skyandtelescope.org• JUNE 2020 47This means the planet is moderately
high in the southeast when morning
twilight begins to brighten the sky.
Mars increases from magnitude 0.0
to –0.5 during June — its tiger-colored
fi re crossing from Aquarius to Pisces
on the 24th. The planet reaches west
quadrature (90° west of the Sun) on
the 6th, so its gibbous disk will show
a strong shadowed edge in telescopes
this month. Mars’s apparent diameter
increases from 9.3′′ to 11.4′′ in June, the
size at which it begins to show sig-
nifi cant surface detail in medium-size
instruments when seeing conditions
are particularly steady.
Neptune glows at magnitude 7.9
just 1.6° northwest of Mars on the
morning of June 13th, with the Moon
just a few degrees east of the Red
Planet. Uranus rises two hours later
than Neptune but shines a full two
magnitudes brighter.
DAWN
Venus technically doesn’t exit the
evening sky until it comes to inferior
conjunction with the Sun at 18h UT on
June 3rd. Venus slips through the plane
of Earth’s orbit almost exactly two days
after that date, so instead of transiting
the solar disk (as it did in 2004 and
2012), it passes just half a solar diam-
eter north of the Sun. The following
weeks fi nd Venus lofting steadily higher
in morning twilight and brightening
rapidly as its phase waxes from “new”
to a thin crescent. On the 12th Venus
rises about 45 minutes before the Sun,
shines at magnitude –4.1, and features
a disk that’s 55′′ wide and roughly 3%
illuminated. By the 20th, the planet
rises 80 minutes before the Sun, shines
at –4.5, and has a 51′′-diameter disk
that’s 9% illuminated. Venus ends the
month clearing the east-northeastern
horizon 2 hours before sunrise in a sky
dark enough to appreciate it gleaming
on the edge of the Hyades, in Taurus.
By then the new morning star has
brightened to magnitude –4.7, with a
44 ′′-wide disk 18% illuminated.SUN AND MOON
The Sun reaches the June solstice at
5:44 p.m. EDT on the 20th, ushering
in summer in the Northern Hemi-
sphere and winter in t he Southern
Hemisphere. One day later, an annular
eclipse of the Sun is visible across parts
of Africa, Asia, and the western Pacifi c
(see page 50 for details).
Observers in Europe, Africa, Asia,
and Australia have an opportunity
to watch the Moon undergo a weak
penumbral lunar eclipse on June 5th. At
dawn on the 8th, the waning gibbous
Moon marks the westernmost point of
a gentle curve with Jupiter and Saturn
equally spaced along it. On the follow-
ing morning the Moon has shifted posi-
tion and now holds down the eastern
end of that curve.
A spectacular close conjunction of
the thin lunar crescent and Venus is
visible low in the east-northeast around
30 minutes before sunrise on the morn-
ing of the 19th (the event is an occulta-
tion in parts of the Eastern Hemisphere
— see page 49 for more). After the new
Moon, the waxing lunar crescent reap-
pears at dusk, and on the 22nd it’s posi-
tioned below and to the left of Pollux
and Castor, low in the west-northwest
during twilight.¢FRED SCHAAF teaches astronomy
at both Rowan University and Rowan
College in Gloucester County, southern
New Jersey.Jupiter
SaturnUranusNeptune MercuryVenus
Earth MarsMarch
equinoxJune
solsticeDecember
solsticeSept.
equinox
SunORBITS OF THE PLANETS
The curved arrows show each planet’s movement during June. The outer planets don’t change
position enough in a month to notice at this scale.skyandtelescope.org• JUNE 2020 47Dusk, June 22 – 23
30 minutes after sunsetPollux CastorMoon
June 22Moon
June 23Looking West-NorthwestDawn, June 27
45 minutes before sunriseAldebaranVenusLooking East-NortheastPleiades