Space | EarthSky https://earthsky.org Updates on your cosmos and world Wed, 10 Apr 2024 21:52:13 +0000 en-US hourly 1 https://wordpress.org/?v=6.4.4 Rainbow-like glory on an exoplanet is 1st-ever detected https://earthsky.org/space/glory-on-an-exoplanet-wasp-76b-exoplanets-glories/ https://earthsky.org/space/glory-on-an-exoplanet-wasp-76b-exoplanets-glories/#respond Thu, 11 Apr 2024 12:00:19 +0000 https://earthsky.org/?p=471096 For the 1st time, astronomers say they have detected a glory on an exoplanet. Glories are a natural phenomenon, but until now seen only on Earth and Venus.

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Glory on an exoplanet: Reddish planet with circular concentric rainbow-like feature on right side, with stars in background.
View larger. | Artist’s concept of the rainbow-like glory on giant exoplanet WASP-76b. If confirmed, it will be the 1st glory on an exoplanet that astronomers have ever seen. Glories are common on Earth, but otherwise have only been seen on Venus so far. Image via ESA (ESA Standard License or CC BY-SA 3.0 IGO).
  • Astronomers have detected what appears to be a glory – the same optical phenomenon you sometimes see out the window of an airplane – on on exoplanet, or planet orbiting a distant star.
  • Glories are common on Earth, and spacecraft have seen them on Venus. But, if confirmed, this will be the first time astronomers have seen a glory outside of our solar system.
  • Glories are a natural circular rainbow-like phenomenon that only occur in certain atmospheric conditions.

Have you ever seen a glory? Glories are colorful, concentric rings of light that form only under certain conditions. You can often see them while looking out an airplane window. They’re fairly common to see on Earth. And astronomers have also seen glories on Venus. But on April 5, 2024, scientists said they’ve detected the first-ever glory outside our solar system, on an exoplanet – or planet orbiting another star – some 637 light-years away. The exoplanet is called WASP-76b, and it’s an ultra-hot gas giant.

They said they spotted the glory using data from two different space observatories: ESA’s CHaracterising ExOPlanet Satellite (Cheops) and NASA’s Transiting Exoplanet Survey Satellite (TESS).

The researchers published their peer-reviewed findings in the journal Astronomy & Astrophysics on April 5, 2024.

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1st glory on an exoplanet?

If this is really a glory – still to be fully confirmed – it will be the first one ever seen outside of our solar system. Olivier Demangeon is an astronomer at the Institute of Astrophysics and Space Sciences in Portugal, and lead author of the new study. He said:

There’s a reason no glory has been seen before outside our solar system; it requires very peculiar conditions. First, you need atmospheric particles that are close-to-perfectly spherical, completely uniform and stable enough to be observed over a long time. The planet’s nearby star needs to shine directly at it, with the observer – here Cheops – at just the right orientation.

The glory appears to be located between the day side and night side of the planet. Similar to glories seen here, it likely occurs when sunlight is reflected off clouds made of a uniform substance. What that substance is on WASP-76b, however, is still unknown.

Hints of the glory phenomenon

So, how did the astronomers detect the glory? The first hints came from observation of the planet as it transited – passed in front of – its star as seen from Earth. The limbs of the planet – the outermost edges – looked “wonky.” The researchers made 23 observations of WASP-76b over three years. During that time, they noticed something unusual. They saw more than the expected amount of light coming from the planet’s eastern terminator, where the day side meets the night side. What might explain the change in brightness?

The researchers said that a glory can explain the odd observations. Demangeon said:

This is the first time that such a sharp change has been detected in the brightness of an exoplanet, its “phase curve.” This discovery leads us to hypothesise that this unexpected glow could be caused by a strong, localised and anisotropic (directionally dependent) reflection … the glory effect.

Reddish and bluish colors inside an 8-sided octagon shape.
View larger. | Venus is the only other place in the solar system where astronomers or spacecraft have seen glories besides Earth. The Venus Express spacecraft captured this enhanced color view on July 24, 2011. The image is composed of 3 images in ultraviolet, visible and near-infrared wavelengths from the Venus Monitoring Camera. Image via ESA/ MPS/ DLR/ IDA (ESA Standard License).

A hellish world

WASP-76b is a gas giant planet, like Jupiter and Saturn, 637 light-years from Earth. It is, in fact, almost twice the twice the size of Jupiter. But about 10% less massive, however. In our solar system, the giant planets all orbit far away from the sun. But WASP-76b is what astronomers call a hot Jupiter. It orbits its sun-like star 12 times closer than Mercury orbits our sun. No wonder it’s so hot!

It is tidally locked to its star, so one side is always in daylight while the other is in darkness. It is so hot, up to 2,400 degrees Celsius (4,300 degrees F) on the dayside, that scientists say it probably rains molten iron. Rocks on the day side would melt. They then evaporate and condense back on the night side. This could create clouds composed of iron particles that would then drip molten iron rain.

Co-author Matthew Standing at ESA said:

What’s important to keep in mind is the incredible scale of what we’re witnessing.

WASP-76b is several hundred light-years away, an intensely hot gas giant planet where it likely rains molten iron. Despite the chaos, it looks like we’ve detected the potential signs of a glory. It’s an incredibly faint signal.

2 sets of concentric colored rings divided vertically.
View larger. | This is a simulated comparison of a glory on Venus (left) and Earth (right). Why do they look different? Cloud droplets on Earth are typically between 10 and 40 thousandths of a millimeter in diameter, but on Venus the droplets at the cloud tops are no more than 2 thousandths of a millimeter across. Therefore, the colored fringes are further apart than they would appear on Earth. Image via C. Wilson/ P. Laven/ ESA (ESA Standard License).

The science of a glory on an exoplanet

Why is finding a glory on an exoplanet significant? First, it’s already a relatively rare phenomenon in our own solar system overall. So finding glories on exoplanets shows that they can happen elsewhere, too. It also provides clues about WASP-76s’s atmosphere. It means there must be clouds made of perfectly spherical droplets. The observations so far show that they either can last more than three years or the clouds are being constantly replenished. That in turn requires temperatures to be stable over long periods of time.

In addition, being able to detect glories will help astronomers see other faint phenomena including glints of sunlight on oceans or lakes on exoplanets.

There is also just the intrigue and satisfaction of finding something new and unique. Demangeon explained:

I was involved in the first detection of asymmetrical light coming from this weird planet, and ever since I have been so curious about the cause. It has taken some time to get here, with moments where I asked myself, “Why are you insisting on this? It might be better to do something else with your time.” But when this feature appeared out of the data, it was such a special feeling, a particular satisfaction that doesn’t happen every day.

Top image shows an airplane glory on water; bottom image shows a close-up of the glory.
View at EarthSky Community Photos. | Eliot Herman caught this wonderful airplane glory on June 29, 2022, while flying over Bristol Bay, Alaska. Thank you, Eliot! The glory on an exoplanet likely appears similar to this, but much larger.

More observations needed to confirm

Additional observations are needed to know for sure that this is a glory, as Theresa Lüftinger, Project Scientist for ESA’s upcoming Ariel mission, which will study the chemical makeup of exoplanets, noted:

Further proof is needed to say conclusively that this intriguing ‘extra light’ is a rare glory. Follow-up observations from the NIRSPEC instrument onboard the NASA/ESA/CSA James Webb Space Telescope could do just the job. Or ESA’s upcoming Ariel mission could prove its presence. We could even find more gloriously revealing colors shining from other exoplanets.

Bottom line: For the 1st time, astronomers say they have detected a glory on an exoplanet. Glories are a natural phenomenon, but until now seen only on Earth and Venus.

Source: Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 b

Via ESA

Read more: Perfect airplane glory

Read more: Space rainbow: Glory seen in Venus atmosphere

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New Horizons finds evidence for 2nd Kuiper Belt https://earthsky.org/space/new-horizons-pluto-spacecraft-2nd-kuiper-belt/ https://earthsky.org/space/new-horizons-pluto-spacecraft-2nd-kuiper-belt/#respond Wed, 10 Apr 2024 12:04:21 +0000 https://earthsky.org/?p=471351 The Pluto spacecraft New Horizons is still alive and speeding outward. Has it found a 2nd Kuiper Belt? The team is hopeful for new spacecraft targets.

