Capella, the Flickering Goat Star, Lights Up Autumn Evening Skies

Northern Hemisphere skywatchers have an easy target on autumn evenings: Capella, a bright star that flashes red, green and blue as it hangs low over the horizon. According to EarthSky, it is the brightest star in the constellation Auriga the Charioteer, and it points the way to a small triangle of stars and three star clusters you can hunt down with binoculars.

The color show is not the star changing. EarthSky explains that Capella's light passes through a thick layer of Earth's wavering atmosphere when the star sits near the horizon, which makes the light jump around and flash.

The numbers behind Capella and Auriga

• 0.08: Capella's magnitude, a measure of apparent brightness, according to EarthSky.
• 6th: Capella's rank among the brightest stars in the sky.
• 43 light-years: its distance from us. EarthSky says its brightness comes from being nearby.
• 85 light-years: the distance to Menkalinan, Auriga's second brightest star, which marks the Charioteer's right shoulder.
• 3: the star clusters in Auriga that are easy to find with binoculars in a dark sky: M36, M37 and M38.

What kind of star Capella is

EarthSky describes Capella as golden and somewhat similar to our sun. The outlet says that from a distance of light-years, our sun might look much the way Capella looks to us. Capella marks the Charioteer's left shoulder and is nicknamed the Goat Star.

It is actually a pair of binary stars. Both are yellow giants, and each has a small red dwarf companion, according to EarthSky. Capella is also the closest first-magnitude star to Polaris, the star that currently marks the north celestial pole, and it forms one corner of the Winter Circle.

How to confirm you have found it

If you are unsure you have the right star, EarthSky suggests looking nearby for a small triangle of stars called The Kids. This asterism, a small named pattern of stars, represents baby goats that the Charioteer carries.

Another landmark is Elnath, at the southern tip of Auriga. EarthSky reports that it once belonged to both Auriga and Taurus the Bull, but in the last century the International Astronomical Union assigned it to Taurus alone.

Three clusters to try with binoculars

The three clusters fall nearly in a line, with M36 in the middle, EarthSky says. All three are open star clusters, and each looks different under magnification.

• M36 is nicknamed the Pinwheel cluster and resembles the Pleiades.
• M37 is the brightest and largest of the three. It lies opposite the Milky Way's galactic center, still within the galaxy's plane but looking toward its fringes.
• M38 is nicknamed the Starfish cluster. EarthSky notes that some observers see an X or the Greek letter Pi instead.

What this means for your evening sky-watching

For readers in the northern U.S., Canada and similar latitudes, Auriga is circumpolar, according to EarthSky. That means all or part of it is visible on any night of the year. The best views of the whole constellation start in Northern Hemisphere autumn, the outlet says.

Capella's flashing is most dramatic now because it sits low in the sky. On winter evenings it moves near the zenith, the point directly overhead. There, EarthSky says, the thinner layer of atmosphere dampens the flashiness. Learning the constellation in autumn leaves observers familiar with its stars and clusters by the time it climbs higher in winter and is better placed for viewing.

Spotting Capella needs no equipment, while the three clusters call for binoculars and a dark sky.

Source: EarthSky