By fusing microlensing light data, high-resolution images and
spectroscopy, researchers can finally view a complete picture
of a MACHO (Massive Compact Halo Object) by measuring
its mass, distance and velocity. This demonstrates that
precision brightness measurements and extensive follow-up
will allow astronomers to characterize a significant fraction of
the Milky Way's dark matter. The work is presented in the
Dec. 6 issue of Nature.
The team of scientists used the NASA/ESA Hubble Space
Telescope and the Europeans Southern Observatory's Very
Large Telescope to take images and make spectra of a
MACHO microlens --which turned out to be a red star in the
The observation makes it possible to determine the mass of the
MACHO and its distance from the Earth. In this case, the
MACHO is a small star with a mass between 5 percent and 10
percent of the mass of the sun at a distance of 600 light-years.
This makes the MACHO a dwarf star and a faint member of
the disk population of stars in the Milky Way.
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