In twilight, look west well below Venus for a very thin waxing crescent Moon close to Mars, as shown here. The Moon is just one day old following yesterday’s solar eclipse. We see the Moon’s night side (dimly Earthlit), and just a little of the sunlit side around the edge, because the Moon is nearly along our line of sight to the Sun. Faraway Mars shows us mostly its day side, because it’s nearly on the same line of sight on the far side of the Sun. Tomorrow evening the Moon will be beautifully paired with Venus; make a note to look.
The Sun undergoes a total eclipse for parts of the North Atlantic and Arctic Oceans. The partial phases sweep across a much larger area: all of Europe, North Africa, and central Asia. Maps and explanations (particularly for the UK). More maps and detailed local timetables are at Fred Espenak’s EclipseWise site.
As dusk turns to night, spot Venus still in the west. To its upper right by about a fist at arm’s length, look for 2.0-magnitude Hamal, the brightest star of Aries. Farther to Venus’s upper left or left, look for 2.5-magnitude Menkar, Alpha Ceti. Spring begins in the Northern Hemisphere at the equinox, 6:45 p.m. EDT (3:45 p.m. PDT). This is when the Sun crosses the equator heading north for the season.
The word “equinox” comes from night and day supposedly being equal on this date, but that’s just wrong. It would be true if Earth had no atmosphere and the Sun were a point rather than a disk. But with an atmosphere, daylight continues long after the moment of sunset. Second, sunrise and sunset are counted not from when the Sun’s center is on the true horizon, but when its top edge is on the horizon; this adds a couple minutes to daytime. And third, atmospheric refraction at the horizon elevates the Sun by about its own apparent diameter, adding a few more minutes to official daytime.
Jupiter this season forms a big, temporary quadrilateral with Procyon well to its right at dusk, Regulus a little less far to Jupiter’s lower left, and fainter Alphard, the orange heart of Hydra, far below Jupiter.
The Big Dipper glitters high in the northeast these evenings, standing on its handle. You probably know that the two stars forming the front of the Dipper’s bowl (currently on top) are the Pointers; they point to Polaris, currently to their left or lower left. And, you may know that if you follow the curve of the Dipper’s handle out and around by a little more than a Dipper length, you’ll arc to Arcturus, which is now rising in the east-northeast. But did you know that if you follow the Pointers backward the opposite way, you’ll land in Leo? Draw a line diagonally across the Dipper’s bowl from where the handle is attached, continue far on, and you’ll get to Gemini. And look at the two stars forming the open top of the Dipper’s bowl. Follow this line past the bowl’s lip far across the sky, and you crash into Capella.
Jupiter this month forms a big, more-or-less equilateral triangle with Procyon and Pollux. Face southeast after dark, and Procyon is to Jupiter’s lower right. Pollux is to Jupiter’s upper right. Procyon is also part of the slightly larger Winter Triangle, down to Procyon’s lower right. The Winter Triangle too is equilateral. Its other stars are orange Betelgeuse in Orion and bright Sirius below.
The brightest point of light at dusk is Venus in the west. Second-brightest is Jupiter, much higher in the east-southeast. Look to the right of Jupiter by two or three fists at arm’s length for Procyon. Look the same distance lower right of Procyon and there’s the evening’s third-brightest point, Sirius.
Have another look for Comet Lovejoy! This evening it’s just a fraction of a degree from Delta Cassiopeiae, the second-dimmest star of Cassiopeia’s W pattern. The comet is still 6th magnitude and fading more slowly than predicted. Nor is there bothersome moonlight in the evening sky. See Bob King’s Catch Comet Lovejoy in Cassiopeia with a quickie naked-eye chart to find the right star in Cassiopeia, or Comet Lovejoy Shines On with a finder chart for every evening in March. You’ll need good binoculars or a low-power telescope. Plan to go out right after dark, when Cassiopeia is still high.
On the traditional divide between the winter and spring sky is dim Cancer, marked this year by Jupiter. Wintry Gemini is to its west, and Leo of spring is to its east. Don’t be too distracted by Jupiter; Cancer also hosts the Beehive Star Cluster, M44, in its middle. Look for it 6° to Jupiter’s upper right after dark. That’s about the width of a binocular’s field of view.
You know the season is shifting. As the stars come out, the Big Dipper standing on its handle in the northeast is now as high as Cassiopeia standing on end in the northwest. The Dipper is rising into spring and summer, and Cas is descending from its high showing in fall and winter.
On Friday morning the 13th, the last-quarter Moon shines to the left of Saturn and the head of Scorpius before and during dawn.