Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Scorpius X-1
open-in-new
<h2 id="discovery-and-early-study">Discovery and early study</h2> <p>The possible existence of cosmic soft X-rays was first proposed by <a href="/facts/Bruno_Rossi/prKj84c6">Bruno Rossi</a>, MIT professor and board chairman of <a href="/facts/American_Science_and_Engineering/bdT6tdu2">American Science and Engineering</a> in <a href="/facts/Cambridge,_Massachusetts/k9UMIJ7U">Cambridge, Massachusetts</a> 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. </p><p>Subsequently, Scorpius X-1 was discovered in 1962 by a team, under <a href="/facts/Riccardo_Giacconi/DsmSXleR">Riccardo Giacconi</a>, who launched an <a href="/facts/Aerobee/2Y6J8k7v">Aerobee</a> 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 <a href="/facts/Solar_System/QIcLSazQ">Solar System</a>. The <a href="/facts/Angular_resolution/wJarPBWF">angular resolution</a> 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 <a href="/facts/Galactic_Center/TI4MwWwM">Galactic Center</a>, but it was eventually realized that it lies in the constellation Scorpius.<a class="footnote-ref" id="fnref:3" href="#fn:3"><sup>3</sup></a> As the first discovered X-ray source in Scorpius, it received the designation Scorpius X-1. </p><p>The <a href="/facts/Aerobee/2Y6J8k7v">Aerobee</a> 150 rocket launched on June 12, 1962, detected the first X-rays from another celestial source (Scorpius X-1) at J1950 <a href="/facts/Right_ascension/z4CEsTFu">RA</a> 16h 15m <a href="/facts/Declination/5X4S4k9u">Dec</a> −15.2°.<a class="footnote-ref" id="fnref:4" href="#fn:4"><sup>4</sup></a> Sco X-1 is a <a href="/facts/LMXB/fpvJvImP">LMXB</a> in which the visual counterpart is V818 Scorpii. </p><p>Although the above reference indicates the rocket launch was on June 12, 1962, other sources indicate the actual launch was at 06:59:00 UTC on June 19, 1962.<a class="footnote-ref" id="fnref:5" href="#fn:5"><sup>5</sup></a><a class="footnote-ref" id="fnref:6" href="#fn:6"><sup>6</sup></a> </p><p>Historical footnote: "The instrumentation had been designed for an attempt to observe X-rays from the moon and was not equipped with collimation to restrict the field of view narrowly. As a result, the signal was very broad, and accurate definition of the size and position of the source was not possible. A similar experiment was repeated in October 1962 when the Galactic Center was below the horizon and the strong source was not present. A third attempt, in June 1963, verified the results of the June 1962 flight."<a class="footnote-ref" id="fnref:7" href="#fn:7"><sup>7</sup></a> The <a href="/facts/Galactic_Center/TI4MwWwM">Galactic Center</a> is < 20° <a href="/facts/Right_ascension/z4CEsTFu">RA</a> and < 20° <a href="/facts/Declination/5X4S4k9u">Dec</a> from Sco X-1, the two X-ray sources are separated by ~20° of arc and may not have been resolvable in the June 1962 flight.<a class="footnote-ref" id="fnref:8" href="#fn:8"><sup>8</sup></a> </p><p>Scorpius XR-1 has been observed at J1950 <a href="/facts/Right_ascension/z4CEsTFu">RA</a> 16h 15m <a href="/facts/Declination/5X4S4k9u">Dec</a> −15.2°.<a class="footnote-ref" id="fnref:9" href="#fn:9"><sup>9</sup></a> </p><p>In 1967 (before the discovery of <a href="/facts/Pulsar/f8c7S5LQ">pulsars</a>), <a href="/facts/Iosif_Shklovsky/eWbTNN6J">Iosif Shklovsky</a> examined X-ray and optical observations of Scorpius X-1 and correctly concluded that the radiation comes from a <a href="/facts/Neutron_star/4enfoxBA">neutron star</a> accreting matter from a companion.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> </p> <h2 id="characteristics">Characteristics</h2> <p>Its X-ray output is 2.3×1031 <a href="/facts/Watt/VK8oqRrm">W</a>, about 60,000 times the total luminosity of the Sun.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> Scorpius X-1 shows regular variations of up to 1 <a href="/facts/Apparent_magnitude/7pCTF1Me">magnitude</a> in its intensity, with a period of around 18.9 hours. The source varies irregularly in optical <a href="/facts/Wavelength/kcJU0ymz">wavelengths</a> as well, but these changes are not correlated with the X-ray variations.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> Scorpius X-1 itself is a <a href="/facts/Neutron_star/4enfoxBA">neutron star</a> whose intense gravity draws material off its companion into an <a href="/facts/Accretion_disk/8zJXshat">accretion disk</a>, 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 <a href="/facts/Eddington_limit/RWeams0T">Eddington limit</a>.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> </p><p>This system is classified as a <a href="/facts/Low-mass_X-ray_binary/fpvJvImP">low-mass X-ray binary</a>; the neutron star is roughly 1.4 <a href="/facts/Solar_masses/j6Auhku8">solar masses</a>, while the donor star is only 0.42 solar masses.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a> The two stars were probably not born together; recent research suggests that the binary may have been formed by a close encounter inside a <a href="/facts/Globular_cluster/FL0EERJU">globular cluster</a>.