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Sculpting a Galaxy

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in Sculptor

Wow!  Take a look at this beauty of an image from the European Southern Observatory’s VISTA telescope.

ESO VISTA's view of the galaxy NGC 253, which lies about 13 million light-years from Earth. Click to massively galacticate. Courtesy ESO/J. Emerson/VISTA. Acknowledgment: Cambridge Astronomical Survey Unit.

What you’re seeing here is a VISTA view of the galaxy NGC 253, a.k.a. the Sculptor Galaxy, found in the constellation Sculptor (visible in Southern Hemisphere skies).  VISTA looked at this galaxy in infrared light, which gave it a great view of the rich collection of dust clouds that thread through the spiral arms of the galaxy. These dust clouds are where star formation takes place.  In fact, NGC 253 is a starburst galaxy, one that has undergone waves of star formation.  Tracing the dust clouds and bursts of starbirth allows astronomers to understand the formation history of the galaxy and the actions that have shaped it into the barred spiral we see today.

The telescope also was able to see a population of cool, red stars that aren’t very visible (if at all) in optical wavelengths of light (which are the main wavelengths our eyes can see).    This is what infrared viewing allows astronomers to do — that is, to peer through the veils of dust that hide the details of the Sculptor Galaxy. Now they can study in deeper detail the myriad of cool red giant stars in the halo that surrounds the galaxy, and measure the composition of some of NGC 253’s small dwarf satellite galaxies. And, they can search for new objects such as globular clusters and ultra-compact dwarf galaxies that would otherwise be invisible without the deep VISTA infrared images.

I remember some years ago when we first started seeing boasts by ground-based observatories that, using new (at the time) technologies such as adaptive optics, astronomers would be able to achieve “near-Hubble” quality observations of such things as the Sculptor Galaxy.  Images like this, from a ground-based observatory in Chile, show that it can be done.  And, the exciting part is that using observatories like this and the newly improved Hubble Space Telescope, our view of the cosmos is only going to get better!

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Dipping the Sky

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What Else Can You Find?

Ursa Major and the Big Dipper. Use the curved handle of the Dipper to "arc to Arcturus".
Use the curved handle of the Big Dipper to arc to Arcturus.

In another entry, I talked about the Big Dipper and how you can find the North Star with it.  It turns out the Big Dipper is a great pointer to another bright star in the sky. If you take the curve of the handle of the Dipper and follow it out in an arc, you come to the bright star Arcturus, the brightest star in the constellation of Boötes.

A star chart showing Bootes and Arcturus.

Arcturus is an interesting star. It’s slightly orangy-colored K-type star (making it older, cooler, 1.5 times more massive than the Sun and appears larger than the Sun).  I was interested to read over at Jim Kaler’s Stars site that astronomers think that Arcturus comes from an older population of stars in the Milky Way. It’s even possible that Arcturus was part of a smaller, dwarf galaxy that merged with the Milky Way in the distant past.

Arcturus compared to the Sun.

Arcturus is seismically active  — meaning that it goes through physical oscillations,  just as other red giants do. It’s a variable star, meaning that its brightness changes slightly every few days.  Interestingly, when you look at Arcturus, you’re seeing what the Sun could look like as it goes into its red giant phase in a few billion years.

Arcturus is another one of those bright stars that everybody on the planet (well, nearly everybody) seemed to observe throughout history. People used it for navigation and seasonal predictions having to do with harvesting food.  Today, you can simply look up and marvel at this star that lies only about 37 light-years away from us. Just remember to “arc to Arcturus” from the handle of the Big Dipper. It’ll take you on a curvy path across the sky to this slightly reddish, bloated star.  Enjoy!