Beam me up!

Bad Astronomy
The entire universe in blog form
Sept. 7 2010 7:00 AM

Beam me up!

Some astronomical pictures are simply and truly cool.

And this, my friends, is near the top of the list.

Phil Plait Phil Plait

Phil Plait writes Slate’s Bad Astronomy blog and is an astronomer, public speaker, science evangelizer, and author of Death From the Skies!  

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[Click to enlasenate.]

Yes, the wow factor is high with this one! And the thing is, what you see is what you get: it's a laser shooting out of an observatory straight up into the heart of our galaxy!

The observatory is of the European Southern flavor, in Chile. It houses the Very Large Telescope, which has a very nice little tool it can use: a laser guide star. The laser shoots up into the sky and excites atoms in the upper atmosphere, causing them to glow. That makes an artificial and very bright star in the sky! The telescope can then use that star to track the distortions in the atmosphere and compensate for them, allowing the images it makes to be incredibly clear and sharp.

Although it doesn't say so explicitly in the press release, given where the laser is pointing I'm guessing they were observing stars orbiting the supermassive black hole in the center of the Milky Way. Those stars can actually be seen to change their positions over time, allowing astronomers to calculate the mass of the black hole -- and using such methods they've found it to be a whopping 4 million times the mass of the Sun! The star positions need to be very accurate, making the laser guide star system invaluable.

The long time exposure of this image makes the laser obvious, as well as the incredible vista of the Milky Way streaming overhead. You can clearly see the central bulge of the galaxy, the spherical hub at the center containing billions of old, redder stars. The dark lane cutting across the center is due to vast amounts of dust created when stars are born and when they die, and that's mostly confined to the disk of the galaxy. Since we are inside that disk, it makes a long line, a stream, across the sky. I've seen it many times, though never from a truly dark site. Some day...

Tip o' the sharks with frikkin' laser beams attached to their heads to the ESO Observatory Twitter stream. Image credit: ESO/Y. Beletsky


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