Bright Venus continues to dominate the West in the evening, joined by Mercury late in the month and Jupiter in the East.
May begins and ends with a Full Moon this year. The moon first reaches the peak of its full phase at 6:09 am EDT on May 2, so it will appear big and bright both Tuesday night, May 1, and Wednesday night, May 2. The second full moon in the month, sometimes referred to as a Blue Moon, occurs on May 31 at 9:04 pm EDT. It is not often that two full moons occur in one month, thus the saying "Once in a blue moon" denotes a rare event.
Venus continues to be a showstopper in the western sky, playing the part of the Evening Star. It is visible immediately after sunset before any other stars begin to appear. If you wait until the sky darkens further and you can see more stars, you will be able to trace Venus's path through the ecliptic, or the plane in our solar system through which the planets, moon, and sun travel. Venus starts the month in the constellation Taurus, sitting between the horns of the bull. Venus is a bright magnitude -4.11 beacon, shining next to another bright light, the reddish hue of Aldebaran. Aldebaran, sometimes called Elnath, is a magnitude 1.65 star -- the brightest star in Taurus. The star marking the other horn of Taurus the Bull is Zeta Tauri, a magnitude 2.97 star. Compare the three in color, brightness, and whether they twinkle or hold steady.
On May 5, the moon makes a close approach with Jupiter in the morning sky. At magnitude -2.52, Jupiter is bright and lying 6 degrees from the moon, which is just a few days past full. Both are in the constellation Ophiuchus on Saturday night.
Mercury heads into the evening sky in the second week of May. Start looking for Mercury just after sunset on May 8. Every day it will get easier to find, as Mercury climbs higher away from the horizon after sunset and into a darker sky before it sets. New Moon occurs on May 16 at 3:27 pm EDT, and the day after, May 17, Mercury and a slender crescent moon pair up in the western sky after sunset. Mercury, at magnitude -0.81 will lie just two and a half degrees from the newborn moon. Mercury and the moon set just under an hour and a half after the sun does, giving you a fair chance to see the pairing. The next night, May 18, the moon will be about midway between Mercury and Venus. The following night, the moon joins Venus for a close pairing, just one degree away. On May 19, people will be asking, "What is that bright star next to the moon tonight?" and you will be able to tell them it is Venus, the closest planet to Earth.
The moon continues to come close to bright sky objects. On May 21, it passes the Beehive Cluster in Cancer, and the next night, May 22, the moon passes about 3 degrees from Saturn, shining at magnitude 0.30. The following night, May 23, it passes the star Regulus in Leo, and then on May 27, it pairs with bright Spica in Virgo. Spica and the moon will lie just 2 degrees apart.
On May 23, Mercury imitates Venus from earlier in the month and passes between the horns of Taurus the Bull. How does this view compare to Venus's appearance there?
Venus, meanwhile, had passed into Gemini earlier in the month and by the end of the month is lying even with the two "head" stars of Gemini, the twins Castor and Pollux. Venus is now a brighter -4.25 magnitude, with Pollux, the closer of the two, at magnitude 1.15 and Castor at magnitude 1.58.
At sunset in the eastern sky, Jupiter has been edging over the horizon, making its evening apperance late in the month. On May 31, the full moon rises seven and a half degrees from Jupiter. Just two degrees in front of the moon is the slightly dimmer star Antares in Scorpius, shining at magnitude 1.06.
The asteroid Vesta reaches opposition on May 30 and makes it closest approach to Earth on May 31. It lies not far from Jupiter and the full moon on this date, but because of the bright moon it will be difficult to see until the early days of June. Vesta shines at magnitude 5.42 in Ophiuchus. Check the asteroid observing guide for 2007 for more info.
Check out observing highlights for June 2007.
