AntaresJupiterSAGITTARIUS
SCORPIUSLUPUSLIBRAOPHIUCHUSJune 10, 11 P.M.
Looking south-southeastSaturn 10°Jupiter at its finest (^)
36 ASTRONOMY • JUNE 2019
Visible to the naked eye
Visible with binoculars
Visible with a telescope
MARTIN RATCLIFFE and ALISTER LING describe the
solar system’s changing landscape as it appears in Earth’s sky.
June 2019: Jupiter dazzles all night
SKYTHIS
MONTH
lthough June nights may
be short, you can pack
a lot of planet view-
ing into those limited
hours. Most observ-
ers will spend the bulk of
their time with Jupiter, which
reaches peak visibility and is
up all night. But you’ll also
want to watch Mercury and
Mars as they have their closest
evening conjunction in more
than a decade. Be sure to turn
your attention toward Saturn
and its magnificent rings as
midnight approaches, then
wrap up a memorable night
with a view of Venus in morn-
ing twilight.
But your first order of
business these June nights
should be to track down
Mercury and Mars. On the
1st, Mercury shines at magni-
tude –1.0 and appears 6° high
A
more prominent. This is earth-
shine — sunlight that bounces
off Earth, hits the Moon, and
ref lects back to our eyes. The
following evening, a slightly
fatter crescent Moon appears
6° to Mars’ upper left.
Over the next two weeks,
Mercury climbs higher and
Mars drops lower. The solar
system’s smallest planets are
destined for a dramatic meet-
ing just after midmonth. On
June 17, the two appear side by
side with 28' — just less than
the Full Moon’s diameter —
between them. (This is the
separation observers in central
North America will see; the
planets appear slightly farther
apart from the eastern part of
the continent and a bit closer
from farther west.)
On the evening of the 18th,
the two stand just 18' apart
— the closest they have been to
each other in the evening sky
in 13 years. Mercury now lies
above Mars and shines at mag-
nitude 0.1, some five times
brighter than its companion.
This close conjunction is
in the west-northwest a half-
hour after sunset. It stands
out quite nicely in the twilight
glow. Four other objects join
the inner planet. Capella, at
magnitude 0.1 the brightest
star in Auriga, stands 21° to
Mercury’s upper right. Mars
lies 16° to Mercury’s upper
left and at the same altitude
as Capella. Glowing at magni-
tude 1.8, the Red Planet may
be hard to see in twilight
without binoculars. Finally,
the twin stars Castor and
Pollux in Gemini appear 13°
directly above the slightly
fainter Mars.
A two-day-old crescent
Moon joins the party June 4.
Luna lies 6° to Mercury’s left,
and both stand some 9° high
30 minutes after sundown. As
the sky darkens, watch the
unlit side of the Moon grow
merely a line-of-sight effect.
Mars currently lies on the far
side of the Sun from Earth
while Mercury is on the near
side. The view through a tele-
scope confirms this: Even
though Mars is physically
40 percent larger than
Mercury, it appears only 3.7"
across — half as big as the
inner planet’s 7.4" diameter. A
telescope also shows the con-
trast between ruddy Mars’
nearly full disk and whiter
Mercury’s half-lit phase.
Following this close con-
junction, Mercury continues
to edge away from the Sun. It
reaches greatest elongation
June 23, when it lies 25° east
of our star and appears 11°
high a half-hour after sunset.
It then starts to sink closer
to the horizon, ending the
month 3.8° to Mars’ left.
As Mercury and Mars set
in the northwest, Jupiter
rises in the southeast. The
solar system’s largest planet
comes to opposition June 10,
when it lies opposite the Sun
in our sky and remains visible
Small telescopes reveal details in Jupiter’s cloud bands when the gas giant
looms large, as it does throughout June. In this Hubble Space Telescope
image, the Great Red Spot looks like a bloodshot eye with the shadow of
Ganymede representing its pupil. NASA/ESA/A. SIMON (GSFC)
The giant planet peaks at opposition June 10, but it reigns supreme against
the backdrop of Ophiuchus all month. ALL ILLUSTRATIONS: ASTRONOMY: RICK JOHNSON