Elderly Parents for Newborn Planets?
Astronomers have discovered a disk of dust that is likely to form new planets. That in itself would not be unusual. But this disc surrounds a very old binary star system. Until now, it has been assumed that planets always form around young stars. According to the usual idea of how planets form, a huge cloud of dust and gas collapses. This creates a new star surrounded by a disk of matter. This is rich in dust particles of iron, silicon, oxygen and other elements found on the planets in our solar system. The satellites of the young star are then created from the material. But a team of Dutch and Belgian astronomers, using the European Space Agency's Infrared Space Observatory, has found such a disk of dust in a completely unusual location (Nature, March 26, 2019). February 1998).
When the researchers aimed the instrument at the "Red Rectangle" cloud of gas and dust 1000 light-years away, they discovered dust grains around 10 micrometers in diameter, from which planets could later form. Analysis revealed tiny crystals of olivine, a mineral found widely on Earth and containing the elements magnesium, iron, silicon and oxygen. This result came as a surprise to astronomers because the "Red Rectangle" is not near a young star, but consists of gas and dust ejected from a pair of older stars.
One of the stars is a red giant, which has a relatively cool surface. Atoms and molecules that have formed in the outer layers can gather on it to form dust particles, explains Rens Waters from the University of Amsterdam. Once the particles have disappeared into the nebula, he says, "the way we imagine them, they combine to form larger and larger particles." Eventually, this process could even produce planets - in a way that has been completely unknown until now.