Special to CosmicTribune.com, February 3, 2025

Excerpts from weekly Sky&Telescope report.

SUNDAY, FEBRUARY 2

■ Today is the center of winter. We cross the midpoint between the December solstice and the March equinox at 6:50 p.m. EST (23:50 UT). That minute is the very bottom of the wheel of the year, astronomically speaking.

■ On Groundhog Day evening look due east, not very high, for twinkly Regulus. Extending upper left from it is the Sickle of Leo, a backward question mark leaning leftward. It’s about a fist and a half long. “Leo announces spring,” goes an old saying. Actually, Leo showing up in the evening announces the cold, sloppy back half of winter. Come spring, Leo will already be high.

MONDAY, FEBRUARY 3

■ The biggest well-known asterism (informal star pattern) is the Winter Hexagon. It fills the sky toward the east and south these evenings.

Start with brilliant Sirius at its bottom. Going clockwise from there, march up through Procyon, Pollux and Castor, Menkalinan and Capella on high, down to Aldebaran, then to Rigel in Orion’s foot, and back to Sirius. Betelgeuse shines inside the Hexagon, off center.

TUESDAY, FEBRUARY 4

■ First-quarter Moon (exact at 3:02 a.m. EST tonight, after it sets for most of North America). At dusk the Moon shines high in the southwest, in Aries. After dark look for the two brightest stars of Aries less than a fist at arm’s length to the Moon’s right. These are Alpha and Beta Arietis, Hamal and Sheratan, magnitudes 2.0 and 2.6. Cover the Moon with your hand to reduce its glare.

Just a finger-width below Beta, can you make out Gamma Arietis (Mesarthim), mag 3.9? It’s a fine double star waiting right there for your telescope when you’re sightseeing the Moon tonight. Both components are magnitude 4.6 and white. They’re lined up almost precisely north-south, 7.4 arcseconds apart.

The pair is 165 light years away, and each star is 40 times as luminous as the Sun. They’re at least 370 a.u. apart, which is at least 12 times Neptune’s separation from the Sun. So each of them could have a planetary system undisturbed by the other. But they are very young: only about 34 million years old.

■ Jupiter reaches its stationary point (the end of its retrograde loop) and resumes its prograde (eastward) motion against the stars.

WEDNESDAY, FEBRUARY 5

■ The Moon occults the Pleiades late tonight for the western U.S. and Canada. The dark limb of the 60% sunlit waxing gibbous Moon will snap up different stars at different times depending on your location. You could just watch. . . or plan ahead:

The brightest of the Pleiades is Alcyone (Eta Tauri), magnitude 2.9. Map and timetables for its occultation.

THURSDAY, FEBRUARY 6

■ Sirius the Dog Star blazes in the southeast after dinnertime, the brightest star of Canis Major. In a dark sky where lots of stars are visible, the constellation’s points can be connected to form a convincing dog seen in profile. He’s currently standing on his hind legs, facing right. Sirius shines on his chest like a dogtag, to the right or lower right of his faint triangular head.

But through the light pollution where most of us live, only his five brightest stars are easily visible. These form the Meat Cleaver. Sirius is the cleaver’s top back corner, its blade faces right, and its short handle is down below pointing lower left.

FRIDAY, FEBRUARY 7

■ Orion is now 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 back and the top of his head. 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 through light pollution.

SATURDAY, FEBRUARY 8

■ The bright gibbous Moon shines over Mars, Pollux, and Castor at nightfall, as shown below. As evening grows late this scene rotates clockwise, so that by 10 or 11 p.m. Mars shines straight left of the Moon.

Every February, the Moon is full or nearly so when it crosses Gemini. This time Mars too says hello.

■ 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.

A complication: Betelgeuse is brighter, and to the human eye, the colors of bright objects appear, falsely, to be desaturated: looking paler (whiter) than they really are. You can get a slightly better read on the colors of bright stars by defocusing them a bit, to spread their light over a larger area of your retina.

■ Jupiter’s innermost large moon, Io, crosses the planet’s bright face from 8:33 to 10:44 p.m. EST, distantly followed by its tiny black shadow (more readily detectable) from 9:46 to 11:58 p.m. EST. Both Io and its shadow creep from celestial east to west with respect to Jupiter. Callisto shines nearby in the foreground.

SUNDAY, FEBRUARY 9

■ Tonight the bright Moon shines amid Mars, Pollux, and Castor. The scene above shows them the way they’re oriented at nightfall.

■ With a telescope, watch just a little east of Jupiter’s limb for Europa to emerge from eclipse out of Jupiter’s shadow at 6:36 p.m. EST, if the sky is dark by then at your longitude. The farther east you live the better.

After that, anyone across North America can watch for Io also to emerge from eclipse at 9:16 p.m. EST.

  Feb. 2-9: The Moon and Pleiades on the 5th, The Sky