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Mars brighter in 2018 than any time since 2003 |
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January 9, 2018 |
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| Joanne
Richard Escober caught this image of
Mars, Saturn and Antares on May 28, 2016
– around the time of Mars’ last
opposition – at Apo Reef Natural Park
Occidental Mindoro, Philippines. Mars
was very bright in 2016, but it’ll be
even brighter in 2018! |
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By Deborah Byrd
EarthSky.org
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| Fresh from
their magnificent conjunction on January
7, Jupiter and Mars will appear near the
moon on January 9-12. |
Remember Mars in 2003? That was the year the red
planet came closer to Earth than it had been in
some 60,000 years.
Mars can be a bright planet. It can outshine
most stars. But, in 2003, for a few months, Mars
was exceedingly spectacular in our sky,
outshining all the stars and planets except
brilliant Venus. In 2018, Mars won’t be quite as
bright as it was in 2003.
But nearly!
It’ll dramatically brighten over the coming
months to appear as a red dot of brilliant flame
in our sky around July, 2018.
More than any other bright planet, the
appearance of Mars in our night sky changes from
year to year. Its dramatic swings in brightness
are part of what make Mars a fascinating planet
to watch with the eye alone.
Mars was faint throughout 2017. But it’s a bit
brighter now, as you might have noticed on
Sunday, January 7, when Mars and Jupiter had
their stunning conjunction before dawn.
When you contrast the brightness of Mars and
Jupiter in January 2018, you might not believe
that Mars will be brighter than Jupiter in six
months. But it’s true.
In late July 2018, around the time Earth sweeps
between Mars and the sun, Mars will outshine
Jupiter by some 1.8 times.
Why does Mars sometimes appear very bright, and
sometimes very faint? The first thing to realize
is that Mars isn’t a very big world. It is only
4,219 miles (6,790 km), making it only slightly
more than half as big as Earth at 7,922 miles
(12,750 km) in diameter.
So, when it’s bright, its brightness isn’t due
to its bigness, as is the case with Jupiter.
The main reason for Mars’ extremes in brightness
has to do with the proximity, or lack of
proximity, of Earth and Mars, during the orbits
of both worlds around the sun. It’s about the
nearness in space of our two worlds.
Sometimes Earth and Mars are on the same side of
the solar system, and hence near one another. At
other times, as it was throughout most of 2017,
Mars is far across the solar system from us.
Mars orbits the sun just one step outward from
Earth’s orbit. Earth takes a year to orbit the
sun once. Mars takes about two years to orbit
once. Opposition for Mars, when Earth passes
between Mars and the sun, happens every two
years and 50 days.
So Mars’ brightness waxes and wanes in our sky
about every two years. But 2018 is a very, very
special year for Mars. Mars will appear brighter
in our sky this year than it has since 2003.
The last opposition was on May 22, 2016. Around
that time, Mars was very bright indeed in
Earth’s sky.
This 2018 opposition of Mars isn’t an ordinary
opposition. Astronomers will call it a perihelic
opposition (or perihelic apparition) of Mars.
The word perihelion refers the point in Mars’
orbit when it is closest to the sun. Maybe you
can see that – in years when we pass between
Mars and the sun, when Mars is also closest to
the sun – Earth and Mars are closest.
That’s what will be happening in 2018, and it’s
why the Association of Lunar and Planetary
Observers (ALPO) wrote, "The 2018 perihelic
apparition of Mars will prove to be one of the
most favorable since the 2003 apparition when
the Red Planet came closest to Earth in 59,635
years ... the year 57,617 BC."
According to ALPO, in 2003, Mars came within
34.6 million miles to Earth, closer than at any
time in over nearly 60,000 years! It’ll be only
1.2 million miles farther away in 2018. Closest
approach for Mars in 2018 will take place on
July 31, some four days after its July 27
opposition.
For a period of about two months, Mars will
supplant Jupiter as the fourth brightest
celestial body, after the sun, moon and Venus.
Mars’ reign as the fourth-brightest celestial
body (or third brightest in the nighttime sky,
after the moon and Venus) will last from about
July 7 to September 7.
So 2017 was, indeed, a lousy year for Mars. But
just wait! Mars will be grand in 2018. |
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