A New Class of Supernova
by Sid Perkins on 26 March 2013, 2:00 PM 胡德良 译
| Some of the most powerful explosions in the universe just got a bit more varied. Astronomers have already categorized two broad groups of supernovae: type Ia supernovae presumed to result from the complete disruption of a white dwarf star, and the type II, Ib, and Ic supernovae thought to explode when the core of giant star collapses. Now, they say that a type of exploding star first thought to be an unusual sort of type Ia supernova is actually a different class of supernova altogether. Explosions of these stars, dubbed type Iax, release somewhere between 1% and 50% the energy of a type Ia supernova, and there are hints that in many cases a remnant of the star may survive the initial outburst. Like type Ia supernovae (but unlike the smaller, garden-variety exploding stars called novae), spectra of type Iax stars don't include any signs of hydrogen. Most of the 25 stars share more than 25 different characteristics—a sign that the stars probably not only look alike but are physically similar, the researchers report online and in a forthcoming issue of The Astrophysical Journal. Type Iax supernovae most likely form in binary star systems when a superdense, carbon- and oxygen-rich white dwarf star (center of disk at left) robs material from its helium-rich partner, eventually accumulating enough mass on its surface to trigger an explosion. Astronomers likely have discovered so few type Iax supernovae only because they are faint, not because they are rare: The team estimates that for every 100 type Ia supernovae explosions that occur, there are about 31 type Iax supernovae. |
宇宙中一些最具威力的爆炸变得有点更加多样化了。天文学家们已经将超新星分为两大类：Ia型超新星——这种超新星被认为是白矮星完全瓦解后形成的；II型、Ib型和Ic型超新星——当巨星恒星的核心塌缩而发生爆炸时，形成这些类型的超新星。天文学家们称，有一种爆炸的恒星，起初被认为是非同寻常的Ia型超新星，实际上是一种完全不同的超新星。这些恒星被称为Iax型超新星，其爆炸释放的能量为Ia型超新星的1%至50%，有迹象表明，这种恒星的残骸在很多情况下可以从最初的爆炸中存留下来。跟Ia型超新星一样，Iax型超新星光谱中没有氢的迹象，这一点与较小的、被称为“新星”的普通恒星爆炸不同。根据研究人员的在线报道，以及在即将出版的一期《天体物理学杂志》中的报道：在25颗Ia型超新星中，多数超新星共同拥有不少于25个各种各样的特征，这表明这些恒星很可能不仅外观相同，而且自然规律也相同。Iax型超新星很可能形成于双星系统中：当富含碳氢的超密白矮星（左部圆盘中心）从富含氦的伴星那里抢夺物质材料之后，最终在其表面积累了足够的物质，引起爆炸。天文学家们很可能没有发现过Iax型超新星，并不是因为这类超新星很罕见，而仅仅是因为它们很暗淡。据研究小组估计，在每一百颗Ia型超新星爆炸的情况中，大约有31颗Iax型超新星。 |
译自：美国《科学》杂志网站（26 March 2013, 2:00 PM）
原著：Sid Perkins
