Your daily digest of celestial events coming soon to a sky near you.
Friday, December 25
Santa likely won’t need Rudolph’s help this year, not with a Full Moon sharing the sky over Christmas Eve and morning. Our satellite officially reaches Full phase at 6:11 a.m. EST, but it looks completely illuminated all night — and nearly so this evening. You can find it rising in the east around sunset and peaking high in the south close to midnight. The Moon passes from eastern Taurus into northern Orion during the course of the long winter’s night. This is the first Full Moon to occur on Christmas Day since 1977; another one won’t arrive until 2034.
Saturday, December 26
The brightest star in the sky (after the Sun, of course) puts on quite a show during December evenings. Gleaming at magnitude –1.5, Sirius shines nearly four times brighter than the next brightest star visible from mid-northern latitudes — Arcturus in the constellation Boötes. Sirius currently rises by 7:30 p.m. local time and ascends in the southeast throughout the evening hours.
Sunday, December 27
For those who recently caught the observing bug, the so-called Summer Triangle must seem like a huge misnomer. That’s because this asterism remains on view after darkness falls even in late December. Look for Vega, the fifth-brightest star in the sky and the brightest triangle member, low in the northwest. Deneb lies above Vega and nearly halfway to the zenith. Altair, the third triangle member, lows low in the west and sets just before 8 p.m. local time.
Monday, December 28
Mercury reaches the peak of its current evening apparition today as it arrives at greatest elongation. The innermost planet lies 20° east of the Sun and, for observers at mid-northern latitudes, stands 9° high in the southwest 30 minutes after sunset. Mercury shines at magnitude –0.6, so you should be able to pick it out easily through binoculars. Once you find it with optical aid, try to spot it with just your naked eye. When viewed through a telescope, the inner world spans 7" and appears about 60 percent lit
Tuesday, December 29
Although Saturn passed on the opposite side of the Sun from Earth exactly one month ago, it already appears noticeable in the southeast as morning twilight commences. Shining at magnitude 0.5, the planet stands out some 10° above the horizon an hour before sunrise. Target it through a telescope and you’ll see a 15"-diameter disk surrounded by a ring system that spans 35" and tilts 26° to our line of sight.
Wednesday, December 30
Two of the finest deep-sky objects shine prominently on evenings in late December. The Pleiades and Hyades star clusters climb highest in the south during midevening but remain conspicuous nearly the whole night. The Pleiades, also known at the Seven Sisters and M45, appears like a small dipper to naked eyes. The larger Hyades forms the V-shaped head of Taurus the Bull. Although both look nice with naked eyes, binoculars show them best.
Thursday, December 31
The waning gibbous Moon lies near Jupiter this morning. The two rose shortly before midnight yesterday evening but stand out much better as they climb higher during the predawn hours. Although the nearby Moon detracts from the planet’s appearance through a telescope today, consider training your scope on the magnitude –2.2 gas giant world any other morning. Jupiter currently spans 39" and displays at least two parallel dark belts in its dynamic atmosphere.
Friday, January 1
Comet Catalina (C/2013 US10) has brightened to 6th magnitude and appears nice through binoculars and telescopes for those up before the Sun. This morning, the comet passes within 0.5° of magnitude 0.0 Arcturus, the sky’s fourth-brightest star. (Can you see the fuzzy comet in the glare of this sun?) The pair rises shortly after midnight and climbs high in the southeast by the time twilight begins. Catalina doesn’t stick around Arcturus for long, however — it sails northward at better than 2° per day for the next few weeks.
Saturday, January 2
Last Quarter Moon occurs at 12:30 a.m. EST (9:30 p.m. PST on January 1). You will see it poking above the eastern horizon shortly after midnight local time and peaking high in the south as twilight starts to paint the sky. The half-lit Moon spends the morning hours in the constellation Virgo the Maiden, roughly 10° from that constellation’s luminary, 1st-magnitude Spica. If the Moon looks a bit smaller than normal this morning, it may not be your imagination. Our satellite reaches apogee, the farthest point in its orbit around Earth, at 6:53 a.m. EST. It then lies 251,206 miles (404,277 kilometers) from Earth’s center.
