File:GKPersei-MiniSuperNova-20150316.jpg
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[編輯]描述GKPersei-MiniSuperNova-20150316.jpg |
English: "Mini Supernova" Explosion Could Have Big Impact
http://www.nasa.gov/mission_pages/chandra/mini-supernova-explosion-could-have-big-impact.html In Hollywood blockbusters, explosions are often among the stars of the show. In space, explosions of actual stars are a focus for scientists who hope to better understand their births, lives, and deaths and how they interact with their surroundings. Using NASA’s Chandra X-ray Observatory, astronomers have studied one particular explosion that may provide clues to the dynamics of other, much larger stellar eruptions. A team of researchers pointed the telescope at GK Persei, an object that became a sensation in the astronomical world in 1901 when it suddenly appeared as one of the brightest stars in the sky for a few days, before gradually fading away in brightness. Today, astronomers cite GK Persei as an example of a “classical nova,” an outburst produced by a thermonuclear explosion on the surface of a white dwarf star, the dense remnant of a Sun-like star. A nova can occur if the strong gravity of a white dwarf pulls material from its orbiting companion star. If enough material, mostly in the form of hydrogen gas, accumulates on the surface of the white dwarf, nuclear fusion reactions can occur and intensify, culminating into a cosmic-sized hydrogen bomb blast. The outer layers of the white dwarf are blown away, producing a nova outburst that can be observed for a period of months to years as the material expands into space. Classical novas can be considered to be “miniature” versions of supernova explosions. Supernovas signal the destruction of an entire star and can be so bright that they outshine the whole galaxy where they are found. Supernovas are extremely important for cosmic ecology because they inject huge amounts of energy into the interstellar gas, and are responsible for dispersing elements such as iron, calcium and oxygen into space where they may be incorporated into future generations of stars and planets. Although the remnants of supernovas are much more massive and energetic than classical novas, some of the fundamental physics is the same. Both involve an explosion and creation of a shock wave that travels at supersonic speeds through the surrounding gas. The more modest energies and masses associated with classical novas means that the remnants evolve more quickly. This, plus the much higher frequency of their occurrence compared to supenovas, makes classical novas important targets for studying cosmic explosions. Chandra first observed GK Persei in February 2000 and then again in November 2013. This 13-year baseline provides astronomers with enough time to notice important differences in the X-ray emission and its properties. This new image of GK Persei contains X-rays from Chandra (blue), optical data from NASA’s Hubble Space Telescope (yellow), and radio data from the National Science Foundation’s Very Large Array (pink). The X-ray data show hot gas and the radio data show emission from electrons that have been accelerated to high energies by the nova shock wave. The optical data reveal clumps of material that were ejected in the explosion. The nature of the point-like source on the lower left is unknown. Over the years that the Chandra data span, the nova debris expanded at a speed of about 700,000 miles per hour. This translates to the blast wave moving about 90 billion miles during that period. One intriguing discovery illustrates how the study of nova remnants can provide important clues about the environment of the explosion. The X-ray luminosity of the GK Persei remnant decreased by about 40% over the 13 years between the Chandra observations, whereas the temperature of the gas in the remnant has essentially remained constant, at about one million degrees Celsius. As the shock wave expanded and heated an increasing amount of matter, the temperature behind the wave of energy should have decreased. The observed fading and constant temperature suggests that the wave of energy has swept up a negligible amount of gas in the environment around the star over the past 13 years. This suggests that the wave must currently be expanding into a region of much lower density than before, giving clues to stellar neighborhood in which GK Persei resides. A paper describing these results appeared in the March 10th issue of The Astrophysical Journal. The authors were Dai Takei (RIKEN, Spring-8 Center Japan), Jeremy Drake (Smithsonian Astrophysical Observatory), Hiroya Yamaguichi (Goddard Space Flight Center), Patrick Slane (Smithsonian Astrophysical Observatory), Yasunobu Uchimaya (Rikkyo University, Japan), Satoru Katsuda (Japanese Aerospace Exploration Agency). NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. |
日期 | (release date) |
來源 | http://www.nasa.gov/sites/default/files/thumbnails/image/gkper.jpg |
作者 | X-ray: NASA/CXC/RIKEN/D.Takei et al; Optical: NASA/STScI; Radio: NRAO/VLA |
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[編輯]- Chandra component:
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- Hubble component:
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This file is in the public domain because it was created by NASA and ESA. NASA Hubble material (and ESA Hubble material prior to 2009) is copyright-free and may be freely used as in the public domain without fee, on the condition that only NASA, STScI, and/or ESA is credited as the source of the material. This license does not apply if ESA material created after 2008 or source material from other organizations is in use. The material was created for NASA by Space Telescope Science Institute under Contract NAS5-26555, or for ESA by the Hubble European Space Agency Information Centre. Copyright statement at hubblesite.org or 2008 copyright statement at spacetelescope.org. For material created by the European Space Agency on the spacetelescope.org site since 2009, use the {{ESA-Hubble}} tag. |
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All images and videos released by NRAO on their website are copyright protected on behalf of the National Radio Astronomy Observatory (NRAO), Associated Universities, Inc. (AUI), and the National Science Foundation (NSF), and are licensed for use under the Creative Commons Attribution 3.0 Unported license (https://creativecommons.org/licenses/by/3.0/) in accordance with the conditions below. See the NRAO Image Use Policy for complete information.
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目前 | 2015年3月17日 (二) 13:07 | 3,600 × 2,802(3.24 MB) | Drbogdan(留言 | 貢獻) | User created page with UploadWizard |
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作者 | Chandra X-ray Observatory Center |
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來源 | Chandra X-ray Observatory |
使用條款 | |
寬度 | 3,600 px |
高度 | 2,802 px |
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壓縮方式 | LZW |
像素合成 | RGB |
方位 | 標準 |
像素數量 | 3 |
水平解析度 | 300 dpi |
垂直解析度 | 300 dpi |
資料排列 | 矮胖格式 |
使用軟體 | Adobe Photoshop CC 2014 (Macintosh) |
檔案修改日期時間 | 2015年3月13日 (五) 12:38 |
Exif 版本 | 2.21 |
色彩空間 | sRGB |
數位化的日期時間 | 2015年2月3日 (二) 12:56 |
詮釋資料最後修改日期 | 2015年3月13日 (五) 07:38 |
評分 (共 5 分) | 0 |
原始文件唯一識別碼 | 6BEEEDC866C337F592F46C3EF006ACCE |
版權狀態 | 版權狀態不明 |
聯絡資訊 | cxcpub@cfa.harvard.edu
60 Garden St. Cambridge, MA, 02138 USA |
IIM 版本 | 4 |