V1291 Aquilae
A magnetic chemically peculiar star with a long rotational period.
V1291 Aquilae is a solitary star in the equatorial constellation Aquila. It appears yellow-white and is faintly visible without a telescope, with an apparent visual magnitude that varies around 5.65. Parallax measurements place it roughly 278 light-years from the Sun, and it is moving closer at a radial velocity of −22 km/s. This star is a magnetic chemically peculiar star, classified as an F0VpSrCrEu—an F-type main-sequence star with unusual abundances of strontium, chromium, and europium in its spectrum. It is an Alpha2 Canum Venaticorum variable, with its visual magnitude ranging from 5.61 to 5.67 over a period of 223.826 days, which is thought to be its average rotation period. V1291 Aquilae was among the first Ap stars found to have a rotation period exceeding 100 days.
- Constellation
- Aquila
- Apparent visual magnitude range
- 5.61 to 5.67
- Spectral type
- F0VpSrCrEu
- Distance
- approximately 278 light years
- Radial velocity
- −22 km/s
- Variable star type
- Alpha2 Canum Venaticorum
- Period
- 223.826 days
Lore & Background
In 1962, Helmut A. Abt and John C. Gloson published data showing that the star's brightness varied. Based on that publication, the star was given its variable star designation, V1291 Aquilae, in 1972. This is a magnetic chemically peculiar star, or Ap star, with a stellar classification of F0VpSrCrEu, matching an F-type main-sequence star with abundance anomalies of strontium, chromium, and europium in the spectrum. It is a variable star of type Alpha2 Canum Venaticorum that ranges in visual magnitude from 5.61 down to 5.67 with a period of 223.826 days. This is most likely the mean rotational period of the star. V1291 Aquilae was one of the first Ap stars discovered with a period of more than 100 days.
Reader's Guide
V1291 Aquilae holds significance as one of the early discoveries of an Ap star with a rotational period exceeding 100 days, a milestone in the study of chemically peculiar stars. Its classification as an Alpha2 Canum Venaticorum variable links its brightness variations to the star's rotation and the patchy distribution of chemical elements on its surface, modulated by a strong magnetic field. The star's spectrum, showing anomalies of strontium, chromium, and europium, places it among the magnetic chemically peculiar stars that provide insight into atomic diffusion and magnetic field effects in stellar atmospheres. Its long period of 223.826 days, likely the rotational period, makes it a benchmark for understanding slow rotators in this class. The star's yellow-white hue and naked-eye visibility allow amateur observers to track its subtle magnitude changes over months. The designation V1291 Aquilae, assigned in 1972 following the 1962 brightness variation data, marks its formal recognition as a variable star. Its radial velocity of −22 km/s indicates it is drifting closer to the Sun, though at a distance of about 278 light years, this motion is gradual.
Did You Know?
- V1291 Aquilae has a rotational period of 223.826 days, one of the longest known among Ap stars.
- The star's spectrum shows abundance anomalies of strontium, chromium, and europium.
- Its variable star designation was assigned in 1972 based on brightness variation data published in 1962.
Frequently Asked Questions
What is V1291 Aquilae?
It is a solitary yellow-white star in the constellation Aquila, just barely visible to the unaided eye with a visual magnitude hovering near 5.65.
What type of variable star is V1291 Aquilae?
It is classified as an Alpha2 Canum Venaticorum variable, showing a small brightness swing between magnitudes 5.61 and 5.67 driven by its long rotational period.
How far away is V1291 Aquilae, and is it getting closer?
Parallax measurements place it at roughly 278 light-years from the Sun, and its negative radial velocity of 22 km/s tells us it is slowly drifting toward the Solar System.
What makes V1291 Aquilae chemically unusual?
Its F0VpSrCrEu spectral type flags it as a magnetic chemically peculiar star, with surface layers enriched in strontium, chromium, and europium relative to a normal F-type main-sequence star.
Why does V1291 Aquilae's brightness vary at all?
The star's magnetic field concentrates those extra elements into patches on its surface, so as the star rotates slowly those bright and dim regions cycle into and out of view, producing the modest magnitude change.
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