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New Horizons: Disk with many white dots. There are 4 circles with different colors at the center of the disk. Five lines come out of an orange sphere at the inner top of the disk.
Only 5 earthly spacecraft are headed out of solar system, into interstellar space. These are the Pioneers 10 and 11, Voaygers 1 and 2, and New Horizons. This image shows their approximate trajectories. Image (not to scale!) via NASA/ Johns Hopkins APL/ SwRI.
  • The New Horizons spacecraft, launched in 2006, achieved historic flybys of Pluto in 2015 and Arrokoth in 2019, making it the fastest spacecraft ever sent from Earth.
  • Chief scientist Alan Stern here provides an update, highlighting unexpected discoveries of dust impacts, an extended Kuiper Belt or even a second one, and outlines plans for future exploration.
  • Its long-term mission goals include reaching the heliosphere’s termination shock and venturing into interstellar space, using its modern instrumentation to complement the findings of NASA’s Voyager spacecraft.

New Horizons visited Pluto in 2015

Remember how exciting it was when the New Horizons spacecraft encountered Pluto? This craft – the fastest one ever sent outward from Earth – launched on January 19, 2006, passed the moon’s orbit in just 9 hours, and then spent 10 years crossing the 3-billion-mile distance to Pluto. It swept past Pluto in 2015, passing within about 7,750 miles (12,500 km) of the little world and discovering, among many other things, a large, young, heart-shaped region of ice on Pluto plus mountains made of water ice. In 2019, New Horizons swept past Arrokoth, which thereby became the farthest and most primitive object in our solar system ever to be visited by a spacecraft. On April 4, 2024, New Horizons chief scientist Alan Stern provided an update of the mission’s findings, as it continues to move outward. He said New Horizons has found evidence for a 2nd Kuiper Belt.He also said the New Horizons team is still hopeful that groundbased searches will reveal new Kuiper Belt Objects that the spacecraft might be able to explore. He reported:

The spacecraft continues to collect round-the-clock data on our sun’s cocoon in the galaxy, called the heliosphere, and transmit that data, as well as the final data from our flyby of Kuiper Belt object Arrokoth, back to Earth … The first of those was the publication of exciting new results from our onboard dust counter instrument, which you can find online. It shows that over the past few years, the instrument detected an unexpectedly high number of dust impacts.

Why is that so exciting? Because it indicates more dust at greater distances from the sun than expected, which in turn could be evidence of an extended Kuiper Belt, or even a second Kuiper Belt, lying ahead.

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Illustration showing Kuiper Belt.
The inner edge of the Kuiper Belt begins at the orbit of Neptune, at about 30 astronomical units (AU) from the sun (1 AU = 1 Earth-sun distance). The outer edge continues outward to nearly 1,000 AU, with some bodies on orbits that go even further beyond. The Kuiper Belt is much like the asteroid belt between Mars and Jupiter, but much more massive. Besides Pluto, it contains bits of rock and ice, comets and larger objects such as Eris, Makemake and Haumea. Image via Space Center Houston.

More Kuiper Belt Objects ahead?

So New Horizons is finding more dust than it expected in the far outer reaches of our solar system. And Alan Stern explained that there are other possibilities for the high dust-impact rate in this part of the solar system.

But, he said, the New Horizons team is also using groundbased telescopes to search along the spacecraft’s outbound trajectory for additional Kuiper Belt Objects. If any lie near the spacecraft’s path, perhaps it will be possible to study them. And he said those searches have led to:

… a surprising number of very distant KBOs ahead of us. That leads to a similar conclusion that the Kuiper Belt could be more extended, or even that there could be a 2nd Kuiper Belt, still farther ahead. These new groundbased results have been submitted for scientific peer review but aren’t yet published. However, a summary of them is posted here and here.

Together, these results have ignited renewed interest in the possibility of finding a distant KBO that New Horizons could fly past in the late 2020s or even 2030s. Toward that end, our team has proposed a multiyear KBO flyby target search to NASA.

If approved by NASA, that effort would initially continue the deep, groundbased KBO searches with the Japanese Subaru Telescope we’ve been using, but with more search time and a deeper search enabled by a new, high-throughput filter that the New Horizons project provided to Subaru.

Beginning in 2025 …

Then, beginning in 2025, we plan to propose to use the even more capable Vera Rubin Observatory (VRO), which is jointly funded by the National Science Foundation and the U.S. Department of Energy, for this search. VRO is a new observatory scheduled to come online in late 2024, and can search even more deeply than Subaru can.

Later, once NASA’s Roman Space Telescope is launched in 2027 or 2028, we would propose to employ this still even more capable observatory, also with custom machine-learning software and supercomputers to crunch those data.

Our calculations indicate that, given the evidence for an extended Kuiper Belt and very distant KBOs, that this triad of searches might just find New Horizons a second flyby KBO. But the calculations also show that even such a search is a longshot, looking for proverbial needles in the cosmic haystack, and might come up dry.

Two brown rocks connected. The one on the left is bigger.
In 2019 New Horizons made the first spacecraft reconnaissance of any Kuiper Belt object (KBO), exploring this small and ancient world called Arrokoth, just 21 miles (33 km) long. Image via NASA/ Johns Hopkins APL/ SwRI.

Nonetheless, he said …

We know that the odds of finding a new flyby target are much more remote without this newly envisioned set of searches. We also know that the scientific payoff of another KBO close flyby for planetary science in general are immense. And the New Horizons team is eager to search. We are willing to try everything humanly possible to get to another KBO flyby. If we do succeed, we’ll have hit the jackpot, and will have the ability to once again be firing our engines to intercept a KBO for close up study, just as we did to achieve the 2019 flyby of KBO Arrokoth — the first KBO ever examined by any spacecraft!

Also just ahead for New Horizons is our continuing studies of the Sun’s outer heliosphere, observing KBOs we pass in the distance, and making other scientific measurements that only a spacecraft in the distant Kuiper Belt can make.

New Horizons is in excellent health, and has sufficient fuel and power to continue to explore into the 2040s, at least. By the late 2020s or 2030s, the spacecraft should fly through the heliosphere’s so-called termination shock, which is the precursor to the heliopause and our entry into interstellar space! NASA’s venerable Voyager spacecraft have already studied the termination shock, the heliopause and interstellar space, but New Horizons has more modern sensors aboard, to greatly supplement what the Voyagers could do.

How can New Horizons keep exploring?

Stern concluded:

To make all this possible, as our spacecraft’s nuclear battery produces less and less power each year, we plan to uplink new software. That software package is called autonomy and fault protection, and the team is already designing and coding it. After extensive testing, we expect to transmit it to New Horizons using NASA’s Deep Space Network of communications antennas. You can learn more about the Deep Space Network.
I’m excited about all of these plans for New Horizons. I’m also excited for us to continue to making scientific discoveries in data we’ve already acquired and the data we’ll collect in 2024. Nearly two-dozen scientific papers with such results, ranging from Kuiper Belt and KBO studies, to heliospheric science, and more, were published in 2023, and a similar number is planned for this year.

Ways to follow New Horizons news and commentary

NASA’s New Horizons website

New Horizons mission website

NASA New Horizons on X

New Horizons on Facebook

New Horizons eNews signup

Sun in the middle with a few little dots, 5 circles and fuzzy green and then gray halo around.
This depiction of the Sun’s heliosphere includes the termination shock that New Horizons will cross in the years ahead, the first of several heliospheric boundaries as our spacecraft approaches interstellar space. Image via NASA/I BEX/ Adler Planetarium/ Johns Hopkins APL.

Bottom line: News from the Pluto spacecraft New Horizons. It is still alive and still speeding outward. It has recently found evidence for a 2nd Kuiper Belt. The team is hopeful new spacecraft targets will be found.

Via Alan Stern, New Horizons

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The threat of supernovas to life on Earth https://earthsky.org/space/threat-of-supernovas-to-life-on-earth/ https://earthsky.org/space/threat-of-supernovas-to-life-on-earth/#respond Fri, 05 Apr 2024 10:19:15 +0000 https://earthsky.org/?p=470733 The threat of supernovas to life on Earth is due to their intense radiation. Fortunately, they'd have to be fairly close to affect Earth.

