Willman 1

Willman 1 is an Ultra Faint dwarf galaxy may also be a globular cluster. It was named after Beth Willman from Haverford College, the leading author of a study based on data from the Sloan Digital Sky Survey. The galaxy is a satellite of the Milky Way and about 120 kpc away. Willman 1 has an elliptical shape with a half-light radius of about 25 pc and a heliocentric recession velocity of approximately -13 km / s

Properties

Level of 2011 is the Willman 1 zweitlichtschwächste known dwarf galaxy by Segue 1 is only a 10 millionth of the luminosity of the Milky Way. The galaxy has an absolute magnitude of -3 mag. Observations suggest that it has a mass of 400,000 M ⊙. Thus one comes to a mass-luminosity ratio of 800, which implies a dominance of this galaxy by dark matter. It is difficult, however, especially at such faint objects to estimate the total mass of the system, there is always a stable gravitationally bound system is adopted as the basis of calculations, which is not always true in galaxies that are currently exposed to the external influence of tidal forces.

Willman 1 is primarily composed of older stars, which emerged more than 10 billion years ago. The metallicity of these stars is correspondingly low at [Fe / H] ≈ -2.1, which is equivalent to the fact that it contains about 110 times less in heavy elements than our Sun.