Cassiopeia A
{{short description|Supernova remnant in the constellation Cassiopeia}}
{{Infobox supernova | name = Cassiopeia A
| image = Cassiopeia A Spitzer Crop.jpg
| caption = A false color image composed of data from three sources: Red is infrared data from the Spitzer Space Telescope, gold is visible data from the Hubble Space Telescope, and blue and green are data from the Chandra X-ray Observatory. The small, bright, baby-blue dot just off-center is the remnant of the star's core.
| type = IIb
| epoch = J2000
| SNRtype = Shell
| host = Milky Way
| ra = {{RA|23|23|24}}
| dec = {{DEC|+58|48.9}}
| gal = 111.734745°, −02.129570°
| discovery = 1947 by Martin Ryle and Francis Graham-Smith)
| distance = {{circa}} 11,000 ly{{cite journal |title=The expansion asymmetry and age of the Cassiopeia A supernova remnant |date=July 2006 |journal=The Astrophysical Journal |volume=645 |issue=1 |pages=283–292 |bibcode=2006ApJ...645..283F |doi=10.1086/504254 |arxiv=astro-ph/0603371 |last1=Fesen |first1=Robert A. |last2=Hammell |first2=Molly C. |last3=Morse |first3=Jon |last4=Chevalier |first4=Roger A. |last5=Borkowski |first5=Kazimierz J. |last6=Dopita |first6=Michael A. |last7=Gerardy |first7=Christopher L. |last8=Lawrence |first8=Stephen S. |last9=Raymond |first9=John C. |first10=Sidney |last10=van den Bergh|s2cid=8999768 }}
| mag_v = {{circa}} 6
| notes = Strongest radio source beyond our solar system
| predecessor = SN 1604
| successor = G1.9+0.3 (unobserved, {{circa|1868}}), SN 1885A (next observed)
|event_type=Supernova|constellation=Cassiopeia}}
Cassiopeia A (Cas A) ({{audio|Cassiopeia (spoken word).ogg|listen| help=no}}) is a supernova remnant (SNR) in the constellation Cassiopeia and the brightest extrasolar radio source in the sky at frequencies above 1 GHz. The supernova occurred approximately {{convert|11000|ly|kpc|1|lk=on}} away within the Milky Way;{{cite magazine |last=Stover |first=Dawn |title=Life in a bubble |magazine=Popular Science |volume=269 |issue=6 |date=2006 |page=16}} given the width of the Orion Arm, it lies in the next-nearest arm outwards, the Perseus Arm, about 30 degrees from the Galactic anticenter. The expanding cloud of material left over from the supernova now appears approximately {{convert|10|ly|pc|0}} across from Earth's perspective. It has been seen in wavelengths of visible light with amateur telescopes down to 234 mm (9.25 in) with filters.{{cite magazine |first=Howard |last=Banich |title=A visual guide to the Cassiopeia A supernova remnant |magazine=Sky & Telescope |date=December 2014}}
It is estimated that light from the supernova itself first reached Earth near the 1660s, although there are no definitively corresponding records from then. Cas A is circumpolar at and above mid-Northern latitudes which had extensive records and basic telescopes. Its likely omission in records is probably due to interstellar dust absorbing optical wavelength radiation before it reached Earth, although it is possible that it was recorded as a sixth magnitude star 3 Cassiopeiae by John Flamsteed. Possible explanations lean toward the idea that the source star was unusually massive and had previously ejected much of its outer layers. These outer layers would have cloaked the star and absorbed much of the visible-light emission as the inner star collapsed.
Cas A was among the first discrete astronomical radio sources found. Its discovery was reported in 1948 by Martin Ryle and Francis Graham-Smith, astronomers at Cambridge, based on observations with the Long Michelson Interferometer.{{cite journal |pages=462–463 |date=September 18, 1948 |bibcode=1948Natur.162..462R |doi=10.1038/162462a0 |issue=4116 |volume=162 |title=A new intense source of radio-frequency radiation in the constellation of Cassiopeia |journal=Nature |last1=Ryle |first1=M. |author-link1=Martin Ryle |last2=Smith |first2=F. G. |s2cid=4028114 |author2-link=Francis Graham-Smith |df=dmy-all}} The optical component was first identified in 1950.
