Merope (star)

Lore & Background

Merope is a blue-white B-type subgiant with a mean apparent magnitude of +4.18, described by Richard Hinckley Allen as lucid white and violet. Its luminosity is 927 times that of the Sun and its radius is 4.8 times the Sun's. The star's mass is roughly stated but not precisely quantified in the notes.

In 1985, Bernard J. McNamara announced that Merope's brightness varies with time. It is classified as a Beta Cephei variable, a type of hot variable star that pulsates regularly due to opacity changes in its atmosphere. Its brightness varies by up to 0.01 magnitudes per pulsation cycle, with a stable period of 0.49 days, though the amplitude of brightness changes on each cycle varies.

Surrounding Merope is the Merope Nebula (NGC 1435), which appears brightest around the star and is also listed as IC 349. Some papers have reported a companion star at a separation not specified, along with several other visual companions farther out, but these have not been confirmed.

Reader's Guide

Merope's significance lies in its membership in the Pleiades star cluster, one of the closest star clusters to Earth, though its exact distance remains disputed. The star's own parallax is not known precisely enough to give an accurate distance; Hipparcos measurements gave a distance of 116 parsecs with a 5% margin of error, while the overall cluster distance from Hipparcos was 120 parsecs. These values are inconsistent with other parallax measurements, such as those from Gaia, which cannot reliably measure Merope due to its brightness. Repeated calculations using Hipparcos, Gaia, the Hubble Space Telescope, and other methods indicate that the Hipparcos parallaxes suffered from systemic error, and the distance to the Pleiades is most likely around 135 parsecs.

As a Beta Cephei variable, Merope contributes to the study of stellar pulsation and opacity-driven variability in hot stars. Its variable star designation V971 Tauri was assigned following the discovery of its brightness variations. The star also carries cultural and historical weight through its name Merope, derived from Greek mythology as one of the seven daughters of Atlas and Pleione known as the Pleiades. In 2016, the International Astronomical Union's Working Group on Star Names approved Merope as the official proper name for this star, and it is entered in the IAU Catalog of Star Names.

Did You Know?

• Merope is designated 23 Tauri and also V971 Tauri as a variable star.
• The Merope Nebula (NGC 1435) surrounds the star and is also cataloged as IC 349.
• The distance to Merope is disputed, with Hipparcos giving 116 parsecs but other methods suggesting about 135 parsecs.