what celestial object lies at the center of the milky way galaxy
Galactic Center
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Galactic Center The Galactic Center, or Galactic Centre, is the rotational center of the Milky Way. It is away from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius where the Milky Way appears brightest. It coincides with the compact radio source Sagittarius A*. There are around 10 million stars within one parsec of the Galactic Center, dominated by red giants. There is also a significant population of massive supergiants and Wolf-Rayet stars from a star formation event around one million years ago. There is a supermassive black hole of 4.100 ± 0.034 million solar masses at the
Galactic Center
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Galactic coordinate system The galactic coordinate system is a celestial coordinate system in spherical coordinates, with the Sun as its center, the primary direction aligned with the approximate center of the Milky Way galaxy, and the fundamental plane parallel to an approximation of the galactic plane but offset to its north. It uses the right-handed convention, meaning that coordinates are positive toward the north and toward the east in the fundamental plane. Longitude (symbol ) measures the angular distance of an object eastward along the galactic equator from the galactic center. Analogous to terrestrial longitude, galactic longitude is usually measured
Galactic coordinate system
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Galactocentrism In astronomy, Galactocentrism is the theory that the Milky Way Galaxy, home of Earths Solar System, is at or near the center of the Universe. Observations by William Herschel in 1785 suggested that the Milky Way was a disk-shaped galaxy with the sun in a central position. Although heliocentric, Herschel's observations were the first attempt at an observational cosmology. Herschel's heliocentric theory was overthrown by astronomer Harlow Shapley's work on globular clusters in 1918. Shapley's research marked the transition from heliocentrism to galactocentrism, placing the Galactic Center of the Milky Way Galaxy far away from the sun, towards Sagittarius.
Galactocentrism
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objects in our Galaxy - all of which are, in principle, observable quantities. However, there are a number of complications. The simple derivation above assumed that both the Sun and the object in question are traveling on circular orbits about the Galactic center. This is not true for the Sun (the Sun's velocity relative to the local standard of rest is approximately 13.4 km/s), and not necessarily true for other objects in the Milky Way either. The derivation also implicitly assumes that the gravitational potential of the Milky Way is axisymmetric and always directed towards the center. This ignores the
Oort constants
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in the Milky Way, as well as most of the Milky Way's star formation activity. Viewed from the Andromeda Galaxy, it would be the brightest feature of the Milky Way. The complex astronomical radio source Sagittarius A appears to be located almost exactly at the Galactic Center (approx. 18 hrs, −29 deg), and contains an intense compact radio source, Sagittarius A*, which coincides with a supermassive black hole at the center of the Milky Way. Accretion of gas onto the black hole, probably involving a disk around it, would release energy to power the radio source, itself much larger than
Galactic Center
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that other galaxies apart from the Milky Way therefore existed. By 1925, Edwin Hubble had confirmed that many objects previously thought to be clouds of dust and gas and classified as "nebulae" were actually galaxies beyond the Milky Way. When astronomers realized that starlight can be absorbed by clouds of gas and dust, infrared radiation was used to penetrate the dust clouds. Estimates dating after 2000 locate our solar system within the range from the Galactic Center of the Milky Way galaxy. Galactocentrism In astronomy, Galactocentrism is the theory that the Milky Way Galaxy, home of Earths Solar System, is
Galactocentrism
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mental attacks. Terminus (planet) Terminus is a fictional planet at the edge of the Galaxy in Isaac Asimov's "Foundation Series", home of the Foundation (later capital of the Foundation Federation). Terminus is the sole planet orbiting an isolated star. Its nearest inhabited neighbor is Anacreon, 8 parsecs (26 light years) away, and it lies approximately 10,000 parsecs from the capital of the First Galactic Empire, Trantor, near the galactic center. There are almost no visible stars in its sky, only the huge lens of the Milky Way Galaxy. The nearby stars of the Province of Anacreon are known as "The
Terminus (planet)
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Terminus (planet) Terminus is a fictional planet at the edge of the Galaxy in Isaac Asimov's "Foundation Series", home of the Foundation (later capital of the Foundation Federation). Terminus is the sole planet orbiting an isolated star. Its nearest inhabited neighbor is Anacreon, 8 parsecs (26 light years) away, and it lies approximately 10,000 parsecs from the capital of the First Galactic Empire, Trantor, near the galactic center. There are almost no visible stars in its sky, only the huge lens of the Milky Way Galaxy. The nearby stars of the Province of Anacreon are known as "The Diamonds", with
Terminus (planet)
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Galactic year The galactic year, also known as a cosmic year, is the duration of time required for the Sun to orbit once around the center of the Milky Way Galaxy. Estimates of the length of one orbit range from 225 to 250 million terrestrial years. The Solar System is traveling at an average speed of 828,000 km/h (230 km/s) or 514,000 mph (143 mi/s) within its trajectory around the galactic center, a speed at which an object could circumnavigate the Earth's equator in 2 minutes and 54 seconds; that speed corresponds to approximately 1/1300 of the speed of light.
