Misplaced Pages

#149850

35-685: (Redirected from Sagittarius Dwarf ) Sagittarius Dwarf Galaxy may refer to: The Sagittarius Dwarf Spheroidal Galaxy (also known as the Sagittarius Dwarf Elliptical Galaxy), a satellite galaxy of the Milky Way The Sagittarius Dwarf Irregular Galaxy , a small member of the Local Group Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with

70-546: A combination of Gaia and Tycho-2 data for those objects in both catalogues, "light curves and characteristics for about 3000 variable stars, and positions and magnitudes for more than 2000 extragalactic sources used to define the celestial reference frame". The second data release (DR2), which occurred on 25 April 2018, is based on 22 months of observations made between 25 July 2014 and 23 May 2016. It includes positions, parallaxes and proper motions for about 1.3 billion stars and positions of an additional 300 million stars in

105-511: A large area of the sky. Sgr dSph appears to be an older galaxy with little interstellar dust, composed largely of Population II stars, older and metal-poor, as compared to the Milky Way. No neutral hydrogen gas related to Sgr dSph has been found. Further discoveries by astrophysics teams from both the University of Virginia and the University of Massachusetts Amherst , drawing upon

140-573: A million stars from that region. The full data release for the five-year nominal mission, DR4, will include full astrometric, photometric and radial-velocity catalogues, variable-star and non-single-star solutions, source classifications plus multiple astrophysical parameters for stars, unresolved binaries, galaxies and quasars, an exo-planet list and epoch and transit data for all sources. Most measurements in DR4 are expected to be 1.7 times more precise than DR2; proper motions will be 4.5 times more precise. DR4

175-407: A near right angle to the plane of the Milky Way. Sgr dSph has at least nine known globular clusters . One, M 54 , appears to reside at its core, while three others reside within the main body of the galaxy: Terzan 7 , Terzan 8 and Arp 2 . Additionally, Palomar 12 , Whiting 1 , NGC 2419 , NGC 4147 , and NGC 5634 are found within its extended stellar streams . However, this

210-531: 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 contend that Sgr dSph has been in orbit around

245-559: A selection was made from more than 100,000 objects that were used for the calibration. These are well-observed objects selected according to Stetson Secondary Standards, but only Gaia data were used. A list of quasars based on the Large Quasar Astrometric Catalog was prepared for IGSL. This in turn goes back to the Sloan Digital Sky Survey. From the more than one million objects, a selection of 150,000 quasars

280-785: A separate catalog of objects from several other catalogues was compiled, which roughly represents the state of knowledge of astronomy at the beginning of the Gaia mission. The Attitude Star Catalog is a subset of the IGSL, required for the first approximation in the iterative evaluation of the Gaia data. A first version was created in 2013, a more refined version in April 2014. In total, the Attitude Star Catalog contains 8,173,331 entries with information on position, proper motion and magnitude. Starting with Gaia DR2,

315-693: A special data set, the Gaia Andromeda Photometric Survey (GAPS), providing a photometric time series for about 1 million sources located in a 5.5-degree radius field centered on the Andromeda galaxy. The release dates of EDR3 and DR3 were delayed by the effects of the COVID-19 pandemic on the Gaia Data Processing and Analysis Consortium. Gaia Focused Product Release from October 2023 focused on Omega Centauri and contained more that half

350-665: Is an unusually low number of globular clusters, and an analysis of VVV and Gaia EDR3 data has found at least twenty more. The newly discovered globular clusters tend to be more metal-rich than previously known globular clusters. Sgr dSph has multiple stellar populations , ranging in age from the oldest globular clusters (almost as old as the universe itself) to trace populations as young as several hundred million years (mya) . It also exhibits an age- metallicity relationship, in that its old populations are metal poor ( [Fe/H] = −1.6 ± 0.1 ) while its youngest populations have super-solar abundances. Based on its current trajectory,

385-498: Is based on observations of 492,006 sources believed to be quasars and has been described as "the first full-fledged optical realisation of the ICRS ... built only on extragalactic sources." Comparison of the positions of 2,843 sources common to Gaia –CRF2 and a preliminary version of the ICRF3 shows a global agreement of 20 to 30 μas, although individual sources may differ by several mas. Since

