View source for Astronomy:Sagittarius B2

{{Short description|A giant molecular cloud near the Milky Way's center}}
{{infobox nebula
|type= giant molecular cloud
|name= Sagittarius B2
|epoch= [[Astronomy:J2000.0|J2000.0]]<ref name=SIMBAD/>
|ra= {{RA|17|47|20.4}}<ref name=SIMBAD/>
|dec= {{DEC|-28|23|07}}<ref name=SIMBAD/>
|constellation= [[Astronomy:Sagittarius (constellation)|Sagittarius]]
|radius_pc= 23
|names= Sagittarius B2, Sgr B2
}}
'''Sagittarius B2''' ('''Sgr B2''') is a giant [[Astronomy:Molecular cloud|molecular cloud]] of gas and dust that is located about {{convert|120|pc|ly|lk=on}} from the center of the [[Astronomy:Milky Way|Milky Way]]. This complex is the largest molecular cloud in the vicinity of the core and one of the largest in the galaxy, spanning a region about {{convert|45|pc|ly}} across.<ref name="chown"/> The total mass of Sgr B2 is about 3 million times the [[Astronomy:Solar mass|mass of the Sun]].<ref name=solomon78/> The mean hydrogen density within the cloud is 3000 atoms per cm<sup>3</sup>, which is about 20&ndash;40 times denser than a typical molecular cloud.<ref name=apj350/>

The internal structure of this cloud is complex, with varying densities and temperatures. The cloud is divided into three main cores, designated north (N), middle or main (M) and south (S) respectively. Thus Sgr B2(N) represents the north core. The sites Sgr B2(M) and Sgr B2(N) are sites of prolific star formation. The first 10 [[Astronomy:H II region|H&nbsp;II regions]] discovered were designated A through J.<ref name=apj356/> H&nbsp;II regions A–G, I and J lie within Sgr B2(M), while region K is in Sgr B2(N) and region H is in Sgr B2(S).<ref name=apj573/> The 5-parsec-wide core of the cloud is a star-forming region that is emitting about 10 million times the [[Astronomy:Solar luminosity|luminosity of the Sun]].<ref name=wolstencroft88/>

The cloud is composed of various kinds of complex molecules, of particular interest: [[Chemistry:Alcohol|alcohol]]. The cloud contains [[Chemistry:Ethanol|ethanol]], [[Chemistry:Vinyl alcohol|vinyl alcohol]], and [[Chemistry:Methanol|methanol]]. This is due to the conglomeration of atoms resulting in new molecules. The composition was discovered via [[Astronomy:Spectrograph|spectrograph]] in an attempt to discover [[Chemistry:Amino acid|amino acid]]s. An [[Chemistry:Ester|ester]], [[Chemistry:Ethyl formate|ethyl formate]], was also discovered, which is a major precursor to amino acids. This ester is also responsible for the flavour of [[Biology:Raspberry|raspberries]],<ref>{{Cite web|last=Gupta|first=Richa|date=2015-08-12|title=Raspberries and Rum- Sagittarius B2|url=https://astronaut.com/raspberries-and-rum-sagittarius-b2/|access-date=2020-07-25|website=Astronaut|language=en-US|archive-date=2022-07-18|archive-url=https://web.archive.org/web/20220718174241/https://astronaut.com/raspberries-and-rum-sagittarius-b2/|url-status=dead}}</ref> leading some articles on Sagittarius B2 to postulate the cloud as smelling of ‘raspberry [[Chemistry:Rum|rum]]’.<ref>{{Cite web|title=A raspberry flavoured galactic centre with a hint of rum|url=https://analyticalscience.wiley.com/do/10.1002/sepspec.21408ezine|access-date=2020-07-25|website=Wiley Analytical Science|language=en|doi=10.1002/sepspec.21408ezine| doi-broken-date=1 August 2023 }}</ref><ref>{{Cite web|last=Team|first=How It Works|date=2015-12-03|title=The Milky Way smells of rum and tastes like raspberries|url=https://www.howitworksdaily.com/the-milky-way-smells-of-rum-and-tastes-like-raspberries/|access-date=2020-07-25|website=How It Works|language=en-GB}}</ref> Large quantities of [[Chemistry:Butyronitrile|butyronitrile]] (propyl cyanide) and other alkyl cyanides have also been detected as being present in the cloud.<ref>{{Cite journal|last1=Belloche|first1=A.|last2=Garrod|first2=R. T.|last3=Müller|first3=H. S. P.|last4=Menten|first4=K. M.|last5=Comito|first5=C.|last6=Schilke|first6=P.|date=2009-05-01|title=Increased complexity in interstellar chemistry: detection and chemical modeling of ethyl formate and n-propyl cyanide in Sagittarius B2(N)|url=https://www.aanda.org/articles/aa/abs/2009/19/aa11550-08/aa11550-08.html|journal=Astronomy & Astrophysics|language=en|volume=499|issue=1|pages=215–232|doi=10.1051/0004-6361/200811550|issn=0004-6361|arxiv=0902.4694| bibcode=2009A&A...499..215B | s2cid=98625608 }}</ref>

