March 5, 2015
The view from newborn stars found far above the Milky Way’s plane would have a (heavily obscured) view of the galactic disk.
NASA / JPL-Caltech
Two clusters of stars, still embedded in their natal clouds of dust and gas, are floating 16,000 light-years above the pancake-shaped disk of the Milky Way.
Denilso Camargo (Colegio Militar de Porto Alegre, Brazil) and colleagues reported the surprising find, part of a larger study of embedded star clusters in Wide-field Infrared Survey Explorer (WISE) data, in the February 26th Monthly Notices of the Royal Astronomical Society.
The Milky Way is a paper-thin spiral galaxy, with 85% of its stars in a disk about 100,000 light-years across and only 3,000 light-years tall. A thicker and sparser disk of older stars extends up to 16,000 light-years above the galactic plane. The two disks appear to contain distinct stellar populations — the thick disk likely forged stars at an earlier stage of the Milky Way’s formation.
So the discovery of new stars so far above the galactic plane, firmly in thick disk territory, is unexpected to say the least. No other such high-altitude star clusters have ever been found, even though violent supernova explosions have ejected plenty of molecular hydrogen clouds high above the galaxy’s plane, any of which could potentially form stars given the right trigger.
The star clusters themselves are only about 2 million years old. Their age, distance, and mass come from models that Camargo’s team fit to the color and brightness measurements of their stellar populations.
At an altitude of 16,000 light-years, the 33 and 42 stars belonging to clusters Camargo 438 and Camargo 439, respectively, have an exceptional (if heavily obscured) outsider’s view of the Milky Way’s spiral design. But they won’t for long, astronomically speaking. The authors calculated the velocity of the cloud containing the young and still-forming stars, and they find that the cloud has crossed paths with the disk before, sometime between 45 and 50 million years ago, an event that likely caused the clouds to condense and form stars. The clusters will cross paths with the disk again in another 50 million years or so.
See the full article here.
Please help promote STEM in your local schools.
Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.
Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.
Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.
“Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”