56 Arietis

Lore & Background

Sanford S. Provin discovered that 56 Arietis is a variable star in 1952, and reported the discovery in 1953. It is the prototype of a class of variable stars known as SX Arietis variables, which are rotationally variable stars with strong magnetic fields. The star ranges in brightness from 5.75 down to 5.81 with a cyclical period matching its rotation rate. This is a magnetic, chemically peculiar star of the silicon type with a stellar classification of B9pSi, and it has a rapid rotation period of 17.5 hours. This period is increasing by about two seconds every hundred years. The star displays evidence of a five year period for precession of its axis.

Reader's Guide

56 Arietis holds significance as the prototype of the SX Arietis class of variable stars, a group defined by rotational variability driven by strong magnetic fields. Its discovery by Sanford S. Provin in 1952, reported the following year, established a new category of stellar behavior. As a magnetic, chemically peculiar star of the silicon type (B9pSi), it exhibits a rapid rotation period of 17.5 hours, which is gradually lengthening by about two seconds per century. The star's brightness varies between magnitudes 5.75 and 5.81 in sync with its rotation, and it also shows evidence of a five-year precession cycle of its axis. This object, visible to the naked eye as a faint blue-white point about 415 light-years away, continues to drift away from the Solar System at +18 km/s. Its legacy lies in defining a class of stars whose magnetic fields and rotation produce observable light variations, providing a benchmark for studying similar chemically peculiar stars.

Did You Know?

• Its rotation period of 17.5 hours is increasing by about two seconds every hundred years.
• Sanford S. Provin discovered its variability in 1952 and reported it in 1953.