Leo I dwarf galaxy

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Galaxy
Leo I dwarf galaxy
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Leo I in the middle of the picture as a weak milky light spot next to Regulus
Leo I in the middle of the picture as a weak milky light spot next to Regulus
AladinLite
Constellation lion
Position
equinox :  J2000.0 , epoch : J2000.0
Right ascension 10 h 08 m 27.4 s
declination 12 ° 18 ′ 27 ″
Appearance
Morphological type dSph  
Brightness  (visual) (11.2 ± 0.5) mag
Angular expansion (9.8 × 7.4) ′
Physical data
Affiliation Local group  
Redshift 0.000951 +/- 0.000007  
Radial velocity 285 ± 2 km / s  
distance (820,000 ± 70,000) ly /
(250,000 ± 20,000) pc
history
discovery Albert George Wilson
Discovery date 1950
Catalog names
UGC  5470 • PGC  29488 • MCG  + 02-26-027 • DDO 74, A1006, Harrington-Wilson # 1, Regulus dwarf

Leo I is a spheroidal dwarf galaxy in the constellation of Leo . It is about 820,000 light years away from the solar system, with a largest extent of about 7,000 light years. Leo I is a member of the Local Group and is one of the most distant satellites of our Milky Way .

The galaxy was already in 1950 by Albert George Wilson on photo recordings in the screening of the Palomar Observatory Sky Survey using the 48- inch - Schmidt Telescope at Palomar Observatory discovered.

Leo I is just 12  arc minutes from Regulus , the brightest star in the constellation Leo. This is why the dwarf galaxy is sometimes referred to as the Regulus dwarf . The scattered light of the star makes studying the object more difficult and it was only possible to examine it visually in the 1990s.

properties

Dimensions

Measuring the radial velocities of some of the brightest red giant stars in the galaxy allowed the determination of the mass of Leo I .
It is at least (2.0 ± 1.0) × 10 7 M ⊙ . Overall, the dwarf should consist of at least ten million stars. However, the results are not necessarily final, nor do they prove or disprove the existence of a dark matter halo around the galaxy. That Leo I does not rotate, however, could already be shown without a doubt.

Hypothetically , Leo I could also be a stream of tidal debris in the halo of our Milky Way Galaxy.

Star formation

It is typical of a dwarf galaxy that its metallicity is very low. It is only 1 % of that of the sun . Gallart et al. showed through analysis of Hubble Space Telescope images in 1999 that Leo I experienced a massive increase in its star formation rate 6 billion and 2 billion years ago. These two phases account for 70% to 80% of the galaxy's star population. There were no significant indications for stars older than 10 billion years . About 1 billion years ago, star formation appears to have decayed rather abruptly to a negligible rate. This low level of activity lasted until about 200 million to 500 million years ago. This is the youngest of the dwarf galaxies in the Milky Way subgroup. Leo I also appears to be embedded in a cloud of ionized gas, which has a mass on the order of the galaxy.

Globular clusters

There were no globular clusters in dwarf galaxy Leo I discovered.

Web links

Individual evidence

  1. ↑ SIMBAD Astronomical Database . Retrieved November 21, 2011.
  2. ↑ a b c d e f NED
  3. ↑ ID Karachentsev, VE Karachentseva, WK Hutch Meier, DI Makarov: A Catalog of Neighboring Galaxies . In: Astronomical Journal . 127, No. 4, 2004, pp. 2031-2068. bibcode : 2004AJ .... 127.2031K . doi : 10.1086 / 382905 .
  4. ↑ Karachentsev, ID; Kashibadze, OG: Masses of the local group and of the M81 group estimated from distortions in the local velocity field . In: Astrophysics . 49, No. 1, 2006, pp. 3-18. bibcode : 2006Ap ..... 49 .... 3K . doi : 10.1007 / s10511-006-0002-6 .
  5. ↑ a b Leo I . In: SEDS Messier Database . Retrieved May 15, 2006.
  6. ↑ a b c d e f Sidney Van den Bergh: Galaxies of the Local Group , 1st. Edition, Cambridge University Press, 2000, ISBN 0-521-65181-6 , pp. 243-245.
  7. ↑ Stars and Space May 2012 p. 74f
  8. ^ Sidney van den Bergh : Updated Information on the Local Group . In: The Publications of the Astronomical Society of the Pacific . 112, No. 770, April 2000, pp. 529-536. arxiv : astro-ph / 0001040 . bibcode : 2000PASP..112..529V . doi : 10.1086 / 316548 .