Saturday, October 16, 2021

The Star That Vanishes

Looking east 11:00PM on September 14th. Can you spot the nearly invisible planet? SUBMITTED PHOTO

Looking east 11:00PM on September 14th. Can you spot the nearly invisible planet? SUBMITTED PHOTO


By Mike P. Usher

In the neck of Cetus, the sea-monster, just under the “C” on the accompanying chart, lies the star Mira. Most of the time it is invisible to the naked eye, so that is what the chart shows. About every 332 days Mira brightens to a maxima of about magnitude 3.5 and slowly sinks back to a minima of around 9. The given magnitudes are approximations; Mira is notably unpredictable. Historically it can get as bright as magnitude 2.0, making it the brightest star in the constellation or as dim as magnitude 10.1, making it hard to spot even in your binoculars. Mira is an oscillating variable star, both the first of its class discovered and the brightest. There are six to seven thousand Mira-type variable stars known, with periods of 80 to 1,000 days.

Mira hit a maxima about two weeks ago and is currently slowly sinking back into invisibility, taking about 200 days to reach the minima. It’s a little close to the horizon right now, but if you stay up late you should still be able to glimpse Mira.

In Cetus we have a vanishing star, but in nearby Pisces, the fish, we have a nearly invisible planet. Uranus at magnitude 5.73 tonight is just barely visible in a dark sky with the naked eye and totally invisible in suburban Marco. Don’t worry though, it’s a cinch with binoculars. As is typical with the two outer planets Uranus and Neptune seeing them is no problem with binoculars, but identification among innumerable stars of similar brightness is difficult. If you are interested in trying, just drop me an e-mail and I’ll send a finder chart.

Since the binoculars are out anyway, look for the Sculptor Galaxy also known as NGC 253. It’s one of the brighter galaxies in the sky and it’s rather surprising Messier never found it or gave it a number.

Look for a very flattened fuzzy oval shape, in the long dimension nearly the width ofthe full Moon; next month it will be further from the horizon and easier to spot.There are no good guide stars to use in the hunt, but be patient and sweep the area very slowly.

Mr. Usher is President of the Everglades Astronomical Society which meets the second Tuesday each month at 7:00PM in the Norris Center, Cambier Park, Naples.

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