Stellar News Briefs

Astronomy Marches On

I’ve been offline the past few days due to a nasty cold (that turned into bronchitis) that I caught while in Florida to catch what turned out to be the “scrub” of the April 29th launch of space shuttle Endeavour. The trip wasn’t a total loss: we got some great images of Endeavour on the pad (see my previous entry about that), and we did our once-every-ten-years-or-so visit to Disney World so we could act like kids again and put on our Mouseketeer hats.

I’m finally up and able to write coherently again, and boy has the news piled on!  So, here’s a look at three of the latest stories with some commentary.

It’s Official: Io is Really, Really Volcanic!

This graphic shows the internal structure of Jupiter's moon Io as revealed by data from NASA's Galileo spacecraft. The low-density crust about 30 to 50 kilometers (20 to 30 miles) thick is shown in gray in the cross-section. Image credit: NASA/JPL/University of Michigan/UCLA

Of course, we’ve all known for years that the little moon Io, which orbits Jupiter, is a volcanic world. But, just HOW volcanic has been confirmed by further analysis of Galileo data. The spacecraft-made measurements show that Io has a subsurface ocean of molten (or partly molten) lava called magma just beneath the surface.  Galileo’s data is the first direct proof that this kind of magma layer exists under the sulfurous rocky crust of this tiny moon.

That subsurface magma sends out about a hundred times MORE lava than all of Earth’s volcanoes combined. Io’s volcanic calderas and vents are scattered across its surface, and their action is enough to completely re-pave this world with lava layers.

The Crab in Motion

The Crab Nebula as seen by Chandra X-ray Observatory. Courtesy NASA/Chandra X-ray Observatory.

One of my favorite supernova remnants is also one of the Chandra X-ray Observatory’s more frequent observing targets.  The folks at Chandra are tracking emissions from the central region of this object, which contains an active pulsar. This week they’ve released a cool little movie that shows changes in the Crab from September 2010 to April 2011.  As you watch the video, you can see some pretty impressive variations in emissions in the structure around the jet at the bottom. You should be able to make out the expansion of a ring of x-ray emission around the pulsar (white dot near center) and changes in the knots within this ring.

However, as the Chandra folks point out on in their release, the arguably the most striking result of these observations is the variations that were not observed, or in analogy with a famous Sherlock Holmes story1, this could be a case where the fact that the dog that did not bark helps to solve a mystery.

The pulsar at the center of the Crab Nebula is a neutron star that spins around about 30 times a second. It was created from a supernova explosion in our galaxy that was observed by astronomers in China and other countries in the year 1054.

As the young pulsar slows down, large amounts of energy are injected into its surroundings. In particular, a high-speed wind of matter and anti-matter particles plows into the surrounding nebula, creating a shock wave that forms the expanding ring seen in the movie. Jets from the poles of the pulsar spew x-ray emitting matter and antimatter particles in a direction perpendicular to the ring. The goal for Chandra’s observations is to pinpoint the location of gamma-ray flares observed by the Fermi spacecraft and Italy’s AGILE satellite. For more information, surf over here.

Star Formation Writ Large in Dwarf Galaxy

Hubble’s newest camera has taken an image of galaxy NGC 4214. This galaxy glows brightly with young stars and gas clouds, and is an ideal laboratory to research star formation and evolution. Courtesy NASA/ESA/STScI.

I’ll close with a gorgeous Hubble Space Telescope look at a star-birth nursery in the dwarf galaxy NGC 4214.  Check this out in “large” mode — it’s beautiful!

This stunner of an image was released earlier today, and is a good look at a starbirth region in a tiny galaxy that, nonetheless, is  packed with everything an astronomer could ask for, from hot, young star-forming regions to old clusters with red supergiants.

What you’re seeing in this image taken in both optical and infrared light by HST’s Wide Field Camera 3, are clouds of glowing ionized hydrogen gas, and in their central regions are cavities blown clear of gas by stellar wind. Nearby are bright star clusters

The huge heart-shaped cavity — possibly the galaxy’s most eye-catching feature — is not just a hole in the clouds. It also contains a large cluster of massive, young stars. They’re hot, too — ranging in temperature from 10,000 to 50 000 degrees Celsius. They blowing out extremely strong stellar winds that are blowing the “bubble” of the cavern free of material. In the process, they’re also closing off any chance for more stars to develop — there’s no more starbirth material left.

Want to know more about this region of space? Check out the full press release and more imagery at