On June 5 one of the rarest events in our solar system will occur. This is the transit of Venus, when the planet appears as a tiny black dot moving across the face of the sun.
Transits come in pairs — the last was June 8, 2004 — but the pairs are separated by 105.5 or 121.5 years. The last pair was between 1874 and 1882. Edmund Halley proposed in 1716 that the transits, viewed from two widely separated positions on Earth, could be used to measure the distance from Venus to the sun by triangulation. He never lived to see a transit, but in 1769, two teams were sent by Britain to measure that year’s transit from Tahiti and northern Norway.
Measurements taken from the American colonies of the 1769 transit are often credited with fostering the birth of American science. The optimum viewing time for this year’s transit is listed for the Maine area as 9:27 p.m. June 5, and Venus should appear very near the top of the Sun’s disk.
If you miss out, another one will occur in 2117.
CAUTION: Do not look directly at the Sun with the naked eye at any time while attempting to view the transit.
Focus on the planets
Mercury emerges low in the west-northwest about an hour after sunset around midmonth. Mercury sets about 2 hours after the sun and will be readily visible to the upper right of the crescent moon on June 21.
Venus follows its historic transit by emerging in the east at dawn to the lower left of Jupiter. Venus is up only 15 minutes before sunrise as June opens but by two hours at month’s end.
Mars is high in the northern sky at sunset at the first of the month where it is nestled among the stars of Leo. Check out Mars on June 25 when it is directly above the crescent moon.
Jupiter rises in the east less than one hour before the sun at the start of June but by more than 2 hours by month’s end. Jupiter is joined by the thin crescent moon on June 17 with Venus to the pair’s lower left.
Saturn is high in the west-southwest around 11 p.m. The bright star Spica is to Saturn’s lower left.
Uranus and Neptune are in Cetus and Aquarius respectively. Both are fairly high at dawn and can be found with finder’s charts published at www.skypub.com/urnep.
1: Sunrise, 4:53 a.m.; sunset, 8:14 p.m. Venus and Mercury are separated by about one-quarter of a degree this evening. This is the closest planet-to-planet approach this year.
3: The moon is at perigee or closest approach to the earth.
4: Full moon, 7:11 a.m. The full moon of June is called the Rose Moon, the Flower Moon or the Strawberry Moon.
5: Venus transits, or passes in front of the face of the sun, for the last time in more than a century.
11: Moon in last quarter, 6:42 a.m.
16: The moon is at apogee or farthest distance from Earth. Jupiter is just to the lower left of the moon at dawn, however, both are quite low in the sky so you will need an unobstructed horizon.
17: Venus, the thin crescent moon, and Jupiter form an ascending line on the eastern horizon just before sunrise. The Pleiades are to the upper left of Jupiter.
19: New moon, 11:02 a.m.
20: Summer solstice, 7:07 p.m. The sun reaches its northernmost point, or 23.5 degrees above the equator. The sun enters the astrological sign of Cancer on the solstice but astronomically is just leaving Taurus.
21: Mercury is just to the upper right of the thin crescent moon in the northwest about an hour after sunset. The two bright stars to the upper right of Mercury are Castor and Pollux. The sun enters the astronomical sign of Gemini.
25: Reddish-orange Mars is located just above the moon in the southwest an hour before midnight. Saturn is far to the upper left of Mars.
27: Moon in first quarter, 11:29 p.m. This is the peak night for the Bootids meteor shower. Erratic, a high number of meteors in 2004 was followed by almost none in 2010 when another profuse shower was expected. Look for the occasional slow-moving meteor out of the region of Bootes.
29: Look to the east-northeast at dawn for an ascending line of Aldebaran, Venus, Jupiter and the Pleiades.
30: Sunrise, 4:52 a.m.; sunset, 8:25 p.m.
Send astronomical queries to Clair Wood at email@example.com or c/o Bangor Daily News Style Desk, P.O. Box 1329, Bangor 04402.