The Milky Way is the second-largest galaxy in the Local Group (after the Andromeda Galaxy), with its stellar disk approximately in diameter and, on average, approximately thick. The Milky Way is approximately 890 billion times the mass of the Sun. To compare the relative physical scale of the Milky Way, if the Solar System out to Neptune were the size of a US quarter (), the Milky Way would be approximately the size of the contiguous United States. There is a ring-like filament of stars rippling above and below the relatively flat galactic plane, wrapping around the Milky Way at a diameter of , which may be part of the Milky Way itself.
Size and mass
Milky Way
Milky Way | Size and mass
The Milky Way is the second-largest galaxy in the Local Group with its stellar disk approximately in diameter and, on average, approximately thick. The Milky Way is approximately 890 billion times the mass of the Sun. It is the second-largest galaxy in the Local Group. It is the second-largest galaxy in the Local Group. The Milky Way is approximately 890 billion times the mass of the Sun.
where is the solar system located in our galaxy
user
The Solar System, is located in the Milky Way's galactic habitable zone.
assistant
what is the milky way?
user
It is the galaxy that contains our Solar System.
assistant
can you tell me the names of the stars that form a part of this galaxy?
user
The Milky Way may contain ten billion white dwarfs, a billion neutron stars, and a hundred million stellar black holes.
assistant
can this galaxy be seen from earth in the northern hemisphere?
user
The Milky Way is visible from Earth as a hazy band of white light, some 30° wide, arching across the night sky.  As viewed from Earth, the visible region of the Milky Way's galactic plane occupies an area of the sky that includes 30 constellations.
assistant
how would you describe its size?
user
The Milky Way is the second-largest galaxy in the Local Group (after the Andromeda Galaxy), with its stellar disk approximately in diameter and, on average, approximately thick. The Milky Way is approximately 890 billion times the mass of the Sun. To compare the relative physical scale of the Milky Way, if the Solar System out to Neptune were the size of a US quarter (), the Milky Way would be approximately the size of the contiguous United States. There is a ring-like filament of stars rippling above and below the relatively flat galactic plane, wrapping around the Milky Way at a diameter of , which may be part of the Milky Way itself.
Milky Way | Size and mass
For comparison, the Milky Way has a diameter of at least 30,000 parsecs (100,000 ly) and is separated from the Andromeda Galaxy, its nearest large neighbor, by 780,000 parsecs (2.5 million ly.)
Galaxy | Introduction
In March 2019, observations from Hubble and data from the European Space Agency's Gaia space observatory were combined to determine that the Milky Way Galaxy weighs approximately 1.5 trillion solar units and has a radius of 129,000 light years.
Hubble Space Telescope | Mass and size of Milky Way
According to a study published in 2014, the mass of the entire Milky Way is estimated to be 8.5 , but this is only half the mass of the Andromeda Galaxy. A recent mass estimate for the Milky Way is 1.29 . Much of the mass of the Milky Way seems to be dark matter, an unknown and invisible form of matter that interacts gravitationally with ordinary matter. A dark matter halo is conjectured to spread out relatively uniformly to a distance beyond one hundred kiloparsecs (kpc) from the Galactic Center. Mathematical models of the Milky Way suggest that the mass of dark matter is 1–1.5 .
Milky Way | Size and mass
Estimates of the mass of the Milky Way vary, depending upon the method and data used. The low end of the estimate range is 5.8 solar masses (), somewhat less than that of the Andromeda Galaxy. Measurements using the Very Long Baseline Array in 2009 found velocities as large as 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 .
Milky Way | Size and mass
The Milky Way is visible from Earth as a hazy band of white light, some 30° wide, arching across the night sky. In night sky observing, although all the individual naked-eye stars in the entire sky are part of the Milky Way Galaxy, the term "Milky Way" is limited to this band of light. The light originates from the accumulation of unresolved stars and other material located in the direction of the galactic plane. Brighter regions around the band appear as soft visual patches known as star clouds. The most conspicuous of these is the Large Sagittarius Star Cloud, a portion of the central bulge of the galaxy.
Milky Way | Appearance
Recent studies indicate a range in mass, as large as 4.5 and as small as 8 . The total mass of all the stars in the Milky Way is estimated to be between 4.6 and 6.43 . In addition to the stars, there is also interstellar gas, comprising 90% hydrogen and 10% helium by mass, with two thirds of the hydrogen found in the atomic form and the remaining one-third as molecular hydrogen. The mass of the Milky Way's interstellar gas is equal to between 10% and 15% of the total mass of its stars. Interstellar dust accounts for an additional 1% of the total mass of the gas.
Milky Way | Size and mass
The galaxy's large apparent size can be attributed to the fact that it is face-on. Despite its size, it only has an apparent visual magnitude of 11.7. It can be classified as spiral galaxy of type SBbc using the Hubble Sequence. The object's distance of roughly 220 million light-years from the Solar System can be estimated using its redshift and Hubble's law.
NGC 521 | Description
The actual size of dark galaxies is unknown because they cannot be observed with normal telescopes. There have been various estimations, ranging from double the size of the Milky Way to the size of a small quasar.
Dark galaxy | Size
Other astronomers such as Simon Marius, Giovanni Battista Riccioli, and Martinus Hortensius made similar measurements of stars, and Marius and Riccioli concluded the smaller sizes were not small enough to answer Tycho's argument.
Galileo Galilei | Milky Way and stars
A different method by Harlow Shapley based on the cataloguing of globular clusters led to a radically different picture: a flat disk with diameter approximately 70 kiloparsecs and 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.