Galactic year
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result is the first measurement of the beryllium content of two stars in a Milky Way globular cluster. With this measurement, astronomers found that the first generation of stars in our galaxy must have formed soon after the end of the 200-million-year "Dark Age" following the Big Bang. Astronomers long suspected that a black hole exists at the center of the Milky Way, but their theory was unproven. Conclusive evidence was obtained after 16 years of monitoring the Galactic Center with ESO telescopes at the La Silla and Paranal observatories. Stars at the centre of the Milky Way are so
European Southern Observatory
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Center. The Far 3 kpc Arm was discovered in 2008 by astronomer Tom Dame (Harvard-Smithsonian CfA). It is located in the first galactic quadrant at a distance of 3 kpc (about 10,000 ly) from the Galactic Center. A simulation published in 2011 suggested that the Milky Way may have obtained its spiral arm structure as a result of repeated collisions with the Sagittarius Dwarf Elliptical Galaxy. It has been suggested that the Milky Way contains two different spiral patterns: an inner one, formed by the Sagittarius arm, that rotates fast and an outer one, formed by the Carina and Perseus
Milky Way
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was detected in the Andromeda Galaxy. The progenitor black hole is located near the galactic center and has about 10 formula_1. Discovered through a data collected by the European Space Agency's XMM-Newton probe, and subsequently observed by NASA's Swift Gamma-Ray Burst Mission and Chandra X-Ray Observatory, the Very Large Array, and the Very Long Baseline Array, the microquasar was the first observed within the Andromeda Galaxy and the first outside of the Milky Way Galaxy. Like the Milky Way, the Andromeda Galaxy has satellite galaxies, consisting of 14 known dwarf galaxies. The best known and most readily observed satellite galaxies
Andromeda Galaxy
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that the Milky Way contained all the stars in the Universe. Following the 1920 Great Debate between the astronomers Harlow Shapley and Heber Curtis, observations by Edwin Hubble showed that the Milky Way is just one of many galaxies. The Milky Way is a barred spiral galaxy with a diameter between 150,000 and 200,000 light-years (ly). It is estimated to contain 100–400 billion stars and more than 100 billion planets. The Solar System is located at a radius of 26,490 (± 100) light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations
Milky Way
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Messier 79 Messier 79 (also known as M79 or NGC 1904) is a globular cluster in the constellation Lepus. It was discovered by Pierre Méchain in 1780 and is at a distance of about 42,000 light years away from Earth and 60,000 light years away from the Galactic Center. Like Messier 54 (the other extragalactic globular on Messier's list), it is thought that M79 is not native to the Milky Way galaxy at all, but instead to the putative Canis Major Dwarf Galaxy, which is currently experiencing a very close encounter with the Milky Way. This is, however, a contentious
Messier 79
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and the opening sequence from Earth through the Solar System and its galaxy and beyond for the "Contact" film. At Sagan's request, Lomberg designed the original sailing ship logo for the Planetary Society in 1981. The Smithsonian Institution commissioned Lomberg in the early 1990s to paint ""A Portrait of the Milky Way"", a scientifically accurate artistic representation of the Milky Way galaxy as seen by a hypothetical observer from a vantage point 10 degrees above the galactic plane and 60,000 light years from the galactic center. The by painting, which was described in a peer reviewed academic paper in 1994
Jon Lomberg
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Carina–Sagittarius Arm The Carina–Sagittarius Arm (also known as Sagittarius Arm or Sagittarius–Carina Arm, labeled "-I") is generally thought to be a minor spiral arm of the Milky Way galaxy. Each spiral arm is a long, diffuse curving streamer of stars that radiates from the galactic center. These gigantic structures are often composed of billions of stars and thousands of gas clouds. The Carina–Sagittarius Arm is one of the most pronounced arms in our galaxy as a large number of HII regions, young stars and giant molecular clouds are concentrated in it. The Milky Way is a barred spiral galaxy, consisting
Carina–Sagittarius Arm
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as Hubble's law, predicted by a universal expansion. The Milky Way Galaxy is moving through space and many astronomers believe the velocity of this motion to be approximately relative to the observed locations of other nearby galaxies. Another reference frame is provided by the Cosmic microwave background. This frame of reference indicates that the Milky Way is moving at around . The Milky Way is rotating around its dense galactic center, thus the sun is moving in a circle within the galaxy's gravity. Away from the central bulge, or outer rim, the typical stellar velocity is between . All planets
Motion (physics)
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such as toward the galactic plane or the galactic center). Because the Milky Way galaxy has a very flat structure, if gamma-ray bursts were to originate from within the Milky Way, they would not be distributed isotropically across the sky, but instead concentrated in the plane of the Milky Way. Although the luminosity of the bursts suggested that they had to be originating within the Milky Way, the distribution provided very strong evidence to the contrary. BATSE data also showed that GRBs fall into two distinct categories: short-duration, hard-spectrum bursts ("short bursts"), and long-duration, soft-spectrum bursts ("long bursts"). Short bursts
History of gamma-ray burst research
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present. Several Mormon authors have attempted to situate Kolob within modern astronomy. Skousen speculated that Kolob is a star at the Galactic Center, Sagittarius A*, of our own Galaxy. This view also had the support of several former general authorities of the LDS Church, including J. Reuben Clark and George Reynolds (with Janne M. Sjödahl). In the mid-19th century, early efforts to find a single "central sun" in the galaxy resulted in failure. Another Mormon author has hypothesized that Kolob exists outside the Milky Way Galaxy at a place called the "metagalactic center", and that this galaxy and other galaxies
Kolob
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fairly narrow range of distances from the Galactic Center. Lineweaver et al. calculate this zone to be a ring 7 to 9 kiloparsecs in radius, including no more than 10% of the stars in the Milky Way, about 20 to 40 billion stars. Gonzalez, et al. would halve these numbers; they estimate that at most 5% of stars in the Milky Way fall in the galactic habitable zone. Approximately 77% of observed galaxies are spiral, two-thirds of all spiral galaxies are barred, and more than half, like the Milky Way, exhibit multiple arms. According to Rare Earth, our own galaxy
Rare Earth hypothesis
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and halo is located at the centre of this galaxy. NGC 4244 NGC 4244, also Caldwell 26, is an edge-on loose Spiral galaxy and Caldwell object in the constellation Canes Venatici. It is part of the M94 Group (the Canes Venatici I Group), a galaxy group relatively close to the Local Group containing the Milky Way. It shines at magnitude +10.2/+10.6. Its celestial cooridinates are RA , dec . It is located near a naked-eye G-class star Beta Canum Venaticorum, barred spiral galaxy NGC 4151, and irregular galaxy NGC 4214. The galaxy lies approximately 6.5 million/14 million light years away,
NGC 4244
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NGC 4244 NGC 4244, also Caldwell 26, is an edge-on loose Spiral galaxy and Caldwell object in the constellation Canes Venatici. It is part of the M94 Group (the Canes Venatici I Group), a galaxy group relatively close to the Local Group containing the Milky Way. It shines at magnitude +10.2/+10.6. Its celestial cooridinates are RA , dec . It is located near a naked-eye G-class star Beta Canum Venaticorum, barred spiral galaxy NGC 4151, and irregular galaxy NGC 4214. The galaxy lies approximately 6.5 million/14 million light years away, with a redshift of +243/493 km/s. A nuclear star cluster
NGC 4244
