The sky: January 29-February 4; Center of winter

Special to, January 29, 2024

Excerpts from weekly Sky&Telescope report.


■ After dark the Great Square of Pegasus sinks low in the west, balancing on one corner. Meanwhile, the Big Dipper climbs up in the north-northeast, tipping up on its handle.

■ Algol shines at its minimum light, magnitude 3.4 instead of its usual 2.1, for a couple hours centered on 6:36 p.m. EST. Watch it rebrighten through the rest of the evening.


■ Orion is high in the southeast right after dark. Left of it is Gemini, headed up by Castor and Pollux at far left. The stick-figure Twins are still lying on their sides.

Well below their legs is bright Procyon. Standing 4° above Procyon is 3rd-magnitude Gomeisa, Beta Canis Minoris, the only other easy naked-eye star of Canis Minor. The Little Dog is seen in profile, but only his topmost outline. Procyon marks his rump, Beta CMi is the back of his neck, and two fainter stars just above that are the top of his head and his nose. Those last two are only 4th and 5th magnitude, respectively. Binoculars help with them through light pollution.


■ Have you ever closely compared the colors of Betelgeuse and Aldebaran? Can you detect any difference in their colors at all? I can’t, really. Yet Aldebaran, spectral type K5 III, is often called an “orange” giant, while Betelgeuse, spectral type M1-M2 Ia, is usually called a “red” supergiant. Their temperatures are indeed a bit different: 3,900 Kelvin and 3,600 Kelvin, respectively.

■ L0ok out a southeast window in Thursday’s early morning hours for the waning Moon. Near it, in the frigid January night, will be springtime Spica. It’s now making its early seasonal appearance in the small hours. See below.

Moon with Spice in the morning hours of Feb. 1, 2024

The Moon, nearly last quarter, shines near Spica in Thursday’s early morning hours. These scenes are drawn exact for an observer near the middle of North America; your Moon positions may differ a bit. Moreover, the Moon is drawn about three times its actual apparent size. On the morning of February 1st it will be about 1° from Spica, or about two Moon diameters.


■ Orion is now high in the south-southeast after dinnertime, looking smaller than you may remember him appearing early in the winter when he was low. You’re seeing the “Moon illusion” effect. Constellations, not just the Moon, look bigger when they’re low.


■ Jupiter is three months past its November 2nd opposition, so it’s traveling eastward again against the background stars (“direct motion,” as opposed to retrograde).

Once the night is fully dark, notice the curved line that Jupiter makes with Alpha Arietis and Alpha Trianguli to the upper right of it, as shown. That line was nearly straight at the beginning of the year, when Jupiter was at its stationary point.

Jupiter still shines at a brilliant magnitude –2.4. Alpha Arietis and Alpha Trianguli upper right of it. At magnitudes 2.0 and 3.0, they are only 1/60 and 1/150 as bright as Jupiter.

■ Last-quarter Moon (exactly so at 6:18 p.m. EST on the 2nd). The Moon rises in the east-southeast around 1 or 2 a.m. Saturday morning. It’s below Spica, and three times as far to the lower right of Arcturus.


■ Sirius the Dog Star blazes well up in the southeast by midevening. It’s the brightest star of Canis Major. In a dark sky with lots of stars visible, the constellation’s points can be connected to make a convincing dog seen in profile. He’s currently standing on his hind legs. Sirius is on his chest, to the right or lower right of his faint triangular head.


Today is the center of winter; we cross the midpoint between the December solstice and the March equinox at 10:16 a.m. EST (15:16 UT). That minute is the very bottom of the wheel of the year, astronomically speaking.

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