Blogs / Bad Astronomy

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

When Galileo first turned his telescope to the sky, almost exactly 400 years ago, he could not possibly have known what he was starting.

Today, four centuries later, we’ve come a long, long way. To celebrate the anniversary of Galileo’s telescopic revolution, NASA’s Great Observatories — Hubble, Spitzer, and Chandra — have released a jaw-dropping mosaic of the very heart of the Milky Way galaxy. Behold!

[Oh yes, you want to click to embiggen that-- what I show here is a very compressed version. Or you can go here for a massive copy. You can also get wallpaper versions here.]

This image is nothing less than a heroic effort of astronomical artistry. It’s a chunk of the sky 38 x 14 arcminutes across, or about half the size of the full Moon, and it’s aimed right into the core of our galaxy. See the bright spot just to the right of the center? Buried in there behind light years of dust and gas is the monster of the Milky Way, a black hole with four million times the mass of the Sun. But even that is dwarfed by the 400 billion solar mass heft of the entire galaxy.

There is so much going on in this image it’s hard to know where to start. But first… the Hubble images are in the near-infrared, with a wavelength a little more than twice what the eye can see (1.87 microns for those playing at home). That’s represented in the image as yellow. Spitzer contributed observations in four infrared wavelengths (3.6, 4.5, 5.8, and 8.0 microns), and those are depicted in red. Chandra sees X-rays which are normally written as units of energy, but to remain consistent with the other two images, they were at wavelengths of 0.0005, 0.00025, and 0.00016 microns, and are shown in blue.

What does all this mean? Different objects emit light at different characteristic wavelengths. Warm dust, for example, emits strongly in the infrared. Stars and warm gas emit visible and near-infrared light. Violently heated gas, affected by huge magnetic fields or shocked by colossal collisions glows in X-rays. So this image is a polychromatic view of the crowded downtown region of a bustling city: our galaxy.

You might want to look at an annotated version of this image so you can get your bearings. It’s worth it!

The huge arches of gas on the left are actually the edges of gigantic molecular clouds (dense nebulae where stars are born), lit up by the torrential blast of light from a clutch of massive stars nearby. This clot of stars, called the Arches Cluster due to the arcs it excites, can be seen as a small spot glowing blue just to the left of center in the picture. Don’t be deceived by its diminutive appearance: the Arches cluster has thousands of superstars in it, each dwarfing our Sun, and each capable of sleeting out vast amounts of radiation that lights up the gas surrounding it. Were this cluster much closer than its 25,000+ light year distance, it would blaze in our sky like a beacon. Replace the Sun in our solar system with just one of those stars, and the Earth would be fried beyond the capability of any life to survive. You might as well try living in the flame of an arc-welder.

Below and just to the left of the Arches is a clumpier, more twisted arc of gas called the Sickle. That’s a giant cavity being carved out of dense gas by the Quintuplet cluster, the pinkish glow in its center. It’s another nursery of stars like the Arches cluster, which is also blasting out light and stellar winds which eat away at the gas enveloping it. The Pistol Star resides there, perhaps one of the most massive stars in the Milky Way.

And there’s more! The blue glow on the left is from an X-ray binary called 1E1743.1-2834, what is probably a massive star being orbited by either a neutron star or a black hole. Matter is being stripped from the star and piling up outside the collapsed companion, where it gets heated up to millions of degrees and emits X-rays.

Supernovae remnants dot the image, as do stars, filaments of gas, clouds of dust, and more. This picture is an astronomer’s dream, a map of everything someone might want to visit with a starship — as long as the shields are at full strength. This image is also a map of violence, turbulence, and unrest… a typical scene, so we think, of any normal spiral galaxy like ours. And our Galaxy’s center is considered quiet by astronomers! Some are far worse.

But this is home for us. It’s a place of unimaginable fury but also astonishing beauty… and we see it now as we do because we have dared to examine the world around us, to use tools we invent to peer closer, to magnify the tiny, to extend our eyes into realms we once didn’t even know existed. And every time we do — every single time — we find more questions, more puzzles, more things to examine.

And we find art. Galileo wasn’t the first to turn his telescope to the sky, nor was he the first to record what he saw. But he was the one who made everyone see what he did, and for that, all these years later, he is owed a debt of gratitude.

