| Leo I | |
|---|---|
 Leo I appears as a faint patch to the right of the bright star, Regulus. |
|
| Observation data (J2000 epoch) | |
| Constellation | Leo |
| Right ascension | 10h 08m 27.4s[1] |
| Declination | +12° 18′ 27″[1] |
| Redshift | 285 ± 2 km/s[1] |
| Distance | 820 ± 70 kly (250 ± 20 kpc)[2][3] |
| Type | E;dSph[1] |
| Apparent dimensions (V) | 9′.8 × 7′.4[1] |
| Apparent magnitude (V) | 11.2[1] |
| Notable features | Milky Way satellite |
| Other designations | |
| UGC 5470,[1] PGC 29488,[1] DDO 74,[1] A1006,[1] Harrington-Wilson #1,[1] Regulus Dwarf[1] | |
| See also: Galaxy, List of galaxies | |
Leo I is a dwarf spheroidal galaxy in the constellation Leo. At about 820,000 light-years distant, it is a member of the Local Group of galaxies and is thought to be one of the most distant satellites of the Milky Way galaxy. It was discovered in 1950 by Albert George Wilson on photographic plates of the National Geographic Society - Palomar Observatory Sky Survey, which were taken with the 48-inch Schmidt camera at Palomar Observatory.[4][5]
Contents |
Mass [link]
The measurement of radial velocities of some bright red giants in Leo I have made possible to measure its mass. It was found to be at least (2.0 ± 1.0) × 107 MSun. The results are not conclusive, and do not deny or confirm the existence of a large dark matter halo around the galaxy. However, it seems to be certain that the galaxy does not rotate.[5]
It has been suggested that Leo I is a tidal debris stream in the outer halo of the Milky Way. This hypothesis has not been confirmed, however.[5]
Star formation [link]
Typical to a dwarf galaxy, the metallicity of Leo I is very low, only one percent that of the Sun. Gallart et al. (1999) deduce from Hubble Space Telescope observations that the galaxy experienced a major increase (accounting for 70% to 80% of its population) in its star formation rate between 6 Ga and 2 Ga (billion years ago). There is no significant evidence of any stars that are more than 10 Ga old. About 1 Ga ago, star formation in Leo I appears to have dropped suddenly to an almost negligible rate. Some low-level activity may have continued until 200-500 Ma. Therefore it may be the youngest dwarf spheroidal satellite galaxy of the Milky Way. In addition, the galaxy may be embedded in a cloud of ionized gas with a mass similar to that of the whole galaxy.[5][6]
Globular clusters [link]
No globular clusters have been found in the galaxy.[5]
Regulus [link]
Leo I is located only 12 arc minutes from Regulus, the brightest star in the constellation. For that reason, the galaxy is sometimes called the Regulus Dwarf. Scattered light from the star makes studying the galaxy more difficult, and it was not until the 1990s that it was detected visually.[4][5]
References [link]
- ^ a b c d e f g h i j k l "NASA/IPAC Extragalactic Database". Results for Leo I. https://nedwww.ipac.caltech.edu/. Retrieved 2006-11-29.
- ^ I. D. Karachentsev, V. E. Karachentseva, W. K. Hutchmeier, D. I. Makarov (2004). "A Catalog of Neighboring Galaxies". Astronomical Journal 127 (4): 2031–2068. Bibcode 2004AJ....127.2031K. DOI:10.1086/382905.
- ^ Karachentsev, I. D.; Kashibadze, O. G. (2006). "Masses of the local group and of the M81 group estimated from distortions in the local velocity field". Astrophysics 49 (1): 3–18. Bibcode 2006Ap.....49....3K. DOI:10.1007/s10511-006-0002-6.
- ^ a b "Leo I". SEDS Messier Database. https://www.seds.org/messier/xtra/ngc/leo1.html. Retrieved 2006-05-15.
- ^ a b c d e f Van den Bergh, Sidney (2000). Galaxies of the Local Group (1st ed.). Cambridge University Press. pp. 243–245. ISBN 0-521-65181-6.
- ^ van den Bergh, Sidney (April 2000). "Updated Information on the Local Group". The Publications of the Astronomical Society of the Pacific. 1sss 112 (770): 529–536. arXiv:astro-ph/0001040. Bibcode 2000PASP..112..529V. DOI:10.1086/316548
External links [link]
- Leo I (dwarf galaxy) on WikiSky: DSS2, SDSS, GALEX, IRAS, Hydrogen α, X-Ray, Astrophoto, Sky Map, Articles and images
- Astronomy Picture of the Day - Leo I
- SEDS page on Leo I
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https://wn.com/Leo_I_(dwarf_galaxy)
LEO (computer)
The LEO I (Lyons Electronic Office I) was the first computer used for commercial business applications.
The prototype LEO I was modelled closely on the Cambridge EDSAC. Its construction was overseen by Oliver Standingford, Raymond Thompson and David Caminer of J. Lyons and Co.. LEO I ran its first business application in 1951. In 1954 Lyons formed LEO Computers Ltd to market LEO I and its successors LEO II and LEO III to other companies. LEO Computers eventually became part of English Electric Company (EELM) and then International Computers Limited (ICL) and ultimately Fujitsu.
LEO series computers were still in use until 1981.
Origins and initial design
J. Lyons and Co., one of the UK's leading catering and food manufacturing companies in the first half of the 20th century, sent two of its senior managers, Oliver Standingford and Raymond Thompson, to the USA in 1947 to look at new business methods developed during the Second World War. During their visit they met Herman Goldstine, one of the original developers of ENIAC, the first general-purpose electronic computer (although it had no stored program). Standingford and Thompson saw the potential of computers to help solve the problem of administering a major business enterprise. They also learned from Goldstine that, back in the UK, Douglas Hartree and Maurice Wilkes were actually building another such machine, the pioneering EDSAC computer, at the University of Cambridge.
Leo I
Leo I may refer to:
People
Other
See also
M96 Group
Coordinates: 
10h 48m 34.7s, +12° 40′ 15″
The M96 Group (also known as the Leo I Group) is a group of galaxies in the constellation Leo. This group contains between 8 and 24 galaxies, including three Messier objects. The group is one of many groups that lies within the Virgo Supercluster (i.e. the Local Supercluster).
Members
The table below lists galaxies that have been consistently identified as group members in the Nearby Galaxies Catalog, the survey of Fouque et al., the Lyons Groups of Galaxies (LGG) Catalog, and the three group lists created from the Nearby Optical Galaxy sample of Giuricin et al.
Nearby groups
The Leo Triplet, which includes the spiral galaxies M65, M66, and NGC 3628, is located physically near the M96 Group. Some group identification algorithms actually identify the Leo Triplet at part of the M96 Group. The two groups may actually be separate parts of a much larger group.
Gallery
M96 Group also includes the bright galaxies Messier 105 and Messier 95.