Temperatures in the cloud vary from {{convert|300|K|°C|abbr=on|lk=on}} in dense star-forming regions to {{convert|40|K|°C|abbr=on}} in the surrounding envelope.<ref name=pasp960310/> Because the average temperature and pressure in Sgr B2 are low, chemistry based on the direct interaction of atoms is exceedingly slow. However, the Sgr B2 complex contains cold dust grains consisting of a silicon core surrounded by a mantle of water ice and various carbon compounds. The surfaces of these grains allow chemical reactions to occur by accreting molecules that can then interact with neighboring compounds. The resulting compounds can then evaporate from the surface and join the molecular cloud.<ref name="chown"/>

The molecular components of this cloud can be readily observed in the 10<sup>2</sup>&ndash;10<sup>3</sup>&nbsp;μm range of wavelengths.<ref name="chown"/>  About half of all the known interstellar molecules were first found near Sgr B2, and nearly every other currently known molecule has since been detected in this feature.<ref name=apjss60/>

The [[Organization:European Space Agency|European Space Agency]]'s gamma-ray observatory [[Astronomy:INTEGRAL|INTEGRAL]] has observed gamma rays interacting with Sgr B2, causing X-ray emission from the molecular cloud. This energy was emitted about 350 years ago by the [[Astronomy:Supermassive black hole|supermassive black hole]] (SMBH) at the galaxy's core, [[Astronomy:Sagittarius A*|Sagittarius A*]]. The total luminosity from this outburst is an estimated million times stronger than the current output from Sagittarius A*.<ref name=hubble050127/><ref name=revnivtsev2004/> This conclusion has been supported in 2011 by Japanese astronomers who observed the [[Galactic Center]] with the [[Astronomy:Suzaku (satellite)|Suzaku]] satellite.<ref name=nobukawa2011/>

==See also==
* [[Astronomy:Large Molecule Heimat|Large Molecule Heimat]]
* List of molecules in interstellar space

==References==
{{reflist|20em|refs=

<ref name=SIMBAD>{{cite simbad |title= NAME Sgr B2 |access-date= 2014-03-14 }}</ref>

<ref name="chown">{{cite news | last=Chown | first=Marcus | date=November 27, 1999 | title=Star attraction | publisher=New Scientist | url=https://www.newscientist.com/article/mg16422144.900-star-attraction.html | access-date=2007-10-29 }}</ref>

<ref name=solomon78>{{cite book | first=P. M. | last=Solomon |editor1=Giancarlo Setti |editor2=Giovanni G. Fazio | year=1978 | title=Physics of Molecular Clouds from Millimeter Wave Length Observations | work=Infrared Astronomy | publisher=Springer | location=New York | isbn=90-277-0871-1 }}</ref>

<ref name=apj350>{{cite journal | last=Goldsmith | first=Paul F. |author2=Lis, Dariusz C. |author3=Hills, Richard |author4= Lasenby, Joan  | title=High angular resolution submillimeter observations of Sagittarius B2 | journal=Astrophysical Journal | year=1990 | volume=350 | pages=186–194 | bibcode=1990ApJ...350..186G | doi=10.1086/168372 }}</ref>

