19 Monocerotis
A massive B-type main-sequence star and Beta Cephei variable.
19 Monocerotis, also known by its variable star designation V637 Monocerotis, is a solitary star in the equatorial constellation Monoceros. Based on parallax measurements, it lies roughly 1,220 light-years from the Sun. With a baseline apparent visual magnitude of 5.00, it appears as a faint, blue-white point of light visible to the naked eye. The star is moving away from Earth at a heliocentric radial velocity of +25 km/s.
This massive star is a B-type main-sequence star with a stellar classification of B1 V. It is a Beta Cephei variable, with its brightness fluctuating between magnitudes 5.01 and 4.96 over a period of 0.19 days. More detailed analysis reveals three distinct pulsation frequencies: 5.22994, 0.17017, and 4.88956 cycles per day. It was once considered a possible marginal Be star, but that classification was not confirmed. The star rotates rapidly, with a projected rotational velocity of 274 km/s. It has 12.3 times the mass of the Sun and radiates 4,817 times the Sun's luminosity from its photosphere, which has an effective temperature of 25,400 K.
- Stellar classification
- B1 V
- Mass
- 12.3 solar masses
- Luminosity
- 4,817 solar luminosities
- Effective temperature
- 25,400 K
- Projected rotational velocity
- 274 km/s
- Apparent visual magnitude
- 5.00 (baseline)
- Radial velocity
- +25 km/s
Lore & Background
This massive, B-type main-sequence star has a stellar classification of B1 V. It is a Beta Cephei variable, ranging from 5.01 to 4.96 magnitude with a period of 0.19 days. Closer examination shows there are three frequencies present, consisting of 5.22994, 0.17017, and 4.88956 cycles per day. At one point it was thought to be a marginal Be star, but this was not confirmed. The star is spinning rapidly with a projected rotational velocity of 274 km/s. It has 12.3 times the mass of the Sun and is radiating 4,817 times the Sun's luminosity from its photosphere at an effective temperature of 25,400 K.
Reader's Guide
19 Monocerotis, also known as V637 Monocerotis, is notable as a Beta Cephei variable star, a class of pulsating variables that are important for studying stellar structure and evolution through asteroseismology. Its three detected pulsation frequencies provide insight into the internal dynamics of massive B-type stars. The star's rapid rotation and high temperature place it among the more extreme members of its class. Although once considered a marginal Be star, that classification was not confirmed, leaving its status as a non-Be star significant for understanding the boundary between normal B stars and Be stars. Its brightness as a naked-eye object makes it accessible for amateur and professional monitoring alike, contributing to long-term studies of stellar variability. The star's distance of about 1,220 light years and its radial velocity of +25 km/s help map the kinematics of the Milky Way in the Monoceros region.
More in Variable Stars, Part 6 1-24
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