04 February 2015

Hidden Objects Along Center of Milky Way Detected Through Infrared

The VVV survey (VISTA Variables in the Via Lactea) of the VISTA telescope at ESO’s Paranal Observatory in Chile has allowed astronomers to see the central parts of the Milky Way as never before.

Using infrared light, the VVV imaged the Trifid Nebula and revealed that the gas cloud has been hiding two Cepheid variable stars directly behind it but at a far distance.

The pair of cepheid stars hidden by the Trifid Nebula is estimated to be around 37,000 light years away from Earth while the Trifid Nebula is at 5,200 light years away. Cepheid variables are unstable bright stars that brightens and fades over time, in this case, a period of 11 days.

These two stars are the only two known Cepheid variables that are close to the central plane of the Milky Way which is 27,000 light years away from Earth.

The Vista Variables in the Via Lactea is an astronomical survey to map the Milky Way, it's bulge and the disk area close to the center of the galaxy. The VVV survey previously assisted astronomers in constructing a three dimensional map of the Milky Way

Hidden Objects Revealed By VVV Survey

A new image taken with ESO’s VISTA survey telescope reveals the famous Trifid Nebula in a new and ghostly light. By observing in infrared light, astronomers can see right through the dust-filled central parts of the Milky Way and spot many previously hidden objects. In just this tiny part of one of the VISTA surveys, astronomers have discovered two unknown and very distant Cepheid variable stars that lie almost directly behind the Trifid. They are the first such stars found that lie in the central plane of the Milky Way beyond its central bulge.

As one of its major surveys of the southern sky, the VISTA telescope at ESO’s Paranal Observatory in Chile is mapping the central regions of the Milky Way in infrared light to search for new and hidden objects. This VVV survey (standing for VISTA Variables in the Via Lactea) is also returning to the same parts of the sky again and again to spot objects that vary in brightness as time passes.

A tiny fraction of this huge VVV dataset has been used to create this striking new picture of a famous object, the star formation region Messier 20, usually called the Trifid Nebula, because of the ghostly dark lanes that divide it into three parts when seen through a telescope.

The familiar pictures of the Trifid show it in visible light, where it glows brightly in both the pink emission from ionised hydrogen and the blue haze of scattered light from hot young stars. Huge clouds of light-absorbing dust are also prominent. But the view in the VISTA infrared picture is very different. The nebula is just a ghost of its usual visible-light self. The dust clouds are far less prominent and the bright glow from the hydrogen clouds is barely visible at all. The three-part structure is almost invisible.

Video: Hidden Objects Discovered Behind Trifid Nebula

In the new image, as if to compensate for the fading of the nebula, a spectacular new panorama comes into view. The thick dust clouds in the disc of our galaxy that absorb visible light allow through 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 perfect example of the surprises that can be revealed when imaging in the infrared. Apparently close to the Trifid in the sky, but in reality about seven times more distant [1], a newly discovered pair of variable stars has been found in the VISTA data. These are Cepheid variables, a type of bright star that is unstable and slowly brightens and then fades with time. This pair of stars, which the astronomers think are the brightest members of a cluster of stars, are the only Cepheid variables detected so far that are close to the central plane, but on the far side of the galaxy. They brighten and fade over a period of eleven days.


European Southern Observatory
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