A lower limit of 9.5 Gyr on the age of the Galactic disk from the oldest white dwarf stars

Article Abstract:

An age-luminosity relations model of the oldest white dwarf stars reveals that the lower limit for the minimum age of the local Galactic disk is about 9.5 Gyrs. The white-dwarf luminosity function shows that the minimum age is more that the Hubble expansion age estimates. The emerging picture of the Galaxy shows that the halo formed about 14-17 Gyrs ago, the bulge globular clusters formed about 12-14 Gyrs ago, and a modest hiatus preceded star formation about 10 Gyrs ago.

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A high-velocity black hole on a Galactic-halo orbit in the solar neighbourhood

Article Abstract:

It has been possible to identify the transverse motion for the black-hole X-ray nova XTE J1118+480. From this, a large space velocity was obtained. This X-ray binary system seems to be comparable to or greater than the age of the Galactic disk.

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Signs of galactic cannibalism

Article Abstract:

Theories of galaxy formation suggest that galaxies increase in size by engulfing smaller galaxies. Studies of the Andromeda galaxy demonstrate that the distribution of ancient galactic debris may be a tell-tale signature for such events.

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