W
e’ve waited 15 long years and now it’s time to
party. Mars reaches perihelic opposition — an
opposition when a planet is at its closest point to
the Sun — on July 27. This is the first perihelic opposition
of Mars since August 2003, meaning that it’s bigger and
bolder in the night sky than it’s been in more than a
decade. Are you as eager as I am to roam its deserts and
poles with a telescope? Maybe even track a dust storm or
catch sight of clouds capping mighty Olympus Mons?
Mars, a planet that requires the patience of marble,
has a more eccentric orbit than most denizens of our
Solar System. At approximately two-year intervals, Earth
lines up with Mars at opposition, but a majority of those
alignments occur at the same time Mars is relatively far
from the Sun. Not this year. Mars is almost at perihelion
at the same time as opposition, so it will be a snug
.38 a.u. (57.6 million kilometers) away from Earth,
close enough for telescopic observers to have a
field day ferreting out dark surface markings
and changeable weather.
On the night of opposition, in the
company of the waxing gibbous Moon,
the Red Planet will burn an intense
magnitude –2.8, equaling Jupiter at
peak brightness. That’s a lot of lightto muster for a tiny planet only twice the size of our
Moon. It just goes to show how distance trumps size when
it comes to things celestial.
At the same time, the planet’s disk will balloon to
24.3′′ (arcseconds), only 0.8′′ smaller than during the
2003 opposition when Mars came its closest to Earth in
59,635 years. Because Mars won’t arrive at perihelion until
September, its closest approach to Earth is slightly delayed,
occurring on July 31. After that date, the two planets begin
to part ways.
June opens with Mars already 15.5′′ across and shining
at magnitude –1.2, nearly the equal of Sirius. Even users
of small telescopes should have no problem seeing the
south polar ice cap and numerous dark albedo markings.
By July 1, it fills out to 21.1′′ and reaches its greatest size at
month’s end as the polar cap continues to shrink.
As well as its glorious girth, southern observers will be
in the box seat during this juicy Mars apparition. At most
perihelic oppositions, including this one, the planet moves
into the belly of the ecliptic low in the southern sky. On
July 27, Mars gleams from southwestern Capricornus at
declination –25° and at culmination stands 81° above the
horizon from the latitude of Sydney. This high altitude
means fewer air layers to peer through, resulting in
decreased turbulence, better seeing and sharper images.SBURNING BEACON Mars glows above the Swiss 1.2-metre Leonhard Euler Telescope at ESO’s La Silla Observatory in Chile in this photo from
MARS: NASA / JPL-CALTECH; INSET: Y. BELETSKY (LCO)/ESO2014. The Red Planet will reach an almost-blistering magnitude –2.8 at opposition on July 27.
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