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Threat of supernovas: An hourglass shaped bright area of gas and dust.
Massive dying stars explode in supernovas and emit large amounts of radiation. The radiation would be deadly to nearby planets with life. So what is the threat of supernovas to life on Earth? Image via NASA/ ESA/ Hubble SM4 ERO Team.

By Chris Impey, University of Arizona

The threat of supernovas to life on Earth

Stars like the sun are remarkably constant. They vary in brightness by only 0.1% over years and decades, thanks to the fusion of hydrogen into helium that powers them. This process will keep the sun shining steadily for about 5 billion more years, but when stars exhaust their nuclear fuel, their deaths can lead to pyrotechnics.

The sun will eventually die by growing large and then condensing into a type of star called a white dwarf. But stars more than eight times more massive than the sun die violently in an explosion called a supernova.

Supernovas happen across the Milky Way only a few times a century. And these violent explosions are usually remote enough that people here on Earth don’t notice. For a dying star to have any effect on life on our planet, it would have to go supernova within 100 light-years from Earth.

I’m an astronomer who studies cosmology and black holes.

In my writing about cosmic endings, I’ve described the threat posed by stellar cataclysms such as supernovas and related phenomena such as gamma-ray bursts. Most of these cataclysms are remote. But when they occur closer to home they can pose a threat to life on Earth.

The death of a massive star

Very few stars are massive enough to die in a supernova. But when one does, it briefly rivals the brightness of billions of stars. At one supernova per 50 years, and with 100 billion galaxies in the universe, somewhere in the universe a supernova explodes every hundredth of a second.

The dying star emits high energy radiation as gamma rays. Gamma rays are a form of electromagnetic radiation with wavelengths much shorter than light waves. Therefore, they’re invisible to the human eye. The dying star also releases a torrent of high-energy particles in the form of cosmic rays: subatomic particles moving at close to the speed of light.

An animation showing a supernova.

Supernovas nearby

Supernovas in the Milky Way are rare, but a few have been close enough to Earth that historical records discuss them. In 185 CE (the common era), a star appeared in a place where no star had previously been seen. It was probably a supernova.

Observers around the world saw a bright star suddenly appear in 1006 CE. Astronomers later matched it to a supernova 7,200 light-years away. Then, in 1054 CE, Chinese astronomers recorded a star visible in the daytime sky that astronomers subsequently identified as a supernova 6,500 light-years away.

Read more: Meet the Crab Nebula, remnant of an exploding star

Johannes Kepler observed last supernova in the Milky Way in 1604, so in a statistical sense, the next one is overdue.

At 600 light-years away, the red supergiant Betelgeuse in the constellation of Orion is the nearest massive star getting close to the end of its life. When it goes supernova, it will shine as bright as the full moon for those watching from Earth, without causing any damage to life on our planet.

A man with dark hair and a beard, wearing dark clothes with an elaborate collar, resting one hand on his hip and another on a globe.
Johannes Kepler, the astronomer who observed what was likely a supernova in 1604. Image via Wikimedia Commons/ Kepler-Museum in Weil der Stadt.

Radiation damage

If a star goes supernova close enough to Earth, the gamma-ray radiation could damage some of the planetary protection that allows life to thrive on Earth. There’s a time delay due to the finite speed of light. If a supernova goes off 100 light-years away, it takes 100 years for us to see it.

Astronomers have found evidence of a supernova 300 light-years away that exploded 2.5 million years ago. Radioactive atoms trapped in seafloor sediments are the telltale signs of this event. Radiation from gamma rays eroded the ozone layer, which protects life on Earth from the sun’s harmful radiation. This event would have cooled the climate, leading to the extinction of some ancient species.

Safety from a supernova comes with greater distance. Gamma rays and cosmic rays spread out in all directions once emitted from a supernova, so the fraction that reach the Earth decreases with greater distance. For example, imagine two identical supernovas, with one 10 times closer to Earth than the other. Earth would receive radiation that’s about a hundred times stronger from the closer event.

A supernova within 30 light-years would be catastrophic. It would severely deplete the ozone layer, disrupt the marine food chain and likely cause mass extinction. Some astronomers guess that nearby supernovas triggered a series of mass extinctions 360 to 375 million years ago. Luckily, these events happen within 30 light-years only every few hundred million years.

When neutron stars collide

But supernovas aren’t the only events that emit gamma rays. Neutron star collisions cause high-energy phenomena ranging from gamma rays to gravitational waves.

Left behind after a supernova explosion, neutron stars are city-size balls of matter with the density of an atomic nucleus, so 300 trillion times denser than the sun. These collisions created many of the gold and precious metals on Earth. The intense pressure caused by two ultradense objects colliding forces neutrons into atomic nuclei, which creates heavier elements such as gold and platinum.

Neutron stars merge when gravity pulls them together, which releases intense radiation.

A neutron star collision generates an intense burst of gamma rays. These gamma rays are concentrated into a narrow jet of radiation that packs a big punch.

Gamma rays aimed at Earth

If the Earth were in the line of fire of a gamma-ray burst within 10,000 light years, or 10% of the diameter of the galaxy, the burst would severely damage the ozone layer. It would also damage the DNA inside organisms’ cells, at a level that would kill many simple life forms like bacteria.

That sounds ominous, but neutron stars do not typically form in pairs, so there is only one collision in the Milky Way about every 10,000 years. They are 100 times rarer than supernova explosions. Across the entire universe, there is a neutron star collision every few minutes.

Gamma-ray bursts may not hold an imminent threat to life on Earth, but over very long time scales, bursts will inevitably hit the Earth. The odds of a gamma-ray burst triggering a mass extinction are 50% in the past 500 million years and 90% in the 4 billion years since there has been life on Earth.

By that math, it’s quite likely that a gamma-ray burst caused one of the five mass extinctions in the past 500 million years. Astronomers have argued that a gamma-ray burst caused the first mass extinction 440 million years ago, when 60% of all marine creatures disappeared.

A recent reminder

The most extreme astrophysical events have a long reach. Astronomers were reminded of this in October 2022, when a pulse of radiation swept through the solar system and overloaded all of the gamma-ray telescopes in space.

It was the brightest gamma-ray burst to occur since human civilization began. The radiation caused a sudden disturbance to the Earth’s ionosphere, even though the source was an explosion nearly 2 billion light-years away. Life on Earth was unaffected, but the fact that it altered the ionosphere is sobering. A similar burst in the Milky Way would be a million times brighter.The Conversation

Chris Impey, University Distinguished Professor of Astronomy, University of Arizona

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Bottom line: The threat of supernovas to life on Earth is due to their intense radiation. Fortunately, they’d have to be fairly close to affect Earth. Colliding neutron stars and their resulting gamma-ray burst also pose a threat to Earth. Sometime in Earth’s past 4 billion years of history, it’s likely that a gamma-ray burst caused a mass extinction on Earth.

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Is Titan’s subsurface ocean habitable? https://earthsky.org/space/titans-subsurface-ocean-habitability-organics/ https://earthsky.org/space/titans-subsurface-ocean-habitability-organics/#respond Fri, 05 Apr 2024 10:18:37 +0000 https://earthsky.org/?p=465870 Saturn's largest moon Titan has an underground ocean of water. But is Titan's subsurface ocean habitable? A new study casts doubt.

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Titan's subsurface ocean: Planet-like body half in shadow with lakes of liquid near its North Pole.
View larger. | Titan is well-known for its lakes and seas of liquid methane and ethane. This image from Cassini in 2017 shows light glinting off the lakes. But Titan is also thought to have an ocean of liquid water deep underground. Is Titan’s subsurface ocean habitable? Image via NASA/ JPL-Caltech/ University of Arizona/ University of Idaho.

Saturn’s large moon Titan teems with liquid. We’ve long known about its liquid methane and ethane lakes and seas. More recent evidence suggests a subsurface ocean of liquid water. Could Titan’s underground ocean be habitable? Earlier this year, a new study suggested it likely isn’t. The study said there probably isn’t enough organic material transferring from Titan’s surface to the ocean below to sustain life.