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William Herschel on 9 September 1798, this well-studied galaxy has a diameter of approximately 40,000 light-years , about one-third of the Milky Way's size, and it contains roughly half the number of stars as the Milky Way. The galaxy is heavily obscured by interstellar matter as it lies quite close to the galactic plane of the Milky Way. Due to its prodigious star formation it has been classified as an active starburst galaxy. Various unusual celestial objects have been observed within NGC 6964. This includes the so-called 'Red Ellipse' along one of the northern arms that looks like a super-bubble
NGC 6946
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his view, the Milky Way is celestial. According to Mohani Mohamed, the Arabian astronomer Alhazen (965–1037) made the first attempt at observing and measuring the Milky Way's parallax, and he thus "determined that because the Milky Way had no parallax, it must be remote from the Earth, not belonging to the atmosphere." The Persian astronomer al-Bīrūnī (973–1048) proposed the Milky Way galaxy to be "a collection of countless fragments of the nature of nebulous stars." The Andalusian astronomer Ibn Bâjjah ("Avempace", 1138) proposed that the Milky Way is made up of many stars that almost touch one another and appear
Galaxy
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is now in a relative state of quiescence, whereas the Milky Way is experiencing more active star formation. Should this continue, the luminosity of the Milky Way may eventually overtake that of Andromeda Galaxy. According to recent studies, the Andromeda Galaxy lies in what in the galaxy color–magnitude diagram is known as the "green valley", a region populated by galaxies like the Milky Way in transition from the "blue cloud" (galaxies actively forming new stars) to the "red sequence" (galaxies that lack star formation). Star formation activity in green valley galaxies is slowing as they run out of star-forming gas
Andromeda Galaxy
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after the Andromeda Galaxy (M31), the Milky Way, and the Triangulum Galaxy (M33). The LMC is classified as a Magellanic spiral. It contains a stellar bar that is geometrically off-center, suggesting that it was a barred dwarf spiral galaxy before its spiral arms were disrupted, likely by tidal interactions from the Small Magellanic Cloud (SMC), and the Milky Way's gravity. With a declination of about -70°, the LMC is visible as a faint "cloud" only in the southern celestial hemisphere and from latitudes south of 20° N, straddling the border between the constellations of Dorado and Mensa, and appears longer
Large Magellanic Cloud
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Clouds may be moving too fast to be orbiting the Milky Way. Of the galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Elliptical Galaxy, which has a diameter of or roughly a fifth that of the Milky Way. Satellite galaxies that orbit from of the edge of the disc of the Milky Way Galaxy to the edge of the dark matter halo of the Milky Way at from the center of the galaxy, are generally depleted in hydrogen gas compared to those that orbit more distantly. This is because of their interactions with the dense hot
Satellite galaxies of the Milky Way
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Sculptor Dwarf Galaxy The Sculptor Dwarf Galaxy (also known as Sculptor Dwarf Elliptical Galaxy or the Sculptor Dwarf Spheroidal Galaxy) is a dwarf spheroidal galaxy that is a satellite of the Milky Way. The galaxy lies within the constellation Sculptor. It was discovered in 1937 by American astronomer Harlow Shapley using the 24-inch Bruce refractor at Boyden Observatory. The galaxy is located about 290,000 light-years away from the Solar System. The Sculptor Dwarf contains only 4 percent of the carbon and other heavy elements in our own galaxy, the Milky Way, making it similar to primitive galaxies seen at the
Sculptor Dwarf Galaxy
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revolution. Lynx's most notable deep sky object is NGC 2419, also called the "Intergalactic Wanderer" as it was assumed to lie outside the Milky Way. At a distance of between 275,000 and 300,000 light-years from Earth, it is one of the most distant known globular clusters within our galaxy. NGC 2419 is likely in a highly elliptical orbit around the Milky Way. It has a magnitude of 10.3 and is a Shapley class II cluster; this classification indicates that it is extremely concentrated at its center. Originally thought to be a star, NGC 2419 was discovered to be a globular
Lynx (constellation)
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showing less stellar density than current elliptical galaxies. It is, however, possible the resulting object will be a large disk galaxy, depending on the amount of remaining gas in the Milky Way and Andromeda. In the far future, roughly 150 billion years from now, the remaining galaxies of the Local Group will coalesce into this object, that being the next evolutionary stage of the local group of galaxies. Andromeda–Milky Way collision The Andromeda–Milky Way collision is a galactic collision predicted to occur in about 5 billion years between two galaxies in the Local Group—the Milky Way (which contains the Solar
Andromeda–Milky Way collision
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been described by a member of the team that discovered it as "a rather pathetic galaxy" in comparison to the Milky Way. Many of the stars have been known for centuries and thought of as normal Milky Way stars, although they have a lower metallicity than normal Population I stars in the Milky Way. The stream lies within the Milky Way, approximately 10 kiloparsecs (30,000 light-years) from the Sun, and extending over a region of space at least 10 kpc across in three dimensions. It is close on the plane of the sky to the Sagittarius Dwarf Elliptical Galaxy, which
Virgo Stellar Stream
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optical astronomical maps, Jansky concluded that the radiation was coming from the Milky Way Galaxy and was strongest in the direction of the center of the galaxy, in the constellation of Sagittarius. An amateur radio operator, Grote Reber, was one of the pioneers of what became known as radio astronomy. He built the first parabolic "dish" radio telescope, in diameter, in his back yard in Wheaton, Illinois in 1937. He repeated Jansky's pioneering work, identifying the Milky Way as the first off-world radio source, and he went on to conduct the first sky survey at very high radio frequencies, discovering
Radio telescope
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as magnitude 7. Cetus lies far from the galactic plane, so that many distant galaxies are visible, unobscured by dust from the Milky Way. Of these, the brightest is Messier 77 (NGC 1068), a 9th magnitude spiral galaxy near Delta Ceti. It appears face-on and has a clearly visible nucleus of magnitude 10. About 50 million light-years from Earth, M77 is also a Seyfert galaxy and thus a bright object in the radio spectrum. Recently, the galactic cluster JKCS 041 was confirmed to be the most distant cluster of galaxies yet discovered. The massive cD galaxy Holmberg 15A is also
Cetus
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what we can see. These views "are remarkably close to the present-day views of the cosmos." In 1750, Thomas Wright speculated (correctly) that the Milky Way is a flattened disk of stars, and that some of the nebulae visible in the night sky might be separate Milky Ways. In 1755, Immanuel Kant used the term "island Universe" to describe these distant nebulae. Toward the end of the 18th century, Charles Messier compiled a catalog containing the 109 brightest celestial objects having nebulous appearance. Subsequently, William Herschel assembled a catalog of 5,000 nebulae. In 1845, Lord Rosse constructed a new telescope
Galaxy
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Leo T (dwarf galaxy) Leo T is a dwarf galaxy situated in the Leo constellation and discovered in 2006 in the data obtained by Sloan Digital Sky Survey. The galaxy is located at the distance of about 420 kpc from the Sun and moves away from the Sun with the velocity of about 35 km/s. The velocity with respect to the Milky Way is around −60 km/s implying a slow infall onto the Milky Way. Leo T is classified as a transitional object ('T' in the name) between dwarf spheroidal galaxies (dSph) and dwarf irregular galaxies (dIrr). Its half-light radius
Leo T (dwarf galaxy)
