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发表于 2005-11-6 17:41:12
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页面标题翻译:向物理学家提问
翻译页面地址:http://boinc.equn.com/einstein/ask/index.htm
Q:Would so-called solid quark stars that undergo "glitches" produce gravity waves due to the changing moment of inertia? Could detection of this be used to prove or rule out the existence of strange quark stars?
Submitted by Robert from Sunnyvale, California
A:A "glitch" is what radio astronomers call it when they see a pulsar's frequency suddenly jump up a little bit. Most of the time the frequency goes down steadily (and very slowly) because the pulsar is radiating energy and angular momentum in electromagnetic waves (radio, light, etc) and gravitational waves. Glitches can't happen to an all-liquid star, so the observations tell us that part of the star is solid. Basically, something must have cracked and the structure changed abruptly. That something could be the solid part itself, or various interactions between the solid and liquid parts.
Neutron stars should be mostly liquid with a thin solid crust on top. But some pulsars might be dense enough to be made of quarks mingling freely rather than confined into the groups of three we call neutrons. The properties of quark stars are harder to predict than those of neutron stars (which are already tricky). Quark stars are thought to be mostly gas under a thin solid crust, but it's possible they're completely solid.
After the abrupt disturbance of a glitch, the whole star should ring like a bell, and the motion of the matter will produce gravitational waves. The exact kind of ringing could reveal in principle the structure of the star, like what fraction is solid and what it's made of. Unfortunately these signals are too weak to be detected with the present generation of instruments or even the next generation. Also they don't last very long, which hurts the detectability of already weak signals.
But Einstein@Home might detect what comes before the glitch. What cracked might have been a lump in the solid part of the star. If so, it would make gravitational waves as it spins around, day after day. The long duration helps us detect that signal, although we need a lot of computing power to take advantage of it. That's why we ask you folks to join Einstein@Home. That long-lived signal might indicate if the source is a neutron star or something else, since the waves from solid quark stars could be a lot stronger than from neutron stars.
问:一个所谓的固体夸克星体会在受到"短时脉冲波形干扰"后由于瞬间惯性的改变而产生引力波?这一发现能够证明或者排除那些陌生的夸克星体的存在吗?
来自Sunnyvale, California 的Robert提出了这个问题.
答:"短时脉冲波形干扰"一词是当无线电天文学家发现脉冲星的频率突然跳跃而命名的.在大多数情况下,脉冲星在以电磁波(无线电,光等)和重力波的形式释放能量和角动量,所以它的频率会连续的下降(而且非常慢).但"短时脉冲波形干扰"并不发生在全液体的星体上,所以观测的资料使我们了解到只有一部分的星体是固态的.基本上,只要某些部分会爆裂和结构突然变化.那些部分就很可能是固态部分的本身,也可能是固态部分和液态部分互相作用产生的现象.
中子星大部分是液体,在表层只有一层薄薄的固体外壳.但一些脉冲星的密集程度使夸克自由组合更胜于把三个中子限制于一组.况且,夸克星体的变化比(那些已经很复杂的)中子星更难预测.而现今,夸克星体已经被普遍认为是由大量气体组成,表面覆盖着一层薄薄的固态外壳的星体,但也有可能它们是完全固态的.
在"短时脉冲波形干扰"突然干扰之后,整个星体会像铃一样响起振动,它的运动将会产生引力波.从那些精准的振动可以大体上分析出星体的结构,就像某些地方是固态或者说它们的组成是什么.但遗憾的是,这些信号实在太弱了,以至现代的仪器不能准确地测出,甚至下一代的仪器也未必.而且,那些信号不会持续太长,这使得它们更难侦测.
但是Einstein@Home 会在"短时脉冲波形干扰"之前侦测它.那怕是固体部分爆裂出的一块.如果真的是这样,当它旋转时会不断地产生重力波.而长久持续的时间能够是我们侦测出那信号,虽然我们需要利用大量的计算能力才能达到那一点.那就是我们邀请你们参与Einstein@Home的原因.由于从夸克星体发出的信号会比中子星强一点,或许那个久远的信号将会告诉我们它是中子星或是其它什么的.
[ Last edited by applegz on 2005-11-6 at 18:41 ] |
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发表于 2005-11-6 13:22:37