You are hereTHIS MONTH'S SKY - April 2010
THIS MONTH'S SKY - April 2010
THIS MONTH'S SKY
Celestial Events -- April 2010
VENUS AND MERCURY IN THE EARLY EVENING SKY
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Venus, the most brilliant of all planets as seen from Earth, becomes easily visible in the west at dusk as April begins. Fainter Mercury is nearby and can be found from Venus using the chart at upper right. This is Mercury's best apparition of the year and will remain visible through the first half of the month, although fading at a rapid rate. This occurs even though Mercury is approaching Earth during this time. The reason it is fading is because of its phase -- we are seeing more and more of the unlit part of Mercury. So look early in the month to spot it. |
Venus and Mercury |
On April 1st Mercury has magnitude -0.9 while Venus is a brilliant -3.9. A telescope will show Mercury is about 67% lit while Venus is 94% lit. This is due to Mercury's great speed as it orbits the Sun. It will several months before Venus' phase becomes this obvious. Look a half hour after sunset. Venus will be 10° above the horizon and Mercury a little over 3° to Venus' lower right. The next few days Mercury approaches ever closer to Venus. On April 4th they are at closest, 3° apart, though Mercury is faded to magnitude -0.5 and 55% lit.
On the 8th it is at greatest elongation from the Sun. If you look at it through a telescope that evening you will see it is only 40% lit and less than 8" (arc seconds) in diameter. Its magnitude is now +0.1. In the following week Mercury is fainter and falling back towards the Sun, making it a much more difficult target.
It is worth an effort on April 15th. Only 1° away is a beautiful thin crescent Moon. Both Moon and Mercury will be difficult targets -- use Venus 7° to the upper left as a guide.
During April Venus will overwhelm everything else in the sky but the Sun and Moon. On the 24th, look for the beautiful Pleiades star cluster 3½° to Venus' upper right. Unlike Mercury, Venus will continue in the evening sky for several months. Look for a wonderful get-together of Venus, Mars, and Saturn in August.
| The planet Mars is easy to spot once the sky darkens. It lies in the faint constellation Cancer the Crab, roughly equidistant from three bright stars: Pollux in Gemini, Procyon in Canis Minor and Regulus in Leo. Note Mars' reddish color.
Mars was at opposition in late January. It has faded a good deal since then, but is still interesting to look at in a telescope, though it will be difficult to see anything besides a yellow-orange ball. We feature Mars this month because it passes very close to a lovely star cluster, the Beehive (also known as Praesepe, the Manger). In fact on the night of April 17th, Mars is only 1° above the cluster. The Beehive is bright enough to be seen from NYC with binoculars. Use Mars to help spot it.
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Location of Mars
Mars and the Beehive |
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Click to get sky charts and a description of the sky for this month.
PLANETS IN APRIL
MERCURY has its best appearance in the evening sky this year in the first half of April. It then fades quickly and falls toward the Sun, being in conjunction with it on the 28th. See above for more details.
VENUS (magnitude -3.9, diameter 10.5" to11.4", phase 95% to 89% lit) is now far enough from the Sun to be obvious. She is joined in the first part of the month by Mercury. See (above).
MARS (magnitude +0.2 to +0.7, diameter 9.2" to 7.3"), in Cancer. On the 17th it passes above the Beehive cluster. See above.
JUPITER (magnitude -2.0, to -2.1 diameter 33.5" to 35.0") is in Aquarius, though moving towards Pisces. It rises about an hour before the Sun on the first, two hours before on the last day of the month. On April 1st, the fourth-magnitude star 90 Aquarii is only 7' (arc minutes) away, masquerading as another Jovian moon.
SATURN (magnitude +0.6 to +0.8, diameter 19.5" to 19.0") is in western Virgo. At opposition last month, it is still prominent in the evening sky.
URANUS (magnitude +5.9, diameter 3.4") is in Pisces. Jupiter is moving toward Uranus; at the end of April they are 5° apart.
NEPTUNE (magnitude +7.9, diameter 2.2") is in Aquarius, like Saturn and Uranus in the morning sky.
PLUTO (magnitude +14.0, diameter 0.1") is still in western Sagittarius.
THIS MONTH'S EVENTS
(Times in EDT)
| April 3 | Antares is just below the Moon this morning, about an hour before sunrise. |
| April 4 | Mercury is closest to Venus (3°) this evening. |
| April 6 | Last Quarter Moon at 5:37 AM. |
| Pluto is stationary, beginning retrograde motion. | |
| April 8 | Venus is at greatest elongation tonight. |
| April 11 | The Moon is 5° above Jupiter this morning. |
| April 14 | New Moon at 8:29 AM. |
| April 15 | At dusk look for Mercury 7° lower right of Venus. An extremely thin Moon will be 1° right and slightly above Mercury. |
| Mars passes 1¼° above the Beehive Cluster tonight. | |
| April 15 | New Moon at 5:01 PM EDT. |
| April 16 | Tonight the Moon is about 7° above Venus and 4° below the Pleiades. |
| April 21 | First Quarter Moon at 2:20 PM. Mars is 6° above the Moon. |
| April 22 | Lyrid Meteor Shower peaks. |
| April 24 | Tonight the Pleiades is 3½° upper right of Venus. |
| April 25 | The Moon is 9° below Saturn. |
| April 28 | Full Moon at 8:18 AM. |
| Mercury is in inferior conjunction with the Sun, entering the morning sky. |
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