81 articles
M51-ULS-1
M51-ULS-1 is an ultraluminous supersoft X-ray source in the Whirlpool Galaxy, 28 million light-years away, host of M51-ULS-1b, the first candidate planet beyond the Milky Way.
Markarian 421
Markarian 421, or Mrk 421, is a nearby blazar, a giant elliptical galaxy with a jet aimed at Earth, first detected at TeV gamma rays in 1992 by the Whipple Observatory.
Markarian 501
Markarian 501, also known as Mrk 501, is a nearby blazar, a type of galaxy with a jet pointed at Earth, and a source of TeV gamma rays.
Messier 105
Messier 105 (M105, also known as NGC 3379) is an elliptical galaxy about 32 million light-years away in Leo and home to a supermassive black hole.
Messier 106
Messier 106, also cataloged as NGC 4258, is a Seyfert 2 spiral galaxy in Canes Venatici about 24 million light-years away, known for its anomalous arms driven by its central black hole.
Messier 61
Messier 61, also known as M61 or NGC 4303, is a barred spiral galaxy in the Virgo Cluster about 55 million light-years away, and has hosted the most observed supernovae of any Messier galaxy.
Messier 77
Messier 77, also known as NGC 1068, is a barred spiral galaxy in Cetus about 45 million light-years away, hosting one of the nearest active galactic nuclei.
Messier 84
Messier 84 (NGC 4374) is a giant elliptical galaxy in the Virgo Cluster, discovered by Charles Messier in 1781 and known for its central supermassive black hole.
Messier 89
Messier 89 (M89, NGC 4552) is an elliptical galaxy in the Virgo Cluster, about 50 million light-years away and notable for its almost perfectly circular appearance.
Mrk 1502
Mrk 1502, better known as I Zwicky 1 (I Zw 1), is a nearby narrow-line Seyfert 1 galaxy in an almost face-on spiral host at redshift 0.0589.
Mrk 335
Mrk 335, also known as Markarian 335, is a narrow-line Seyfert 1 galaxy about 324 million light-years away in Pegasus whose supermassive black hole drives unusually variable X-ray output.
Mrk 509
Mrk 509 (Markarian 509) is a bright Seyfert 1 galaxy in Aquarius, about 500 million light-years away, with a black hole of roughly 300 million solar masses.
Narrow-line region
The narrow-line region is the outer part of an active galactic nucleus, beyond the dust sublimation radius, where sparse gas moving a few hundred km/s emits narrow lines.
NGC 1052
NGC 1052 is an elliptical galaxy in the constellation Cetus, about 20 megaparsecs away, notable for a LINER active nucleus and a double-sided radio jet seen nearly edge-on.
NGC 1275
NGC 1275, also known as Perseus A and 3C 84, is the giant elliptical galaxy at the center of the Perseus cluster, a strong X-ray and radio source 230 million light-years away.
NGC 1316
NGC 1316, also known as Fornax A, is a lenticular galaxy in Fornax about 62 to 75 million light-years away and one of the strongest radio sources in the sky.
NGC 3227
NGC 3227 is a barred spiral galaxy with an active Seyfert nucleus in the constellation Leo, gravitationally interacting with its smaller elliptical companion NGC 3226.
NGC 3516
NGC 3516 is a nearby Seyfert 1 spiral galaxy, one of the original six in Carl Seyfert's class, with an active nucleus powered by a supermassive black hole.
NGC 3783
NGC 3783 is a bright barred spiral galaxy about 130 million light-years from Earth in the constellation Centaurus, hosting one of the best-studied active galactic nuclei in the southern sky.
NGC 4051
NGC 4051 is a barred spiral galaxy in Ursa Major, one of the six original Seyfert galaxies from Carl Seyfert's 1943 paper, known for its variable X-ray nucleus.
NGC 4151
NGC 4151 is a nearby barred spiral galaxy in the constellation Canes Venatici with a Seyfert 1.5 active nucleus, one of the nearest and brightest Seyfert galaxies.
NGC 4253
NGC 4253, also known as Markarian 766, is a Seyfert 1 barred spiral galaxy in the constellation Coma Berenices, one of the most frequently observed active galactic nuclei in X-ray astronomy.
NGC 4261
NGC 4261 is a giant elliptical galaxy in the Virgo Cluster region, best known for the spiral dust disk imaged by Hubble around its 1.6-billion-solar-mass black hole.
NGC 4388
NGC 4388 is a Seyfert 2 spiral galaxy in the Virgo Cluster, roughly 60 to 65 million light years away, and the brightest Seyfert 2 galaxy in hard X-rays.
NGC 4593
NGC 4593, also cataloged as Mrk 1330, is a barred spiral galaxy about 39 Mpc away with a Seyfert 1 active nucleus, discovered by William Herschel in 1784.
NGC 4636
NGC 4636 is a giant elliptical galaxy at the southern border of the Virgo cluster, about 47 to 50 million light years away, with a disturbed X-ray halo.
NGC 5506
NGC 5506 is a nearly edge-on spiral galaxy in Virgo whose Seyfert 2 nucleus was revealed in 2002 to be a dust-obscured narrow-line Seyfert 1.
NGC 5548
NGC 5548, also cataloged as Mrk 1509, is a nearby Seyfert 1 spiral galaxy whose nucleus hosts a rapidly accreting supermassive black hole about 79 megaparsecs away.
NGC 7469
NGC 7469 is a barred spiral Seyfert 1 galaxy in Pegasus about 220 million light-years away, one of the original six Seyfert galaxies, interacting with IC 5283.
OJ 287
OJ 287 is a blazar, a jet-pointed active galactic nucleus at redshift 0.306, and a leading binary black hole candidate whose optical outbursts recur about every 12 years.