10/31/2022 – Ephemeris – The perfect Halloween star

This is Bob Moler with Ephemeris for Halloween, Monday, October 31st. Today the Sun will be up for 10 hours and 13 minutes, setting at 6:32, and it will rise tomorrow at 8:20. The Moon, 1 day before first quarter, will set at 12:02 tomorrow morning.

Not all the ghosts and goblins out tonight will be children. One is out just about every night because it’s a star. Its name is Algol, from the Arabic for Ghoul Star or Demon Star. It’s normally the second-brightest star in the constellation Perseus the hero, visible 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. The star got the name before astronomers discovered what was really wrong with it. They found out that it does a slow wink about every two days, 21 hours because Algol is two stars that eclipse each other. Her next evening wink will be dimmest at 10:25 p.m. November 19th.*

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

Addendum

*For the broadcast, the source for the Algol minimum brightness time was the Stellarium app. For whichever date the sky is displayed for and Algol is clicked on, among the data for the star that is displayed is next minimum light. However, in double-checking the times with those posted in Sky & Telescope magazine after I recorded the program, it turns out to be 3 hours 46 minutes early, so minimum light would be at 1:36 am on November 17th. At the time given then, the eclipse would just be starting. The actual first eclipse minimum in the evening in November would be at 10:25 pm on the 19th. I hope it’s clear on the night of the 16/17th to see which prediction is right. In the past, S&T was accurate, or accurate enough.

Perseus, Cassiopeia, Andromeda with Algol finder animation for Autumn evenings. Click on the image to enlarge it. Created using Stellarium and GIMP.

Perseus and the head of Medusa from the 1690 Uranographia by Johannes Hevelius. Note that the captions in the image are as seen in a mirror. Early star representations were painted on a globe, a celestial sphere, so the stars and constellations were shown as seen from the outside. A God’s eye view. Early printed star charts simply kept the convention. I reversed the image, so it is seen from inside the celestial sphere. An Earthly view to match the sky as we see it. The image was found with the article on Algol on Wikipedia.

Animation of an eclipsing binary star like Algol. Credit: Wikimedia Commons h/t Earth and Sky

10/17/022 – Ephemeris – Andromeda, damsel in distress

This is Ephemeris for Monday, October 17th. Today the Sun will be up for 10 hours and 53 minutes, setting at 6:54, and it will rise tomorrow at 8:02. The Moon, at last quarter today, will rise at 12:18 tomorrow morning

In the east at 9 this evening can be found a large square of stars, the Great Square of Pegasus the upside down flying horse. The square is standing on one corner. What looks like its hind legs stretching to the left from the left corner star is another constellation, Andromeda the chained princess. She is seen in the sky as two nearly horizontal but diverging curved strings of stars that curve upward. She was doomed due to her mother, Queen Cassiopeia’s boasting, which angered the god Poseidon. She was rescued by the hero Perseus, a nearby constellation, riding his steed Pegasus. Andromeda’s claim to scientific fame is the large galaxy seen as a faint fuzzy spot with the naked-eye just above the upper line of stars. The Great Andromeda Galaxy is two and a half million light years away.

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

Addendum

Andromeda finder animation looking east at 9 pm tonight, October 17, 2022. The left corner star of the Great Square of Pegasus is called Alpheratz, and actually belongs to Andromeda. The faint fuzzy spot labeled M31 is the Great Andromeda Galaxy, the Milky Way’s large neighbor. I’ll talk more about it tomorrow. Click on the image to enlarge it. Created using Stellarium and GIMP.

I’ve related Andromeda’s story in my post The Great Star Story of Autumn.

09/27/2022 – Ephemeris – Finding the constellation of Perseus the hero

This is Ephemeris for Tuesday, September 27th. Today the Sun will be up for 11 hours and 54 minutes, setting at 7:30, and it will rise tomorrow at 7:37. The Moon, 2 days past new, will set at 8:28 this evening.

Close to the horizon, but rising in the northeast in the evening, is the constellation of Perseus the Greek hero, holding as his prize the severed head of Medusa. To me, the stars don’t seem to match the figure in the stars. It’s either the Greek letter pi (π) tilted to the left or the cartoon roadrunner running up the sky. Perseus’ brightest star is Mirfak in the middle of the top of the letter π, or back of the roadrunner. Using a pair of binoculars to look towards Mirfak, one can see many more stars, just below naked eye visibility near it. It’s a very loose star cluster called the Alpha (α) Persei Association, α Persei being a catalog designation for Mirfak. And Mirfak is actually in the association. Unlike some bright stars, who are just foreground stars.

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

Addendum

For my take on the mythology featuring Perseus, see The Great Star Story of Autumn. It’s way too long for my short radio program. For Hollywood’s treatment of the story, see Clash of the Titans.

