Uranus makes a rare pass by a star in Pisces

To get oriented, face east around 10 o’clock and find the Great Square of Pegasus. Uranus is located one “square width” below and in line with the Square’s left side and forms an isosceles triangle with Delta and Omega Piscium. Charts created with Chris Marriott’s SkyMap

Last week at a star party I aimed my telescope at Uranus for the first time this season and was pleasantly surprised to find it next door to 44 Piscium (PYE-see-um), a star of identical brightness. One by one people lined up for a look. We had fun comparing the two colors – Uranus an obvious blue against the yellow-orange of 44 – and trying to figure which was the planet and which the star. That was apparently too easy, since everyone had no trouble telling them apart.

As we zoom in a little, Uranus and 44 Piscium stand out better. Delta and Omega Piscium will guide binocular users to the pair. Uranus is magnitude 6 and just visible with the naked eye from dark rural skies. Stars are shown to magnitude 7 with the view facing around 10 this evening (22nd).

Since then, Uranus has been edging closer to the star night after night. Tonight (Sept. 22) and tomorrow they’ll be at their closest and form a striking “double star” through binoculars and telescopes. How close? Only 1.4 arc minutes  or about 1/20 the diameter of the full moon. Those with excellent skies will see the pair as a single, faint, unresolved star, while binoculars will show them as a pair of close-set “eyes” staring straight back at you. In the coming nights, the planet will slowly pull away to the west but remain near 44 through the end of the month. Finding the 7th planet and seeing it groove through the sky is a very worthwhile observing project that requires only the simplest of equipment.

Our final chart is close in, so you can use it to track Uranus’ movement to the right (west) over the coming nights. Positions are shown for 10 p.m. CDT. The blue dots show the planet on the nights of closest approach.

Uranus always appears identical to a star with the naked eye and binoculars, but a small telescope magnifying 60x or higher will not only show the color difference between star and planet but also reveal Uranus as a tiny disk. 44 Piscium will remain a flickering point of light even at high power – a fine side-by-side example of the difference in appearance between a star-like planet and a star. I wonder if the colors will be visible in binoculars? Only one way to find out. Good luck!

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

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