Galaxy | Milky Way
The resulting disk of stars can be seen as a band on the sky from our perspective inside the disk. In a treatise in 1755, Immanuel Kant elaborated on Wright's idea about the structure of the Milky Way. The first project to describe the shape of the Milky Way and the position of the Sun was undertaken by William Herschel in 1785 by counting the number of stars in different regions of the sky. He produced a diagram of the shape of the galaxy with the Solar System close to the center. Using a refined approach, Kapteyn in 1920 arrived at the picture of a small (diameter about 15 kiloparsecs) ellipsoid galaxy with the Sun close to the center.
Galaxy | Milky Way
The Sun is from the Galactic Center. This value is estimated using geometric-based methods or by measuring selected astronomical objects that serve as standard candles, with different techniques yielding various values within this approximate range. In the inner few kpc (around 10,000 light-years radius) is a dense concentration of mostly old stars in a roughly spheroidal shape called the bulge. It has been proposed that the Milky Way lacks a bulge formed due to a collision and merger between previous galaxies, and that instead it only has a "pseudobulge" formed by its central bar. However, confusion in the literature between the (peanut shell)-shaped structure created by instabilities in the bar, versus a possible bulge with an expected half-light radius of 0.5 kpc, abounds.
Milky Way | Galactic Center
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 an estimated visible diameter between 170,000 and 200,000 light-years (ly). It is estimated to contain 100–400 billion stars and at least that number of planets. The dark matter halo around the Milky Way may span as much as 2 million light years. The Solar System is located at a radius of about 27,000 light-years from the Galactic Center, on the inner edge of the Orion Arm, one of the spiral-shaped concentrations of gas and dust.
Milky Way | Introduction
The Milky Way consists of a bar-shaped core region surrounded by a warped disk of gas, dust and stars. The mass distribution within the Milky Way closely resembles the type Sbc in the Hubble classification, which represents spiral galaxies with relatively loosely wound arms. Astronomers first began to conjecture that the Milky Way is a barred spiral galaxy, rather than an ordinary spiral galaxy, in the 1960s. These conjectures were confirmed by the Spitzer Space Telescope observations in 2005 that showed the Milky Way's central bar to be larger than previously thought.
Milky Way | Structure
This has been called into question by a 2018 study that cited a lower estimate on the mass of the Andromeda Galaxy, combined with preliminary reports on a 2019 study estimating a higher mass of the Milky Way. The Andromeda Galaxy has a diameter of about , making it the largest member of the Local Group in terms of extension, if not mass. The number of stars contained in the Andromeda Galaxy is estimated at one trillion (), or roughly twice the number estimated for the Milky Way.
Andromeda Galaxy | Introduction
The galaxy is approximately 150,000 light years across. This makes it, in comparison, about 1.5 times as large as the Milky Way. The galaxy also has a satellite elliptical galaxy called PGC (Principal Galaxies Catalogue) 1563523.
NGC 52 | Physical Characteristics
The Milky Way is the galaxy that contains our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. The term "Milky Way" is a translation of the Latin ', from the Greek (', "milky circle"). From Earth, the Milky Way appears as a band because its disk-shaped structure is viewed from within. Galileo Galilei first resolved the band of light into individual stars with his telescope in 1610. Until the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe.
Milky Way | Introduction
The Milky Way appears as a hazy band of faint stars. It is the disc of our own galaxy, viewed edge-on from within it. It appears as a 10°-wide band of diffuse light passing all the way around the sky. It crosses the ecliptic at a high angle. Its most prominent feature is a large dust cloud that forms a dark rift in its southern and western part. There is no almanac in the codices that refers specifically to the Milky Way but there are references to it in almanacs concerned with other phenomena.
Maya astronomy | The Milky Way
Many barred spiral galaxies are active, possibly as a result of gas being channeled into the core along the arms. Our own galaxy, the Milky Way, is a large disk-shaped barred-spiral galaxy about 30 kiloparsecs in diameter and a kiloparsec thick. It contains about two hundred billion (2×10) stars and has a total mass of about six hundred billion (6×10) times the mass of the Sun.
Galaxy | Barred spiral galaxy
The diameter of each of the bubbles is about ; they stretch up to Grus and to Virgo on the night-sky of the southern hemisphere. Subsequently, observations with the Parkes Telescope at radio frequencies identified polarized emission that is associated with the Fermi bubbles. These observations are best interpreted as a magnetized outflow driven by star formation in the central of the Milky Way.
Milky Way | Galactic Center
The distance the light from the edge of the observable universe has travelled is very close to the age of the universe times the speed of light, , but this does not represent the distance at any given time because the edge of the observable universe and the Earth have since moved further apart. For comparison, the diameter of a typical galaxy is 30,000 light-years (9,198 parsecs), and the typical distance between two neighboring galaxies is 3 million light-years (919.8 kiloparsecs). As an example, the Milky Way is roughly 100,000–180,000 light-years in diameter, and the nearest sister galaxy to the Milky Way, the Andromeda Galaxy, is located roughly 2.5 million light-years away.
Universe | Size and regions
NGC 1357 has a Hubble classification of Sab, which indicates it is a spiral galaxy with no bar. It is moving from away from the Milky Way at a rate of 2,018 km/s. Its size on the night sky is 3.2' x 2.4' which is proportional to its real size of the 85 000 ly. NGC 1357's surface brightness profile shows a small bulge and a large, fairly exponential disk. However, the automatic bulge-disk fit would give an unreliably large bulge extending through the whole galaxy (lowermost row). A more reasonable fit is obtained by adding another exponential disk component to the inner part of the galaxy (upper profile).
