Skylights: May 2024

Sun

After moving through Aries for the past 25 days, the Sun enters Taurus on the 13th. On the 16th, sunsets begin occurring after 8:00pm EDT, and will remain so through August 3rd.

Moon

May begins with the Moon at last quarter in Capricornus at 7:27am EDT on the 1st.

On the 4th, the waning crescent Moon is 5.6° east of Saturn before sunrise. On the 5th, it is 3.8° east-northeast of Mars, and on the 6th, it is 3.2° north-northeast of Mercury.

New Moon is at 11:22pm EDT on the 7th, marking the beginning of Lunation 1254.

On the 8th, try to find the 21-hour, 1.0% illuminated waxing crescent Moon just after sunset. With a clear horizon, you just may be able to spot Jupiter for the final time this month 5.0° south-southwest, or nearly directly below the Moon. Once you spot the Moon with binoculars or a telescope, keep watching it as the sky darkens, and you’ll begin to see the brighter members of the Pleiades appear within 0.5° to its north.

On the 10th, while it is within 5° of the open cluster in Gemini, the 10.8% illuminated crescent Moon occults the 4.6 magnitude star 136 Tauri, a class A0 spectroscopic binary star system that is 420 light years away. Ingress behind the Moon’s darkened limb is at 10:07pm, and it reappears from the bright limb 39 minutes later.

On the following evening, the 23rd, the Moon passes 2.8° north of Vesta. It is then 2.0° south of Pollux (alpha Geminorum) on the 12th, and 2.3° north of the Beehive Cluster, M44, in Cancer, on the 13th.

First quarter Moon occurs at 7:48am on the 15th, in Leo, and is 2.7° northeast of Regulus early that evening.

The Moon occults another star, magnitude 3.6 Zavijava (beta Virginis), early on the 18th. Ingress occurs at 1:31am, and egress is at 2:34am. Zavijava is a class F9 dwarf that lies just 36 light years away.

The waxing gibbous Moon passes 2.3° northwest of Spica, in Virgo, on the 20th.

At 9:23am on the 23rd, the full Flower Moon occurs in Scorpius. During that evening, it passes just three arcminutes from Antares, with the closest appearance occurring at 9:56pm EDT.

The waning gibbous Moon is just 1.7° southeast of dwarf planet Ceres just after midnight on the 27th. 

The Moon occults a third moderately bright star on the 29th, magnitude 4.6 epsilon Capricorni. The star disappears behind the bright limb of the Moon at 3:40am, and reappears from the dark limb at 4:48am, which is within civil twilight, so the star may not be visible unless observed with a fairly large telescope.

Last quarter Moon occurs at 1:13pm EDT on the 30th, in Aquarius. The following morning, the Moon lies just 1.0° south-southeast of Saturn.

At the beginning of May, all of the planets lie within a 67.5° arc of sky, with Jupiter and Saturn marking the eastern and western endpoints, respectively. With Jupiter’s apparent motion more than double that of Saturn, the arc gradually widens throughout the month, and after the 18th, the entire set of planets will be in the morning sky.

Mercury

Mercury spends the month in the morning sky, but remains low throughout its apparition, never rising more than 50 minutes before the Sun. 

On the 6th, use the 28.5-day, 4.1% illuminated crescent Moon as a guide to find Mercury, which will be 3.2° south-southwest.

Mercury is at greatest elongation on the 9th, when it will be 26.4° west of the Sun. Mercury’s earliest rise time of this apparition is at 4:26am EDT on the 25th.

On the final morning of May, if you happen to see a very dim, bluish speck just 1.3° north of Mercury, this is the planet Uranus. Its position low on the horizon and through bright twilight makes it very difficult to see, even with the largest telescopes.

Venus

Our brightest planet, Venus, is approaching its superior conjunction early next month, and is therefore very close to the Sun and difficult to observe during all of May. It joins Jupiter (0.2° to its north) on the 23rd, but as the two planets will be just 3° from the Sun, there is no practical or safe way to observe them.

Mars

Mars season has begun, with the Red Planet rising into a dark sky, before the onset of astronomical twilight, for the first time on May 29th, but you can start observing Mars low in the east earlier in the month. On the 5th, the waning crescent Moon lies 3.8° east-southeast of Mars. 

Throughout May, Mars is brightening slowly, around magnitude 1.1, similar in brightness to Antares, in Scorpius.

The first week of May is also a good time to see Mars and Neptune together, as the distant eighth planet is within a few degrees west of Mars.

Jupiter

Jupiter, now in Taurus, is low in the west-northwest after sunset during early May. On the 1st, it sets 1 hour after sunset, but quickly drops out of view during the next few nights. It reaches conjunction in the afternoon of the 18th, and moves into the morning sky. It rises just 30 minutes before sunrise on the 31st, so we may not be able to see it until June.

Saturn

Saturn is in Aquarius, and in early May, the ringed planet rises before 4:00am EDT. At the end of the month, Saturn enters the eastern sky at 2:00am.

With Saturn rising into the sky before twilight, now is a good time to notice how much its ring plane angle has changed since January, the last time it was observable in our evening sky. The rings are tilted about 3° toward us, whereas they were at 10° at the end of January.

The waning crescent Moon joins Saturn on the 31st, appearing just 1.0° south-southeast of the planet.

Uranus

Uranus is at conjunction on the 13th and will be out of view until later next month. Our seventh planet, which has spent the past 63 months moving through Aries, enters Taurus on the 23rd; however, it will briefly retrograde back into Aries at the end of this year.

