The bright yellow star Capella shines nearly overhead in early evenings in late February/early March, as seen from mid-northern America. At 7 p.m. this week, just step outside and look high up. If the sky is clear of course, Capella will be gleaming, shining back at you with its beautiful Capella-light.
Capella-light? The Sun — you know, the star that shines so conspicuously every day and keeps us warm — sends us sunlight. It’s really starlight. Each star casts its beams on us, inviting us to enjoy its shine.
Also known as Alpha Aurigae, Capella is the brightest star in the constellation Auriga the Chariot Driver. At magnitude +0.08, Capella is the sixth brightest star visible in the night sky.
Included among the group of bright stars prominent in the winter sky, Capella is the furthest west. Back in November, when for example, when Capella was just rising in the northeast just after night fall (all of the stars move east to west as the Earth spins), we knew that Orion and all the other prominent winter evening constellations would be visible a few hours later.
Capella is also quite far north. For anyone living north of 44 degrees North Latitude (Maine through central Oregon), Capella is "circumpolar"- it circles the sky without ever setting. Anyone viewing from there can see Capella any night of the year. On June evenings the star will appear low near the northern horizon in the northern U.S., if you can avoid hills and other obstructions.
This star has been measured to be 42.9 light years from the Earth. In other words, the Capella-light you see the next clear night left the star almost 43 years ago (in 1975) and spanned 248.8 TRILLION miles (measured at the distance light travels in a second, about 186,000 miles).
I have a car that just reached 100,000 miles. That seems a lot to me, but’s it’s practically nothing. It takes an astronomer or a federal budget cruncher to visualize a trillion!
Capella is actually a system of four stars in two binary pairs. One of these pairs includes two bright yellow giant stars, both of which are approximately 2.5 times as massive as the Sun. Designated as Capella Aa and Capella Ab, they spin around a common center of gravity every 104 days, about 70 million miles apart (our Earth on average is 93 million miles from our Sun). The second pair of stars are two small red dwarf stars (Capella H and Capella L); the two pairs travel space about 929 BILLION miles apart (at its farthest, Pluto is only about 5.9 billion miles from the Sun).
So the light you see from Capella is actually the combined light of four stars (mostly Capella A and B).
Capella marks one corner of the constellation Auriga, which makes an easily-recognizable hexagon. The Milky Way Band passes here. A careful scan with binoculars on a dark night will reveal several dense star clusters, M36, M37 and M38. They are splendid in a small telescope.
February, alas, has no full Moon; the Moon reaches full phase on March 1st.
Keep looking up!
— Peter Becker is Managing Editor at The News Eagle in Hawley, PA. Notes are welcome at email@example.com. Please mention in what newspaper or web site you read this column.