Skywatch: Perigee and perihelion this week


The new year starts out with a full moon. On Monday, look for the full moon at 9:24 in the evening. This month’s full moon is known as the Wolf Moon because hungry wolves could be heard howling outside of villages as winter wore on and food became scarce. This has also been called the Old Moon.

Because this month’s full moon happens so close to the moon’s perigee for the month (point of orbit when it’s closest to the Earth), we can call it a “Supermoon”. At 221,559 miles from Earth, this is actually the closest lunar perigee of 2018 so if the moon looks bigger and brighter than normal on Monday night, you’re not imagining things.

Our innermost planet will also reach a milestone on January 1st. Mercury will reach what’s known as greatest elongation at 3:00 P.M. Monday. It’ll shine brightly in the sky on Tuesday morning as a result. The planet will hang low in the southeastern sky on Tuesday morning with Jupiter and Mars above and right of it. Again, look in the SE at around 6:45 A.M. and if skies are clear, you’ll catch three planets as you start your day.

Our own planet hits a milestone this week as well. Earth’s perihelion takes place at 12:35 A.M. on Wednesday morning. One may think that planets and heavenly bodies have circular orbits but that’s not true, they actually take on elliptical orbits. As a result, there are times when the Earth is closer to the sun and when it’s farther away. On Wednesday, Earth will be 91.4 million miles from the sun marking the closest point in its yearly orbit about our star. The fact that we’re closest to the sun during our coldest time of year underscores the fact that our planet’s seasons are caused the tilt of the planet and not its distance from the sun. As always, this time of year, we need the disclaimer that this is what you’ll find when the skies cooperate and clear out for us. Happy hunting!