Astrobiologist Catherine Neish and her colleagues at Western University in Ontario, Canada published their peer-reviewed findings in the journal Astrobiology on February 2, 2024.

What does habitability mean to astronomers?

Is Titan’s subsurface ocean habitable?

NASA’s Cassini spacecraft found evidence that Titan has a deep ocean beneath its outer icy crust. This is similar to other moons such as Europa, Enceladus, Ganymede and others. But is it habitable, by earthly standards? Even with water, life still requires a source of heat, organic material and chemical nutrients. And all life on Earth uses water as a solvent to develop in. Neish said:

Life as we know it here on Earth needs water as a solvent, so planets and moons with lots of water are of interest when looking for extraterrestrial life.

Cometary impacts

We don’t yet know the exact conditions in Titan’s subsurface ocean. In the new study, however, Neish and her colleagues wanted to test how much organic material can make it from Titan’s surface down into the ocean. Organics, of course, including amino acids, are essential building blocks of life on Earth. The researchers used impact cratering data to determine how much organic material might be in Titan’s ocean. Those organics originated from the impacts on the surface.

Titan is blanketed in organics, with its hydrocarbon dunes, lakes and seas. Even its atmosphere is filled with a thick hydrocarbon. But does any of that organic material makes it down into the ocean? Impacts from comets – which can also have their own organics – can temporarily melt the icy surface. The meltwater could then sink through the ice.

The researchers estimated how many comets have impacted Titan throughout its history. Knowing this, the team could then estimate how much water has flowed from the surface down through the ice, possibly all the way to the ocean.

Not enough organics for life in Titan’s subsurface ocean

As it turned out, the results suggest that there wouldn’t be enough organics getting into the ocean to make life feasible. There would only be about 16,000 pounds (7,500 kg) per year of glycine, the simplest amino acid. That’s about the same mass as a single African male elephant. Amino acids are essential as they are the building blocks of proteins. Neish said:

One elephant per year of glycine into an ocean 12 times the volume of Earth’s oceans is not sufficient to sustain life. In the past, people often assumed that water equals life, but they neglected the fact that life needs other elements, in particular, carbon.

This work shows that it is very hard to transfer the carbon on Titan’s surface to its subsurface ocean. Basically, it’s hard to have both the water and carbon needed for life in the same place.

The paper stated:

Unless biologically available compounds can be sourced from Titan’s interior, or be delivered from the surface by other mechanisms, our calculations suggest that even the most organic-rich ocean world in the solar system may not be able to support a large biosphere.

Still much to learn about Titan’s subsurface ocean

It would be disappointing if the ocean isn’t well-suited for life. But Titan is still a fascinating world, with plenty of prebiotic chemistry occurring on its surface and in its atmosphere. As Neish noted:

Even if the subsurface ocean isn’t habitable, we can learn a lot about prebiotic chemistry on Titan, and Earth, by studying the reactions on Titan’s surface. We’d really like to know if interesting reactions are occurring there, especially where the organic molecules mix with liquid water generated in impacts.

NASA’s upcoming Dragonfly mission to Titan will be able to sample in spots where meltwater from impacts has mixed with the ice. Dragonfly is currently scheduled to launch in 2026 and arrive in 2034. Neish continued:

If all the melt produced by impacts sinks into the ice crust, we wouldn’t have samples near the surface where water and organics have mixed. These are regions where Dragonfly could search for the products of those prebiotic reactions, teaching us about how life may arise on different planets. The results from this study are even more pessimistic than I realized with regards to the habitability of Titan’s surface ocean, but it also means that more interesting prebiotic environments exist near Titan’s surface, where we can sample them with the instruments on Dragonfly.

Moon-like sphere with cutaway view showing various layers inside it, and planet with edge-on rings in background.
View larger. | Titan has a global subsurface ocean of water, represented here by the dark blue layer. Image via NASA.

Pessimism about other ocean moons

The study puts forth a pessimistic view of life on the other ocean moons in the solar system as well. As Neish explained:

Unfortunately, we will now need to be a little less optimistic when searching for extraterrestrial lifeforms within our own solar system. The scientific community has been very excited about finding life in the icy worlds of the outer solar system, and this finding suggests that it may be less likely than we previously assumed.

The study argues that other ocean moons such as Europa and Enceladus have less organics and carbon on their surfaces to begin with. Therefore, they might have even less organics in their oceans.

Other moon’s oceans may still be habitable

However, other studies have pointed to those two oceans, Enceladus in particular, as being promisingly habitable. In the case of Enceladus, the Cassini spacecraft detected a variety of organic molecules in the water vapor plumes, which originate from the ocean below. There is also evidence for hydrothermal vents on the ocean floor, which would provide heat and nutrients. Enceladus’ ocean even contains phosphorus, another key building block of life.

Last September, researchers said that carbon dioxide ice deposits on Europa’s surface likely originated from its internal ocean. So at least in one way, the scenario is opposite that of Titan. The organic carbon rises to the surface through cracks, instead of sinking down through the ice. This shows that organics can indeed be present in such underground oceans, without having to get there from the surface. The organics in Enceladus’ plumes also suggest this.

Bottom line: Saturn’s largest moon Titan has an underground ocean of water. But is Titan’s subsurface ocean habitable? A new study casts doubt.

Source: Organic Input to Titan’s Subsurface Ocean Through Impact Cratering

Via Western University

Read more: Titan’s magic islands appear and disappear in liquid seas

Read more: Did Europa’s carbon dioxide come from its ocean?

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Giant planets orbiting white dwarfs: 1st images? https://earthsky.org/space/planets-orbiting-white-dwarfs-exoplanets-webb-space-telescope/ https://earthsky.org/space/planets-orbiting-white-dwarfs-exoplanets-webb-space-telescope/#respond Thu, 04 Apr 2024 10:43:21 +0000 https://earthsky.org/?p=464611 Astronomers using NASA's Webb telescope have discovered and imaged two possible giant planets orbiting white dwarfs less than 75 light-years away.

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Giant planets orbiting white dwarfs: 6 squares with black fuzzy dots in 5 of them, blue star shapes in 4 and black text labels.
These Webb images depict WD 1202-232 (top row) and WD 2105-82 (bottom row). In the 2 images at far left, the white dwarf is at the center. In the other 4 images, the white dwarf has been replaced by a star icon. The images on the far right are with the planetary candidate removed. This technique shows that in both cases the candidate planet came out cleanly, indicating it’s a real “point-source in nature.” The images are evidence for 2 giant planets orbiting white dwarfs, both less than 75 light-years away. Image via Mullally et al./ arXiv.

Can a planet survive the death of its star? A new study says yes, it can. Scientists at the Space Telescope Science Institute (STScI) said in a new paper on January 24, 2023, that they have discovered two possible giant exoplanets orbiting white dwarfs, which are the remains of ordinary stars that have lost their ability to shine in the way most stars do. Both of these white dwarfs lie within 75 light-years of Earth. NASA’s James Webb Space Telescope first detected the planets in 2023. Astronomers have discovered planets orbiting white dwarf stars before, but, if confirmed, these will be the first planets around white dwarfs for which we have direct images.

Jonathan O’Callaghan wrote about the discovery for Science on January 31, 2024.

The researchers’ new peer-reviewed paper has been accepted for publication in The Astrophysical Journal Letters and is available on the arXiv preprint server.

Webb images 2 possible giant planets orbiting white dwarfs

Susan Mullally, an astronomer at the Space Telescope Science Institute, led the new observations. She and her colleagues used Webb to study four nearby white dwarfs, all of which are within 75 light-years of Earth. Two of those white dwarfs proved to be of particular interest, WD 1202-232 and WD 2105-82. Each of those white dwarfs appears to have a giant planet still orbiting it. In both cases, the planetary candidates orbit far out from their white dwarf stars, like the gas and ice giants in our solar system. Both white dwarfs are polluted with metals (heavy elements) in their atmospheres.

One of the planets is estimated to be 1.3 times as massive as Jupiter. Its orbit is similar to Saturn’s in our solar system. The other planet has a larger orbit, slightly farther from its white dwarf than Neptune is from our sun. That planet is also more massive, about 2.5 times that of Jupiter.

