搜索死亡恆星 它擲出致命彗星
Search on for Death Star that throws out deadly comets
Nasa scientists are searching for an invisible 'Death Star' that circles the Sun, which catapults potentially catastrophic comets at the Earth.
美國宇航局的科學家正在搜尋，一粒以太陽繞圈的隱形'死亡恆星'，它有潛質向地球彈射災難性的彗星。
By Richard Alleyne, Science Correspondent
Published: 8:00AM GMT 13 Mar 2010
This diagram shows a brown dwarf in relation to Earth, Jupiter, a low-mass star and the sun. Photo: NASA
這圖顯示一粒棕矮星與地球、木星、低質量恆星和太陽。圖片：NASA
The star, also known as Nemesis, is five times the size of Jupiter and could be to blame for the impact that wiped out the dinosaurs 65 million years ago.
那恆星亦被稱為復仇，是木星5倍的大小，和能被指責為 6500萬年前恐龍滅絕的影響。
The bombardment of icy missiles is being blamed by some scientists for mass extinctions of life that they say happen every 26 million years.
結滿冰的導彈轟炸正被一些科學家指責，為他們說的每26萬年發生的大規模的生命滅絕。
Nemesis is predicted to lie at a distance equal to 25,000 times that of the Earth from the Sun, or a third of a light-year.
復仇被預計躺在一個距離，相當於 25,000倍從太陽至地球，或者三分之一的光年。
Astronomers believe it is of a type called a red or brown dwarf – a "failed star" that has not managed to generate enough energy to burn like the Sun.
天文學家相信它是一種被稱為紅或棕色的矮星 - 一粒“失敗的恆星”沒法產生足夠的能量如太陽般燃燒。
But it should be detectable by a heat-sensitive space telescope called WISE, the Wide-Field Infrared Survey Explorer.
但是它應該能夠用熱感太空望遠鏡稱為WISE探測到，它是寬界紅外線探測望遠鏡。
Launched last year, WISE began surveying the skies in January. It is expected to discover a 1000 brown dwarfs within 25 light-years of the Sun – right on our cosmic doorstep – before its coolant runs out in October.
去年發射的WISE在1月開始調查天空，預計 會發現在太陽內25光年的1,000棕矮星 - 在我們的宇宙門檻 - 在它於10月到期冷卻之前。
The nearest normal star to us is around 4.5 light-year away.
我們的最近正常恆星大約在 4.5光年外。
Our solar system is thought to be surrounded by a vast sphere of icy bodies, twice as far away as Nemesis, called the Oort Cloud.
我們的太陽系被認為是被一個巨大的多冰球體所包圍，復仇的兩倍遙遠，被稱為奧爾特雲。
Some get kicked in towards the planets as comets – giant snowballs of ice, dust and rock – and the suggestion is that the Death Star's gravitational influence is to blame.
The paleontologists David Raup and Jack Sepkoski discovered that, over the last 250 million years, life on Earth has been devastated on a 26-million-year cycle. Comet impacts are suggested as a likely cause for these catastrophes.
A similar impact by an asteroid wiped out the dinosaurs 65 million years ago, a major inquest by scientists concluded last week, though that is not being blamed on Nemesis.
Most stars have one or more companion stars orbiting around each other, which would make the sun's single status unusual.
A major clue to Nemesis's existence is a mysterious dwarf planet called Sedna that was spotted on an elongated 12,000-year-long orbit around the sun.
Mike Brown, who discovered Sedna in 2003, said: "Sedna is a very odd object – it shouldn't be there! It never comes anywhere close to any of the giant planets or the sun. It's way, way out there on this incredibly eccentric orbit.
The only way to get on an eccentric orbit is to have some giant body kick you – so what is out there?"
Professor John Matese, of the University of Louisiana at Lafayette, says most comets in the inner solar system seem to come from the same region of the Oort Cloud – launched by the pull of a companion star to the sun that scatters comets in its wake.
He suggests it is up to five times the size of Jupiter or 7,000 times the size of Earth.
He said: "There is statistically significant evidence that this concentration of comets could be caused by a companion to the Sun."
http://www.telegraph.co.uk/science/space/7429335/Search-on-for-Death-Star-that-throws-out-deadly-comets.html
繞太陽矮星 引彗星撞地球
2010年03月15日
科學家估計，這顆被稱為「報應女神」（Nemesis）的矮星，距離地球約三分之一光年，亦即地球和太陽之間距離的二萬五千倍，體積約為木星的五倍，但實際位置不明。科學家相信太陽系被一層巨大的冰體雲團奧爾特雲（Oort Cloud）包圍，而「報應女神」的引力會令奧爾特雲中的巨型冰塊如彗星般撞向行星。
有古生物學家指地球約每隔二千六百萬年便會遭受浩劫，相信彗星撞擊便是引致這些災難的原因。
http://orientaldaily.on.cc/cnt/china_world/20100315/00180_026.html
復仇女神：死亡之星
Disc: http://www.discuss.com.hk/viewthread.php?tid=11759195&page=2&extra=page%3D1#pid243920184
沒有留言:
發佈留言