Skylights: January 2024

The new year begins with Earth passing perihelion, the closest point in its orbit around the Sun, at 7:39pm on the 2nd, at a distance of 0.98331 au (147.101 million kilometers, 91.404 million miles, 8.178 light minutes). This is 96.713% of the aphelion distance, which occurs on July 5. The angular diameter of the Sun’s photosphere, measured on January 2, will be about 1952 arcseconds, which is 64 arcseconds larger than it appears at aphelion, a difference that is slightly larger than the apparent diameter of Venus at inferior conjunction.

Latest sunrise occurs at 7:14 am EST on the 4th.

After spending the past 23 days in Sagittarius, the Sun enters Capricornus at about 9:00am EST on the 20th.

January begins with the Moon in its waning gibbous phase, on its way to last quarter, which occurs at 10:30pm on the 3rd, in Virgo. It rises the following night as a wide crescent just 3.7° east of Spica, the brightest star in that constellation.

On the 8th, just before sunrise, the 26.7-day crescent Moon will be just 1.5° east of Antares, in Scorpius, and the globular cluster M4 will be just 0.4° below the southern cusp of the slender Moon. The three objects will present a fine view in binoculars or a wide-field telescope, with the Earthshine illuminating the dark globe of the Moon.

New Moon occurs at 6:57am on the 11th, beginning Lunation number 1250. During its waxing crescent phase, it passes 6.5° east of Saturn on the 14th, then appears just 1.0° southeast of Neptune the following night.

First quarter Moon is at 10:53pm on the 17th, in Pisces. The Moon then passes 2.8° north-northeast of Jupiter on the 18th, and 4.2° northeast of the Pleiades on the 20th.

Early on the 22nd, the waxing gibbous Moon is 1.3° south of Elnath, in Taurus, and two evenings later, it is 3.2° southeast of Pollux.

The Full Wolf Moon occurs at midday on the 25th, in Cancer. The Moon rises at 4:41pm EST, about ten minutes before sunset, making for a photogenic moonrise. Just after twilight fades, look for the open cluster M44 2.7° southwest of the Moon.

On the waning side, the Moon passes 5.2° northwest of Regulus on the morning of the 27th, and on the 29th, the 18.1-day gibbous Moon occults the 4th magnitude star Sigma Leonis. Lunar occultations of moderately bright stars are some of the most dramatic events that can be observed with simple equipment, such as binoculars or any sized telescope. Ingress behind the bright limb of the Moon occurs at 4:31am EST, and egress from the dark limb occurs at 5:43am.

Mercury undergoes a favorable morning apparition during January, reaching a maximum elongation of 23.5° west of the Sun on the 12th, in Sagittarius. Throughout the second week of January, Mercury rises over 90 minutes before the Sun, with earliest Mercuryrise occurring at 5:30am on the 8th.

On the 27th, Mercury is just 0.3° north-northwest of Mars, with the pair rising about an hour before sunrise. With the two smallest planets appearing this close in our sky, it is interesting to note that Mercury, at a distance of 1.242 au, is 1.1 au closer than Mars.

Venus, which has been present in our morning sky for the past five months, is now moving lower and closer to the Sun in January as its orbit takes it around the back side of the Sun from our view. Its gibbous globe diminishes from 14.1 arcseconds in early January to 12.3 arcseconds by the end of the month.

Venus appears relatively close to Antares during the beginning of January. On the 8th, look for both Antares and the waning crescent Moon 6.5° to Venus’ southwest.

Venus is just 0.2° south-southeast of dwarf planet Ceres on the 16th.

Mars is in Sagittarius, and rises less than an hour before the Sun. Its position low in the southeast during twilight makes it difficult to observe, but on the 27th, Mercury will be just 0.3° north-northwest of Mars, providing an opportunity to open your 2024 observations of the Red Planet.

You may notice Jupiter positioned high in the sky at the meridian (due south) just as twilight ends. The giant planet reaches quadrature (90° east of the Sun on the heliocentric grid) on the 24th.

Due to its high elevation in the evening sky, Jupiter has been providing some exceptional telescopic views during nights of steady seeing. Be sure to take advantage of this before the planet gets lower in the southwestern sky over the next few weeks.

On the 18th, the 6-day gibbous Moon visits Jupiter 2.8° to its north-northeast.

Some notable arrangements of Jupiter’s four Galilean satellites include a parallelogram of opposed moon pairs at 6:00pm on the 2nd. Then on the 6th, at an instant between 5:48 and 5:49pm, Jupiter briefly appears to have only one moon, as Io ducks behind the planet, and both Europa and Ganymede are transiting Jupiter, leaving only Callisto to Jupiter’s west. Ganymede emerges from transit just as Io is occulted.

On the 12th, at about 9:24pm, the three outermost moons form an equilateral triangle, pointing back towards Io and Jupiter.

Another single moon (Callisto) arrangement occurs from 8:07pm to 9:39pm on the 13th, with Europa and Ganymede transiting simultaneously, and Io being occulted, then eclipsed. Watch Io re-emerge from eclipse to the east at 11:07pm. This event gives demonstration to the near-maximum shadow angle of the Jovian system from our view at this time.

