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GD-1
In 2006, GD-1 is identified as a moving group of old, metal-poor stars located at 8.5 kpc above the galactic disk and spanning 63 degrees across the sky. The stream was formed after a globular cluster was disrupted by tidal forces, possibly from the gravitational field of the Milky Way. The stream is located within the Field of Streams, a region of sky in the galactic northern hemisphere containing many stellar streams, the most prominent of which is the Sagittarius stream. The stream's progenitor is believed to be a globular cluster based on the stream's radial velocity The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity ..., location and the age of the stars within, but the specific cluster has not been identified. References Milky Way Stellar streams Astronomical objec ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stellar Streams
This is a list of stellar streams. A stellar stream is an association of stars orbiting a galaxy. It was once a globular cluster or dwarf galaxy that has now been torn apart and stretched out along its orbit by tidal forces. An exception in the list about Milky Way streams given below is the Magellanic Stream, composed of gas (mostly hydrogen), although in 2023 a population of stars has been described inside it. Local Group streams Milky Way streams Andromeda Galaxy streams Streams beyond the Local Group Due to new deeper sky surveys, such as the Dark Energy Spectroscopic Instrument#DESI Legacy Imaging Surveys, DESI Legacy Imaging Survey, a large number of streams are to be expected to be discovered in the future. An initial search in 2023 by Martínez-Delgado et al. searched 389 galaxies and found 89 candidates with stellar streams (22,9%). They plan to search about 3100 galaxies, which might yield hundreds of candidates. In the pasts less sensitive surveys such as Sloan D ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Moving Group
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space. Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as the internal kinematics of more distant galaxies. Measurement of the kinematics of stars in different subcomponents of the Milky Way including the thin disk, the thick disk, the bulge, and the stellar halo provides important information about the formation and evolutionary history of our Galaxy. Kinematic measurements can also identify exotic phenomena such as hypervelocity stars escaping from the Milky Way, which are interpreted as the result of gravitational encounters of binary stars with the supermassive black hole at the Galactic Center. Stellar kinematics is related to but distinct from the subject of stellar dynamics, which involves the theoretical study or modeling of the motions of stars under the influence of gravity. Stella ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Globular Cluster
A globular cluster is a spheroidal conglomeration of stars that is bound together by gravity, with a higher concentration of stars towards its center. It can contain anywhere from tens of thousands to many millions of member stars, all orbiting in a stable, compact formation. Globular clusters are similar in form to dwarf spheroidal galaxy, dwarf spheroidal galaxies, and though globular clusters were long held to be the more luminous of the two, discoveries of outliers had made the distinction between the two less clear by the early 21st century. Their name is derived from Latin (small sphere). Globular clusters are occasionally known simply as "globulars". Although one globular cluster, Omega Centauri, was observed in antiquity and long thought to be a star, recognition of the clusters' true nature came with the advent of telescopes in the 17th century. In early telescopic observations, globular clusters appeared as fuzzy blobs, leading French astronomer Charles Messier to incl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milky Way
The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galaxy, which are so far away that they cannot be individually distinguished by the naked eye. The Milky Way is a barred spiral galaxy with a Galaxy#Isophotal diameter, D25 isophotal diameter estimated at , but only about 1,000 light-years thick at the spiral arms (more at the bulge). Recent simulations suggest that a dark matter area, also containing some visible stars, may extend up to a diameter of almost 2 million light-years (613 kpc). The Milky Way has several List of Milky Way's satellite galaxies, satellite galaxies and is part of the Local Group of galaxies, forming part of the Virgo Supercluster which is itself a component of the Laniakea Supercluster. It is estimated to contain 100–400 billion stars and at least that number of pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Field Of Streams
The Field of Streams is a patch of sky where several stellar streams are visible and crisscross. It was discovered by Vasily Belokurov and Daniel Zucker's team in 2006 by analyzing the Sloan Digital Sky Survey II (SDSS-II) data. The team named the area ''Field of Streams'' because of so many crisscrossing trails of stars. The Sagittarius Stream of the Sagittarius Dwarf Elliptical Galaxy (SagDEG) dominates the ''Field''. It has a split trail within the area of the Field of Streams, because SagDEG has wrapped around the Milky Way Galaxy multiple times, which has resulted in overlapping trails. The forking of the trail has made it possible to infer the organization of dark matter in the inner halo of the Milky Way Galaxy, resulting in the determination that it is distributed in a round spherical manner, as opposed to the expected flattened spheroid. The shape of the streams also implies that the dark matter is very cold, due to the thin trails, and persisting existence. Also app ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sagittarius Stream
In astronomy, the Sagittarius Stream is a long, complex structure made of stars that wrap around the Milky Way Galaxy in an orbit that nearly crosses the galactic poles. It consists of tidally stripped stars from the Sagittarius Dwarf Elliptical Galaxy, resulting from the process of merging with the Milky Way over a period of billions of years. This stellar stream was originally proposed in 1995 by Donald Lynden-Bell after analyzing the distribution of globular clusters in the Milky Way. The actual structure was identified by Newberg and associates (2002) plus Majewski and associates (2003) using data from the 2MASS and SDSS surveys. In 2006, Belokurov and his collaborators found that the Sagittarius Stream has two branches. When the progenitor object was shredded apart during the interaction, it sent oscillations (analogous to sound waves) through the Milky Way spiral arm structure. The effects of the oscillations are observed today as layers of alternately denser and sparser ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radial Velocity
The radial velocity or line-of-sight velocity of a target with respect to an observer is the rate of change of the vector displacement between the two points. It is formulated as the vector projection of the target-observer relative velocity onto the relative direction or line-of-sight (LOS) connecting the two points. The radial speed or range rate is the temporal rate of the distance or range between the two points. It is a signed scalar quantity, formulated as the scalar projection of the relative velocity vector onto the LOS direction. Equivalently, radial speed equals the norm of the radial velocity, modulo the sign. In astronomy, the point is usually taken to be the observer on Earth, so the radial velocity then denotes the speed with which the object moves away from the Earth (or approaches it, for a negative radial velocity). Formulation Given a differentiable vector \mathbf r \in \mathbb^3 defining the instantaneous relative position of a target with respe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
