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12/15/2017 – Ephemeris – Taurus, Bullish on Winter

December 15, 2017 1 comment

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

Taurus and Orion

Three views of Taurus the bull and Orion the hunter for about  p.m. in December.

Hyades and Pleiades

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.

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11/07/2017 – Ephemeris – The autumn constellations are all visible in the early evening

November 7, 2017 1 comment

Ephemeris for Election Day for some folks, Tuesday, November 7th. The Sun will rise at 7:28. It’ll be up for 9 hours and 54 minutes, setting at 5:23. The Moon, 3 days before last quarter, will rise at 8:49 this evening.

We’ll have about an hour and a half of reasonably dark skies between 6:30 and nearly 9 p.m. – At 8 p.m. all the autumn constellations are visible. The Zodiacal constellations from Capricornus in the southwest through Aquarius, Pisces and Aries, all relatively faint to Taurus rising in the east northeast. Pegasus the flying horse is seen in the high south-southeast. It and the connected constellation of Andromeda the chained princess are seen above Aquarius through Aries. The bright star Fomalhaut holds a lonely vigil low in the south, High in the northeast is the W shaped constellation of Cassiopeia the queen, under which is Perseus, her son-in-law and hero down to the bright star Capella.

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

Autumn constellations.

The sky at 8 p.m. November 7, 2017 showing the autumn constellations, centered on the southeastern sky. Click on the image to enlarge. The Milky Way has been brightened to show its passage through Perseus better. The red line is the ecliptic, the path of the Sun through the Zodiac. Created using Stellarium.

Addendum

 

11/06/2017 – Ephemeris – Taurus’ angry red eye, Aldebaran

November 6, 2017 1 comment

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

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.

09/12/2017 – Ephemeris – The Moon will hide the bright star Aldebaran after sunrise this morning

September 12, 2017 Comments off

Ephemeris for Tuesday, September 12th. The Sun will rise at 7:18. It’ll be up for 12 hours and 40 minutes, setting at 7:58. The Moon, 1 day before last quarter, will rise at 12:13 tomorrow morning.

This morning during daylight at around 8:40*. the bright star Aldebaran will disappear behind the Moon. Binoculars or a small telescope can be used to spot Aldebaran, the bright star in the constellation Taurus the bull’s eye. Taurus and the rest of the winter constellations are visible before sunrise. The sky needs to be absolutely clear to be able to spot the event. The star will be seen to approach the bright side of the Moon. The star will reappear around 9:53 a.m.* on the dark western edge of the Moon. These events are called occultations. They come from the word occult, which means hidden. In actuality the solar eclipse of three weeks ago was a spacial case of an occultation for those in the path of totality.

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

* The disappearance and appearance times for Aldebaran are within a couple of minutes for Western Michigan.  For other locations in the occultation path Stellarium will give pretty good times for the events by modeling the occultation as I did below.  Like a solar eclipse where you are determines the timing of the event.

Addendum

Occultation map

Map of where the occultation is visible. For the area bounded in red, the occultation is visible in the daytime. Credit: Occult4 by IOTA.

Position of the Moon in the sky

Position of the Moon in the sky near the start of the occultation, 8:35 a.m. September 12, 2017. Created using Stellarium.

Aldebaran and the Moon at 8:35 a.m.

Aldebaran and the Moon at 8:35 a.m. September 12, 2017. Created using Stellarium.

Aldebaran reappearing from behind the Moon

Aldebaran reappearing from behind the Moon at 9:53 a.m. September 12, 2017. Created using Stellarium.

 

02/16/2017 – Ephemeris – The Winter Circle

February 16, 2017 Comments off

Ephemeris for Thursday, February 16th.  The Sun will rise at 7:40.  It’ll be up for 10 hours and 32 minutes, setting at 6:12.  The Moon, 2 days before last quarter, will rise at 12:17 tomorrow morning.

