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Ephemeris: 10/29/2024 – A star for Halloween
This is Ephemeris for Tuesday, October 29th. Today the Sun will be up for 10 hours and 17 minutes, setting at 6:34, and it will rise tomorrow at 8:18. The Moon, 3 days before new, will rise at 6:24 tomorrow morning.
Not all the ghosts and goblins out Thursday night will be children. One is out every night because it’s a star. Its name is Algol, from the Arabic for Ghoul 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 had snakes for hair so that she turned all who gazed upon her to stone. Algol is her still glittering eye. The star got this name before astronomers found out what was really wrong with it. They found out that it does a slow wink every two days, 21 hours, because it is two stars that eclipse each other. Her next 9-hour wink, is centered at 2 AM Halloween morning.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hours). Times will be different for other locations.
Addendum
Stellarium tends to show variable stars and a brightness about halfway between the brightest and dimmest magnitudes. However, Algol stays at its peak brightness most of the time, so it usually appears as bright as Mirfak which, in the image above, is to its upper left. It’s only during the eclipse that it appears dimmer than Mirfak. That’s how you can tell that Algol is in eclipse.
Here is where to go to find out when Algol is going to be in eclipse in the next week or so: http://www.astropical.space/algol.php
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
10/30/2020 – 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.
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
10/31/2016 – Ephemeris – What’s a Halloween sky without the Ghoul Star
Ephemeris for Halloween, Monday, October 31st. The Sun will rise at 8:20. It’ll be up for 10 hours and 12 minutes, setting at 6:32. The Moon, 1 day past new, will set at 7:28 this evening.
Not all the ghosts and goblins out tonight will be children. One is out every night, because it’s a star. Its name is Algol, from the Arabic for 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 2 days 21 hours because it is two very close stars that eclipse each other in that period. It did so this morning at 5:53 a.m.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
To run an app to calculate times for the minima of Algol click here: http://www.skyandtelescope.com/observing/celestial-objects-to-watch/the-minima-of-algol/ courtesy of Sky and Telescope Magazine.
Perseus with Cassiopeia and Andromeda in the northeast at 8:30 p.m. on Halloween. Created using Stellarium and GIMP.
Animation of an eclipsing binary star like Algol. Credit: Wikimedia Commons h/t Earth and Sky
10/31/2012 – Epmeneris – The Ghoul Star
Ephemeris for Halloween, Wednesday, October 31st. The sun will rise at 8:19. It’ll be up for 10 hours and 12 minutes, setting at 6:32. The moon, 2 days past full, will rise at 7:37 this evening.
Not all the ghosts and goblins out tonight will be children. One will be out every night, because it’s a star. Its name is Algol, from the Arabic for Ghoul Star or Demon Star. The Chinese had a name for it that meant a mausoleum or more ominously ‘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 very close stars that eclipse each other in that period.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The constellation Perseus in the northeast at 9 p.m. on October 31, 2012. Created using Stellarium.
Perseus and the head of Medusa from the 1690 Uranographia by Johannes Hevelius. Image found with the article on Algol in Wikipedia.
Note that this is a mirror image. The star charts in the 17th century were based on celestial globes, which represented the constellations as seen from the outside of the celestial sphere instead of from the inside. I reversed the image to match Perseus as we see him.
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