Sky & Telescope - July 2020 - 47

Neptune rises roughly one hour
before Mars this month, and Uranus
follows the Red Planet by about one
hour. Like Mars, the two outer planets are still several months from their
respective oppositions.

December
solstice

Uranus

Mercury
March
equinox

PRE-DAWN AND DAWN
Venus ﬂames to its brightest and veritably rockets up from morning twilight
for observers at mid-northern latitudes
during July. Venus's lead on the Sun
increases from 2 hours to 3¼ hours
during the month, and the planet's sunrise altitude leaps from 21° to 35° - the
steepest monthly climb in its 8-year
cycle of recurring appearances. And the
brilliance of Venus during July makes it
easy to see with the naked eye at sunrise, or even shortly after in a very clear
sky. The queenly Morning Star blazes at
magnitude -4.7 for much of the month
before tapering off a tiny bit to -4.6.
The sight of Venus is especially
thrilling in the ﬁrst half of July as it
marches through the Hyades and passes
1° north of Aldebaran on the morning
of the 11th.
A scope shows Venus's crescent waxing from 19% to 43% illuminated as its
disk shrinks from 43″ to 28″ diameter
during the month. The planet reaches
greatest illuminated extent (47.4 square
arcseconds) on the 10th.

Dawn, July 11

Pleiades

45 minutes before sunrise

Sept.
equinox

Sun

Jupiter

Neptune
Saturn

Mars

Venus
Earth
June
solstice

ORBITS OF THE PLANETS
The curved arrows show each planet's movement during July. The outer planets don't change
position enough in a month to notice at this scale.

Mercury is at inferior conjunction
on June 30th and doesn't reappear in
the dawn sky until around July 17th,
when it shines at magnitude 1.1 and
rises 1¼ hours before the Sun. The tiny
planet reaches greatest elongation (22°
west of the Sun) on the 22nd. By then
Mercury has brightened nearly a full
magnitude to 0.2 but is only 37% illuminated and has an angular diameter
of just 7.8″.

EARTH AND MOON
Earth reaches aphelion (its greatest
distance from the Sun) at 7:35 a.m. EDT
on July 4th when our home planet is

94,507,635 miles from the Sun.
The Moon is at Full at 12:44 a.m.
EDT on July 5th and undergoes a
penumbral eclipse too slight for the eye
to detect. Mid-eclipse occurs at 12:30
a.m. EDT on July 5th. The Moon makes
a long curving line with Jupiter and
Saturn on the 4th, and the following
evening it forms a wonderful, compact equilateral triangle with the two
planets. At dawn on the 17th, a waning
lunar crescent is just a few degrees left
of Venus, with Aldebaran nearby. A very
thin Moon is left of Mercury 30 minutes before sunrise on the 19th.
¢ FRED SCHAAF teaches astronomy at
both Rowan University and Rowan College in southern New Jersey.

Dawn, July 17-19
30 minutes before sunrise
Aldebaran
Moon
July 17

TA U R U S

Venus

Dawn, July 25
30 minutes before sunrise

TA U R U S
Venus
Aldebaran

GEMINI

Moon
July 18
Castor
Mercury
Moon
July 19

Looking East

Looking East

Betelgeuse

Mercury

Pollux

Looking East-Northeast

s k y a n d t e l e s c o p e . o r g * J U LY 2 0 2 0

47
http://www.skyandtelescope.org
Sky & Telescope - July 2020

Table of Contents for the Digital Edition of Sky & Telescope - July 2020
