As we start British Summer Time, the Lyrid meteor shower lights up the April sky and we witness both the farthest Full Micromoon of the year and the closest New Supermoon of 2025.
- The Sun leaves Pisces (The Fishes) on 18 April at 12:40 pm and enters Aries
(The Ram) and recedes from Earth by 1,238,923 km over the month. Daylight
lengthens from 13:08 (13.140 hours) on 1 April to 15:19 (15.324 hours) on 30
April so we lose 2 hours and 11 minutes of night time by the end of April.
As we head towards the long summer days of northern climes, spare a thought for
the hapless astronomer who yearns for the dark hours when astronomical dusk
ends and astronomical dawn begins. At the start of April, this amounts to 6
hours and 15 minutes but shortens dramatically to 2 hours and 8 minutes by
month’s end!
The first quarter Moon shows up on 5 April at 3:15 am in Gemini (The Twins).
This is followed by the full Pink Moon which makes an appearance on 13 April at
1:22 am in Virgo (The Maiden). Lunar apogee (furthest from Earth) occurs on 13
April at 11:33 pm and takes the Moon to 406,287 km away from Earth—around
21,887 km further than average—subtending an angle of 29.4 arc-minutes. This
is the farthest ‘full Moon apogee syzygy’ of the year making it the smallest
full micromoon of 2025. The Moon enters last quarter on 21 April at 2:36 am in
Capricornus (The Sea Goat). Lunar perigee (closest to Earth) occurs on 27 April
at 5:12 pm and finds the Moon some 357,118 km away from Earth—around 27,282
km closer than average—subtending an angle of 33.5 arc-minutes. The new Moon
appears on 27 April at 8:31 pm in Aries (The Ram) beginning a new synodic month
which will last 29 days, 7 hours and 31 minutes. This is the closest ‘new Moon
perigee syzygy’ of the year making it the largest new supermoon of 2025.
The Moon conjuncts with several bright objects in April. The Pleiades (M45 but
also known as the ‘Seven Sisters’ star cluster) will be 0.6 degrees south of
the waxing gibbous Moon on All Fool’s Day. The full Moon also comes within
0.3 degrees of Spica in Virgo (The Maiden) in the wee hours of 13 April.
Finally, Antares in Scorpio (The Scorpion) will be 0.4 degrees north of the
waning gibbous Moon on 17 April.
For the inferior planets: Mercury remains in Pisces (The Fishes) all month but
recedes by 57,681,851 km. The ‘Swift Planet’ increases in brightness from 2.89
to 0.15 magnitudes (12.42 times in luminosity) and reaches aphelion (furthest
from the Sun) on 17 April and greatest western elongation on 21 April. On 24
April, Mercury reaches dichotomy where exactly half the surface is illuminated
by the Sun but the planet will be very low on the horizon during civil dawn.
Likewise, Venus remains in Pisces (The Fishes) all month and recedes by
24,527,795 km. Venus re-emerges as the ‘Morning Star Planet’ and increases in
brightness from -4.24 to -4.72 magnitudes (1.55 times in luminosity) throughout
April. Both Mercury and Venus reach orbital stationary points in April as shown
in the ephemeris.
For the superior planets: Mars begins the month in Gemini (The Twins) and ends
in Cancer (The Crab) whilst receding by 42,296,425 km. Mars will conjunct with
the waxing gibbous Moon on 5 April passing 2.2 degrees south. The ‘Red Planet’
decreases in brightness from 0.44 to 0.94 magnitudes (0.63 times in luminosity).
Mars reaches aphelion on 16 April and is at eastern quadrature (where the angle
between Sun, Earth and planet is exactly 90 degrees) on 21 April. Jupiter
remains in Taurus (The Bull) all month and recedes by 57,447,313 km so decreases
in brightness from -2.11 to -1.98 magnitudes (0.89 times in luminosity) over the
month.
Saturn begins the month in Aquarius (The Water Bearer) and ends in Pisces (The
Fishes) but comes closer by 37,126,048 km. This barely affects the magnitude of
1.16. On 25 April, however, the waning crescent Moon, only 7.5% illuminated,
bisects Venus and Saturn just before sunrise but Saturn will be difficult to
see. For telescopic or binocular observers: Uranus remains in Taurus (The Bull)
all month but recedes by 37,132,338 km and fades from 5.82 to 5.84 magnitudes.
Neptune remains in Pisces (The Fishes) all month but comes closer by 31,723,524
km so increases in brightness from 7.83 to 7.81 magnitudes.
Shooting star watchers may enjoy the Lyrid meteor shower between 14–30 April.
These originate in Lyra (The Lyre) and should peak 22–23 April with 18
meteors per hour. Good viewing will begin after 9:30 pm and the waning crescent
Moon should not hamper observations too much since last quarter was the
previous day. Seeded by (C/1861 G1) Thatcher’s Comet, these are the oldest
meteor showers having been observed by Chinese astronomers in 687 BCE.
Thatcher’s comet has a period of around 415 years and will not be visible in
our night sky until it returns to perihelion sometime in 2276. Meanwhile, our
vigil of the recurrent nova T CrB, in Corona Borealis (The Northern Crown),
continues as the constellation is highly visible during evening and night hours
all month.
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, Orion (The Hunter) in the west, and Crater (The Cup) in the south.
The ecliptic hosts Virgo (The Maiden), Leo (The Lion), Cancer (the Crab),
Gemini (The Twins), Taurus (The Bull) and Aries (The Ram).
April is the shoulder season where the ‘Winter Triangle’—Procyon in Canis
Minor (The Lesser Dog), Sirius in Canis Major (The Greater Dog) and Betelgeuse
in Orion (The Hunter)—sets in the west and a few hours later the ‘Summer
Triangle’—Deneb in Cygnus (The Swan), Vega in Lyra (The Lyre) and Altair in
Aquila (The Eagle)—rises in the east. Between them lies the ‘Spring Triangle’
of Arcturus in Bootes (The Herdsman), Denebola in Leo (The Lion) and Spica
in Virgo (The Maiden). 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).
Phil Daly is a former employee of the Royal Observatory Edinburgh (now UKATC) on Blackford Hill.
He has worked on the UK's overseas telescopes in Hawaii (UKIRT, JCMT) and on large telescopes
at major astronomical observatories worldwide. He is currently part of an international collaboration
searching for optical counterparts to gravity wave events using multi-messenger astronomy.
