Archive
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.
02/04/2021 – Ephemeris – Finding Orion’s larger hunting dog
This is Bob Moler with Ephemeris for Thursday, February 4th. Today the Sun will be up for 9 hours and 58 minutes, setting at 5:56, and it will rise tomorrow at 7:56. The Moon, at last quarter today, will rise at 2:19 tomorrow morning.
The great winter constellation or star group Orion the hunter, is located in the southern sky at 9 p.m. His elongated rectangle of a torso is vertical. In the center of the rectangle are three stars in a line that make his belt. As a hunter, especially one of old, he has two hunting dogs. The larger, Canis Major can be found by following the three belt stars of Orion down and to the left. They point to Sirius, the brightest night-time star, also known as the Dog Star. It’s in the heart of a stick figure dog low in the southeast facing Orion that appears to be begging. There’s a fine star cluster, called Messier, or M 41, at the 5 o’clock position from Sirius. It’s easily visible in binoculars or a small telescope.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Orion and his hunting dogs with pointers as seen February. I didn’t have time in the program to mention Canis Minor, the little dog. I expect to cover it in the future, or you can search for Canis Minor in the search box above. Created using Stellarium.
I did not have time to talk about Canis Minor in this program due to the inclusion of M 41. I plan to cover Canis Minor soon. I have in the past. Search for Canis Minor in the search box above.
Star cluster M 41 finder chart. Created using Stellarium.
M 41 up close. Image courtesy of Tim Hunter and James McGaha, Grasslands Observatory at http://www.3towers.com
01/18/2021 – Ephemeris – The Drinking Gourd
This is Bob Moler with Ephemeris for Martin Luther King Jr. Day, Monday, January 18th. Today the Sun will be up for 9 hours and 18 minutes, setting at 5:32, and it will rise tomorrow at 8:13. The Moon, 2 days before first quarter, will set at 11:34 this evening.
This day is set aside to honor the Reverend Dr. Martin Luther King Jr. who gave his life for the struggle for equality for blacks and other minorities and to end segregation. A struggle that continues to this day. In the decades before the Civil War runaway slaves would travel, often at night, northward from the slave states of the south to the northern free states and Canada over the metaphorical Underground Railroad following the Drinking Gourd, the Big Dipper as their compass. Over the last several millennia the Great Bear, Ursa Major has been that northward pointer. For much of that time the North Pole of the sky had been passing near the handle of the Big Dipper or bear’s tail.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
An animation showing the Big Dipper, also known as the Drinking Gourd pointing to Polaris, the North Star which is just about due north. This is for 9 pm January 18th, about 3 1/2 hours after sunset. Created using Stellarium with additional annotations.
01/15/2021 – Ephemeris – The constellation Lepus the hare
This is Bob Moler with Ephemeris for Friday, January 15th. Today the Sun will be up for 9 hours and 12 minutes, setting at 5:28, and it will rise tomorrow at 8:15. The Moon, 2 days past new, will set at 8:17 this evening.
Orion, the central winter constellation is seen in the southern sky this evening. He is a hunter, as artists depict him, he is preoccupied with the charge of Taurus the bull from the upper right. At Orion’s feet, and unnoticed by him is the small constellation of Lepus the hare. It’s very hard to see a rabbit in its eight dim stars: however, I can see a rabbit’s head ears and shoulders. A misshapen box is the head and face of this critter facing to the left. His ears extend upwards from the upper right star of the box, and the bend forward a bit. Two stars to the right of the box and a bit farther apart hint at the front part of the body. In Lepus telescopes can find M79, a distant globular star cluster, one of the few visible in the winter sky.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
My view of Lepus the hare. Star field from Cartes du Ciel. Desert Cottontail drawing from Arizona-Senora Desert Museum website. Superimposed with GIMP.
An animation showing the stars, constellations and artwork of Lepus, Orion and Taurus from Stellarium. The constellation lines suggest a rabbit ears TV antenna. Created using Stellarium and GIMP.
