The April 25 edition of the Bangor Daily News carried a piece about astronomers detecting an earthlike planet around a nearby star. This is “nearby” only in astronomical terms for the star, Gliese 581, is 20 light-years or 120 trillion miles from Earth.

And to answer an often asked question, a light-year is a unit of distance, not time, and is equal to about 6 trillion miles. It is the distance light travels in one year at a speed of 186,000 miles per second and, when observing the light from far distant stars, it is like “looking back into time.”

The light from Gliese 581 astronomers see today left the star 20 years ago. This fact was used to open the 1933 Chicago World’s Fair. A previous World’s Fair was held in Chicago in 1893 and some observant soul noticed that the star Arcturus is 40 light-years from Earth, meaning that light leaving the star in 1893 would arrive at the opening of the 1933 Fair.

Photoelectric cells were a new invention and it was decided to open the fair by training light from Arcturus on a photocell and use the electricity produced to activate a switch turning on the lights. This was done and new technology was joined with astronomy to give an opening that was spectacular by every measure – even light-years!

Focus on the planets

Mercury makes its best appearance for 2007 during the latter half of the month. Starting around mid-May, look for Mercury shining brightly just above the northwestern horizon as darkness falls.

Venus blazes high in the west at sunset, where it remains in view for nearly two hours. On May 19 an extremely close pairing of Venus and the crescent moon makes a stunning sight.

Mars is low in the southeast at dawn where it will be difficult to observe in the glow of the rising sun. On May 13, Mars is directly to the right of the crescent moon.

Jupiter rises in the southeast shortly before midnight as May opens and by sunset at month’s end. Jupiter is visible throughout the night but the best time for viewing is after midnight when it is highest in the sky. The four major moons of Jupiter give a varied show each night. The reddish star to the right of Jupiter is Antares.

Saturn is high in the south at sunset well to the upper left of Venus, but the gap between the two planets is cut in half over the course of the month. Saturn’s rings are still favorably tilted for viewers with telescopes to be able to pick out details between individual rings.

Uranus and Neptune are not visible in May as they rise with the glare of dawn.

May events

1 Sunrise, 5:26 a.m.; sunset, 7:40 p.m. This is May Day or Beltane, a cross-quarter day marking the midpoint between the spring equinox and summer solstice.

2 Full moon, 6:10 a.m. The full moon of May is called variously the Milk Moon, Flower Moon or Corn Planting Moon.

4 Jupiter is to the upper left of the moon during the late night hours with Antares to the moon’s upper right.

6 Peak night for the Eta Aquarid meteor shower. Derived from Halley’s comet, the Aquarids produce bright, fast-moving meteors at a rate of one every minute or so but this year viewing will be diminished due to the recent full moon.

10 Moon in last quarter, 12:27 a.m.

13 Look for Mars directly to the right of the crescent moon at dawn.

14 The sun enters the constellation of Taurus the Bull on the ecliptic.

15 The moon is at perigee, or closest approach to Earth, today.

16 New moon, 3:28 p.m.

17 Look very low to the northwest at dusk where Mercury is just below a thin crescent moon. The red-orange star far to the left of Mercury is Betelgeuse.

19 Don’t miss the extremely close pairing of Venus and the moon high in the west at twilight!

21 The sun enters the astrological sign of Gemini but astronomically is still in Taurus.

22 Saturn is less than a degree to the right or lower right of the moon this evening.

23 Moon in first quarter, 5:02 p.m.

27 The moon is at apogee, or farthest distance from Earth, today.

31 Full moon, 9:04 p.m. This is the second full moon of the month making it a “Blue Moon.” Antares lies to the upper right of the moon with Jupiter to upper left. Sunrise, 4:53 a.m.; sunset, 8:13 p.m.

Send astronomical queries to Clair Wood at cgmewood@aol.com or care of the Bangor Daily News, Lifestyle Desk, P.O. Box 1329, Bangor 04402.