Space Telescope reveals secrets of the star birth

Herschel observes star-forming cloud RCW 120

Constellation cloud RCW 120 © ESA / PACS / SPIRE / HOBYS Consorti
Read out

The first scientific findings from the ESA's Infrared Space Observatory, Herschel, reveal hitherto hidden details of star formation. New images show thousands of distant galaxies bursting with impulsive star births and glorious star-forming clouds of dust stretching across the Milky Way galaxy. On a recording even an "impossible" star can be seen during its development.

The results presented yesterday at a scientific conference in the European Space Agency (ESA) challenge earlier assumptions about star birth and pave the way for future research.

Herschel is the largest astronomical telescope ever launched into space. The diameter of its main mirror measures four times more than any previous infrared space telescope and one and a half times more than Hubble's.

Massive stars live only briefly

Through Herschel's observations of the star-forming cloud RCW 120, scientists were able to discover an embryonic star, which would evolve into one of the largest and brightest stars in our galaxy in hundreds of thousands of years. He already possesses eight to ten times the mass of the sun and is still surrounded by a cloud of gas and dust reaching 2, 000 solar masses, from which he can further accrete matter.

"This star can only grow bigger, " says Annie Zavagno from the Astrophysics Laboratory in Marseille. Massive stars are rare and short-lived. Capturing one during its creation is a unique opportunity to clarify a long-standing paradox in astronomy. "According to our current knowledge, it is actually not possible that forms a star that is greater than eight solar masses, " said Zavagno. display

"Impossible" stars

The reason for this is that the huge rays of light emitted by such huge stars should dissolve their cloud of origin even before more mass accumulates. But they somehow still form. Many of these "impossible" stars are already known, some of them make up to 150 solar masses. Now that Herschel has observed a star at the beginning of its existence, astronomers can use the data obtained to investigate how it contradicts their theories.

At the beginning of a star birth, the surrounding dust and gas clouds are heated to a few dozen degrees above absolute zero and begin to emit radiation in the far-infrared wavelength range. The Earth's atmosphere completely blocks most of these wavelengths, so observations from space are necessary. With her unprecedented resolution and sensitivity, Herschel captures the star-forming regions of our galaxy.

Star birth in the Milky Way ESA / Hi-GAL Consortium

Stellar nurseries

"Prior to Herschel, it was not clear how matter in the Milky Way collided in sufficiently high density and at the required low temperatures to form stars, " explains Sergio Molinari of the Institute for space physics in Rome. A new picture of Herschel, published yesterday, showing a number of stellar nurseries in the Milky Way, explains this to us. Star embryos appear at first inside the filaments of glowing dust and gas that traverse the entire galaxy. The filaments form chains of nurseries that are dozens of light-years long, shedding the galaxy into a network of star-bursting breeds.

Herschel also took a close look at outer space beyond our galaxy and measured the infrared light of thousands of galaxies billions of light years away in the universe. Each galaxy appears to be as small as a speck of dust, according to the researchers; however, astronomers can determine their star birth rate by their brightness. As a rule, the brighter the galaxy, the more stars it produces.

In this case too, previous knowledge was called into question by Herschel's finding that galaxies developed much faster than originally assumed along the cosmic timescale. Astronomers thought galaxies had formed stars at roughly the same speed over the past three billion years. Herschel refutes this, however.

Star birth in the constellation Fuchs ESA / Hi-GAL Consortium

New state of water discovered

In the past, there were numerous galaxies where true star bursts took place and the stars were born 10 to 15 times faster than today in the Milky Way. What triggered this frenetic activity is not yet clear. "Hierschel will now give us the opportunity to examine the reasons for these developments, " says Steve Eales of the University of Cardiff in the United Kingdom.

In addition, Herschel is a first-class instrument for detecting the smallest forms of matter, the molecules. The telescope has discovered for the first time in space a new state of water. It is electrically charged and unlike the more familiar forms, such as solid ice, liquid water and gaseous vapor, does not naturally exist on earth.

However, when ultraviolet light penetrates through the gas in the birth clouds surrounding the young stars, this radiation can expel an electron from the water molecule and provide it with an electrical charge. "This discovery of ionized water vapor was a surprise, " says Arnold Benz of the Swiss Federal Institute of Technology (ETH) Zurich. "It shows us that in the early stages of the birth, tremendous processes are taking place that lead to an energetic radiation spread throughout the cloud."

Success guarantor Herschel

From the largest galaxies to the smallest molecules, Herschel's many initial findings will be presented to scientists at the ESLAB 2010 Symposium, which will take place this week at ESA's Space Research and Technology Center, ESTEC, in Noordwijk, The Netherlands.

"This is just the beginning of the mission. Thanks to Herschel, we will gain many more scientific findings in the coming years, "assures Göran Pilbratt, Herschel project scientist at ESA.

(ESA, 07.05.2010 - DLO)