Uranus at Eastern Quadrature – 2021

   Tuesday January 26th the position of the planet Uranus with respect to the Earth and the Sun places this ringed planet at what is called eastern quadrature. Uranus is at a 90 degree angle from the Earth. Think first quarter Moon as that is a fair comparison of the relative positions of the Earth, the Sun, and Uranus – or any outer planet. At this position Uranus follows the Sun across the sky from east to west as the Earth is rotating, meaning that Uranus rises after the Sun and sets after the Sun.

   So, where is Uranus? Look over the southern horizon after sunset for the reddish star-like object – the planet Mars. A few degrees above Mars is the star Hamal in the constellation of Aries the Ram. About 4o down to the right from Mars is the outer ringed planet Uranus.

   With a 5.77 apparent magnitude Uranus is just bright enough to be seen with binoculars as perhaps a very small dot. However Uranus is at about the naked-eye limit of visibility (6th magnitude) so it would take extremely dark skies to see it without optical assistance. Compare the apparent magnitude of Uranus with that of Mars at 0.34 and the 2.00 apparent magnitude for the star Hamal.

   
   
   

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September Moon at Perigee


   Our Moon reaches perigee, (closest distance from Earth), for this orbit on Wednesday September 13th. At that time the Moon will be at a distance of 28.99 Earth diameters (369,860 km or 229,820 miles) from the Earth.
   Does our Moon actually go around the Earth as this graphic shows? From our perspective on the Earth the Moon appears to circle around the Earth. However, in reality, the Moon orbits the Sun together with the Earth*

   On the day of the perigee Moon the 23-day old 3rd or last quarter Moon is above the east to southeastern horizon about an hour or so before the Sun rises. The inner planet Venus is very visible shining brightly above the horizon at -3.94 apparent magnitude, and Dwarf Planet Ceres at 7.92 apparent magnitude will not be visible but it is where the graphic indicates it to be.

   *Click here to read my 2006 Scope on the Sky column “The Real Shape of the Moon’s Orbit”. (PDF)

   Read this very informative article about the Earth-Moon system and their orbital motions, written by Joe Hanson. “Do We Orbit the Moon?”

   
   
   

Click here to go to the Qué tal in the Current Skies web site for monthly observing information, or here to go to bobs-spaces.