NGC 1357 | Characteristics
This galaxy is approximately 35 thousand light years wide, determined by its apparent size of 11.6 by 1.9 arcmin
NGC 1560 | Introduction
In fact, it is only 11000 light years (3300 parsecs) wide at its widest; our own galaxy, Milky Way, in comparison, is about ten times larger. Dwarf galaxies like these usually have about a billion stars. NGC 5264 also is relatively blue-coloured; this is from it interacting with other galaxies, supplying it with gas for star formation.
NGC 5264 | Introduction
The disk of stars in the Milky Way does not have a sharp edge beyond which there are no stars. Rather, the concentration of stars decreases with distance from the center of the Milky Way. For reasons that are not understood, beyond a radius of roughly 40,000 ly (13 kpc) from the center, the number of stars per cubic parsec drops much faster with radius. Surrounding the galactic disk is a spherical Galactic Halo of stars and globular clusters that extends farther outward, but is limited in size by the orbits of two Milky Way satellites, the Large and Small Magellanic Clouds, whose closest approach to the Galactic Center is about .
Milky Way | Contents
The Galaxy has an apparent size of 0.9 × 0.6 arcmins and a recessional velocity of approximately 5807 kilometers per second. As of such, the redshift of 0.01956 allows an estimate of the galaxies distance using Hubble's law, which puts the object at roughly 260 million light-years from the Sun.
NGC 513 | Description
Dreyer described NGC 125 as "very faint" and "small," with a "brighter middle." It is about 115 thousand light-years across, making it slightly larger than the Milky Way galaxy.
NGC 125 | Visual appearance
The LMC is about twice the diameter of the SMC (14,000 ly and 7,000 ly respectively). For comparison, the Milky Way is about 100,000 ly across. The total mass of these two galaxies is uncertain. Only a fraction of their gas seems to have coalesced into stars and they probably both have large dark matter halos. One recent estimate of the total mass of the LMC is about 1/10 that of the Milky Way. That would make the LMC rather a large galaxy in the current observable universe. Since the sizes of relatively nearby galaxies are highly skewed, the average mass can be a misleading statistic.
Magellanic Clouds | Characteristics
From a viewpoint in the LMC, the Milky Way's total apparent magnitude would be −2.0—over 14 times brighter than the LMC appears to us on Earth—and it would span about 36° across the sky, the width of over 70 full moons. Furthermore, because of the LMC's high galactic latitude, an observer there would get an oblique view of the entire galaxy, free from the interference of interstellar dust that makes studying in the Milky Way's plane difficult from Earth. The Small Magellanic Cloud would be about magnitude 0.6, substantially brighter than the LMC appears to us.
Extraterrestrial sky | From the Large Magellanic Cloud
The band then continues the rest of the way around the sky, back to Sagittarius, dividing the sky into two roughly equal hemispheres.
Milky Way | Appearance
The Galaxy has an apparent size of 1.6 × 0.4 arcmins and as of such is very elongated. It has recessional velocity of approximately 4810 kilometers per second. The distance of NGC 512 from the Solar System can be estimated using Hubble's law, which puts the object at roughly 220 million light-years from the Sun.
NGC 512 | Description
The exact size or mass of the galaxy is not known, but there have been estimates of its mass using the velocities of its companion galaxies. The number of stars estimated within NGC 5962 reaches (1 ± 2.5) × 10 to the 12th power stars.
NGC 5962 | Physical characteristics
The luminosity and size of this galaxy is mid-way between the Large and Small Magellanic Clouds. De Vaucouleurs and associates classed it as type SAc, suggesting more loosely wound arms. It is inclined at an angle of 65° to the line of sight from the Earth. Although appearing as a disk, there is evidence for a non-axisymmetric form of gas distribution, with a suggestion of central bar plus large-scale spiral arms. The inner structure contains many dark lanes and stellar condensations in its disk. There are two strong H II regions, one to each side. The overall star formation rate is y.
NGC 2976 | Introduction
The galaxy is described as "pretty bright", "very small" with a "brighter middle". It is approximately 165,000 light years in diameter and is elongated. The galaxy is famous for its (peanut shell)-shaped bulge, and in 2016 it was discovered that there are two such nested structures, possibly associated with two stellar bars.
NGC 128 | Visual appearance
The galaxy has a diameter of 75 000 light-years.
IC 342 | Introduction
A galaxy is a large gravitational aggregation of stars, dust, gas, and an unknown component termed dark matter. The Milky Way Galaxy is only one of billions of galaxies in the known universe. Galaxies are classified into spirals, ellipticals, irregular, and peculiar. Sizes can range from only a few thousand stars (dwarf irregulars) to 10 stars in giant ellipticals. Elliptical galaxies are spherical or elliptical in appearance. Spiral galaxies range from S0, the lenticular galaxies, to Sb, which have a bar across the nucleus, to Sc galaxies which have strong spiral arms. In total count, ellipticals amount to 13%, S0 to 22%, Sa, b, c galaxies to 61%, irregulars to 3.5% and peculiars to 0.9%.