01/14/2021 – Ephemeris – The constellation of Auriga the charioteer
This is Bob Moler with Ephemeris for Thursday, January 14th. Today the Sun will be up for 9 hours and 10 minutes, setting at 5:27, and it will rise tomorrow at 8:16. The Moon, 1 day past new, will set at 7:06 this evening.
The constellation Auriga the charioteer is nearly overhead at 9 p.m. It is a pentagon of stars, with the brilliant star Capella at one of its corners. Capella represents a she-goat he’s carrying. A narrow triangle of stars nearby Capella are her kids. The Kids is an informal constellation or asterism. Within and near that pentagon, binoculars and telescopes will find several star clusters, groups of hundreds of stars born in the clump we still see them in. These star clusters will appear as fuzzy spots in binoculars. One called M38 is near the center of the pentagon. Another, M36 is to the east of it. Still another star cluster, M37, is farther east, just outside the pentagon. The M designations come from Charles Messier who 250 years ago ran into them while looking for comets.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Auriga finder animation showing the Kids, nearby stars including Aldebaran and the sideways V shape of the Hyades (unlabeled) of Taurus the bull and the Pleiades AKA M 45. Created using Stellarium and GIMP.
01/12/2021 – Ephemeris – The celestial river Eridanus
This is Bob Moler with Ephemeris for Tuesday, January 12th. Today the Sun will be up for 9 hours and 7 minutes, setting at 5:25, and it will rise tomorrow at 8:17. The Moon, 1 day before new, will rise at 8:58 tomorrow morning.
One of the more obscure constellations around is Eridanus, which depicts a river. The river starts near the lower right corner of Orion, near the bright star Rigel and flows to the right then down near the southwestern horizon, then it meanders along the horizon to the south before turning below the horizon. One has to travel to the far south to see the southern terminus of the river, the bright star Achernar. Writers over the ages have seen here the Nile and the Earth circling river Ocean of the flat earth days. Achernar is actually two stars, the brightest was discovered to be the flattest star known, due to its rapid spin. The dimensions of Achernar A has been determined to be twice as wide across its equator than from pole to pole. It’s 139 light years away.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
An animation of the constellation Eridanus which is a river that flows from Rigel in Orion to the star Achernar below our southern horizon at latitude 45 degrees north. Create using Stellarium and GIMP.
01/11/2021 – Ephemeris – Procyon, the before the Dog Star
This is Bob Moler with Ephemeris for Monday, January 11th. Today the Sun will be up for 9 hours and 5 minutes, setting at 5:23 pm, and it will rise tomorrow at 8:17 am. The Moon, 2 days before new, will rise at 8:05 tomorrow morning.
Visible low in the east at 8 p.m. appears the star Procyon. To its right and below is Sirius the brightest night-time star. Procyon is the bright star in the constellation Canis Minor, or lesser dog. I can find only one other star in Canis Minor. Perhaps it’s a hot dog. If Sirius, in Canis major is the Dog Star then Procyon should be the Little Dog Star. However, Procyon is an interesting name. It means “Before the dog”, which is an allusion to the fact that Procyon, though east of Sirius actually rises before it. This is due to Procyon’s more northerly position. This effect doesn’t work south of the equator, however. Sirius will rise at about 7:30 tonight. Procyon is a star much like Sirius but is 32% farther away. It’s 11.4 to Sirius’ 8.6 light years away.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Orion and his hunting dogs in early winter (8 pm, January 11, 2021) showing that Procyon does rise before Sirius.
01/07/2021 – Ephemeris – The constellations Orion and Taurus interact
This is Bob Moler with Ephemeris for Thursday, January 7th. Today the Sun will be up for 8 hours and 59 minutes, setting at 5:19, and it will rise tomorrow at 8:19. The Moon, 1 day past last quarter, will rise at 3:13 tomorrow morning.
