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02/22/2018 – Ephemeris – The blue-white star at Orion’s knee
Ephemeris for Thursday, February 22nd. The Sun will rise at 7:32. It’ll be up for 10 hours and 49 minutes, setting at 6:21. The Moon, 1 day before first quarter, will set at 1:46 tomorrow morning.
The bright star at the bottom right corner of the big upright rectangle that is the giant hunter Orion’s body in the south-southeast is Rigel. It is a white star with a bluish tinge. It compares in brightness with Betelgeuse at the opposite end of Orion’s rectangle, though it’s usually a bit brighter. The mismatch in color makes brightness comparisons difficult. Rigel is about 860 light years away, It’s 23 times the mass of the Sun, 120 thousand the times brighter than the Sun, and a diameter almost the size of the orbit of Mercury. It’s age is thought to be about 8 million years. It has a visual companion star that can be seen in amateur telescopes. It’s not that dim, but suffers by being close to the arc light brightness of Rigel.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Orion’s named stars including the belt stars. Created using Stellarium.
Rigel with its companion star as photographed through a telescope. No attribution. Source: http://washedoutastronomy.com/content/urban-orion?page=1
02/12/2018 – Ephemeris – The Winter Circle
Ephemeris for Monday, February 12th. The Sun will rise at 7:47. It’ll be up for 10 hours and 19 minutes, setting at 6:07. The Moon, 3 days before new, will rise at 6:29 tomorrow morning.
The winter skies are blessed with more first magnitude stars than any other season. Six of these stars lie in a large circle centered on the seventh, It’s called the Winter Circle. This circle is up at 9 p.m. Starting high overhead is yellow Capella in Auriga the charioteer. Moving down clockwise is orange Aldebaran in the face of Taurus the Bull. Then down to Orion’s knee we find blue-white Rigel. Down and left is the brightest star of all the brilliant white Sirius the Dog Star in Canis Major, lowest of these stars in the south-southeast. Moving up and left is white Procyon in Canis Minor, Above Procyon is Pollux in Gemini the twins. All these are centered, well not quite, on Betelgeuse the bright red star in Orion’s shoulder.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The bright stars of winter arrayed in a circle (well almost). Created using Stellarium.
01/22/2018 – Ephemeris – The Pup
Ephemeris for Monday, January 22nd. The Sun will rise at 8:11. It’ll be up for 9 hours and 25 minutes, setting at 5:37. The Moon, 2 days before first quarter, will set at 11:24 this evening.
Sirius is the brightest night-time star and is located in the southeast at 9 p.m. below and a bit left of Orion the Hunter. We’ve visited Sirius last week. There is another star in the Sirius system that is practically invisible due to its dazzling glare. It’s Sirius B, nicknamed the Pup, alluding to Sirius’ Dog Star title. The tiny star was suspected as far back as 1834 due to Sirius’ wavy path against the more distant stars. Sirius is only 8.6 light years away. Sirius A and the Pup have 50 year orbits of each other. The star was first seen by Alvan Clark in 1862 while testing a new telescope. The Pup was the first of a new class of stars called white dwarfs. The Pup is about the size of the Earth, with the mass of our Sun, and 5 times hotter than the Sun’s surface. It’s out of fuel and slowly collapsing.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Orion and Canis Major Animation for 9 p.m. January 20, 2017. Created using Stellarium and GIMP.
Sirius A & B’s path in the sky showing the wobble that betrayed the Pup’s presence. Credit Mike Guidry, University of Tennessee.
Sirius A and B (near the diffraction spike to the lower left), A Hubble Space Telescope photograph. Credit NASA, ESA.
12/18/2017 – Ephemeris – The little dog shall lead
Ephemeris for Monday, December 18th. The Sun will rise at 8:14. It’ll be up for 8 hours and 49 minutes, setting at 5:03. The Moon is new today, and won’t be visible.