Galactic orientation | Galaxies
Elliptical galaxies vary greatly in both size and mass with diameters ranging from 3000 lightyears to more than 700,000 lightyears, and masses from 10 to nearly 10 solar masses. This range is much broader for this galaxy type than for any other. The smallest, the dwarf elliptical galaxies, may be no larger than a typical globular cluster, but contain a considerable amount of dark matter not present in clusters. Most of these small galaxies may not be related to other ellipticals. The Hubble classification of elliptical galaxies contains an integer that describes how elongated the galaxy image is. The classification is determined by the ratio of the major ("a") to the minor ("b") axes of the galaxy's isophotes: Thus for a spherical galaxy with "a" equal to "b", the number is 0, and the Hubble type is E0.
Elliptical galaxy | Sizes and shapes
A large enough volume means that the mean motion of galaxies within this volume is equal to the Hubble flow. Astronomers believe the Milky Way is moving at approximately with respect to this local co-moving frame of reference. The Milky Way is moving in the general direction of the Great Attractor and other galaxy clusters, including the Shapley supercluster, behind it. The Local Group (a cluster of gravitationally bound galaxies containing, among others, the Milky Way and the Andromeda Galaxy) is part of a supercluster called the Local Supercluster, centered near the Virgo Cluster: although they are moving away from each other at as part of the Hubble flow, this velocity is less than would be expected given the 16.8 million pc distance due to the gravitational attraction between the Local Group and the Virgo Cluster.
Milky Way | Velocity
The Galaxy has an apparent size of 1.1 × 1.1 arcmins and a recessional velocity of approximately 10954 kilometers per second. It also contains multiple concentric rings. The distance of NGC 511 from the Solar System can be estimated using Hubble's law, which puts the object at nearly 500 million light-years from the Sun.
NGC 511 | Description
The stars in the innermost 10,000 light-years form a bulge and one or more bars that radiate from the bulge. The galactic center is an intense radio source known as Sagittarius A*, a supermassive black hole of 4.100 (± 0.034) million solar masses. Stars and gases at a wide range of distances from the Galactic Center orbit at approximately 220 kilometers per second. The constant rotation speed contradicts the laws of Keplerian dynamics and suggests that much (about 90%) of the mass of the Milky Way is invisible to telescopes, neither emitting nor absorbing electromagnetic radiation. This conjectural mass has been termed "dark matter".
Milky Way | Introduction
The nature of the Milky Way's bar, which extends across the Galactic Center, is also actively debated, with estimates for its half-length and orientation spanning between 1–5 kpc (short or a long bar) and 10–50°. Certain authors advocate that the Milky Way features two distinct bars, one nestled within the other. The bar is delineated by red-clump stars (see also red giant); however, RR Lyrae variables do not trace a prominent Galactic bar. The bar may be surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present in the Milky Way, and most of the Milky Way's star formation activity.
Galactic Center | Distance to the Galactic Center
In 2015, building on the 2002 studies which revealed the Monoceros Ring, an international team of scientists sorting and sifting through galactic data from the Sloan Digital Sky Survey suggested that the Milky Way is actually 50 percent larger than previously thought. It turned out that the disk of the Milky Way is not just a disk of stars in a flat plane, but is instead corrugated. As it radiates outward from the Sun, there appear to be at least four ripples in the disk of the Milky Way. Scientists assume that this pattern is going to be found throughout the disk.
Monoceros Ring | Dispute
According to Jamil Ragep, the Persian astronomer Naṣīr al-Dīn al-Ṭūsī (1201–1274) in his "Tadhkira" writes: "The Milky Way, i.e. the Galaxy, is made up of a very large number of small, tightly clustered stars, which, on account of their concentration and smallness, seem to be cloudy patches. Because of this, it was likened to milk in color."
Milky Way | Astronomical history
To put this in perspective, the mass of all such books required to write out a googolplex would be vastly greater than the masses of the Milky Way and the Andromeda galaxies combined (by a factor of roughly 2.0 x 10), and greater than the mass of the observable universe by a factor of roughly 7 x 10.
Googolplex | Size
The Galactic Center is marked by an intense radio source named Sagittarius A* (pronounced Sagittarius A-star). The motion of material around the center indicates that Sagittarius A* harbors a massive, compact object. This concentration of mass is best explained as a supermassive black hole (SMBH) with an estimated mass of 4.1–4.5 million times the mass of the Sun. The rate of accretion of the SMBH is consistent with an inactive galactic nucleus, being estimated at around per year. Observations indicate that there are SMBHs located near the center of most normal galaxies. The nature of the Milky Way's bar is actively debated, with estimates for its half-length and orientation spanning from and 10–50 degrees relative to the line of sight from Earth to the Galactic Center.
Milky Way | Galactic Center
To determine the number of stars in the Milky Way, volumes in cubic kiloparsecs (kpc) are selected in various directions. All the stars in these volumes are counted and the total number of stars statistically determined. The number of globular clusters, dust clouds, and interstellar gas is determined in a similar fashion. To determine the number of galaxies in superclusters, volumes in cubic megaparsecs (Mpc) are selected. All the galaxies in these volumes are classified and tallied. The total number of galaxies can then be determined statistically. The huge Boötes void is measured in cubic megaparsecs. In physical cosmology, volumes of cubic gigaparsecs (Gpc) are selected to determine the distribution of matter in the visible universe and to determine the number of galaxies and quasars.
Parsec | Volume units
The Color-color diagram shows ~100 GPs (green crosses), 10,000 comparison galaxies (red points) and 9,500 comparison quasar (purple stars) at similar redshifts to the GPs. The black lines show how these figures are on the diagram. Comparing a GP to the Milky Way can be useful when trying to visualize these star-forming rates. An average GP has a mass of ~3,200 million (~3,200 million solar masses). The Milky Way (MW) is a spiral galaxy and has a mass of ~1,125,000, million (~1,125,000 million solar masses). So the MW has the mass of ~390 GPs.
