AB Aurigae

Mary Doris Applegate Beach discovered that AB Aurigae is a variable star by examining 150 photographic plates taken between 1914 and 1921. Her discovery was announced in 1921.

This star is known for hosting a dust disk that harbour a massive protoplanet or proto-brown dwarf. The star is part of the young Taurus-Auriga association, which is located in the Taurus Molecular Cloud. It may recently have encountered a dense cloudlet, which disrupted its debris disk and produced an additional reflection nebula.

Substellar companion

In 2017 scientists used the Atacama Large Millimeter/submillimeter Array (ALMA) to take an image of the protoplanetary disk around AB Aurigae. The image showed a dusty disk which has a radius of about 120 astronomical units and a distinct "gap". Inside this gap gaseous spiral arms are detected in CO.

Observations with ALMA found two gaseous spiral arms inside the disk. These are best explained by an unseen planet with a semimajor axis of about 60–80 au. An additional planet with a semimajor axis of 30 au and with a large pitch angle compared to the disk (likely higher inclination) could explain the emptiness of the inner dusty disk. The outer planet was still not detected as in 2022, putting an upper limit on is mass at 3–4 M_J, inconsistent with the spiral structures observed in the disk. The planet-like clump observed in April 2022 at projected separation 93 AU from star, may be either an accretion disk around newly formed planet or the unstable disk region currently transforming into the planet. Evidence for unstable disk regions transforming into companions, possibly supporting such a formation of AB Aurigae b was reported in a Nature paper published in September 2024. The planet was independently detected in July 2022.