Possible observations
Calculations working back from the currently observed expansion point to an explosion that would have become visible on Earth around 1667. Astronomer William Ashworth and others have suggested that the Astronomer Royal John Flamsteed may have inadvertently observed the supernova on {{OldStyleDate|16 August|1680|6 August}}, when he catalogued a sixth-magnitude star 3 Cassiopeiae, but there is no corresponding star at the recorded position. Possible explanations include an error in the position,{{cite journal |last1=Ashworth |first1=W. B. |year=1980 |title=A Probable Flamsteed Observation of the Cassiopeia a Supernova |journal=Journal for the History of Astronomy |volume=11 |page=1 |bibcode=1980JHA....11....1A |doi=10.1177/002182868001100102 |s2cid=121684168}} or that a transient was recorded. Caroline Herschel noted that a star in the vicinity of τ Cas, HD 220562, fit well with 3 Cas if a common error in sextant readings was made.{{Cite journal |last=Ashworth |first=William B. |date=February 1980 |title=A Probable Flamsteed Observation of the Cassiopeia a Supernova |url=http://journals.sagepub.com/doi/10.1177/002182868001100102 |journal=Journal for the History of Astronomy |language=en |volume=11 |issue=1 |pages=1–9 |doi=10.1177/002182868001100102 |bibcode=1980JHA....11....1A |s2cid=121684168 |issn=0021-8286}} Alternatively, the star AR Cassiopeiae may have been observed, again with the position recorded incorrectly. The position and timing mean that it may have been an observation of the Cassiopeia A progenitor supernova.{{cite journal |author=Hughes, D.W. |date=1980 |title=Did Flamsteed see the Cassiopeia A supernova? |journal=Nature |volume=285 |issue=5761 |pages=132–133 |bibcode=1980Natur.285..132H |doi=10.1038/285132a0 |s2cid=4257241 |doi-access=free}} Another suggestion from recent cross-disciplinary research is that the supernova was the "noon day star", observed in 1630, that was thought to have heralded the birth of Charles II, the future monarch of Great Britain.{{cite web |last=Oullette |first=Jennifer |title=Did supernova herald the birth of a king? |url=http://news.discovery.com/space/did-supernova-herald-birth-of-a-king-110417.html |publisher=Discovery.com |access-date=18 April 2011 |archive-date=29 September 2012 |archive-url=https://web.archive.org/web/20120929225132/http://news.discovery.com/space/did-supernova-herald-birth-of-a-king-110417.html |url-status=dead }}
However, it is more probable that the "noon day star" was the planet Venus that reached its maximum morning brightness two days earlier, allowing day time visibility in a clear sky. A bright supernova in Cassiopeia would have been visible for months and there would be more observation records as Cassiopeia is visible above the horizon any night in Europe.
No supernova occurring within the Milky Way has been visible to the naked eye from Earth since.
Expansion
The expansion shell has a temperature of around 30 million K, and is expanding at 4,000−6,000 km/s.
Observations of the exploded star through the Hubble Space Telescope have shown that, despite the original belief that the remnants were expanding in a uniform manner, there are high velocity outlying eject knots moving with transverse velocities of 5,500−14,500 km/s with the highest speeds occurring in two nearly opposing jets. When the view of the expanding star uses colors to differentiate materials of different chemical compositions, it shows that similar materials often remain gathered together in the remnants of the explosion.