Need some pretty for today? Then you should feast your eyes on this exquisite picture of the cluster of stars known as the Jewel Box:

[Click to encaret].

Gee, I can’t imagine why’d they name it the Jewel Box! In fact, this is a large cluster of stars located in the southern constellation of Crux, also called the Southern Cross. It’s bright enough to be seen with the unaided eye, in fact (though when I was in the Galapagos last year, Crux didn’t get high enough off the horizon to see the cluster very well).

This image, taken by the Hubble Space Telescope, shows the multicolored stars dwelling in the cluster. But not for long, I’ll add. Those bluish stars are O and B-type supergiants, massive stars that scream through their nuclear fuel thousands of times faster than the Sun, meaning their lives are far shorter. The red beacon there at the upper right is a red supergiant, a star right on the edge of disaster (literally, since the word means "bad or ill star"). It won’t be long, maybe a few million more years, when all the bright stars in the Jewel Box will go supernova, detonating in titanic explosions each of which, from the Earth, will outshine Venus!

The image is one of three from three different telescopes, taken to examine the core of the cluster (with Hubble) as well as the outer regions. The picture on the left is from the Very Large Telescope in Chile, and shows a larger area around the cluster (the bright red star is the same as in the Hubble picture). Incredibly, due to the huge telescope’s light-gathering abilities, this picture is actually only a 5.2 second exposure! It’s composed of three images: one in blue (2.6 seconds), one in yellow (1.3 s) and one in red (1.3 s). When you use a telescope with a mirror 8 frakkin’ meters across, bright stars don’t take long to show up.

Astronomers aren’t sure if the Sun was born in a cluster like the Jewel Box, or if it was formed in a smaller cloud by itself; both types of birth occur in the galaxy. I know it’s not scientific, but a part of me rather hopes that once upon a time, a few billion years ago, the Sun did in fact see its first light inside such a cluster. Imagine the sky, festooned with stars so bright they outshine the Moon, easily luminous enough to read by, and each glowing blue, red, yellow… that would have been a fantastic sight.

Some people think that science takes away the romance and wonder of the Universe, but I don’t think not knowing is romantic, especially when knowing gives us such lovely vistas to explore.

If you thought the Lagoon yesterday was pretty, then reset your awe-meter. Check. This. Out.

D’ya like that? Huh? Do ya? Had enough? No? Then check THIS out!

Jeebus. Click either to brobdingnangate. In fact, you can get massively huge versions here and here. We’re talking 30 and 40 Mb each, so be ye fairly warned, says I.

Those magnificent images are of the galaxies NGC 4402 and NGC 4522, respectively, as seen by the Hubble Space Telescope’s Advanced Camera for Surveys (from before the recent repair mission). They’re both spiral galaxies in the Virgo Cluster, the nearest large collection of galaxies to us, roughly 60 million light years from Earth.

If they look funny to you, then good! The Virgo Cluster is massive, and has a lot of gravity. The galaxies bound to it are moving like bees surrounding a hive, each in its own orbit going every which way. These galaxies are screaming through the cluster at speeds of 10 million kilometers per hour, a truly terrifying velocity.

There is an ethereal gas distributed between the galaxies called the intercluster medium. It’s incredibly thin, but over the size of a galaxy — especially when said galaxy is barreling through it at such tremendous speed — the gas can exert significant pressure, called ram pressure. The pressure is actually blowing the galaxies’ internal gas clouds out into the cluster itself, making them look a little bit like pickup trucks driving down a highway with dirt copiously pouring out the beds^*. This is especially obvious in NGC 4522 (the lower one), where you can see bright blue splotches, which are regions of intense star formation, along with dark lanes of dust actually above the galactic plane.

In NGC 4022, you can see how the ram pressure is roiling up the dust in the galaxy, and also blowing it back, though apparently not as briskly as in the other galaxy.

These pictures are incredible. Poke around them; you can see amazing detail in the galaxies themselves, as well as hundreds, maybe thousands of background galaxies.

It’s been a while since we’ve seen deep, glorious pictures of spiral galaxies from Hubble. Now that ACS is working again, and it’s being joined by the equally powerful Wide Field Camera 3, we’ll be seeing lots more of these. Get used to it.

Image credits: NASA and ESA.