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November morning sky at Old Scituate Light in Scituate, MA USA.

Is it true that Jupiter protects Earth?

Brown spots mark the places where fragments of Comet Shoemaker-Levy 9 tore through Jupiter's atmosphere in July 1994.  Image and caption via Wikimedia Commons.

Brown spots mark the places where fragments of Comet Shoemaker-Levy 9 tore through Jupiter’s atmosphere in July 1994.

Here’s a question we get regularly:

Is it true that Jupiter could be considered our friendliest planet because – without Jupiter – comets would be more likely to hit us?

The answer is yes … and no.

Neptune near moon on November 28

2014-nov-28-aquarius-neptune-sigma-aquarii-moon-night-sky-chart

Neptune, the eighth planet out from the sun and outermost of the major planets according to the International Astronomical Union, is the only major planet in our solar system that you absolutely can’t see with the unaided eye. It’s near the moon on the night of November 28, but because of the moonlit glare, you won’t see Neptune very well, even if you have a telescope. What will you see? Only the moon shining in all its splendor. You can gaze at it and imagine Neptune nearby.

Although the moon and Neptune are close together on the sky’s dome tonight, they’re nowhere close in space. The moon resides about 1.2 light-seconds from Earth, whereas Neptune looms way out there at over four light-hours away. In other words, Neptune is over 12,000 times farther away than the moon in tonight’s sky.

Using supermassive black holes to measure cosmic distances

“Eye of Sauron,” an actively growing supermassive black hole at the center of the galaxy called NGC 4151.

How do we know the distances across space? Astronomers start with an actual measurement of nearby stars via stellar parallax and use a stepping stone method to estimate the vast distances beyond the closest stars. It’s impressive, but the method is full of guesstimates, and thus cosmic distances are known to be uncertain. Now researchers from the Niels Bohr Institute at the University of Copenhagen say they’ve demonstrated that precise distances can be measured using supermassive black holes.

Earth has its own Star-Trek-like invisible shield

Scientists have discovered an invisible shield roughly 7,200 miles above Earth that blocks so-called “killer electrons,” which can fry satellites and degrade space systems during intense solar storms. Illustration by Andy Kale, University of Alberta.

Scientists have discovered an invisible shield roughly 7,200 miles (11,600 km) above Earth that blocks so-called “killer electrons,” which can fry satellites and degrade space systems during intense solar storms. Illustration by Andy Kale, University of Alberta.

Today, scientists announced an “extremely sharp” boundary at the inner edge of the outer Van Allen radiation belt. They say this boundary layer is Earth’s own invisible Star-Trek-like shield, in that it appears to block ultrafast electrons from moving deeper into Earth’s atmosphere.

Animation shows Venus in evening sky late 2014 and 2015

Larry Koehn of the wonderful website shadowandsubstance.com dropped us a note today about his newest astronomy animation. It shows the much-anticipated upcoming apparition of the sky’s brightest planet – Venus – in the evening sky in late 2014 and 2015.

Dolphins use specific whistles as names

Image credit: Shutterstock / Willyam Bradberry

Image credit: Shutterstock / Willyam Bradberry

Bottlenose dolphins in Africa use signature whistles to identify each other, similar to the way humans use names, say scientists.

Small Magellanic Cloud is a nearby dwarf galaxy

View larger. |  A Perseid meteor streaks between the two Magellanic Clouds during the peak of the 2013 Perseid meteor shower.  Photo by Colin Legg.

A Perseid meteor streaks between the two Magellanic Clouds. Photo by Colin Legg.

You’ll see the Small Magellanic Cloud from Earth’s Southern Hemisphere. It’s even farther to the south than its larger cousin, the the Large Magellanic Cloud . These two hazy patches in the southern sky are really separate galaxies from our Milky Way. They are satellite galaxies to the Milky Way, orbiting around it. Follow the links inside to learn more about the Small Magellanic Cloud.

Mira the Wonderful

Mira, from NASA's Galaxy Evolution Explorer

Mira, as seen by NASA’s Galaxy Evolution Explorer. Mira’s comet-like tail, discovered in 2007, stretches 13 light-years in space.

The star Omicron Ceti – aka Mira – in the constellation Cetus varies in brightness like clockwork over 11 months. That’s why, for centuries, stargazers have called it Mira the Wonderful.

Does eating turkey really make you sleepy?

Photo credit: Lotus Carroll/Flickr

Photo credit: Lotus Carroll/Flickr

Ah, Thanksgiving Day. You pile your plates with turkey, dressing, two kinds of potatoes, cranberries – all the traditional foods – and dig in. Second helpings? Of course! An hour later, after plenty of food and conversation, you push back and notice you’ve become very, very sleepy. You think, “I’m sleepy because turkey is high in tryptophan.”