Night_skies_mar_30

Jeff Green | Mar 30, 2006

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TheNightSkies ofApril, 2006:Bright planets and anApril meteor shower

by Leo Enright

At the beginning of April, sunset locally was at about 6:30 p.m. EST, and with from Standard Time to Daylight Saving Time, that time became 7:30 p.m. EDT. By the end of the month, sunset will be slightly after 8 p.m. EDT. Of course, this change of 30 minutes in 30 days means an approximate average sunset time of one minute later each day. The time of end of evening astronomical twilight changes by more than one minute per day, going from 9:15 p.m. EDT on April 1 to about 10:15 p.m. on April 30. In the mornings our sunrise times change even more dramatically, occurring earlier each morning by an average of about two minutes per day, moving from about 6:50 a.m. EDT on the 1st to 6 a.m. on the 30th. With this information, readers may determine the times of their local sunrise, sunset, and end-of-evening-twilight for each day of the month.

On clear April evenings, even before the end of evening twilight, it is easy to notice that the bright stars of the great winter constellations (Taurus, Orion, Canis Major, and Canis Minor) are sinking low in the western sky. At the same time, the large “spring constellations” (Leo, Hydra, and Virgo) have moved up into a position of prominence in the southern and eastern sky. High in the south, and as distinctive as was Orion in the winter sky, is Leo, the Lion, with the “large backwards question mark” forming the head, mane and front paws of the huge feline and the “right-angled triangle” forming its hind-quarters. To the left of Leo, but still well up in the southeastern sky is Virgo, marked by Spica, a brilliant whitish star amid two large rectangular star patterns – a formation from which it is admittedly difficult for the modern observer, with a less active imagination, to recognize the shape of a young lady carrying a bouquet of flowers, as was “seen” be our ancient ancestors. Experienced observers, with their telescopes, often spend hours on these two constellations alone, studying the dozens, even hundreds, of very distant galaxies that lie within their borders – galaxies, each one of which has billions of stars, like our own Milky Way Galaxy. The constellation Virgo, especially, is known for its “Realm of the Galaxies”; yet not one of these galaxies, because of their incredible distances, is near enough to be seen with the naked eye.

Of the five bright planets, three may be seen in the evening sky, one dominates the dawn sky, and one may be seen for the first half of the month. Reddish Mars can be easily spotted in the evening twilight in the west above the star pattern forming the “Head of the Bull, in Taurus”. Mars is now well above the red star Aldebaran, the “Eye of the Bull” star, and in fact, between the two stars that form the “tips of the horns” above the “Head of the Bull”. From night to night it will be possible for careful observers to detect this planet’s movement – “upward” toward the two brightest stars of the constellation Gemini, Castor and Pollux. High in the southwestern evening sky, the planet Saturn is still in the constellation Cancer and about mid-way between Gemini and Leo, and binocular-users can see that it is near the famous Beehive Cluster of stars (also called M44).

Though the motion of Mars is easy to detect this month, that of Saturn is more difficult. In fact, on April 5, Saturn ends its retrograde motion (referred to in previous columns) and begins its forward, or eastward, motion. Only binocular users are likely to notice that, after April 5, it appears each evening to be getting slightly closer to M44. Bright Jupiter may be seen rising in the east after 9 p.m. in early April, and even earlier in late April. It is in the constellation Libra and well below Virgo’s bright star Spica. As with Saturn, very careful observers, especially those who use binoculars, will be able to detect Jupiter’s slow motion from night to night, by comparing its position with a nearby bright star in the constellation Libra. Jupiter’s motion is still retrograde, or westward; only in July will Jupiter do what Saturn does this month, and begin its forward, or eastward, motion across the sky. Meanwhile it is a bright and dominant beacon in the eastern night sky. Of course, the most brilliant planet of all, Venus, is still in the morning sky, rising in the east slightly less than 2 hours before sunrise. (See first paragraph for sunrise times.) It dominates the dawn sky. Users of small telescopes will notice that its disk is similar to that of a Last Quarter Moon. Mercury may be seen during the first two weeks of April by those who are fortunate enough to have a very good, unobstructed eastern horizon and look below Venus about 30 to 45 minutes before sunrise.

Several lunar conjunctions with bright planets are well worth seeing this month. On the evening of April 6, the moon is near Mars, and on April 9, it is quite near Saturn. On April 14, a “near-Full Moon” appears to the right of Jupiter. On the morning of April 24 the crescent moon is just to the right of Venus in the eastern sky – a stunning sight that definitely should not be missed. Well worth setting the alarm, just to be sure of not missing it!

Meteor observers are reminded that the April Lyrid Meteor Shower peaks on nights of April 20, 21, and 22, and though there will be some moonlight interference in the latter part of the night, a good number of bright “shooting stars” should be seen throughout those nights. Observers are encouraged to record the number of meteors seen per hour.

More information about observing the spring and summer sky is available in a book entitled The Beginner’s Observing Guide, now available at Sharbot Lake Pharmacy.