Mercury and Venus gleam in the morning sky while Saturn and Mars put on a show in the evening…
Friday, March 14
Mercury reaches greatest elongation today, when it lies 28° west of the Sun and appears about 5° high in the east-southeast 30 minutes before sunrise. The innermost planet shines at magnitude 0.1 and should appear as an inconspicuous dot to naked eyes, but it stands out through binoculars. Mercury will remain as high and as bright for the next few mornings as well. Use Venus, which shines brilliantly some 20° to Mercury’s upper right, as a guide. For Northern Hemisphere observers, this morning apparition ranks as Mercury’s worst of 2013. But from south of the equator, this is the planet’s best predawn show of the year. It rises two hours before the Sun and climbs 20° high in the east a half-hour before sunrise.
Saturday, March 15
Orion the Hunter stands out in the southwest as darkness falls this week. The conspicuous constellation appears slightly askew compared with its appearance in mid-winter’s evening sky. Now, the three-star belt is aligned parallel to the horizon while blue-white Rigel hangs directly below the belt and ruddy Betelgeuse stands directly above.
Sunday, March 16
Full Moon occurs at 1:08 p.m. EDT, but our satellite will look completely illuminated all night to skygazers across the Americas. You can find it rising in the east shortly after sunset and peaking in the south around 1:30 a.m. local daylight time. The Moon lies among the background stars of western Virgo, roughly 20° west of Mars and Spica.
Monday, March 17
Although asteroid 2 Pallas reached opposition nearly a month ago, it still glows at magnitude 7.3 and shows up easily through binoculars and small telescopes. Pallas currently lies in the northern part of Hydra, a region that appears highest in the south during late evening. To find the asteroid, first locate magnitude 3.9 Iota (ι) and magnitude 4.5 Tau2 (τ2) Hydrae (which resides 2° west of Iota). Tonight and on the next two evenings, Pallas is the brightest point of light between these two stars.
Tuesday, March 18
Look to the eastern sky after 10 p.m. local daylight time, and you’ll immediately spot the waning gibbous Moon. Our satellite forms the bottom of a stunning triangle that features Mars to the upper left and Spica to the upper right. All three will show up in a single field of view through typical binoculars. Mars shines at magnitude –1.0, some six times brighter than its starry neighbor. Take time this week to view the Red Planet through a telescope, preferably after midnight when it climbs higher in the sky. The planet’s ocher-colored disk currently spans 14″ and should show several dark surface markings in addition to its white north polar cap. Mars will reach opposition and peak visibility in early April, so now is the time to start viewing Earth’s planetary neighbor.
Wednesday, March 19
March evenings offer an excellent chance to see the zodiacal light. From the Northern Hemisphere, late winter and early spring are great times to observe this elusive glow after sunset. It appears slightly fainter than the Milky Way, so you’ll need a clear moonless sky and an observing site located far from the city. With the waning gibbous Moon now exiting the early evening sky, the rest of this month will provide prime viewing opportunities. Look for the cone-shaped glow, which has a broad base and points nearly straight up from the western horizon, after the last vestiges of twilight have faded away.
Thursday, March 20
The waning gibbous Moon rises shortly before midnight local daylight time in the company of Saturn. From the United States and Canada, the two appear about 2° (four Moon-widths) apart. Saturn remains a beautiful telescopic sight all week, though the best views come when it climbs high in the south before dawn. The ringed planet shines at magnitude 0.3 among the much fainter background stars of Libra the Balance. A telescope reveals Saturn’s 18″-diameter disk surrounded by a stunning ring system that spans 41″ and tilts 23° to our line of sight.
For those of you sick of this seemingly never-ending winter, good news: Spring officially begins today in the Northern Hemisphere. Earth’s vernal equinox occurs at 12:57 p.m. EDT, which marks the moment when the Sun crosses the celestial equator traveling north. The Sun rises due east and sets due west today. If the Sun were a point of light and Earth had no atmosphere, everyone would get 12 hours of sunlight and 12 hours of darkness. But our blanket of air and the finite size of our star make today a few minutes longer than 12 hours.
Friday, March 21
Binoculars open a world of wonders invisible to naked eyes. Did you realize you could see several galaxies without resorting to a telescope? A prime hunting ground for spring galaxies lies in northern Virgo and southern Coma Berenices, home to the nearest large galaxy cluster. One of its brightest members is M87, which glows at magnitude 8.6 at the cluster’s heart.
Saturday, March 22
Venus lies 47° west of the Sun today, its greatest elongation of the year. It rises approximately two hours before the Sun and appears brilliant in the southeast before dawn. The planet shines at magnitude –4.5 and stands about 15° above the horizon a half-hour before sunrise. When viewed through a telescope this morning, Venus’ disk spans 25″ and appears half-lit.
Sunday, March 23
The brightest point of light in the evening sky belongs to the planet Jupiter. The brilliant world shines at magnitude –2.3, nearly a magnitude brighter than the brightest star, Sirius. Jupiter lies highest in the south as darkness falls, passing nearly overhead for viewers at mid-northern latitudes. The planet resides in central Gemini, nearly 15° from that constellation’s brightest stars, Castor and Pollux. When viewed through a telescope, the giant world spans 39″ and shows stunning detail in its dynamic atmosphere. And this evening, the shadows of two Galilean moons appear as black dots on the planet’s cloud tops. Io’s shadow already shows up as darkness falls across North America. Ganymede’s shadow joins it at 10:09 p.m. EDT, and both remain on the disk until 10:32 p.m. EDT. Ganymede’s shadow lifts back into space about three hours later, at 1:26 a.m. EDT.
Last Quarter Moon arrives at 9:46 p.m. EDT. It won’t rise until around 2:30 a.m. local daylight time tomorrow morning, however, when it will appear slightly less than half-lit. The Moon spends the morning hours in the northern part of the constellation Sagittarius.