| Tweet |
5がつ29日付、CNNより。
5月28日、ハワイのホノルルで｢アメリカ天文学会」が開催された。
その結果について、カリフォルニア大学バークレー校の天文学者、Geoffrey Marcy 教授がCNNの電話インタビューで答えた内容の要約は下記の通り。
・我々の住んでいる太陽系の外側に、28個の他の軌道をまわっている惑星をすでに発見している
・これらの発見されている４つのシステム(我々の太陽系と同じような太陽系）もそれぞれ複数の惑星を有している
・我々の太陽系と同じようなものは無数といっていいほど宇宙には存在する
・我々の地球のような星は宇宙では珍しくない
http://edition.cnn.com/2007/TECH/space/05/29/space.exoplanets.reut/index.html
Planet-hunters find bonanza of new solar systems
POSTED: 1656 GMT (0056 HKT), May 29, 2007
Story Highlights
• 28 new planets found outside our solar system in the past year
• Scientists: There could be billions of habitable planets out there
• Four of the solar systems have multiple planets
• "Our home is not a rarity in the universe" says astronomer Geoffrey Marcy
WASHINGTON (Reuters) -- Planet-seekers who have spotted 28 new planets orbiting other stars in the past year say Earth's solar system is far from unique and there could be billions of habitable planets.
The most recent planet discoveries bring the number of known exoplanets -- planets outside our solar system -- to 236, the researchers told a meeting of the American Astronomical Society in Honolulu Monday.
"We are beginning to see that our home is not a rarity in the universe," said Geoffrey Marcy, a professor of astronomy at the University of California Berkeley, who led the team.
"We are easily able to detect giant planets like Jupiter and Saturn around other stars. Most orbit far from the star like our own Jupiter and Saturn orbit from the sun," Marcy said in a telephone interview.
"It's a common structure among planetary systems."
New techniques allow astronomers to detect planets that are not enormous although Earth-sized objects cannot yet be seen, said the researchers.
Four of the systems also have multiple planets, like Earth's own with its sun, eight planets (Pluto was demoted from planet status) and smaller orbiting objects.
"We are finding that most stars have not just one planet but when we find one there is a second or a third or a fourth," Marcy said.
"The ... attribute which really has us the most excited is this new planet which we found three years ago," Marcy said. The Neptune-like planet orbiting the star Gliese 436 has intrigued scientists because it appears to be covered with water -- albeit rock-hard, hot water in a most un-Earthlike chemical state because of the intense pressures on the planet.
Earlier this month, Swiss and Belgian researchers imaged the star as this planet crossed between it and the Earth. The tiny change in the star's light gave them the planet's diameter and density.
"From the density of two grams per cubic centimeter -- twice that of water -- it must be 50 percent rock and about 50 percent water, with perhaps small amounts of hydrogen and helium," Marcy said.
"Now we are very sure it has a rocky core and this giant thick envelope of water," he added.
"This is why we are jumping out of our clothes. It is the first time we have determined the structure of one of these extrasolar planets. It is rocky like Earth but it has a lot of water which is the essential ingredient for life."
This is almost certainly happening over and over again, Marcy said. Scientists had theorized this for decades but now the hard evidence is starting to pour in.
"Our Milky Way galaxy has 200 billion stars. I would estimate that 10 percent of them, perhaps, have planets that are habitable," Marcy said.
"There are hundreds of billions of galaxies, all of which are more or less like our Milky Way Galaxy, which is tens of billions of planets like our own."
There is one unusual property to our solar system: the nearly circular orbits of the planets, which gives a consistent dose of radiation from the Sun.
Other solar systems seen so far are not usually like this. "Most of the planets are not in circular orbits around the host star but in elongated ones called elliptical orbits," Marcy said.
"We enjoy nearly constant temperatures throughout the year," he added. "If the Earth got too close to the sun, the Earth would heat up, the water would boil off and that would be bad." Too far, and it would freeze.
"An elongated orbit could not sustain life," Marcy said.
Copyright 2007 Reuters. All rights reserved.This material may not be published, broadcast, rewritten, or redistributed.
▲このページのＴＯＰへ HOME > 環境・エネルギー・天文板2掲示板
フォローアップ:
投稿コメント全ログ コメント即時配信 スレ建て依頼 削除コメント確認方法
題名には必ず「阿修羅さんへ」と記述してください。
掲示板,ＭＬを含むこのサイトすべての
一切の引用、転載、リンクを許可いたします。確認メールは不要です。
引用元リンクを表示してください。