{"id":15472,"date":"2018-01-17T06:00:29","date_gmt":"2018-01-17T11:00:29","guid":{"rendered":"http:\/\/hobbyspace.com\/Blog\/?p=15472"},"modified":"2018-01-15T23:57:48","modified_gmt":"2018-01-16T04:57:48","slug":"eso-unusual-movement-of-star-indicates-orbit-around-black-hole-four-times-mass-of-sun","status":"publish","type":"post","link":"https:\/\/hobbyspace.com\/Blog\/?p=15472","title":{"rendered":"ESO: Unusual movement of star indicates orbit around black hole four times mass of Sun"},"content":{"rendered":"

A new report from ESO<\/a> (European Southern Observatory):<\/p>\n

Odd Behaviour of Star Reveals Lonely Black Hole Hiding in Giant Star Cluster<\/a><\/strong><\/p>\n

\"\"<\/a>
Artist\u2019s impression of the black hole binary system in NGC 3201. Astronomers using ESO\u2019s MUSE instrument on the Very Large Telescope in Chile have discovered a star in the cluster NGC 3201 that is behaving very strangely. It appears to be orbiting an invisible black hole with about four times the mass of the Sun \u2014 the first such inactive stellar-mass black hole found in a globular cluster. This important discovery impacts on our understanding of the formation of these star clusters, black holes, and the origins of gravitational wave events.This artist\u2019s impression shows how the star and its massive but invisible black hole companion may look, in the rich heart of the globular star cluster. [Larger images<\/a>]<\/em><\/figcaption><\/figure>Astronomers using ESO\u2019s MUSE instrument on the Very Large Telescope in Chile have discovered a star in the cluster NGC 3201 that is behaving very strangely. It appears to be orbiting an invisible black hole with about four times the mass of the Sun \u2014 the first such inactive stellar-mass black hole found in a globular cluster and the first found by directly detecting its gravitational pull. This important discovery impacts on our understanding of the formation of these star clusters, black holes, and the origins of gravitational wave events.<\/p>\n
https:\/\/cdn.eso.org\/videos\/medium_podcast\/eso1802a.mp4<\/a><\/video><\/div>\n

Astronomers using ESO\u2019s MUSE instrument on the Very Large Telescope in Chile have discovered a star in the cluster NGC 3201 that is behaving very strangely. It appears to be orbiting an invisible black hole with about four times the mass of the Sun \u2014 the first such inactive stellar-mass black hole found in a globular cluster.\u00a0This important discovery impacts on our understanding of the formation of these star clusters, black holes, and the origins of gravitational wave events.\u00a0This short ESOcast takes a look at this discovery and its significance.<\/em><\/p>\n

Globular star clusters<\/a>\u00a0are huge spheres of tens of thousands of stars that orbit most galaxies. They are among the oldest known stellar systems in the Universe and date back to near the beginning of galaxy growth and evolution. More than 150 are currently known to belong to the Milky Way.<\/p>\n

One particular cluster, called\u00a0NGC 3201<\/a>\u00a0and situated in the southern constellation of\u00a0Vela<\/a>\u00a0(The Sails), has now been studied using the\u00a0MUSE instrument<\/a>\u00a0on ESO\u2019s\u00a0Very Large Telescope<\/a>\u00a0in Chile. An international team of astronomers has found that one of the stars\u00a0[1]<\/a>\u00a0in NGC 3201 is behaving very oddly \u2014 it is being flung backwards and forwards at speeds of several hundred thousand kilometres per hour, with the pattern repeating every 167 days\u00a0[2]<\/a>.<\/p>\n

\"\"<\/a>
This image from the NASA\/ESA Hubble Space Telescope shows the central region of the rich globular star cluster NGC 3201 in the southern constellation of Vela (The Sails). A star that has been found to be orbiting a black hole with four times the mass of the Sun is indicated with blue circle. [Larger images<\/a>.]<\/em><\/figcaption><\/figure>Lead author Benjamin Giesers (Georg-August-Universit\u00e4t G\u00f6ttingen<\/a>, Germany) was intrigued by the star\u2019s behaviour:<\/p>\n

\u201cIt was orbiting something that was completely invisible, which had a mass more than four times the Sun \u2014 this could only be a black hole! The first one found in a globular cluster by directly observing its gravitational pull.<\/em>\u201d<\/p>\n

