Physics Today: At a symposium and press conference held at the European Space Agency’s ESTEC space research and technology center, in Noordwijk in the Netherlands today, the first scientific results from ESA’s Herschel infrared space observatory were revealed, challenging old ideas of star birth and opening new roads for future research. Herschel is the largest astronomical telescope ever to be placed into space. The diameter of its main mirror is four times larger than any previous IR space telescope and one and a half times larger than Hubble Space Telescope.The images show thousands of distant galaxies furiously building stars and star-forming clouds draped across the Milky Way. As stars begin to form, the surrounding dust and gas is warmed up to a few tens of degrees above absolute zero and starts to emit at far-IR wavelengths. As Earth’s atmosphere blocks IR radiation, only a space-based telescope can observe it.
Herschel‘s observation (above image) of a cloud of gas and dust, called “RCW120,” has revealed an embryonic star that looks set to turn into one of the biggest and brightest stars in our galaxy within the next few hundred thousand years. The very young star already weighs in at around ten times the mass of the Sun, and can continue to grow by feeding on the surrounding cloud, which still contains about 200 times as much material as the star. In the image, the blue cavity is a bubble being blown in the cloud by a massive star in the center. The massive young star currently forming is seen as a white blob on the bottom edge of the bubble.Current theories suggest that the fierce light emitted by such large stars should blast away their birth clouds before they grow any larger than around ten times the mass of the Sun. Despite this, many of these “impossible” stars are already known, some up to 150 times the mass of the Sun. “The fact that stars like this exist at all is one of the biggest mysteries in astronomy, and this star is probably going to be huge,” said Derek Ward-Thompson of Cardiff University. “Now that we’ve seen such a young example, we can start to investigate why our theories can’t explain its existence.” Surveying the Milky WayOne new image shows a part of the plane of our galaxy in the constellation of Vulpecula, as seen at IR wavelengths by the Herschel space telescope. It is just one small part of a project, called “HiGal,” to survey the entire inner part of the plane of the Milky Way, conducting a complete census of the on-going star formation in our galaxy. Herschel can see through the clouds of gas and dust that surround newly formed stars, and observe the hidden processes of their formation in unprecedented detail. The preliminary results based on these first images already show us how stars are formed inside filaments of glowing gas and dust, draped across the galaxy, forming chains of stellar nurseries, tens of light-years long.Toby Moore, of Liverpool John Moores University, said “the complete results from the HiGal survey will revolutionize our understanding of the physical process of star formation. It will give us the first clear picture of the development of clouds of gas and dust clouds into the familiar bright stars of the night sky.” The big pictureHerschel has also been measuring the IR light from thousands of other galaxies, spread across billions of light-years. Each galaxy appears as just a pinprick but its brightness allows astronomers to determine how quickly it is forming stars. Roughly speaking, the brighter the galaxy the more stars it is forming.Until now, astronomers believed that galaxies have been forming stars at about the same rate for the last three billion years. Herschel shows this is not true, finding that galaxies have been changing over cosmic time much faster than previously thought. Water in spaceHerschel has made a discovery of water but in a state that doesn’t occur naturally on Earth.Instead of a solid, liquid, or gaseous state, this new form of water doesn’t occur naturally on Earth. Water vapor is known to exist in stellar nurseries, but in the case discovered by Herschel the intense ultraviolet light from hot young stars has caused it to become electrically charged. “This is a surprise,” says Arnold Benz, ETH Zürich, Switzerland. “It tells us that there are violent processes taking place during the early birth stages which lead to intense radiation throughout the cloud."Paul Guinnessy