Pea galaxy | Analysis of the Cardamone 2009 paper
For the Milky Way, the galactic habitable zone is commonly believed to be an annulus with an outer radius of about 10 kiloparsecs and an inner radius close to the Galactic Center, both of which lack hard boundaries. NGC 6118 is difficult to see with a small telescope. Amateur astronomers have nicknamed it the "Blinking Galaxy", as it has a tendency to flick in and out of view with different eye positions.
NGC 6118 | Introduction
PKS1353-341 is estimated to have a total mass of 690 trillion solar masses, making it over 1000 times as massive as the Milky Way. Its central galaxy is an extremely bright quasar at a luminosity 46 billion times that of the Sun. This brightness is produced by a superheated disk of matter circling the supermassive black hole at the center of the central galaxy.
PKS1353-341 | Properties
Like many other galaxies of similar type, the Milky Way consists of a large mass of stars shaped into the form of a relatively flat disc by gravity. The disc is rotating, with the dense central body of stars moving at greater speeds than those toward the rim of the disc. As a result, the pattern of stars within the Galaxy as viewed from directly above or below the disc has formed into a spiral. Because of localised gravitational variations, the spiral pattern has itself formed several distinct 'spiral arms', where particularly large numbers of stars can be found.
Norma Arm | Introduction
The smallest dwarf galaxies of the Milky Way are only 500 light-years in diameter. These include Carina Dwarf, Draco Dwarf, and Leo II Dwarf. There may still be undetected dwarf galaxies that are dynamically bound to the Milky Way, which is supported by the detection of nine new satellites of the Milky Way in a relatively small patch of the night sky in 2015. There are also some dwarf galaxies that have already been absorbed by the Milky Way, such as the progenitor of Omega Centauri. In 2014 researchers reported that most satellite galaxies of the Milky Way lie in a very large disk and orbit in the same direction.
Milky Way | Environment
Whirlpool Galaxy lies 23 million light-years from Earth and has an estimated diameter of 76,000 light-years. Overall the galaxy is about 43% the size of the Milky Way. Its mass is estimated to be 160 billion solar masses. or around 10.3% of the mass of Milky Way Galaxy. A black hole, once thought to be surrounded by a ring of dust, but now believed to be partially occluded by dust instead, exists at the heart of the spiral. A pair of ionization cones extend from the active galactic nucleus.
Whirlpool Galaxy | Properties
This is what determines the size of the HCSS: its radius is roughly the radius of the orbit that has the same velocity around the SMBH as the kick velocity, or where is the mass of the SMBH and the gravitational constant. The size works out to be roughly one-half parsec (pc) (two light years) for a kick of 1000 km/s and a SMBH mass of 100 million solar masses. The largest HCSSs would have sizes of about 20 pc, roughly the same as a large globular cluster, and the smallest would be about a thousandth of a parsec across, smaller than any known star cluster.
Hypercompact stellar system | Properties
The size of a Solar System object can be deduced from its optical magnitude, its distance, and its albedo. Objects appear bright to Earth observers either because they are large or because they are highly reflective. If their reflectivity (albedo) can be ascertained, then a rough estimate can be made of their size. For most distant objects, the albedo is unknown, but Haumea is large and bright enough for its thermal emission to be measured, which has given an approximate value for its albedo and thus its size. However, the calculation of its dimensions is complicated by its rapid rotation.
Haumea | Size, shape, and composition
At an estimated 140,000 light-years in diameter, NGC 1 is roughly the same size as our own galaxy, the Milky Way, which is believed to be approximately 160,000 light-years across. Although its apparent magnitude of 13.65 lets the galaxy appear too faint to see it in the sky with the naked eye, its absolute magnitude of -22.08 makes NGC 1 two to three times more luminous than our home galaxy. The galaxy is 4.0 Mly away from the 80,000 light-year wide galaxy UGC 69, its nearest major neighbor. NGC 1 has a visual size of 1.6' × 1.2'. Being classified as a SABbc class galaxy using the Hubble sequence and the De Vaucouleurs system as an extension, NGC 1 is a spiral galaxy with the presence of a weak nuclear bar and loosely wound arms.
NGC 1 | General
This galaxy has an apparent diameter of approximately 1.3 million light-years, occupying 1.1' of the Earth's sky. It holds approximately 15 trillion stars. NGC 262 was tidally disturbed by the gravitational forces of smaller galaxies, which resulted in its large size. NGC 262 is very unusual, since it is 10 times larger than a regular spiral galaxy of its type. According to Morris and Wannier, NGC 262 is surrounded by a huge cloud of neutral hydrogen that is probably caused by the tidal stripping of smaller galaxies. The cloud has an apparent mass of approximately 50 billion solar masses at a distance of 88 kiloparsecs (287,000 light-years) from the nucleus of NGC 262 and extending up to 300 kiloparsecs (1 million light-years) away.
NGC 262 | Size
A study of 27 Milky Way neighbors found that in all dwarf galaxies, the central mass is approximately 10 million solar masses, regardless of whether the galaxy has thousands or millions of stars. This has led to the suggestion that galaxies are largely formed by dark matter, and that the minimum size may indicate a form of warm dark matter incapable of gravitational coalescence on a smaller scale.
