Monday, December 12, 2011

The 'Christmas Planet:' Kepler-22b

"Potentially Earth-Like Planet Has Right Temperature for Life"
ScienceNow, Wired Science (December 5, 2011)

"For the first time, astronomers have found a planet smack in the middle of the habitable zone of its sunlike star, where temperatures are good for life. 'If this planet has a surface, it would have a very nice temperature of some 70° Fahrenheit [21°C],' says William Borucki of NASA's Ames Research Center here, who is the principal investigator of NASA's Kepler space telescope. '[It's] another milestone on the journey of discovering Earth's twin,' adds Ames director Simon 'Pete' Worden.

"Unfortunately, the true nature of the planet, named Kepler-22b, remains unknown. It is 2.4 times the size of Earth, but its mass, and hence its composition, has not yet been determined. 'There's a good chance it could be rocky,' Borucki says, although he adds that the planet would probably contain huge amounts of compressed ice, too. It might even have a global ocean. 'We have no planets like this in our own solar system.'

"Kepler-22b is 600 light-years away. Every 290 days, it orbits a star that is just a bit smaller and cooler than our own sun. The Kepler telescope, launched in 2009 to scan the skies for Earth-like worlds, found the planet because it sees the orbit edge on. That means that every 290 days, the world transits the surface of the star, blocking out a minute fraction of its light.

"Borucki likes to call the new discovery the Christmas planet. 'It's a great gift,' he said...."

This is exciting news for the Lemming. Astronomers have spotted planets that are close to the right distance from their star before; and have spotted planets that are only a few times as massive as Earth. Kepler-22b is roughly the same size as Earth, and at roughly the 'right' distance from its parent star: so it's possible that there is life there.

Or, not. We don't know what Kepler-22b's mass is, which will tell researchers how dense it is. And we don't know what sort of light gets bounced off Kepler-22b. If the expolanet's density is in the neighborhood of 5.5 grams per cubic centimeter, like Earth, and reflects a lot of bluish-white light, like Earth: it's still not a 'twin' of Earth. But it would be awfully close.

By the way, that 5.5 grams/cubic centimeter means that Earth is 5.5 times as dense as water. About. Water's density is 1 gram per cubic centimeter at 39.2°F. Boiling water (at sea level) is 0.95865 gram per cubic centimeter, and that's another topic. (USGS)

Only 600 Light Years: That's Close

Depending on what you're looking at, 600 light years is a huge distance, or practically next door. It's the distance light travels in 600 years: so the light that the Kepler observatory picked up started out around the time when the first golf balls were made. That's about 3,527,175,200,000,000 miles. Give or take a few hundred million.

Compared to the distance the Lemming travels, going to the nearest grocery, that's a long way away.

Backing off a little, and looking back at Earth's neighborhood, Kepler 22-b is practically next door. On the scale of this picture, the "S" in "Sun" is well over 1,200 light years across: twice the distance to Kepler-22b.

(from Department of Physics, University of Oregon, used w/o permission)

Life, the Universe, and All That

That Wired Science article doesn't have the sort of entertainment value that "Star Wars" or "Star Trek II: The Wrath of Kahn" offer. For something in a 'science news' online publication, that's not the point.

What fascinates the Lemming about Kepler 22-b, and the rapidly growing list of known exoplanets, is the knowledge that the collection of planets, moons, and assorted debris, circling our star isn't quite unique.

We still don't know whether there are many - or any - other orderly systems like ours, with planets circling in neatly nested circles. And we're probably a long way from knowing whether there's life somewhere other than on Earth.

As for traveling to planets circling other stars: That's another topic.

Related posts:
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'Star Trek,' no; easy, no; possible, yes:

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