The winter skies are blessed with more first magnitude stars than any other season.  These are the twenty-one brightest stars in the sky.  Six of these stars lie in a large circle centered on the seventh.  This circle is up all evening now that we are in the heart of winter.  Starting high overhead is Capella in Auriga the charioteer.  Moving clockwise, we come to Aldebaran in the face of Taurus the Bull.  Then down to Orion’s knee we find Rigel.  Down and left is the brightest star of all Sirius the Dog Star in Canis Major Orion’s large hunting dog, lowest of these stars in the south.  Moving up and left there is Procyon in Canis Minor, Then above it is Pollux in Gemini the twins.  All are centered on Betelgeuse in Orion.

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

Addendum

The Winter Circle of 1st magnitude stars

The Winter Circle of 1st magnitude stars. Created using my LookingUp program.

01/23/2017 – Ephemeris – The rabbit that got away

January 23, 2017 Comments off

Ephemeris for Monday, January 23rd.  The Sun will rise at 8:10.  It’ll be up for 9 hours and 29 minutes, setting at 5:39.  The Moon, half way from last quarter to new, will rise at 5:17 tomorrow morning.

Orion, the central winter constellation is seen in the south-southeast at 9 p.m. He is a hunter, but is preoccupied in defending himself from the charge of Taurus the bull to 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 whole rabbit in its eight dim stars: however, I do 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 show the front part of the body.  The free computer program at Stellarium.org shows a whole rabbit facing the opposite direction.

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

Addendum

Lepus

An animation showing the stars, constellations and artwork of Lepus, Orion and Taurus. Created using Stellarium and GIMP.

12/12/2016 – Ephemeris – The Moon will cover the eye of the bull tonight

December 12, 2016 Comments off

Ephemeris for Monday, December 12th.  The Sun will rise at 8:11.  It’ll be up for 8 hours and 51 minutes, setting at 5:02.  The Moon, 1 day before full, will set at 7:21 tomorrow morning.

Late tonight the nearly full moon will pass in front of the bright star Aldebaran.  This will be a difficult  event to spot due to the brightness of the Moon.  It will take a telescope at least to spot Aldebaran, the bright star the is the bloodshot eye in the face of Taurus the bull.  It might help to spot Aldebaran an hour or two early, while it’s some distance left of the Moon.  Aldebaran will disappear at the Moon’s left edge, while its a tiny distance from the bright edge of the Moon at around 10:54 p.m.  Aldebaran will reappear at about 12:09 a.m.  Make sure to start observing several minutes early since these are low precision times, plus your location affects the times.  These times are most accurate in the Western Lower Peninsula of Michigan.

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

Addendum

The Moon moves from west to east, so the occultation events will happen earlier to the west and later to the east.  Planetarium programs can be used to simulate the position of the Moon and stars and can be used to estimate the occultation start and end times.  To be accurate your location longitude and latitude must be entered in the program.

The times I developed are from the free program Cartes du Ciel and are within a minute of that provided by the more accurate program Occult4, which can be downloaded for free at the site below.  Planetarium programs are close enough, however.  Occult4 is somewhat difficult to use.

If you’re out keep a look out for some bright Geminid Meteors.  Their shower will reach its peak tomorrow night.

Occultation start

Start of the occultation at 11:54 p.m EST December 12, 2016. The grid is altitude and azimuth. Created using Cartes du Ciel.

Occultation start

End of the occultation at 12:09 a.m EST December 13, 2016. The grid is altitude and azimuth. Created using Cartes du Ciel.

Occultation visibility path

Path of the occultation. Locations between the bright boundaries would see the occultation at night. Created by the software program Occult4 by the International Occultation Timing Association.

Occultation animation

An animation created by Occult4 of the occultation of Aldebaran and some of the dimmer stars of the Hyades.

Eclipse and occultation information and software can be accessed at http://occultations.org/ the website of IOTA, the International Occultation Timing association.