Galaxy | Dwarfs
It is a relatively small, compact spiral with a diameter of , multiple flocculent arms and a bright, dusty nucleus that does not appear to be active. However, the neutral hydrogen in the galaxy is spread over a diameter five times larger than its visible size. Although it appears nearly face-on, the galactic plane is inclined by an angle of 28° to the line of sight from the Earth, with the major axis being oriented along a position angle of 116°. The outer part of the disk appears to be warped, so that the major axis is not quite perpendicular to the minor axis, and the morphology is somewhat disrupted.
NGC 278 | Introduction
The total mass of M87 may be 200 times that of the Milky Way.
Messier 87 | Properties
Of the galaxies confirmed to be in orbit, the largest is the Sagittarius Dwarf Elliptical Galaxy, which has a diameter of or roughly a twentieth that of the Milky Way.
Satellite galaxies of the Milky Way | Introduction
In 2004, Quaoar was estimated to have a diameter of with an uncertainty of , using Hubble's measurements. Given its distance Quaoar is on the limit of Hubble's resolution of 40 milliarcseconds and its image is consequently "smeared" on a few adjacent pixels. By comparing carefully this image with the images of stars in the background and using a sophisticated model of Hubble optics (PSF), Brown and Trujillo were able to find the best-fit disk size that would give a similar blurred image. This method was also applied by the same authors to measure the size of the dwarf planet Eris.
50000 Quaoar | Size
The galaxy appears very dim in the sky as it only has an apparent visual magnitude of 14.4. It can be classified as type E using the Hubble Sequence. The object's distance of roughly 240 million light-years from the Solar System can be estimated using its redshift and Hubble's law.
NGC 519 | Description
The Milky Way contains between 100 and 400 billion stars and at least that many planets. An exact figure would depend on counting the number of very-low-mass stars, which are difficult to detect, especially at distances of more than from the Sun. As a comparison, the neighboring Andromeda Galaxy contains an estimated one trillion (10) stars. The Milky Way may contain ten billion white dwarfs, a billion neutron stars, and a hundred million stellar black holes. Filling the space between the stars is a disk of gas and dust called the interstellar medium. This disk has at least a comparable extent in radius to the stars, whereas the thickness of the gas layer ranges from hundreds of light-years for the colder gas to thousands of light-years for warmer gas.
Milky Way | Contents
The galaxy appears very dim in the sky as it only has an apparent visual magnitude of 13.3 and thus can only be observed with telescopes. It can be classified as type S0 using the Hubble Sequence. The object's distance of roughly 95.6 million light-years from the Solar System can be estimated using its redshift and Hubble's law.
NGC 525 | Description
Eridanus II does not have a spherical shape, and its ellipticity (ε) has been estimated at about 0.45 (Crnojević et al., 2016; Koposov et al., 2015). Its size depends on assumptions about mass distribution and three-dimensional structure. Crnojević et al. (2016) find that their data are consistent with a simple exponential distribution of mass and a half-light radius (a radius enclosing half the luminosity of the galaxy) of 277 ±14 pc (~890 light years), with an apparent half-light diameter of 4.6 arcmin to observers on Earth. A galactic structure of this small size is not expected to show signs of coherent rotation.
Eridanus II | Size, shape, and rotation
This was explained by the interstellar dust scattered through the galaxy, resulting in the absorption (extinction) of light or interstellar extinction of light. Trumpler further studied and catalogued open clusters in order to determine the size of the Milky Way galaxy. At first he thought his analysis placed an upper limit on the Milky Way's diameter of about 10,000 parsecs with the Sun located somewhat near the center although he later revised this. While cataloguing open clusters, he also devised a system for their classification according to the number of stars observed within them, how concentrated these stars are in the center of the cluster and the range of their apparent brightness.
Robert Julius Trumpler | Career
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*, has a mass four million times greater than the Sun.
Galaxy | Introduction
At a distance of nearly 63 million light-years, it is a member of Fornax Cluster. Its size on night sky is 1.4' x 1.0' which is proportional to its real size of 30,000 light-years, which makes it one of the smaller galaxies in Fornax Cluster.
NGC 1460 | Distance and size
The galaxy is classified as a supergiant elliptical (E) to lenticular (S0) and is the brightest galaxy in A2029 (hence its other designation A2029-BCG; BCG meaning "brightest cluster galaxy"). The galaxy's morphological type is debated due to it possibly being shaped like a flat disc but only visible from Earth at its broadest dimensions. However, most lenticulars have sizes ranging from . IC 1101 is among the largest known galaxies, but there is debate in the astronomical literature about how to define the size of such a galaxy. Photographic plates of blue light from the galaxy (sampling stars excluding the diffuse halo) yield an effective radius (the radius within which half the light is emitted) of .
IC 1101 | Characteristics
Galaxy diameters are included and the classifications and descriptions are given in such a way as to provide as accurate an account as possible of the appearance of the galaxies on the prints. The accuracy of coordinates is only what is necessary for identifications purposes.
Uppsala General Catalogue | Introduction
On the other hand, Curtis argued that the Milky way was much smaller and that the observed nebulae were in fact galaxies similar to our own Milky Way. This debate was not settled until late 1923 when the astronomer Edwin Hubble measured the distance to M31 (currently known as the Andromeda galaxy) using Cepheid Variable stars. By measuring the period of these stars, Hubble was able to estimate their intrinsic luminosity and upon combining this with their measured apparent magnitude he estimated a distance of 300 kpc, which was an order-of-magnitude larger than the estimated size of the universe made by Shapley.
Satellite galaxy | Early 20th century
The Initial Mass Function of LH 95 does not seem to differ from that typical for the Milky Way.