The discovery of these two giant worlds, if confirmed, shows that larger gas giant planets can indeed survive their stars becoming white dwarfs. Mullally said:

This is our first real indication that planets like Jupiter and Saturn should survive the evolution of their sun into a white dwarf.

The white dwarf planets are real … probably

Right now, the two planets are still considered to be candidates. They are not fully confirmed … yet. There is still a chance, albeit a small one, that they are false positives. They could actually be background galaxies, but the researchers said the chances of that are only about one in 3,000. To confirm the objects as real planets, the researchers need to make sure they are gravitationally bound to the stars. As Jay Farihi at University College London told Science:

You need to be sure they move together in space.

Only then can the researchers fully rule out background galaxies.

In addition, if the astronomers do confirm the planets, that would support the possibility that such planets could often survive their stars becoming white dwarfs. The research team was studying only four white dwarfs with Webb at the time. And two of those have planetary candidates. Mary Anne Limbach at the University of Michigan said:

Two out of their four systems have candidates, which is incredible. We’re going to be able to build up a sample of planets that look exactly analogous to Saturn and Jupiter in our system.

Planet with banded clouds in its atmosphere with bright white star in distance.
View larger. | This is an artist’s concept of a gas giant planet orbiting a white dwarf star. Image via NASA/ JPL-Caltech.

Other planets orbiting white dwarfs

Although these are the first exoplanet candidates to be directly imaged around white dwarfs, they are not the first detections.

In 2021, astronomers at the W. M. Keck Observatory in Hawaii said they found evidence of a gas giant planet orbiting a white dwarf 6,500 light-years away. The planet has a similar size and orbit to Jupiter in our solar system.

Astronomers reported another giant exoplanet around a white dwarf 1,500 light-years from Earth in 2019, too. This planet, however, seemed to be evaporating. That’s because it orbits very close to the white dwarf, completing an orbit in only 10 days.

Also, in 2021, astronomers found evidence of four white dwarfs consuming Earth-like planets. According to analysis of the vaporized material found, these are the remains of the outer layers, the crusts, of planets similar in rocky composition to Earth and Mars that used to orbit those stars.

1st habitable zone planet around a white dwarf

And in 2022, scientists said that there is likely a small rocky planet orbiting in the habitable zone of its white dwarf, 117 light-years away. Even though they are producing much less heat, white dwarfs can still have their own habitable zones, just like regular stars. It is in those zones that temperatures are suitable for a rocky planet to possibly have liquid water.

So it seems that planets around white dwarfs might be rather common. How do they compare to planets that orbit still-active stars? It will be interesting to see what telescopes like Webb and other reveal about them.

Bottom line: Astronomers using NASA’s Webb space telescope have discovered and imaged two possible giant planets orbiting white dwarfs. Both are less than 75 light-years away.

Source: JWST Directly Images Giant Planet Candidates Around Two Metal-Polluted White Dwarf Stars

Via Science

Read more: Solar system’s future seen: 1st planet around a white dwarf

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Black hole is ‘underachiever,” despite jets and high radiation https://earthsky.org/space/black-hole-quasar-h1821643-chandra-vlt/ https://earthsky.org/space/black-hole-quasar-h1821643-chandra-vlt/#respond Mon, 01 Apr 2024 12:00:20 +0000 https://earthsky.org/?p=470439 A black hole in a quasar 3.4 billion light-years away is powerful but underachieving, according to astronomers using NASA's Chandra X-ray Observatory.

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Black hole: Bright white round spot with bluish and reddish blurry shapes around it on black background.
View larger. | This is H1821+643, a quasar containing a supermassive black hole, captured in a composite image (X-rays and radio waves). The quasar and its black hole are relatively nearby, only 3.4 billion light-years from Earth. The black hole is emitting powerful jets and high levels of radiation. But astronomers expected … more. X-ray image: NASA/ CXC/ U. of Nottingham/ H. Russell et al.; Radio: NSF/ NRAO/ VLA; Image Processing: NASA/ CXC/ SAO/ N. Wolk/ Chandra.
  • Quasars and their embedded supermassive black holes are exceedingly bright. We often see them at very large distances, corresponding to a time in the early history of our universe.
  • Quasar H1821+643 is the closest known quasar to Earth within a galaxy cluster. It’s about 3.4 billion light-years away. So we’re seeing it at a time not so long ago.
  • This quasar’s supermassive black hole appears to be underachieving, despite having some attributes like the quasars in the early universe, such as powerful jets and high levels of radiation. It’s underachieving in the sense that it isn’t affecting its surroundings as much as astronomers expected it would.

The supermassive black hole in the center of our Milky Way galaxy is about 4 million times our sun’s mass. But the black hole embedded in quasar H1821+643 – 3.4 billion light-years away – is some 4 billion times our sun’s mass. As the closest quasar known within a galaxy cluster, H1821+643 was the focus of a new study performed in both X-rays and radio. Astronomers collaborated, using the Earth-orbiting Chandra X-ray Observatory and the Very Large Telescope, or VLT, in Chile. And, on March 21, 2024, upon releasing the results of their study, they called the black hole in H1821+643 an underachiever.

They said that, although this giant black hole is responsible for high levels of radiation and powerful jets, it’s not affecting its surroundings as greatly as many of its black hole counterparts in other galaxies.

The international team of researchers published their peer-reviewed findings in the Monthly Notices of the Royal Astronomical Society on January 27, 2024.

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Closest quasar to Earth in a galaxy cluster

Quasars are extremely bright, up to 1,000 times brighter than our home galaxy, the Milky Way. The intense radiation from quasars is thought to be due to the supermassive black holes found at the hearts of most galaxies. Quasars in the early universe tend to be exceedingly “hungry.” They are pulling in material from their surroundings, creating conditions for high levels of radiation and powerful, superluminal jets.

But some supermassive black holes are pulling in surrounding material more slowly than others. They outburst energy on a regular basis, preventing the superheated gas that surrounds them from cooling down. This has two effects. One is the limiting of star formation in the host galaxy. The other is a limit on how much material the black hole consumes.

Underachieving black hole

But when it comes to supermassive black holes in quasars that are in galaxy clusters, like H1821+643, there is still a lot for astronomers to learn. And this black hole appears to be underperforming. As lead author Helen Russell of the University of Nottingham in the U.K. noted:

We have found that the quasar in our study appears to have relinquished much of the control imposed by more slowly growing black holes. The black hole’s appetite is not matched by its influence.

Overall, the new study suggests that quasars may have less influence on their host galaxy, and even the galaxy cluster, than previously thought.

Observing with Chandra

So, how did the researchers determine this? With Chandra, they looked at the hot gas that surround the black hole, quasar and host galaxy. The hot gas emits weak X-rays, while the X-rays from the quasar and black hole are much stronger. Strong enough that they obscured the astronomers’ observations of the gas X-rays. So the researchers had to remove the stronger X-rays from the composite images. In doing so, the researchers could measure how much influence the X-rays from the black hole and quasar had on its surroundings.

As it turned out, not that much. The density of hot gas was higher in the vicinity of the black hole and quasar, but the temperatures lower than expected. Why? The researchers said it’s because there are less outbursts of energy from the black hole than they thought there would be. Usually, those bursts would help prevent the gas from cooling down. But instead, the gas is cooling down and flowing toward the center of the galaxy cluster.

Most supermassive black holes have a much larger influence on their neighborhood. So this particular black hole is underperforming, you could say. As the paper described it,

The active galactic nucleus appears to be underheating the core of this cluster.

The paper also noted that the black hole may be undersized, or it may be going through a period of underheating. Additional observations may help to determine which is the case.

Bottom line: A black hole in a quasar 3.4 billion light-years away is powerful but underachieving, according to astronomers using NASA’s Chandra X-ray Observatory.

Source: A cooling flow around the low-redshift quasar H1821+643

Via Chandra X-ray Observatory

Read more: What are black holes?

Read more: Closest black holes yet in famous Hyades star cluster?

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Comet Hale-Bopp closest to the sun 27 years ago today https://earthsky.org/space/this-date-in-science-comet-hale-bopp/ https://earthsky.org/space/this-date-in-science-comet-hale-bopp/#comments Mon, 01 Apr 2024 10:38:14 +0000 https://earthsky.org/?p=238057 27 years ago on April 1, 1997, Comet Hale-Bopp was at perihelion, its closest point to the sun. This comet was widely seen from the Northern Hemisphere.

