Day 92: A tale of three comets

I know; that type is way too small. Click anywhere on the image to go see the big version at the NASA site! Credit: NASA/Swift/Bodewits & Immler and Univ. of Leicester/Bodewits et al.

Wow! Almost at the end of “100 Days of Science.” People keep asking what I’ll do at the end, and I still don’t know. I do know that I’ll take a two-week reprieve, at least from daily posting, while I go visit some family members. I also know that I have a very exciting announcement to make soon, and it entails me being a little too busy for daily posting even after my travels. But I love blogging, and the project has been big fun. 

Any suggestions for a new name for the blog? I didn’t actually plan beyond the end of the “100 Days” when I started …

As for today’s post, a little light reading (and comet ogling) for a Sunday. This is a montage of comets Lulin, Tuttle and SW3, released earlier this month. They’re pictured individually below.

NASA released the images as a trio –  including a new image of Comet 8P/Tuttle — to illustrate just how different three comets can be, as part of a live, 24-hour video webcast called “Around the World in 80 Telescopes,” one of many events celebrating the ongoing International Year of Astronomy.

Comet Lulin -- Credit: NASA/Swift/Univ. of Leicester/Bodewits et al.

Comets are clumps of frozen gases mixed with dust sometimes called “dirty snowballs.” These icy bodies get jostled from their faraway places beyond the solar system’s edge, and forced into a solar orbit, casting off gas and dust whenever they venture near the Sun. 

All three of the images came from NASA’s Swift telescope, dedicated to alert astronomers about new gamma-ray bursts – powerful explosions from distant dying stars. 

Comet 8P/Tuttle passed through the inner solar system in 2008. Credit: NASA/Swift/Bodewits & Immler

From its orbital perch, Swift can view targets using ultraviolet wavelengths, visible light, and X rays — and it’s the only observatory that sees them at the same time. Between bursts, astronomers task Swift to survey the entire sky at X-ray wavelengths, monitor exploding stars, image galaxies, and study comets. 

Comet Lulin provides the best example of cometary X rays Swift has seen so far. The X rays arise through a process called charge exchange, as fast-moving ions emitted by the sun snatch electrons from neutral comet gases. Because this interaction occurs over such a large region, cometary X-ray emission can reach powers as high as a billion watts.

Comet 73P/Schwassman-Wachmann 3; credit NASA/Swift/Bodewits & Immler

Neither SW3 (at left) nor Tuttle could be imaged in X rays with Swift, although NASA’s Chandra X-ray Observatory detected both comets. They each produced much less water than Comet Lulin, which was gushing out nearly 800 gallons of water a second when Swift observed it. 

“Someone calculated that’s equivalent to $17,000 of bottled water each second,” said Geronimo Villanueva, a planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, at a presentation about the discoveries. 

Links/more information:

> NASA’s Swift Spies Comet Lulin
> NASA’s Swift Looks to Comets for a Cool View