Shorter nights, but plenty to see

The Sky Guy

Posted: Sunday, April 06, 2008



Days are getting longer and nights are getting shorter. We're also leaving the freezing cold behind. As we all love winter's benefits, we surely regret that our beloved starry skies will take a back seat soon.

But at least we get some nice views for a good-bye. With Daylight Savings Time having started early last month, it doesn't get dark until 10 p.m. or even later, and therefore the diagram shows the western sky around 11:30 p.m. toward the end of April. This late in the season, many of the brilliant stars of winter are either gone or hard to detect. Therefore, look early in the month in the west for Sirius and Orion with Betelgeuse and Rigel, Aldebaran and the Pleiades. Still visible all month are the twins Castor and Pollux in the middle of the diagram, Procyon below and left of middle, Capella in its pentagon of Auriga on the right.

But look out especially for Mars which has now moved toward the left (east) of these bright stars; around May 5 (Cinquo de Mayo, Korean Children's Day) it exhibits a perfect straight line with Gemini's Castor and Pollux.

Having shifted from east to west throughout late winter are Leo with Regulus and Saturn nearby. The latter is actually of virtually the same brightness as those bright stars I described and thus blends in pretty good, showing an acute triangle with Regulus and Algeiba in the lion's mane.

Saturn looks great in binoculars and in telescopes of all sizes. Take a peek and see the southern side of the rings for the last time since the mid-1990s; next year the rings will be edge-on, i.e. sometimes appear invisible, then the northern side will open up the following year, lasting for half of Saturn's orbit until the mid-2020s. This effect happens because Saturn's rings are tilted by 20 degrees with respect to its orbit and next year Saturn appears in the part of its orbit where they're edge-on.

Mercury can be barely glimpsed after sunset in late April and early May, also see diagram.

The other planets are not viewable for various reasons: Venus is on its way toward superior conjunction, i.e., on the other side of the sun; Jupiter resides in Sagittarius, which is a pretty constellation but too low when viewed in Alaska (Jupiter may appear very low near the southern horizon during dawn); Uranus and Neptune are too close to the sun they may be viewed again in early fall.

The crescent moon appears just left of the Pleiades on April 8 (the East Coast sees the moon occulting the Seven Sisters). On April 11 the half moon sits right on top of Mars, and this should be interesting to watch throughout the evening and night: first it will be pretty, second, by viewing the moon during daylight, one might be able to glimpse Mars with binoculars to its lower left, and third, the moon's west-to-east motion becomes apparent when it glides to Mars' left throughout the night.

On April 14, the now gibbous moon joins Saturn and Regulus; on April 18 the full moon is near the bright star Spica in Virgo; on April 27 the half moon sits very low on the southern horizon during dawn with Jupiter right above it.

In the east, find Arcturus by following the Big Dipper's handle. In the northeast Vega, Deneb and Altair are becoming more prominent. They can be seen all summer during the few hours of semi-darkness and are aptly named the Summer Triangle.

Andy Veh is a professor of math and physics at Kenai Peninsula College.

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