Category Astronomy/Space

Our home Milky Way galaxy (MW, yellow) and our companion Andromeda galaxy (M31, red) are participating in a downward flow away from a vast underdense region called the Local Void and toward the Virgo Cluster, represented by the purple spherecircle. Most galaxies between us and the Virgo Cluster will eventually fall into the cluster but we lie slightly beyond the capture zone. Credit: R. Brent Tully

Researchers have constructed the galaxies’ motions from 13 billion years in the past to the present day. A team of astronomers from Maryland, Hawaii, Israel and France has produced the most detailed map ever of the orbits of galaxies in our extended local neighborhood, showing the past motions of almost 1,400 galaxies within 100 million light years of the Milky Way.

The main gravitational attrac...

Display of the survival of meteoroid with air permeability κ/κ0 = 0.25, until its breakup at an altitude of 32 km.

Our atmosphere is a better shield from meteoroids than researchers thought. When a meteor comes hurtling toward Earth, the high-pressure air in front of it seeps into its pores and cracks, pushing the body of the meteor apart and causing it to explode. “There’s a big gradient between high-pressure air in front of the meteor and the vacuum of air behind it,” said Jay Melosh, a professor of Earth, Atmospheric and Planetary Sciences at Purdue University and co-author of the paper. “If the air can move through the passages in the meteorite, it can easily get inside and blow off pieces.”

Researchers knew that meteoroids often blew up before they reach Earth’s surface, but they di...

Left: Charged particles from the sun (the solar wind) form an induced magnetosphere round Mars, which unlike the sun does not have its own intrinsic magnetic field (artwork: Anastasia Grigoryeva) Larger file Right: Robin Ramstad points out the position of the Swedish instrument ASPERA-3 on a model of the Mars Express spacecraft (photo: Anastasia Grigoryeva)

Despite the absence of a global Earth-like magnetic dipole, the Martian atmosphere is well protected from the effects of the solar wind on ion escape from the planet. New research shows this using measurements from the Swedish particle instrument ASPERA-3 on the Mars Express spacecraft. Present-day Mars is a cold and dry planet with less than 1% of Earth’s atmospheric pressure at the surface...

The Aurora Australis, or Southern Lights, over the South Pole Telescope at NSF’s Amundsen-Scott South Pole Station. Credit: Dr. Keith Vanderlinde, NSF

Observations of two galaxies made with ALMA radio telescope suggest that large galaxies formed faster than scientists had previously thought. The two galaxies, first discovered by the South Pole Telescope at NSF’s Amundsen-Scott South Pole Station in Antarctica, were massive and star-filled at a time when the cosmos was < 1B years old. The observation came as a surprise, considering astronomers had thought that the first galaxies, which formed just a few hundred million years after the Big Bang, were similar to today’s dwarf galaxies – collections of stars much smaller than the Milky Way...