<ref name=apj356>{{cite journal | last=Lis | first=Dariusz C. |author2=Goldsmith, Paul F.  | title=Modeling of the continuum and molecular line emission from the Sagittarius B2 molecular cloud | journal=Astrophysical Journal, Part 1 | year=1990 | volume=356 | pages=195–210 | bibcode=1990ApJ...356..195L | doi=10.1086/168830 }}</ref>

<ref name=apj573>{{cite journal | last=Takagi | first=Shin-ichiro |author2=Murakami, Hiroshi |author3=Koyama, Katsuji  | title=X-Ray Sources and Star Formation Activity in the Sagittarius B2 Cloud Observed with Chandra  | journal=The Astrophysical Journal | year=2002 | volume=573 | issue=1 | pages=275–282 | bibcode=2002ApJ...573..275T | doi=10.1086/340499 |arxiv = astro-ph/0203035 | s2cid=119426549 }}</ref>

<ref name=wolstencroft88>{{cite book | first=Ramon D. | last=Wolstencroft |author2=William Butler Burton  | year=1988 | title=Millimetre and Submillimetre Astronomy | publisher=Springer | isbn=90-277-2763-5 }}</ref>

<ref name=pasp960310>{{cite conference | first=P. | last=de Vicente |author2=Martin-Pintado, J. |author3=Wilson, T. L.  | title=A Hot Ring in the SGR B2 Molecular Cloud | book-title=Proceedings Astronomical Society of the Pacific Conference Series | pages=64&ndash;67 | publisher=Astronomical Society of the Pacific. | date=March 10–15, 1996 | location=La Serena, Chile | bibcode=1996ASPC..102...64D }}</ref>

<ref name=apjss60>{{cite journal |author1=S. E. Cummins |author2=R. A. Linke |author3=P. Thaddeus | title=A survey of the millimeter-wave spectrum of Sagittarius B2 | journal=Astrophysical Journal Supplement Series | year=1986 | volume=60 | pages=819–878 | bibcode=1986ApJS...60..819C | doi=10.1086/191102 }}</ref>

<ref name=hubble050127>{{cite news | author=Staff | date=January 28, 2005 | title=Integral rolls back history of Milky Way's super-massive black hole | publisher=Hubble News Desk | url=http://www.esa.int/SPECIALS/Integral/SEMSKPO3E4E_0.html | access-date=2007-10-31 }}</ref>

<ref name=revnivtsev2004>{{cite journal | author=M. G. Revnivtsev |display-authors=et al. | title=Hard X-ray view of the past activity of Sgr A* in a natural Compton mirror | journal=Astronomy and Astrophysics | year=2004 | volume=425 | pages=L49–L52 | bibcode=2004A&A...425L..49R | doi=10.1051/0004-6361:200400064|arxiv = astro-ph/0408190 |s2cid=18872302 }}</ref>

<ref name=nobukawa2011>{{cite journal | author=M. Nobukawa |display-authors=et al. | title=New Evidence for High Activity of the Supermassive Black Hole in our Galaxy | journal=The Astrophysical Journal Letters | year=2011 | volume=739 |issue=2 | pages=L52 | bibcode=2011ApJ...739L..52N | doi=10.1088/2041-8205/739/2/L52| arxiv=1109.1950|s2cid=119244398 }}</ref>

}}

==External links==
*{{cite web
 | author=R. M. Gaume 
 | display-authors=et al.
 | date=October 31, 2007
 | url=http://www.nrao.edu/imagegallery/php/level3.php?id=55
 | title=Sagittarius B1 (North)
 | publisher=[[Astronomy:National Radio Astronomy Observatory|National Radio Astronomy Observatory]]
 | access-date=2007-10-31
}}
* [https://scitechdaily.com/how-did-organic-matter-reach-earth-cosmic-detectives-trace-origin-of-complex-organic-molecules/ How Did Organic Matter Reach Earth? Cosmic Detectives Trace Origin of Complex Organic Molecules], on: SciTechDaily. September 10, 2020. Source: Tokyo University of Science: [[Chemistry:Acetonitrile|Acetonitrile]] found in molecular cloud Sgr B2(M) at the center of the Milky Way galaxy.

[[Category:Molecular clouds]]

{{Sourceattribution|Sagittarius B2}}