Perseus finder using the animated GIF to show the star field, constellation lines and names, and Perseus as art. Cassiopeia is included as a means to find the dimmer Perseus below it on autumn evenings. Algol, another important star and the second-brightest star of Perseus, is also labeled. I normally cover it around Halloween, but if you can’t wait, type Algol in the search box at the upper right. Created using Stellarium, LibreOffice Draw, and GIMP.

The Alpha Persei Association. The brightest star is Mirfak (Alpha Persei). This is a small section of a photograph taken February 18, 2017, Canon EOS Rebel T5, 121 seconds, f/3.5, 18 mm fl., ISO 3200. Credit Bob Moler.

10/28/2021 – Ephemeris – The spookiest star in the sky

This is Ephemeris for Thursday, October 28th. Today the Sun will be up for 10 hours and 21 minutes, setting at 6:36, and it will rise tomorrow at 8:17. The Moon, at last quarter today, will rise at 12:31 tomorrow morning.

We are getting down to the spookiest time of the year, with Halloween on Sunday, so it’s time to talk about the spookiest star in the sky, Algol the Ghoul or Demon Star. It’s in the constellation of Perseus the hero, now rising in the northeastern sky. The constellation itself looks like the Greek letter pi, or like the cartoon Roadrunner with its long legs. Algol is the second brightest star in the constellation, near the Roadrunner’s leading foot. That’s where the eye of the severed head of Medusa, that Perseus is carrying. It’s still winking, once every 2 days and 21 hours*. Tonight it will be in the deepest part of its wink at 8:43 pm. It will take about three hours to recover its usual brightness. I recall that the ancient Chinese weren’t fond of that star either.

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

* More specifically, 2 days, 20 hours, 49 minutes on average and altered by Earth’s changing distance from the star due to its orbit of the Sun.

Addendum

Algol Finder Animation for around 8 pm in the later part of October and early November (7 pm after the EST time change on the first Sunday in November). Created using Stellarium and GIMP.

Algol is an eclipsing binary star, where one star eclipses the other.

Animation of an eclipsing binary star like Algol. Credit: Wikimedia Commons h/t Earth and Sky

09/28/2021 – Ephemeris – Andromeda, a damsel in distress

This is Bob Moler with Ephemeris for Tuesday, September 28th. Today the Sun will be up for 11 hours and 50 minutes, setting at 7:28, and it will rise tomorrow at 7:38. The Moon, at last quarter today, will rise at 11:46 this evening.

In the east at 9 this evening can be found a large square of stars, the Great Square of Pegasus the flying horse. The square is standing on one corner. What looks like its hind legs stretching to the left from the left corner star is another constellation, Andromeda the chained princess. She is seen in the sky as two diverging curved strings of stars that curve upward. She was doomed due to her mother, Queen Cassiopeia’s boasting, which angered the god Poseidon. She was rescued by the hero Perseus, a nearby constellation, riding his steed Pegasus. Andromeda’s claim to astronomical fame is the large galaxy seen with the naked-eye just above the upper line of stars. The Great Andromeda Galaxy is two and a half million light years away.

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

Addendum

Andromeda finder animation surrounded by the other constellations in her story, except the monster, which will rise later. Click on the image to enlarge it. Created using Stellarium and GIMP.

Great Andromeda Galaxy finder chart. This image shows the galaxy almost to its fullest extent. In the finder animation above, the galaxy looks pretty much as it would to the naked eye. Click on the image to enlarge it. Created using Stellarium.

Astronomers often refer to this galaxy as M 31 for short. It was the 31st entry in Charles Messier’s catalog of objects that could be confused as being comets by comet hunters like himself. It was added in 1764. He didn’t care what these fuzzy objects were, just that they didn’t move against the background stars. Actually, M 31 is in the background. The stars are in the foreground, in our Milky Way Galaxy.

 

11/13/2020 – Ephemeris – Finding Perseus the hero in the stars

This is Ephemeris for Friday, November 13th. Today the Sun will be up for 9 hours and 38 minutes, setting at 5:16, and it will rise tomorrow at 7:39. The Moon, 2 days before new, will rise at 6:41 tomorrow morning.

About a third the way from the east northeastern horizon to the zenith at 8 p.m. and below the letter W shaped constellation of Cassiopeia the queen is Perseus the hero. It’s kind of an odd shape for a hero, To me it looks kinda like the cartoon roadrunner. To those who’re mathematically inclined its shape is also like the Greek letter pi on its side. It’s two brightest stars are Mirfak and Algol the demon star, the still winking eye of Medusa. Look at the area around Mirfak with binoculars and a large group of stars just below naked eye visibility will appear. It’s called the Alpha Persei Association. That’s because Mirfak is also known as Alpha Persei. The group is about 560 light years away, which means, though close, are farther away than the Pleiades, which is below and to the right of them.

