Astronomers like to find rotating primordial discs of gas and dust around young stars from which planets can form. They might be able to catch the star partway through the planet-formation process, but it’s highly unusual to find such discs around brown dwarfs or stars with very low masses. Now, recent work reveals four new low-mass objects surrounded by discs.
A four-planet system orbiting the star Kepler-223 in the constellation Cygnus is actually a rarity: Its planets, all miniature Neptunes nestled close to the star, are orbiting in a unique resonance that has been locked in for billions of years. For every three orbits of the outermost planet, the second orbits four times, the third six times and the innermost eight times.
To better understand how planets in binary star systems form and evolve, astronomers using the Atacama Large Millimetre/submillimetre Array (ALMA) took a new, detailed look at the planet-forming disc around HD 142527, a binary star about 450 light-years from Earth in a cluster of young stars known as the Scorpius-Centaurus Association.