Top Qs
Timeline
Chat
Perspective
Scorpius X-1
Astronomical X-ray source From Wikipedia, the free encyclopedia
Remove ads
Scorpius X-1 is a low-mass X-ray binary located roughly 9,000 light years away in the constellation Scorpius. Scorpius X-1 was the first extrasolar X-ray source discovered, and, aside from the Sun, it is the strongest apparent non-transient source of X-rays in the sky.[4]
Remove ads
Discovery and early study
Summarize
Perspective
The possible existence of cosmic soft X-rays was first proposed by Bruno Rossi, MIT professor and board chairman of American Science and Engineering in Cambridge, Massachusetts to Martin Annis, president of AS&E. Following his urging, the company obtained a contract from the United States Air Force to explore the lunar surface prior to the launch of astronauts to the Moon, and incidentally to perhaps see galactic sources of X-rays.
Subsequently, Scorpius X-1 was discovered in 1962 by a team, under Riccardo Giacconi, who launched an Aerobee 150 sounding rocket carrying a highly sensitive soft X-ray detector designed by Frank Paolini. The rocket trajectory was slightly off course but still detected a significant emission of soft X-rays that were not coming from the Moon. Thus fortuitously, and as first pointed out by Frank Paolini, Scorpius X-1 became the first X-ray source discovered outside the Solar System. The angular resolution of the detector did not initially allow the position of Scorpius X-1 to be accurately determined. This led to suggestions that the source might be located near the Galactic Center, but it was eventually realized that it lies in the constellation Scorpius.[5] As the first discovered X-ray source in Scorpius, it received the designation Scorpius X-1.
The Aerobee 150 rocket launched on June 12, 1962[6] or June 19, 1962,[7][8] detected the first X-rays from another celestial source (Scorpius X-1) at J1950 RA 16h 15m Dec −15.2°.[6] The rocket was designed to observe X-rays from the moon rather than smaller, extrasolar sources, and therefore was unable to accurately retrieve the position and strength of the X-ray signal. The source was estimated to be at J1950 coordinates RA 16h 15m Dec −15.2°.[9]
In 1967, before the discovery of pulsars, Iosif Shklovsky examined X-ray and optical observations of Scorpius X-1 and correctly concluded that the radiation comes from a neutron star accreting matter from a companion.[10]
Remove ads
Characteristics
Summarize
Perspective
Its X-ray output is 2.3×1031 W, about 60,000 times the total luminosity of the Sun.[12] Scorpius X-1 shows regular variations of up to 1 magnitude in its intensity, with a period of around 18.9 hours. The source varies irregularly in optical wavelengths as well, but these changes are not correlated with the X-ray variations.[5] Scorpius X-1 itself is a neutron star whose intense gravity draws material off its companion into an accretion disk, where it ultimately falls onto the surface, releasing a tremendous amount of energy. As this stellar material accelerates in Scorpius X-1's gravitational field, X-rays are emitted. The measured luminosity for Scorpius X-1 is consistent with a neutron star which is accreting matter at its Eddington limit.[12]
This system is classified as a low-mass X-ray binary; the neutron star is roughly 1.4 solar masses, while the donor star is only 0.42 solar masses.[13] The origin of the system is a matter of debate. There is evidence that the two stars were not born together; studies based on the reconstruction of the orbit of Sco X-1 suggest that the binary may have been formed by a close encounter inside a globular cluster. However, it is not clear how to reconcile this formation scenario with the circularisation of the binary's orbit.[14]
Remove ads
See also
References
Wikiwand - on
Seamless Wikipedia browsing. On steroids.
Remove ads