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

Addendum

Perseus finder animation for 8 pm November 13, 2020. The star Mirphak in the image is generally spelled Mirfak and is also designated Alpha Persei.

The Alpha Persei Association. The brightest star is Mirfak (Alpha Persei). This a an extreme crop from a photograph taken February 18, 2017, Canon EOS Rebel T5, 121 seconds, f/3.5, 18mm fl., ISO 3200. Credit Bob Moler.

10/30/2020 – Ephemeris – The spookiest star in the sky

This is Ephemeris for Friday, October 30th. Today the Sun will be up for 10 hours and 14 minutes, setting at 6:33, and it will rise tomorrow at 8:20. The Moon, 1 day before full, will set at 8:08 tomorrow morning.

With the COVID virus around probably the only spooky thing out tomorrow night will be the star Algol. It’s out every night actually. It’s name, Algol, is from the Arabic for Ghoul Star or Demon Star. The Chinese had a name for it that meant “piled up corpses”. It’s normally the second brightest star in the constellation Perseus the hero, visible 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 winking eye. The star got the name before astronomers found out what was wrong with it. They found out that it does a slow wink every two days, 21 hours. That’s because Algol is two stars that eclipse each other. Her next evening wink will be at its dimmest at 12:11 am November 13th. Remember, daylight time ends on Sunday.

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

Addendum

Algol at 7:30 p.m. on Halloween, in a modern portrayal. Created using Stellarium.

Animation of an eclipsing binary star like Algol. Credit: Wikimedia Commons h/t Earth and Sky

Algol Minima through November 24th 2020. Click on the image to enlarge. Eclipses are about 10 hours long with 5 hours of dimming and another 5 hours to regain brightness. Source: Insula Astra http://www.astropical.space/algol.php.

 

 

08/11/2020 – Ephemeris – Tonight is the peak of the Perseid Meteor shower

This is Bob Moler with Ephemeris for Tuesday, August 11th. Today the Sun will be up for 14 hours and 12 minutes, setting at 8:53, and it will rise tomorrow at 6:42. The Moon, at last quarter today, will rise at 12:46 tomorrow morning.

This evening and tomorrow morning we should see the peak of the Perseid Meteor Shower. There is the expected broad peak of the shower which for us is after sunrise. However the meteoroid stream isn’t monolithic. Each pass of the comet in the inner solar system superimposes its debris on the general stream, so we will have increased activity all night tonight and even into the next few mornings. In general Perseid meteors will be seen to come from the northeast. The evening view will be not hampered by the Moon until it rises at 12:46 am which will drown out the dimmer meteors. The best time to view is from about 10 or 10:30 pm to 12:46 am. The Perseids are the most active meteor shower visible in warm weather, with a possible over 50 meteors per hour.

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

Addendum

My best Perseid photo. From the 1970’s.

Perseid radiant at 11 pm, August 11th at the top of the constellation of Perseus, below the W shaped constellation of Cassiopeia. Click on the image to enlarge. Created using Stellarium.

Ephemeris Extra – The Great Star Story of Autumn

The constellations of the great star story of autumn. Looking southeast on October 31 at 10 p.m. Created using Stellarium.

The great star wheel of the sky rolls on. In the evening sky gone are the stars of spring, and going are the southern stars of summer. In the morning sky before sunrise the stars of an early winter evening.

A constant in both skies are the stars of autumn: rising in the evening and setting in the morning. In no other part of the sky do so many constellations take part in a single story

The constellations, as seen above are Cepheus, Cassiopeia, Andromeda, Perseus, Pegasus, and Cetus. And their story goes like this:

In distant Ethiopia a crisis was brewing. King Cepheus and Queen Cassiopeia were at wits end as how to stop it. A giant sea monster named Cetus was ravaging the country’s coastal cities destroying them and devouring the inhabitants.

The king and queen consulted the temple oracle as to what happened and what could be done to save their country. The oracle intoned gravely that the fault was Cassiopeia’s. Suddenly the queen knew what happened. Cassiopeia was very beautiful and she had vainly boasted to all who could hear that she was more beautiful than even the sea nymphs, the lovely daughters of the sea god Poseidon.

The sea nymphs had heard of Cassiopeia’s boast and complained to their father. Poseidon, like any father, was angered, and being a god was able to do something about. Being a god means never having to say your sorry when you do something really mean. He loosed the monster Cetus upon the Ethiopians.

The oracle said that to appease the monster and Poseidon Cassiopeia would have to sacrifice her daughter the Princess Andromeda to the monster. That is how young Andromeda was chained to the rocks on the sea shore to await her doom…

Far away in ancient Greece a wedding was about to take place between the beautiful Princess Danaë and King Polydectes. Danaë’s son Perseus, fathered by Zeus, but that’s another story, wasn’t too happy about the proposed union, and Polydectes wanted the boy gone.