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A bright round-wedge-shaped comet with multiple flared tails.
Comet Hale-Bopp with its prominent dust (white) and plasma (blue) tails. Photo via E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory/ Wikimedia Commons (CC BY-SA 3.0).
  • Discovered by amateur astronomers: Comet Hale-Bopp was discovered on July 23, 1995, independently by Alan Hale and Thomas Bopp, two amateur astronomers.
  • Many people saw it!: Comet Hale-Bopp became one of the brightest comets seen from Earth in the 20th century. It reached peak brightness in April 1997 when it was visible to the naked eye for a record-breaking 18 months.
  • Huge cometary nucleus: Comet Hale-Bopp’s nucleus, or icy core, was estimated to be about 25 miles (40 kilometers) in diameter, making it one of the largest cometary nuclei ever observed.

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Remember Comet Hale-Bopp?

Twenty-seven years ago today – on April 1, 1997 – Comet Hale-Bopp reached its perihelion or closest point to the sun. It was slightly less than Earth’s distance from the sun at 0.9 astronomical units (Earth-sun units). And it was bright, for a comet. Its brightness – though dispersed across a wider area than stars – exceeded that of any star in the sky except for Sirius, the sky’s brightest star.

Hale-Bopp is officially labeled C/1995 O1. It was one of the most-viewed comets in human history.

As seen from the Northern Hemisphere, Hale-Bopp was the brightest comet since Comet West, sometimes called the Great Comet of 1976. Hale-Bopp stayed visible with the unaided eye for a record of 18 months, twice as long as the previous record holder: the Great Comet of 1811. Some called Hale-Bopp the Great Comet of 1997 (although others disagreed that it met the criteria for a Great Comet).

One of the most-viewed comets ever

There are over 5,000 images of this comet available via a webpage maintained by NASA’s Jet Propulsion Laboratory.

It attracted so many people not only because of its rarity and beauty, but also because it enabled people to jump – in their minds – back in time. Some 4,200 years ago, when Hale-Bopp last passed the Earth and sun, the Egyptian pyramids were newly being polished by sand, and the Epic of Gilgamesh, considered the first great work of Western literature, was not yet written.

Bright light (saturated moon) and a comet over a desert landscape with 3 pyramids in distance.
Comet Hale-Bopp above the pyramids of Giza, Egypt, in 1997, accompanied by the saturated moon and stars of Taurus with the Pleiades and Perseus. Image via John Goldsmith/ ESA.

Comet Hale-Bopp discovery

Comet Hale-Bopp was discovered on July 23, 1995, by two independently observing amateur astronomers: Alan Hale and Thomas Bopp. At that time, the comet was a whopping 7.2 AU from the sun, which made it the most distant comet to ever be discovered by amateurs up until that time.

What made that discovery possible was that Hale-Bopp was so bright. It was literally a thousand times brighter than Comet Halley had been at that same distance; Halley, one of the most famous comets, had visited the inner solar system a decade earlier. It was clear that Hale-Bopp was a very special comet, because comets typically don’t shine so brightly when they are beyond Jupiter’s orbit.

There were a few reasons explaining the comet’s unusual brightness. The main one is the enormous size of its nucleus, or core. Most cometary nuclei are thought to be no more than about 10 miles (16 km) across. The nucleus of Hale-Bopp had a diameter estimated to be between 25 and 40 miles across (40-60 km).

Sky gradient from yellow via purple to dark, with a tree in the foreground and a bright comet on the sky.
Comet Hale-Bopp from near Pazin, Croatia, seen near perihelion. The Andromeda Galaxy is faintly visible to the lower right of the comet. Image via Philipp Salzgeber/ Wikimedia Commons (CC BY-SA 2.0 at).

The orbit of Comet Hale-Bopp

Giant Jupiter is thought to have affected this comet’s orbit. It’s been calculated that Hale-Bopp was last seen in Earth’s skies around 4,200 years ago. Now, though, the comet’s orbit is shorter. Astronomers think that – on what might have been its first voyage around the sun thousands of years ago – the comet almost collided with Jupiter. It passed very close to Jupiter again in April 1996, shortening its orbital period still more. The comet’s current orbital period is around 2,530 Earth years.

No records have been found of the comet’s passage 4,200 years ago, but that does not mean that no records were made. It most likely means that none survived. Around 2213 B.C., when the comet last was visible, civilizations had been using the sky to track seasonal changes and other phenomena for a long time. They could not have missed Hale-Bopp.

For more about the world at Hale-Bopp passage around 2213 B.C., click here.

Thus, in a way, Hale-Bopp is like a clock that measures time in millennia. It reminds us of the progress humankind has made since its last visit. Imagine what the world will look like when Comet Hale-Bopp next crosses our skies, sometime around the year 4380.

Where is the comet now?

Comet Hale-Bopp is in the constellation Octans with an estimated magnitude of +19.95. The comet is over 4,485,532,00 miles (7,218,765,000 km) distant from the sun. Check the current location at theskylive.com.

Bottom line: Twenty-seven years ago on April 1, 1997, Comet Hale-Bopp was at perihelion, its closest point to the sun. This comet – remembered by many – was widely seen from the Northern Hemisphere.

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The moon: 5 myths about our natural satellite https://earthsky.org/space/five-myths-about-the-moon/ https://earthsky.org/space/five-myths-about-the-moon/#comments Sun, 31 Mar 2024 11:01:19 +0000 https://earthsky.org/?p=176373 There are plenty of myths that surround the moon. Here are 5 of the most popular myths. How many of these myths have you been led to believe?

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Animation showing moon crossing full Earth with moon far side facing camera.
View larger. | Here’s a unique view of the moon as it moved in front of the sunlit side of Earth in 2015. The Deep Space Climate Observatory (DSCOVR) satellite captured it from about a million miles (1.6 million kilometers) out. This image shows what many call the “dark side” of the moon. But it’s not dark at all. In this image, it’s fully illuminated. Read about the myth that the moon has a dark side, and about more moon myths, below. Image via NASA/ NOAA.

We have full moons, blue moons, Harvest Moons, supermoons and any number of culturally relevant references to the moon. Maybe it’s time to unearth a few moon myths and misconceptions. Have you believed any of these myths?

Myth 1: The moon has a permanent dark side

Most grammar school students know that the moon presents only one face or side to the Earth. This is (roughly) true and gives rise to the idea that there is a permanent dark side of the moon, a thought immortalized in Pink Floyd’s music and elsewhere.

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But the side of the moon that is perpetually turned away from Earth is not darker than the side we see. It is fully illuminated by the sun just as often (lunar daytime), and is in shade just as often (lunar night), as is the familiar Man in the Moon side we see.

The Earth-facing side of the moon gives rise to another misconception that many people share, namely that we see only 50% of the moon from Earth. In fact, only about 41% of the moon’s far side (a much more accurate and preferable term than dark side) is invisible to earthly observers. A diligent observer on Earth can, over time, observe about 59% of the moon’s surface. This is because a phenomenon called libration causes the moon’s viewing angle, relative to Earth, to change slightly over its orbit. Basically, this causes our view of the the moon to shift slightly up-and-down and from side-to-side.

Lunar libration is when we can see a bit further over one limb (edge) or the other. The moon occasionally exposes slightly more of its surface on the eastern or western extreme (depending on the location in the orbit). That’s why, as viewed from Earth, about 59% of the moon’s surface is exposed over the course of the moon’s (roughly) monthly orbit around the Earth.

On black background, beam of light hitting a prism and coming out the other side as a spectrum of colors.
Pink Floyd’s Dark Side of the Moon album cover from 1973. Image via Wikimedia Commons (fair use).

Myth 2: The moon is perfectly round

To the eye, the moon appears round. So it’s natural to assume that it is actually spherical in shape – with every point on its surface equidistant from its center – like a big ball. Not so. The shape of the moon is that of an oblate spheroid, meaning it has the shape of a ball that is slightly flattened.

