How a sunset comet came to be

Mar 18, 2013
Credit: NASA

(Phys.org) —For a comet, visiting the sun is risky business. Fierce solar heat vaporizes gases long frozen in the fragile nucleus, breaking up some comets and completely destroying others.

That's why astronomers weren't sure what would happen in early March when Pan-STARRS, a first-time visitor to the inner solar system, dipped inside the orbit of Mercury. On March 10th, NASA's STEREO-B spacecraft watched as the comet made its closest approach to the sun only 28 million miles away. At that distance, the sun loomed 3 times wider and felt more than 10 times hotter than it does on Earth.

The comet survived.

Still intact, Comet Pan-STARRS is emerging from the Sun's glare into the sunset skies of the . Solar heating has caused the comet to glow brighter than a first magnitude star. Bright twilight sharply reduces visibility, but it is still an easy target for binoculars and small telescopes 1 and 2 hours after sunset. As of March 15th, people are beginning to report that they can see the comet with the unaided eye.

This video is not supported by your browser at this time.
NASA's STEREO-B spacecraft photographed "wild striations" in the tail of Comet Pan-STARRS as it passed by the sun.

Discovered in June 2011 by astronomers using the Pan-STARRS survey telescope atop the Haleakala volcano in Hawaii, the comet is paying its first visit to the . It hails from the Oort cloud, a deep space reservoir of comets far beyond the orbit of Pluto. Because Comet PanSTARRs is a newcomer, its potential brightness and ability to withstand was unknown.

Now we know. "It is a gorgeous comet—one of the brightest in years," says astronomer Matthew Knight of the Lowell Observatory.

Comet specialist Emmanuel Jehin of the has been monitoring Pan-STARRS using a remote-controlled telescope in Chile. Based on his data, Knight concludes that "Comet Pan-STARRS seems to be producing quite a bit of dust compared to an average comet. This is very good for its visibility, because the extra dust is reflecting sunlight and making Pan-STARRS appear brighter than it would otherwise."

The amount of dust and gas spewing from the comet implies a nucleus on the order of 1 km in diameter—in other words, neither unusually large nor small. Size-wise, it is a fairly typical comet.

The comet's tail is anything but typical. STEREO-B images processed by Karl Battams of the Naval Research Lab in Washington DC reveal many wild and ragged striations in the cloud of dust trailing behind Pan-STARRS. "Wow!" says Battams. "The fine-structure is breathtaking. We think this is caused by some fairly complex interaction between the solar wind and the comet's rotating nucleus. It's going to take computer models to figure this one out."

The comet is now receding from Earth. It will slowly dim as it heads back into deep space. Ironically, though, its visibility will improve for a while as it heads into darker skies away from the sun. In the last weeks of March it could become an easy naked-eye object.

Step outside after sunset, face west, and take a look.

Explore further: Computer model shows moon's core surrounded by liquid and it's caused by Earth's gravity

Related Stories

A possible naked-eye comet in March

Feb 09, 2013

Far beyond the orbits of Neptune and Pluto, where the sun is a pinprick of light not much brighter than other stars, a vast swarm of icy bodies circles the solar system. Astronomers call it the "Oort Cloud," ...

Comet posing beside crescent moon in cool photo op

Mar 11, 2013

Now's your chance to see the comet that passed within 100 million miles of Earth last week. Twilight on Tuesday will provide the best photo op for the comet called Pan-STARRS. It will be visible in the Northern ...

Comet Pan-STARRS: How bright will it get?

Sep 06, 2012

Early next year, a comet will come fairly close to Earth and the Sun—traveling within the orbit of Mercury—and it has the potential to be visible to the naked eye. Amateur and professional astronomers ...

Comet Pan-STARRS holds promise for stargazers

Mar 06, 2013

A rare bright comet shows up in the northern hemisphere this week, cruising past Earth with promise of spectacular naked-eye viewings of the giant ball of ice and dust streaking the twilight sky with a blazing ...

Recommended for you

Titan offers clues to atmospheres of hazy planets

8 hours ago

When hazy planets pass across the face of their star, a curious thing happens. Astronomers are not able to see any changes in the range of light coming from the star and planet system.

Having fun with the equation of time

9 hours ago

If you're like us, you might've looked at a globe of the Earth in elementary school long before the days of Google Earth and wondered just what that strange looking figure eight thing on its side was.

The source of the sky's X-ray glow

Jul 27, 2014

In findings that help astrophysicists understand our corner of the galaxy, an international research team has shown that the soft X-ray glow blanketing the sky comes from both inside and outside the solar system.

User comments : 0