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See three planets in a line before sunrise |
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December 29, 2017 |
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By Bruce McClure
EarthSky.org
As 2017 draws to a close, cloud cover
permitting, three bright planets are lined up
across the eastern sky before sunrise. In their
order from the sunrise point upward, these
worlds are surprisingly bright Mercury, dazzling
Jupiter, and modesty-bright Mars.
Draw an imaginary line from the red planet Mars
through the king planet Jupiter to find Mercury,
the solar system’s innermost planet, near the
sunrise point on the horizon.
As Earth spins under the sky, Mercury is the
last planet to rise into the morning sky, coming
up just above your sunrise point as predawn
darkness gives way to morning twilight. In the
Northern Hemisphere, Mercury rises better than
90 minutes before the sun in late December. At
temperate latitudes in the Southern Hemisphere,
Mercury comes up about 70 minutes before
sunrise. Although this apparition of Mercury
favors the Northern Hemisphere, most everyone
worldwide should be in a good position to view
Mercury before sunrise for a week or so around
the time 2017 ends, and 2018 begins.
Technically, all five of the so-called bright
planets – Mercury, Venus, Mars, Jupiter and
Saturn – reside in the morning sky right now. By
bright planet, we mean any planet that can be
seen without an optical aid and which has been
observed by our ancestors since time immemorial.
Mercury, Jupiter and Mars are easy to see, but
Venus and Saturn sit so close to the glare of
sunrise that – while technically up before the
sun – they aren’t presently visible.
Day by day, Venus will sink sunward while Saturn
will climb upward toward Mercury. Venus will
transition over to the evening sky on January 9,
to be (again, only technically) the only bright
planet in the January evening sky.
Venus will be close to the sunset in January,
though, and you might not actually see Venus
until February.
Two planetary conjunctions will occur in the
January morning sky. For reference, the moon’s
diameter spans approximately 1/2-degree of sky.
Watch for Mars to swing less than 1/4-degree
south of Jupiter – half a moon-diameter – on
January 7; the moon itself sweeps past these
planets a few days later. Then Saturn will pass
a bit more than 1/2-degree north of Mercury –
about one moon-diameter – on January 13. At that
time, Saturn and Mercury will be close to the
sunrise and possibly hard to see; binoculars
will help.
Yes, the wandering planets will be a sight to
behold in the morning sky for the next few
weeks! |
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Let the moon be your guide to the
planets Jupiter and Mars on January 10,
11 and 12. |
Around
January 11, it’ll be easy to see the
moon with Jupiter and Mars, but tougher
to catch Mercury, and especially Saturn,
closer to the dawn. Binoculars might
come in handy! |
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