Capella
A family of stars
A family of stars
Capella, or Alpha Auriga, is a binary star (two stars orbiting one another very closely) located 42.92 light-years away from Earth. While that's much farther than our sun, which is only 8 light-minutes away, it's still very close, considering that the Milky Way is 100,000 light-years in diameter. Because of its proximity, Capella is located on the same arm of the galaxy as we are, Orion-Cygnus.
That red dot there, labeled "Solar System," is us. Capella is just above it.
If you follow this diagram straight down from our location, you'll find the Sagittarius region of the Milky Way. In the direction of this constellation, from our perspective on Earth, lies the center of the galaxy. In the opposite direction is Capella, placing it near the Galactic Anticenter.
Auriga is a roughly pentagon-shaped constellation believed by the Ancient Greeks to trace the celestial form of Erichthonius, son of Hephaestus and patron of goatherds and shepherds.
In one hand, the charioteer cradles a goat known as Amalthea, thought to have nursed baby Zeus. Capella is the Roman word for "small goat" or "female goat," and today is the most common moniker for the star at the head of the goat or, sometimes, the shoulder of Erichthonius. Capella has also been called the Goat Star in English, al-'Ayyuq in Arabic, meaning "the goat," and mul.ÁŠ.KAR in Sumerian: "the goat star."
Two dimmer stars represent the "kids" of Capella, Haedus I (which I was born under!) and Haedus II, or Zeta and Eta Aurigae, respectively. Ancient Greek philosopher Cleostratus was the first to decide that these stars were Capella's two offspring.
In the Northern Hemisphere, we can find Auriga by first locating the big dipper, which is high up in the night sky during the spring and summer months and lower in autumn.
Follow the line of the Big Dipper's top two bowl stars, and you'll end up just below Capella. Since the star system is the 6th brightest in the night sky, it should not be too hard to spot.
Capella's spectral type is G5III, so it's no surprise that it shines so brightly. Its luminosity is 79 times that of our sun, although they are similar in temperature. Capella's magnitude is 0.08v, while our sun's is -26.74v. For these reasons, the star falls above the main spectrum on the H-R diagram, approaching red giant territory.
Astronomers believe that Capella has existed between 590 and 650 million years since it formed from a nebula. This means that it isn't a previously existing star simply taking on a different state like many do-- rather, Capella is a first-generation star formed from a cloud of dust and matter that coalesced via gravity. We're not sure, but it's possible that the binary system was created through some kind of split after the initial formation. Since Capella is relatively massive and luminous, it's expected to reach red giant status within the next few million years. Once this occurs, it will exist in that form for up to two billion years before fizzling out into a white dwarf. Unfortunately, since Capella doesn't have any surrounding planets, it's extremely unlikely that any life can occur between now and then.