https://www.scientificamerican.com/index.cfm/_api/render/file/?method=inline&fileID=84F6F339-6F4C-4A03-A8F86DEDDAAEE722
SCIENTIFIC AMERICAN June 2009 Volume 300, Issue 6 UnlikelySuns Reveal Improbable Planets Astronomers are findingplanets where there were not supposed to be any By Micheal W. Wernerand Michael A. Jura
有一篇第一段说说科学家通过一种方法可以观测一个什么“PR-数字”的星，那个星有三个卫星绕着转。然后说这个星的形成，生词较多，不是很理解，不说了以免误导大家。 ．【PXCR 2317】(编号是我瞎编的,原文的编号不记得了,没有实际含义的~)
(1)PARA1,科学家在研究一个星体PXCR 2317(后面用P2代替),其星球直径只有10 kilometer(我没记错的话) ,周围有很多更小的星体影响着P2的position
(2)para2,一种说法是说P2是远古一个大星体的explosion的碎片.但是这种说法有问题,因为大星体本身的直径就比太阳系的直径更大(imply:爆炸之后不可能比这个距离更小,也不可能合成P2.这一点有出考题,LZ觉得应该是对应这里.).所以科学家的结论是P2形成是在这个explosion之前.
(3)para3,提出了P2形成的另一种解释.说P2的构成是因为collapse because of theweight.具体的不记得了
Astronomers have always suspected that planetsmight orbit stars other than our sun. Weimagined, though, that we would fi nd systemsmuch like our own solar system, centered on astar much like the sun. Yet when a fl ood of discoveriesbegan 15 years ago, it was apparent rightaway that extrasolar planetary systems can differdramatically from our solar system. The fi rstexample was the sunlike star 51 Pegasi, found tohave a planet more massive than Jupiter on an orbitsmaller than that of Mercury. As instrumentsbecame more sensitive, they found ever strangerinstances. The sunlike star HD 40307 hosts threeplanets with masses between four and 10 Earth masses, all on orbits less than half the size ofMercury’s. The sunlike star 55 Cancri A has nofewer than fi ve planets, with masses rangingfrom 10 and 1,000 Earth masses and orbital radiiranging from one tenth that of Mercury toabout that of Jupiter. Planetary systems imaginedin science fi ction scarce ly compare.
It is sometimes forgotten today, but the fi rstconfi rmed discovery of any extrasolar planets was around a very unsunlikestar: the neutron star PSR 1257+12, an even more extreme type of stellar corpsethan a white dwarf. It packs a mass greater than the sun’s into the size of asmall asteroid, some 20 kilometers across. The event that created this beast,the supernova explosion of a star 20 times the mass of the sun, was moreviolent than the demise of a sunlike star, and it is hard to imagine planetssurviving it. Moreover, the star that exploded probably had a radius largerthan 1 AU (astronomical unit, the Earth-sun distance), which is larger than theorbits of the planets we see today. For both reasons, those planets must haverisen up out of the ashes of the explosion.
Although supernovae typically eject most oftheir debris into interstellar space, a small amount remains gravitationallybound and falls back to form a swirling disk around the stellar remnant. Disksare the birthing grounds of planets. Astronomers think our solar system tookshape when an amorphous interstellar cloud of dust and gas collapsed under itsown weight. The conservation of angular momentum, or spin, kept some of thematerial from simply falling all the way to the newborn sun; instead it settledinto a pancake shape. Within this disk, dust and gas coagulated into planets[see “The Genesis of Planets,” by Douglas N. C. Lin; Scientific American, May2008]. Much the same process could have occurred in the postsupernova fallbackdisk.
Astronomers discovered the system around PSR1257+12 by detecting periodic deviations in the timing of the radio pulses itgives off; such deviations arise because the orbiting planets pull slightly onthe star, periodically shifting its position and thus altering the distance thepulses must travel. Despite intensive searches of other stars’ pulses,observers know of no other comparable system. Another pulsar, PSR B1620–26, hasat least one planet, but it orbits so far from the star that astronomers think itdid not form in a fallback disk but rather was captured gravitationally fromanother star.
In 2006, however, NASA’s Spitzer SpaceTelescope discovered unexpected infrared emission from the neutron star 4U0142+61. The infrared light might arise from the star’s magnetosphere or from acircumstellar disk. This star formed in a supernova explosion about 100,000years ago, and it typically takes about a million years or so for planets toagglomerate, so if the radiation does signal the presence of a disk, thissystem may one day resemble that revolving around PSR 1257+12.
应该不是原文了。 No discuss about giant star.
楼主能回忆一些英文原词吗？
是原文吗？
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发表于 2018-7-8 01:16:45
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