8/16/2023 0 Comments Autumn sky map algol![]() ![]() That seems like a lot to us, but consider that our innermost planet, Mercury, averages 36 million miles away from the sun, and the Ssun is almost a million miles across (864,000 miles). Beta Persei A and B are thus 5,766,000 miles apart. One astronomical unit is the average distance between the Earth and sun, or 93 million miles. That’s another way distance is measured within solar systems. Too bad.Ī and B are separated by only 0.062 astronomical units (AU). Nevertheless, more fun names don’t seem to slip in official classifications. Maybe you can apply a better trio of names, such as Huey, Dewey and Looie. There are actually three stars in the system the brightest is referred to as Beta Persei A the star that eclipses it from our line of sight is Beta Persei B the other is Beta Persei C. The star is also referred to as Beta Persei. Once you find the constellation with a star map, you can compare Algol with nearby stars to estimate its brightness. Algol is one of the brighter stars of the constellation Perseus. Look for Algol in the northeast, below the W-shaped constellation Cassiopeia. (For comparison, the stars of the Big Dipper are also 2nd and 3rd magnitude.) Usually shining at a near constant magnitude +2.1, it dips to +3.4 every two days, 20 hours and 49 minutes. Unlike other variables where the change is due to pulsations within the star, the reason for the wink is its companion star.Īlgol has another, dimmer star in a tight orbit, which like clockwork partially eclipses Algol. You can easily watch it change light over several nights. ![]() Some rise from seeming insignificance requiring a good telescope to easy visibility with just your pearly whites.Īlgol is a famous variable star of the evening autumn sky. There are numerous types of variable stars most change on a fairly regular basis, over a predictable length of time and range of magnitude. There are thousands of stars you can see that vary in brightness. The next clear night be sure to look up the star that winks back. If you see any problems with this tool, or any of our interactive tools, please send an email to. The orbital period of the binary undergoes slight but unpredictable long-term drifts. In December 2021 we revised the prediction formula to better match Algol’s current minima. The times given should be accurate to within a few minutes. Or you can enter any current date to see the dates and times of eight consecutive minima. Click "Initialize to today" to view the dates and times of Algol's minima for the next three weeks. (For detailed tips on estimating a variable's brightness, see "The Lure of Variable Stars." For information and finder charts for Algol and 11 other inconstant stars, see "The Top 12 Naked-Eye Variable Stars.") Below is a calculator you can use to predict when Algol will be at mideclipse. You can compare Algol's brightness with them at a glance click on the star chart to see a larger version with the magnitudes of several comparison stars clearly labeled. Good comparison stars are Gamma (γ) Andromedae to Algol's west, magnitude 2.1, and Epsilon (ε) Persei to its east, magnitude 2.9. Algol stays nearly that faint for two hours centered on the time of mideclipse, and it takes several additional hours to fade and to rebrighten. In the middle of an eclipse it shines dimly at magnitude 3.4 instead of its usual 2.1. Its changes are very plain to the naked eye. Algol fades and rebrightens like clockwork every 2.87 days. You can check on it whenever you step outdoors on nights when Perseus is in view. Sky & Telescope The star Algol (β Persei) was the first eclipsing variable star ever discovered, and it's still the most famous one. Good comparison stars are Gamma Andromedae to Algol's west, magnitude 2.1, and Epsilon Persei to its east, magnitude 2.9. The star Algol (Beta Persei) was the first eclipsing variable star ever discovered. ![]()
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