Astro Bob A look at celestial happenings in the Northland and beyond Bob King View my profile Click here to view previous posts or additional resources

Poked by a needle

I looked but didn't see any northern lights last night so perhaps tonight they'll materialize. Space weather forecasters predict that auroras may be visible from the northern tier of states both tonight and tomorrow night. I'll be watching and hope you will,too. Look low in the north for a telltale greenish arc between 9 p.m. and midnight. That'll be the tip-off a display is underway. If you see anything shaking out there , please drop us an e-mail or post a comment below. Also, don't forget to watch for the crescent moon and Venus pairing up again in the west tonight about 45 minutes after sundown. The moon will lie about a fist directly above the planet.

A rough sketch of the galaxy NGC 4565 as viewed in a 15-inch reflector at 142 power last night. The long "wings" are the galaxy's thin disk. The central oval is the hub or bulge where stars are more concentrated. The white dot is the star-packed core of the galaxy while the dark swath above it is a band of silhouetted stardust.

Taking very long time exposures the Hubble Space Telescope has found up to 3000 galaxies in just 2.5 arc minutes of sky -- that's less than one-tenth the diameter the full moon subtends in the sky. If we multiply that amount by 24 we get the number of galaxies in one degree of sky which is the amount of sky covered by your little "pinkie" held at arm's length. Are you ready for this? It comes to 72,000 galaxies! The sky is like a sponge soaked in galaxies and until you "squeeze" it with a telescope, you hardly know they're there.

NGC 4565 was discovered by English astronomer William Herschel in 1785. Herschel was also the discoverer of the planet Uranus. In this telescopic photo you can begin to appreciate the rich detail in the dust clouds silhouetted against the combined glow of billions of stars in the galaxy's central bulge. Credit: ESO

Of the billions of Milky Ways out there, I spent a half hour last night with one that goes by NGC 4565 and nicknamed the Needle Galaxy because of its incredibly large, thin disk. The Needle is in Coma Berenices, a dim constellation chasing the tail of Leo the Lion in the east. If you ever wanted a good idea of what our galaxy the Milky Way would look like if you could get outside of it and look back, NGC 4565 is the place to go. It's similar in size -- 100,000 light years across -- and has a spiral form and dark dust clouds along its mid-plane just like our own. Because of its distance of 30 million light years, the Needle's too faint for binoculars but telescopes from 6-inches on up show its delicate form beautifully.

Don't have a telescope? Not to worry. Both amateur and professional astronomers are attracted to this galaxy like kids to candy. You'll find many photographs of it in books, magazines and online. Click HERE for a hi-res version of the photo above or HERE to see a closeup of one of the galaxy's arms resolved into stars by the Hubble Space Telescope. We see NGC 4565 edge-on or from the side so its pinwheel-like disk looks very flat. If we could hover above both it and the Milky Way we'd be treated to a grand display of spiral arms. We'll spend more time getting to know galaxies inside and out as the spring unfolds.

Posted by: rking@duluthnews.com on 3/17/2010 at 10:48 AM | Comments (0) | Permalink | Edit

Tags: daily updates, northern lights, ngc 4565, coma berenices, milky way, astro bob, life, aurora, galaxy