LH 95 | Introduction
This makes the Milky Way difficult to see from brightly lit urban or suburban areas, but very prominent when viewed from rural areas when the Moon is below the horizon. Maps of artificial night sky brightness show that more than one-third of Earth's population cannot see the Milky Way from their homes due to light pollution. As viewed from Earth, the visible region of the Milky Way's galactic plane occupies an area of the sky that includes 30 constellations. The Galactic Center lies in the direction of Sagittarius, where the Milky Way is brightest. From Sagittarius, the hazy band of white light appears to pass around to the galactic anticenter in Auriga.
Milky Way | Appearance
The galaxy recedes from the Milky Way at the speed of about 241 km/s. The visible radius of Dwingeloo 2 is approximately 2′, which at the distance of 3 Mpc corresponds to about 2 kpc. Dwingeloo 2 has a well defined rotating HI disk inclined at approximately 69° with respect to observer. The distribution of the neutral hydrogen in Dwingeloo 2 is quite irregular, and it is detected as far as 3.2 kpc from the center of the galaxy. The total mass of the galaxy within this radius is estimated at 2.3 billion Solar masses, while the mass of the neutral hydrogen is estimated at about 100 million Solar masses.
Dwingeloo 2 | Introduction
Dark regions within the band, such as the Great Rift and the Coalsack, are areas where interstellar dust blocks light from distant stars. The area of sky that the Milky Way obscures is called the Zone of Avoidance. The Milky Way has a relatively low surface brightness. Its visibility can be greatly reduced by background light, such as light pollution or moonlight. The sky needs to be darker than about 20.2 magnitude per square arcsecond in order for the Milky Way to be visible. It should be visible if the limiting magnitude is approximately +5.1 or better and shows a great deal of detail at +6.1.
Milky Way | Appearance
4 billion solar masses) than the black hole at our Milky Way's center, one of the largest known. The physics that creates the jets is poorly understood, with a likely energy source being matter ejected perpendicular to the accretion disc of the central black hole.
Hercules A | Galaxy
Three stellar components with varying scale heights can be distinguished within the disc of the Milky Way (MW): the "young thin disc", the "old thin disc", and the "thick disc". The "young thin disc" is a region in which star formation is taking place and contains the MW's youngest stars and most of its gas and dust. The scale height of this component is roughly 100 pc. The "old thin disc" has a scale height of approximately 325 pc while the "thick disc" has a scale height of 1.5 kpc. Although stars move primarily within the disc, they exhibit a random enough motion in the direction perpendicular to the disc to result in various scale heights for the different disc components.
Galactic disc | Structure of the Milky Way Disc
John Herschel described the galaxy as "faint, pretty large, pretty much extended, very gradually brighter middle."
NGC 131 | Appearance
NGC 1375's size on night sky is 2.3' x 0.9′ which with galaxy's distance gives diameter of 23,000 light-years.
NGC 1375 | Distance and diameter estimates
M101 is a large galaxy, with a diameter of 170,000 light-years. By comparison, the Milky Way has a diameter of 100,000 light-years. It has around a trillion stars, twice the number in the Milky Way. It has a disk mass on the order of 100 billion solar masses, along with a small central bulge of about 3 billion solar masses. M101 has a high population of H II regions, many of which are very large and bright. H II regions usually accompany the enormous clouds of high density molecular hydrogen gas contracting under their own gravitational force where stars form.
Pinwheel Galaxy | Structure and composition
The measured angular diameter of this star, after correcting for limb darkening, is . At its estimated distance, this yields a physical size of 88 times the radius of the Sun.
ET Virginis | Introduction
The cloud is spiral shaped with at least one arm, and possibly another one extending throughout the galaxy.
NGC 262 | Size
It is at the edge of Fornax Cluster. Near the galaxy is bright foreground star that makes deep observations more difficult, so the galaxy's apparent magnitude is 12.6. Its size on night sky is 2.5' x 2.2' which is, along with it distance, proportional to real size of 45,000 light-years. IC 1993 is one of the 25 galaxies known to have rings or partial rings. Most resemble local collisional ring galaxies in morphology, size, and clumpy star formation. Clump ages range from to yr, and clump masses go up to several × solar masses, based on color evolution models. The clump ages are consistent with the expected lifetimes of ring structures if they are formed by collisions.
IC 1993 | Introduction
The galaxy is approximately 200,000 light-years across, in between the sizes of the Andromeda Galaxy and our home galaxy, the Milky Way. NGC 1232 and its satellite are part of the Eridanus cluster of galaxies, along with NGC 1300.
NGC 1232 | Introduction
Observed angular sizes for HVCs range from 10 degrees down to the resolution limit of the observations. Typically, high resolution observations eventually show that larger HVCs are often composed of many smaller complexes. When detecting HVCs solely via HI emission, all of the HVCs in the Milky Way cover about 37% of the night sky. Most HVCs are somewhere between 2 and 15 kilo parsecs (kpc) across.
High-velocity cloud | Size
Certain authors advocate that the Milky Way features two distinct bars, one nestled within the other. However, RR Lyrae variables do not trace a prominent Galactic bar. The bar may be surrounded by a ring called the "5-kpc ring" that contains a large fraction of the molecular hydrogen present 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. X-ray emission from the core is aligned with the massive stars surrounding the central bar and the Galactic ridge. In 2010, two gigantic spherical bubbles of high energy emission were detected to the north and the south of the Milky Way core, using data from the Fermi Gamma-ray Space Telescope.
