March 23, 2008

Antlia

Now for another constellation wayyyy down near the Southern horizon in the Spring, right next to Pyxis. Again, though, this is the best (only) time of year it is visible during the evening. This is the constellation Antlia, the air pump (antlia pneumatica, formally). Air pump? Yes, this is one of a set of constellations created by French astronomer Nicolas Louis de Lacaille to fill in blank areas of the sky, all of which are named after scientific instruments. Obviously, there is no mythology associated with it, and there are no exceptional stars here, just a few interesting deep sky objects.

Unfortunately, there are no bright star patterns anywhere near here, so the best direction I can give you is similar to what I gave for Pyxis. Follow the arc of the back of Canis Major from Sirius and through the tail of Wezen and Aludra. About 20 degrees East along the Southern horizon is Pyxis, and then another 25 degrees East of Alpha Pyxidis is Alpha Antliae, a (barely) 4th magnitude star. About 3-4 degrees due south of this star is a pair of galaxies we'll look at first.

NGC 3258 and NGC 3268 are a pair of faint but enormous elliptical galaxies that are at the heart of a nearby cluster of galaxies known as the Antlia cluster, the third nearest cluster to our Local Group behind the Virgo and Fornax clusters, about 32 million light years away (compare to Andromeda's distance of 2 million light years). There are 234 galaxies in this little region of the sky at last count, but only the two giant ellipticals are attainable through small telescopes.

About 2 degrees Southeast of this pair is the spiral galaxy NGC 3347, pictured here in a negative print, a spiral galaxy with rather extended arms with lots of clearly defined star formation regions. Moving about 6 degrees WSW from the Antlia cluster (or 10 degrees Southwest of Alpha Antliae), we have one of the two nicest objects here, the planetary nebula NGC 3132, the Eight-Burst Nebula. This nebula is half a light year in diameter and about 2000 light years away.

The final nice object in this region of the sky is found about 10 degrees WNW of Alpha Antliae, and this is the very nice spiral galaxy NGC 2997. If you follow that link, be sure to click on the deeper image that shows just how far the neutral gas extends beyond the visible border of the galaxy. For a much larger and prettier image of this galaxy, follow this link to see just how far you can trace the ghostly arms into the blackness of the surrounding night.

Posted by Observer at March 23, 2008 09:03 PM
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