640 articles
Atacama Large Millimeter/submillimeter Array
The Atacama Large Millimeter/submillimeter Array (ALMA) is a radio observatory of 66 antennas on the Chajnantor Plateau in Chile's Atacama Desert, observing star formation and distant galaxies.
Atmospheric super-rotation
Atmospheric super-rotation is when a planet's atmosphere circulates faster than the planet rotates. It occurs permanently on Venus, Titan, Jupiter, Saturn, and some hot Jupiters.
Australian Square Kilometre Array Pathfinder
The Australian Square Kilometre Array Pathfinder (ASKAP) is a radio telescope of 36 dish antennas operated by CSIRO in Western Australia, and a Square Kilometre Array precursor.
Axis of evil (cosmology)
The axis of evil, also called the ecliptic alignment anisotropy of the CMB, is a claimed alignment of large-scale cosmic microwave background patterns, named in 2005.
B-mode polarization
B-mode polarization is the curl-like, handed component of the cosmic microwave background's polarization, a distinctive fingerprint of primordial gravitational waves from inflation, with dust and lensing as contaminants.
Baldwin effect
The Baldwin effect is the anticorrelation in quasars and active galactic nuclei where emission lines weaken as continuum luminosity rises, first reported by Jack Baldwin in 1977.
Baryogenesis
Baryogenesis is the hypothetical physical process in the early universe that generated a small excess of baryons over antibaryons, producing all the matter in today's cosmos.
Baryon asymmetry
Baryon asymmetry is the excess of matter over antimatter in the universe, quantified by the baryon-to-photon ratio and generated by baryogenesis in the early universe.
Benjamin Banneker
Benjamin Banneker, also known as Ben Banneker, was a free African American astronomer, mathematician, and surveyor in Maryland who published almanacs from 1792 to 1797.
BICEP / Keck Array
BICEP / Keck Array is a series of cosmic microwave background polarization experiments at the South Pole, searching for primordial gravitational waves from cosmic inflation.
Big Bang
The Big Bang, or Big Bang model, is the prevailing cosmological theory in which the universe expanded and cooled from an extremely hot, dense state 13.8 billion years ago.
Big Bang nucleosynthesis
Big Bang nucleosynthesis, also called primordial nucleosynthesis, is the production of the lightest nuclei, chiefly helium-4, deuterium, helium-3, and lithium-7, during the universe's first minutes of cosmic time.
Big Bounce
The Big Bounce, also called the cosmic bounce, is a hypothetical cosmological model in which a contracting universe rebounds into expansion, replacing the big bang singularity.
Big Crunch
The Big Crunch is a hypothetical end of the universe in which cosmic expansion stops and reverses, and all matter collapses back into a hot, dense final state.
Big Ring
The Big Ring is a ring-shaped large-scale structure of galaxies about 1.3 billion light-years in diameter, found near Boötes at redshift 0.8 and reported in 2024 by Alexia Lopez.
Big Rip
The Big Rip is a hypothetical future singularity named by Robert Caldwell in 2003, in which phantom dark energy accelerates expansion without limit, tearing apart galaxies, stars, and eventually atoms.
Biosignature
A biosignature is any characteristic, element, or feature usable as evidence of past or present life, whose value depends on how unlikely nonbiological processes could produce it.
BL Lacertae
BL Lacertae (BL Lac) is the prototype blazar, an active galactic nucleus whose jet points almost at Earth. It was mistaken for a variable star when found in 1929.
BL Lacertae object
A BL Lacertae object (BL Lac, or BLL) is an active galactic nucleus with weak or no emission lines, one of the two blazar classes, named after BL Lacertae.
Black Hole Explorer
Black Hole Explorer, or BHEX, is a proposed NASA space VLBI mission to image supermassive black holes like M87 and measure the photon ring, targeted for launch in 2031.
Black hole feedback
Black hole feedback is the transfer of energy from an accreting supermassive black hole to gas in its host galaxy, altering star formation and black hole growth.
BlackGEM
BlackGEM is an array of three 65-cm optical survey telescopes at ESO's La Silla Observatory in Chile, built to find the visible light from neutron-star mergers detected by gravitational-wave detectors like LIGO.
Blazar
A blazar is an active galactic nucleus whose relativistic jet points almost directly at Earth, making it the most numerous identified gamma-ray source in the sky.
Boltzmann solver
A Boltzmann solver is a numerical code integrating the Einstein–Boltzmann equations to compute cosmic microwave background spectra and the matter power spectrum of cosmological models.
Breakthrough Listen
Breakthrough Listen is a privately funded ten-year astronomical program launched in 2015 with $100 million from Yuri Milner, using major radio telescopes to search for technosignatures from extraterrestrial technology.
Broad absorption line quasar
A broad absorption line quasar is a quasar whose ultraviolet spectrum shows broad absorption troughs from fast gas outflows, about 10 to 15 percent of optically selected quasars.
Broad-line region
The broad-line region is the zone of dense gas a few light-days from an active galactic nucleus's supermassive black hole, producing broad emission lines used to measure black hole masses.
Canadian Hydrogen Intensity Mapping Experiment
The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a radio telescope at Penticton, British Columbia, commissioned in 2017 to map hydrogen and detect fast radio bursts.
Cancer Cluster (galaxy cluster)
The Cancer Cluster is a nearby galaxy cluster in the constellation Cancer, famously studied by Fritz Zwicky in 1950, who found it highly spherical with bright galaxies concentrated toward its center.
CARMENES
CARMENES is a dual-channel échelle spectrograph on the 3.5 m telescope at the Calar Alto Observatory in Spain, built to detect low-mass planets around M dwarf stars.