Epoch J2000 Equinox J2000
|Right ascension||06h 11m 49.0763s|
|Declination||+22° 49′ 32.686″|
|Apparent magnitude (V)||11.51|
|Proper motion (μ)|| RA: -0.067 mas/yr |
Dec.: -1.889 mas/yr
|Parallax (π)||0.4403 ± 0.0856 mas|
|Distance||approx. 7,000 ly |
(approx. 2,300 pc)
|Period (P)||78.9±0.3 d|
|Surface gravity (log g)||3.43±0.15 cgs|
LB-1 is a binary star system in the constellation Gemini. It is composed of a B-type star and an unseen object that might be a black hole. If the star is an ordinary main sequence B-type star (with its luminosity in conflict with a mainstay astronomic satellite's parallax measurements), the companion which is strongly suspected to be solitary, would be a black hole having mass outside of ordinary single stellar evolution parameters.
The optically observed star, LB-1 A, or LS V+22 25, is a B-type star nine times the mass of the Sun and located at least 7,000 light-years (2,100 pc) from Earth. It was found to exhibit radial velocity variations by Chinese astronomers using the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) and the radial-velocity method to search for such wobbly stars.
The astronomers observed the star orbiting an unseen companion every 78.9 days, in what researchers described as a "surprisingly circular" orbit. Follow-up observations using the Gran Telescopio Canarias in Spain and the W. M. Keck Observatory in the United States better defined the findings.
The parallax to LB-1 has been published in Gaia Data Release 2, implying a distance around 2,300 pc. The observed spectral properties of the star are inconsistent with those expected for an ordinary main sequence B-type star at this distance.
A separate spectroscopic analysis of the star suggests that instead of a B-type main sequence star as had been indicated, LB-1 A is more likely a stripped helium star (whose spectrum is very similar) with only ~1 M☉, if at the distance determined by the Gaia satellite.
The unseen companion to the star was discovered by measuring the radial velocity shifts of its companion star. If it is a black hole, this would mark the first time a stellar black hole was discovered without observation of its X-ray emissions.
If the distance from parallax is ignored, and the star is assumed to be an ordinary main sequence B-type star, the unseen companion LB-1 B or LB-1 *, could be hypothesized to be a black hole, with a mass of about 70 solar masses, more than twice the mass as the maximum predicted by most current theories of stellar evolution. It would be in the stellar-mass black hole range, below the size of intermediate-mass black holes; however, it would fall in the pair-instability gap of black hole sizes, whereby sufficiently massive black hole progenitor stars undergo pair-instability supernovae and completely disintegrate, leaving no remnant behind. LB-1 would be the first black hole discovered in the mass gap range. The companion mass would be high enough that anything other than a black hole would be expected to be easily detected. According to one of the researchers, "This discovery forces us to re-examine our models of how stellar-mass black holes form [...] This remarkable result, along with the LIGO-Virgo detections of binary black hole collisions during the past four years, really points towards a renaissance in our understanding of black hole astrophysics."
- Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
- Liu, Jifeng; et al. (27 November 2019). "A wide star–black-hole binary system from radial-velocity measurements". Nature. 575 (7784): 618–621. arXiv:1911.11989. Bibcode:2019Natur.575..618L. doi:10.1038/s41586-019-1766-2. PMID 31776491.
- Irrgang, A.; Geier, S.; Kreuzer, S.; Pelisoli, I.; Heber, U. (January 2020). "A stripped helium star in the potential black hole binary LB-1". Astronomy and Astrophysics (Letter to the Editor). 633: L5. doi:10.1051/0004-6361/201937343.
- "Chinese Academy of Sciences leads discovery of unpredicted stellar black hole" (Press release). Chinese Academy of Sciences. EurekAlert!. 27 November 2019. Retrieved 29 November 2019.
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- Roberto Soria (3 December 2019). "Did this black hole swallow a star?". EarthSky.org.
- Jing Xuan TENG (28 November 2019). "Scientists spot black hole so huge it 'shouldn't even exist' in our galaxy". Space Daily. AFP.
- Katie Mettler (29 November 2019). "Scientists find 'monster' black hole so big they didn't think it was possible". Washington Post.
- Baker, Sinéad (29 November 219). "Chinese astronomers discovered a black hole so big it shouldn't exist according to current science". Business Insider. Retrieved 29 November 2019.
- Lewis, Sophie (28 November 2019). "Astronomers discover massive black hole that "should not even exist" in the Milky Way galaxy". CBS News. Retrieved 29 November 2019.
- Black Holes: Gravity's Relentless Pull – Interactive multimedia website about the physics and astronomy of black holes from the Space Telescope Science Institute
- Frequently Asked Questions (FAQs) on Black Holes