Blogs / Bad Astronomy

Artist’s impression of the planetary system around Gliese 581. Courtesy ESO.

The European Southern Observatory is reporting that they have found the most Earthlike planet yet orbiting another star. It has about 1.5 times the Earth’s diameter, and five times its mass. This makes it the smallest extrasolar planet yet found (two other planets have already been found orbiting that star, with 15 and 8 times Earth’s mass).

This is amazing enough! But it gets far, far better. The parent star, Gliese 581, is a red dwarf, meaning it’s smaller and cooler than the Sun. The as-yet unnamed planet orbits this star much closer than the Earth does the Sun; it stays about 11 million kilometers (6.7 million miles) from its star, while the Earth is 150 million km (93 million miles) from the Sun.

But remember, Gliese 581 is cooler than the Sun, so at this distance the planet would actually be very temperate: models show it would be between 0 and 40 Celsius! If that doesn’t grab you, then consider this:

That is warm enough for water to be a liquid.

So what we may have here is a terrestrial planet with liquid water on its surface.

Let me be clear: this is not a guarantee! We have not actually gotten an image of the planet; its presence is indicated by the gravitational effect it has on its star as it orbits (once every 13 days, incidentally). So we don’t know if the planet is dry, or covered in oceans, or even if it’s rocky like the Earth — though models indicate it will either be rocky or possibly even covered by oceans.

And this planet is Earthlike, but not Earth! The surface gravity is more than twice that of Earth’s (22 m/s/s versus 9.8 m/s/s on Earth) and who knows what the atmosphere is like. But the basic characteristics are certainly provocative! Almost all the planets detected using this method are more massive than Jupiter, and extremely hot, way too hot to be hospitable to our kind of life.

Why is this planet important? Well, one of the major goals of science right now is to find out if life has arisen and evolved elsewhere in the Universe. Up until 1995 we weren’t even sure if any other stars had planets! Now we know of hundreds, and as the technology gets better, we can find smaller and smaller ones. We’re right on the verge of being able to find ones just like Earth. And while of course we cannot know if this newly found planet has life or not, it’s our best bet yet!

There is much more to learn about this planet. Getting an image of it is currently not possible: at a distance of 20 or so light years, Gliese 581 one of the closest stars in the sky, but still far too distant to separate the planet from the star. So I’m left wondering about this planet. Does it rotate once every orbit due to the gravitational interaction with its star? This is what has happened to every moon in the solar system; they spin at the same rate they go around their parent bodies, so they always show one face to their parent (which is why the Moon always has the same face toward us here on Earth). If so, how does this affect the atmosphere? Models indicate that the air should carry the warmth of the star around the planet, so the temperatures should actually be fairly moderate on both the day and night sides of such a world. But if it’s covered by an ocean, how does having one side of the planet eternally locked into daylight affect it?

Criminy, what would life be like on a tidally-locked ocean world?

Wow. One of my favorite aspects of science is taking an idea and running with it. I don’t encourage too much speculation beyond what’s known — and in this case we don’t know all that much — but it sure can be fun. Especially when what we’re starting with is so exciting.

So hat’s off to the team of scientists who made this momentous discovery. May they make many more… and may their results get ever smaller, and ever cooler.

Keith Cowing at NASAWatch put up a link to a video put out ostensibly by NASA, but it’s not like other ones they’ve done. This one is very, very cool.

The hi-res version is here, and is worth waiting for.

The music is cool. It has "Raiders of the Lost Ark" overtones at first, as Keith points out, then it kicks into a "Battlestar Galactica" thing. I wonder who did this, and what the music is from?

Incidentally, this is the kind of thing I was yelling at NASA to do years ago (well, not literally yelling, but I felt like it sometimes). A handful of these trailers, playing in movie theaters before some crappy SciFi epic, would go a long way toward showing the public that going back to the Moon is such an amazing and awe-inspiring thing to do. NASA needs to do lots more stuff like this.

NASA: you know where to find me. I still wanna help.

Update (April 26, 2007): I somehow missed the fact that the release of this image is also available at the Space Telescope Science Institute itself. Duh! Sorry about the oversight.

Today is the 17th anniversary of Hubble’s launch on April 24, 1990.

Oh, I remember it. There has been so much knowledge gained since then, and so much of it due to that observatory! And it’s changed the way the public looks at astronomy, too. I remember when Hubble was the butt of jokes from magazines to late-night talk shows — it was a colossally expensive endeavor, and it was launched with a flawed mirror.