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4th magnitude (and those with measured luminosity), Andromeda has a relatively even distribution of evolved and main-sequence stars. The constellation of Andromeda lies well away from the galactic plane, so it does not contain any of the open clusters or bright nebulae of the Milky Way. Because of its distance in the sky from the band of obscuring dust, gas, and abundant stars of our home galaxy, Andromeda's borders contain many visible distant galaxies. The most famous deep-sky object in Andromeda is the spiral galaxy cataloged as Messier 31 (M31) or NGC 224 but known colloquially as the Andromeda Galaxy
Andromeda (constellation)
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skies. Being a diffuse object, it is challenging to see under light-polluted skies, even with a small telescope or binoculars, and low power is required to view it. It is a spiral galaxy with a diameter of 46,000 light-years and is thus smaller than both the Andromeda Galaxy and the Milky Way. A distance of less than 300 kiloparsecs between it and Andromeda supports the hypothesis that it is a satellite of the larger galaxy. Within the constellation, it lies near the border of Pisces, 3.5 degrees west-northwest of Alpha Trianguli and 7 degrees southwest of Beta Andromedae. Within the
Triangulum
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for stars at the outer edge of the Milky Way. Because the orbital velocity depends on the total mass inside the orbital radius, this suggests that the Milky Way is more massive, roughly equaling the mass of Andromeda Galaxy at 7 within of its center. In 2010, a measurement of the radial velocity of halo stars found that the mass enclosed within 80 kiloparsecs is 7 . According to a study published in 2014, the mass of the entire Milky Way is estimated to be 8.5 , but this is actually only half the mass of the Andromeda Galaxy. Much
Milky Way
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Milky Way and is obscured by galactic dust. The Circinus Galaxy is a Type II Seyfert galaxy and is one of the closest known active galaxies to the Milky Way, though it is probably slightly farther away than Centaurus A. Circinus Galaxy produced supernova SN 1996cr, which was identified over a decade after it exploded. This supernova event was first observed during 2001 as a bright, variable object in a Chandra X-ray Observatory image, but it was not confirmed as a supernova until years later. The Circinus Galaxy is one of twelve large galaxies in the "Council of Giants" surrounding
Circinus Galaxy
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Anticenter shell The anticenter shell or anticenter superbubble is a region near the anticenter of the Milky Way Galaxy that emits 21 cm radiation. It is located at , or l = 197°, b = +2° in galactic coordinates, near the border of the constellations Gemini and Orion. It is a supershell (a very large superbubble) within our galaxy that is spherical in shape and features jets of gas. Discovered in 1970, this galactic object has subsequently been variously classified by researchers as a spiral arm of the Milky Way in 1972, a nearby tidally-stripped dwarf galaxy in 1975, and
Anticenter shell
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diameter of (), which is slightly larger than the Milky Way Galaxy. The gap separating the two stellar populations may contain some star clusters that are almost too faint to see. As rare as this type of galaxy is, another more distant ring galaxy (SDSS J151713.93+213516.8) can be seen through Hoag's Object, between the nucleus and the outer ring of the galaxy, at roughly the one o'clock position in the image shown here. Even though Hoag's Object was clearly shown on the Palomar Star Survey, it was not included in either the "Morphological Catalogue of Galaxies", the "Catalogue of Galaxies
Hoag's Object
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Local Group The Local Group is the galaxy group that includes the Milky Way. The Local Group comprises more than 54 galaxies, most of them dwarf galaxies. Its gravitational center is located somewhere between the Milky Way and the Andromeda Galaxy. The Local Group has a diameter of (about 10 meters) and has a binary (dumbbell) distribution. The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The three largest members of the group (in descending order) are the Andromeda Galaxy, the Milky Way and the Triangulum Galaxy. The larger
Local Group
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this discussion regarding the new McKay-Carter Intergalactic Gate Bridge, General Hank Landry states that the distance between the Pegasus and Milky Way galaxies is "three million light-years," suggesting that the series takes place in the Pegasus Dwarf Irregular Galaxy. Also, in a few episodes the Pegasus galaxy has been seen from between the Milky Way and Pegasus, showing an irregular galaxy. Unlike what happened in the Milky Way, the human population of the Pegasus galaxy is a product of Ancient seeding. The Lanteans arrived in the Pegasus galaxy via the Ancient city ship of Atlantis. As there was seldom interbreeding
Mythology of Stargate
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energy than visible light photons. Objects with temperatures between about 5 K and 340 K will emit radiation in the far infrared range (see Wien's displacement law and Black-body radiation). This property is sometimes used to observe interstellar gases where new stars are often formed. For example, the center of the Milky Way Galaxy is very bright in far infrared images because the dense concentration of stars there heats the surrounding dust and causes it to emit radiation in this part of the spectrum. Disregarding the center of our own galaxy, the brightest far infrared object in the sky is
Far infrared
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can pull material out of galaxies and create small satellite galaxies in either prograde or retrograde orbits around larger galaxies. A galaxy called Complex H, which was orbiting the Milky Way in a retrograde direction relative to the Milky Way's rotation, is colliding with the Milky Way. NGC 7331 is an example of a galaxy that has a bulge that is rotating in the opposite direction to the rest of the disk, probably as a result of infalling material. The center of a spiral galaxy contains at least one supermassive black hole. A retrograde black hole – one whose spin
Retrograde and prograde motion
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Milky Way and NGC 4395, are known to contain both a SBH and a NSC. The mass associated with CMOs is roughly 0.1–0.3% times the total mass of the galactic bulge. Central massive object Central massive object (CMO) refers to a mass concentration at the center of a galaxy. It can be either a supermassive black hole or a nuclear star cluster. The most massive galaxies are thought to always contain a supermassive black hole (SBH); these galaxies do not contain nuclear star clusters, and the CMO is identified with the SBH. Fainter galaxies usually contain a nuclear star cluster
Central massive object
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Dust lane A dust lane is a relatively dense obscuring band of interstellar dust, observed as a dark swath against the background of a brighter object, especially a galaxy. These dust lanes can usually be seen in spiral galaxies (e.g., the Milky Way) when viewed from the edge. Due to the dense and relatively thick nature of this dust, light from the galaxy is reduced by several magnitudes. In the Milky Way, this reduction of light makes it impossible to see the light from the central bulge of the galaxy from Earth. This dust, as well as the gasses also
Dust lane
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Cosmic noise Cosmic noise and galactic radio noise is random noise that originates outside the Earth's atmosphere. It can be detected and heard in radio receivers. Cosmic noise characteristics are similar to those of thermal noise. Cosmic noise is experienced at frequencies above about 15 MHz when highly directional antennas are pointed toward the sun or to certain other regions of the sky such as the center of the Milky Way Galaxy. Celestial objects like Quasars, super dense objects that lie far from Earth, emit electromagnetic waves in its full spectrum including radio waves. We can also hear the fall
Cosmic noise
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of the cluster at a projected separation of 3.7°, or around one megaparsec, from the cluster center at Messier 87. The galaxy is undergoing ram-pressure stripping as it moves through the intracluster medium. Messier 99 Messier 99 or M99, also known as NGC 4254, is a grand design spiral galaxy in the northern constellation Coma Berenices approximately in distance from the Milky Way. It was discovered by Pierre Méchain on March 17, 1781. The discovery was then reported to Charles Messier, who included the object in the Messier Catalogue of comet-like objects. Messier 99 was one of the first galaxies
