Blogs / Bad Astronomy

You know what "galaxy" means in Latin Greek, don’t you?

Yeah, it’s Saturn, not the Milky Way, but still. That is made of awesome. I want to go to that coffee shop!

Via Reddit.

Check. This. Out.

You might think that’s an alien spore, or a crystal of some kind. But it’s actually what appears to be a rendering of a three-dimensional fractal!

Fractals are very interesting. There are different ways to describe one, but one way to think of one is that it’s a shape that looks the same no matter what magnification you use. You can double it, triple it, make it 10,876,432 times bigger, and the object still displays (more or less) the same features. The term fractal was coined by Benoît Mandelbrot, and there is an entire subclass of fractals named after him. They are seen in nature (and art, like here) quite a bit. Coastlines are fractal, as are — seriously — some kinds of broccoli.

However, fractals are generally calculated in two dimensions. What’s new here is that the fractal pattern has now been calculated in three dimensions! That is, to say the least, a non-trivial procedure — I used to play with some of the 2D equations many years ago, on my old 512k Fat Mac, with code written in Pascal (yes, with the semicolons and everything) and it was fascinating if very complex.

But the 3D idea has been written up by Daniel White, who, along with others, figured out how to create and render such an incredible object. He even created a "fly-over" video to demonstrate the fractal pattern:

Wow. Even if the math of this makes no sense at all to you, the beauty of this should be apparent.

Which brings up a point: why are mathematical shapes beautiful? What makes them so pleasing to our eyes and brain; why did we evolve an appreciation for such things? I don’t know, and at some point I’ll have to research that a bit — understanding the principles behind this will help me appreciate it even more.

Tip of the fractionally dimension hat to Fark.

When you poke the Pillsbury dough boy in his bulging tummy, he giggles. When you poke the bulge in NGC 4710, however, you get the history of how galaxies form. Voila!

Awesome. And you really need to embiggen this one to get a sense of the incredible beauty and resolution of the picture. Try the 4000 x 2000 pixel one on for size!

NGC 4710 is an edge-on spiral galaxy located about 60 million light years away in the Virgo Cluster. That puts it in the next town over, cosmically speaking, so it’s a rich target for something like Hubble Space Telescope. This image, newly released (but taken in 2006 before the last servicing mission), reveals spectacular details in the sideways galaxy. Views like this really accentuate the huge sprawling dust complexes littering spiral galaxies.

But it isn’t the dust astronomers are interested in here. Spirals have three main parts: a more-or-less spherical bulge in the center, the disk (which has the spiral arms), and a giant halo of stars surrounding them both. We understand a lot about spirals, but lots of big questions remain, including how and when the bulge forms. A galaxy is born out of a vast, collapsing cloud of gas. It’s possible that the bulge forms straight away, with the infalling gas of the protogalaxy making stars which build up in the galactic center. It’s also possible that the bulge forms later, well after the galaxy itself takes shape, as stars in the inner part of the galactic disk interact gravitationally and fall to the center, building up the bulge.

It turns out there might be a way to distinguish these formation mechanisms, even billions of years after the fact. Globular clusters are small (well, a couple of dozen light years across or so) balls of hundreds of thousands of stars. They orbit bigger galaxies; the Milky Way has well over 100 orbiting it. We know that many globulars formed at the same time as their parent galaxies; the stars in the clusters can be incredibly old. This means that perhaps the formation of the galaxy and its attendant clusters are connected.

In fact, it’s thought that the same process that creates the bulge in the "forms at the same time as the galaxy itself" scenario also creates globular clusters, but the other process (stars from the disk falling inward) does not create globulars.

That’s where NGC 4710 comes in. Being edge-on, we can see the bulge clearly, so it can be studied. But it also presents a good view of its globulars, so scientists can look at pictures like this one and simply count up the number of globular clusters near the galaxy and then figure out if the number is consistent with one of the two formation mechanisms.

In this case, NGC 4710 sports very few globulars, indicating the bulge formed after the galaxy itself. But NGC 4710 is only one of many galaxies being studied this way. Will they all show the same sluggish beginnings to their central bulges?

Time will tell. But I hope that as more of these galaxies are studied more images as lovely as this one become available.

Image credit: NASA & ESA

What does a star on the edge of death look like? Perhaps not what you think:

This series of images [as usual, click to embiggen], from the European Southern Observatory’s Very Large Telescope, will take some ’splainin. Hang on.

A supernova — an exploding star — is among the brightest single objects in the known Universe. A supernova can release as much energy in a single second as the Sun will in a thousand years.

