04/18/2023 – Ephemeris – Orion rotates 90 degrees from rising to setting

This is Bob Moler with Ephemeris for Tuesday, April 18th. Today the Sun will be up for 13 hours and 37 minutes, setting at 8:31, and it will rise tomorrow at 6:52. The Moon, 2 days before new, will rise at 6:43 tomorrow morning.

As the constellation of Orion the hunter, that dominated our winter skies, moves into the west in the evening, it will have rotated 90 degrees from its rising orientation. As we saw it rising last November, its three belt stars were nearly vertically aligned. Now, as Orion nears the western horizon, those belt stars have rotated to be almost horizontal. The same is true of Gemini’s two brightest stars, Castor and Pollux. They are the two stars above red Mars, which is now halfway through Gemini on its eastward travels. Orion, a minor Greek hero, is most famous for how he died. I know of three versions, all different. The one that fits Orion’s current setting is that he was killed by the sting of a giant scorpion. So he must flee the sky before Scorpius the scorpion rises, which is around midnight tonight.

This amount of rotation between rising and setting is only true for latitudes near 45 degrees north or south, such as Northern Michigan, and objects near the celestial equator. The rotation for other latitudes would be 2 x (90 – latitude) for equatorial celestial objects. The name given for the term (90 – latitude) is colatitude.  90 degrees is the latitude of the Earth’s poles.

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

Addendum

When Orion is rising, its belt stars are nearly vertically aligned. Castor and Pollux, too, appear nearly vertically aligned. This was for November 30, 2022, at 9 pm. Mars was near opposition then and quite close to the Earth, so it had shown quite brightly. Created using Stellarium and LibreOffice Draw.

Orion’s belt stars show that the constellation has rotated about 90 degrees from their rising orientation. This is for 10 pm, April 18, 2023. Note that Venus is the Evening Star now, and Mars is much dimmer, as the Earth has moved ahead and away from it. Created using Stellarium and LibreOffice Draw, for the added labels.

01/20/2023 – Ephemeris – Gemini’s Castor is six stars orbiting each other

This is Ephemeris for Friday, January 20th. Today the Sun will be up for 9 hours and 21 minutes, setting at 5:34, and it will rise tomorrow at 8:12. The Moon, 1 day before new, will rise at 8:34 tomorrow morning.

At 9 p.m. the constellation of Gemini the twins will be seen high in the east-southeast. The namesake stars of the two lads are the two bright stars at the left of the constellation. Pollux the pugilist, or boxer, is the lower and slightly brighter of the two, while Castor, the horseman, is the other star, or rather a six-star system. In telescopes two close stars may be seen, each is a spectroscopic binary, meaning the lines of two stars can be seen in the spectrum, shifting as they orbit each other. Another faint spectroscopic binary also belongs. Pollux, though a single star, does have at least one planet with over twice the mass of Jupiter orbiting the star. Pollux and Castor are respectively 34 and 50 light years away. Not too far away as stars go.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.

Addendum

The Castor star system exploded in this JPL/NASA infographic.

01/19/2023 – Ephemeris – Gemini, twins with a secret

This is Ephemeris for Thursday, January 19th. Today the Sun will be up for 9 hours and 19 minutes, setting at 5:33, and it will rise tomorrow at 8:13. The Moon, 2 days before new, will rise at 7:38 tomorrow morning.

Another famous winter constellation is Gemini. The constellation of Gemini the Twins is visible halfway to the zenith in the east, at the top and left of Orion the hunter, at 9 pm. The namesake stars of the two lads, are the two bright stars at the left end of Gemini, and are high and are due east. Castor is on top, while Pollux is below. From them come two lines of stars that outline the two, extending horizontally toward Orion. In Greek mythology the lads were half brothers, Castor was fathered by a mere mortal, while Pollux was fathered by Zeus, but were born together as twins. When Castor was killed during the quest for the Golden Fleece, Pollux pleaded with Zeus to let him die also, so Zeus placed them together in the sky.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.

Addendum

Gemini finder animation for the second half of January 2023. It’s dated because Mars is dawdling in Taurus near the Pleiades. Mars is now back to heading eastward once again, after being in retrograde or westward motion as the Earth passed it in early December. Mars will officially enter Gemini in March. Created using Stellarium, and GIMP.

