Hubble Telescope Discovers Planet Forming, Supporting a Theory of Planetary Formation


Photo of AB Aurigae b from NASA

Jakub L., Reporter

    NASA’s Hubble Space Telescope has photographed a planet nine times the size of Jupiter, AB Aurigae b, forming. Both Hubble’s Space Telescope Imaging Spectrograph (STIS) and its Near Infrared Camera and Multi-Object Spectrograph (NICMOS) helped detect the planet. The telescope collected information on the planet for 13 years which suggests that the planet may have formed via disk instability, a theory of planetary formation. 

    Every planet’s formation involves a protoplanetary disk, consisting of gas and dust, surrounding a star. Two main models exist theorizing how this disk leads to planetary formation. 

    Prior to this discovery, the primary model for planetary formation was core accretion. In the core accretion model, small chunks of gas and dust within a protoplanetary disk combine to form a larger object. Then, this object’s gravity continues to attract more gas and dust. As the object absorbs matter from the protoplanetary disk, it grows in size. Eventually, it absorbs a significant amount of matter and becomes a planet. However, core accretion fails to explain the formation of planets a great distance from their sun as core accretion can only occur close to a star. 

    AB Aurigae b supports the theory of disk instability. In this model, a protoplanetary disk swiftly cools. Because of this rapid decrease in temperature, the disk loses gravitation stability and cannot retain its structure. Instead, the disk breaks up into several planets. However, some researchers suggest that a protoplanetary disk would dissolve due to temperature reduction before achieving instability. 

    AB Aurigae b orbits the star AB Aurigae which researchers estimate to be two million years old, the age of Earth’s sun when planets began to form around it. A protoplanetary disk containing AB Aurigae b surrounds this star. The planet orbits its sun at a distance of 8.6 billion miles, more than twice the distance between Pluto and its Sun. At this distance, a planet likely would never form through core accretion and core accretion would likely last longer than two million years if it occurred. Therefore, researchers believe disk instability caused this planet’s formation.