Most people think of supernovae as massive stars exploding at the end of their lives, but there is another kind. When the Sun finally dies in a few billion more years, it will shed most of the material making up its outer layers, revealing the white-hot, dense core. This superhot ball will have half the mass of the Sun in it, but only be the size of the Earth. We call such a thing a white dwarf.

If a white dwarf orbits a normal star like the Sun, it can draw material off. This matter piles up on the surface and can eventually detonate like a stellar thermonuclear bomb. We call these Type Ia supernovae.

The thing is, massive stars are bright, so we can see them a long way off. We know of many stars in our galaxy that can blow that way (though all too far away to hurt us). But a Type Ia progenitor is faint, and hard to spot. Usually, the first notice we get of one is when it explodes, and we see the sudden and vast increase in light in a distant galaxy.

But astronomers have spotted a potential Type Ia supernova in our own galaxy, a ticking time bomb about 25,000 light years away. Called V445 Puppis, in November 2000 it underwent an explosive event: not a supernova, but a regular nova, the detonation of small (in cosmic terms) amount of material. Still, it ejected a lot of matter — several times the mass of the entire Earth — at very high speed, about 24 million kilometers per hour (14 million mph). That would reach from the Earth to the Moon in one minute flat. Over the course of several years, astronomers have taken images of the expanding debris, and the change — seen in the picture above — is dramatic, lovely, and terrifying.

The debris did not expand spherically because the two stars are in a tight orbit, circling each other rapidly. The matter drawn off the normal star forms a thick disk around the white dwarf. When the material on the surface exploded, it couldn’t go through the disk, so it went up and down, above and below the disk. Over time it forms what’s called a bipolar structure, because it comes out of the poles of the star. We see lots of similar bipolar objects, but not usually in a system that’s about to go bye-bye.

Tellingly, there is no detectable hydrogen in the system. The surface of the white dwarf appears to be mostly helium, and the normal star looks to be dumping only helium on the white dwarf. Type Ia supernovae are hydrogen poor, even lacking it completely, so that fits.

Also, the mass of the white dwarf in V445 Puppis is on the thin hairy edge of the maximum it can be before it blows. When a white dwarf reaches 1.4 times the mass of the Sun, it goes kablooie (I had to calculate this as a homework problem in grad school). V445’s mass? 1.35 times that of the Sun.

Yikes.

So when will the system go off? Hard to say. It may not be for thousands of years, or even longer. At that distance, it will be very bright in the sky, brighter than Venus. It won’t hurt us; it’s way too far away to to do that. But a nearby supernova of this type would be a huge boon to astronomy! It’s this flavor of supernova we use to measure the expansion of the Universe (since they are so bright they can be seen very far away, and tend to blow up with the same brightness every time).

It’s a little funny to think that the death of a star so many quadrillions of kilometers away can actually be a benefit to us. But remember, the calcium in our bones and iron in our blood came from supernovae like the one V445 Puppis will eventually become, so not only do we learn more about the Universe from them, we owe our very existence to them as well.

German amateur astronomer Bernhard Christ was in the right place at the right time — due to very careful planning and foresight — and captured this astonishing scene:

[Click to embiggen.]

That’s the International Space Station crossing the face of the Moon, what astronomers call a transit (like an eclipse, but when something small goes in front of something big). This image is actually a composite of several images taken in a row, with some sharpening to make it cleaner looking.

The transit only lasted for 0.4 seconds, so Christ had to be on the ball to capture this. He used a digital astronomical camera that can take what is essentially video (really just rapid still shots, but after all that’s what video is), and processed the individual frames. It’s a gorgeous image, with the Moon looking really stunning.

And if you’re wondering why he only got four shots of the ISS, look again: there is a shot of it just inside the limb of the Moon, but it’s low contrast and hard to see. Just follow the path of the ISS as it crosses the Moon and you’ll find it.

My thanks to Herr Doktor Christ for allowing me to post this picture. Well done, and vielen Dank!

The ESA spacecraft Rosetta swings past the Earth in a few hours, but look at what it did when it was still 630,000 km (400,000 miles) from home:

Sigh. So lovely.

Rosetta took an image every hour for 24 hours; they’re making a movie which will be online soon. That should be spectacular!

Via Digg I found a lovely website called Light Stalking, with tips and fantastic photos for amateur photographers. The site is featuring wide-angle (that is, not through a telescope) pictures of the sky taken by amateurs, and they’re lovely. The pix were culled from Flickr (though not freely licensed, so I cannot post any here), but it’s easier to get them all from one place. Take a look! Maybe they’ll inspire you to try to get some of your own.