Skywatch: Star hopping in the spring sky

12 May 2024

Finding your way around the night sky can be really intimidating, especially if you’re new to stargazing. The best way to learn the constellations is to use the ones you can recognize to help you find the ones you’re unfamiliar with and those that aren’t as bright. Another fun way to learn to navigate the sky is star hopping, traveling from one star to another across the celestial dome with your eyes rather than a spaceship. It works well!

Our starting point will be very easy to find: the Big Dipper, the rear end and tail of the constellation Ursa Major, the Big Bear. We won’t worry about the rest of the Big Bear right now; we’ll concentrate on the Big Dipper, hanging upside down in the early evening May sky. First, we want to face north and look up at the two stars on the left side of the pot opposite the handle. Shoot a line downward from those two stars, Merak and Dubhe, and you’ll run right into Polaris, otherwise known as the North Star. If you extend a clenched fist at arm’s length, three of those fist-widths will get you from Dubhe to Polaris. Polaris is the brightest star in the much fainter Little Dipper, and Polaris is positioned at the end of the handle.

(Mike Lynch)

Next, face due east as best you can. From that vantage point, the Big Dipper will appear to be standing on its handle. Extend the arced line of the handle stars; handle stars Alioth, Mizar, and Alkaid beyond the handle, and you arch yourself directly to the very bright and orange-hued star Arcturus. This famous star-hopping tip is called “arc to Arcturus.”

Arcturus is one of the brightest stars in the spring and the brightest star in the constellation Bootes the Herdsman or Farmer. Facing to the east, Bootes actually looks much more like a big sideways kite pointing to the left or north, with Arcturus serving as the tail of the kite. Some folks see Bootes as a one-scoop ice cream cone lying on its side.

Astronomically, Arcturus is considered a bloated red giant star nearing the end of its life. It’s over 21 million miles in diameter, about 25 times the sun’s diameter. It used to be about the same size as our sun, but crazy helium fusion has caused it to expand rapidly. Arcturus lies about 37 light years from Earth, with just one light year equaling nearly 6 trillion miles. The light from Arcturus tonight originally left that star when The Minnesota Twins won the World Series for the first time in 1987.

Arc to Arcturus isn’t the end of the arc, though. Continue the arc, and you’ll eventually run into a bright star with a slightly blue hue. That’s Spica in the low southeast heavens. I’ve also heard the adage “Arc to Arcturus and then spike to Spica.”

Spica, about 250 light years away and nearly eight times the diameter of our sun, is the brightest star in the very large but very faint constellation Virgo the Virgin. Spica is close by one of my favorite constellations, Corvus the Crow. If you’re still facing east, look for a lopsided trapezoid to the right or south of Spica. That trapezoid is supposed to be a crow? Good luck seeing that!

There you have it, a classic example of a star hopping in the sky. With any star map, you discover other star-hopping tricks to travel all around the great celestial dome, making the stars your old friends!

Mike Lynch is an amateur astronomer and retired broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and Mike is available for private star parties. You can contact him at [email protected].

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