Thursday, August 26, 2010
MESSENGER took a photograph of the Earth and Moon system the other day from a distance of 183 million km, which from that distance looks like this:
Now, the Moon has a diameter of 3500 km while the asteroid 4 Vesta is 530 km, giving them an approximate visible area of:
220618 km2 for 4 Vesta,
9478715 km2 for the Moon
thus 42 times greater. 4 Vesta has a much higher albedo than the Moon though, at 0.423 vs. 0.136. This is one of the optical illusions (or brain failures as Dr. deGrasse Tyson calls them) that the Moon presents us with as it appears to be quite light when compared with the rest of the sky. So it's very likely that we should begin to see some interesting images of the asteroid (though certainly nothing yet comparable to those taken from the Hubble Space Telescope) if there are plans to photograph it in the upcoming months as Dawn continues its slow and steady approach.