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Tuesday, 12 August 2008

The search for our aliens spouses continues

Two very interesting articles for the space fans.
After a discussion in one internet forum, I realised people don't really know about the development of the search of Earth-like planets, so I think this article is a good opportunity to enlighten them.
I'm very sure I had an article on the middle sized planets recently, but this one is more popularly oriented so I'll repost it.
So, on the first article, just notice how the article starts with the accomplishment of the Swiss team and then it shift towards the past accomplishments of US teams. Lol, it's not very amusing, but oh, well, we all know that science is a cold war. But in any case, the moral is obvious: planets with different size are VERY common in the near Kosmos so we should expect finding an Earth-sized planet very very soon. The size, of course, isn't all that matters, but it's a good beginning.
The second article continues the subject with the straight-forward search for aliens. If you ask me, there is one significant flaw-they search for civilisations that are around our level. But that's just a small error in the assumptions. After all a significantly advanced civilisation isn't likely to show off to every jerk that wants a company. So to say.

A Bounty of Midsize Planets Is Reported

Published: June 17, 2008

About a third of all the Sun-like stars in our galaxy harbor modestly sized planets, according to a study announced Monday by a team of European astronomers.

At a meeting in Nantes, France, Michel Mayor of the Geneva Observatory and his group presented a list of 45 new planets, ranging in mass from slightly bigger than Earth to about twice as massive as Neptune, from a continuing survey of some 200 stars.

All of the planets orbit their stars in 50 days or less, well within the corresponding orbit of Mercury, which takes 88 days to go around the Sun, and well within frying distance of any lifelike creatures.

Among the bounty is a rare triple-planet system of “super-Earths” around the star HD 40307, about 42 light-years away in the constellation Pictor. The planets are roughly four, seven and nine times the mass of Earth and have orbital periods of 4, 10 and 20 days, respectively.

Dr. Mayor called the discoveries “only the tip of the iceberg” in a news release from the European Southern Observatory in Garching, Germany.

Theories of planet formation, Dr. Mayor said in an e-mail message from Nantes, hold that smaller planets like super-Earths and Neptunes should be numerous. “But evidently it was a nice surprise to see that with our instrument we have the sensitivity to detect that population,” he said.

Astronomers said the new results indicated that when their instruments got sensitive enough to detect even smaller planets, such planets would be there to be found.

In a terse statement, Dr. Mayor’s main rivals, a group of planet hunters led by Geoff Marcy of the University of California, Berkeley, and Paul Butler of the Carnegie Institution of Washington, said they were doing their own survey, to be completed within a year.

“Our survey will check the Swiss report that 30 percent of stars have super-Earths or Neptunes orbiting closer than Mercury does the Sun,” the group said in an e-mail message.

Dr. Mayor and his team discovered the first so-called exoplanet orbiting a regular star, known as Pegasi 51, in 1995. That planet, about half the mass of Jupiter, circles its star tightly in a four-day orbit. In the years since, some 270 exoplanets have been discovered, many of them like the original, so-called hot Jupiters in lethal scorching embraces of their stars.

Part of the reason that such unusual systems have been found first is that the detection method is biased toward finding large planets close to their stars. Both Dr. Mayor’s and Dr. Marcy’s groups use what is called the wobble method, deducing the presence of a planet by the to-and-fro gravitational tug it gives its star as it orbits. The more massive the planet and the closer it is, the bigger and more noticeable tug it will impart.

The tug perturbs the star’s velocity relative to Earth by as little as a few meters per second in the case of a super-Earth. That shows up as a periodic shift in the wavelength of light from the star.

In recent years, Dr. Mayor’s group has used a special spectrograph known as Harps, for High Accuracy Radial Velocity Planet Searcher, on a telescope at the European Southern Observatory’s site at La Silla, Chile, to detect such small wobbles in stars.

“Detection of planets with masses of about 2 Earth-masses (maybe less!) is possible,” Dr. Mayor said in an e-mail message.

To do much better, astronomers will have to go to space.

About one in 14 stars harbors a massive giant planet like Jupiter or Saturn, Dr. Mayor estimated. If in fact one in three harbors a Neptune or super-Earth, that is an appealing situation for astronomers and others who would like someday to find someplace livable or even someone living Out There. source

Narrowing the search for ET

If another advanced civilisation in the Milky Way is the proverbial needle, a group of researchers has suggested how we should narrow our search for it in the galactic haystack.

At a meeting of the American Astronomical Society in St Louis, Missouri, US, on Wednesday, Richard Conn Henry of Johns Hopkins University and colleagues proposed limiting the search for extra-terrestrial intelligence (SETI) to the ecliptic - the plane in which our solar system's planets orbit.

SETI begins with the hypothesis that another, more advanced civilisation in our galaxy is out there, trying to contact us. Assuming this is true, Henry says a search focused on the ecliptic "should lead rapidly to the detection of other civilisations".

That's because exoplanets in that plane would be able to see Earth passing in front of the Sun and dimming its light.

Such transits reveal all sorts of information about the transiting planets, including their radius, density and composition. They also shed light on the planet's atmosphere - so alien astronomers studying the Earth's spectrum could find indicators of life in our atmospheric oxygen, for example.

Henry and his colleagues hope to search the ecliptic for these civilisations with the Allen Telescope Array, a set of dozens of antennae in Hat Creek, California, US.

All of this begs the question - what kind of technology would alien astronomers in the ecliptic need to glean information from Earth transits?

Greg Laughlin, an astronomer and extrasolar planet hunter at the University of California, Santa Cruz, says it depends how distant the other planet is.

If we're lucky enough to have an advanced civilisation trying to communicate with us within 50 light years, its inhabitants could see the Earth as a bluish dot if they had an 8-metre space-based telescope with a good coronagraph. A set of space-based infrared telescopes would enable them to detect ozone and water vapour in our atmosphere.

That kind of technology is not so far-fetched. These are the underlying concepts behind NASA's Terrestrial Planet Finder missions, which would allow us to attempt this process in reverse, helping us to search elsewhere for habitable, Earth-like planets.

But budget woes have delayed TPF indefinitely, so we can only hope any alien astronomers on other worlds have evolved beyond such earthly concerns. source

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