<a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a> </p> <h2 id="see-also">See also</h2> <ul><li><a href="/facts/List_of_X-ray_pulsars/HAIRQTHu">List of X-ray pulsars</a></li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Giacconi, R.; Gursky, H.; Paolini, F.R.; Rossi, B.B. (1962). "Evidence for X-rays from sources outside the solar system". Phys. Rev. Lett. 9 (11): 439–443. Bibcode:1962PhRvL...9..439G. doi:10.1103/PhysRevLett.9.439. <a href="https://doi.org/10.1103%2FPhysRevLett.9.439" target="_blank">https://doi.org/10.1103%2FPhysRevLett.9.439</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>Shklovskii, Iosif S. (1978). Stars: Their Birth, Life, and Death. W.H. Freeman. ISBN 978-0-7167-0024-1. <a href="978-0-7167-0024-1" target="_blank">978-0-7167-0024-1</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Shklovskii, Iosif S. (1978). Stars: Their Birth, Life, and Death. W.H. Freeman. ISBN 978-0-7167-0024-1. <a href="978-0-7167-0024-1" target="_blank">978-0-7167-0024-1</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Giacconi R (August 2003). "Nobel Lecture: The dawn of X-ray astronomy". Rev. Mod. Phys. 75 (3): 995–1010. Bibcode:2003RvMP...75..995G. doi:10.1103/RevModPhys.75.995. <a href="https://doi.org/10.1103%2FRevModPhys.75.995" target="_blank">https://doi.org/10.1103%2FRevModPhys.75.995</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Drake SA (September 2006). "A Brief History of High-Energy Astronomy: 1960–1964". <a href="https://heasarc.gsfc.nasa.gov/docs/heasarc/headates/1960.html" target="_blank">https://heasarc.gsfc.nasa.gov/docs/heasarc/headates/1960.html</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>"Chronology—Quarter 2 1962". Archived from the original on 2010-01-18. <a href="https://web.archive.org/web/20100118132318/http://astronautix.com/chrono/19622.htm" target="_blank">https://web.archive.org/web/20100118132318/http://astronautix.com/chrono/19622.htm</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Bowyer S; Byram ET; Chubb TA; Friedman H (1965). Steinberg JL (ed.). "Observational results of X-ray astronomy". Astronomical Observations from Space Vehicles, Proceedings from Symposium No. 23 Held in Liège, Belgium, 17 to 20 August 1964. 23. International Astronomical Union: 227–39. Bibcode:1965IAUS...23..227B. <a href="/wiki/International_Astronomical_Union" target="_blank">/wiki/International_Astronomical_Union</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Bowyer S; Byram ET; Chubb TA; Friedman H (1965). Steinberg JL (ed.). "Observational results of X-ray astronomy". Astronomical Observations from Space Vehicles, Proceedings from Symposium No. 23 Held in Liège, Belgium, 17 to 20 August 1964. 23. International Astronomical Union: 227–39. Bibcode:1965IAUS...23..227B. <a href="/wiki/International_Astronomical_Union" target="_blank">/wiki/International_Astronomical_Union</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Bowyer S; Byram ET; Chubb TA; Friedman H (1965). Steinberg JL (ed.). "Observational results of X-ray astronomy". Astronomical Observations from Space Vehicles, Proceedings from Symposium No. 23 Held in Liège, Belgium, 17 to 20 August 1964. 23. International Astronomical Union: 227–39. Bibcode:1965IAUS...23..227B. <a href="/wiki/International_Astronomical_Union" target="_blank">/wiki/International_Astronomical_Union</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>Shklovsky, I.S. (April 1967). "On the Nature of the Source of X-Ray Emission of SCO XR-1". Astrophys. J. 148 (1): L1 – L4. Bibcode:1967ApJ...148L...1S. doi:10.1086/180001. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Bradshaw, C.F.; Fomalont, E.B.; Geldzahler, B.J. (1999). "High-Resolution Parallax measurements of Scorpius X-1". The Astrophysical Journal. 512 (2): L121 – L124. Bibcode:1999ApJ...512L.121B. doi:10.1086/311889. <a href="https://doi.org/10.1086%2F311889" target="_blank">https://doi.org/10.1086%2F311889</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Shklovskii, Iosif S. (1978). Stars: Their Birth, Life, and Death. W.H. Freeman. ISBN 978-0-7167-0024-1. <a href="978-0-7167-0024-1" target="_blank">978-0-7167-0024-1</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Bradshaw, C.F.; Fomalont, E.B.; Geldzahler, B.J. (1999). "High-Resolution Parallax measurements of Scorpius X-1". The Astrophysical Journal. 512 (2): L121 – L124. Bibcode:1999ApJ...512L.121B. doi:10.1086/311889. <a href="https://doi.org/10.1086%2F311889" target="_blank">https://doi.org/10.1086%2F311889</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Steeghs, D.; Casares, J. (2002). "The Mass Donor of Scorpius X-1 Revealed". The Astrophysical Journal. 568 (1): 273–278. arXiv:astro-ph/0107343. Bibcode:2002ApJ...568..273S. doi:10.1086/339224. S2CID 14136652. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Mirabel, I. F.; Rodrogues, I. (2003). "The origin of Scorpius X-1". Astronomy and Astrophysics. 398 (3): L25 – L28. arXiv:astro-ph/0301580. Bibcode:2003A&A...398L..25M. doi:10.1051/0004-6361:20021767. S2CID 2585509. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> </ol>