Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

July 23, 1998

X-Ray Pulsar
Picture Credit: W. Feimer (Allied Signal), GSFC, NASA

Explanation: This dramatic artist's vision shows a city-sized neutron star centered in a disk of hot plasma drawn from its enfeebled red companion star. Ravenously accreting material from the disk, the neutron star spins faster and faster emitting powerful particle beams and pulses of X-rays as it rotates 400 times a second. Could such a bizarre and inhospitable star system really exist in our Universe? Based on data from the orbiting Rossi X-Ray Timing Explorer (RXTE) satellite, research teams have recently announced a discovery which fits this exotic scenario well - a "millisecond" X-ray pulsar. The newly detected celestial X-ray beacon has the unassuming catalog designation of SAX J1808.4-3658 and is located a comforting 12,000 light years away in the constellation Sagittarius. Its X-ray pulses offer evidence of rapid, accretion powered rotation and provide a much sought after connection between known types of radio and X-ray pulsars and the evolution and ultimate demise of binary star systems.

這幅戲劇性的藝術家圖示,呈現一顆城市規模的中子星,座落在它從泛紅伴星吸積的熾熱電漿盤之中心。 中子星瘋狂的從吸積盤吸收物質,造成它的旋轉速度愈來愈快,在每秒旋轉400次的同時,也輻射出強大的粒子束和X射線脈衝。 在我們的宇宙中是否真的有這麼怪異且嚴酷的恒星系統? 分析來自軌道上的羅西X射線定時探測衛星(RXTE)的資料,研究小組最近宣佈發現了一例符合這種奇異場景的 "毫秒級 "X射線脈衝星。 這個新剛探測到的天體X射線信標的編錄號為SAX J1808.4-3658,令人欣慰的是它位在人馬座方向約12000光年遠之處。 它的X射線脈衝證實吸積驅動的高速系統之存在,並對已知類型的無線電和X射線脈衝星、及雙星系統演化和最終消亡之間的聯結,提供了追尋已久的跡證。

Tomorrow's picture: Alan B. Shepard Jr. 1923-1998

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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (USRA)
NASA Technical Rep.: Jay Norris. Specific rights apply.
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&: Michigan Tech. U.