Look at a photo of Jupiter and you will see a good example of this. The moon exhibits very slight oblateness, but more important is the fact that the “side” of the moon that faces Earth is a bit larger than the side turned away from us. This makes it slightly similar to the shape of a typical bird egg that is larger on one “end” than on other. You might think of it as “gumdrop” shaped. So the moon is not exactly spherical. The deviation is small but real.

Full moon with clear view of dark splotches (maria) and craters.
Near side of the moon as seen through a telescope. The moon looks round, but it isn’t. In a dark sky, the moon looks bright white, but this image captures its true asphalt-gray color. Notice that the moon’s near side has dark “maria” or “seas,” while the moon’s far side lacks these features. Image via Wikimedia Commons (CC BY-SA 3.0).

Myth 3: The moon is bright white

Anyone who has seen a full moon high in a clear sky late at night has a right to believe this. Comparatively speaking, however, the moon is neither particularly bright nor actually white. It appears very bright relative to the dark sky, and ordinarily looks white to the eye. Remember the old-style incandescent light bulbs? Now imagine a 100-watt light bulb located about 150 feet (46 meters) away and shining in an otherwise completely dark night. That is approximately how bright the full moon is. Really.

And the color? Well, as with brightness, color is a subjective thing. The moon emits no light of its own, but rather shines by reflecting sunlight. Sunlight is composed of all colors, but peaks in the yellow-green range of the spectrum. The sun looks white when high in the sky, as does the moon, because of the way our eye-brain connection mixes all the colors together. The moon’s color varies somewhat according to its phase and position in the sky, although this color variation generally is too subtle for human eyes. However, the moon is actually gray rather than pure white, on average much like the well-worn asphalt on most streets.

A half-lit moon on a black sky. There are many small craters and big dark areas on the lit right side.
View at EarthSky Community Photos. | Lorraine Boyd in Glen Falls, New York, captured November’s 1st quarter moon on November 20, 2023. Lorraine wrote: “There’s just something about seeing the moon in the 1st quarter phase that puts a smile on my face.” Thank you, Lorraine! Us, too.

Myth 4: There is no gravity on the moon

But of course the moon does have gravity. The idea that the moon has no gravity is, frankly, so ludicrous that I would not even mention it were it not so prevalent. When shown an image of one of the Apollo astronauts jumping high or seemingly floating across the lunar surface, some of my college students will reply that it is because there is no gravity on the moon. In reality, the force of gravity on the moon is only about 1/6 what it is on Earth, but it is still there.

I think that this moon myth, widespread though it may be, is simply a misunderstanding of what the word gravity means in physics. Every physical body, whether it be the sun, Earth, the moon, a human body or a subatomic particle – everything that has substance – has a gravitational pull.

While the practicality of measuring the weight (the pull of gravity) on tiny objects, such as a grain of sand, can be debated, the force exists and can be calculated. Even photons of light and other forms of energy exhibit gravity. Gravity holds galaxy clusters, galaxies, stars, planets and moons together and/or in orbit about each other. If every physical thing did not exhibit gravity, the universe as we know it could not exist.

Myth 5: The moon raises significant tides in people

There is no question that the moon, or rather its gravity, is the major cause of ocean tides on Earth. The sun’s gravity raises tides, too, by the way, but its effect is smaller. Some folks use the indisputable fact of the moon’s effect on the tides to argue that the moon raises tides in the human body. However, to believe that ocean tides and human tides both are caused by the moon betrays a major misunderstanding about how gravity works to produce ocean tides.

In short, gravity depends on two things: mass and distance. Tides occur only when the two objects involved (say, Earth and the moon) are both of astronomical size (far larger than a human!), and also close (astronomically) in distance. The moon is roughly 30 Earth diameters away from our planet, and roughly 1/80th of the Earth’s mass. Given that, the moon helps raise tides, which on average, are a couple of meters (a few feet) high in the fluid oceans.

If tidal effects were even measurable in the human body, which they aren’t, they would be on the order of a ten-millionth of a meter, or about one-thousandth the thickness of a piece of paper. Those are still tides, you say? Perhaps. But they are far, far smaller tides than are raised within your body when a truck passes you on the highway … or even when another person walks past you on the street.

So while the moon’s gravity can power the tides on Earth, its effect on a human body is utterly inconsequential.

By the way, we often hear people say that nurses in hospitals report an increase in birth rate at times of the month when the moon is full. But studies don’t bear out this correlation. There’s a concise summary of moon/ birth rate studies at Wikipedia. Be sure to click into the references to see that they were published in bona fide science journals, such as the New England Journal of Medicine, American Journal of Obstetrics and Gynecology, and so on.

Of course, the moon does influence us in some ways

The moon can certainly pull on our heartstrings when we see a beautiful crescent bathed in earthshine, or an orange-hued lunar eclipse. But it may have some physical effects on us as well.

Women’s menstrual cycles appear to correlate with the cycle of the moon’s monthly orbit around Earth. If it is a true correlation, and not a coincidence, it’s not yet fully explained.

Another recent study showed that people sleep less leading up to a full moon. Maybe you’ve noticed yourself tossing and turning as the moon nears full phase? Read more: People sleep less before a full moon.

Man standing on a car with hands out to huge glowing full moon.
View at EarthSky Community Photos. | Stojan Stojanovski in Bitola, Macedonia, captured this image on August 30, 2023. Stojan wrote: “My friend shows you the super Blue Moon tonight on the top of the mountain.” Thank you, Stojan!

Bottom line: There are plenty of myths that surround the moon. Here are five of the most popular myths. How many of these myths have you been led to believe?

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Older brown dwarfs are more likely to be lonely https://earthsky.org/space/brown-dwarfs-binary-systems-hubble-space-telescope/ https://earthsky.org/space/brown-dwarfs-binary-systems-hubble-space-telescope/#respond Sun, 31 Mar 2024 10:04:43 +0000 https://earthsky.org/?p=470192 NASA's Hubble Space Telescope has found older and less massive brown dwarfs tend to be alone with no companions, unlike younger and larger brown dwarfs.

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Brown dwarfs: Bright slightly glowing sphere with dark bands in its atmosphere and stars in background.
View larger. | Artist’s concept of a brown dwarf. It’s an object that’s too massive enough to be an ordinary planet, but not massive enough to shine as a star. Many brown dwarfs come in binary pairs, where two orbit one another. But a new study shows the less massive and older a brown dwarf is, the more likely it is to be alone. Image via NASA/ ESA, Joseph Olmsted (STScI)/ Hubblesite.
  • Brown dwarfs are star-planet hybrid objects, with a mass in between that of stars and planets.
  • The older and less massive a brown dwarf is, the less likely it is to have a companion brown dwarf.
  • Over time, it appears the brown dwarf companions just drift apart.

Older brown dwarfs are more likely to be lonely

Most stars come in pairs, or binary systems. Brown dwarfs – objects more massive than Jupiter but less massive than the smallest stars – can come in binary pairs, too. But a new study with the Hubble Space Telescope has found older brown dwarfs are less likely to have companions. On March 21, 2024, an international team of scientists said the older and less massive a brown dwarf is, the more likely it is to wander through space alone. It appears that many binary brown dwarfs drift apart over timescales of millions of years.

The researchers first published their peer-reviewed paper in the Monthly Notices of the Royal Astronomical Society on September 22, 2023.

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Older and lower-mass brown dwarfs unlikely to have companions

Hubble found that it’s rare for a lower-mass, cooler brown dwarf to have a binary companion. The researchers studied a sampling of 33 older and cooler brown dwarfs in our local galactic neighborhood. The team used two different near-infrared filters on Hubble, one in which a cold brown dwarf will appear bright, and another covering specific wavelengths where it will look very faint due to water absorption in its atmosphere.

NASA’s Wide-Field Infrared Survey Explorer (WISE) had previously found these brown dwarfs. Most of them are only a few hundred degrees warmer than Jupiter. None of them had binary companions, even though Hubble can detect binary companions as close as 300 million miles (480 million km) to each other. That’s about the same distance from the sun to the asteroid belt in our solar system.

Astronomers have previously found that younger brown dwarfs often do have companions, however. Lead author Clémence Fontanive of the Trottier Institute for Research on Exoplanets at the University of Montréal, Canada, said:

Our survey confirms that widely separated companions are extremely rare among the lowest-mass and coldest isolated brown dwarfs, even though binary brown dwarfs are observed at younger ages. This suggests that such systems do not survive over time.