There are several instances in the Greek heavens where constellations appear to interact with one another. This is true with Orion the hunter and Taurus the bull. Taurus, whose face is the letter V of stars with orangish Aldebaran as his angry bloodshot eye is charging down on Orion, who has raised a lion skin shield on one arm and an upraised club in the other, ready to strike. They have been frozen in this pose for millennia. Stars below and right of the letter V of the Bull’s face suggest the front part of his body and his front legs charging at Orion. Orion also has two hunting dogs, Canis Major and Canis Minor. Canis Major with its dazzling star Sirius will rise around 7:30 on a line extended down from Orion’s belt.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Orion-Taurus Tableau. Seen around 8 pm, January 7, 2021. Created using Stellarium.
01/05/2021 – Ephemeris – Orion’s named stars and their meanings
This is Ephemeris for Tuesday, January 5th. Today the Sun will be up for 8 hours and 57 minutes, setting at 5:17, and it will rise tomorrow at 8:19. The Moon, 1 day before last quarter, will rise at 12:42 tomorrow morning.
The constellation of Orion the hunter is visible in the southeast at 8 p.m. The names of the stars of Orion are interesting in themselves. Starting at the top left of the seven bright stars of Orion’s torso is Betelgeuse the bright red star, whose name means something like “Armpit of the Giant”. The star in Orion’s other shoulder is Bellatrix the “Amazon Star”. Below are the three stars of Orion’s belt, from left to right; Alnitak, Alnilam and Mintaka. Their names mean “Girdle”, “Belt of Pearls”, and “Belt” respectively. Down to Orion’s knees we look on the left to the star Saiph pronounced “Safe”* which means “Sword”, though it is a star in his knee. Finally, there’s the bright blue-white star Rigel whose name means “Left Leg of the Giant” in Orion’s other knee. These are the important stars that make up the figure of Orion in the sky. [BTW. most star names are Arabic, and what survives of them is just a part of the original Arabic phrases.]
* In the radio program I pronounced the word then spelled it out.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The named stars of Orion. Created using Stellarium.
12/15/2020 – Ephemeris – Hyades, the face of Taurus the bull
This is Ephemeris for Tuesday, December 15th. Today the Sun will be up for 8 hours and 49 minutes, setting at 5:02, and it will rise tomorrow at 8:14. The Moon, 1 day past new, will set at 6:03 this evening.
The face of the constellation Taurus the bull looks like the letter V sideways above the rising Orion the Hunter in the east at 9 p.m. The bright star at the tip of a letter V of stars is Aldebaran. Look with binoculars at the letter V shape and you will see the stars of the Hyades star cluster The Hyades is the closest star cluster to us, at about 153 light years. And is important for that reason. Before satellites like Hipparcos and Gaia the Hyades was the only star cluster that could be directly measured by a technique called parallax, using the radius of the Earth’s orbit as one side of a surveyors enormous triangle. Its many stars at the same distance were used to determine distances of star clusters even farther away. Additional techniques based on the distance of the Hyades allowed us to measure distances to the nearest galaxies.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Aldebaran in the ‘V’ shape of the Hyades (The face of Taurus the bull) with the Pleiades above. Aldebaran is not part of the Hyades, being about halfway between us and the cluster. Created using Stellarium.
HR diagram showing the Hyades and Pleiades. Credit: European Southern Observatory.
The Hertzsprung–Russell diagram or HR diagram is one of the great astronomical tools developed in the early 20th century by plotting stars by surface temperature horizontally (hot to cool, left to right) and brightness vertically. It turns out that stars in the prime of life and shining via converting hydrogen to helium lie on a diagonal line from hot and bright from the upper left to cool and dim to the lower right. The line is called the main sequence. In plotting the Hyades stars against other star cluster stars the vertical displacement of the main sequence line is a function of the relative distances of the two star clusters from us. This is just one of the uses of the HR diagram.
Bob Moler's Ephemeris Blog 