Messier 99
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Galaxy A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek "" (), literally "milky", a reference to the Milky Way. Galaxies range in size from dwarfs with just a few hundred million () stars to giants with one hundred trillion () stars, each orbiting its galaxy's center of mass. Galaxies are categorized according to their visual morphology as elliptical, spiral, or irregular. Many galaxies are thought to have supermassive black holes at their centers. The Milky Way's central black hole, known as Sagittarius A*,
Galaxy
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−6.75, meaning that it is less luminous than some stars, like Deneb in the Milky Way. It is comparable in luminosity to Rigel. It has been described as similar to the Sextans Dwarf Galaxy. Both galaxies are ancient and metal-deficient. It estimated to be located at a distance of about 330,000 light-years (100 kpc) from the Earth. That is about twice the distance to the Large Magellanic Cloud; the largest and most luminous satellite galaxy of the Milky Way. There was another object called "Ursa Major Dwarf", discovered by Edwin Hubble in 1949. It was designated as Palomar 4. Due
Ursa Major I Dwarf
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NGC 4550 NGC 4550 is a barred lenticular galaxy located in the constellation of Virgo that can be seen with amateur telescopes. It lies at a distance of 50 million light-years (15.5 mega parsecs) from the Milky Way and is a member of the Virgo Cluster. While NGC 4550 is not one of the brightest galaxies of the Virgo Cluster, its notable as it's one of the few galaxies where a large amount of its stars rotate around the galaxy's center in opposite direction to the others About her research article on this galaxy, Vera Rubin wrote: "I discovered from
NGC 4550
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Messier 86 Messier 86 (also known as M86 or NGC 4406) is an elliptical or lenticular galaxy in the constellation Virgo. It was discovered by Charles Messier in 1781. M86 lies in the heart of the Virgo Cluster of galaxies and forms a most conspicuous group with another large galaxy known as Messier 84. It displays the highest blue shift of all Messier objects, as it is approaching the Milky Way at 244 km/s. This is due to its falling towards the center of the Virgo cluster from the opposite side, which causes it to move in the direction of
Messier 86
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NGC 17 NGC 17, also known as NGC 34, is a spiral galaxy in the constellation Cetus. It is the result of a merger between two disk galaxies, resulting in a recent starburst in the central regions and continuing starforming activity. The galaxy is still gas-rich, and has a single galactic nucleus. It lies 250 million light years away. It was discovered in 1886 by Frank Muller and then observed again later that year by Lewis Swift. Due to the major merger event NGC 17 has no defined spiral arms like the Milky Way galaxy. Unlike the Milky Way, the
NGC 17
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other associations since Carina OB1 has relatively little dust extinction in its region. Together with Carina OB2, they compromise the most massive stellar grouping known in the galaxy. Carina OB1 is about across, and is the most massive stellar association in the Milky Way Galaxy since it lies within an active emission nebula. It contains many hot luminous stars which share common characteristics. Carina OB1 Carina OB1 is a giant OB association in the Carina Nebula, which is home to some of the most massive and luminous stars in the Milky Way Galaxy. It includes the young star clusters Collinder
Carina OB1
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not visible to the naked eye but can be made out using binoculars under favourable conditions. The nebula lies in the Perseus Arm of the Milky Way galaxy, at a distance of about from Earth. It has a diameter of , corresponding to an apparent diameter of some 7 arcminutes, and is expanding at a rate of about , or 0.5% of the speed of light. At the center of the nebula lies the Crab Pulsar, a neutron star across with a spin rate of 30.2 times per second, which emits pulses of radiation from gamma rays to radio waves.
Crab Nebula
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Barycentric celestial reference system The barycentric celestial reference system (BCRS) is a coordinate system used in astrometry to specify the location and motions of astronomical objects. It was created in 2000 by the International Astronomical Union (IAU) to be the global standard reference system for objects located outside the gravitational vicinity of Earth: planets, moons, and other Solar System bodies, stars and other objects in the Milky Way galaxy, and extra-galactic objects. The geocentric celestial reference system (GCRS), also created by the IAU in 2000, is a similar standard coordinate system used to specify the location and motions of near-earth
Barycentric celestial reference system
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it toward the center of our galaxy at about 67 km/sec (Li et al., 2016: 5, Table 1). While these observations solve the problem of radial velocity, the movement of Eridanus II towards the center of our galaxy, they cannot solve the problem of transverse velocity, motion at right angles to the line between Eridanus II and the Milky Way. That is, we cannot determine whether Eridanus II is orbiting the Milky Way, or simply moving in its direction from outside the system. Li et al. (2016: 7–8) report that Eridanus II does not exhibit a "tail" or gradient of
Eridanus II
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HI (atomic hydrogen) disk of the Milky Way Galaxy to the tidal effects of a perturbing galaxy. The unseen perturber's mass was calculated to be about 1% of that of the Milky Way, which would make it the third heaviest satellite of the Milky Way, after the Magellanic Clouds (Large Magellanic Cloud and Small Magellanic Cloud, each some 10x larger than Galaxy X). In this hypothetical model, the putative satellite galaxy would have interacted with the Milky Way some 600 million years ago, coming as close as , and would now be moving away from the Milky Way. The name
Galaxy X (galaxy)
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found within these lanes, mix together and combine to form stars and planets. Dust lane A dust lane is a relatively dense obscuring band of interstellar dust, observed as a dark swath against the background of a brighter object, especially a galaxy. These dust lanes can usually be seen in spiral galaxies (e.g., the Milky Way) when viewed from the edge. Due to the dense and relatively thick nature of this dust, light from the galaxy is reduced by several magnitudes. In the Milky Way, this reduction of light makes it impossible to see the light from the central bulge
Dust lane
5593773
Tucana Dwarf The Tucana Dwarf Galaxy is a dwarf galaxy in the constellation Tucana. It was discovered in 1990 by R.J. Lavery of Mount Stromlo Observatory. It is composed of very old stars and is very isolated from other galaxies. Its location on the opposite side of the Milky Way from other Local Group galaxies makes it an important object for study. The Tucana Dwarf is a dwarf spheroidal galaxy of type dE5. It contains only old stars, formed in a single star formation era around the time the Milky Way's globular clusters formed. It is not experiencing any current
Tucana Dwarf
1694457
is thought to contain 100,000 stars. Lying three degrees to the south is NGC 6744, a spiral galaxy around 30 million light years away from Earth that resembles the Milky Way, but is twice its diameter. A type 1c supernova was discovered in the galaxy in 2005; known as SN2005at, it peaked at magnitude 16.8. The dwarf galaxy IC 4662 lies 10 arcminutes northeast of Eta Pavonis, and is of magnitude 11.62. Located only 8 million light years away, it has several regions of high star formation. The 14th-magnitude galaxy IC 4965 lies 1.7 degrees west of Alpha Pavonis, and
Pavo (constellation)
10017628
Center, both of which lack hard boundaries. NGC 5964 NGC 5964 is a barred spiral galaxy in the constellation Serpens Caput. NGC 5964 is also known by the names IC 4551 and PGC 55637. NGC 5964 has relatively unwound spiral arms; it lacks the clear defined spiral arms the Milky Way galaxy has. The central bar is very small, long and thin. NGC 5964 thus does not have a galactic habitable zone like the Milky Way. For the Milky Way, the galactic habitable zone is commonly believed to be an annulus with an outer radius of about 10 kiloparsecs and
