Stars That Go Out with a Bang

When a star becomes a white dwarf-an old, extremely dense star that would have once had a mass similar to our own sun's-the eventful part of its life is over.
dwarf: (特に、頭が大きく手足が短い)小びと、(おとぎ話に出てくる)醜い小びと、特別に小さい動物、矮性(わいせい)植物、盆栽(ぼんさい)

It releases what heat and light it has left over billions of years, slowly cooling until it no longer shines.
leave over: 残す、余す、繰り延べる、延期する

Some white dwarfs, however, are not content with this ending.
white dwarf: 白色矮星(わいせい)

If a white dwarf exists in a two-star system with a companion, it can avert its fate and go out with a bang, not a whimper.
content with: 満足して、満足する、甘んじる
avert: そむける、そらす、避ける、防ぐ
go out with: 付き合う、付合う、つき合う、[通例 go outing 形で] 〔異性と〕出歩く、つき合う

It does so by causing a particular type of stellar explosion called a type Ia supernova.
whimper: クンクン鳴く、すすり泣きする、しくしく泣く、鼻声になる、ぶつぶつ不平を言う
stellar: 星の、星から成る、(形が)星のような、星形の、主要な、傑出した、花形の

A type Ia supernova starts when the white dwarf drags material from its companion onto itself.

It grows and grows until it cannot get any bigger.

At this point, it implodes, then rebounds and explodes in a supernova bright enough to outshine whole galaxies.
implode: 内側に破裂する、内破する
outshine: よりよく光る、より光が強い、より優秀である、(…に)まさる

The companion star from which the white dwarf steals matter is instrumental in this dramatic event.
instrumental: (…の)手段になって、助けになって、器械の、楽器(用)の

Its identity, however, has long been a mystery.

Theoretical models say the companion star can be anything from a red giant to a main sequence star like the sun to another white dwarf.

Astronomers have been able to narrow the range of possible companions for a type Ia supernova spotted late last year.
spot: (特定の)場所、地点、(感情・気持ちなどの)点、所、個所、(周囲と違った色の小さな)ぶち、斑点(はんてん)、まだら、ほくろ、発疹(はつしん)

A telescope belonging to the Palomar Transient Factory ( PTF ) survey in Pasadena, Calif.

, spotted a bright spot at one minute before 9 P.M. on August 24. The new supernova, known as supernova 2011fe, won Palomar astronomers the rec\xadord for the earliest ever detection of a type Ia supernova: just 11 hours after its initial explosion.

Last December researchers published two papers in Nature analyzing observations of supernova 2011fe.

One paper, with lead author Peter Nugent of Lawrence Berkeley National Laboratory and PTF, found that the companion star was probably a main sequence star.
main sequence star: 主系列星

The other work, spearheaded by Weidong Li of the University of California, Berkeley, rules out a red giant.
spearhead: 槍(やり)の穂先、先鋒(せんぽう)、先頭、一番槍(を務める人)

Li used observations from the Keck II telescope in Hawaii to pinpoint the location of the supernova, then analyzed Hubble Space Telescope images from before the supernova explosion to look for clues about the pair of stars from which it was born.
rule out: (規定などによって)(…を)除外する、排する、無視する、(…を)不可能にする

Supernova 2011fe is the nearest type Ia supernova to be discovered in many years and, because instrumentation has moved on considerably in that time, will be the most studied supernova in history.
move on: どんどん進む、転職する、移る、過ぎていく

These two papers are just the beginning.

\xa0This article was published in print as Stars That Go Out with a Bang.

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