May graces us with another, invisible, new supermoon, and two full micromoons the latter of which will also be a (calendar) blue moon.
The Eta Aquarids meteor shower seeded by Halley’s comet also brightens the May sky.
The Sun leaves Aries (The Ram) on 14 May at 5:40 am and enters Taurus (The Bull) and recedes from Earth by 966,934 km (0.006 AU) over the month. Daylight lengthens from 15:23 (15.378 hours) on 1 May to 17:09 (17.155 hours) on 31 May so we lose 1 hour and 47 minutes of night time by the end of May. After 5 May, we never attain astronomical twilight or darker as the Sun is always above the -18 degrees boundary (so never dips below it).
The Moon begins the month in Virgo (The Maiden) and ends in Ophiuchus (The Serpent Bearer) but recedes by 6,036 km. The (first) full Flower Moon makes an appearance on 1 May at 6:23 pm in Libra (The Scales). Since the Moon is at ‘apogee syzygy’, it is a full micromoon and the Moon will appear smaller than normal. Lunar apogee (furthest from Earth) occurs on 4 May at 11:21 pm and takes the Moon to 405,816 km away from Earth—around 21,416 km further than average—subtending an angle of 29.4 arc-minutes. The Moon enters last quarter on 9 May at 10:10 pm in Capricornus (The Sea Goat). The new Moon appears on 16 May at 9:01 pm in Aries (The Ram) beginning a new synodic month which will last 29 days, 8 hours and 53 minutes. Since the Moon is at ‘perigee syzygy’ it is also a new supermoon but it cannot be seen. Lunar perigee (closest to Earth) occurs on 17 May at 2:38 pm and finds the Moon some 358,082 km away from Earth—around 26,318 km closer than average—subtending an angle of 33.4 arc-minutes.
The first quarter Moon shows up on 23 May at 12:11 pm in Leo (The Lion). Finally, there is a second full Moon which makes an appearance on 31 May at 9:45 am in Scorpius (The Scorpion). At this time, the Moon is also at ‘apogee syzygy’ so it, too, is a micromoon and, since it is the second full Moon within the same month, it is a calendar Blue Moon. It is also the smallest micromoon all year!
The Moon conjuncts with Antares in Scorpius (The Scorpion) on 4 May in the wee, small, hours.
For the inferior planets: Mercury begins the month in Pisces (The Fishes)
and ends in Taurus (The Bull) but approaches by 22,025,006 km (0.147 AU).
The ‘Swift Planet’ decreases in magnitude from -0.79 to -0.52 (1.28 times
in brightness) over the month. The distance between the Earth and Mercury
will be greatest on 13 May at a shade over 198 million km. It is lost for
observing mid-month when it reaches superior conjunction (behind the Sun).
On 18 May, Mercury reaches perihelion (closest to the Sun) at a mere 46
million km. Venus begins the month in Taurus (The Bull) and ends in Gemini
(The Twins) but approaches by 27,181,964 km (0.182 AU). Venus increases in
magnitude from -3.92 to -3.95 (1.03 times in brightness) over the month.
On 15 May, Venus reaches perihelion. The ‘Evening Star Planet’ remains
highly visible, in the west, into late evening and is well placed for
observing.
For the superior planets: Mars begins the month in Pisces (The Fishes) and
ends in Aries (The Ram) but approaches by 9,165,092 km (0.061 AU). The
‘Red Planet’ decreases in magnitude from 1.23 to 1.27 (1.04 times in
brightness) over the month. Mars remains a daytime object and inaccessible
to observers. Jupiter remains in Gemini (The Twins) all month but recedes
by 61,325,453 km (0.410 AU). The ‘Gas Giant Planet’ decreases in
magnitude from -2.01 to -1.88 (1.13 times in brightness) over the month.
The good news is that it will be the highlight of the planets visible
during May observable all evening and into the early hours every day.
