Skylights: March 2023

March begins with a conjunction of the two brightest planets, Venus and Jupiter, in the western sky after sunset on the 1st. In one of the more spectacular sights in the sky, Venus will be just 0.5° (the width of the Moon) northwest of Jupiter. 

As the month progresses, Venus moves higher above the western horizon as Jupiter loses its race against encroaching twilight, though it will remain visible until the end of the month.

Be sure to direct your gaze towards Venus on the 30th, when it will be 1.2° north of Uranus. If you haven’t observed Uranus recently (or at all), this is a great opportunity to find it.

Mercury passes superior conjunction on the 17th, and returns to the evening sky. On the 27th, Jupiter will be just 1.3° southeast of Mercury. By the end of the month, Mercury will set over an hour after the Sun.

In early March, the Moon passes some notable objects in the winter sky along its way to Full Worm Moon on the 7th. On the 2nd, it is 1.7° south of Pollux in Gemini; on the 4th, it passes 2.6° south of M44 in Cancer, and on the 5th, it appears 3.6° north of Regulus, in Leo.

On the waning side, the Moon is 2.6° north of Spica on the morning of the 10th, and 3.5° east of Antares on the 14th. Last quarter occurs late on the 14th.

The Moon is new on the 21st, and returns to the evening sky. The waxing crescent appears 0.7° east of Jupiter on the 22nd, 0.9° north of Uranus on the 24th, and 1.7° south of the Pleiades, in Taurus, on the 25th, followed by first quarter, on the 28th.

Closing out the month, the waxing gibbous is 2.7° southwest of Pollux on the 30th, and 4.2° northwest of the open cluster M44, in Cancer, on the 31st.

Mars remains high in the southwest after dark, and continues moving eastward through the Winter Hexagon. It has dimmed somewhat since its peak brightness in early December, but is still bright enough to change the appearance of the departing season’s largest and most familiar asterism on a nightly basis. At mid-month, it passes near Alnath, in Taurus, and forming a “parallel pair” with Castor and Pollux in Gemini. On the 20th, Mars forms an equilateral triangle with the two bright red stars, Betelgeuse and Aldebaran. On the 22nd, Mars crosses the north-south axis, the line connecting Capella and Sirius, and moves into the eastern half of the hexagon. On the 23rd, it lies in a line with Aldebaran and Castor.

Mars reaches its eastern quadrature (90° from the Sun) on the 16th, and after being a long-time resident of Taurus over the past few months, it finally enters Gemini on the 24th. At the end of the month it appears near the open cluster M35, passing just 1.2° north of the cluster on the 29th.

What other interesting alignments do you notice as you follow Mars on its nightly march through the Winter Hexagon?

When Mars begins to pass out of view, the next planetary body that becomes visible is our closest and brightest dwarf planet Ceres. Ceres resides in an area of the sky that often gets extra scrutiny this time of year, due to the prevalence of galaxies in the Messier catalog, which gets perused by deep sky observers in mid-March on the annual quest known as the Messier Marathon. More on that later.

Ceres never quite reaches naked-eye visibility, but when it is its closest to Earth, which occurs on the night of March 20-21, it can be seen in binoculars from a dark, moonless sky at just a bit brighter than magnitude 7. At opposition, Ceres is 1.6 AU from Earth, which is slightly closer than the maximum distance Venus and Earth can be, when the former is at superior conjunction. Although Ceres is considered to be a large object (it is the largest object in the asteroid belt), its 950 kilometer globe is hardly noticeable from a starlike point in even the largest telescopes. It gets as large as 0.83 arcseconds.

Saturn, which passed conjunction last month, is in Aquarius, visible low in the east-southeast before sunrise during the second half of March. On the 19th, the waning crescent Moon passes 5.6° to its south.

Neptune is in conjunction on the 15th, and is not visible in March.

The annual shift to Daylight Saving Time occurs on the 12th. From 2:00am on that date, through November 5, Eastern Time will shift ahead one hour to four hours behind Coordinated Universal Time. This brings our first sunset in the 7pm hour to the 23rd.

The Sun crosses the border from Aquarius into Pisces on the 12th. Equinox occurs at 5:24pm EDT on the 20th, when the Sun crosses the celestial equator, and its declination then becomes positive. This brings in the season of spring for the northern hemisphere, and results in fewer hours of darkness than daylight.

Also, as a bit of astronomical coordinate trivia, a portion of the Sun’s disk crosses into the non-zodiac constellation Cetus, the whale, for a few hours on the 28th. 

Dwarf planet Makemake reaches opposition in Coma Berenices on the 29th. At a distance of 51.7 AU, it shines at a meager 17.1 magnitude. Although this would require a very large telescope to observe visually, it can be detected with a modest telescope and imaging camera.

Finally, for deep-sky observers, March is the time of the year to embark on the annual Messier Marathon, an observing event when all 110 objects in Messier’s catalog can be seen over the course of a single night due to the position of the Sun during the third week of March being in an area mostly devoid of the Messier objects. It’s a bit of a challenge to observe the entire catalog, as it requires exceptionally clear weather and unobstructed horizons, as some of the objects must be viewed in twilight. 

The best time to conduct a Messier Marathon in 2023 is around March 23-25. The challenge begins with spotting the first two galaxies, M74 in Pisces and M77 in Cetus, while they are still in twilight and before they set. The crescent Moon should not interfere with early observing. The very last object in the challenge, globular cluster M30 in Capricornus, can be a bit tricky to pick up very low in the southeast during brightening twilight. Delaying your Messier Marathon by a few days makes this easier, but also makes the first objects more difficult, as they set earlier, and the Moon becomes brighter.

The best aspects of Messier Marathoning is when it is undertaken as a group activity, sharing views through different telescopes, and exploring parts of the sky you’d likely seldom visit. You can also keep a log of your observations and compete against your own best record. How many Messier objects have you seen during one night?