Free Astronomy Magazine March-April 2015

SPACE CHRONICLES T his extract from the VISTA VVV survey of the central parts of the Milky Way shows the famous Trifid Nebula at the bottom. It appears as faint and ghostly at these infrared wavelengths when compared to the familiar view at visible wavelengths. This transparency has brought its own benefits — many previously hidden background objects can now be seen clearly. Among these are two newly discovered Cepheid variable stars, the first ever spotted on the far side of the galaxy near its central plane. [ESO/VVV consortium/D. Minniti] newly discovered Cepheids are at a distance of about 37000 light- years), a newly discovered pair of variable stars has been found in the VISTA data. These are Cepheid var- iables, a type of bright star that is unstable and slowly brightens and then fades with time. This pair of stars, which the astron- omers think are the brightest members of a cluster of stars, are the only Cepheid var- iables detected so far that are close to the central plane, but on the far side of the gal- axy. They brighten and fade over a period of eleven days. can be revealed when imaging in the infrared. Apparently close to the Trifid in the sky, but in reality about seven times more distant (The Trifid Nebula lies about 5200 light-years from Earth, the centre of the Milky Way is about 27000 light-years away, in almost the same direction, and the most of the infrared light that VISTA can see. Rather than the view being blocked, VISTA can see far beyond the Trifid and detect objects on the other side of the galaxy that have never been seen before. By chance this picture shows a per- fect example of the surprises that T his video sequence compares a new view of the Trifid Nebula in infrared light, from the VVV VISTA survey with a more familiar visible-light view from a small telescope. The glowing clouds of gas and dust are much less prominent in the infrared view, but many more stars behind the nebula become appar- ent, including two newly discovered Cepheid variable stars. [ESO/VVV con- sortium/D. Minniti/Gábor Tóth] n