All articles A–Z
519,064 articles
SN 1991bg
SN 1991bg was a strongly subluminous, peculiar Type Ia supernova that exploded in 1991 in the elliptical galaxy NGC 4374 in the Virgo cluster, giving its name to a subclass.
SN 1991T
SN 1991T was a peculiar, luminous Type Ia supernova discovered in April 1991 in the spiral galaxy NGC 4527, the prototype of the 1991T-like subclass of Type Ia supernovae.
SN 1993J
SN 1993J was a Type IIb supernova discovered on 28 March 1993 in the nearby galaxy M81, and the first supernova whose progenitor came from a binary system.
SN 1994D
SN 1994D was a Type Ia supernova that exploded in NGC 4526, a lenticular galaxy in the Virgo cluster, and became one of the best-observed supernovae of its type.
SN 1998bw
SN 1998bw is an unusually energetic Type Ic supernova discovered in April 1998 in the spiral galaxy ESO 184-G82, and the first supernova linked to a gamma-ray burst, GRB 980425.
SN 1998S
SN 1998S was a Type IIn supernova discovered in the galaxy NGC 3877 in March 1998, one of the brightest and best-studied examples of its class.
SN 1999em
SN 1999em was a Type II-plateau core-collapse supernova discovered in October 1999 in the nearby spiral galaxy NGC 1637, and became one of the most thoroughly observed of its type.
SN 2002ap
SN 2002ap was an energetic Type Ic supernova, or hypernova, discovered in January 2002 by Japanese amateur astronomer Yoji Hirose in the nearby spiral galaxy M74.
SN 2003dh
SN 2003dh was a Type Ic hypernova that appeared in March 2003 in the afterglow of GRB 030329, giving the first spectroscopic confirmation that some gamma-ray bursts come from supernovae.
SN 2003du
SN 2003du was a normal Type Ia supernova discovered in April 2003 in the nearby spiral galaxy UGC 9391, and among the most thoroughly observed nearby Type Ia events.
SN 2003lw
SN 2003lw is a broad-lined Type Ic supernova discovered in December 2003 in the host galaxy of gamma-ray burst GRB 031203, one of the nearest burst-supernova pairs known.
SN 2004et
SN 2004et was a Type IIP core-collapse supernova discovered in the spiral galaxy NGC 6946 on September 27, 2004, one of the nearest and best observed of its type.
SN 2005cs
SN 2005cs was a subluminous Type II-plateau supernova in the Whirlpool Galaxy, M51, discovered in June 2005 by German amateur astronomer Wolfgang Kloehr, with a low-mass red supergiant progenitor.
SN 2005nc
SN 2005nc is a type Ic supernova discovered on May 30, 2005, in the afterglow of gamma-ray burst GRB 050525A, one of the spectroscopically confirmed supernova–gamma-ray-burst associations.
SN 2006aj
SN 2006aj is a Type Ic supernova discovered in February 2006 in association with the low-luminosity X-ray flash XRF 060218, about 440 million light-years away in the constellation Aries.
SN 2006gy
SN 2006gy was an extremely luminous Type IIn supernova in the galaxy NGC 1260, about 240 million light-years away, the most luminous supernova recorded up to that time.
SN 2006jc
SN 2006jc is a peculiar Type Ib core-collapse supernova in galaxy UGC 4904, discovered by Koichi Itagaki in 2006 and the prototype of the Type Ibn class.
SN 2008D
SN 2008D is a Type Ib core-collapse supernova in the spiral galaxy NGC 2770, discovered on 9 January 2008 when Swift caught its X-ray shock breakout.
SN 2009ip
SN 2009ip was a transient in the galaxy NGC 7259, discovered in 2009 and long debated as a supernova or a supernova impostor, with its progenitor now gone.
SN 2010jl
SN 2010jl was a luminous Type IIn supernova discovered on 2 November 2010 in the irregular galaxy UGC 5189A, about 160 million light years from Earth.
SN 2011dh
SN 2011dh was a Type IIb core-collapse supernova that exploded in the Whirlpool Galaxy, Messier 51, in 2011; its yellow supergiant progenitor was identified in pre-explosion images.
SN 2011fe
SN 2011fe was a Type Ia supernova discovered on 24 August 2011 in the spiral galaxy Messier 101 in Ursa Major, the nearest Type Ia since 1986.
SN 2013cq
SN 2013cq is a broad-lined Type Ic supernova that accompanied the exceptionally energetic gamma-ray burst GRB 130427A, identified in 2013 at redshift 0.34 through excess flux in the burst's afterglow light curve.
SN 2014J
SN 2014J is a Type Ia supernova discovered on January 21, 2014, in Messier 82, about 12 million light-years away and the nearest Type Ia since 1986.
SN-38
SN-38, also known as 7-ethyl-10-hydroxycamptothecin, is the active metabolite of the anticancer drug irinotecan and the cytotoxic payload of the antibody-drug conjugate sacituzumab govitecan (Trodelvy).
Sn-Beta zeolite
Sn-Beta zeolite, also written Snβ or Sn-BEA, is a water-tolerant Lewis acid catalyst in which tin replaces some silicon in the Beta framework, first synthesized in 1997.
Sn-Ge alloyed perovskites
Sn-Ge alloyed perovskites are lead-free halide perovskites of form ASn1−xGexX3, where germanium partially replaces tin; the native GeO2 layer they form passivates surfaces, with best devices near 8% efficiency.
SN1 reaction
The SN1 reaction, or unimolecular nucleophilic substitution, is a two-step nucleophilic substitution that proceeds through a carbocation intermediate. Its rate depends only on substrate concentration, so tertiary substrates react fastest.
SN2 reaction
The SN2 reaction, or bimolecular nucleophilic substitution, is a concerted organic reaction, formulated by Hughes and Ingold in 1937, in which a nucleophile attacks from behind a leaving group, inverting the stereochemistry.
Snaaib
Snaaib, or Menkhaure Snaaib, is an Egyptian king of the late Second Intermediate Period (c. 17th century BC) known only from a stela found at Abydos.