Radio source
Cas A had a flux density of {{nowrap|2720 ± 50 Jy}} at 1 GHz in 1980.{{cite journal |author1=Baars, J.W.M. |author2=Genzel, R. |author3=Pauliny-Toth, I.I.K. |author4=Witzel, A. |title=The absolute spectrum of Cas A; an accurate flux density scale and a set of secondary calibrators |journal=Astronomy and Astrophysics |volume=61 |page=99 |date=1977 |bibcode=1977A&A....61...99B}} Because the supernova remnant is cooling, its flux density is decreasing. At 1 GHz, its flux density is decreasing at a rate of {{nowrap|0.97 ± 0.04 percent}} per year. This decrease means that, at frequencies below 1 GHz, Cas A is now less intense than Cygnus A. Cas A is still the brightest extrasolar radio source in the sky at frequencies above 1 GHz.
X-ray source
Although Cas X-1 (or Cas XR-1), the apparent first X-ray source in the constellation Cassiopeia was not detected during the 16 June 1964, Aerobee sounding rocket flight, it was considered as a possible source.{{cite conference |vauthors=Bowyer S, Byram ET, Chubb TA, Friedman H |chapter=Observational results of X-ray astronomy |title=Astronomical Observations from Space Vehicles, Proceedings from Symposium No. 23 Held in Liege, Belgium, 17 to 20 August 1964 |journal=Astronomical Observations from Space Vehicles |volume=23 |publisher=International Astronomical Union |editor=Steinberg JL |date=1965 |pages=227–239 |bibcode=1965IAUS...23..227B}} Cas A was scanned during another Aerobee rocket flight of 1 October 1964, but no significant X-ray flux above background was associated with the position.{{cite journal |vauthors=Fisher PC, Johnson HM, Jordan WC, Meyerott AJ, Acton LW |title=Observations of cosmic X-rays |journal=Astrophysical Journal |date=1966 |volume=143 |pages=203–17 |bibcode=1966ApJ...143..203F |doi=10.1086/148491 |doi-access=free }} Cas XR-1 was discovered by an Aerobee rocket flight on 25 April 1965,{{cite journal |vauthors=Byram ET, Chubb TA, Friedman H |title=Cosmic X-ray sources, galactic and extragalactic |journal=Science |date=Apr 1966 |volume=152 |issue=3718 |pages=66–71 |url=http://www.sciencemag.org/cgi/content/abstract/152/3718/66 |doi=10.1126/science.152.3718.66 |pmid=17830233 |bibcode=1966Sci...152...66B|s2cid=122616358 }} at RA {{RA|23|21}} Dec {{DEC|+58|30}}.{{cite journal |vauthors=Friedman H, Byram ET, Chubb TA |title=Distribution and variability of cosmic X-ray sources |journal=Science |date=April 1967 |volume=156 |issue=3773 |pages=374–8 |url=http://www.sciencemag.org/cgi/content/abstract/156/3773/374 |doi=10.1126/science.156.3773.374 |pmid=17812381 |bibcode=1967Sci...156..374F|s2cid=29701462 }} Cas X-1 is Cas A, a Type II SNR at RA {{RA|23|18}} Dec {{Dec|+58|30}}.{{cite journal |author=Webber, W.R. |title=X-ray astronomy-1968 vintage |journal=Proceedings of the Astronomical Society of Australia |volume=1 |issue=4 |date=December 1968 |pages=160–164 |bibcode=1968PASA....1..160W |doi=10.1017/S1323358000011231|s2cid=119018154 |doi-access=free }}
The designations Cassiopeia X-1, Cas XR-1, Cas X-1 are no longer used, but the X-ray source is Cas A (SNR G111.7-02.1) at 2U 2321+58.
