LY Aurigae
LY Aurigae is a bright, young quadruple star system in the constellation Auriga, about 6,800 light-years from Earth. It appears as a close pair of stars, LY Aur A and LY Aur B, that are separated by only about 0.6 arcseconds.
LY Aur A is itself a tight eclipsing binary. Its two hot, massive stars (both of spectral type O) orbit each other every 4 days and are in very close contact. This causes the system’s brightness to dim during eclipses: the primary eclipse drops by about 0.69 magnitudes and the secondary by about 0.60 magnitudes. Because the stars are deformed from their mutual gravity, the light changes smoothly throughout the orbit.
In LY Aur A, the brighter component (Aa) is about 25.5 solar masses and roughly 16 solar radii, with a surface temperature around 31,000 K. The companion (Ab) is about 14 solar masses and 12.6 solar radii, also very hot, with a similar temperature. Each star is extremely luminous—tens to hundreds of thousands of times brighter than the Sun.
LY Aur B, the other visible star in the pair, is itself a binary system. It has a 20.5-day orbit and its companion is difficult to detect directly. The primary in LY Aur B is a hot B-type star with a luminosity of tens of thousands of Suns, and the system as a whole is highly luminous.
Overall, LY Aurigae is a quadruple star system: two bright, close stars forming LY Aur A and two stars forming LY Aur B, visible as a pair about 0.6 arcseconds apart. The entire system lies in a young stellar region called the Auriga OB1 association and is estimated to be about 5 million years old.
This page was last edited on 3 February 2026, at 05:45 (CET).