SCP 06F6

{{Short description|Astronomical object discovered in 2006}} {{Sky|14|32|27.42|+|33|32|25.1|1000000}} {{Infobox astronomical event}} '''SCP 06F6''' is (or was) an [[astronomical object]] of unknown type, discovered on 21 February 2006 in the constellation [[Boötes]]<ref name=ns>[https://www.newscientist.com/article/dn14738-space-firefly-resembles-no-known-object.html Space 'firefly' resembles no known object], ''New Scientist News'', 16 September 2008</ref> during a survey of [[galaxy cluster]] CL 1432.5+3332.8 with the [[Hubble Space Telescope]]'s [[Advanced Camera for Surveys]] Wide Field Channel.<ref name="barbary">Barbary et al.: [https://arxiv.org/abs/0809.1648v1 Discovery of an Unusual Optical Transient with the Hubble Space Telescope]; accepted September 8, 2008, for later publication in the [[Astrophysical Journal]]</ref>

According to research authored by Kyle Barbary of the [[Supernova Cosmology Project]], the object brightened over a period of roughly 100 days, reaching a peak intensity of [[apparent magnitude|magnitude]] 21; it then faded over a similar period.<ref name="barbary"/>

Barbary and colleagues report that the [[spectrum]] of light emitted from the object does not match known [[supernova]] types, and is dissimilar to any known [[phenomenon]] in the [[Sloan Digital Sky Survey]] database. The light in the blue region shows broad line features, while the red region shows continuous emission.<ref name="ST Mystery Object">[http://www.spacetelescope.org/updates/html/update0811.html Mystery object spied with Hubble] The European Homepage for the NASA/ESA Hubble Space Telescope November 2008 update</ref> The spectrum shows a handful of spectral lines, but when astronomers try to trace any one of them to an element the other lines fail to match up with any other known elements.<ref name="barbary"/>

Because of its uncommon spectrum, the team was not able to determine the distance to the object using standard [[redshift]] techniques; it is not even known whether the object is within or outside the [[Milky Way galaxy|Milky Way]].<ref name=ns/> Furthermore, no Milky Way star or external galaxy has been detected at this location,<ref name="barbary"/> meaning any source is very faint.

The European X-ray satellite ''[[XMM Newton]]'' made an observation in early August 2006 which appears to show an X-ray glow around SCP 06F6,<ref name="nature">[http://www.nature.com/news/2008/080919/full/news.2008.1122.html How they wonder what you are], ''Nature News'', 19 September 2008</ref> two orders of magnitude more luminous than that of supernovae.<ref name=gans>Gänsicke et al.: [https://arxiv.org/abs/0809.2562 SCP06F6: A carbon-rich extragalactic transient at redshift z~0.14]. Preprint, 2008.</ref>

Observations from the [[Palomar Transient Factory]], reported in 2009, indicate a redshift ''z'' = 1.189 and a peak magnitude of −23.5 absolute (comparable to [[SN2005ap]]), making SCP 06F6 one of the most luminous transient phenomena known as of that date.<ref name="Quimby">{{cite arXiv |eprint=0910.0059v1 |author1=Quimby |author2=Kulkarni |author3=Kasliwal |author3-link=Mansi Kasliwal|author4=Gal-Yam |author5=Arcavi |author6=Sullivan |author7=Nugent |author8=Thomas |author9=Howell |title=Mysterious transients unmasked as the bright blue death throes of massive stars |class=astro-ph.CO |date=2009}}</ref>

== Possible causes == Supernovae reach their maximum brightness in only 20 days, and then take much longer to fade away. Researchers had initially conjectured that SCP 06F6 might be an extremely remote supernova; relativistic time dilation might have caused a 20-day event to stretch out over a period of 100 days. But this explanation now seems unlikely.<ref name=ns/> Other conjectures that have been advanced involve a collision between a [[white dwarf]] and an [[asteroid]], or the collision of a white dwarf with a [[black hole]].<ref>[https://www.sciencedaily.com/releases/2009/01/090107175009.htm Star Light, Star Bright, Its Explanation Is Out Of Sight], ''Science Daily'', 8 January 2009</ref>

An analysis by a team from the [[University of Warwick]] (Boris Gänsicke et al.) suggests that the light spectrum is "consistent with emission from a cool, [[carbon]]-rich atmosphere at a [[redshift]] of z~0.14",<ref name=gans/> possibly representing the core collapse and explosion of a [[carbon star]].<ref name="nature"/> Gänsicke's group concurs with Barbary and colleagues that SCP 06F6 may represent "a new class" of [[celestial object]].<ref name="barbary"/><ref name=gans/>

The analysis of Israeli astronomers of [[Technion – Israel Institute of Technology|Technion]] suggests four alternative explanations for SCP 06F6, in plausibility order: the tidal destruction of a carbon-oxygen [[white dwarf]] by an [[intermediate-mass black hole]], a [[type Ia supernova|Type Ia]] [[supernova]] exploding inside the dense stellar wind of a [[carbon star]], an [[asteroid]] that was swallowed up by a white dwarf or, least likely, a [[Type II supernova|core-collapse supernova]].<ref>[https://arxiv.org/abs/0812.1402 "Galactic vs. Extragalactic Origin of the Peculiar Transient SCP 06F6"] Noam Soker, Adam Frankowski, Amit Kashi (Technion, Israel)</ref>

Observations in 2009 indicate that it may be a [[pair-instability supernova]].<ref name="Quimby"/>

The event was similar to [[SN 2005ap]], and other unusually bright supernova suggesting that it was a new type of supernova.<ref>{{cite journal|last1=Quimby|first1=R. M. |last2=Kulkarni |last3=Kasliwal|author3-link=Mansi Kasliwal |last4=Gal-Yam |display-authors=etal |title=Hydrogen-poor superluminous stellar explosions|journal=[[Nature (journal)|Nature]]|date=June 8, 2011|doi=10.1038/nature10095|arxiv = 0910.0059 |bibcode = 2011Natur.474..487Q |volume=474 |issue=7352 |pages=487–489 |pmid=21654747|s2cid=4333823 }}</ref>

== References == {{reflist}}

== External links == * [http://www.cbat.eps.harvard.edu/cbet/000500/CBET000546.txt CBET 546] * [https://www.newscientist.com/channel/astronomy/dn9360-enigmatic-object-baffles-supernova-team.html New Scientist's article from June 2006 when the object was first observed] * [https://www.newscientist.com/article/dn14738-space-firefly-resembles-no-known-object.html New Scientist's article from September 2008] * [https://www.newscientist.com/article/dn17262 New Sci June 2009] * [http://www.iop.org/EJ/abstract/1538-4357/697/2/L129 Astrophysical Journal: Boris T. Gänsicke et al, ''SCP 06F6: A CARBON-RICH EXTRAGALACTIC TRANSIENT AT REDSHIFT z ~ 0.14''. May, 2009]

[[Category:Supernovae]] [[Category:Discoveries by the Hubble Space Telescope]] [[Category:Astronomical objects discovered in 2006|20060221]] [[Category:Boötes]] [[Category:Unsolved problems in astronomy]]