03/03/2022 – Ephemeris – Finding Cancer the crab

This is Ephemeris for Thursday, March 3rd. Today the Sun will be up for 11 hours and 16 minutes, setting at 6:33, and it will rise tomorrow at 7:15. The Moon, 1 day past new, will set at 7:46 this evening.

The constellation of Cancer the crab is made of dim stars, which are generally connected, in constellation charts, with lines that make either the letter K or an upside down Y, which lie directly between the star pair Castor and Pollux in Gemini and Regulus in Leo. In the center of the constellation is, what to the naked-eye is a fuzzy spot called Praesepe, or the manger. The two nearby stars, one to the northeast, and one to the southeast are Asellus Borealis, and Asellus Australis, the northern and southern donkey colts feeding out of the manger. Viewing that fuzzy spot with a pair of binoculars will reveal that it’s not fuzzy at all. It resolves into a cluster of stars, which astronomers, over the years, have called the Beehive cluster. Back in the first and second century CE, the Sun entered Cancer to begin the season of summer. It’s now just a transitional constellation between the winter and spring evening skies.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). They may be different for your location.

Addendum

Cancer, the crab finder chart. Note the beehive cluster, also known to amateur astronomers as M44, along with other catalog names. Prior to the invention of the telescope this cluster was known as Praesepe which means “Manger”. Click on the image to enlarge it. Created using Stellarium and GIMP.

A closer look at Cancer, noting the donkey stars Asellus Borealis and Australis feeding at the manger, Praesepe or M44, aka: the Beehive Cluster. Created using Cartes du Ciel (Sky Charts) and LibreOffice for captions. Adapted from a chart I created for the March 2022 issue of the GTAS newsletter, the Stellar Sentinel.

01/27/2022 – Ephemeris – Looking at the constellation of Gemini the twins

This is Ephemeris for Thursday, January 27th. Today the Sun will be up for 9 hours and 37 minutes, setting at 5:44, and it will rise tomorrow at 8:06. The Moon, 2 days past last quarter, will rise at 4:56 tomorrow morning.

Another famous winter constellation is Gemini. The constellation of Gemini the Twins is visible high in the southeast, above and left of Orion the hunter, at 9 p.m. The namesake stars of the two lads, are the two bright stars at the left end of Gemini, and are high and nearly in the east. Castor is on top, while Pollux is below. From them come two lines of stars that outline the two, extending horizontally toward Orion. In Greek mythology the lads were half brothers, Castor was fathered by a mere mortal, while Pollux was fathered by Zeus, but were born together as twins. When Castor was killed during the quest for the Golden Fleece, Pollux pleaded with Zeus to let him die also, so Zeus placed them together in the sky.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). They may be different for your location.

Addendum

Gemini finder animation for 9 pm January 27th, showing just stars, constellation lines and star names, and figures of the lads. Click on the image to enlarge it. Created using Stellarium and GIMP.

02/08/2021 – Ephemeris – A look at Gemini the twins

This is Ephemeris for Monday, February 8th. Today the Sun will be up for 10 hours and 9 minutes, setting at 6:01, and it will rise tomorrow at 7:51. The Moon, 3 days before new, will rise at 6:49 tomorrow morning.

Let’s look at another of the winter constellations, and a member of the Zodiac. The constellation of Gemini the Twins is visible high in the southeast, above and left of Orion the hunter at 9 p.m. The namesake stars of the two lads, will be at the left end of Gemini, are nearly overhead and vertically aligned. Castor is on top, while the slightly brighter Pollux is below. From them come two lines of stars that outline the two extending toward Orion. In Greek mythology the lads were half brothers, Castor was fathered by a mere mortal, while Pollux was fathered by Zeus, but were born together as twins. When Castor was killed during the quest for the Golden Fleece, Pollux pleaded with Zeus to let him die also, so Zeus placed them together in the sky, so they could be together forever.

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

Addendum

Gemini finder animation for early February at 9 pm (about 3 hours after sunset). Created using Stellarium and GIMP.

03/12/2020 – Ephemeris – The mythology behind the constellation of Gemini

Ephemeris for Thursday, March 12th. Today the Sun will be up for 11 hours and 46 minutes, setting at 7:45, and it will rise tomorrow at 7:57. The Moon, 3 days past full, will rise at 11:45 this evening.