We’ve come a long way.

To celebrate 6209 days in space, the European arm of the Hubble science community has released the extraordinary image above. It’s of the Carina nebula, a vast complex of gas, dust, stars, forces, and energy sitting 7500 light years away. The image is a mosaic of 50 frames from the Advanced Camera for Surveys onboard Hubble. It shows a region only 50 light years wide… and yet there is so much to see!

That picture I posted above does not do the original justice at all. I’ve extracted some highlights below, but you should really do yourself a favor and grab the high-res version of the image and scan across it. If your machine can hack it, try the 200 Mb version. If you happen to have a Cray lying around, then why waste your time with the kid’s stuff? Grab the 500 Mb image! Or, better, you can take a look at a copy safely stored on a computer in Europe, and zoom, pan, and scan to your heart’s delight.

Honestly, 7500 light years distant isn’t enough buffer for my taste. Sitting inside that nebula are a dozen stars with more than 50 times the Sun’s mass, stars guaranteed to explode some day as titanic supernovae. One star, Eta Carinae, is in its death throes, violently expelling gas in eruptive events that are only a hair’s breadth shy of a supernova themselves. The last such, in 1843, expelled two vast lobes of gas — seen in the image above as an elongation in the gas surrounding the star — brightening Eta so much it became the second brightest star in the sky, and it’s nearly 1000 farther away than the first brightest! While those other stars in the Carina nebula will explode in the next million years or so, Eta has far less time, maybe thousands of years… or it may blow tonight. We don’t know. It’s far enough away that it poses no immediate threat to us, but when it does go, it’ll be one of the brightest objects in the sky once again.

Despite the brutal and violent forces tossed around inside the nebula, there are also regions of ethereal and delicate beauty. As gas from a star or a cluster of stars expands, it rams the other gas around it, forming a shock wave. Like the water displaced by the front of a moving boat, the gas shock forms a bow shape. In this case, it’s difficult to tell from where the gas is coming. I see no star at the focus of the arc, no tell-tale signs of a source. Maybe it’s from a long-dead supernova, the original star having torn itself literally to shreds. All that’s left is this ghostly wave of gas, slowly mingling with and mixing into the nebula itself. As it compresses the surrounding gas, it may cause the nebula to collapse locally, forming more stars, and setting the cycle going once again.

There’s plenty of evidence that’s still going on in the Carina nebula. This part of the image shows a dense cluster of newborn stars, shining like beacons amidst the strewn gas and dust. These are most likely young stars, fiercely hot, and like many of their brethren in the nebula, doomed to explode someday. The smudges you see are not image defects: those are extremely dense globules of dust and gas. These are star forming factories in miniature: maybe only a few stars are forming in its core. Maybe only one. It looks like its sitting right in the cluster, but it may be many light years in front of or behind it: one of the maddening aspects of image analysis is the lack of depth. I doubt it’s in the cluster; the violent winds and flood of ultraviolet light would make quick work of such a delicate cocoon.

How do I know? Well, look at this:

This may be my favorite part of this huge image. This is a relatively dense section of the nebula, located above and to the right of the star cluster. See how there appear to be lower-left to upper-right series of alignments in it? Those all point more or less toward the cluster. This knot of gas is definitely being modified by the powerful winds and light from those nascent stars. If you look at a higher resolution image you can see shocks and rammed gas, and outflow all pouring off the dense knots like a snowball being blasted by a blowtorch. This clump of matter may not last more than a few thousand years before being literally blown away by that cluster.

What a place, the Carina nebula! Hundreds of light years across; hundreds of thousands of solar masses of material; stars of all sizes, masses, temperatures, and brightnesses forming; gas and dust blown into all manners of shapes; stars dying, caught in the act. It’s construction and deconstruction on a mind-numbing scale, and it’s all laid out for us to see, thanks to telescopes like Hubble and others on the ground and in space.

In 17 years, Hubble has taken a half million images of 25,000 astronomical objects, producing 30 terabytes of data in the process. If everything goes as planned, NASA will service this magnificent instrument yet again in 2008, and it will have many more years of service. What other images will it take, inviting us to peer farther into the Universe and add even more to our already considerable knowledge?

Or will the Universe itself have something to say about our hubris?

I don’t believe in signs… but I do believe in humor, and if the Universe has a sense of one, it has a funny way of showing it. But you can find everything in that nebula. Even an attitude.