The relationship between\u00a0black holes<\/a>\u00a0and\u00a0globular clusters<\/a>\u00a0is an important but mysterious one. Because of their large masses and great ages, these clusters are thought to have produced a large number of\u00a0stellar-mass black holes<\/a>\u00a0\u2014 created as massive stars within them exploded and collapsed over the long lifetime of the cluster\u00a0[3]<\/a>[4]<\/a>.<\/p>\n

https:\/\/cdn.eso.org\/videos\/medium_podcast\/eso1802b.mp4<\/a><\/video><\/div>\n

This video takes us towards the southern constellation of Vela (The Sails), where we find the bright globular star cluster NGC 3201. This huge and ancient ball of stars has been found to harbour an invisible black hole with four times the mass of the Sun. The final sharp view of the centre of the cluster comes from the NASA\/ESA Hubble Space Telescope.\u00a0Credit:\u00a0ESO\/ESA\/NASA\/Digitized Sky Survey 2\/N. Risinger (skysurvey.org<\/a>). Music: Astral Electronic<\/em><\/p>\n

ESO\u2019s MUSE instrument provides astronomers with a unique ability to measure the motions of thousands of far away stars at the same time. With this new finding, the team have for the first time been able to detect an inactive black hole at the heart of a globular cluster \u2014 one that is not currently swallowing matter and is not surrounded by a glowing disc of gas. They could estimate the black hole\u2019s mass through the movements of a star caught up in its enormous gravitational pull\u00a0[5]<\/a>.<\/p>\n

From its observed properties the star was determined to be about 0.8 times the mass of our Sun, and the mass of its mysterious counterpart was calculated at around 4.36 times the Sun\u2019s mass \u2014 almost certainly a black hole\u00a0[6]<\/a>.<\/p>\n

\"\"<\/a>
Colour-composite image of the globular cluster NGC 3201, obtained with the WFI instrument on the ESO\/MPG 2.2-m telescope at La Silla. Globular clusters are large aggregates of stars, that can contain up to millions of stars. They are among the oldest objects observed in the Universe and were presumably formed at about the same time as the Milky Way Galaxy, in the early phase after the Big Bang. This particular globular cluster is located about 16 000 light-years away towards the Southern Vela constellation. The data were obtained as part of the ESO Imaging Survey (EIS), a public survey being carried out by ESO and member states, in preparation for the VLT First Light. The original image and astronomical data can be retrieved from the\u00a0EIS Pre-Flames Survey Data Release pages, where many other nice images are also available. [Larger images<\/a>]<\/em><\/figcaption><\/figure>Recent detections of radio and X-ray sources in globular clusters, as well as the 2016 detection of gravitational-wave signals produced by the merging of two stellar-mass black holes, suggest that these relatively small black holes may be more common in globular clusters than previously thought.<\/p>\n

Giesers concludes:<\/p>\n

\u201cUntil recently, it was assumed that almost all black holes would disappear from globular clusters after a short time and that systems like this should not even exist! But clearly this is not the case \u2014\u00a0our discovery is the first direct detection of the gravitational effects of a stellar-mass black hole in a globular cluster. This finding helps in\u00a0understanding the formation of globular clusters and the evolution of black holes and binary systems \u2014 vital in the context of understanding gravitational wave sources.<\/em>\u201d<\/p>\n

Notes<\/strong><\/p>\n

<\/a>[1] The star found is a main sequence turn-off star, meaning it is at the end of the\u00a0main sequence<\/a>\u00a0phase of its life. Having exhausted its primary hydrogen fuel supply it is now on the way to becoming a\u00a0red giant<\/a>.<\/p>\n

<\/a>[2] A large survey of 25 globular clusters around the Milky Way is currently being conducted using ESO\u2019s MUSE instrument with the support of the MUSE consortium. It will provide astronomers with the spectra of 600 to 27 000 stars in each cluster. The study includes analysis of the \u201cradial velocity\u201d of individual stars \u2014 the speed at which they move away from and toward the Earth, along the line of sight of the observer. With radial velocity measurements the orbits of stars can be determined, as well as the properties of any massive object they may be orbiting.<\/p>\n

<\/a>[3] In the absence of continuous star formation, as is the case for globular clusters, stellar-mass black holes soon become the most massive objects present. Generally, stellar-mass black holes in globular clusters are about four times as massive as the surrounding low-mass stars. Recent theories have concluded that black holes form a dense nucleus within the cluster, which then becomes detached from the rest of the globular material. Movements at the centre of the cluster are then thought to eject the majority of black holes, meaning only a few would survive after a billion years.<\/p>\n