NGC 5964
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US 708 US 708 is a hyper-velocity O class subdwarf in Ursa Major in the halo of the Milky Way Galaxy. One of the fastest-moving stars in the galaxy, the star was first surveyed in 1982. US 708 was first discovered in 1982 by Peter Usher and colleagues of Pennsylvania State University as a faint blue object in the Milky Way halo. Sloan Digital Sky Survey measured the star again in 2005. In 2015, Stephan Geier of the European Southern Observatory led a team that reported in "Science" that the velocity of the star was 1,200 kilometers per second, the
US 708
9122011
current luminosity). When two spiral galaxies collide, the hydrogen present on their disks is compressed, producing strong star formation as can be seen on interacting systems like the Antennae Galaxies. In the case of the Andromeda–Milky Way collision, it is believed that there will be little gas remaining in the disks of both galaxies, so the mentioned starburst will be relatively weak, though it still may be enough to form a quasar. The galaxy product of the collision has been nicknamed "Milkomeda" or "Milkdromeda". According to simulations, this object will look like a giant elliptical galaxy, but with a centre
Andromeda–Milky Way collision
5631344
being tidally disrupted by the Milky Way galaxy. Carina Dwarf Spheroidal Galaxy The Carina Dwarf Spheroidal Galaxy is a dwarf galaxy in the Carina constellation. It was discovered in 1977 with the UK Schmidt Telescope by Cannon et al. The Carina Dwarf Spheroidal galaxy is a satellite galaxy of the Milky Way and is receding from it at 230 km/s. The diameter of the galaxy is about 1600 light-years, which is 75 times smaller than the Milky Way. Most of the stars in the galaxy formed 7 billion years ago, although it also experienced bursts of star formation about 13
Carina Dwarf Spheroidal Galaxy
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the Sun far from the center. Both analyses failed to take into account the absorption of light by interstellar dust present in the galactic plane, but after Robert Julius Trumpler quantified this effect in 1930 by studying open clusters, the present picture of our host galaxy, the Milky Way, emerged. A few galaxies outside the Milky Way are visible on a dark night to the unaided eye, including the Andromeda Galaxy, Large Magellanic Cloud and the Small Magellanic Cloud. In the 10th century, the Persian astronomer Al-Sufi made the earliest recorded identification of the Andromeda Galaxy, describing it as a
Galaxy
9122002
Andromeda–Milky Way collision The Andromeda–Milky Way collision is a galactic collision predicted to occur in about 5 billion years between two galaxies in the Local Group—the Milky Way (which contains the Solar System and Earth) and the Andromeda Galaxy. The stars involved are sufficiently far apart that it is improbable that any of them will individually collide. Some stars will be ejected from the resulting galaxy, nicknamed "Milkomeda" or "Milkdromeda". The Andromeda Galaxy is approaching the Milky Way at about as indicated by blueshift. However, the lateral velocity is very difficult to measure with a precision to draw reasonable conclusions:
Andromeda–Milky Way collision
9870656
lute). The story is based on a 4,000-year-old Chinese folktale about the creation of Night and Day, a story of star-crossed lovers. "The Silver River" is the Chinese name for what is known in the West as the "Milky Way", the galaxy of the solar system. In Chinese tradition, the Silver River bathed heaven and earth in constant light and connected both realms, allowing earthly and celestial creatures to meet. The Jade Emperor, Lord of Heaven, dreams of a chaos that plunges heaven and earth into darkness. His nightmare comes true when the mortal Cowherd (also known as Buffalo Boy
The Silver River
2464712
some proper motion work. But no astrophysics or anything that looked like that. No structure of the galaxy, no dynamics of the galaxy. There was no one else in Leiden who was interested in these problems in which I was principally interested, so the first years I worked more or less by myself in these projects. De Sitter was interested, but his main line of research was celestial mechanics; at that time the expanding universe had moved away from his direct interest." As the European Space Agency states, Oort "sh[ook] the scientific world by demonstrating that the Milky Way rotates
Jan Oort
7301184
is a member of the M94 Group as well. DDO 199 (also known as Ursa Minor Dwarf, PGC 54074 or UGC 9749) is a dwarf spheroidal galaxy which is located in the northern constellation of Ursa Minor. It was discovered in 1955 by an American astronomer Albert George Wilson. It is a satellite of the Milky Way as well. DDO 210 (also known as Aquarius Dwarf or PGC 65367) is a dwarf irregular galaxy in the constellation of Aquarius. It is a member of the Local Group and lies 3.2 ± 0.2 million light years from our Milky Way. DDO
David Dunlap Observatory Catalogue
2519622
with that of the Milky Way. However, Sgr dSph still has coherence as a dispersed elongated ellipse, and appears to move in a roughly polar orbit around the Milky Way as close as 50,000 light-years from the galactic core. Although it may have begun as a spherical object before falling towards the Milky Way, Sgr dSph is now being torn apart by immense tidal forces over hundreds of millions of years. Numerical simulations suggest that stars ripped out from the dwarf would be spread out in a long stellar stream along its path, which were subsequently detected. However, some astronomers
Sagittarius Dwarf Spheroidal Galaxy
16830085
Swift J1745-26 Swift J1745-26 is a stellar-mass black hole located a few degrees from the center of the Milky Way galaxy toward the constellation Sagittarius. It was discovered by NASA's Swift satellite on September 16, 2012 due to the detection of an X-ray nova. The pattern of X-rays from the nova indicated that the central object was a black hole. Its name arises from the coordinates of its sky position. While astronomers do not know its precise distance, they think the object resides about 20,000 to 30,000 light-years away in the galaxy's inner region. Ground-based observatories have detected infrared and
Swift J1745-26
417534
from Earth. Like neighboring 47 Tucanae, NGC 362 is a Shapley class III cluster and among the brightest globular clusters in the sky. Unusually for a globular cluster, its orbit takes it very close to the center of the Milky Way—approximately 3,000 light-years. It was discovered in the 1820s by James Dunlop. Its stars become visible at 180x magnification through a telescope. Located at the southern end of Tucana, the Small Magellanic Cloud is a dwarf galaxy that is one of the nearest neighbors to the Milky Way galaxy at a distance of 210,000 light-years. Though it probably formed as
Tucana
3511714
estimated to be −21.9 at (−21.8 at the average distance of above), that as stated above makes it the brightest galaxy within a radius of around the Milky Way. A report from 2016 used the Hubble Space Telescope to measure the distance to M104 based on the tip of the red-giant branch method yielding 9.55 ± 0.13 ± 0.31 Mpc. The Sombrero Galaxy lies within a complex, filament-like cloud of galaxies that extends to the south of the Virgo Cluster. However, it is unclear whether the Sombrero Galaxy is part of a formal galaxy group. Hierarchical methods for identifying groups,
Sombrero Galaxy
371426
Sagittarius, near its western boundary with Ophiuchus. Astronomers believe that one of its components, known as Sagittarius A*, is associated with a supermassive black hole at the center of the galaxy, with a mass of 2.6 million solar masses. The Sagittarius Dwarf Elliptical Galaxy is located just outside the Milky Way. Baade's Window is an area with very little obscuring dust that shows objects closer to the Milky Way's center that would normally be visible. NGC 6522, magnitude 8.6, and NGC 6528, magnitude 9.5, are both globular clusters visible through Baade's Window. 20,000 and 24,000 light-years from Earth, with Shapley
Sagittarius (constellation)
50902
stars by where formula_36 is the mass of the background stars. The gravitational force from the massive object causes nearby stars to move faster than they otherwise would, increasing both formula_34 and "V". The Brownian velocity of Sgr A*, the supermassive black hole at the center of the Milky Way galaxy, is predicted from this formula to be less than 1 km "s". In mathematics, Brownian motion is described by the Wiener process; a continuous-time stochastic process named in honor of Norbert Wiener. It is one of the best known Lévy processes (càdlàg stochastic processes with stationary independent increments) and
