You are hereTHIS MONTH'S SKY - May 2010
THIS MONTH'S SKY - May 2010
THIS MONTH'S SKY
Celestial Events -- May 2010
Usually we discuss an interesting event in the current month. Frankly, there's nothing that exciting happening this May, but there are a trio of planets in the evening sky that will converge over the next few months. Following them, even only once a week, you will learn how the planets move and interact.
The planets involved are Venus, Mars and Saturn. As May begins Venus, the most brilliant object in the night sky after the Moon, is fairly low in the northwest at dusk. As the sky darkens it will become obvious. Because Venus is an inner planet (closer to the Sun than Earth) it will show phases. That is, from our viewpoint only part of it will be lit. At this time we see Venus 88% lit -- by August 31st it will be 42% lit. This is compensated by Venus' approach to Earth. From May 1 to August 31 Venus grows from 11.5" (arc seconds) in diameter to 28.5". On May 1 Venus is in the constellation Taurus, and to its left is the reddish star Aldebaran, Taurus's bright star.
Mars is high in the south-southwest in the faint constellation Cancer. Don't confuse it with the fairly nearby star Regulus. Mars is the brighter object to the west (right) and has a noticeably reddish color.
Saturn is lower in the southeast, in the constellation Virgo. Its beautiful rings can barely be made out with binoculars but are easily seen in a telescope.
MAY 1 (chart 1): Venus is a whopping 65° from Mars. In turn Mars is 45° from Saturn. To get a feel for these distances, the width of your fist at arm's length is about 10°.
DURING MAY: Watching the motion of the three planets with respect to the background stars, it soon becomes obvious that Venus is moving quite rapidly. On May 20 it leaves Taurus and enters Gemini. Venus will move 37° in May. In the same period of time Mars only travels 14°, entering Leo on May 13. Slowpoke Saturn moves less than 1 degree, and in the wrong direction (towards Mars and Venus). This strange movement, called retrograde motion, occurs because Earth is overtaking Saturn, creating the illusion that Saturn is moving backwards with respect to the stars. The Sun makes a complete 360° circuit of the sky each year, or about 360°/12 = 30° per month. Since Venus is moving faster than the Sun, it is getting higher. The other two planets are losing ground to the Sun.
JUNE 1 (chart 2): As June begins Venus is 42° from Mars, which in turn is 30° from Saturn. Venus is in the middle of Gemini not far from the bright stars Castor and Pollux. Mars is now in the east-southeast and quite close to Regulus. Saturn has barely moved.
DURING JUNE: Venus will move 35° (relative to the stars) this month, Mars 16½° and Saturn 1°. On June 6th Mars passes less than 1° from Regulus. Four days later Venus is only 5° from Pollux. Two days afterwards Venus moves into Cancer. On June 20th Venus is just above the Beehive Cluster. Ten days later Venus moves into Leo.
Venus, Mars and Saturn
9 PM May 1
JULY 1 (chart 3): Venus is now 23° from Mars and Mars 15° from Saturn.
DURING JULY: Venus travels 34°, Mars 18° and Saturn less than 2° this month. On the 10th Venus passes just over 1° above Regulus. On the 19th Mars enters Virgo.
JULY 29 -- MARS PASSES 1⅔° BELOW RIGHT OF SATURN.
SIDELINE: Mercury joins the crew this month. It is easiest to spot in the last week of July and first week of August. Look about 18° to 20° lower right of Venus. On the 27th it is less than ½° from Regulus.
AUGUST 1 (chart 4): The climax of the gathering occurs early in August. On the 1st Venus is 7¼° from Mars and 6⅔° from Saturn. Mars and Saturn are now just under 2° apart and moving away from each other.
AUGUST 7 -- VENUS PASSES 2¾° BELOW SATURN
AUGUST 7 -- CLOSEST GATHERING OF THE THREE PLANETS, 4¾°.
AUGUST 18 -- VENUS PASSES LESS THAN 2° FROM MARS.
On the 20th, Venus is at greatest elongation from the Sun (46°). On August 31 it is only 1° below Spica, the bright star in Virgo.
DENOUEMENT: The Sun catches up to the three planets, which soon will be swallowed up by twilight. To make up for this loss, Jupiter returns to the evening sky!
MERCURY is in the morning sky this month. It is close to the Sun and the angle of the ecliptic in the morning this time of year is unfavorable so it will take an effort to see it, even at greatest elongation on the 26th.
VENUS (magnitude -3.9, diameter 11.4" to12.9", phase 89% to 81% lit) by now is easily seen as a brilliant object in evening twilight. On the 16th it is occulted by the Moon, an event visible in the eastern hemisphere. It moves from Taurus into Gemini on the 20th. For more about Venus see above
MARS (magnitude +0.7 to +1.1, diameter 7.3" to 6.0") moves from Cancer into Leo on the 12th. See above for more information.
JUPITER (magnitude -2.1, to -2.3 diameter 35.1" to 37.8") moves from Aquarius to Pisces on the 3rd. In the morning sky, early in the month it rises in twilight, but by the end of May it's up around 2 or 3 AM.
SATURN (magnitude +0.8 to +1.0, diameter 19.0" to 18.2") is in western Virgo. See above.
URANUS (magnitude +5.9, diameter 3.4") is in Pisces. Jupiter is 5° to Uranus' right (west) as May begins, closing to only 1° as the month ends.
NEPTUNE (magnitude +7.9, diameter 2.3") is in western Aquarius.
PLUTO (magnitude +14.0, diameter 0.1") is still in western Sagittarius.
THIS MONTH'S EVENTS
(Times in EDT)
|May 1||Look ¼° (15') lower left of Venus for the 4th-magnitude star Kappa1 (κ1) Tauri. Kappa1 is a double star with 5th-magnitude κ2 6' to its lower left.|
|May 3||Venus is 6° north of the bright star Aldebaran in Taurus.|
|May 4||Venus is only ½° north of the star Tau (τ) Tauri.|
|May 6||Last Quarter Moon at 12:15 AM.|
|The Eta Aquarid meteor shower peaks this morning.|
|May 9||Jupiter is 7° south of the Moon.|
|May 13||New Moon at 9:04 PM.|
|May 14||This morning the star 20 Piscium (magnitude 5.5) will be ¼° lower right of Jupiter.|
|May 15||Venus is 6½° above a thin crescent Moon early this evening. Tomorrow the Moon will be 7° above Venus. In between the Moon occults Venus for the eastern hemisphere.|
|May 19||The Moon is 7° below Mars tonight.|
|May 20||First Quarter Moon at 7:43 PM.|
|May 22||Saturn is 8 ° above the Moon.|
|May 26||Mercury at greatest elongation west (25°) in the morning sky. Nevertheless it will be a difficult target for the naked eye.|
|May 27||Full Moon at 7:07 PM.|
|May 27-28||Moon and the star Antares are very close. At 1 AM they are only 1° apart.|
|May 31||Saturn is stationary, resuming direct motion (moving to the east with respect to the stars). Only ten hours later Neptune is stationary, like Saturn resuming direct motion.|
Click to get sky charts and a description of the sky for this month.
PLANETS IN MAY