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Stellar nursery

August 5, 2011

An infrared telescope run by the European Southern Observatory has found 96 star clusters that were previously hidden behind dust and gas. The find gives scientists new information on the early stages of star formation.

A mosaic of 30 of the star clusters the VISTA telescope found
European scientists found 96 new start clustersImage: ESO/J. Borissova

The European Southern Observatory's VISTA telescope has dug deep into the star-forming regions of the Milky Way and found 96 new star clusters that are developing in dusty cosmic nurseries.

The find comes one year into an ESO program called VVV, or VISTA Variables in the Via Lactea, that uses the infrared telescope to survey the galaxy and find objects that are hidden behind this clouds of cosmic gas and dust that visible-light telescopes cannot penetrate. Via Lactea is Latin for Milky Way.

"In regions that looked empty in previous visible-light surveys, the sensitive VISTA infrared detectors uncovered many new objects," said Dante Minniti, lead scientist on the survey, in a statement published Wednesday.

The star clusters give scientists new insight into the formation and evolution of the universe, since these kinds of groupings, called open clusters, are the building blocks of solar systems and galaxies such as our own Milky Way. Their results will be published in a forthcoming edition of the journal Astronomy & Astrophysics.

APEX telescope in Chile
ESO also operates the APEX telescope, located 5,100 meters above sea level in ChileImage: AP

Needs dusting

The problem facing astronomers is the fact that stellar clusters form in very dusty regions of space, which absorb and diffuse most of the visible light that young, developing stars emit, "hiding" them, in effect, behind a curtain of dust and gas.

"We can't see them unless we can create a window in the electromagnetic spectrum," said Axel Quetz, a science editor at the Max Planck Institute of Astronomy in Heidelberg, in an interview with Deutsche Welle.

But by using an infrared telescope, which can sense light at wavelengths three times the length of those detectible by the human eye, scientists can see through that curtain and peer into the window.

To clear the smudges further, the ESO team used computer software that took images captured by the telescope and removed the foreground stars in front of each cluster, which enabled them to count the genuine cluster members. Scientists could then analyze the visual images to measure the distance from the earth and ages of the stars.

Most of the clusters were small, containing about 10 to 20 stars each, and were very faint and compact compared to typical examples of this kind of stellar grouping.

This is the first time so many faint and small clusters have been found at once, ESO said.

Infrared giant

The telescope used, named VISTA for Visible and Infrared Survey Telescope for Astronomy, is the world largest telescope in the world dedicated to surveying outer space. Conceived and developed in the UK, it has a main mirror that measures 4.1 meters across and a three-ton camera that has 16 detectors sensitive to infrared light.

The camera has to be cooled to -200 degrees Celsius (-328 Farenheit) and is sealed with the largest infrared transparent window ever made.

"Infrared radiation is like heat and observing with an infrared telescope with a warm detector is like trying to see stars in daytime," added Richard Hood, ESO information officer, who spoke to Deutsche Welle. "The background is too bright."

The Rho Ophiuchi star formation region
The Rho Ophiuchi star formation region was found using the ESO's APEX telescopeImage: ESO/S. Guisard

The telescope is located on a mountain peak in the Atacama Desert of northern Chile. The site was chosen due to its remoteness, away from polluting ambient light, its high altitude and its aridity, which is important because water vapor in the air can obscure images.

The fact that the air flow across the site is uniform is also helpful to astronomers. While twinkling stars might be romantic to the layperson, to scientists, they are an annoyance.

"It's a bit like if you look above a heater in a room, you see everything churning about," Hood said. "That's what makes stars twinkle and what messes up the image quality from the ground."

A star is born

Despite the problems cosmic dust and gases cause astronomers, they are essential since they are the raw materials that form stars and planets.

These bodies start off as great clouds of hydrogen and other heavier elements such as carbon, oxygen and silicon. At some slightly denser regions in the cloud, particles begin to coalesce under their own gravity and stars begin to form.

Around them, a flat, rotating disk of gas and dust develops, out of which form the planets and other bodies found in a solar system.

The process can take a few million years, which in astronomical terms is not that long, especially when compared to the age of our solar system (4.6 billion years) or when the big bang is thought to have occurred (13.7 billion years ago).

While astronomers have figured out the basic steps of star formation, the processes involved are very complex and many of the details are still not fully understood.

The European Southern Observatory is an intergovernmental astronomy organization headquartered in Germany. Founded in 1962, it is supported by 15 countries. In addition to VISTA and other powerful instruments to study the heavens, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory.

Author: Kyle James
Editor: Cyrus Farivar