January 4, 2022: Earth is at perihelion today – it’s closest point to the sun. Mars is a morning planet, while the evening planet pack – Venus, Mercury, Saturn, and Jupiter – and the crescent moon are in the southwest after sundown.
by Jeffrey L. Hunt
Chicago, Illinois: Sunrise, 7:18 a.m. CST; Sunset, 4:33 p.m. CST. Check local sources for sunrise and sunset times for your location.
Our planet reaches its closest point to the sun at 12:55 a.m. CST in its annual trek, a little over 91 million miles from the central star.
The planets revolve around the sun in orbital paths that are best described as ellipses. The orbits are not circles, but slightly not circular. This property is known as the eccentricity of the orbit.
A circle has an eccentricity of zero. Earth’s eccentricity is 0.017. Venus’ orbit is the most circular with a value of 0.007. Mercury’s orbit is 0.206 and Pluto is 0.248.
Comet Halley’s eccentricity is 0.967.
Orbits with eccentricities of larger values that are nearing the number one vary greatly in their distances from the sun. Cometary orbits have perihelion points very close to the sun and aphelions far into the solar system.
Pluto’s perihelion point is closer to the sun than Neptune and during the last century it was the eighth classic planet from the sun.
When Mars is near perihelion as Earth passes by, the Red Planet is very bright in the sky. This occurred in 2018. The Red Planet’s oppositions are moving toward the aphelion point during the next several years.
Happy Perihelion Day!
Morning Sky
This morning Mars continues its slow climb into the morning sky. The planet’s slow appearance in the morning sky is from its eastward motion along the plane of the solar system. It moves about 0.7° eastward each morning. While the stars rise about four minutes earlier each morning from our revolution around the sun, Mars rises about one minute earlier every two days.
About forty-five minutes before sunrise, Mars is over 10° above the southeast horizon and 7.0° to the left of Antares.
Evening Sky
Venus continues to slide into bright twilight. This evening it is low in the southwest, only about 3° up at 30 minutes after sunset.
As the sky darkens further and Venus sets, the crescent moon – 7% illuminated – is over 10° above the southwest horizon.
Saturn is 4.1° to the upper right of the lunar slice. Mercury is 11.6° to the lower right of the moon and 8.8° to the lower right of Saturn.
Bright Jupiter is 17.6° to the upper left of the moon. Watch the moon approach and pass Jupiter during the next few evenings.
What is the last evening you see Venus? Inferior conjunction is four days away.
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