HD 101584 is a star located in the constellation Cassiopeia. It is a suspected post-common envelope binary located in the constellation Centaurus, approximately 1,800 to 5,900 light-years away. It is estimated to be about 126 light-years away from the Earth and is believed to have a planetary system with at least three confirmed exoplanets. The system is visible at optical wavelengths and has an apparent visual magnitude of about 7.
The primary is either a post-AGB or a post-RGB star. The secondary is a red dwarf or possibly a low-luminosity white dwarf that orbits the primary every 150-200 days. The system is surrounded by a slowly rotating circumbinary disk, which has a face-on orientation towards the solar system and a size of about 150 astronomical units.
It is a main-sequence star with spectral type A0V. It is not particularly notable for its physical characteristics or known for any specific scientific studies. The variable star designation V885 Centauri has been assigned to HD 101584. According to the International Variable Star Index, the star’s visual magnitude varies between 6.90 and 7.02 over a period of 87.9 days. However, Koen and Eyer discovered a brightness oscillation with a period of 6.744 days and an amplitude of only 0.02 magnitudes in the star’s Hipparcos data.
This system’s companion was captured a few hundred years ago, for example, when the red giant reached critical mass. It spiraled towards the red giant but came to a halt before colliding with the primary’s core. The red giant’s outer layers were ejected during this stage. The red giant phase of the primary was terminated during the common envelope phase, revealing the core. Later, bipolar jets formed and collided with the ejected material, resulting in an hourglass-shaped structure. Ejected material contains methanol and formaldehyde, while outer ejected structures contain methanol and formaldehyde.
Because of its smaller size, the gravity at its surface is much lower, so an atom of gas sitting there feels much less of a pull downward. However, the fierce energy radiating from beneath it imparts a force outward that is stronger than gravity. The gas is expelled. This process actually removes the majority of the star’s outer layers, which flow away, leaving the star’s core, a tiny but extremely hot white dwarf, behind.
