“The central bulge of the Milky Way is thought to consist of vast numbers of old stars. But the VISTA data has revealed something new — and very young by astronomical standards!”
Astronomers using the VISTA telescope at ESO’s Paranal Observatory have discovered a previously unknown component of the Milky Way. By mapping out the locations of a class of stars that vary in brightness called Cepheids, a disc of young stars buried behind thick dust clouds in the central bulge has been found.
“All of the 35 classical Cepheids discovered are less than 100 million years old. The youngest Cepheid may even be only around 25 million years old, although we cannot exclude the possible presence of even younger and brighter Cepheids.”
The Vista Variables in the Vía Láctea Survey (VVV)  ESO public survey is using the VISTA telescope at the Paranal Observatory to take multiple images at different times of the central parts of the galaxy at infrared wavelengths . It is discovering huge numbers of new objects, including variable stars, clusters and exploding stars (see related articles).
A team of astronomers, led by Istvan Dékány of the Pontificia Universidad Católica de Chile, has now used data from this survey, taken between 2010 and 2014, to make a remarkable discovery — a previously unknown component of our home galaxy, the Milky Way.
“The central bulge of the Milky Way is thought to consist of vast numbers of old stars. But the VISTA data has revealed something new — and very young by astronomical standards!” says Istvan Dékány, lead author of the new study.
Analysing data from the survey, the astronomers found 655 candidate variable stars of a type called Cepheids. These stars expand and contract periodically, taking anything from a few days to months to complete a cycle and changing significantly in brightness as they do so.
The time taken for a Cepheid to brighten and fade again is longer for those that are brighter and shorter for the dimmer ones. This remarkably precise relationship, which was discovered in 1908 by American astronomer Henrietta Swan Leavitt, makes the study of Cepheids one of the most effective ways to measure the distances to, and map the positions of, distant objects in the Milky Way and beyond.
But there is a catch — Cepheids are not all the same — they come in two main classes, one much younger than the other. Out of their sample of 655 the team identified 35 stars as belonging to a sub-group called classical Cepheids — young bright stars, very different from the usual, much more elderly, residents of the central bulge of the Milky Way. Read the rest of this entry »
One of the biggest mysteries in astronomy, how stars blow up in supernova explosions, is unraveling thanks to new data from NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR. In this image of Cassiopeia A, NuSTAR data, which show high-energy X-rays from radioactive material, are colored blue. Lower-energy X-rays from non-radioactive material are shown in red, yellow and green. Cassiopeia A is the remains of a star that blew up in a supernova event whose light reached Earth about 350 years ago, when it could have appeared to observers as a star that suddenly brightened. The remnant is located 11,000 light-years away from Earth.