Sky & Telescope - April 2025 - 50

APRIL 2025 OBSERVING
Celestial Calendar
15h 10m
15h 00m
14h 50m
14h 40m
14h 30m
0°
2
3
4
5
6
7
8
Action at Jupiter
- 2°
16
3 5 7 91113151719 21 23 25 27 29
Apr 1
LIBRA
VIRGO
β
-10°
- 8°
May
1 3 5 7 9 11 13 15 17 19 2123 25 272931
- 4°
µ
- 6°
ALTHOUGH JUPITER is still months
away from its June 24th conjunction
with the Sun, the current apparition
is beginning to wind down. As April
opens, the planet's altitude remains
greater than 30° from sunset to around
10 p.m. local daylight time. However,
by the 30th that altitude window only
lasts from sunset to 8:30 p.m., when
civil twilight is ending. Fortunately,
Jupiter is bright enough to observe in
a telescope half an hour after sunset,
when the dusk sky is still bright. The
planet opens the month in Taurus
where it shines at magnitude -2.1 and
presents a disk spanning 36.1″. Enjoy
the views while you can!
Any telescope reveals the four big
Vesta Makes a Bright Return
VESTA REACHES OPPOSITION approximately
every 16 to 18 months, and it
hits that mark this year on May 2nd.
Five days later it has its closest approach
to Earth, when it slips by at a distance
of 177 million kilometers (110 million
miles). Vesta brightens to magnitude 5.6
this opposition, which means it should
be possible to spot without optical aid
under a dark sky. The Moon-free period
from late April through early May provides
your best chance.
As the chart above
shows, Vesta begins April
just 3¼° north-northwest
of 2.5-magnitude Beta (β)
Librae and crosses from
northern Libra into Virgo
on May 7th. From April
21-29, it's within 1° of the
star 16 Librae (magnitude
4.5), which serves as a
Dark, carbon-rich material is
exposed in landslides along the
rim of the crater Numisia (top)
and as speckles and blotches in
a smaller, unnamed crater (bottom)
on Vesta. Both images are
from NASA's Dawn mission.
50 APRIL 2025 * SKY & TELESCOPE
good marker for a naked-eye sighting
of the minor planet. Wait until later in
the evening when Vesta is highest and
use averted vision to claim your prize.
Of course, binoculars make sighting
the object a piece of cake.
Given its status as the brightest of
all asteroids, it's ironic that Vesta is
home to some of the darkest materials
in the solar system. Inky-black blotches
dot craters and their associated impact
ejecta. Data from NASA's
Dawn probe in 2011-2012
indicate that these dark
features are a good match
to carbonaceous chondrite
meteorites found on Earth,
the most famous of which
is the Murchison meteorite
that fell in Victoria,
Australia, in 1969. Similar
water-rich impactors
struck Vesta and likely all
the planets in the past. On
one planet at least (ours),
the materials may have
played a crucial role in the
origins of life.
Galilean moons, and binoculars usually
show at least two or three. The moons
orbit Jupiter at different rates, changing
positions along an almost straight line
from our point of view on Earth. Use the
diagram on the facing page to identify
them by their relative positions on any
given date and time. All the observable
interactions between Jupiter and its satellites
and their shadows are tabulated
on the facing page. Find events timed for
when Jupiter is at its highest.
Features on Jupiter appear closer to
the central meridian than to the limb
for 50 minutes before and after transiting.
Here are the times, in Universal
Time, when the Great Red Spot should
cross Jupiter's central meridian. The
dates, also in UT, are in bold. (Eastern
Daylight Time is UT minus 4 hours.)
March 1: 5:46, 15:42; 2: 1:38, 11:34,
21:29; 3: 7:25, 17:21; 4: 3:17, 13:13,
23:08; 5: 9:04, 19:00; 6: 4:56, 14:52; 7:
0:47, 10:43, 20:39; 8: 6:35, 16:31; 9: 2:26,
12:22, 22:18; 10: 8:14, 18:10; 11: 4:05,
14:01, 23:57; 12: 9:53, 19:49; 13: 5:44,
15:40; 14: 1:36, 11:32, 21:28; 15: 7:23,
17:19; 16: 3:15, 13:11, 23:07; 17: 9:03,
18:58; 18: 4:54, 14:50; 19: 0:46, 10:42,
20:37; 20: 6:33, 16:29; 21: 2:25, 12:21,
22:17; 22: 8:12, 18:08; 23: 4:04, 14:00,
23:56; 24: 9:51, 19:47; 25: 5:43, 15:39;
26: 1:35, 11:31, 21:26; 27: 7:22, 17:18;
28: 3:14, 13:10, 23:06; 29: 9:01, 18:57;
30: 4:53, 14:49; 31: 0:45, 10:41, 20:36
Star magnitudes
NASA / JPL-CALTECH / UCLA / MPS / DLR / IDA
taP
V
of
h
atse
Sky & Telescope - April 2025

Table of Contents for the Digital Edition of Sky & Telescope - April 2025
