Telescope finds possible planetary system forming
EUROPEAN SPACE AGENCY SCIENCE RELEASE
Posted: April 30, 2000
Stars are born within thick 'cocoons' of dust very difficult to penetrate, and for this reason current models describing the process are very incomplete. Astronomers know, in broad terms, that the future star begins to form within the dust cloud by accreting material which forms a disk, the same disk out of which planets, comets and all the components of a planetary system will probably form in the future --the disk is actually called a 'protoplanetary disk'. Once the star-to-be has gathered enough material, the high pressures and temperatures in its centre trigger the first nuclear reactions and the star 'lights up' --it starts the 'ignition'. During this process the very young star or 'protostar' emits jets of material that can be detected with different techniques. Astronomers use these detectable signs to classify the evolutionary stages of the new-born stars.
The system observed by ISO was previously thought to be at the earliest evolutionary stage, in fact, so young that the protostar had not yet had time to ignite. However, ISO results contradict this belief.
"We are seeing the earliest stages of formation of a planetary system. There is already a central object hot enough to work as a star and to heat up its surrounding protoplanetary disk. The star is already 'lit up'", says Spanish astronomer Jose Cernicharo, from the Instituto de Estructura de la Materia (CSIC), in Madrid, main author of the article being published in Science.
The system observed by ISO's infrared camera, ISOCAM, is 1200 light years away in a star-forming region in the Orion nebula. It's called VLA1/2. Cernicharo and his group estimate that the central star and its surrounding matter might be at an average temperature of at least 500 degrees Kelvin. It is surrounded by a protoplanetary disk whose diameter is four times the distance from the Earth to the Sun, the same as Jupiterīs orbit.
"This is the first time we can determine the size of the regions where where a low mass star and its planets are being formed", Cernicharo says.
ISO results also indicate --as highlighted by the team in Science-- that these systems will be observable with the new generation of large (8 metre class) ground-based infrared telescopes. Current knowledge so far suggested that these very dusty objects could only be detected at far-infrared wavelengths not accessible from the ground, but ISO has shown that they can also be seen at certain very precise infrared wavelengths which do indeed cross the Earth's atmosphere --the so-called 'infrared windows' at which ground -based infrared telescope work.
For this work, ISO observations were complemented with the 30 metres radio telescope of the Institute de Radioastronomie Millimetrique (IRAM), in Granada (Spain).
The European Space Agency's infrared space observatory, ISO, operated from November 1995 to May 1998, almost a year longer than expected. An unprecedented observatory for infrared astronomy, able to examine cool and hidden places in the Universe, ISO made nearly 30 000 scientific observations.
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