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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.
SNR B0102-72.3
SNR B0102-72.3, also cataloged as 1E 0102.2-7219 and known as E0102, is a young oxygen-rich supernova remnant in the Small Magellanic Cloud, about 190,000 light years from Earth.
SNR G006.4-00.1
SNR G006.4-00.1, also known as W28, is a supernova remnant in Sagittarius, about 40,000 years old, that illuminates nearby molecular clouds with escaping cosmic rays.
SNR G021.5-00.9
SNR G021.5-00.9, also written G21.5−0.9, is a young, Crab-like supernova remnant in Scutum powered by the pulsar PSR J1833−1034, about 870 years old, and a routine X-ray calibration target.
SNR G029.7-00.3
SNR G029.7-00.3, also known as Kesteven 75 or Kes 75, is a young composite supernova remnant in Aquila about 480 years old, with no historical record of its explosion.
SNR G031.9+00.0
SNR G031.9+00.0, also known as 3C 391, is a thermal composite Galactic supernova remnant about 7.1 kpc from the Sun, a prototype of remnants interacting with a molecular cloud.
SNR G034.6-00.5
SNR G034.6-00.5, also known as W44 or 3C 392, is a mixed-morphology supernova remnant in Aquila, discovered in 1958, with a radio shell, bright interior X-rays, and a pulsar.
SNR G039.7-02.0
SNR G039.7-02.0, also known as W50, is a large, elongated radio nebula in Aquila, widely cataloged as a supernova remnant, that hosts the microquasar SS 433.
SNR G315.0-02.3
SNR G315.0-02.3, also cataloged as RCW 86, is a large Galactic supernova remnant in Circinus, widely identified with supernova SN 185, recorded by Chinese astronomers in 185 AD.
SNR G347.3-00.5
SNR G347.3-00.5, also cataloged as RX J1713.7−3946, is a young shell-type supernova remnant in Scorpius, about 1 kpc away, linked to a supernova observed in 393 CE.
SNR J052559-660453
SNR J052559-660453, better known as N49 or DEM L 190, is a bright supernova remnant in the Large Magellanic Cloud hosting the magnetar SGR 0526-66.
Soft gamma repeater
A soft gamma repeater (SGR) is a neutron star that emits sporadic bursts of soft gamma rays, generally understood to be a magnetar with a magnetic field of roughly 10^14 to 10^15 gauss.
Solar-like oscillations
Solar-like oscillations are acoustic modes in stars stochastically driven by turbulent convection, like the Sun's; two measured numbers yield a star's mass, radius, and age, making them a workhorse of asteroseismology.
Sombrero Galaxy
The Sombrero Galaxy (Messier 104, NGC 4594) is a nearly edge-on galaxy about 30 million light-years away in Virgo, named for its brilliant bulge ringed by a dark dust lane.
South Pole Wall
The South Pole Wall is a filamentary structure of galaxies about 1.4 billion light-years long, discovered in 2020 behind the dust-obscured southern sky and comparable to the Sloan Great Wall at half the distance.
Southern Ring Nebula
NGC 3132, the Southern Ring Nebula or Eight-Burst Nebula, is a planetary nebula in Vela about 2,500 light-years away, thrown off by a dying star.
Spectroscopic binary
A spectroscopic binary is a pair of stars orbiting too closely to resolve in a telescope, identified by periodic Doppler shifts in its combined spectrum, first recognized in 1889.
Spica
Spica (Alpha Virginis) is the brightest star in Virgo, a blue-white binary of two massive B-type stars orbiting every 4.0145 days, about 250 light-years away.
Spider pulsar
A spider pulsar is a millisecond pulsar in a tight binary orbit whose wind strips, or ablates, its low-mass companion, dividing into black widows and redbacks.
Spiral arm
A spiral arm is a region of denser gas, dust, and young stars winding outward from the center of a disk galaxy, giving spiral galaxies their pinwheel appearance.
Spiral galaxy
A spiral galaxy is a galaxy with a rotating disk of stars, gas, and dust arranged in spiral arms around a central bulge, like the Milky Way.
SR 12 AB
SR 12 AB is a young K4+M2.5 T Tauri binary in the rho Ophiuchus cloud, about 125 pc away, hosting SR 12 AB c, a directly imaged 13-Jupiter-mass companion at roughly 1000 au with an ALMA-detected circumplanetary disk.
SS 433
SS 433, also cataloged as V1343 Aquilae, is an eclipsing X-ray binary in the constellation Aquila, about 5.5 kiloparsecs away, and the first microquasar discovered in the Galaxy.
SS Cygni
SS Cygni is the brightest dwarf nova in the sky, a close binary in Cygnus where a white dwarf accretes from a companion and erupts roughly every 50 days.
Standard solar model
The standard solar model is a calibrated, one-dimensional mathematical description of the Sun's interior, evolved to its present age of 4.57 billion years and used as the reference for solar neutrino fluxes and helioseismology.