Astronomers spy a 2nd interstellar visitor

Animated diagram of solar system with line coming in from above and sweeping out below.
This illustration depicts the trajectory of the object now known as C/2019 Q4. Deemed a possible interstellar object, it will approach no closer to Earth than about 190 million miles (300 million km). Image via NASA/JPL-Caltech.

Astronomers are buzzing this week about a newly discovered object that appears to have come from interstellar space. The official confirmation that this object – labeled C/2019 Q4 – is interstellar has not yet been made, but if it is, it would be only the second such object detected. How exciting is that? First, there was only one known object – which earthly astronomers named ‘Oumuamua – observed and confirmed as interstellar, in October 2017. And now there are two. The second (“likely”) interstellar object has been designated C/2019 Q4 (Borisov). Gennady Borisov of Ukraine – an optician by trade – discovered it August 30, 2019, at the MARGO observatory in Nauchny, Crimea.

A statement from NASA called the object a “comet” and said:

The new comet, C/2019 Q4, is still inbound toward the sun, but it will remain farther than the orbit of Mars and will approach no closer to Earth than about 190 million miles (300 million km).

After the initial detections of the comet, Scout system, which is located at NASA’s Jet Propulsion Laboratory in Pasadena, California, automatically flagged the object as possibly being interstellar. Davide Farnocchia of NASA’s Center for Near-Earth Object Studies at JPL worked with astronomers and the European Space Agency’s Near-Earth Object Coordination Center in Frascati, Italy, to obtain additional observations. He then worked with the NASA-sponsored Minor Planet Center in Cambridge, Massachusetts, to estimate the comet’s precise trajectory and determine whether it originated within our solar system or came from elsewhere in the galaxy.

Farnocchia said:

The comet’s current velocity is high, about 93,000 mph [150,000 kph], which is well above the typical velocities of objects orbiting the sun at that distance. The high velocity indicates not only that the object likely originated from outside our solar system, but also that it will leave and head back to interstellar space.

Do we know what C/2019 Q4 looks like? No. It’s mainly just a moving speck to us, albeit, apparently, a slightly fuzzy one. Its orbit resembles the orbits of long-period comets. NASA called it a comet in its announcement, but, in another announcement from the European Space Agency, astronomers used the more neutral word “object.” The NASA statement explained the results of observations completed by Karen Meech and her team at the University of Hawaii, indicating the comet nucleus is somewhere between 1.2 and 10 miles (2 and 16 km) in diameter:

2019 Q4 was established as being cometary due to its fuzzy appearance, which indicates that the object has a central icy body that is producing a surrounding cloud of dust and particles as it approaches the sun and heats up.

“Established” is a strong word, and our guess is that not every astronomer will agree with it. And of course science fiction fans, like me, are hoping it’s something more exciting than a comet, even a (likely) interstellar one.

Could the object be something other than a comet? With ‘Oumuamua, some astronomers speculated that the object might be an alien artifact, perhaps similar to the two Voyager spacecraft that are now hurtling outward away from our solar system, with their golden records attached. Astronomers hunted for signals from ‘Oumuamua, but they didn’t find any. ‘Oumuamua went on its way with many mysteries still unsolved, just as this object will reach its closest point to our sun – its perihelion – on December 8, 2019, at a distance of about 190 million miles (300 million km). Then, if it is truly interstellar, it will – like ‘Oumuamua – flee again into the space between the stars.

White fuzzy dots on black background.
This illustration depicts Comet C/2019 Q4’s appearance against background stars. Deemed a possible interstellar object, it will approach no closer to Earth than about 190 million miles (300 million km). Image via NASA/JPL-Caltech.

According to NASA, C/2019 Q4 will be within reach of professional telescopes for months to come. Farnocchia said:

The object will peak in brightness in mid-December and continue to be observable with moderate-size telescopes until April 2020. After that, it will only be observable with larger professional telescopes through October 2020.

NASA said that astronomers will continue collect observations to further characterize the comet’s physical properties (size, rotation, etc.) and also continue to better identify its trajectory.

Diagram of solar system with long, curved yellow line passing through it.
Hyperbolic orbit of comet C/2019 Q4. By definition, this sort of orbit means an object will only travel through the solar system only once. If this is the correct orbit for this object, it may indeed be interstellar. Image via ESA.Image via ESA.

So a second-ever known interstellar object has (probably) entered our solar system, and we will likely hear more about it in the months to come as astronomers continue to scrutinize it.

By the way [SPOILER ALERT AHEAD], if you never read Rendezvous with Rama – a 1973 sci fi book by Arthur C. Clarke about an object that enters our solar system from interstellar space, and turns out to be an alien spacecraft – then you might not appreciate the words:

And on far-off Earth, Dr. Carlisle Perera had as yet told no one how he had wakened from a restless sleep with the message from his subconscious still echoing in his brain: The Ramans do everything in threes.

If you did read it … you know why I (longingly) mention that quote!

Bottom line: Astronomers believe they discovered a second interstellar object on August 30, 2019. They labeled it C/2019 Q4. If it’s confirmed as interstellar, it would be only the second such object detected, after ‘Oumuamua, observed in 2017.

Read more from NASA/JPL

Read more from ESA

September 12, 2019

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