Ursa Major I Dwarf

Infobox Galaxy


name = Ursa Major I Dwarf
epoch = J2000
type = dSph
ra = RA|10|34|52.8cite web
title=NASA/IPAC Extragalactic Database
work=Results for Ursa Major dSph
url=http://nedwww.ipac.caltech.edu/
accessdate=2006-11-27 ]
dec = DEC|+51|55|12
dist_ly = 330 kly (100 kpc)Willman, Dalcanton, Martinez-Delgado, et al. (2005) "A New Milky Way Dwarf Galaxy in Ursa Major", submitted to Astrophysical Journal Letters, on arXiv.org: [http://arxiv.org/abs/astro-ph/0503552 astro-ph/0503552] ]
z =
appmag_v =
size_v =
constellation name = Ursa Major
notes =
names = UMa I dwarf, Ursa Major I dSph

Ursa Major I Dwarf (UMa I dSph) is a dwarf spheroidal galaxy orbiting the Milky Way galaxy. The discovery by Beth Willman et al. was announced in 2005.

Being a small dwarf galaxy, it measures only a few thousand light-years in diameter. As of 2006, it is the second least luminous galaxy known (discounting dark galaxies such as VIRGOHI21 in the Virgo cluster of galaxies), to the Boötes Dwarf (absolute magnitude -5.7). The absolute magnitude of the galaxy is estimated to be only -6.75, meaning that it is less luminous than some stars, like Deneb in the Milky Way. It is comparable in luminosity to Rigel. It has been described as similar to the Sextans Dwarf Galaxy. Both galaxies are ancient and metal-deficient.

It estimated to be located at a distance of about 330,000 light-years (100 Kpc) from the Earth. That is about twice the distance to the Large Magellanic Cloud; the largest and most luminous satellite galaxy of the Milky Way.

There was another object called "Ursa Major Dwarf", discovered by Edwin Hubble in 1949.cite web | title=Ursa Major Dwarf, Palomar 4 | work=Milky Way Globular Clusters | url=http://www.seds.org/~spider/spider/MWGC/pal04.html | accessmonthday=April 16 | accessyear=2005] It was designated as Palomar 4. Due to its peculiar look, it was temporary suspected to be either a dwarf spheroidal or elliptical galaxy. However, it has since been found to be a very distant (about 360,000 ly) globular cluster belonging to our galaxy.

External links

* [http://simbad.u-strasbg.fr/sim-id.pl?protocol=html&Ident=Ursa+Major+Dwarf SIMBAD Ursa Major Dwarf]

ee also

* Ursa Minor Dwarf
* Ursa Major II Dwarf

References