ISO finds the 'missing ingredient' to make Jupiter-like planets Astronomers have detected so far about 50 planets orbiting other stars. They are all giant, Jupiter-like planets, made mostly of gas, and their formation process is still unclear. ESA's Infrared Space Observatory, ISO, sheds now some light on this problem. These models will now have to be reviewed. They said, for instance, that Jupiter-like planets had to form in just a few million years, but the ISO result implies that the process can take up to 20 million years.
Planetary systems form very early in the star's life, actually during the star-birth itself.
In the first steps of star formation, when the star is merely a swirling sphere of gas, a thick circumstellar disk of gas and dust forms around the star's equator, and planets form from the material in that disk - called 'protoplanetary disk'. While the whole process of star and planet formation is taking place the system remains covered by opaque dust and therefore optical telescopes cannot see it. When, after the dispersion of the dust, the star becomes visible, much of the material in its protoplanetary disk is already 'locked' in the planets, and only left-over dust grains remain in the now very thin, feeble, circumstellar ring of debris. The gas, a key component of giant, Jupiter-like planets, is all gone already. Or so it seemed.