In 1999, the Chandra X-Ray Observatory found CXOU J232327.8+584842,{{cite simbad|title=CXOU J232327.8+584842|access-date=2020-03-03}} a central compact object that is the neutron star remnant left by the explosion.{{cite journal |last1=Elshamouty |first1=K.G. |last2=Heinke |first2=C.O. |last3=Sivakoff |first3=G.R. |last4=Ho |first4=W.C.G. |last5=Shternin |first5=P.S. |last6=Yakovlev |first6=D.G. |last7=Patnaude |first7=D.J. |last8=David |first8=L. |title=Measuring the cooling of the neutron star in Cassiopeia A with all Chandra X-Ray Observatory detectors |journal=Astrophysical Journal |volume=777 |issue=1| year=2013 |pages=22 |doi=10.1088/0004-637X/777/1/22 |arxiv=1306.3387 |bibcode=2013ApJ...777...22E|s2cid=17981919 }}
Supernova reflected echo
In 2005 an infrared echo of the Cassiopeia A explosion was observed on nearby gas clouds using Spitzer Space Telescope.{{Cite journal|last1=Krause|first1=Oliver|last2=Rieke|first2=George H.|last3=Birkmann|first3=Stephan M.|last4=Le Floc'h|first4=Emeric|last5=Gordon|first5=Karl D.|last6=Egami|first6=Eiichi|last7=Bieging|first7=John|last8=Hughes|first8=John P.|last9=Young|first9=Erick T.|last10=Hinz|first10=Joannah L.|last11=Quanz|first11=Sascha P.|date=June 2005|title=Infrared Echoes near the Supernova Remnant Cassiopeia A|journal= Science|language=en|volume=308|issue=5728|pages=1604–1606|doi=10.1126/science.1112035|pmid=15947181|issn=0036-8075|arxiv=astro-ph/0506186|bibcode=2005Sci...308.1604K|s2cid=21908980}} The infrared echo was also seen by IRAS and studied with the Infrared Spectrograph. Previously it was suspected that a flare in 1950 from a central pulsar could be responsible for the infrared echo. With the new data it was concluded that this is unlikely the case and that the infrared echo was caused by thermal emission by dust, which was heated by the radiative output of the supernova during the shock breakout.{{Cite journal|last1=Dwek|first1=Eli|last2=Arendt|first2=Richard G.|date=October 2008|title=Infrared Echoes Reveal the Shock Breakout of the Cas A Supernova|journal=Astrophysical Journal|language=en|volume=685|issue=2|pages=976–987|doi=10.1086/589988|arxiv=0802.0221|bibcode=2008ApJ...685..976D|issn=0004-637X|doi-access=free}} The infrared echo is accompanied by a scattered light echo. The recorded spectrum of the optical light echo proved the supernova was of Type IIb, meaning it resulted from the internal collapse and violent explosion of a massive star, most probably a red supergiant with a helium core which had lost almost all of its hydrogen envelope. This was the first observation of the light echo of a supernova whose explosion had not been directly observed which opens up the possibility of studying and reconstructing past astronomical events.{{cite journal|last1=Krause|first1=Oliver|last2=Birkmann|last3=Usuda|last4=Hattori|last5=Goto|last6=Rieke|last7=Misselt|display-authors=3|date=2008|title=The Cassiopeia A supernova was of Type IIb|journal=Science|volume=320|issue=5880|pages=1195–1197|arxiv=0805.4557|bibcode=2008Sci...320.1195K|doi=10.1126/science.1155788|pmid=18511684|s2cid=40884513}}{{cite journal |last=Fabian |first=Andrew C. |title=A blast from the past |journal=Science |department=Astronomy |volume=320 |issue=5880 |date=2008 |pages=1167–1168 |doi=10.1126/science.1158538 |pmid=18511676|s2cid=206513073 }} In 2011 a study used spectra from different positions of the light echo to confirm that the Cassiopeia A supernova was asymmetric.{{Cite journal|last1=Rest|first1=A.|last2=Foley|first2=R. J.|last3=Sinnott|first3=B.|last4=Welch|first4=D. L.|last5=Badenes|first5=C.|last6=Filippenko|first6=A. V.|last7=Bergmann|first7=M.|last8=Bhatti|first8=W. A.|last9=Blondin|first9=S.|last10=Challis|first10=P.|last11=Damke|first11=G.|date=May 2011|title=Direct Confirmation of the Asymmetry of the Cas A Supernova with Light Echoes|journal=Astrophysical Journal|language=en|volume=732|issue=1|pages=3|doi=10.1088/0004-637X/732/1/3|issn=0004-637X|arxiv=1003.5660|bibcode=2011ApJ...732....3R|s2cid=119266059}}