Lets look at the next to last of the winter constellations, and member of the Zodiac. The constellation Gemini, the Twins is visible high in the southeast, above and left of Orion the hunter at 9 p.m. The namesake stars of the two lads, will be at the left end of Gemini, nearly vertically aligned. Castor is above, Pollux below. From them can be traced two lines of stars extending toward Orion that outline the two. In Greek mythology the lads were half brothers, Castor was fathered by a mere mortal, while Pollux was fathered by Zeus in the famous Leda and the swan affair and immortal, but were born together as twins. When Castor was killed during the quest for the Golden Fleece, Pollux pleaded with Zeus to let him die also, so he placed them together in the sky so they could be together forever.

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

Addendum

Gemini finder looking south-southeast around 9 p.m. March 10th, 2020. Created using Stellarium.

Castor and Pollux namesakes of the twins of Gemini in its position around 9 p.m. EDT March 12th. Created using Stellarium.

03/10/2020 – Ephemeris – A Closeup look at Gemini’s namesake stars

Ephemeris for Tuesday, March 10th. Today the Sun will be up for 11 hours and 39 minutes, setting at 7:43, and it will rise tomorrow at 8:01. The Moon, 1 day past full, will rise at 9:07 this evening.

At 9 p.m. the constellation of Gemini the twins will be seen high in the south-southeast. The namesake stars of the two lads are the two bright stars at the upper left of the constellation. Pollux the pugilist, or boxer, is the lower of the two, while Castor, the horseman, is the other star, or rather a six star system. In telescopes two close stars may be seen each is a spectroscopic binary, meaning the two stars can be detected by the rainbow colors of light from the star. A faint nearby spectroscopic binary also belongs. Pollux, though a single star, does have at least one planet, over twice the mass of Jupiter orbiting it at a distance somewhat greater than Mars is from the Sun. Pollux is 34 light years away while Castor is 50 light years away.

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

Addendum

Gemini finder looking south-southeast at 9 p.m. March 10th, 2020. Created using Stellarium.

Castor and Pollux namesakes of the twins of Gemini in its position at 9 p.m. EDT March 10th. Created using Stellarium.

The Castor star system exploded in this JPL/NASA infographic.

 

02/11/2019 – Ephemeris – The stars Castor and Pollux

Ephemeris for Monday, February 11th. Today the Sun will be up for 10 hours and 16 minutes, setting at 6:05, and it will rise tomorrow at 7:47. The Moon, 1 day before first quarter, will set at 12:57 tomorrow morning.

At 9 p.m. the constellation of Gemini the twins will be seen high in the southeast. The namesake stars of the two lads are the two bright stars at the top of the constellation. Pollux the pugilist, or boxer, is the lower of the two, while Castor, the horseman, is the other star, or rather a six star system. In telescopes two close stars may be seen each is a spectroscopic binary, meaning the lines of two stars can be seen in the spectrum. A faint nearby spectroscopic binary also belongs. Pollux, though a single star, does have at least one planet, over twice the mass of Jupiter orbiting the star at a distance somewhat greater than Mars is from the Sun. Pollux is 34 light years away while Castor is 50 light years away. Not too far away as stars go.

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

Addendum

Gemini with Castor and Pollux. Created with Stellarium.

The Castor star system exploded in this JPL/NASA infographic.

5/15/2018 – Ephemeris – Two thirds thru spring

Ephemeris for Tuesday, May 15th. Today the Sun will be up for 14 hours and 49 minutes, setting at 9:04, and it will rise tomorrow at 6:13. The Moon is new today, and won’t be visible.

Here we are at the middle of May, nearly two-thirds through spring and in the west only a few winter stars remain. Castor and Pollux of Gemini are horizontal in the west, Procyon the Little Dog Star is below and left of them, Capella in Auriga is in the northwest, but for most of the IPR listening area it will never quite set. At 10:30 Betelgeuse in Orion the hunter will be setting, chased from the skies by Scorpius the scorpion, which is rising in the southeast. In one story it is the sting of this scorpion that killed him. Already at that time two-thirds of the stars of the summer Triangle are up. Bright Vega in Lyra the harp, and Deneb in Cygnus the swan. The Big Dipper reigns overhead as spring is in full bloom.

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

Addendum

The sky dome for 10:30 p.m. May 15, 2018 showing the stars and constellations. It may not work for any latitude or time, but it works for our location, near 45 degrees north. Created using Stellarium.