Use Sirius to imagine sun’s path through Milky Way
If you’re in the Northern Hemisphere now, you can use the brilliant star Sirius – and the star Vega – to imagine the direction our sun and solar system are traveling through space. The sun in its orbit is traveling away from Sirius and toward the star Vega. Although we couldn’t fit them both on one chart, Vega shines over your northwestern horizon, opposite Sirius, at dusk/nightfall at this time of year. Vega sets at early evening while Sirius stays out until the wee hours of the morning.
So if you stand outside at dusk or nightfall with your back to Sirius – facing northwest – you’ll be facing the direction our solar system moves through the Milky Way galaxy. Cool, huh?
Tonight’s chart, and the photo below, both can help you be sure you’re seeing Sirius. Both show the east-southeastern sky not long after the sky gets dark, as viewed from mid-northern latitudes. The brightest star of nighttime – Sirius – shows up close to the horizon in early evening, rising upward as evening deepens into night. Sirius is found by drawing a line through the three stars of Orion’s Belt.
When an overwhelmingly bright star like Sirius hovers near the horizon, it doesn’t just twinkle. Itscintillates: sparkles in red and blue.
By the way, the direction to the star Vega – the general direction toward which our sun is traveling through space – is called the solar apex or sometimes the apex of the sun’s way.
Bottom line: Look for the star Sirius in the constellation Canis Major at nightfall tonight. It’s easy to find because it’s so bright – brightest star in the sky. Once you find it, turn around so that your back is to this bright star. You’ll be facing into the sun’s path through the Milky Way!
Bruce McClure is the chief writer for the popular EarthSky Tonight pages. Since joining EarthSky in 2004, he has written thousands of astronomy articles, enjoyed here by millions. He also writes, gives planetarium shows and hosts a wide assortment of public astronomy programs in and around his home in upstate New York. If you ask an astronomy question on our site, it’s likely to be Bruce that answers it. His love for the heavens has taken him to Lake Titicaca in Bolivia, and he has sailed the North Atlantic, earning his celestial navigation certificate through the School of Ocean Sailing and Navigation. Bruce is also a sundial aficionado. He says his number one passion – besides his wife Alice – is stargazing.
Article published on EarthSky