Brownian motion
5604632
galaxy appears to be slightly off-center, with one side of the disk appearing to extend further away from the core than the opposite side. The galaxy is similar in size and structure to the Milky Way, and is often referred to as "the Milky Way's twin". However, discoveries in the 2000s regarding the structure of the Milky Way may call this similarity into doubt, particularly because the latter is now believed to be a barred spiral, compared to the unbarred status of NGC 7331. In spiral galaxies the central bulge typically co-rotates with the disk but the bulge in the
NGC 7331
19010284
object from that galaxy. Pyxis globular cluster The Pyxis globular cluster is a globular cluster in the constellation Pyxis. It lies around 130,000 light-years distant from earth and around 133,000 light-years distant from the centre of the Milky Way—a distance not previously thought to contain globular clusters. It is around 13.3 ± 1.3 billion years old. Discovered in 1995 by astronomer Ronald Weinberger while he was looking for planetary nebulae, it is in the Galactic halo. Irwin and colleagues noted that it appears to lie on the same plane as the Large Magellanic Cloud and raised the possibility that it
Pyxis globular cluster
3741314
Circinus Galaxy The Circinus Galaxy (ESO 97-G13) is a Seyfert galaxy in the constellation of Circinus. It is located 4 degrees below the Galactic plane, and, at a distance of , and is one of the closest galaxies to the Milky Way. The galaxy is undergoing tumultuous changes, as rings of gas are likely being ejected from the galaxy. Its outermost ring is 1400 light-years across while the inner ring is 260 light-years across. Although the Circinus galaxy can be seen using a small telescope, it was not noticed until 1977 because it lies close to the plane of the
Circinus Galaxy
3511703
Sombrero Galaxy The Sombrero Galaxy (also known as Messier Object 104, M104 or NGC 4594) is a spiral galaxy in the constellation Virgo located from Earth. The galaxy has a diameter of approximately 15kpc (50,000 light-years), 30% the size of the Milky Way. It has a bright nucleus, an unusually large central bulge, and a prominent dust lane in its inclined disk. The dark dust lane and the bulge give this galaxy the appearance of a sombrero. Astronomers initially thought that the halo was small and light, indicative of a spiral galaxy, but the Spitzer Space Telescope found that the
Sombrero Galaxy
1354460
most obvious deep-sky object is the naked-eye Andromeda Galaxy (M31, also called the Great Galaxy of Andromeda), the closest spiral galaxy to the Milky Way and one of the brightest Messier objects. Several fainter galaxies, including M31's companions M110 and M32, as well as the more distant NGC 891, lie within Andromeda. The Blue Snowball Nebula, a planetary nebula, is visible in a telescope as a blue circular object. In Chinese astronomy, the stars that make up Andromeda were members of four different constellations that had astrological and mythological significance; a constellation related to Andromeda also exists in Hindu mythology.
Andromeda (constellation)
807469
1.5 trillion solar masses) compared to for the Milky Way. This contradicts earlier measurements, that seem to indicate that Andromeda Galaxy and the Milky Way are almost equal in mass. Even so, Andromeda Galaxy's spheroid actually has a higher stellar density than that of the Milky Way and its galactic stellar disk is about twice the size of that of the Milky Way. The total stellar mass of Andromeda Galaxy is estimated to be between ., (i.e., around twice as massive as that of the Milky Way) and , with around 30% of that mass in the central bulge, 56%
Andromeda Galaxy
12703726
that of the Sun. HVSs with smaller masses are also expected and G/K-dwarf HVS candidates have been found. HVSs that have come into the Milky Way came from the dwarf galaxy Large Magellanic Cloud. When the dwarf galaxy made its closest approach to the center of the Milky Way, it underwent intense gravitational tugs. These tugs boosted the energy of some of its stars so much that they broke free of the dwarf galaxy entirely and were thrown into space, due to the slingshot-like effect of the boost. Some neutron stars are inferred to be traveling with similar speeds. This
Stellar kinematics
174096
Small Magellanic Cloud, a satellite galaxy to the Milky Way. Most of the cloud is located in the neighbouring constellation Tucana. Hydrus Hydrus is a small constellation in the deep southern sky. It was one of twelve constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman and it first appeared on a 35-cm (14 in) diameter celestial globe published in late 1597 (or early 1598) in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603. The French explorer and
Hydrus
807455
Milky Way Galaxy (~0.8-1.5 solar masses vs the Milky Way's 8.5 solar masses), though a 2018 study found that the Andromeda Galaxy's mass is roughly the same as the Milky Way's. The Andromeda Galaxy, spanning approximately 220,000 light-years, is the largest galaxy in our Local Group, which is also home to the Triangulum Galaxy and other minor galaxies. The Milky Way and Andromeda galaxies are expected to collide in ~4.5 billion years, merging to form a giant elliptical galaxy or a large disc galaxy. With an apparent magnitude of 3.4, the Andromeda Galaxy is among the brightest of the Messier
Andromeda Galaxy
3511704
halo around the Sombrero Galaxy is larger and more massive than previously thought, indicative of a giant elliptical galaxy. The galaxy has an apparent magnitude of +8.0, making it easily visible with amateur telescopes, and it is considered by some authors to be the brightest galaxy within a radius of 10 megaparsecs of the Milky Way. Its large bulge, its central supermassive black hole, and its dust lane all attract the attention of professional astronomers. The Sombrero Galaxy was discovered on May 11, 1781 by Pierre Méchain, who described the object in a May 1783 letter to J. Bernoulli that
Sombrero Galaxy
19673987
meaning the stars have a low abundance of elements other than hydrogen and helium—what astronomers term metallicity. As recently as 1995, it was considered the most metal-poor globular cluster in the Milky Way. The chemical abundances of the stars in NGC 5053 are more similar to those in the dwarf galaxy Sagittarius Dwarf Spheroidal Galaxy than to the Milky Way halo. Along with the kinematics of the globular cluster, this suggests that NGC 5053 may have been stripped from the dwarf galaxy. There are ten known RR Lyrae variable stars in this cluster with masses ranging from 68% to 78%
NGC 5053
2291070
detector would observe signals from binary stars within our galaxy (the Milky Way); signals from binary supermassive black holes in other galaxies; and extreme-mass-ratio inspirals and bursts produced by a stellar-mass compact object orbiting a supermassive black hole. There are also more speculative signals such as signals from cosmic strings and primordial gravitational waves generated during cosmological inflation. LISA will be able to detect the nearly monochromatic gravitational waves emanating of close binaries consisting of two compact stellar objects (white dwarfs, neutron stars, and black holes) in the Milky Way. At low frequencies these are actually expected to be so
Laser Interferometer Space Antenna
9122005
the Triangulum Galaxy—the third-largest and third-brightest galaxy of the Local Group—will participate in the collision event, too. Its most likely fate is to end up orbiting the merger remnant of the Milky Way and Andromeda galaxies and finally to merge with it in an even more distant future. However, a collision with the Milky Way, before it collides with the Andromeda Galaxy, or an ejection from the Local Group cannot be ruled out. While the Andromeda Galaxy contains about 1 trillion () stars and the Milky Way contains about 300 billion (3), the chance of even two stars colliding is
Andromeda–Milky Way collision
1482928
be split in two, with a smaller section of this galaxy behind the main part of the SMC (as seen from Earth's perspective), and separated by about 30,000 light years. They suggest the reason for this is due to a past interaction with the LMC splitting the SMC, and that the two sections are still moving apart. They have dubbed this smaller remnant the Mini Magellanic Cloud. Magellanic Clouds The Magellanic Clouds (or "Nubeculae Magellani") are two irregular dwarf galaxies visible in the Southern Celestial Hemisphere; they are members of the Local Group and are orbiting the Milky Way galaxy.