SECTION 10

#1733086332150

420-559: Is expected to be released no earlier than mid-2026. The last catalogue, DR5, will consist of all data collected during the lifespan of the mission. It will be 1.4 times more precise than DR4, while proper motions will be 2.8 times more precise than DR4. It will be published no earlier than the end of 2030. The Gaia Archive is a catalogue that contains positions and brightnesses for 1.7 billion stars , including distances and proper motions for more than 1.3 billion stars. An outreach application, Gaia Sky , has been developed to explore

455-434: Is found to have galactocentric distances that oscillate between ≈13 and ≈41 kpc with a period of 550 to 750 million years. The last perigalacticon was approximately fifty million years ago. Also in 1999, Jiang & Binney found that it may have started its infall into the Milky Way at a point more than 200 kpc away if its starting mass was as large as ≈10 M ☉ . The models of both its orbit and

490-460: The 2MASS Two-Micron All Sky Infrared Survey data, revealed the entire loop-shaped structure. In 2003 with the aid of infrared telescopes and super computers, Steven Majewski, Michael Skrutskie, and Martin Weinberg were able to help create a new star map, picking out the full Sagittarius Dwarf presence, position, and looping shape from the mass of background stars and finding this smaller galaxy to be at

525-407: The Gaia archive. The Initial Gaia Source List (IGSL) is a star catalogue of 1.2 billion objects created in support of the Gaia mission. The mission should have delivered a catalogue based entirely on its own data. For the first catalogue, Gaia DR1, a way was needed to be able to assign the observations to an object and to compare them with the objects from other star catalogues. For this purpose,

560-586: The International Celestial Reference Frame (ICRF3) . Included is the Gaia Catalogue of Nearby Stars (GCNS), containing 331,312 stars within (nominally) 100 parsecs (330 light-years). The full DR3, published on 13 June 2022, includes the EDR3 data plus Solar System data; variability information; results for non-single stars, for quasars, and for extended objects; astrophysical parameters; and

595-554: The Attitude Star Catalog was replaced with a new list generated from the Gaia Main Data Base (MDB), using the same criteria. IGSL contains a list of about 200 stars of different spectral classes and magnitudes needed for calibration of the photometric measurements. It is the result of the Gaia Spectrophotometric Standard Stars Survey (SPSS), a selection of stars using Earth-based data in advance of

630-491: The European Space Agency, designed primarily to investigate the origin, evolution and structure of the Milky Way, delivered the largest and most precise census of positions, velocities and other stellar properties of more than a billion stars, which showed that Sgr dSph had caused perturbations in a set of stars near the Milky Way's core, causing unexpected rippling movements of the stars triggered when it sailed past

665-424: The Gaia mission. Previous catalogues for calibrating magnitudes could not be used for the mission because many of these objects are too bright for Gaia to detect. It was anticipated that some of the stars selected may be previously unrecognized doubles or variable stars that would need to be deleted from the catalogue; for this reason the list contains more stars than necessary. For Gaia EDR3 (Early Data Release 3),

700-635: The Max Planck Institute for Astronomy in La Silla, Chile. It contains precise positions, UBV I photometry for the southern field and the corresponding magnitudes. The northern part was created with the Canada–France–Hawaii Telescope on Mauna Kea, Hawaii. The GEPC v3.0 catalogue contains 612,946 objects from a field of one square degree each at the north and south poles. The north pole is relatively sparse and contains 164,468 objects, while

735-475: The Milky Way between 300 and 900 million years ago. A 2019 study by TCU Graduate Student Matthew Melendez and co-authors concluded that Sgr dSph had a decreasing metallicity trend as a function of radius, with a larger spread in metallicity in the core relative to the outer regions. Also, they did find evidence for the first time for two distinct populations in alpha abundances as a function of metallicity. A 2020 study concluded that collisions between

SECTION 20

#1733086332150

770-433: The Milky Way for some billions of years, and has already orbited it approximately ten times. Its ability to retain some coherence despite such strains would indicate an unusually high concentration of dark matter within that galaxy. In 1999, Johnston et al. concluded that Sgr dSph has orbited the Milky Way for at least one gigayear and that during that time its mass has decreased by a factor of two or three. Its orbit

805-461: The Milky Way's potential field could be improved by proper motion observations of Sgr dSph's stellar debris. This issue is under intense investigation, with computational support by the MilkyWay@Home project. A simulation published in 2011 suggested that the Milky Way may have obtained its spiral structure as a result of repeated collisions with Sgr dSph. In 2018, the Gaia project of

