A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek galaxias (γαλαξίας), literally 'milky', a reference to the Milky Way galaxy that contains the Solar System. Galaxies, averaging an estimated 100 million stars, range in size from dwarfs with less than a thousand stars, to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass visible in the form of stars and nebulae. Supermassive black holes are a common feature at the centres of galaxies.
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area about 2.6 arcminutes on a side, about one 24-millionth of the whole sky, which is equivalent in angular size to a tennis ball at a distance of 100 metres. The image was assembled from 342 separate exposures taken with the Space Telescope's Wide Field and Planetary Camera 2 over ten consecutive days between December 18 and 28, 1995.
A barred spiral galaxy is a spiral galaxy with a central bar-shaped structure composed of stars. Bars are found in about two thirds of all spiral galaxies in the local universe, and generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well. The Milky Way Galaxy, where the Solar System is located, is classified as a barred spiral galaxy.
Amy J. Barger is an American astronomer and Henrietta Leavitt Professor of Astronomy at the University of Wisconsin–Madison. She is considered a pioneer in combining data from multiple telescopes to monitor multiple wavelengths and in discovering distant galaxies and supermassive black holes, which are outside of the visible spectrum. Barger is an active member of the International Astronomical Union.
Luminous infrared galaxies or LIRGs are galaxies with luminosities, the measurement of brightness, above 1011 L☉. They are also referred to as submillimeter galaxies (SMGs) through their normal method of detection. LIRGs are more abundant than starburst galaxies, Seyfert galaxies and quasi-stellar objects at comparable luminosity. Infrared galaxies emit more energy in the infrared than at all other wavelengths combined. A LIRG's luminosity is 100 billion times that of the Sun.
APM 08279+5255 is a very distant, broad absorption line quasar located in the constellation Lynx. It is magnified and split into multiple images by the gravitational lensing effect of a foreground galaxy through which its light passes. It appears to be a giant elliptical galaxy with a supermassive black hole and associated accretion disk. It possesses large regions of hot dust and molecular gas, as well as regions with starburst activity.
A low-ionization nuclear emission-line region (LINER) is a type of galactic nucleus that is defined by its spectral line emission. The spectra typically include line emission from weakly ionized or neutral atoms, such as O, O+, N+, and S+. Conversely, the spectral line emission from strongly ionized atoms, such as O++, Ne++, and He+, is relatively weak. The class of galactic nuclei was first identified by Timothy Heckman in the third of a series of papers on the spectra of galactic nuclei that were published in 1980.
A Pea galaxy, also referred to as a Pea or Green Pea, might be a type of luminous blue compact galaxy that is undergoing very high rates of star formation. Pea galaxies are so-named because of their small size and greenish appearance in the images taken by the Sloan Digital Sky Survey (SDSS).
Lyman-break galaxies are star-forming galaxies at high redshift that are selected using the differing appearance of the galaxy in several imaging filters due to the position of the Lyman limit. The technique has primarily been used to select galaxies at redshifts of z = 3–4 using ultraviolet and optical filters, but progress in ultraviolet astronomy and in infrared astronomy has allowed the use of this technique at lower and higher redshifts using ultraviolet and near-infrared filters.
HXMM01, known more formally as 1HERMES S250 J022016.5−060143, is a starburst galaxy located in the northwestern portion of the constellation Cetus. Discovered in 2013 by a team at the University of California, Irvine, it was discovered that HXMM01 is actually still forming from its two parent galaxies as part of the "brightest, most luminous and most gas-rich submillimeter-bright galaxy merger known." When the merger is complete, HXMM01 will rapidly evolve to become a giant elliptical galaxy with a mass about four times that of the Milky Way. As of 2013, HXMM01 has been observed to form about 2,000 M☉ of stars every year, with an efficiency ten times greater than that of typical galaxies and far more than the Milky Way's 0.68–1.45 M☉ per year.
HFLS3 is the name for a distant galaxy at z = 6.34, originating about 880 million years after the Big Bang. Its discovery was announced on 18 April 2013 as an exceptional starburst galaxy producing nearly 3,000 solar masses of stars a year. It was found using the far-infrared-capable Herschel Space Telescope. The galaxy was estimated to have 35 billion stars. It is 10–30 times the mass of other known galaxies at such an early time in the universe.
Alice Eve Shapley is a professor at the University of California, Los Angeles (UCLA) in the Department of Physics and Astronomy. She was one of the discoverers of the spiral galaxy BX442. Through her time at University of California, Los Angeles (UCLA) she has taught Nature of the Universe, Black Holes and Cosmic Catastrophes, Cosmology: Our Changing Concepts of the Universe, Galaxies, Scientific Writing, AGNs, Galaxies, *and* Writing, and The Formation and Evolution of Galaxies and the IGM. Shapley has committed herself to over a two decades of research and publication in the interest of physics and astronomy.
Haro 11 (H11) is a small galaxy at a distance of 300,000,000 light-years (redshift z=0.020598). It is situated in the southern constellation of Sculptor. Visually, it appears to be an irregular galaxy, as the ESO image to the right shows. H11 is named after Guillermo Haro, a Mexican astronomer who first included it in a study published in 1956 about blue galaxies. H11 is a starburst galaxy that has 'super star clusters' within it and is one of nine galaxies in the local universe known to emit Lyman continuum photons (LyC).
Peter Lawrence Capak is currently the Architect of Perception Systems at the Oculus division of Facebook. His current focus is developing machine perception technologies, sensors, displays, and compute architectures for the next generation of augmented (AR), mixed (MR) and virtual reality (VR) systems. His research has focused on using physical modeling and advanced statistical methods including artificial intelligence and machine learning to extract information from very large multi-wavelength (hyper-spectral) data sets. He has primarily used this to study structure formation in the universe, cosmology, and the nature of dark matter and dark energy.
Rosemary Theresa Coogan is an astrophysicist and UK astronaut from Northern Ireland. Her research considers galaxy evolution and space-based telescopes. She is part of ESA's European Astronaut Corps.
Jeyhan Sevim Kartaltepe is an American astronomer, Associate Professor and Director of the Rochester Institute of Technology Laboratory for Multiwavelength Astrophysics. Her research considers observational astronomy and galaxy evolution. She is a lead investigator on the Cosmic Evolution Early Release Science Survey and the COSMOS-Webb Survey conducted on the James Webb Space Telescope.
Maisie's Galaxy is a distant galaxy located at z=11.4 that existed 390 million years after the beginning of the universe.
The COSMOS field, or the Cosmic Evolution Survey Deep Field, is a stitched photograph of deep space, which was photographed with the Hubble Space Telescope's Advanced Camera for Surveys in segments from 2003 to 2005, and was supported by several other ground-based and space-based telescopes. It was the capstone of the COSMOS project, which aimed to observe and study how galaxies are affected by celestial environments.
