Atom & Cosmos

Earth’s Trojan asteroid
Trojan asteroids may sound like nefarious characters — sneaky buggers ready to unleash a barrage of meteorites — but they’re not much more than orbital tagalongs. Scientists report in the July 28 Nature that Earth has one of these rocky buddies sharing its orbit, as do Mars, Jupiter and Neptune. Astronomers in Canada and the United States found the 300-meter asteroid, called 2010 TK7, in data from the Wide-Field Infrared Survey Explorer telescope and confirmed its presence with scopes on the ground. Trojans are tricky to detect because they typically dwell in the daylight sky, but they could make good candidates for an asteroid rendezvous. —Nadia Drake

Too few black holes
Small black holes may eschew the innermost area around a gargantuan black hole after two galaxies merge. The result, reported online July 21 on arXiv.org by Alessia Gualandris of the Max Planck Institute for Astrophysics and David Merritt of the Rochester Institute of Technology, comes from computer simulations of how stuff reorganizes in galaxies’ cores after a collision. Both galaxies started with a big central black hole, which coalesced into one bigger hole. But after everything started settling down, the number of smaller black holes that stuck near the newly formed beast was only 1 percent to 10 percent what was expected. The astronomers suggest that real galaxies could therefore have populations of black holes with “very uncertain” locations. —Camille M. Carlisle

Galactic watering hole
Astronomers have detected the oldest and largest water reservoir in the universe. The water, holed up in a cloud surrounding a gigantic black hole, sits in a galaxy that blazed brightly about 1.6 billion years after the Big Bang. Water runs rampant in the cosmos, but this oasis holds water equal to the mass of at least 100,000 suns, a fount about 4,000 times the Milky Way’s stash. The results, reported by two international teams in two papers to appear in Astrophysical Journal Letters, suggest a disk of vapor nearly 2,000 light-years wide surrounds the galaxy’s central black hole. —Camille M. Carlisle