When Perseus asked Polydectes what he wanted for a wedding gift, he said, “I want the head of Medusa.” The boy immediately and foolhardedly agreed to get it for him.

Merdusa, it turns out, was one of three sisters, the Gorgons, who had snakes for hair. They were so ugly that one glimpse of them would turn the beholder to stone. Medusa was the only mortal one.

Luckily Perseus had the favor of the god Hermes and Athene. They armed him with Hermes’ winged sandals, a helmet that made him invisible, a pouch that would expand to hold an object of any size, a shiny mirror shield, and a sword.

Thus armed Perseus was told to find the Graiae or the gray women, who could tell him where the lair of the Gorgons was. They were three in number and shared but one eye and one tooth among them which they passed from one to another to use.

The Graiae refused to help Perseus. But he was able to force them to help by snatching their one eye while it was being passed from one to another. They told him that the Gorgons dwelt in the shore of the river Ocean at the edge of the world in perpetual twilight.

In approaching the lair of the Gorgons Perseus put on the helmet of invisibility. He approached Medusa stepping backwards, cautiously peering only at Medusa’s indistinct image in his shield. Perseus then swept his sword in a backhanded way and managed to sever Medusa’s head. It is said that Athene guided his hand.

Amazingly, springing full grown from Medusa’s blood was the winged white stallion Pegasus. After placing Medusa’s head in the pouch, Perseus mounted Pegasus for the trip home.

Cruising high in the sky over the Ethiopian coast Perseus spotted a horrific sight. There far below the beautiful Andromeda, in chains; her screams reaching his ears. Then he spotted why she was screaming. A short distance away, crawling out of the surf was the monster Cetus, heading towards Andromeda. Perseus immediately sizes up the situations and swooped with Pegasus down to a spot between Andromeda and the monster. Then, burying his head in his shoulder drew out the head of Medusa from the pouch and held it in front of Cetus. The head was as lethal in death as in life, and the monster was promptly turned to stone. Replacing the head in the pouch, Perseus freed Andromeda. They flew off to, well supposedly, live happily ever after.

Oh yes. Perseus did present the head of Medusa to his step father Polydectes. He, of course, was also turned to stone when he laid eyes on it.

There you have it a story connecting the autumn constellations of Cepheus, Cassiopeia, Andromeda, Perseus, Pegasus and Cetus.

Cepheus is a dim church steeple of a constellation. Its dim star Delta is a variable star, the prototype of an important class of distance measuring stars called Cephieds in its honor. Cassiopeia is the famous W shaped constellation that along with Cepheus doesn’t set at our latitude.

Perseus looks to me more like the cartoon roadrunner than a hero. As the ancients saw him, he is holding the head of Medusa, whose still glittering eye is the star Algol, a variable star which ghastly winks at us every 2 days and 21 hours.

Andromeda’s modern claim to fame is the great galaxy that lies beyond her stars, the Great Andromeda Galaxy which has the designation M31. The galaxy is faintly visible to the unaided eye on dark nights. The farthest you can see without optical aid. The galaxy lies some 2.5 million light years away.

Pegasus can be easily found by the square of stars the form his body. It’s called the Great Square of Pegasus.

What can be said about Cetus. It now represents a whale, not a monster. Its star Mira, which means “Wonderful”, slowly varies in brightness over 330 days from a star barely visible in binoculars to a 2nd or 3rd magnitude star.

Look up on an autumn evening and recapture the wonder the ancients had as they looked upward at the stars.

11/05/2018 – Ephemeris – Cassiopeia the Queen

Ephemeris for Monday, November 5th. The Sun will rise at 7:26. It’ll be up for 9 hours and 59 minutes, setting at 5:26. The Moon, 2 days before new, will rise at 6:00 tomorrow morning.

The stars of the autumn skies are replacing the summer stars from the east. Look in the northeastern sky by 7 p.m. and you can find the W shaped constellation of Cassiopeia the queen. Cassiopeia is so far north that it never sets for us in Michigan. It is opposite the pole star Polaris from the Big Dipper. There’s a dim star that appears above the middle star of the W which turns it into a very crooked backed chair, Cassiopeia’s throne. Above and left of Cassiopeia is a dim upside down church steeple shaped constellation of Cepheus the king, her husband. The Milky Way flows through Cassiopeia toward the northeastern horizon and through the constellation of Perseus the hero, which kind of looks, to me anyway, like the cartoon roadrunner.

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

Addendum

Cassiopeia and constellations along the Milky Way in the northeast these autumn evenings. (8 p.m. November 5). Click on image to enlarge. Created using Stellarium and GIMP.