Galaxy in the constellation of Hydra
NGC 4993 starmap nearψ Hydrae , near galaxies ofNGC 4968 ,NGC 4970 ,NGC 5042 ,IC 4180 ,IC 4197 NGC 4993 (also catalogued asNGC 4994 in theNew General Catalogue ) is alenticular galaxy [ 5] light-years away[ 2] Hydra .[ 6] [ 7] William Herschel [ 6] [ 7] [ 3]
NGC 4993 was the site ofGW170817 , acollision of twoneutron stars , the first astronomical event detected in both electromagnetic and gravitational radiation, a discovery given theBreakthrough of the Year award for 2017 by the journalScience [ 8] [ 9] gamma-ray burst GRB 170817A short gamma-ray bursts .[ 10]
Physical characteristics [ edit ] NGC 4993 has several concentric shells of stars and a large dust lane—with a diameter of approximately a few kiloparsecs—which surrounds the nucleus and is stretched out into an "s" shape. The dust lane appears to be connected to a small dust ring with a diameter of ~330 ly (0.1 kpc ).[ 11] [ 12] [ 13] [ 14]
Dark matter content [ edit ] NGC 4993 has adark matter halo with an estimated mass of× 1010 M ☉ [ 13]
NGC 4993 has an estimated population of 250globular clusters .[ 5]
The luminosity of NGC 4993 indicates that the globular cluster system surrounding the galaxy may be dominated by metal-poor globular clusters.[ 15]
Supermassive black hole [ edit ] NGC 4993 has asupermassive black hole with an estimated mass of roughly 80 to 100 millionsolar masses (× 107 M ☉ [ 16]
Galactic nucleus activity [ edit ] The presence of weakO III ,NII andSII emission lines in the nucleus of NGC 4993 and the relatively high ratio of [NII]λ6583/Hα suggest that NGC 4993 is a low-luminosityAGN (LLAGN).[ 16] [ 13]
Neutron star merger observations [ edit ] On 17 August 2017,[ 17] [ 18] [ 19] [ 20] NASA 'sFermi andESA 'sINTEGRAL had detectedGRB 170817A short gamma-ray burst (sGRB) of the type conjectured to be emitted in the collision of twoneutron stars .[ 21] [ 17] LIGO andVirgo collaborations announced that, 1.7 seconds before the GRB signal, they had detectedGW170817 , agravitational wave event which matched predictions for such mergers. The gravitational wave signal had a duration of about 100 seconds, and was indeed later confirmed as the first gravitational wave detection of aneutron star merger .[ 1] [ 22] [ 23] [ 24]
The simultaneous detection of the GW and sGRB signals suggested that they were emitted by the same astrophysical event, so researchers scrambled to combine their data and narrow down its location in the sky.[ 25] [ 26] optical transient ,kilonova AT 2017gfo NGC 4993 , allowing the location of the merger to be precisely known.[ 23] [ 24] GW170817 ,GRB 170817A multi-messenger astronomy . For example, the initial GW and sGRB signals had traveled for 140 million years at the speed of light before arriving at earth only 1.7 seconds apart, empirically tightening the previous constraint on the speed of gravity by around 14 orders of magnitude.[ 26] [ 25] [ 27]
^a b Chou, Felicia; Washington, Dewayne; Porter, Molly (16 October 2017)."Release 17-083 - NASA Missions Catch First Light from a Gravitational-Wave Event" .NASA . Retrieved21 October 2017 . ^a b c d e f g h i j "NASA/IPAC Extragalactic Database" .Results for NGC 4993 . Retrieved3 June 2018 .^a b Hjorth, Jens; Levan, Andrew J.; Tanvir, Nial R.; Lyman, Joe D.; Wojtak, Radosław; Schrøder, Sophie L.; Mandel, Ilya; Gall, Christa; Bruun, Sofie H. (16 October 2017)."The Distance to NGC 4993: The Host Galaxy of the Gravitational-wave Event GW170817" .The Astrophysical Journal .848 (2): L31.arXiv :1710.05856 Bibcode :2017ApJ...848L..31H .doi :10.3847/2041-8213/aa9110 hdl :2381/41880 .S2CID 51812508 . ^ Staff (2017)."Galaxy NGC 4993 - Galaxy in Hydra Constellation" .dso-browser.com . Archived fromthe original on 16 September 2017. Retrieved30 September 2017 . ^a b Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X. (1 December 2017)."On the Progenitor of Binary Neutron Star Merger GW170817" .The Astrophysical Journal .850 (2): L40.arXiv :1710.05838 Bibcode :2017ApJ...850L..40A .doi :10.3847/2041-8213/aa93fc S2CID 29357210 . ^a b "NGC 4993" .Deep Sky Observer's Companion . Retrieved28 August 2017 .^a b "New General Catalog Objects: NGC 4950 - 4999" .cseligman.com . Retrieved5 June 2018 .^ "Breakthrough of the year 2017" .Science | AAAS . 22 December 2017.