As Jupiter sinks into the west at sunset, a smaller, nearer solar system neighbor rises in the east: Mars.
This red planet has been rising bright in the evening sky as Earth has been catching up to it on the great cosmic racetrack. On March 3, we passed between Mars and the sun, placing Mars at opposition when it rose as the sun set and was highest in the sky at midnight. Tonight it will rise more than two hours before the sun sets at 7:15 p.m. and be nearly 25 degrees (the width of two and a half fists held at arm's length) above the eastern horizon as the sky darkens.
Through the spring, it will climb higher in the sunset sky to May 12 when it will be at its highest and due south as the sun slips behind the western horizon at 8:20 p.m. Meanwhile, Saturn is also rising and brightening in the eastern evening sky. Tonight it will rise at 9:20 p.m., two hours before Venus sets in the west.
If you have low horizons, you'll have the opportunity to view three planets and visualize the plane of the solar system arcing across the sky. Saturn will be the brightest object low on the eastern horizon, but only a few degrees northeast (left) of the bright luminary of Virgo, Spica (SPIKE-uh).
Both Earth and Mars are catching up to Saturn so just as we watched Jupiter move across the sky to meet Venus through the winter, we'll be able to watch Saturn move across the sky toward Mars through the spring and summer. As Earth passes planets, they appear to move backward, westward, with respect to the stars. Both Mars and Saturn are in this retrograde motion as can be seen in the diagram showing their positions tonight and their motions through Aug. 16.
Mars will end its retrograde motion on April 15 when it will seem to pause on the line between Regulus (REGG-you-luss) and Chertan (CHUR-tun). Then it will move rapidly eastward away from Leo. On that same day, Saturn will be at opposition, rising as the sun sets and visible all night long. It will also be closest to us at a distance of 810 million miles and shine about twice as bright as nearby Spica. A view through binoculars will show both objects in the same field of view, though it will take a telescope (with a magnification around 100 for a decent view) to see Saturn's rings.
Still in retrograde motion, Saturn will close to about 5 degrees from Spica by June 26 when it will stop and begin moving eastward again. Mars will move between this pair in August as shown in the inset. Through binoculars, red-orange Mars and gold Saturn will provide a beautiful contrast with bluish-white Spica. Between now and August, the stars will continue their one-degree-per-day westward march. Though the diagram shows the motion of the planets relative to the stars, even Mars' motion is not fast enough to counter the motion of the entire sky, so it, too, will move westward, though more slowly than the stars. When it passes between Saturn and Spica, the trio will be about 25 degrees above the southwestern horizon at sunset. After this, both planets will become harder to see against the glare of dusk as Earth's motion increases their distance, leaving them on the far side of the sun. Saturn will be on the far side of the sun, in a configuration known as conjunction, on Oct. 25, but Mars' faster motion will delay its conjunction to April 17, 2013. After conjunction, planets move into the morning sky, rising before the sun instead of setting after it.
Since Earth moves faster in its orbit than the outer worlds, conjunction is actually when we round the far side of the track and begin catching up to pass them once again. Saturn will be at opposition again on April 28, 2012, but it will take us until April 8, 2014 to overtake Mars again in the endless dance of the planets.
As well as planets, we have a wonderful opportunity to view a young crescent moon since the Vernal Equinox occurred at 1:13 this morning, and the new moon will occur on Thursday at 10:38 a.m.
By Friday evening, the moon will be almost 20 degrees from the sun, 14 degrees above the horizon at sunset (7:15 p.m.) and set almost an hour and a half later (8:40 p.m.).
If you have a low western horizon, look for the thin crescent moon above due west with binoculars after about 7:30 p.m. It's easier to spot initially with binoculars and then with the unaided eye. On Saturday evening, the moon will be two-thirds of the way between the horizon and Jupiter and set at 9:40 p.m. Sunday night will give us a view of the moon just to the right (3 degrees north) of Jupiter and Monday it will be just left (2 degrees south) of Venus. While you have your binoculars out, wait for dark to view some starry sights.
The Orion nebula in the hunter's sword always provides a lovely view that will soon be lost in the glare of dusk. A Google search will provide spectacular images of this amazing star-formation region. A less known beauty is the Coma star cluster in Coma Berenices (KO-muh bear-ENN-uh-seez), the "hair of Bernice." This cluster of about 40 bright stars about 280 million light years away (about a billion miles ten to the eighteenth power) is only about 450 million years old.
On Earth at the time of its birth, a shallow sea filled with Paleozoic life forms lapped up against the low remnants of the ancestral Adirondacks, depositing the sand that would become Potsdam Sandstone.
On a clear evening, take the time to pull an Adirondack chair out of its winter home in the barn to spend a few minutes viewing and contemplating the beauty and wonder of the stars, moon and planets, including the wonderful world on which we have the privilege to live.
If you have questions about the stars, moon, planets or any other astronomical topic, please visit the Adirondack Public Observatory web site at apobservatory.org or email Aileen at firstname.lastname@example.org.