The constellation Orion has two hunting dogs. At 9 p.m. we’ll see one of them, the lesser dog, Canis Minor whose bright star Procyon is low in the East. Just two stars mark the constellation. Is it a dachshund or maybe a hot dog? The name Procyon means “Before the dog”, an odd title. It means that though east of Sirius, the bright dog star in Orion’s large dog, Canis Major, it rises before Sirius, due to its more northerly position in the sky. At 9 Sirius is just rising in the east-southeast. In many ways Procyon is nearly a twin of Sirius. It shines with the same white color, although a bit cooler, and has a white dwarf companion like Sirius. It’s a bit farther away than Sirius’ 8.6 light years. Procyon is at a distance of 11.46 light years.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Stars and constellations in the east at 9 p.m., about 4 hours after sunset, on December 18th. This only works for locations above 30 degrees north latitude. Created using Stellarium.
12/15/2017 – Ephemeris – Taurus, Bullish on Winter
Note: The title of this post I’ve taken from an article I wrote for the December 1999 issue of the Stellar Sentinel, the monthly newsletter of the Grand Traverse Astronomical Society, which I will reprint with some tweaks, as the addendum to this post. Winter will arrive in six days, though I’m not particularly bullish on it, but it fits the constellation I’m talking about today.
Ephemeris for Friday, December 15th. The Sun will rise at 8:12. It’ll be up for 8 hours and 50 minutes, setting at 5:02. The Moon, 3 days before new, will rise at 6:25 tomorrow morning.
Low in the east-southeast at 9 p.m. is the constellation of Orion the giant hunter. Above him is Taurus the bull. His face is a letter V shape of stars lying on its side with the bright orange-red star Aldebaran at the bottom tip of the V as its angry blood-shot eye. Orion is depicted in the sky facing him with club in one hand and a shield in the other the approaching and in some depictions charging Taurus. The V of stars is a star cluster called the Hyades. The Pleiades are in his shoulder above. Taurus, in Greek mythology, was the guise the god Zeus when he carried off the maiden Europa. Europa’s still with him, sort of, as the intriguing satellite with a buried ocean orbiting Zeus’ Roman equivalent the planet Jupiter.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Three views of Taurus the bull and Orion the hunter for about p.m. in December.
The Hyades (lower left) and the Pleiades (upper right). My photograph from many years ago BD (Before Digital).
The first constellation of winter to appear is probably a toss-up between Auriga the charioteer and Taurus the Bull. Auriga never quite disappears, or at least Capella its brightest star is circumpolar and never quite sets here in Northern Michigan. But Auriga sneaks up slowly in the northeast. Taurus on the other hand makes a grand entrance on autumn evenings preceded by the Pleiades, the Seven Sisters star cluster.
Taurus’ brightest star is Aldebaran, the bull’s angry bloodshot eye. It is at the left tip of a letter V of stars that is the bull’s face. Above the V are single stars that form the tips of its very long horns. Other stars below form the front legs of this beast. That’s it. Only the front part of the bull appears in the sky. In its shoulder are the Pleiades.
According to Greek mythology Taurus represents the god Zeus, the Roman Jupiter, who, in the disguise of a bull abducted the beautiful maiden Europa. This isn’t the only celestial disguise of Zeus. Cygnus is the disguise of Zeus in the famous Leda and the swan affair.
The Pleiades and the Hyades, the V-shaped star cluster of Taurus’ head also have their places in Greek Mythology. The Hyades and Pleiades are half sisters of each other who share Atlas as their father. But it is the Pleiades which are more prominent and have more stories about them. It is the Pleiades that are pursued by Orion the hunter, the central constellation of winter. And since the Pleiades are west of Orion it does appear that Orion continues to chase them around and around the sky daily. To the Kiowa Indians the Pleiades were also young maidens. As the story goes they were being chased by a large bear. The Great Spirit placed them on what we know today as Devil’s Tower in Wyoming to keep them out of reach of the bear. It is said that even today the sides of this tower show the scars of the bear’s claws. Devil’s Tower was the prominent landmark in the movie Close Encounters of the Third Kind. To the Anishinaabek native peoples around here the Pleiades is the “Hole in the Sky” or the seven sweating stones that are heated for the sweat lodge ceremony.
