The Big Dipper
Of the very brightest stars (called 1st-magnitude stars) none are in the northern-most night sky, yet that part of the sky holds seven moderately bright stars that form a pattern more familiar than any of the brightest stars.
Of the very brightest stars (called 1st-magnitude stars) none are in the northern-most night sky, yet that part of the sky holds seven moderately bright stars that form a pattern more familiar than any of the brightest stars.
The Big Dipper, probably the best-known pattern in the entire northern hemisphere, is part of the constellation named Ursa Major, the Big Bear.
The Little Dipper, part of Ursa Minor, the Little Bear, is not so easy to identify as four of its seven stars are faint. It does, however, contain the North Star, also known as Polaris. Since it is straight up from Earth’s North Pole, Polaris never moves in our sky. It is always due north and the same distance (in degrees) above the horizon as the latitude from which it is being viewed. The two stars forming the outer end of the Big Dipper’s bowl are “pointer stars” pointing toward Polaris.
Polaris is like the center of a 24-hour clock with all the other stars moving around it like the clock’s hands, although in a counterclockwise direction. And just as stars circle Polaris, so do star patterns, including the Big Dipper. Depending upon the season and time of night, the Big Dipper might be above, below or east or west of Polaris.
There’s a legend that helps know where to look for the Big Dipper in the early evening. In the fall the dipper is due north below Polaris, down near Earth filling its bowl with water.
In the winter it is to the east (right) of Polaris with its bowl tilted on its side and its handle pointing downward. The water doesn’t spill out because, being winter, it’s frozen.
In the spring the Big Dipper is again due north but above Polaris in an upside-down position. The water, now thawed, is pouring out of the dipper’s bowl bringing us spring rains.
By summer, the dipper has swung around to the west (left) of Polaris with its bowl again tilted on its side and its handle pointing upward. It no longer has any water to spill on Earth, accounting for our dry, hot summers.
And the next fall it again swings down near Earth to again fill its bowl with water and begin the cycle anew. Right now in the early evening, as spring is about to turn to summer, the Big Dipper is to the upper left of Polaris.
• Sky Calendar.
* June 4 Fri.: The Moon is at 3rd quarter.
* 6 Sun. morning: The crescent Moon is to the upper right of Jupiter low in the east before dawn.
* 6 Sun. evening: Mars is just to the upper left of Leo’s bright star Regulus high in the west.
* 8 Tue. morning: Jupiter passes less than a moonwidth from Uranus; seeing much fainter Uranus requires binoculars.
* 10 Thu. morning: The crescent Moon is above Mercury low in the east northeast at dawn, and the next morning to Mercury’s left.
* 10-12 Thu.-Sat. early evenings: Venus and Gemini’s bright stars Pollux and Castor are aligned and equally spaced low in the west at dusk.
* 12 Sat.: The Moon is new.
* 14 Mon. early evening: The crescent Moon is below Venus low in the west.
* 16 Wed. evening: The crescent Moon is below Mars, and then to Mars’ left the next night.
* 18 Fri. evening: The 1st quarter Moon is below Saturn.
• Naked-eye Planets. (The Sun, Moon, and planets rise in the east and set in the west due to Earth’s west-to-east rotation on its axis.) Evening: “Evening star” Venus is prominent in the west northwest, Mars is mid way up in the west, and Saturn is high in the southwest. Morning: Jupiter rises two hours before the break of dawn with Mercury very low in the east at dawn.
• Star Party. The Central Texas Astronomical Society’s free monthly star party is Saturday, May 5, at the Lake Waco Wetlands beginning at 8:30 p.m. For directions see my Web site.
Stargazer appears every other week. Paul Derrick is an amateur astronomer who lives in Waco. Contact him at 918 N. 30th, Waco, TX 76707, (254) 753-6920 or . See the Stargazer Web site at <stargazerpaul.com>.
