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Posts Tagged ‘Alcor’

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

June 26, 2020 Comments off

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

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 would appear in a telescope

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

April 19, 2018 Comments off

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 with Mizar & Alcor

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

Telescopic Mizar and Alcor

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

March 15, 2016 Comments off

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

 

Big Dipper

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.

Mizar and Alcor

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

June 2, 2011 Comments off

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

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