Phosphorus detection
In 2013, astronomers detected phosphorus in Cassiopeia A, which confirmed that this element is produced in supernovae through supernova nucleosynthesis. The phosphorus-to-iron ratio in material from the supernova remnant could be up to 100 times higher than in the Milky Way in general.{{Cite journal |last1=Koo |first1=B.-C. |last2=Lee |first2=Y.-H. |last3=Moon |first3=D.-S. |last4=Yoon |first4=S.-C. |last5=Raymond |first5=J.C. |title=Phosphorus in the young supernova remnant Cassiopeia A |doi=10.1126/science.1243823 |journal=Science |volume=342 |issue=6164 |pages=1346–1348 |year=2013 |pmid=24337291 |arxiv=1312.3807 |bibcode=2013Sci...342.1346K|s2cid=35593706 }}
Gallery
{{gallery|mode=nolines
|File:Cassiopeia A infrared echo (complete).jpg|Cassiopeia A infrared echo as seen by unWISE. The observation time in this image ranges from 2015 (red) to 2020 (blue). The infrared echo appears as rainbow colored clouds. North is up.
|File:Ghostly Stellar Echoes in Supernova Remnant Cassiopeia A.jpg|The infrared echo caused by the Cassiopeia A supernova seen by Spitzer. The image was processed in a way that the infrared echo appears colored while dust clouds remain grey. North is on the left.
|File:CassiopeiaA Supernova Remnant Nebula from the Mount Lemmon SkyCenter Schulman Telescope courtesy Adam Block.jpg|Cassiopeia A seen by the 24-inch Ritchey-Chrétien reflector at the Mount Lemmon Observatory
|Image:heic0609.jpg|Cassiopeia A observed by the Hubble Space Telescope
|File:HEAO-2 Image of the Supernova Remnant Cassiopeia A Taken by the High Energy Astronomy Observatory 8003547.jpg|x-ray image of Cassiopeia A taken with the Einstein Observatory
|File:Cassiopeia A First Light (Chandra).jpg|Cassiopeia A was the first light image of the Chandra X-ray Observatory
|File:Cas A (NIRCam image) (weic2330a).jpg|Near-Infrared Camera (NIRCam) image of Cassiopeia A
|File:Cassiopeia A (MIRI Image) (2023-121-01GWQBBY77MHGFV3M3N63KDCEJ).png|Cassiopeia A observed by the JWST's Mid-Infrared Instrument (MIRI)
|File:Dust and Gas in Supernova Remnant.jpg|Cassiopeia A seen by Spitzer and showing different chemical elements and dust within the supernova remnant
}}
See also
References
{{reflist|2}}
External links
{{Commons category|Cassiopeia A}}
- {{cite journal |last1=Arcand |first1=Kimberly K. |author1-link=Kimberly Arcand |last2=Jiang |first2=Elaine |last3=Price |first3=Sara |last4=Watzke |first4=Megan |last5=Sgouros |first5=Tom |last6=Edmonds |first6=Peter |date=2018-12-15 |title=Walking through an exploded star: Rendering supernova remnant Cassiopeia A into virtual reality |journal=Communicating Astronomy with the Public Journal |volume=24 |page=17 |arxiv=1812.06237 |bibcode=2018CAPJ...24...17A |df=dmy-all}}
- {{cite news |url=http://news.bbc.co.uk/2/hi/uk_news/wales/7814351.stm |title=3D visualisation of Cassiopeia A |work=BBC News}}
- {{cite news |url=https://sketchfab.com/3d-models/supernova-remnant-cassiopeia-a-99219993de9f4f0e811abd56dce6d288|title=Virtual reality and augmented reality model viewer to explore a 3D hydrodynamic model of supernova remnant Cassiopeia A |publisher=Sketchfab; INAF-Osservatorio Astronomico di Palermo (S. Orlando)}}
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Category:Cassiopeia (constellation)