What do we know about Taurus today? Aldebaran is an orangish giant star which lies at a distance of 65 light years. It doesn’t belong to the Hyades, which is about 151 light years away. Aldebaran’s diameter is 40 times the Sun’s, about the diameter as the orbit of Mercury. It’s only 1.7 times tha mass of the Sun. Aldebaran shines at 153 times the Sun’s output.
Aldebaran appears to be part of the Hyades cluster, but it is less than half the distance to this most important star cluster. Though less prominent as the Pleiades, the Hyades is the most important star cluster in the heavens. The reason is because the Hyades was until recently the only star cluster close enough to get an accurate distance measurement by direct means. That direct means is parallax, measuring the shift of the star’s position in the sky due to the earth’s changing position in orbit of the Sun. The Hipparcos satellite has been refining these parallaxes over the past few years. Its measurement of the distance of the Hyades cluster is 151 light years give or take a bit less than a light year. The Hyades distance is the basis for all more distant measurements to the ends of the known universe.
The Hyades is a good binocular object with over 100 stars visible. The cluster actually overflows the binocular’s field of view. This cluster is also known as the Taurus Moving Cluster because its stars are receding towards a point northeast of Orion’s Betelgeuse.
Of course the splashiest part of Taurus is the Pleiades. For people with good vision 6 or more stars can be seen. I can see 4 or 5 stars and fuzz, which are unresolved stars. Many, who see the Pleiades for the first time, think the tiny pattern of stars is the Little Dipper. The stars do indeed look like a tiny dipper, with a nice bowl and a sawed off handle. And that’s what I call it: the Tiny Dipper. The big surprise of the Hipparcos distance measurements is the distance of the Pleiades. The generally accepted distance was about 410 light years. Hipparcos measured 375 light years. This means that the stars of the Pleiades are somewhat dimmer than believed before. Pleiades prior measurement was based on photometric or brightness measurements with the stars of the Hyades and other stars of the same type and known brightness and distance. So it turns out in the case of the Pleiades that the former measurements weren’t as accurate as thought, and means we have more to understand about stellar evolution as it relates to star brightness. Or perhaps Hipparcos is wrong. And interesting debate and more measurements are sure to follow.
The age of the Pleiades is thought to be around 100 million years, young compared to the Sun’s 4.6 billion years. Long exposure photographs and some telescopes can still spot the remaining wisp’s of the nebulae they were born from. The material is probably dust simply reflecting the light of the stars in the cluster.
Taurus is a great constellation to scan with a pair of binoculars.
11/20/2017 – Ephemeris – The Moon is near Saturn tonight and the approaching signs of winter
Ephemeris for Monday, November 20th. The Sun will rise at 7:46. It’ll be up for 9 hours and 23 minutes, setting at 5:09. The Moon, 2 days past new, will set at 7:04 this evening.
Tonight the two day old Moon will appear near Saturn. The ringed planet will appear to the left and a bit below the thin crescent Moon before they set about an hour later. The approaching winter season and the resumption of standard time have dropped sunset to 5:09 in the Interlochen/Traverse City area. Our sunset will drop another 11 minutes before slowly recovering 19 days from now. Two to three hours later another sign of the approaching winter season will appear, as the constellation of the giant hunter Orion rises in the east. He is resplendent with his nearly vertical belt of three stars rising, framed to the left and right by the bright stars reddish Betelgeuse and bluish Rigel. He will dominate our evening skies until April.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon and Saturn at 6 p.m. November 20, 2017. Created using Stellarium.
Finder chart for the rising Orion at 9 p.m., November 30, 2017. Created using Stellarium and GIMP.
11/06/2017 – Ephemeris – Taurus’ angry red eye, Aldebaran
Ephemeris for Monday, November 6th. The Sun will rise at 7:27. It’ll be up for 9 hours and 57 minutes, setting at 5:24. The Moon, 3 days past full, will rise at 7:52 this evening.