Magellanic Clouds
3771114
Omega Centauri, the remnant of a dwarf spheroidal galaxy disrupted and accreted by the Milky Way. However, later research seems to disprove that possibility. Astronomer Leos Ondra has noted that NGC 2419 would be the "best and brightest" for any observers in the Andromeda Galaxy, looking for globular clusters in our galaxy since it lies outside the obscuring density of the main disk. This is analogous to the way the cluster G1 can be seen orbiting outside of the Andromeda Galaxy from Earth. NGC 2419 NGC 2419 (also known as Caldwell 25) is a globular cluster in the constellation Lynx.
NGC 2419
516525
Large Magellanic Cloud The Large Magellanic Cloud (LMC) is a satellite galaxy of the Milky Way. At a distance of about 50 kiloparsecs (≈163,000 light-years), the LMC is the second- or third-closest galaxy to the Milky Way, after the Sagittarius Dwarf Spheroidal (~16 kpc) and the possible dwarf irregular galaxy known as the Canis Major Overdensity. Based on readily visible stars and a mass of approximately 10 billion solar masses, the diameter of the LMC is about , making it roughly one one-hundredth as massive as the Milky Way. This makes the LMC the fourth-largest galaxy in the Local Group,
Large Magellanic Cloud
6923832
NGC 4945 NGC 4945 is a barred spiral galaxy in the constellation Centaurus, visible near the star Xi Centauri. The galaxy was discovered by James Dunlop in 1826 and is thought to be similar to the Milky Way Galaxy, although X-ray observations show that NGC 4945 has an unusual energetic Seyfert 2 nucleus that might house a supermassive black hole. This object has an estimated mass of . NGC 4945 one of the brightest galaxies of the Centaurus A/M83 Group, a large, nearby group of galaxies. The galaxy is the second brightest galaxy in the subgroup centered on Centaurus A.
NGC 4945
151346
merging into a single elliptical galaxy. In the Local Group, the Milky Way and the Andromeda Galaxy are gravitationally bound, and currently approaching each other at high speed. Simulations show that the Milky Way and Andromeda are on a collision course, and are expected to collide in less than five billion years. During this collision, it is expected that the Sun and the rest of the Solar System will be ejected from its current path around the Milky Way. The remnant could be a giant elliptical galaxy. One observation (see above) that must be explained by a successful theory of
Galaxy formation and evolution
17751232
NGC 7727's most likely fate is to become an elliptical galaxy in the future, with very little interstellar dust and star formation NGC 7727 NGC 7727 is a peculiar galaxy in the constellation Aquarius. This object is located at a distance of 23.3 megaparsecs (76 million light years) of the Milky Way and has a peculiar aspect, with several plumes and streams of irregular shape that explains its inclusion on Halton C. Arp's Atlas of Peculiar Galaxies with the number 222, being classified as a "Galaxy with amorphous spiral arms". In all likelihood, this system is the product of the
NGC 7727
435999
Milky Way itself. NGC 6217 is a barred spiral galaxy located some 67 million light-years away, which can be located with a or larger telescope as an 11th magnitude object about 2.5° east-northeast of Zeta Ursae Minoris. It has been characterized as a starburst galaxy, which means it is undergoing a high rate of star formation compared to a typical galaxy. NGC 6251 is an active supergiant elliptical radio galaxy more than 340 million light-years away from Earth. It has a Seyfert 2 active galactic nucleus, and is one of the most extreme examples of a Seyfert galaxy. This galaxy
Ursa Minor
3030285
Dwingeloo 1 Dwingeloo 1 is a barred spiral galaxy about 10 million light-years away from the Earth, in the constellation Cassiopeia. It lies in the Zone of Avoidance and is heavily obscured by the Milky Way. The size and mass of Dwingeloo 1 are comparable to those of Triangulum Galaxy. Dwingeloo 1 has two smaller satellite galaxies — Dwingeloo 2 and MB 3 — and is a member of the IC 342/Maffei Group of galaxies. The Dwingeloo 1 galaxy was discovered in 1994 by the Dwingeloo Obscured Galaxy Survey (DOGS), which searched for neutral hydrogen (HI) radio emissions at the
Dwingeloo 1
16715277
DDO 190 DDO 190 (or UGC 9240) is a dwarf irregular galaxy in the vicinity of the Milky Way, as it is relatively small and lacks clear structure. It is away from Earth and lies out of the Local Group, determined by the tip of the red giant branch method. The outskirts of the galaxy are harbouring older (reddish) stars, while the centre is crowded with younger (bluish) stars. Heated gas is observed at several places. DDO 190 still experiences some active star formation. The galaxy is categorised as a Magellanic dwarf galaxy of morphological type Im. Its metallicity is
DDO 190
20010584
were determined to be satellites of the Milky Way (Li et al. (2016: 8)). For reasons to be discussed in the concluding section, most researchers now believe that Eridanus II is an extremely long-period (i.e., several billion years per orbit) satellite of the Milky Way, probably beginning only its second approach to our galaxy. To put these numbers into their proper context, it may be worth reminding ourselves that the expansion of the universe is a significant factor on these distance scales. Eridanus II is moving toward the center of the Milky Way at 67 km/sec. However, applying the current
Eridanus II
2519616
Sagittarius Dwarf Spheroidal Galaxy The Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), also known as the Sagittarius Dwarf Elliptical Galaxy (Sgr dE or Sag DEG), is an elliptical loop-shaped satellite galaxy of the Milky Way. It consists of four globular clusters, the main cluster having been discovered in 1994. Sgr dSph is roughly 10,000 light-years in diameter, and is currently about 70,000 light-years from Earth, travelling in a polar orbit (i.e. an orbit passing over the Milky Way’s galactic poles) at a distance of about 50,000 light-years from the core of the Milky Way (about 1/3 the distance of the Large
Sagittarius Dwarf Spheroidal Galaxy