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Megamaser Cosmology Project
The Megamaser Cosmology Project is an NRAO Key Science Project that measures the Hubble constant through geometric distances to water megamasers, independent of the distance ladder and the CMB.
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 60
Messier 60 (M60, NGC 4649) is a giant elliptical galaxy in the constellation Virgo and the third brightest member of the Virgo cluster, about 54 million light-years from Earth.
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.
Metal enrichment of the intergalactic medium
Metal enrichment of the intergalactic medium is the dispersal of heavy elements forged in stars into the gas between galaxies, measured mainly through absorption lines in quasar spectra.
Methods of detecting exoplanets
Methods of detecting exoplanets are the observational techniques astronomers use to find planets around other stars. Most detections are indirect, through transit photometry, radial velocity, astrometry, microlensing, and direct imaging.
Millennium Simulation
The Millennium Simulation, also called the Millennium Run, is a 2004 computer simulation of dark matter structure growth, run by the Virgo Consortium and published in 2005.
Mini-Neptune
A mini-Neptune, sometimes called a gas dwarf, is an exoplanet larger than Earth but smaller than Neptune, carrying a thick hydrogen- and helium-dominated atmosphere over ice or rock.
Modern Cosmology (book)
Modern Cosmology is a graduate-level cosmology textbook by Scott Dodelson, first published by Academic Press in 2003 and now in a third edition with Fabian Schmidt.
Modified Newtonian dynamics
Modified Newtonian dynamics (MOND), or Milgrom's law, is a proposed alternative to dark matter in which Newtonian mechanics breaks down at very low gravitational accelerations, proposed by Mordehai Milgrom in 1983.
Mount Wilson Observatory
Mount Wilson Observatory is an observatory on Mount Wilson near Pasadena, California, founded by George Ellery Hale in 1904 and home to the 100-inch Hooker telescope.
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.
Multi Unit Spectroscopic Explorer
The Multi Unit Spectroscopic Explorer (MUSE) is a panoramic integral-field spectrograph at the Very Large Telescope's Paranal Observatory in Chile, which saw first light in 2014.
Multi-object spectroscopy
Multi-object spectroscopy (MOS) is an observational technique in astronomy that records the spectra of many objects at once, using objective prisms, slit masks, or fiber-fed spectrographs, and underpinning large galaxy redshift surveys.
Murchison Widefield Array
The Murchison Widefield Array is a low-frequency radio interferometer at the Murchison Radio-astronomy Observatory in Western Australia, operating from 80 to 300 MHz as an official Square Kilometre Array precursor since 2013.
Nadir
The nadir is the point on the celestial sphere directly below an observer, exactly opposite the overhead zenith, and hidden from view by the ground.
Narrow band photometry
Narrow band photometry is an observational astronomy technique that measures an object's brightness through a filter passing only a small wavelength range, separating emission-line flux from the continuum.
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.
Natural inflation
Natural inflation is a model of cosmic inflation in which the inflaton is a pseudo Nambu-Goldstone boson with a cosine potential, proposed by Freese, Frieman, and Olinto in 1990.
Navarro–Frenk–White profile
The Navarro–Frenk–White (NFW) profile, proposed in 1996 by Julio Navarro, Carlos Frenk, and Simon White, is a formula for dark matter density inside halos and a standard model in lensing studies.
New inflation
New inflation is a cosmological model proposed in 1982 by Andrei Linde and independently by Albrecht and Steinhardt, in which a slowly rolling scalar field drives accelerated expansion.
NewAthena
NewAthena, short for New Advanced Telescope for High-ENergy Astrophysics, is a planned ESA X-ray observatory carrying the largest X-ray telescope ever built, with launch planned for the late 2030s.
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.