At about 9:00pm on the 20th, a close grouping of Europa and Ganymede to Jupiter’s east, and Io close to the west is worth watching. Then at 12:00am, the system returns to the one-moon arrangement, with Io eclipsed and Europa and Ganymede in transit, leaving only Callisto to the west. The arrangement persists until Europa re-emerges from transit 28 minutes later.

Finally, at about 11:00pm on the 27th, all four moons are visible in a close-in arrangement: Ganymede and Europa to the east, Io and Callisto to the west, all within two Jupiter diameters from the planet.

Saturn, which has been in our evening sky since June, is now low in the southwest after twilight. At the beginning of the month, Saturn sets just after 8:30pm, and by the end of the month, it is out of view by 7:00pm, making January our last time to get a good view of the ringed planet.

As such, be sure to take note of the angle of its ring tilt, take a photo if you can, and compare it to the view when Saturn emerges from morning twilight in May. In mid-January, the ring plane tilt is 10.5°, and in mid-May, it will narrow to just 3.2°. Our next ring plane crossing, when the angle will be 0°, occurs on March 24, 2025, when Saturn will unfortunately not be visible during the dark hours. Our best view will be in late November 2025, when the tilt will be less than -0.5°. 

Uranus continues to be in a favorable position for viewing throughout the evening. High in the south, in Aries, it is located about halfway between Jupiter and the Pleiades, and just 3° south-southwest of magnitude 4.4 Botein (delta Arietis). You may not notice Uranus’ movement with respect to the stars, as it reaches its stationary point on the 27th, ending its retrograde motion and resuming prograde (eastward) motion thereafter.

While you’re exploring the winter sky with your binoculars or telescope, be sure to make a stop at Uranus.

The 8.6-day gibbous Moon appears 3.5° to the northeast of Uranus on the 19th.

Neptune, following Saturn, is also in the southwest just after dark. As it’s a bit higher in the sky, we still have a few more weeks to view it.

Drawing a line between iota and lambda Piscium, on the eastern side of the Circlet asterism,  takes you directly to our most distant planet. 

Pluto departs Sagittarius for the final time on the 3rd. It will now reside in Capricornus until 2038. It will not cross the border back into Sagittarius again until 2255.

Pluto is in conjunction on the 21st, and will not be visible again until April, when it is sufficiently high enough in the southeastern sky before morning twilight.

Our closest dwarf planet, Ceres, is visible low in the southeastern sky before sunrise, in Ophiuchus. Its dim light, shining at magnitude 9.0, will require a telescope to view, especially given how low it is in the sky. A great opportunity to locate it comes on the morning of the 16th, when it appears just 0.2° north-northwest of brilliant Venus. Ceres, at a distance of 3.354 au, is about 2.8 times farther away from us than Venus.

Of all the small solar system bodies visible in the sky this month, asteroid 4 Vesta is by far the brightest and easiest to locate. It remains brighter than magnitude 7.0 through most of January, and it can be found within the same binocular field of view as Tianguan (zeta Tauri), and the Crab Nebula (M1). It passes just north of Tianguan, and on the 8th-9th, it is only 0.1° away.

Asteroid 3 Juno, at magnitude 9.3, located in far southern Leo, is moving west-northwestward. It is in a fairly nondescript region of sky, but if you can locate magnitude phi Leonis, it is within 3° north-northeast of this star for much of the month.

Asteroid 2 Pallas, at magnitude 9.6, is a little easier to locate. On the 2nd, it passes just 1.0° south of the large and bright globular M5, in Serpens. From there it moves eastward, roughly towards epsilon Serpentis, passing 1.7° south of the magnitude 3.7 star on the 22nd.

The Quadrantids meteor shower peaks on the morning of the 4th. This can be quite a productive shower, with the radiant located in northern Bootes, which is nearly circumpolar. The name Quadrantids derives from the obsolete constellation Quadrans Muralis, the wall quadrant. The waning crescent Moon, located near Spica during peak morning, rises around 1:00am, and will produce moderate sky brightening for the expected peak at 4:00am.

January’s long, cold nights are gradually getting shorter, and offer, for the first time of the season, winter’s sky treasures to early evening observers. Hovering in the southeast as twilight fades is the entirety of the Winter Hexagon and its component constellations Auriga, Taurus, Orion, Canis Major, Canis Minor, and Gemini, and includes adjacent constellations Eridanus, Lepus, Puppis, and Monoceros.

It is worth the effort to bundle up and venture out to a place with a reasonably dark sky on a moonless January night to gaze into the winter Milky Way. Its gossamer glow, much dimmer than its summer component, contains a plethora of nebulae, star clusters, double stars and asterisms that are readily accessible in binoculars and small telescopes.

There is quite a lot to explore with any sized telescope just in Orion’s sword, home to the well-known Great Orion Nebula. The sword consists of four distinct and optically equidistant stellar clumps aligned in an almost perfect north-south orientation that is just under two degrees in length. The northern segment consists of the star cluster NGC 1981, a loose cluster with about a dozen stars between 6th and 8th magnitude that lies about 1,250 light years away. 