<\/a>[4]\u00a0Stellar-mass black holes<\/a>\u00a0\u2014 or collapsars \u2014 are formed when massive stars die, collapsing under their own gravity and exploding as powerful\u00a0hypernovae<\/a>. Left behind is a black hole with most of the mass of the former star, which can range from a few times the mass of our Sun to several tens of times as massive.<\/p>\n

<\/a>[5] As no light is able to escape black holes because of their tremendous gravity, the primary method of detecting them is through observations of radio or X-ray emissions coming from hot material around them. But when a black hole is not interacting with hot matter and so not accumulating mass or emitting radiation, as in this case, the black hole is \u201cinactive\u201d and invisible, so another method of detection is required.<\/p>\n

<\/a>[6] Because the non-luminous object in this binary system cannot be directly observed there are alternative, although much less persuasive, explanations for what it could be. It is perhaps a triple star system made up of two tightly bound neutron stars, with the observed star orbiting around them. This scenario would require each tightly bound star to be at least twice the mass of our Sun, a binary system that has never been observed before.<\/p>\n","protected":false},"excerpt":{"rendered":"

A new report from ESO (European Southern Observatory): Odd Behaviour of Star Reveals Lonely Black Hole Hiding in Giant Star Cluster Astronomers using ESO\u2019s MUSE instrument on the Very Large Telescope in Chile have discovered a star in the cluster NGC 3201 that is behaving very strangely. It appears to be orbiting an invisible black … Continue reading ESO: Unusual movement of star indicates orbit around black hole four times mass of Sun<\/span> →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"jetpack_post_was_ever_published":false,"_jetpack_newsletter_access":"","_jetpack_dont_email_post_to_subs":false,"_jetpack_newsletter_tier_id":0,"_jetpack_memberships_contains_paywalled_content":false,"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[12],"tags":[],"class_list":["post-15472","post","type-post","status-publish","format-standard","hentry","category-astronomy"],"jetpack_featured_media_url":"","jetpack_sharing_enabled":true,"jetpack_shortlink":"https:\/\/wp.me\/p34aWK-41y","jetpack-related-posts":[{"id":24680,"url":"https:\/\/hobbyspace.com\/Blog\/?p=24680","url_meta":{"origin":15472,"position":0},"title":"ESO: Black hole discovered in star cluster outside the Milky Way","author":"TopSpacer","date":"November 11, 2021","format":false,"excerpt":"A new report from ESO (European Southern Observatory): Black hole found hiding in star cluster outside our galaxy Using the European Southern Observatory\u2019s Very Large Telescope (ESO\u2019s VLT), astronomers have discovered a small black hole outside the Milky Way by looking at how it influences the motion of a star\u2026","rel":"","context":"In "Astronomy"","block_context":{"text":"Astronomy","link":"https:\/\/hobbyspace.com\/Blog\/?cat=12"},"img":{"alt_text":"","src":"https:\/\/i0.wp.com\/hobbyspace.com\/Blog\/wp-content\/uploads\/2021\/11\/eso1914a1.jpg?resize=350%2C200&ssl=1","width":350,"height":200,"srcset":"https:\/\/i0.wp.com\/hobbyspace.com\/Blog\/wp-content\/uploads\/2021\/11\/eso1914a1.jpg?resize=350%2C200&ssl=1 1x, https:\/\/i0.wp.com\/hobbyspace.com\/Blog\/wp-content\/uploads\/2021\/11\/eso1914a1.jpg?resize=525%2C300&ssl=1 1.5x, https:\/\/i0.wp.com\/hobbyspace.com\/Blog\/wp-content\/uploads\/2021\/11\/eso1914a1.jpg?resize=700%2C400&ssl=1 2x"},"classes":[]},{"id":15103,"url":"https:\/\/hobbyspace.com\/Blog\/?p=15103","url_meta":{"origin":15472,"position":1},"title":"ESO: The Fornax Galaxy Cluster reveals its secrets to the Very Large Telescope (VLT)","author":"TopSpacer","date":"October 25, 2017","format":false,"excerpt":"A new report from\u00a0ESO (European Southern Observatory): Revealing Galactic Secrets Countless galaxies vie for attention in this monster image of the Fornax Galaxy Cluster, some appearing only as pinpricks of light while others dominate the foreground. 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