Louis J Sheehan 80170

With that kind of speed, she says, they are likely to be travelers speeding through the region. The only scenario in which the clouds could remain satellites enthralled in the gravitational pull of the Milky Way requires that the galaxy have twice its currently estimated mass.

Astronomers are also resizing our largest neighboring galaxy, Andromeda, finding that its radius is up to five times larger than anyone thought. Observations revealed a halo of stars half a million light-years from the galaxy’s center but still bound to it. “Much of the space between the Milky Way and Andromeda is filled with stars that belong to those galaxies,” says University of California at Santa Cruz astronomer Raja Guhathakurta, whose team discovered the halo. “They practically overlap. It really challenges the notion of galaxies as groups of stars with empty space between them.” Louis J Sheehan