05/23/2022 – Ephemeris – the Moon and the morning planets plus the Big Dipper’s stars Mizar and Alcor

This is Bob Moler with Ephemeris for Monday, May 23rd. Today the Sun will be up for 15 hours and 6 minutes, setting at 9:13, and it will rise tomorrow at 6:05. The Moon, 1 day past last quarter, will rise at 3:44 tomorrow morning.

This week, the Moon is in the process of passing the morning planets. This morning it passed Saturn. Tomorrow afternoon and evening it will pass Mars, then Jupiter. By Thursday morning, the Moon will be below and left of Jupiter. Thursday evening, it will pass Venus.

Back to tonight’s sky, the Big Dipper is nearly overhead. In its handle is a star or two that are interesting. It’s the star at the bend in the handle. It’s called Mizar. Next to it, for those with good eyesight, is a dimmer star, called Alcor. The name Mizar is from the Arabic, meaning apron or cover, while Alcor means the forgotten one. Before optometrists, the ability to actually see both stars was a test for good eyesight, especially for Arabic warriors. The pair is also known as the “Horse and the Rider”.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). They may be different for your location.

Addendum

The Moon passing the morning planets at 5 am 5/23/2022 to 5/27/2022. Click on the image to enlarge it. Created using Stellarium and GIMP.

Mizar and Alcor in the Big Dipper as it is nearly overhead towards the north. Click on the image to enlarge it. Created using Stellarium.

Alcor seems to be a true companion to Mizar, since they are at the same distance of 81.7 light years. Alcor also has an unseen companion star. Mizar also has a much closer companion star that can be seen in a telescope. On top of that, each of them has another unseen companion star. Six stars for the price of two. What a deal.

How can you detect a companion star that can’t be seen? When analyzing a star’s spectra, the companion star betrays it presence by its chemical absorption lines shifting with respect to its primary due to the Doppler effect of its motion.

06/26/2020 – Ephemeris – The stars known as the Horse and Rider

Jun 26. This is Bob Moler with Ephemeris for Friday, June 26th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:32, and it will rise tomorrow at 5:59. The Moon, 2 days before first quarter, will set at 1:28 tomorrow morning.

The most interesting star in the Big Dipper is Mizar and its dim companion Alcor. It is the second star from the end of the handle, where the bend in the handle takes place. Folks with good vision can see the dimmer star right next to Mizar. In ancient times it was used as an eye test for visual acuity for warriors. As such it was known as the “Horse and the Rider”. Mizar is second magnitude, in the second rank of star brightness invented by the Greek astronomer Hipparchus in the 2nd century BC. He ranked stars in 6 classes, from first magnitude for the brightest to 6th for the dimmest visible to the naked eye. Alcor comes in at 4th magnitude. It does suffer a bit by being very close to Mizar which is 6 times brighter.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Mizar finder animation for the Big Dipper’s orientation in late June at 11 pm where I live or an hour and a half after sunset. Created using Stellarium and GIMP.

Mizar and Alcor as they might appear in a telescope. Mizar is a binary star in a telescope. The other star in the field is apparently a background star. The brighter star of Mizar is Mizar A, while the dimmer is Mizar B. It turns out that Mizar A and B plus Alcor are all spectroscopic binaries, meaning the companion stars are too close to resolve in telescopes, but whose motion shows up in the spectra of the stars. Mizar and Alcor are around 80 light years away. Created using Stellarium.

04/19/2018 – Ephemeris – The Big Dipper’s stars Mizar and Alcor

Ephemeris for Thursday, April 19th. The Sun rises at 6:51. It’ll be up for 13 hours and 41 minutes, setting at 8:32. The Moon, 3 days before first quarter, will set at 12:47 tomorrow morning.

The most interesting star in the Big Dipper is Mizar and its dim companion Alcor. It is the second star from the end of the handle, where the bend in the handle takes place. Folks with good vision can see the dimmer star right next to Mizar. In ancient times it was used as an eye test for visual acuity for warriors as such it was known as the “Horse and the Rider”.

Mizar is second magnitude, in the second rank of star brightness invented by the Greek astronomer Hipparchus in the 2nd century BC. He ranked stars in 6 classes, from first magnitude for the brightest to 6th for the dimmest visible to the naked eye. Alcor comes in at 4th magnitude. It does suffer a bit by being close to Mizar which is 6 times brighter.

The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Big Dipper, almost overhead at 10 p.m. April 19 with Mizar and Alcor pointed out. Created using Stellarium.

A view of Mizar and Alcor as seen in a telescope. Mizar is itself a binary star. In actuality both components of Mizar and Alcor are spectroscopic binaries, which are too close to split, but their presence is detected by their Doppler motions with spectrographs. Created using Stellarium.

03/15/2016 – Ephemeris – Spotting the celestial Horse and Rider

Ephemeris for, the Ides of March, Tuesday, March 15th.  The Sun will rise at 7:54.  It’ll be up for 11 hours and 55 minutes, setting at 7:49.   The Moon, at first quarter today, will set at 3:36 tomorrow morning.

In the handle of te Big Dipper rising high in the east northeast is an easily seen double star.  It’s the star second from the end of the handle where it makes a bend.  The bright star is Mizar.  It has a dim companion star that folks with good eyesight can easily spot, named Alcor.  The Arabs of old, before optometrists used the pair as an eye test.  I would have failed.  Even with my glasses on I can’t spot Alcor.  I must resort to binoculars.  The pair is known as the Horse and Rider, while the indigenous peoples of North America, see the stars of the handle of the Big Dipper not as the great Bear’s tail, but hunters following the bear.  In this case Alcor is either a hunting dog, or a cooking pot to cook the bear in.

Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

 

The Big Dipper, part of Ursa Major the Great Bear, is poised on its handle in the northeast. Can you spot Alcor? Created using Stellarium.

A closeup view of Mizar and Alcor and a dimmer star that lies in the background. Created using Stellarium.

A telescope with low power will also split Mizar intro a bright and dim companion named Mizar A and Mizar B.  By observing Mizar A, B and Alcor have determined that all three are binary.  There’s six stars there.

06/02/11 – Ephemeris – The stars Mizar and Alcor

Thursday, June 2nd.  Today the sun will be up for 15 hours and 21 minutes, setting at 9:21.   The moon, 1 day past new, will set at 10:21 this evening.  Tomorrow the sun will rise at 5:59.

The Big Dipper is high in the northwest at 11 p.m. now.  It’s handle is also the tail of the Great Bear or Ursa Major.  An Native American view of the bear was the the stars of the Big Dipper’s handle were not a tail, but hunters following the bear.  The star Mizar, at the bend of the handle has a dim companion called Alcor.  This was the cooking pot the hunters will cook the bear in.  The ancient Arabs saw these two stars as the Horse and the Rider, and it was an eye test for warriors.  If you could see Alcor, your eyesight was good enough.  Even with my glasses I can rarely see this dim star, so I suppose I’d be the Arabic equivalent of a 4F.  If you have a telescope, check out the Mizar-Alcor pair and you’ll find that Mizar has a close companion itself.

* Times are for the Traverse City/Interlochen area of Michigan.  They may be different for your location.

Addendum

The Stars Mizar and Alcor in the Big Dipper. Cartes du Ciel