^ Cho, Adrian (2017). "Cosmic convergence".Science .358 (6370):1520– 1521.Bibcode :2017Sci...358.1520C .doi :10.1126/science.358.6370.1520 .PMID 29269456 . ^ Overbye, Dennis (16 October 2017)."LIGO Detects Fierce Collision of Neutron Stars for the First Time" .The New York Times . Retrieved16 October 2017 . ^ Blanchard, P. K.; Berger, E.; Fong, W.; Nicholl, M.; Leja, J.; Conroy, C.; Alexander, K. D.; Margutti, R.; Williams, P. K. G. (16 October 2017)."The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. VII. Properties of the Host Galaxy and Constraints on the Merger Timescale" .The Astrophysical Journal .848 (2): L22.arXiv :1710.05458 Bibcode :2017ApJ...848L..22B .doi :10.3847/2041-8213/aa9055 S2CID 119336499 . ^ Im, Myungshin; Yoon, Yongmin; Lee, Seong-Kook J.; Lee, Hyung Mok; Kim, Joonho; Lee, Chung-Uk; Kim, Seung-Lee; Troja, Eleonora; Choi, Changsu (26 October 2017)."Distance and Properties of NGC 4993 as the Host Galaxy of the Gravitational-wave Source GW170817" .The Astrophysical Journal .849 (1): L16.arXiv :1710.05861 Bibcode :2017ApJ...849L..16I .doi :10.3847/2041-8213/aa9367 S2CID 55716501 . ^a b c Ebrová, Ivana; Bílek, Michal (2020). "NGC 4993 the shell galaxy host of GW170817: constraints on the recent galactic merger".Astronomy & Astrophysics .634 : A73.arXiv :1801.01493 Bibcode :2020A&A...634A..73E .doi :10.1051/0004-6361/201935219 .S2CID 56354361 . ^ Palmese, A.; Hartley, W.; Tarsitano, F.; Conselice, C.; Lahav, O.; Allam, S.; Annis, J.; Lin, H.;Soares-Santos, M. (9 November 2017)."Evidence for Dynamically Driven Formation of the GW170817 Neutron Star Binary in NGC 4993" .The Astrophysical Journal .849 (2): L34.arXiv :1710.06748 Bibcode :2017ApJ...849L..34P .doi :10.3847/2041-8213/aa9660 S2CID 55049352 . ^ Lee, Myung Gyoon; Kang, Jisu; Im, Myungshin (20 May 2018)."A Globular Cluster Luminosity Function Distance to NGC 4993 Hosting a Binary Neutron Star Merger GW170817/GRB 170817A" .The Astrophysical Journal Letters .859 (1): L6.arXiv :1805.01127 Bibcode :2018ApJ...859L...6L .doi :10.3847/2041-8213/aac2e9 S2CID 73713875 . ^a b Wu, Qingwen; Feng, Jianchao; Fan, Xuliang (6 March 2018)."The Possible Submillimeter Bump and Accretion-jet in the Central Supermassive Black Hole of NGC 4993" .The Astrophysical Journal .855 (1): 46.arXiv :1710.09590 Bibcode :2018ApJ...855...46W .doi :10.3847/1538-4357/aaac28 S2CID 89606053 . ^a b Drake, Nadia (25 August 2017)."Strange stars caught wrinkling spacetime? Get the facts" .National Geographic the original on 27 August 2017. Retrieved27 August 2017 .^ von Kienlin, Andreas (17 August 2017)."GCN Circular Number 21520; GRB 170817A: Fermi GBM detection; 2017-08-17 20:00:07 GMT" .Max Planck Institute for Extraterrestrial Physics . Retrieved28 August 2017 . ^ Castelvecchi, Davide (25 August 2017)."Rumours swell over new kind of gravitational-wave sighting" .Nature .Nature News .doi :10.1038/nature.2017.22482 . Retrieved27 August 2017 . ^ Sokol, Joshua (25 August 2017)."What Happens When Two Neutron Stars Collide?" .Wired . Retrieved28 August 2017 . ^ Nakar, E. (2007). "Short-hard gamma-ray bursts".Physics Reports 442 (1– 6):166– 236.arXiv :astro-ph/0701748 Bibcode :2007PhR...442..166N .CiteSeerX 10.1.1.317.1544 doi :10.1016/j.physrep.2007.02.005 .S2CID 119478065 . ^ Abbott, B.P.; et al. (16 October 2017). "GW 170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral".Physical Review Letters .119 (16) 161101.arXiv :1710.05832 Bibcode :2017PhRvL.119p1101A .doi :10.1103/PhysRevLett.119.161101 .PMID 29099225 .S2CID 217163611 . ^a b Cho, Adrian (16 October 2017)."Merging neutron stars generate gravitational waves and a celestial light show" .Science doi :10.1126/science.aar2149 . Retrieved16 October 2017 . ^a b Krieger, Lisa M. (16 October 2017)."A Bright Light Seen Across The Universe, Proving Einstein Right - Violent collisions source of our gold, silver" .The Mercury News . Retrieved16 October 2017 . ^a b Overbye, Dennis (16 October 2017)."LIGO Detects Fierce Collision of Neutron Stars for the First Time" .The New York Times . Retrieved16 October 2017 .^a b Landau, Elizabeth; Chou, Felicia; Washington, Dewayne; Porter, Molly (16 October 2017)."NASA Missions Catch First Light from a Gravitational-Wave Event" .NASA . Retrieved16 October 2017 . ^ Abbott, B. P.; et al. (LIGO Scientific Collaboration &Virgo Collaboration ) (16 October 2017)."GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral" .Physical Review Letters .119 (16) 161101.arXiv :1710.05832 Bibcode :2017PhRvL.119p1101A .doi :10.1103/PhysRevLett.119.161101 PMID 29099225 . Wikimedia Commons has media related to
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