Saturn begins the month in Cetus (The Sea Monster) and ends in Pisces (The
Fishes) but approaches by 53,788,304 km (0.360 AU). The ‘Ringed Planet’
increases in magnitude from 0.93 to 0.88 (1.05 times in brightness) over
the month. You may catch it during nautical twilight particularly during
the latter days of the month. Uranus remains in Taurus (The Bull) all
month but recedes by 7,613,590 km (0.051 AU). Uranus decreases in
magnitude from 5.83 to 5.83 (1.00 times in brightness) over the month.
Earth and Uranus are furthest apart on 22 May at 3 billion km. It reaches
conjunction with the Sun the same day and is lost for observation. Neptune
remains in Pisces (The Fishes) all month but approaches by 60,441,979 km
(0.404 AU). Neptune increases in magnitude from 7.81 to 7.78 (1.03 times
in brightness) over the month.
Although we witness no minor planet transits in 2026, Neptune-based
observers might be tempted to witness a transit of Mars on 5 May starting
at 3:53 pm (Earth time) and continuing until 10:36 pm (also Earth time)!
There are 2 meteor showers in the May sky for Edinburgh and Lothian. The
strong Eta Aquarids (031 ETA), radiant from Aquarius (The Water Bearer),
began last month and are active until 28 May. They peak on 6 May with up
to 50 meteors per hour. The radiant rises around 3 am on 6 May so the
shower, with a ZHR=50, will be visible for 90 minutes—the waxing gibbous
Moon illuminated to 81% notwithstanding—before sunrise spoils the show.
These are one of only 2 meteor showers seeded by the world’s most famous
comet: 1P/Halley. The very weak Eta Lyrids (145 ELY), radiant from Lyra
(The Lyre), are active between 3–14 May and peak on 11 May with barely 3
meteors per hour. This shower is associated with comet C/1983 H1
IRAS-Araki-Alcock. They are hard to see but the waning crescent Moon is
only illuminated to 34% and does not rise until 3:30 am giving a few
hours of observing. They will be radiant from an area between Vega and
Deneb: two of the bright stars in the ‘Summer Triangle’.
At the time of our sky map, some constellations visible are Ursa Major
(The Greater Bear) at zenith, Cepheus (The King) in the north, Hercules
(Hercules) in the east, Gemini (The Twins) in the west, and Corvus (The
Crow) in the south. The ecliptic hosts Ophiuchus (The Serpent Bearer),
Libra (The Scales), Virgo (The Maiden), Leo (The Lion), Cancer (the Crab),
Gemini (The Twins) and Taurus (The Bull).
If you wish to have a late night, around midnight mid-month, try seeking
out some prominent Messier objects visible on our sky map. These will need
a telescope or binoculars but M82 (Cigar Galaxy), M101 (Pinwheel Galaxy)
and M51 (Whirlpool Galaxy) will all be close to zenith and M87 (Virgo A),
in the south, will be at a reasonable airmass. M44 (Beehive Cluster also
known as Praesepe) and M67 (Golden Eye Cluster) will be in the west.
We also see 2 bright star triangles in the May sky. The ‘Spring Triangle’
of Arcturus in Bootes (The Herdsman), Denebola in Leo (The Lion) and
Spica in Virgo (The Maiden) is south-east. The ‘Summer Triangle’—Deneb
in Cygnus (The Swan), Vega in Lyra (The Lyre) and Altair in Aquila (The
Eagle)—rises in the east after midnight. Circumpolar
constellations—always above the horizon at the latitude of Edinburgh and
Lothian—include Draco (The Dragon), Perseus (The Hero), Cassiopeia (The
Seated Queen) and Camelopardalis (The Giraffe).
The sky above Edinburgh and Lothian at 11 pm on 1 May, 10 pm on 15 May and 9 pm on 30 May. The green, dashed, line is the Ecliptic and the brown, dashed, line is the Milky Way. Asterisms below 10° may be truncated because of distortion. To use the map, face any direction and then rotate the map until that cardinal point is nearest to you. The zenith (point directly overhead) is at the center of the circle and the edge is the horizon.
