Some of the invisible matter in our Galactic halo has been shown to be white dwarfs by:
A)direct detection with optical telescopes, such as the Hubble Space Telescope.
B)direct detection with gamma-ray observations from the Fermi Telescope.
C)observations of Type I supernovae.
D)the gravitational microlensing technique.
E)watching white dwarfs in the Galactic halo pass in front of distant galaxies.

Question

Quizplus · Accepted Answer

The gravitational microlensing technique involves observing the temporary brightening of a distant star caused by the gravitational lensing effect of a massive object, such as a white dwarf, passing in front of it. This method has been used to detect some of the invisible matter in our Galactic halo as white dwarfs. The gravitational microlensing technique involves observing the gravitational lensing effect of a massive object (in this case, a white dwarf) on the light of a more distant object (such as a background star). This can reveal the presence and properties of the white dwarf, even though it is too faint to detect through direct observations.

Some of the Invisible Matter in Our Galactic Halo Has