Tag: Small Magellanic Cloud

This is a galaxy?

By Phil Plait | June 27, 2011 10:04 am

I love to post pretty pictures of galaxies and wax lyrical about their magnificent structure, complex history, and complicated internal compositions.

… and then there’s the Carina Dwarf galaxy. It’s so small and faint it wasn’t even discovered until 1977 even though it’s one of the closest galaxies in the sky! How did it avoid detection so long? This’ll make it obvious:

[Click to unendwarfenate.]

See it? Yeah, it’s that faint smattering of stars in the middle of the picture (the bright star near the center is in our Milky Way and coincidentally aligned with Carina). Not much to it, is there? It’s about 300,000 light years away, only 1/10th as far as the much brighter and more famous Andromeda Galaxy, and only about twice as distant as our two satellite galaxies, the Small and Large Magellanic Clouds, both of which are easily visible to the unaided eye.

Like the LMC and SMC, it is apparently a satellite of the Milky Way, but formed long after we did; studies of the stars in the Carina Dwarf indicate it’s only about 7 billion years old at most, while our galaxy is well over 10 billion years old. It probably formed from primordial gas orbiting the Milky Way, taking much longer due to its low mass and relatively quiet environment.

This image is a combination of observations taken with the 2.2 meter MPG/ESO and the Victor M. Blanco 4-meter telescopes in Chile. It shows that the galaxy has very little or no gas at all in it, and so its career in star-formation is long dead. But there’s still much to learn from such objects: they get eaten by bigger galaxies, for example. This cosmic cannibalism is one way galaxies like ours get so big, so studying these smaller bite-sized snacks in situ help us learn about ones we’ve already munched on.

Plus, galaxies like Carina might be the most common in the Universe! We just can’t see them because even at relatively small distances they fade away into the background. They may not be as flashy as spirals or as monstrous as giant elliptical galaxies, but they play an important role in building up such beasts. The more we know about them, the better we’ll understand the Universe itself.

Image credit: ESO/G. Bono & CTIO


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CATEGORIZED UNDER: Astronomy, Pretty pictures

The Milky Way bridges from here to eternity

By Phil Plait | April 6, 2011 7:00 am

The European Southern Observatory’s monster 8-meter Very Large Telescope observatory is silhouetted against the galaxy itself — and beyond — in this stunning vista of the high Atacama desert of Chile:

[Click to southernhemispherenate.]

What a breathtaking panorama! It’s dominated by the Milky Way Galaxy, hanging low near the horizon. We live inside the disk of our galaxy, so we see it from the inside out. It makes a thick line across the sky, the central hub bulging out in the middle. Dust chokes the interstellar view, creating dark lanes that block the light from stars behind them.

On the left you can see the two companion dwarf galaxies to our own: the Large and Small Magellanic Clouds. They apparently hang side-by-side in the sky, but are separated by over 40,000 light years… and are removed from us by distances of 160,000 and 200,000 light years, respectively.

And on the right is our eye on the sky, Unit Telescope 1 of the VLT — and that’s only one of four of the giant 8 meter telescopes in operation. I like the imagery here: the telescope at one end, distant galaxies on the other, and bridging them like a cosmic rainbow is our home galaxy itself.

You may make your own metaphor here, but the one I choose is obvious. You might even say this post is entitled to it.

[Edited to add: After writing this, but before posting it, I found that APOD had a very similar picture to this one. Funny coincidence!]

Image credit: ESO/Y. Beletsky


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CATEGORIZED UNDER: Astronomy, Pretty pictures

Beauty in violence

By Phil Plait | February 26, 2010 6:56 am

The European Southern Observatory just released a very pretty picture of the nebula NGC 346. Check this out:

eso_ngc346

I strongly urge you to click that to ennebulanate to the higher-res version; I had to shrink and compress it quite a bit to fit it here.

The picture is lovely, showing a star-forming region in the Small Magellanic Cloud, a satellite galaxy to our own. The nebula’s about 200 light years across, and 200,000 light years away.

I won’t go into details; you can go to the ESO site for that. But there’s something I want to point out. The sharp wisps you see strewn this way and that inside the gas are due to vast and powerful winds of subatomic particles blowing from the surfaces of massive stars that are newly-born from that very gas. These streams slam into the gas, compressing it across trillions of kilometers, producing storm fronts that are thinner than a laboratory vacuum but are still so voluminous that the mass adds up to many times that of the Sun’s. Added to that is a flood of high-energy ultraviolet light from these massive stars, energy blasting out as they furiously churn out energy in their cores, leading ultimately to their demise in supernovae explosions.

So while you gaze at this nebula and wonder at its beauty, remember that in our Universe, beauty is borne by great violence. If there’s a life lesson in there I’m unaware of it. But it is worth pondering.

CATEGORIZED UNDER: Astronomy, Pretty pictures
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