January 23, 2008 7:47

So Where Were We?

When last we met...or...whatever we do here, I said you'd have to register in order to make comments from now on. That moment is evidently here, or so my blogmasters tell me. It's to prevent spam bots from flooding the site, so let's see if it works. Looking forward to resuming....

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January 19, 2008 8:46

New Policy on Comments

From now on, everyone has to agree with me.

OK, that's not the new policy, unless I want comments to drop to zero. The truth is that our beloved spam filter is being overwhelmed, so while lots of the stuff is still being filtered, much to much is getting through. And while it gives me great pleasure to manually delete them (you should see me cackling with joy every time), it's taking up too much time.

So from now on, here's the deal; if you want to comment from now on, you have to register. They promise me it'll be easy, and it's a one-time thing, so it shouldn't be a burden. Watch this space for instructions.

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January 11, 2008 10:48

Dark Matter Made Visible (sort of)

Magenta-colored areas represent the presence of invisible dark matter that surrounds clusters of galaxies/NASA, ESA, C. Heymans (University of British Columbia, Vancouver), M. Gray (University of Nottingham, U.K.), M. Barden (Innsbruck), the STAGES collaboration, C. Wolf (Oxford University, U.K.), K. Meisenheimer (Max-Planck Institute for Astronomy, Heidelberg), and the COMBO-17 collaboration

A couple of days ago, I blogged on a cosmic optical illusion, and said (or should have said) that it's not just bizarre; the phenomenon of gravitational lensing is also useful in all sorts of ways for probing the unseen universe.

The image above (another one released at this week's American Astronomical Society meeting) is a perfect example. by Meghan Gray, of the University of Nottingham in the U.K., and Catherine Heymans of the University of British Columbia in Vancouver led a team that started out with a ground-based image of the Abell 901/902 supercluster of galaxies—that is, a lot of clusters clumped together into a giant agglomeration (most of the bright spots you see are galaxies, not stars).

Then they used the Hubble to measure the precise shapes of galaxies, not in the supercluster, but in the background. Gravitational lensing subtly distorts those more-distant galaxies' shapes—and by measuring the precise warping of some 60,000 of them, calculated the distribution of whatever foreground mass was doing the distorting. Most of that is dark matter, which they tinted magenta so we could see where it is.

The main idea was to understand how dark matter affects the growth and evolution of superclusters—but for most of us, the simple fact that so much dark matter is out there , demonstrated so amply here and in the closeup below, is reason enough to be humbled by the remarkable grandeur of the universe.

My two cents, anyway.

Closeup of the above/NASA, ESA, C. Heymans (University of British Columbia, Vancouver), M. Gray (University of Nottingham, U.K.), M. Barden (Innsbruck), the STAGES collaboration, C. Wolf (Oxford University, U.K.), K. Meisenheimer (Max-Planck Institute for Astronomy, Heidelberg), and the COMBO-17 collaboration

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January 11, 2008 10:08

More Astronomy Porn

These giant, glowing clouds of gas and dust are the remnants of two different exploding stars. /Gemini Observatory / Multi-Object Spectrograph (GMOS-South) Image

No, the headline doesn't't refer to astronomers behaving badly—it's just that the pictures we're getting from deep space this week are too delectable to pass up. They're all coming out now because the American Astronomical Society is in the midst of its annual winter meeting (the venue changes each year; this time they're in Austin, Texas) and observatories are falling over themselves to show their latest, greatest results.

This one shows the expanding clouds of gas and dust from two independent supernova explosions that lie on a line of sight with each other (i.e., they're not really overlapping, despite how it looks). The explosions happened in the Large Magellanic Cloud, a small companion galaxy of the Milky Way, probably tens of thousands of years earlier than what we're seeing here, but since the LMC is about 160,000 light-years away, the actual supernovas went off much longer ago.

Explosions like these spew out elements like carbon and oxygen, which are only formed in the nuclear furnaces at the cores of stars. Without stars to manufacture these and other key elements, planets—and the people who live on them—wouldn't exist.

This image looks like it must have come from the Hubble, but not so: it's from the Gemini South observatory, in Chile (its twin, Gemini North, is in Hawaii). Just goes to show you that while it's nice to have a telescope in space, it isn't always necessary.

Note of pride: my very first cover story for TIME was on a supernova that went off in the Large Magellanic cloud in 1987 (or again, the light got here in '87).

More to come...

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January 10, 2008 12:18

Double Cosmic Ring of Fire...With a Catch

An embedded pair of "Einstein Rings"—in essence, a cosmic optical illusion./NASA, ESA, and R. Gavazzi and T. Treu (University of California, Santa Barbara), and the SLACS team

The catch is that it doesn't really exist, even though you can see it through a telescope. Or at least, the Hubble can. What you're looking at is a galaxy (brightest spot in the left-hand image) surrounded by the magnified images of two more-distant galaxies that lie right behind it. Because gravity actually bends spacetime, making light rays travel in a curving path, the foreground galaxy's gravitational field distorts the images of the two further objects into what look like rings (the right-hand closeup has the foreground galaxy digitally erased so you can see the rings better).

Einstein himself discussed the idea of "gravitational lensing" in a paper published in the 1930s, but thought they'd never be seen. The first one was found in 1979; they're now a powerful tool in astronomers' arsenals, letting them do everything from detecting planets around distant stars to mapping out the extent of dark matter in and around galaxies.

In short, Einstein was, uncharacteristically, dead wrong.

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