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The Sagittarius Dwarf Spheroidal Galaxy (Sgr dSph), also known as the Sagittarius Dwarf Elliptical Galaxy, is an elliptical loop-shaped satellite galaxy of the Milky Way. It contains four globular clusters, with the brightest of them – NGC 6715 (M54) – being known well before the discovery of the galaxy itself 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 at a distance of about 50,000 light-years from the core of the Milky Way. In its looping, spiraling path, it has passed through the plane of the Milky Way several times in the past. In 2018 the Gaia project of the European Space Agency 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 moved past the Milky Way between 300 and 900 million years ago.
The Sloan Digital Sky Survey or SDSS is a major multi-spectral imaging and spectroscopic redshift survey using a dedicated 2.5-m wide-angle optical telescope at Apache Point Observatory in New Mexico, United States. The project was named after the Alfred P. Sloan Foundation, which contributed significant funding.
Messier 54 is a globular cluster in the constellation Sagittarius. It was discovered by Charles Messier in 1778 and subsequently included in his catalog of comet-like objects.
The Canis Major Overdensity or Canis Major Dwarf Galaxy is a disputed dwarf irregular galaxy in the Local Group, located in the same part of the sky as the constellation Canis Major.
The Sagittarius Dwarf Irregular Galaxy (SagDIG) is a dwarf galaxy in the constellation of Sagittarius. It lies about 3.4 million light-years away. It was discovered by Cesarsky et al. on a photographic plate taken for the ESO (B) Atlas on 13 June 1977 using the ESO 1 meter Schmidt telescope.
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 via lactea, from the Greek γαλαξίας κύκλος. 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. 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 has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.
The Virgo Stellar Stream, also known as Virgo Overdensity, is the proposed name for a stellar stream in the constellation of Virgo which was discovered in 2005. The stream is thought to be the remains of a dwarf spheroidal galaxy that is in the process of merging with the Milky Way. It is the largest galaxy visible from the Earth, in terms of the area of the night sky covered.
Canes Venatici I or CVn I is a dwarf spheroidal galaxy situated in the Canes Venatici constellation and discovered in 2006 in the data obtained by Sloan Digital Sky Survey. It is one of the most distant known satellites of the Milky Way as of 2011 together with Leo I and Leo II. The galaxy is located at a distance of about 220 kpc from the Sun and is moving away from the Sun at a velocity of about 31 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical shape with the half-light radius of about 550 pc.
Segue 1 is a dwarf spheroidal galaxy or globular cluster situated in the Leo constellation and discovered in 2006 by Sloan Digital Sky Survey. It is located at a distance of about 23 kpc from the Sun and moves away from the Sun with the velocity of about 206 km/s. Segue 1 has a noticeably elongated shape with the half-light radius of about 30 pc. This elongation may be caused by the tidal forces acting from the Milky Way galaxy if Segue 1 is being tidally disrupted now.
MilkyWay@home is a volunteer distributed computing project in astrophysics running on the Berkeley Open Infrastructure for Network Computing (BOINC) platform. Using spare computing power from over 38,000 computers run by over 27,000 active volunteers as of November 2011, the MilkyWay@home project aims to generate accurate three-dimensional dynamic models of stellar streams in the immediate vicinity of the Milky Way. With SETI@home and Einstein@home, it is the third computing project of this type that has the investigation of phenomena in interstellar space as its primary purpose. Its secondary objective is to develop and optimize algorithms for distributed computing.
Canes Venatici II or CVn II is a dwarf spheroidal galaxy situated in the Canes Venatici constellation and discovered in 2006 in the data obtained by Sloan Digital Sky Survey. The galaxy is located at the distance of about 150 kpc from the Sun and moves towards the Sun with the velocity of about 130 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical shape with the half-light radius of about 74+14
−10 pc.
Coma Berenices or Com is a dwarf spheroidal galaxy situated in the Coma Berenices constellation and discovered in 2006 in data obtained by the Sloan Digital Sky Survey. The galaxy is located at the distance of about 44 kpc from the Sun and moves away from the Sun with the velocity of about 98 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an elliptical shape with the half-light radius of about 70 pc.
Bootes II or Boo II is a dwarf spheroidal galaxy situated in the Bootes constellation and discovered in 2007 in the data obtained by Sloan Digital Sky Survey. The galaxy is located at the distance of about 42 kpc from the Sun and moves towards the Sun with the speed of 120 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately round shape with the half-light radius of about 51 pc.
Segue 2 is a dwarf spheroidal galaxy situated in the constellation Aries and discovered in 2009 in the data obtained by Sloan Digital Sky Survey. The galaxy is located at the distance of about 35 kiloparsecs from the Sun and moves towards the Sun at a speed of 40 km/s. It is classified as a dwarf spheroidal galaxy (dSph) meaning that it has an approximately round shape with a half-light radius of about 34 parsecs.
Pisces I or Pisces Overdensity is a clump of stars in the Milky Way's halo, which may be a disrupted dwarf spheroidal galaxy. It is situated in the Pisces constellation and was discovered in 2009 by analysis of distribution of RR Lyrae stars in the data obtained by the Sloan Digital Sky Survey's data. The galaxy is located at the distance of about 80 kpc from the Sun and moves towards it with a speed of about 75 km/s.
In astronomy, the Sagittarius Stream is a long, complex, structure made of stars that wrap around the Milky Way galaxy in an almost polar orbit. 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.
The stellar halo of a galaxy refers to the component of its galactic halo containing stars. The halo extends far outside a galaxy's brightest regions and typically contains its oldest and most metal poor stars.
The Gaia Sausage is the remains of a dwarf galaxy, the Sausage Galaxy, or Gaia-Enceladus-Sausage, or Gaia-Enceladus, that merged with the Milky Way about 8–11 billion years ago. At least eight globular clusters were added to the Milky Way along with 50 billion solar masses of stars, gas and dark matter.
References
- ↑ SDSS, "Multiple galaxy mergers continue in the Milky Way", 2006 May 8 (accessed 2009 March 29)
- ↑ SpaceDaily, "Milky Way A Field Of Streams", 2006 May 9 (accessed 2009 March 29)
- ↑ SDSS, "Map of stars in the outer regions of the Milky Way Galaxy", V. Belokurov, Sloan Digital Sky Survey (accessed 2009 March 29) Archived March 19, 2009, at the Wayback Machine
Sources
- The Astrophysical Journal, Volume 658, Issue 1, pp. 337–344. "An Orphan in the Field of Streams"; 2007 March; Belokurov, V. et al.; doi : 10.1086/511302; Bibcode : 2007ApJ...658..337B;
- The Astrophysical Journal, Volume 642, Issue 2, pp. L137-L140. "The Field of Streams: Sagittarius and Its Siblings"; 2006 May; Belokurov, V. et al.; doi : 10.1086/504797; Bibcode : 2006ApJ...642L.137B;
- Monthly Notices of the Royal Astronomical Society , Volume 375 Issue 4, pp. 1171–1179. "Is Ursa Major II the progenitor of the Orphan Stream?"; M. Fellhauer et al.; doi : 10.1111/j.1365-2966.2006.11404.x;
- Science News, "Galactic de Gustibus: Milky Way's snacks shed light on dark matter and galaxy growth", Ron Cowen, 2006 July 1
- Christian Science Monitor, "Big galaxies, it seems, eat little ones", Robert C. Cowen, 2006 May 18 (accessed 2009 March 29)
- New Scientist, "Our galaxy's halo is round not squashed", Maggie McKee, 2006 May 9 (accessed 2009 March 29)
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