Today Venus will pass between Earth and the sun, appearing as a small black dot moving across the sun's face. The transit of Venus is a rare event, and this afternoon will likely be your last chance to experience it—the next one won't happen until 2117.

Sunday evening's solar eclipse dazzled hundreds of sun gazers who gathered on Caltech's campus to watch the rare alignment, a partial annular "ring of fire" solar eclipse that wowed spectators around the world.

A team of astronomers has found that the most active galactic nuclei—enormous black holes that are violently devouring gas and dust at the centers of galaxies—may prevent new stars from forming. The team, which includes several researchers from Caltech, reported its findings in the May 10 issue of the journal Nature.

Scientists have further narrowed the search for a hypothetical particle that could be dark matter, the mysterious stuff that makes up 80 percent of all the mass in the universe. Caltech postdoc Jennifer Siegal-Gaskins presented the researchers' results, compiled from two years' worth of data from NASA's Fermi Gamma-ray Space Telescope, at a meeting of the American Physical Society in Atlanta earlier this week.