840-606: The Sagittarius Dwarf Spheroidal Galaxy and the Milky Way triggered major episodes of star formation in the latter, based on data taken from the Gaia project. Gaia EDR3 The Gaia catalogues are star catalogues created using the results obtained by Gaia space telescope. The catalogues are released in stages that will contain increasing amounts of information; the early releases also miss some stars, especially fainter stars located in dense star fields. Data from every data release can be accessed at

875-483: The Sgr ;dSph main cluster and its merger with the Milky Way stream is expected to be complete within a billion years from now. At first, many astronomers thought that Sgr dSph had already reached an advanced state of destruction, so that a large part of its original matter was already mixed with that of the Milky Way. However, Sgr dSph still has coherence as a dispersed elongated ellipse, and appears to move in

910-415: The Sgr dSph main cluster is about to pass through the galactic disc of the Milky Way within the next hundred million years, while the extended loop-shaped ellipse is already extended around and through our local space and on through the Milky Way galactic disc, and in the process of slowly being absorbed into the larger galaxy, calculated at 10,000 times the mass of Sgr dSph. The dissipation of

945-549: The data processing procedure links individual Gaia observations with particular sources on the sky, in some cases the association of observations with sources will be different in the second data release. Consequently, DR2 uses different source identification numbers than DR1. A number of issues have been identified with the DR2 data, including small systematic errors in astrometry and significant contamination of radial velocity values in crowded star fields, which may affect some one percent of

980-403: The magnitude range g = 3–20, red and blue photometric data for about 1.1 billion stars and single colour photometry for an additional 400 million stars, and median radial velocities for about 7 million stars between magnitude 4 and 13. It also contains data for over 14,000 selected Solar System objects. The coordinates in DR2 use the second Gaia celestial reference frame ( Gaia –CRF2 ), which

1015-549: The radial velocity values. Ongoing work should resolve these issues in future releases. A guide for researchers using Gaia DR2, which collected "all information, tips and tricks, pitfalls, caveats and recommendations relevant to" DR2, was prepared by the Gaia Helpdesk in December 2019. Due to uncertainties in the data pipeline, the third data release, based on 34 months of observations, has been split into two parts so that data that

1050-465: The south pole is still in the region of the Large Magellanic Cloud and contains 448,478 objects. The GEPC data was needed right at the beginning of the mission for the initial calibration. The commissioning phase of the Gaia space probe ended on July 18, 2014. This was followed by a calibration phase of 28 days, during which the ecliptic poles were measured intensively. During this time, Gaia

1085-600: The title Sagittarius Dwarf Galaxy . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Sagittarius_Dwarf_Galaxy&oldid=992081667 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Sagittarius Dwarf Spheroidal Galaxy Officially discovered in 1994, by Rodrigo Ibata, Mike Irwin , and Gerry Gilmore , Sgr dSph

Sagittarius Dwarf Galaxy - Misplaced Pages Continue

1120-456: Was immediately recognized as being the nearest known neighbor to the Milky Way at the time. (The disputed Canis Major Dwarf Galaxy , discovered in 2003, might be the actual nearest neighbor.) Although it is one of the closest companion galaxies to the Milky Way, the main parent cluster is on the opposite side of the Galactic Center from Earth, and consequently is very faint, although covering

1155-460: Was made, which are in the region of Gaia's magnitude limit. The selected objects are already well observed and documented. In most cases, quasars are very far away, so that their proper motions and parallaxes are negligibly small. Gaia Ecliptic Pole Catalogue (GEPC) was created for measuring the poles. The southern part of the catalogue was compiled from observations made with the MPG/ESO telescope at

1190-616: Was operated in Ecliptic Poles Scan Law mode (EPSL), in which the two poles were measured twice during each revolution. The initial catalogue was used for Gaia DR1 to match Gaia -found objects to previous star catalogues. Gaia DR1, the first data release based on 14 months of observations made through September 2015, took place on 13 September 2016. It includes "positions and magnitudes in a single photometric band for 1.1 billion stars using only Gaia data, positions, parallaxes and proper motions for more than 2 million stars" based on

1225-405: Was ready first, was released first. The first part, EDR3 (Early Data Release 3), consisting of improved positions, parallaxes and proper motions, was released on 3 December 2020. The coordinates in EDR3 use a new version of the Gaia celestial reference frame ( Gaia –CRF3), based on observations of 1,614,173 extragalactic sources, 2,269 of which were common to radio sources in the third revision of

#149850