Last night the Moon passed in front of or occulted the bright star Aldebaran. Above right of Moon tonight is Aldebaran the bright orange star with a V shape of other stars in the face of Taurus the bull. Aldebaran appears at the lower left tip of that letter V laying on it’s side. With the bright Moon, it might take binoculars to pull out the faint stars of the V. Aldebaran isn’t actually part of the group, called the Hyades star cluster. The cluster is about 153 light years away, while Aldebaran is 65 light years away. The star has an orange hue because its surface is cooler than the Sun’s. However Aldebaran is 44 times larger in diameter, and shines 425 times brighter than the Sun. The name Aldebaran means “Follower” because it follows the Pleiades star cluster above it.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Aldebaran in the Hyades (unlabeled), with also the Pleiades, unlabeled, at the top and the Moon. at 9 p.m., November 6, 2017. Created using Stellarium.
10/30/2017 – Ephemeris – Halloween preview: The Ghoul Star
Ephemeris for Monday, October 30th. The Sun will rise at 8:17. It’ll be up for 10 hours and 15 minutes, setting at 6:33. The Moon, 3 days past first quarter, will set at 3:50 tomorrow morning.
Tomorrow night is the spookiest night of the year, so lets preview the spookiest star of all. It’s Algol, from Ghoul Star or Demon Star. The Chinese had a name for it that meant ‘piled up corpses’. It’s the second brightest star in the constellation Perseus the hero, rising in the northeast this evening. The star is located where artists have drawn the severed head of Medusa, whom he had slain. Medusa was so ugly that she turned all who gazed upon her to stone. Algol is her still glittering eye. Astronomers finally found out what was wrong with Algol. It does a slow 6 hour wink every two days 21 hours, because it is two stars that eclipse each other. It began to dip this morning just before sunrise and it will again centered on 11:41 p.m. Friday night.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Perseus, Cassiopeia, Andromeda with Algol finder animation for Autumn evenings. Created using Stellarium and GIMP.
Animation of an eclipsing binary star like Algol. Credit: Wikimedia Commons h/t Earth and Sky
10/23/2017 – Ephemeris – The loneliest star in the sky
Ephemeris for Monday, October 23rd. The Sun will rise at 8:08. It’ll be up for 10 hours and 35 minutes, setting at 6:44. The Moon, half way from new to first quarter, will set at 9:27 this evening.
There’s a bright star that appears for only seven and a half hours on autumn evenings from northern Michigan. It’s appearance, low in the south at around 10:30 p.m. tonight, is a clear indication of the autumn season. The star’s name is Fomalhaut, which means fish’s mouth. That’s fitting because it’s in the constellation of Piscis Austrinus, the southern fish. At our latitude it’s kind of the fish that got away, because Fomalhaut appears to be quite alone low in the sky. The faintness of the constellation’s other stars and location close to the horizon make the dim stars hard to spot. The earth’s thick atmosphere near the horizon reduces their brightness by a factor of two or more, so Fomalhaut, one of the brightest stars in the sky, keeps a lonely vigil in the south.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Fomalhaut in the south at 9:30 p.m. on October 23, 2017. Created using Stellarium.
09/07/2017 – Ephemeris – Capella rising
Ephemeris for Thursday, September 7th. The Sun will rise at 7:12. It’ll be up for 12 hours and 55 minutes, setting at 8:07. The Moon, 1 day past full, will rise at 9:08 this evening.
For those with the advantage of a low northern horizon, will see a bright star moving nearly parallel above the horizon over the evening hours or notice its change in position from night to night, moving to the northeast. The star is Capella, northernmost of the bright winter stars. It never quite sets for locations north of the latitude of Ludington (44° N), meaning it’s circumpolar like the Big Dipper. It’s slow motion, due to its position close to the north pole of the sky sometimes makes it seem odd. I’ve gotten several calls about it over the years. Capella is the brightest star in the constellation Auriga the charioteer, a constellation I see as a pentagon, with a small triangle of three stars on one side. I’ll wait until the winter season to talk further about them.
The times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Capella appearing to rise like an aircraft taking off. Shown here at hourly intervals from 9 p.m. to midnight. Created using Stellarium and GIMP.
Bob Moler's Ephemeris Blog 