Archive

Posts Tagged ‘Hyades’

04/24/2018 – Ephemeris – Venus will be south of the Pleiades tonight

April 24, 2018 Comments off

Ephemeris for Tuesday, April 24th. The Sun rises at 6:43. It’ll be up for 13 hours and 55 minutes, setting at 8:39. The Moon, 2 days past first quarter, will set at 4:51 tomorrow morning.

Tonight the brilliant planet Venus will be just south of the Pleiades, also known as the Seven Sisters star cluster. From our cockeyed position on the Earth about half way from the equator and the North Pole. The sky in the east and west, low in the sky, is tilted about the same angle, namely about 45 degrees. If you’re listening to this program from other than Northern Michigan the angle will be the same as your latitude. So instead of south being down, as one would expect when looking to the south, south is to the lower left when looking to the west. On this program Thursday, Friday and Monday I’ll be talking about Venus and what the ancients found out about the planet in the days before the telescope was invented.

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

Addendum

The sky low in the west

Venus, Pleiades, Aldebaran with the Hyades star cluster and Orion are seen in the west at 9:45 p.m. April 24, 2018. Venus is south of the Pleiades. Created using Stellarium.

Venus and the Pleiades with grid

A closer look at Venus and the Pleiades with the coordinate grid added. The lines that run from upper right to lower left are lines of right ascension, analogous to longitude lines on the Earth. To the upper right is north and lower left is south. The other lines are those of declination. Like latitude lines on the Earth, they run east and west. Created using Stellarium.

Advertisements

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.

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.

04/21/2017 – Ephemeris – Mars is passing south of the Pleiades today

April 21, 2017 Comments off

Ephemeris for Friday, April 21st.  The Sun rises at 6:47.  It’ll be up for 13 hours and 47 minutes, setting at 8:35.  The Moon, 2 days past last quarter, will rise at 4:54 tomorrow morning.

Mars in its ever eastward trek through the constellations of the Zodiac is now just south of the Pleiades or Seven Sisters star cluster in the western evening twilight.  By 10 p.m. Mars will be 10 degrees above the western horizon.  That’s the width of a fist held at arm’s length.  Because of our location on the Earth, the setting sky is tilted, so Mars being south of the Pleiades is to the lower left of it.  The bright star Aldebaran, now brighter than Mars is to the left of it with the V-shaped star cluster called the Hyades, in mythology, half sisters of the Pleiades, filling out the face of Taurus the bull.  Mars will finally be overtaken by the Sun on July 26th.  After that it will spend more than a year to come closer to us than at any time since August 2003.

First star party of the year at the Sleeping Bear Dunes National Lakeshore

Tomorrow night the Rangers of the Sleeping Bear Dunes National Lakeshore and the Grand Traverse Astronomical Society will host a Star Party at the Dune Climb featuring the planet Jupiter, and the stars of spring.  It starts at 9 p.m.

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

Addendum

Mars passes the Pleiades

Mars and the Pleiades at 10 p.m. April 21, 2017. Aldebaran and the Hyades which is the face of Taurus the bull is to the left of them. Created using Stellarium.

Note that the nebulosity in the Pleiades exists, but is not visible to the naked eye.

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.

12/08/2016 – Ephemeris – Aldebaran, the follower

December 8, 2016 Comments off

Ephemeris for Thursday, December 8th.  The Sun will rise at 8:07.  It’ll be up for 8 hours and 54 minutes, setting at 5:02.  The Moon, 1 day past first quarter, will set at 2:26 tomorrow morning.

The central constellation of winter, Orion, is low in the east-southeast at 9 p.m.  Above it is Taurus the bull.  The bright orange star in Taurus is Aldebaran.  Aldebaran appears at the bottom left tip of a letter V group of stars lying on its side that is the face of the bull.  Aldebaran isn’t actually part of the group, called the Hyades star cluster.  The cluster is about 151 light years away, while Aldebaran is a bit less than half that.  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 350 times brighter than the Sun.  Next Monday night the 12th, the Moon will pass in front of Aldebaran in an event called an occultation I’ll have more information on it then.  The name Aldebaran means The Follower, since it follows the Pleiades across the sky as the Earth rotates.

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

Addendum

Aldebaran

Aldebaran in the ‘V’ shape of the Hyades (The face of Taurus the bull) with the Pleiades above. Created using Stellarium.

11/28/2016 – Ephemeris – The Hyades the star cluster in the face of Taurus the bull

November 28, 2016 Comments off

Ephemeris for Monday, November 28th.  The Sun will rise at 7:57.  It’ll be up for 9 hours and 7 minutes, setting at 5:04.  The Moon, 1 day before new, will rise at 7:45 tomorrow morning.

Rising in the east now is the bright star Aldebaran an orange star that’s at one end of the sideways letter V of stars that is the head of Taurus the bull.  Above it is the jewel-like Pleiades or Seven Sisters star cluster.  There’s more to Taurus, like it’s freakishly long horns and front part of its body.  But you can say you’ve seem Taurus, if you can spot his face.  That V of stars is actually a star cluster called the Hyades, and in Greek Myth were the half-sisters of the Pleiades, also fathered by the god Atlas.  Both the Hyades and Pleiades are being pursued by Orion, which as Robert Frost put it is throwing a leg over the eastern horizon at 8 to 9 pm.  He isn’t the only one following the Pleiades, the name Aldebaran means “The Follower”.

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

Addendum

the Hyades, Taurus, Orion and the Pleiades

An animation showing the Hyades, Taurus, Orion and the Pleiades. Created using Stellarium and GIMP.  Click on image to enlarge.

Closeup of the Hyades and the Pleiades

Closeup of the Hyades and the Pleiades. Created using Stellarium.