MY Apodis
A pulsating white dwarf in Apus, discovered in 1974.
MY Apodis (also cataloged as L 19-2, GJ 2108, or WD 1425-811) is a solitary white dwarf situated in the far-southern constellation Apus. With an average apparent visual magnitude of roughly 13, it is far too dim for naked-eye observation. Parallax measurements place it 68.3 light-years from the Sun, and it is moving away at a radial velocity of 58.0 km/s.
This compact stellar remnant is classified as DA4.1, meaning its outer atmosphere is rich in hydrogen. It belongs to the ZZ Ceti class of pulsating white dwarfs, exhibiting photometric variations with an amplitude of 0.05 in visual magnitude. The low-amplitude variability was first detected by James E. Hesser and colleagues in 1974, who recorded periods of 192.75 ± 0.1 seconds and 113.77 ± 0.1 seconds. By 2015, ten distinct pulsation modes had been identified, and the star’s behavior has remained stable over four decades of observation.
MY Apodis packs 70.5% of the Sun’s mass into just 1.1% of its radius. It rotates rapidly, completing a full spin every 13 hours. The star radiates only 0.35% of the Sun’s luminosity, with an effective temperature of 12,330 K. Astroseismological modeling suggests a thin outer hydrogen shell with a mass of 1.0 × 10⁻⁴ M☉, an intermediate helium layer of 1.5 to 2.0 × 10⁻² M☉, and a core composed of 20% carbon and 80% oxygen, extending out to 60% of the stellar radius.
- Constellation
- Apus
- Distance
- 68.3 light-years
- Radial velocity
- 58.0 km/s (drifting further away)
- Spectral class
- DA4.1
- Mass
- 70.5% of the Sun's mass
- Radius
- 1.1% of the Sun's radius
- Rotation period
- 13 hours
- Luminosity
- 0.35% of the Sun's luminosity
- Effective temperature
- 12,330 K
- Apparent visual magnitude
- about 13
Lore & Background
MY Apodis is a compact stellar remnant with a class of DA4.1, indicating a hydrogen-rich outer atmosphere. It is a pulsating white dwarf (ZZ Ceti star) that varies photometrically with an amplitude of 0.05 in visual magnitude. The low-amplitude variability was discovered by James E. Hesser and associates in 1974, who found it showed periods of 192.75±0.1 and 113.77±0.1 seconds. By 2015, ten different pulsation modes had been identified, and it remained stable over four decades of observation.
The star has 70.5% of the mass of the Sun compressed down into 1.1% of the Sun's radius. It is spinning rapidly with a rotation period of 13 hours. The star is radiating just 0.35% of the luminosity of the Sun at an effective temperature of 12,330 K. Astroseismological models suggest the star has a thin outer hydrogen shell with a mass of 1.0×10−4 M☉, an intermediate helium layer of 1.5 to 2.0×10−2 M☉, and a core of 20% carbon and 80% oxygen that extends out to 60% of the stellar radius.
Reader's Guide
MY Apodis is significant as a ZZ Ceti star, a class of pulsating white dwarfs that provide insights into the internal structure of degenerate matter. Its discovery by James E. Hesser and associates in 1974 marked the identification of a low-amplitude variable with periods of 192.75±0.1 and 113.77±0.1 seconds. Over four decades of observation, ten pulsation modes were identified, and the star remained stable, making it a valuable target for astroseismology. The astroseismological models derived from its pulsations reveal a layered interior: a thin outer hydrogen shell, an intermediate helium layer, and a core composed of 20% carbon and 80% oxygen extending to 60% of the stellar radius. These details help constrain theories of white dwarf evolution and cooling. The star's rapid rotation period of 13 hours and its low luminosity (0.35% of the Sun) at an effective temperature of 12,330 K further characterize this remnant. Its distance of 68.3 light-years and radial velocity of 58.0 km/s (drifting away) place it in context within the solar neighborhood. The star's variability amplitude of 0.05 in visual magnitude and its faint apparent magnitude of about 13 underscore the need for sensitive photometry to study such objects.
Did You Know?
- It has a rotation period of 13 hours.
- The star's core is 20% carbon and 80% oxygen, extending to 60% of its radius.
Frequently Asked Questions
What is MY Apodis and where can I find it in the sky?
MY Apodis is a lone white dwarf star located in the far-southern constellation Apus, and it carries several alternate catalog designations including L 19-2, GJ 2108, and WD 1425-811. At an average visual magnitude of about 13, it is entirely invisible to the unaided eye and requires a telescope to observe.
What kind of variable star is MY Apodis?
It is a ZZ Ceti-type pulsating white dwarf whose outer atmosphere is dominated by hydrogen, earning it the spectral label DA4.1. Its brightness oscillates by roughly 0.05 magnitudes in the visual band as the star pulses.
How far is MY Apodis from Earth and is it getting closer or farther?
Parallax measurements place it at approximately 68.3 light-years from the Sun. It is currently receding at a radial velocity of 58.0 km/s, so the distance between us is steadily increasing.
How does MY Apodis compare in size and mass to our Sun?
Although it is a compact stellar remnant, it still retains about 70.5 percent of the Sun's mass while its radius has shrunk to just 1.1 percent of the solar radius, making it an extraordinarily dense object.
When was MY Apodis discovered and why is it notable to variable-star astronomers?
The star was identified in 1974 as a pulsating white dwarf, adding to the roster of known ZZ Ceti-class variables. Its small, steady-amplitude brightness oscillations make it a useful reference for studying how compact stellar cores vibrate and gradually cool over time.
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