HD 49976
A magnetic chemically peculiar star in Monoceros.
HD 49976 is a variable star in the constellation Monoceros (the Unicorn), designated V592 Monocerotis. It is a white-hued star near the lower limit of naked-eye visibility, with an apparent visual magnitude that fluctuates from 6.16 down to 6.32 over a period of 2.976 days. Based on parallax measurements, it lies approximately 337 light years from the Sun and is drifting further away with a radial velocity of +19 km/s.
- Variable star designation
- V592 Monocerotis
- Constellation
- Monoceros
- Apparent visual magnitude range
- 6.16 to 6.32
- Period
- 2.976 days
- Distance
- 337 light years
- Radial velocity
- +19 km/s
- Spectral type
- B9V
Lore & Background
HD 49976 is a magnetic chemically peculiar star, showing excesses of strontium and rare earth elements in its photosphere. Houk and Swift assigned it a stellar classification of B9V, matching a B-type main sequence star. It is an Alpha2 Canum Venaticorum variable, and its magnetic field is complex, not corresponding to a simple dipole. The star is estimated to be 209 million years old and spins with a period of 2.976 days. It has 2.2 times the mass of the Sun and 2.3 times the Sun's radius, radiating 32 times the Sun's luminosity from its photosphere at an effective temperature of 9,016 K.
Reader's Guide
HD 49976 is significant as an Alpha2 Canum Venaticorum variable, a class of chemically peculiar stars whose brightness variations are linked to their strong, complex magnetic fields and non-uniform surface distributions of elements. Its classification as a B9V star places it among the hotter, more massive main-sequence stars, yet its magnetic peculiarities set it apart from typical B-type stars. The star's measured rotation period of 2.976 days matches its variability period, indicating that the observed light changes are due to rotationally modulated spots enriched in strontium and rare earth elements. The complex nature of its magnetic field, not a simple dipole, adds to its interest for studies of stellar magnetism and atmospheric chemistry. Its proximity at 337 light years and brightness near naked-eye visibility make it a useful target for amateur and professional observers monitoring magnetic chemically peculiar stars. The star's radial velocity of +19 km/s indicates it is moving away from the Solar System, while its estimated age of 209 million years places it in a relatively youthful evolutionary stage.
Did You Know?
- HD 49976 has a variable star designation of V592 Monocerotis.
- It is a magnetic chemically peculiar star with excesses of strontium and rare earth elements.
- The star's magnetic field is complex and does not correspond to a simple dipole.
- It spins with a period of 2.976 days, matching its brightness variation period.
Frequently Asked Questions
What is HD 49976?
HD 49976 is a variable star catalogued as V592 Monocerotis, located in the constellation Monoceros (the Unicorn). It is classified as a magnetic chemically peculiar star, meaning its surface shows unusual abundances of certain elements driven by strong magnetic fields.
How does HD 49976 vary in brightness?
The star's apparent visual magnitude oscillates between 6.16 at maximum and 6.32 at minimum, completing one full cycle every 2.976 days. This modest swing makes it a relatively low-amplitude variable.
Where is HD 49976 in the sky and how far away is it?
It sits within the boundaries of Monoceros, the Unicorn, roughly 337 light years from the Sun based on parallax measurements. Its radial velocity of +19 km/s indicates it is slowly receding from us.
Can I see HD 49976 with the naked eye?
At its brightest it reaches about magnitude 6.16, placing it right at the very edge of what a dark-sky observer with excellent vision might glimpse. In practice, a small telescope or binoculars are the more reliable way to spot this white-hued star.
Why do astronomers care about HD 49976?
As a magnetic chemically peculiar variable, it offers a natural laboratory for studying how strong stellar magnetic fields can segregate elements in a star's atmosphere and drive short-period photometric changes. Its ~3-day cycle and well-measured distance make it a useful benchmark for modelling such exotic atmospheres.
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