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Ephemeris: 10/29/2024 – A star for Halloween

October 29, 2024 Comments off

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

Algol Finder Animation
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.

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.

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

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

Categories: Ephemeris Program, Observing, Variable Star Tags: , , ,

Ephemeris: 01/09/2024 – Betelgeuse, Betelgeuse, nope I’m not saying it again

January 9, 2024 Comments off

Jan 9. This is Ephemeris for Tuesday, January 9th. Today the Sun will be up for 9 hours and 1 minute, setting at 5:20, and it will rise tomorrow at 8:18. The Moon, 2 days before new, will rise at 8:04 tomorrow morning.

The constellation Orion has two first magnitude stars, the most famous of these is Betelgeuse. It is a red supergiant star in Orion’s shoulder. Its name actually means Armpit of the Central One. Betelgeuse is about 500 light years away, and it is many hundreds of thousands of times brighter than the Sun, and it’s thought to be almost as big as the orbit of Jupiter. For all its size it’s only about 20 times the mass of the Sun. Some call it a red-hot vacuum. Betelgeuse has been interesting lately, first dimming for a period of time and now somewhat brighter than normal. Astronomers are wondering what’s going on with it. Betelgeuse is a type of star that will end with the supernova explosion. The question is when. Perhaps sometime in the next 100,000 years.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT –5 hours). They may be different for your location.

Addendum

Orion's named stars
Orion’s named stars. Betelgeuse means “Armpit of the Central One”. Bellatrix means “Female warrior”. The names of the belt stars refer to belt or girdle, Rigel refers to Orion’s foot. Saiph means sword, however Orion’s sword is the line of three stars below the belt stars. In binoculars, there’s more than three stars here. Around the second “star” of the sword is the Great Orion Nebula, barely visible here. Created using Stellarium.
Light Curve Betelgeuse 2017 to 2023
Brightness measurements of Betelgeuse from the AAVSO from 2017 to 2023 showing a big dip around January 2020. Betelgeuse has a normal, approximately 400 day, variability cycle and superimposed on this was the big dip in brightness in January 2020. AAVSO = American Association of Variable Star Observers.
Betelgeuse before and after dimming
This comparison image shows the star Betelgeuse before and after its unprecedented dimming. The observations, taken with the SPHERE instrument on ESO’s Very Large Telescope in January and December 2019, show how much the star has faded and how its apparent shape has changed. Credit: European Southern Observatory (ESO)/M. Montargès et al.
Categories: Ephemeris Program, Observing, Variable Star Tags: ,

Ephemeris: 10/30/2023 – Just in time for Halloween – Algol the Demon Star

October 30, 2023 Comments off

This is Ephemeris for Monday, October 30th. Today the Sun will be up for 10 hours and 16 minutes, setting at 6:34, and it will rise tomorrow at 8:19. The Moon, 2 days past full, will rise at 7:29 this evening.

Not all the ghosts and goblins out tomorrow night 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. 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 these names 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 its dimmest at 10:12 p.m. this Wednesday, November 1st.

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 predictions of the minima of Algol for your time zone and for Universal Time (UT) go here: http://www.astropical.space/algol.php

Algol Finder Animation
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.
Perseus and the head of Medusa from the 1690 Uranographia by Johannes Hevelius.
Perseus and the head of Medusa from the 1690 Uranographia by Johannes Hevelius. Note that the image is mirror reversed. This mimicked the image on a celestial globe, looking from outside the globe. Note a couple of extra constellations: a small triangle below Triangulum, and Musca the fly. There is a Musca constellation in the southern hemisphere. This image was found with the article on Algol on Wikipedia.
Eclipsing Binary Star
Animation of an eclipsing binary star like Algol. Credit: Wikimedia Commons h/t Earth and Sky.
Categories: Constellations, Ephemeris Program, Mythology, Variable Star Tags: , ,