Earth reaches perihelion, the closest point to the Sun during its year-long orbit, at 6 p.m. EST. The two then lie 91.4 million miles (147.1 million kilometers) apart. It surprises many people to learn that Earth comes closest to the Sun in the dead of winter, but the cold weather in the Northern Hemisphere at this time of year arises because the Sun lies low in the sky.
Sunday, January 3
The waning crescent Moon passes just above Mars in this morning’s sky. The two objects form an isosceles triangle with 1st-magnitude Spica. Our satellite, which appears nearly 40 percent lit, stands 5° from each of its neighbors. The planet and star shine with almost equal intensity — Mars glows at magnitude 1.2 and Spica appears 0.2 magnitude brighter. But you’ll surely notice the beautiful color contrast between the ruddy planet and blue-white star.
Monday, January 4
The Quadrantid meteor shower reaches its peak this morning. And, with the waning crescent Moon offering only minor interference, observers with clear weather will have excellent viewing conditions. From a dark-sky site, viewers can expect to see up to 120 meteors per hour — an average of two per minute. The meteors appear to radiate from a spot in the northern part of the constellation Boötes. This region climbs high in the northeast as dawn approaches, which makes the hours after midnight the best for viewing
Tuesday, January 5
Although Venus entered Scorpius on New Year’s Day, the Scorpion couldn’t hang on to its prey for long. The planet leaves the constellation today, entering adjacent Ophiuchus the Serpent-bearer. Venus shines at magnitude –4.0, which makes it by far the brightest point of light in the sky. If you point a telescope at the world, you’ll see a 14"-diameter disk that appears about three-quarters illuminated.
The dwarf planet Pluto is in conjunction with the Sun at 10 p.m. EST. The distant world then lies on the far side of the Sun from our perspective and can’t be seen.
Wednesday, January 6
The waning crescent Moon continues its march across the morning sky, parking itself just above Venus and Saturn in the southeast before dawn. Our satellite lies 7° above Venus with Saturn 3° to the lower left of its sister planet. As a bonus, look for the 1st-magnitude star Antares below the group. Venus passes 6° due north of Scorpius’ brightest star today.
Thursday, January 7
Although people in the Northern Hemisphere experienced the shortest day of the year more than two weeks ago (at the winter solstice December 21), the Sun has continued to rise slightly later with each passing day. That trend stops this morning for those at 35° north latitude. Tomorrow’s sunrise will arrive less than a second earlier than today’s. This turnover point depends on latitude. If you live farther north, the switch occurred a few days ago; closer to the equator, the change won’t happen until later in January.
Friday, January 8
With the New Year recently begun and winter tightening its grip across much of the Northern Hemisphere, one of the most familiar constellations takes center stage. Orion the Hunter appears conspicuous in the eastern sky as twilight fades and grows even more prominent after darkness settles in. The star group climbs highest in the south around 10 p.m. local time, when it stands more than halfway to the zenith from mid-northern latitudes.
Saturday, January 9
Venus’ rapid eastward motion brings it to Saturn’s doorstep this morning. The two bright planets appear closer to each other than at any time in a decade. Western Europeans have the best view, with the two worlds passing just 5' apart at 4h UT. By the time the pair rises in eastern North America, 17' separate the two, and the gap grows to 25' on the West Coast. Still, both objects will appear in a single field of view through a telescope at low power.
New Moon occurs at 8:31 p.m. EST. At its new phase, the Moon crosses the sky with the Sun and so remains hidden in our star’s glare.
Sunday, January 10
Starting this evening and running into tomorrow morning, you can watch through a telescope as three of Jupiter’s four Galilean satellites pass directly in front of (transit) the planet. Europa gets things rolling at 11:37 p.m. EST with a transit that lasts until 2:21 a.m. Less than an hour later, at 3:04 a.m., Callisto begins to cross Jupiter’s north polar region. More than halfway through Callisto’s two-hour transit, at 4:22 a.m., Io’s shadow falls on the planet’s cloud tops. Io itself starts to transit at 5:27 a.m