Category Astronomy/Space

N-body simulation of the merger of a Milky Way-like galaxy (with its stars in blue) and a smaller disky galaxy resembling the Small Magellanic Cloud in mass (with it stars in red). At the beginning, the two galaxies are clearly separated, but gravity pulls them together and this leads to the full accretion of the smaller one. Distinguishing the accreted stars from the rest is not easy by the final stage, but it is possible using the motions of the stars and their chemical composition. Credit
Credit: H.H. Koppelman, A. Villalobos, A. Helmi (University of Groningen)

Some ten billion years ago, the Milky Way merged with a large galaxy. The stars from this partner, named Gaia-Enceladus, make up most of the Milky Way’s halo and also shaped its thick disk, giving it its inflated form...

An artist’s illustration of what Phaeton might look like up close.
Credit: Heather Roper

Blue asteroids are rare, and blue comets are almost unheard of. An international team led by Teddy Kareta, a doctoral student at the University of Arizona’s Lunar and Planetary Laboratory, investigated (3200) Phaethon, a bizarre asteroid that sometimes behaves like a comet, and found it even more enigmatic than previously thought.

Kareta presented the results during a press conference on Oct. 23 at the 50th annual meeting of the American Astronomical Society’s Division for Planetary Science in Knoxville, Tennessee. Using telescopes in Hawaii and Arizona, the team studied sunlight reflected off Phaethon, which is known to be blue in color...

IC 63 — nicknamed the Ghost Nebula — is about 550 light-years from Earth. The nebula is classified as both a reflection nebula — as it is reflecting the light of a nearby star — and as an emission nebula — as it releases hydrogen-alpha radiation. Both effects are caused by the gigantic star Gamma Cassiopeiae. The radiation of this star is also slowly causing the nebula to dissipate.
Credit: ESA/Hubble, NASA

About 550 light-years away in the constellation of Cassiopeia lies IC 63, a stunning and slightly eerie nebula. Also known as the ghost of Cassiopeia, IC 63 is being shaped by radiation from a nearby unpredictably variable star, Gamma Cassiopeiae, which is slowly eroding away the ghostly cloud of dust and gas...

An Illustration of a compact, multi-planet system. Researchers have found that such systems are more likely to form around stars with lower amounts of heavy elements than our own Sun.
Credit: Michael S. Helfenbein/Yale University

Researchers at Yale and the Flatiron Institute have discovered that compact, multiple-planet systems are more likely to form around stars that have lower amounts of heavy elements than our own Sun. This runs counter to a good deal of current research, which has focused on stars with higher metallicity.

The research team looked at 700 stars and their surrounding planets for the study, which appears in The Astrophysical Journal Letters. The researchers considered any element heavier than helium – including iron, silicon, magnesium, and carbon – as a heavy metal...