In astronomy, X-rays look at interstellar gas heated to millions of degrees around extreme environments like black holes, neutron stars, and colliding galaxies.
Very Long Baseline Interferometry, or VLBI, links together widely separated radio telescopes to allow astronomers to see the universe in more detail than ever.
Sidereal time measures the rotation of our planet relative to the stars. It allows astronomers to keep time without worrying about the motion of Earth around the sun.
The Venus transit appeared as a small dark dot crossing sun's face for last time this century on June 5-6, 2012. Last transit of Venus in our lifetimes!