What does this mean? It suggests younger brown dwarfs generally aren’t massive enough to have sufficient gravity to keep the pair together. Instead, they gradually drift apart over hundreds of millions of years.

Born the same way as stars

The findings not only provide new information about brown dwarf binaries but how a brown dwarf itself forms and evolves. And the results support previous theories that brown dwarfs form the same way stars do. This involves both of them forming from the gravitational collapse of a cloud of molecular hydrogen. But then why do brown dwarfs end up so different from stars?

Essentially, brown dwarfs are not massive enough for the nuclear fusion of hydrogen to occur.

Gleaming metallic cylinder floating in space above Earth.
View larger. | Astronomers used the Hubble Space Telescope to find out more about binary brown dwarfs. Image via NASA.

Similarities to binary stars

More than half the stars in our galaxy have a binary companion. And, similar to brown dwarfs, it’s more massive stars that are typically in those binary systems. That prompted the researchers to compare them to brown dwarf binaries and look for similar trends, as Fontanive noted:

The motivation for the study was really to see how low in mass the trends seen among multiple stars systems hold up.

Our Hubble survey offers direct evidence that these binaries that we observe when they’re young are unlikely to survive to old ages; they’re likely going to get disrupted. When they’re young, they’re part of a molecular cloud, and then as they age the cloud disperses. As that happens, things start moving around and stars pass by each other. Because brown dwarfs are so light, the gravitational hold tying wide binary pairs is very weak, and bypassing stars can easily tear these binaries apart.

The new data from Hubble is the best ever obtained so far regarding brown dwarf pairs. Fontanive said:

This is the best observational evidence to date that brown dwarf pairs drift apart over time. We could not have done this kind of survey and confirmed earlier models without Hubble’s sharp vision and sensitivity.

Bottom line: NASA’s Hubble Space Telescope has found that older and less massive brown dwarfs tend to be alone with no companions, unlike brown dwarfs that are younger and larger.

Source: An HST survey of 33 T8 to Y1 brown dwarfs: NIR photometry and multiplicity of the coldest isolated objects

Via Hubblesite

Read more: What are brown dwarfs?

Read more: 95 new cool brown dwarfs in the sun’s neighborhood

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5000th comet for sun-observing SOHO spacecraft https://earthsky.org/space/5000th-comet-discovery-soho/ https://earthsky.org/space/5000th-comet-discovery-soho/#respond Fri, 29 Mar 2024 10:27:27 +0000 https://earthsky.org/?p=470202 Citizen scientists using imagery from the SOHO solar observatory have now discovered their 5000th comet. You can help, too! Join the Sungrazer Project.

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5000th comet: An orangish background with a faint, lighter color blur circled, moving across the scene.
The circled object is the 5,000th sungrazing comet discovered by the sun-observing SOHO spacecraft. This 5000th comet is moving relative to background stars; that’s how we know the circled object is closer to us than the stars. SOHO’s LASCO instrument acquired the images to create this animation. The images are via NASA/ ESA/ SOHO. By the way, experts believe this comet is related to Comet 96P/Machholz, named for Don Machholz, a beloved member of the EarthSky team until his death in 2022. Don discovered a total of 12 comets that bear his name. We miss you, Don!
  • NASA’s sun-observing SOHO spacecraft has now made its 5,000th comet discovery. As of March 29, 2024, it has been 28 years, 3 months, and 27 days since SOHO launched in December, 1995!
  • These comets are sungrazers. Sungrazing comets are those that pass extremely close to the sun at their closest point (perihelion), sometimes within a few thousand kilometers of the sun’s surface. Some are vaporized, but some survive to pass near the sun again and again.
  • SOHO’s comets were found with the help of citizen scientists as part of the Sungrazer Project.

Vanessa Thomas originally wrote this story, which NASA published on March 27, 2024. Edits by EarthSky.

SOHO discovers its 5000th comet

On March 25, 2024, a citizen scientist in the Czech Republic spotted a comet in an image from the Solar and Heliospheric Observatory (SOHO) spacecraft. It’s now confirmed as the 5,000th comet discovered using SOHO data. SOHO has achieved this milestone over 28 years in space, even though it was never designed to be a comet hunter.

The newest comet is a small body of ice and rock that orbits the sun every few years. It belongs to the “Marsden group” of comets. Experts believe this group is related to Comet 96P/Machholz. That comet is named for Don Machholz, who was a beloved member of the EarthSky team until his passing in 2022. Don discovered 12 comets that bear his name. SOHO observes Comet 96P/Machholz every 5.3 years when it passes near the sun.

The Marsden group is named for the late scientist Brian Marsden, who first recognized the group using SOHO observations. Only about 75 of the 5,000 comets discovered with SOHO belong to the Marsden group.

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The most prolific comet-finder in history

A joint mission of ESA and NASA, SOHO launched in December 1995 to study the sun and the dynamics in its outer atmosphere, or the corona. A science instrument on SOHO – the Large Angle and Spectrometric Coronagraph (LASCO) – uses an artificial disk to block the blinding light of the sun. This masking allows scientists to study the corona and environment immediately around the sun.

It also allows SOHO to do something many other spacecraft cannot: see comets flying close to the sun, known as “sungrazing” comets or “sungrazers.” Many of these comets only brighten when they’re too close to the sun for other observatories to see. Therefore, they would otherwise go undetected, lost in the bright glare of our star.

While scientists expected SOHO to serendipitously find some comets during its mission, the spacecraft’s ability to spot them has made it the most prolific comet-finder in history. SOHO has discovered more than half of the comets known today.

Dark circle at center blocking disk of sun with light stream from it and tiny dot nearby, with inset.
The 5,000th comet discovered with the Solar and Heliospheric Observatory (SOHO) spacecraft is in the white box at upper left. A zoomed-in inset shows the comet as a faint dot between the white vertical lines. SOHO’s Large Angle and Spectrometric Coronagraph (LASCO), which uses a disk to block the bright sun and reveal faint features around it, took this image on March 25, 2024. Image via NASA/ ESA/ SOHO.

Sungrazer Project

Soon after SOHO launched, people around the world began spotting so many comets in its images that mission scientists needed a way to keep track of them all. In the early 2000s, they launched the NASA-funded Sungrazer Project, which allows anyone to report comets they find in SOHO images.

SOHO’s 5,000th comet was found by Hanjie Tan, a Sungrazer Project participant who is originally from Guangzhou, China. He’s currently pursuing a doctoral degree in astronomy in Prague, Czech Republic. Tan has been participating in the Sungrazer Project since he was 13 years old and is one of the project’s youngest comet discoverers. Tan said:

Since 2009, I’ve discovered over 200 comets. I got into the Sungrazer Project because I love looking for comets. It’s really exciting to be the first to see comets get bright near the sun after they’ve been traveling through space for thousands of years.

Most of the 5,000 comets discovered using SOHO have been found with the help of an international cadre of volunteer comet hunters in the Sungrazer Project. And many of them have no formal scientific training.

5000th comet wows scientists

Karl Battams is a space scientist at the U.S. Naval Research Lab in Washington, D.C., and the principal investigator for the Sungrazer Project. He said:

Prior to the launch of the SOHO mission and the Sungrazer Project, there were only a couple dozen sungrazing comets on record: That’s all we knew existed. The fact that we’ve finally reached this milestone – 5,000 comets – is just unbelievable to me.

The vast number of comets discovered using SOHO has allowed scientists to learn more about sungrazing comets and groups of comets that orbit the sun. Comets discovered by the Sungrazer Project have also helped scientists learn more about the sun, by watching the comets plunge through our star’s atmosphere like small solar probes. Battams said:

The statistics of 5,000 comets, and looking at their orbits and trajectories through space, is a super unique dataset. It’s really valuable science. It’s a testament to the countless hours the project participants have put into this. We absolutely would never had reached this milestone if it wasn’t for what the project volunteers have done.

Bottom line: Citizen scientists using imagery from the SOHO solar observatory have now discovered their 5000th comet. You can help, too! Join the Sungrazer Project.

Via NASA

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