You are hereTHIS MONTH'S SKY - March 2010
THIS MONTH'S SKY - March 2010
THIS MONTH'S SKY
Celestial Events -- March 2010
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The planet Saturn is at opposition on March 21st. This means Sun, Earth and Saturn lie in a straight line, with Earth in the middle. Saturn is at its closest around this time. (If planetary orbits were circles opposition would be the moment a planet is closest, but because they are ellipses, the date the two planets are closest may differ by a few days.) At opposition, a planet is literally opposite the Sun (from Earth's point of view). So Saturn rises when the Sun sets, and sets at sunrise. Therefore it's up all night. The first thing about Saturn we think of is its rings. Last year the rings were edge-on and almost invisible, an event that occurs every 15 years. Now the rings are clearly visible through a telescope, though their tilt from our line of sight is only 3° or 4° this month. As with all planets at opposition, Saturn is retrograding now. That is, it is moving towards the west with respect to the background stars. This effect is caused by a change in perspective, due to Earth passing Saturn. Saturn will "turn around" and begin moving east on May 31st. At upper right is a movie of Saturn in 2010 as seen from Earth. The change in Saturn's size (as it gets closer and farther away from Earth) and the orientation of the rings can be seen. The tilt of the rings will increase this year, part of the 15-year periodicity described above. However, because of Earth's own motion around the Sun, superimposed on the tilt is a smaller effect caused by our own changing perspective. |
Saturn in 2010 
Saturn in March 2010 10 PM EDT |
At lower right is a star chart giving Saturn's location at 10 PM EDT in March. Mars can be seen near the top of the chart. Not visible at this time is Venus, which set in evening twilight. Over the next few months, Venus will approach Mars, which in turn will approach Saturn. There will be a wonderful gathering of the three planets in August.
VENUS ENTERS THE EVENING SKY AND GETS COMPANY
| Venus begins an apparition of several months in the evening sky. Early in March it is very low in the west but gets higher each passing week. By the end of the month it is a brilliant beacon, 12° above the horizon 30 minutes after sunset..
At this time of year (spring) the ecliptic, the path taken by the planets, rises steeply in the west at dusk. Venus is not the only planet that benefits from this -- Mercury becomes visible the last week of the month. Mercury actually begins March in the morning sky, too close to the Sun to be seen. It is in conjunction with the Sun on the 14th, moving into the evening sky. Because of its speed and the favorable angle of the ecliptic, less than two weeks later it can be seen near Venus. |
Venus and Mercury |
On March 31 the two planets are only 3½° apart -- use far brighter Venus to spot Mercury at about 4 o'clock. The two planets will get a little closer the first week of April, after which Mercury will retreat and fade dramatically, as can be seen from the movie of the planet's movements at right.
Venus will stay around until August, when it will be joined by Mars and Saturn in a beautiful gathering.
Click to get sky charts and a description of the sky for this month.
PLANETS IN MARCH
MERCURY begins March in the morning sky. On the 14th at superior conjunction it enters the evening sky. Because of Mercury's speed and the favorable tilt of the ecliptic it can be spotted by binoculars within a week and by naked eye the last week of the month. See above for more details.
VENUS (magnitude -3.9, diameter 10.0" to10.5", phase 98% to 95% lit) is becoming prominent in the western sky at dusk. She is joined late in March and early in April by Mercury, which reaches to within 3½° from Venus. See (above).
MARS (magnitude -0.6 to +0.1, diameter 12.1" to 9.3"), in Cancer, dramatically fades during the month, as Earth moves farther away. It will be stationary on March 11, resuming direct motion (moving east with respect to the stars).
JUPITER (magnitude -2.0, diameter 33.0" to 33.5") is in Aquarius. Now in the morning sky, it becomes visible later in the month.
SATURN (magnitude +0.6, diameter 19.4" to 19.5") is in western Virgo. It is at opposition on the 21st (see above).
URANUS (magnitude +5.9, diameter 3.3") is in Pisces. It is in conjunction with the Sun on the 17th and lost to view this month.
NEPTUNE (magnitude +8.0, diameter 2.2"), now in the morning sky, moves from Capricornus into Aquarius on the 23rd.
PLUTO (magnitude +14.0, diameter 0.1") is still in western Sagittarius.
THIS MONTH'S EVENTS
(Times in EDT until March 14; EST thereafter)
| March 1 | The Moon is well below Saturn this evening. |
| March 3 | The Moon is well below Spica all night |
| March 7 | This morning the Moon is 4° left of Antares. |
| Last Quarter Moon at 10:42 AM EDT. | |
| March 11 | Mars is stationary, resuming direct motion. |
| March 14 | Daylight Savings Time begins at 2 AM. Turn your clock forward one hour. |
| Mercury at superior conjunction, entering the evening sky. | |
| March 15 | New Moon at 5:01 PM EDT. |
| March 16 | A very thin crescent Moon is 7° west (right) of the Moon in the dusk. |
| March 17 | Uranus is in conjunction with the Sun. |
| Tonight the crescent Moon is about 9° above Venus. | |
| March 20 | Spring begins in the Northern Hemisphere at 1:32 PM EDT. |
| The Moon passes near the Pleiades, occulting several stars in the outer fringe of the cluster. | |
| MARCH 21 | SATURN IS AT OPPOSITION TONIGHT (SEE ABOVE). |
| March 23 | First Quarter Moon at 7:00 AM EDT. |
| March 25 | This morning the Moon is 8° west of Mars. |
| March 28 | The Moon is 9° right of Saturn. |
| March 29 | Full Moon at 10:25 PM EDT. |
| MARCH 30 | MERCURY IS BECOMING VISIBLE IN THE WESTERN SKY AT DUSK. LOOK FOR IT TONIGHT 3° BELOW RIGHT OF BRIGHT VENUS. SEE ABOVE. |
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