Milky Way | Galactic Center
Two smaller galaxies and a number of dwarf galaxies in the Local Group orbit the Milky Way. The largest of these is the Large Magellanic Cloud with a diameter of 14,000 light-years. It has a close companion, the Small Magellanic Cloud. The Magellanic Stream is a stream of neutral hydrogen gas extending from these two small galaxies across 100° of the sky. The stream is thought to have been dragged from the Magellanic Clouds in tidal interactions with the Milky Way. Some of the dwarf galaxies orbiting the Milky Way are Canis Major Dwarf (the closest), Sagittarius Dwarf Elliptical Galaxy, Ursa Minor Dwarf, Sculptor Dwarf, Sextans Dwarf, Fornax Dwarf, and Leo I Dwarf.
Milky Way | Environment
Size in general is the magnitude or dimensions of a thing. More specifically, "geometrical size" (or "spatial size") can refer to linear dimensions (length, width, height, diameter, perimeter), area, or volume. Size can also be measured in terms of mass, especially when assuming a density range. In mathematical terms, "size is a concept abstracted from the process of measuring by comparing a longer to a shorter". Size is determined by the process of comparing or measuring objects, which results in the determination of the magnitude of a quantity, such as length or mass, relative to a unit of measurement. Such a magnitude is usually expressed as a numerical value of units on a previously established spatial scale, such as meters or inches.
Size | Introduction
As an elliptical galaxy, the galaxy is a spheroid rather than a flattened disc, accounting for the substantially larger mass of M87. Within a radius of , the mass is times the mass of the Sun, which is double the mass of the Milky Way galaxy. As with other galaxies, only a fraction of this mass is in the form of stars: M87 has an estimated mass to luminosity ratio of ; that is, only about one part in six of the galaxy's mass is in the form of stars that radiate energy. This ratio varies from 5 to 30, approximately in proportion to "r" in the region of from the core.
Messier 87 | Properties
Discovered by 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. It is heavily obscured by interstellar matter due to its location close to the galactic plane of the Milky Way, with a dimming of ~1.5 magnitudes. 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 or very large supernova remnant, and which may have been formed by an open cluster containing massive stars.
NGC 6946 | Introduction
Another technique for measuring the angular size of stars is through occultation. By precisely measuring the drop in brightness of a star as it is occulted by the Moon (or the rise in brightness when it reappears), the star's angular diameter can be computed. Stars range in size from neutron stars, which vary anywhere from 20 to in diameter, to supergiants like Betelgeuse in the Orion constellation, which has a diameter about 1,000 times that of our sun. Betelgeuse, however, has a much lower density than the Sun.
Star | Diameter
The galaxy has an apparent visual magnitude of 12.5 and can be classified as type S0 using the Hubble Sequence. The object's distance of roughly 190 million light-years from the Solar System can be estimated using its redshift and Hubble's law.
NGC 517 | Description
But it is small, appearing only 4' by 2'. The morphological classification of this galaxy is SAB(rs)bc, indicating a spiral galaxy with a weak central bar (SAB), an incomplete ring structure around the bar (rs), and moderately–wound arms (bc). The plane of the galactic disk is inclined by 64° to the line of sight from the Earth, with the major axis aligned along a position angle of 178°. Within the galaxy's core is an active galactic nucleus tentatively classified as a type I Seyfert. The central supermassive black hole has a relatively low mass, estimated as . The core is a source for X-ray emission that is seen to vary dramatically on time scales as low as hours.
NGC 7314 | Introduction
The Local Group is the galaxy group that includes the Milky Way. It has a total diameter of roughly , and a total mass of the order of . It consists of two clusters of galaxies in a "dumbbell" shape: the Milky Way and its satellites form one lobe, and the Andromeda Galaxy and its satellites constitute the other. The two clusters are separated by about and move towards one another with a velocity of . The group itself is a part of the larger Virgo Supercluster, which may be a part of the Laniakea Supercluster. The total number of galaxies in the Local Group is unknown as some are occluded by the Milky Way; however, at least 80 such objects are known (most of which are dwarf galaxies).
Local Group | Introduction
Each stream removed is characterized by six parameters: percent of stars in the stream; the angular position in the stripe; the three spatial components (two angles, plus the radial distance from Earth) defining the removed cylinder; and a measure of width. For each search, the server application keeps track of a population of individual stars, each of which is attached to a possible model of the Milky Way.
MilkyWay@home | Purpose and design
The Milky Way is the galaxy that contains our Solar System. Milky Way may also refer to:
Milky Way (disambiguation) | Introduction
The galaxy was observed by the Hubble Space Telescope. It was found that it has a central disk seen nearly face-on with a diameter of 1".8. Inside the disk is an inner ring with a diameter of circa 0".44 arcseconds, maybe part of a hardly visible spiral structure. There is also a linear dust feature sticking out of the disk with nearly the same axis as the radio jet. H-alpha and [N II] emission presented a peak at the centre of the dusk disk and also was found to form a ring around the peak, which had two brighter spots lying diametrically opposed.
NGC 541 | Introduction
This came as a surprise: according to standard cosmology, the satellite galaxies should form in dark matter halos, and they should be widely distributed and moving in random directions. This discrepancy is still not fully explained.
Milky Way | Environment
Carrignan et al. (1997) measured the velocity differences and projected separations of nine galaxies they identified as satellites of NGC 5084 and using different equations they estimated the mass of NGC 5084 to be between 6 x 10 and 1 x 10 , which was at that time the highest mass ever derived for a disk galaxy. They estimated the optical diameter of NGC 5084 to be 74 kpc (241 Kly).
NGC 5084 | Mass and size estimates