Research press release


Nature Physics

Laser recreates conditions near a black hole

レーザーを用いて、ブラックホールの近傍で作られるものに似た、物質の極端な状態を生成できることが、Nature Physics(電子版)に報告される。このような状態を実験室で再現できれば、ブラックホールやほかの同じくらい重い天体の近くで起こる過程の研究だけでなく、このような天体の天文測定結果のよりよい解釈がずっと容易になる。


光電離プラズマを生成するために、藤岡慎介たちは、300ギガワットのレーザーを用いて、薄いシリコン箔を爆縮させた。その結果生じたプラズマから放射されるX線スペクトルの形状が、チャンドラX線天文衛星によって測定された、ブラックホールの候補である連星Cygnus X-3や中性子星であるVela X-1の放射スペクトルと極めて似ていることがわかった。この結果から、これらのスペクトルの特定部分の起源に関する一般的な解釈が間違っている可能性があることが示唆され、このような天体系のモデルの改善に役立つかもしれない。

Lasers can be used to generate extreme states of matter similar to those produced in the vicinity of a black hole, reports a study published online this week in Nature Physics. The ability to recreate these states in the laboratory makes it much easer to study the processes that occur near black holes and other similarly massive astrophysical objects, as well as to better interpret the astronomical measurements of these objects.

Most plasmas, including those that occur in the Sun, are composed of gas atoms that have been ionized ― or electrically charged ― by collisions with electrons and hot gas atoms. The ionization of plasmas surrounding a black hole, however, is driven by the immense flux of photons generated as matter is sucked into the black hole. These 'photoionized' plasmas produce a characteristic X-ray spectrum that can is detected by satellites orbiting the Earth. But photoionized plasmas are much more difficult to produce than conventional plasmas.

To produce a photoionized plasma, Shinsuke Fujioka and colleagues use a 300 gigawatt laser to cause the implosion of a thin silicon foil. The researchers found that the shape of the X-ray spectrum from the resulting plasma was remarkably similar to those emanating from the binary stars Cygnus X-3, a black-hole candidate, and Vela X-1, a neutron star, as measured by the Chandra X-ray satellite. The results suggest that the commonly held understanding of the origin of certain parts of these spectra might be wrong a fact that could help astrophysicists improve their models of these and similar astrophysical systems.

doi: 10.1038/nphys1402


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