Neptune

If you have a fairly large telescope, and can point it low to the horizon, Neptune can be seen just a few degrees east of Mars early in the month. Otherwise, you may want to wait a few weeks, when the eighth planet rises higher in the sky before the onset of twilight.

Minor Planets

Asteroid 4 Vesta is moving eastward through Gemini during May, and remains at magnitude 8.3.

On the 1st, Vesta will lie just 0.3° south of Mebsuta (epsilon Geminorum). At the end of the month, having faded by just 0.1 magnitude, it will be 4.7° south-southwest of Pollux (beta Geminorum).

3 Juno has resumed prograde (eastward) motion through Leo, although it has faded beyond magnitude 10.0, beyond the limit of binoculars, unless you are in a very dark sky. It is still fairly easy to locate in the early evening sky. In early May, it is just 1.5° north-northeast of rho Leonis. During the third week of the month, watch it pass 2.5° south of the M95/M96 galaxy pair.

2 Pallas reaches opposition on May 17. Owing to its highly eccentric orbit, it is actually closest to Earth 10 days earlier, on the 7th, at 2.15 au. The 513 kilometer wide asteroid hovers around magnitude 9.0 for the duration of the month, and its highly inclined orbit, at 34°, brings it substantially north of the ecliptic.

In early May, Pallas is just 1.5° west of the small planetary nebula NGC 6210, which is about the same visual magnitude as the asteroid. On the 11th, it crosses the line between Kornephoros (beta) and zeta Herculis, about ⅓ the distance from the former. 

In mid-May, it shines at magnitude 9.0, and is moving northwestward through Hercules, about 2.7° northeast of Kornephoros  and just 1.5° west of the planetary nebula NGC 6210, which is about the same visual magnitude as the asteroid.

It crosses the border from Hercules into Corona Borealis, at declination +26°40’, on May 29.  

Dwarf planet Ceres begins retrograde motion in Sagittarius, and brightens to magnitude 8.0 in May. At the beginning of the month, it is within 1° east of chi1 Sagittarii. Its southerly declination (it descends from -24° to -26° throughout the month), and movement into a star-rich region of the sky, will make tracking it fairly challenging. The Moon is 1.7° southeast of Ceres on the 27th.

Pluto is in Capricornus and rises at about 1:45am. It is located 1.0° south of 4 Capricorni, and 8° south of Dabih (beta Capricorni). The distant dwarf planet is magnitude 14.5.

Eta Aquarids peak on the night of May 4-5. These particles from 1P/Halley tend to produce persistent trains, and originate from a point near the water jar asterism in Aquarius. The waxing crescent Moon shouldn’t interfere with observing, and the peak activity can produce 10-30 meteors per hour. 

With evening twilight now encroaching well into the 9:00pm hour, dark observing conditions only begin during the later evening hours from May through August.

At the beginning of May, we get our last views of the Pleiades and Orion in the evening sky, before they return to the morning sky later in summer. High overhead, the pointer stars of the Big Dipper, which lie on the 11th hour of right ascension, are positioned neatly on the meridian, at the 12 o’clock position relative to Polaris, the North Star. If you’re not a late-night observer, this is the best time of the year for observing the myriad of galaxies that are spread across Ursa Major, Coma Berenices, Leo and Virgo.

Venturing out on a dark, moonless night in May offers many rewarding sights for naked-eye and  binocular observers. 

Looking directly overhead, one may notice three conspicuous pairs of third and fourth magnitude stars spanning over 30° in a very shallow arc, each pair exhibiting approximately the same separation of about three Moon diameters. These six stars are physically unrelated, but are all part of the Ursa Major constellation, and represent the great bear’s paws. They are also part of an asterism of their own, called the Three Leaps of the Gazelle. 

Farther to the east, about 30° south of the arc of the Big Dipper’s handle, is a diffuse sprinkling of dim stars spread over an area just over 5° across. In a very dark sky, Bortle 4 or less, the glow of this cluster is quite distinct to the dark-adapted eye, but requires binoculars under more light-polluted skies. This is the Coma Berenices Cluster (not to be confused with the Coma Cluster of galaxies). It is also listed as the 111th entry in the Melotte catalog, and number 256 in the Collinder catalog.

From the Coma Berenices cluster, move in a line towards Mizar (zeta Ursae Majoris), the middle star in the handle of the Big Dipper. Before you reach the halfway point, you will cross a pair of stars oriented roughly perpendicular to your line to Mizar. These two stars make up the constellation Canes Venatici, the Hunting Dogs. While this is a rather underappreciated constellation, its alpha star, known as Cor Caroli, is a worthwhile double star in a small telescope, with magnitude 2.8 and 5.6 components separated by a generous 19 arcseconds, ⅓ more than that of the more well-known, nearby Mizar.

Going back to the line from Coma Berenices cluster to Mizar, just after you cross the line connecting the two stars of Canes Venatici, and about ⅓ of their separation above them, you will find an 8th magnitude smudge in your binoculars. This is M94, a nearly face-on spiral galaxy that lies about 16 million light years away. 

Back to Cor Caroli, with your binoculars, move along a line towards Arcturus (alpha Bootis). A little more than half-way, you will land on the globular cluster M3. At 34,000 light years, and still within the boundaries of Canes Venatici, this massive cluster contains a half-million stars.

Finally, continue through Arcturus, for the same distance as that traveled between it and Cor Caroli, and you will find another globular cluster, M5, in Serpens. This is one of the northern sky’s best globular clusters, rivaling Hercules’ M13 in apparent size, brightness, and resolvability. It contains over 100,000 stars, and is located at 25,000 light years.