Just to the south is a complex of nebulae comprising NGC 1973, NGC 1975, and NGC 1977. Often referred to as the Running Man Nebula, its namesake shape may take some imagination to bring out, but small telescopes under a moderately dark sky do reveal the nebulous glow embedded within the object's most distinct feature, a shallow arc of three comparatively bright stars that extends in a roughly east-west orientation and is about four arcminutes long. The nebula complex is about 1,500 light years distant, slightly more distant than the Great Orion Nebula, which lies immediately to its south.

Visible without optical aid even from moderately light polluted skies like those above Seagrave Observatory, the Great Orion Nebula is perhaps the most frequently observed object in the Messier catalog, but lesser known is that it is listed as two separate objects, M42 and M43. While the nebula is the same object, the dark band separating the comma-shaped M43 to the north from the much larger fan-shaped M42 to the south gave the appearance to Messier and his contemporary astronomers that they were two distinct nebulae.

The Orion Nebula is a massive star forming region about 1,300 light years from Earth, and is a fascinating target for exploration in anything from binoculars to the Webb Telescope. The core of the Orion Nebula, known as the Trapezium for its four brightest stars in a tight group, is visible in any backyard telescope. While there are many hundreds more stars being formed within the Orion Nebula, most of our small telescopes are unable to resolve many of them. However, one of the most famous discoveries made with the Hubble telescope was the direct detection of protoplanetary disks embedded within the nebula. More recently, the Webb Telescope detected Jupiter-mass rogue planets (planets not associated with a host star) in binary pairs floating in the nebula.

Exploring a bit south of the Orion Nebula, we come across the fourth, and last, stop in Orion’s sword. This one is more sparsely populated, but contains the only star in this region with an IAU-designated proper name–Hatysa (iota Orionis). This star may not draw as much attention as the beautiful nebula to the north, but at magnitude 2.8, it is the brightest star in Orion’s sword, and at a distance of over 1,300 light years, it is a very massive and luminous star with about 15 solar masses and over 14,000 times the luminosity. It is part of the cluster with nebulosity cataloged as NGC 1980, containing s smattering of fainter stars spread across an area about half the width of M42.

After you’ve explored Orion’s sword for a while, move to the north and spend a few minutes exploring the area around Orion’s belt. While this area doesn’t contain as many distinct clusters, and its nebulous regions are quite a bit dimmer, the rich starfields of central Orion against an inky black sky is one of the more underrated sights to see in the winter sky.

A Look Ahead: 2024 at a Glance

Of the many events we have to look forward to in 2024, the most notable is the total solar eclipse of April 8, of which Rhode Island will experience a deep, 92% partial from 2:15pm to 4:38pm, with maximum eclipse occurring at 3:29pm.

We also have a partial lunar eclipse on September 17-18, but with only a small notch of the Moon’s northern limb being under the umbral shadow.

There are several occultations by the Moon worth watching in 2024. Spica is occulted on July 19 and November 27. Neptune is occulted on September 18 and again on November 11, and the Pleiades on November 16. There is also a daytime occultation of Venus by the Moon on April 7, the day preceding the eclipse.

The Moon occults the Pleiades on November 16. Although this is one of several passages of our nearest celestial neighbor across one of the most prominent star clusters in the sky, the remaining ones take place either during daylight hours, or when the Moon is still below the horizon. This does not detract from the beauty of seeing our Moon close to the sparkling star cluster. Look for these on January 20 (71.9% gibbous), February 16 (first quarter), March 14 (28.5% crescent), April 11 (13.8% crescent), May 8 (1.0% crescent), July 2 (14.8% crescent), July 30 (27.0% crescent), August 25 (last quarter), September 22 (75.6%), October 19 (90.7% gibbous), and December 13 (97.3% gibbous).

In addition, the Moon makes some rather close pairings with planets. On August 5, the 0.0% crescent Moon is 2.3° from Venus. On the 20th of August, the gibbous Moon is 0.3° from Saturn. The Moon appears even closer to Saturn, 0.1°, on November 10. And on December 18, it is 0.1° from Mars.

For planet-watching in 2024, Mercury has favorable evening apparitions in March and July, and good morning appearances in January and September.

Venus reaches its inferior conjunction on June 5, followed by a less than optimal evening apparition, during which it doesn’t appear very high in the sky until the final weeks of the year.

2024 marks a relatively infrequent second consecutive calendar year without a Mars opposition, as the next one occurs in January 2025. The last two consecutive years without one were 1991-2, and the next pair will be 2038-9. However, even though we don’t get to see a Mars opposition this year, that it occurs early next year means that the final months of 2024 will offer favorable opportunities for observing Mars. The Red Planet reaches quadrature on October 14, after which we’ll be able to observe it before midnight.

The outer planets all reach opposition during the final third of the year, with Saturn and Neptune in September, Uranus in November, and Jupiter in December.

Lastly, among celestial events that can be highly unpredictable, comet 12P/Pons-Brooks is at perihelion in April. Although with comets, we never know what to expect, it is possible that this one may become naked-eye visible early in the month. Keep watching the skies.