Earth Weather / Space Weather

Best Aurora Photos

By: Susie77, 6:40 PM GMT on March 28, 2013

Courtesy of National Geographic

(You can see the rest at the link above. Breathtaking!)


Sunset Comet

By: Susie77, 9:27 PM GMT on March 15, 2013

[I hope you get a chance to look for PanSTARRS -- see previous blog post for a skymap through the end of March. I was lucky enough to spot it on Wednesday evening. I could see it with the unaided eye; it was brighter through binocs. The guys I was with could not see it with unaided eye but did spot it with their binocs.]

Courtesy of Science at NASA

March 15, 2013: 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.

Video: Sunset Comet

That's why astronomers weren't sure what would happen in early March when Comet 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 northern hemisphere. 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.

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 inner solar system. It hails from the Oort cloud, a deep space reservoir of comets far beyond the orbit of Pluto. Because Comet PanSTARRs is a newcomer, astronomers didn't know what to expect.

Now they 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 European Southern Observatory 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.We’re going to need 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.

Production editor: Dr. Tony Phillips | Credit: Science@NASA


Comet PanSTARRS -- Now Visible in Northern Hemisphere

By: Susie77, 9:58 PM GMT on March 07, 2013

Courtesy of Sky and Telescope

Look west after sunset near the horizon. Binoculars may be needed to pick Comet PanSTARRS out of the bright sky. Look too early and the sky will be too bright; too late and the comet will be too low. On the altitude scale at left, 10° is about the width of your fist held at arm's length.

This diagram is drawn for a viewer near 40° north latitude (Denver, New York, Madrid) 30 minutes after sunset. If you're south of there, the comet will be a little higher above your horizon early in the month than shown here. North of 40°, it will be a little lower early in March than shown here.
Sky & Telescope diagram

Swinging toward its March 10th closest approach to Sun, Comet PanSTARRS emerges above the western sunset horizon this week for observers at mid-northern latitudes. Bring binoculars or a wide-field telescope; it's unlikely to be brighter than about 2nd magnitude, not necessarily easy to spot low in twilight through thick air.

The farther south you are, the earlier the date when you may first pick it up. As of February 28th it was already being seen naked eye (faintly) from the Southern Hemisphere. Next week the comet should come into its best visibility for mid-northern latitudes.


About Susie77

Sometimes I complain about the earthly weather, but mostly I like to post about astronomy and space events. Hope you enjoy the articles.

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