Archive
Ephemeris: 01/16/2026 – Comparing Orion’s two brightest stars
This is Ephemeris for Friday, January 16th. Today the Sun will be up for 9 hours and 13 minutes, setting at 5:29, and it will rise tomorrow at 8:15. The Moon, 2 days before new, will rise at 7:54 tomorrow morning.
Orion’s two brightest stars are kind of the same but different. Let me explain. Betelgeuse is a red giant star, extremely massive, maybe 14 to 19 times the sun’s mass. It is somewhere between 8 and 14 million years old, which compared to the sun is just a baby, except it is so massive that it is in the last million or so years of its life. Rigel is a bluish white and a bit more massive, about 21 times the mass of the sun, and maybe 8 million years old. It has used most of the hydrogen in its core, and is beginning to transition into its final years which is a few more millions of years. So it’s not as far along in its evolution as Betelgeuse and has not bloated out and turned red. Betelgeuse is 500 light years away, while Rigel is almost 900.
The astronomical event times given in this blog are for the Traverse City/Interlochen area of Michigan (Lat 44.7° N, Long 85.7° W; EST, UT – 5 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 01/30/2025 – What’s up with Betelgeuse
This is Bob Moler with Ephemeris for Thursday, January 30th. Today the Sun will be up for 9 hours and 45 minutes, setting at 5:49, and it will rise tomorrow at 8:02. The Moon, 1 day past new, will set at 7:20 this evening.
The constellation Orion is in the southeast at 8 PM, so what’s up with Betelgeuse. Betelgeuse is the bright reddish upper leftmost star of the torso of Orion the hunter, it’s in his shoulder. Betelgeuse has been acting up lately. In 2019 and 2020 Betelgeuse had dimmed significantly. Astronomers didn’t know why at the time, but found out later that it ejected a large cloud of gas and dust which blocked the light from the star. Since then Betelgeuse has increased its brightness significantly, so it’s much brighter than normal. Again, we don’t exactly know why. Some have speculated that Betelgeuse is will soon go supernova. We’ve known that for a while, but soon is measured in hundreds of thousands of years. So astronomers are keeping an eye on Betelgeuse to see what happens next.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EST, UT – 5 hours). Times will be different for other locations.
Addendum
Ephemeris: 03/07/2024 – There’s a unicorn in there somewhere
This is Bob Moler with Ephemeris for Thursday, March 7th. Today the Sun will be up for 11 hours and 30 minutes, setting at 6:39, and it will rise tomorrow at 7:06. The Moon, 3 days before new, will rise at 6:35 tomorrow morning.
The constellation of Monoceros the unicorn is located in an area of sky to the left of Orion so it’s in the south at 8 pm, inside the Winter Triangle of stars, Betelgeuse in Orion; Sirius in the Great Dog, Canis Major; and Procyon in Canis Minor. If you don’t see anything there, it’s OK. Nobody sees real unicorns any more anyway. Are there any real unicorns? Anyway, there’s a great number of nebulae here in the Milky Way that runs through it, which unfortunately are too faint to be seen with amateur telescopes. However, it is a gold mine for amateur astronomers who are also astrophotographers using time exposures to record the faint nebulae here, including the famous Rosette Nebula!
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
Ephemeris: 01/09/2024 – Betelgeuse, Betelgeuse, nope I’m not saying it again
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
Ephemeris: 11/13/2023 – Betelgeuse is acting weird again
This is Ephemeris for Monday, November 13th. Today the Sun will be up for 9 hours and 40 minutes, setting at 5:16, and it will rise tomorrow at 7:38. The Moon is new today, and won’t be visible.
The constellation Orion is rising early in the evening now so what’s up with Betelgeuse. Betelgeuse is the bright reddish upper leftmost star of the torso of Orion the hunter, it’s in his shoulder. Betelgeuse has been acting up lately. In 2019 and 2020 Betelgeuse had dimmed significantly. Astronomers didn’t know why at the time, but found out later that it ejected a large cloud of gas and dust which blocked the light from the star. Now in the last year Betelgeuse has increased its brightness significantly, so it’s much brighter than normal. Again, we don’t exactly know why. Some have speculated that Betelgeuse is about ready to go supernova. We’ve known that for a while, but soon is measured within hundreds of thousands of years. So astronomers are keeping an eye on Betelgeuse to see what happens next.
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
Ephemeris: 07/26/2023 – Let’s find out where the naked-eye planets have wandered off to this week
This is Bob Moler with Ephemeris for Wednesday, July 26th. Today the Sun will be up for 14 hours and 53 minutes, setting at 9:15, and it will rise tomorrow at 6:23. The Moon, 1 day past first quarter, will set at 1:08 tomorrow morning. | Let’s find out where the naked-eye planets have wandered off to this week. Venus is our hard to find Evening Star, seen very low in the west in evening twilight by 9:45 pm. It will set at 10:11 pm, Mercury might be spotted to Venus’ right and a bit above. The red planet Mars is pretty much lost in the evening twilight, above and left of Venus. Saturn will rise at 10:38 pm. And by 5:30 am, or a bit less than an hour before sunrise tomorrow, it will appear in the south-southwest, the brightest “star” in that direction. Its above the bright star Fomalhaut, normally the loneliest bright star in the sky. Jupiter will be in the east-southeast at that hour. Jupiter is the brightest star-like object in the morning sky now, near some of the bright stars of a winter’s evening.
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
01/10/2023 – Ephemeris – The constellation of Orion the hunter, unlucky in love
This is Bob Moler with Ephemeris for Tuesday, January 10th. Today the Sun will be up for 9 hours and 3 minutes, setting at 5:22, and it will rise tomorrow at 8:18. The Moon, halfway from full to last quarter, will rise at 9:01 this evening.
Before the Moon rises tonight, we will have two hours of darkness. Winter’s central constellation, Orion the hunter, doesn’t need the Moon to be absent to see its principal stars. He’s in the southeast before the Moon rises with red Betelgeuse in one shoulder and dimmer Bellatrix on the other, Saiph at one knee and bright blue-white Rigel at the other. Between his shoulders and knees runs his belt of three stars in a line. Above Betelgeuse, he is holding a club aloft and from Bellatrix he holds a lion skin shield to defend himself from the charge of Taurus the bull, above and right of him. I consider him a hard luck hero, with three different stories on how he died. Unlucky in love, he’s consigned to chase the Seven Sisters of the Pleiades throughout eternity.
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 finder animation with Mars. First, showing the unannotated sky looking southeast at Orion. Second, Orion with lines and labels of the stars at the corners of his body, and other bright stars in the view, plus the Pleiades and bright planet Mars, that’s just happening to be passing through this year. Third, the constellation art for Orion and Taurus the bull. Created using Stellarium, LibreOffice Draw and GIMP.
Here are the three stories of how Orion died: One: Orion raped the goddess Artemis, and so she killed him. Two: Orion was betrothed to Artemis, but her twin brother Apollo was jealous and caused her to kill him in a hunting “accident”. Three: Orion was killed by the sting of a scorpion, which is the reason Orion and Scorpius are never in the sky at the same time.
02/22/2022 – Ephemeris – The Winter Triangle
This is Ephemeris for Tuesday, February 22nd. Today the Sun will be up for 10 hours and 49 minutes, setting at 6:21, and it will rise tomorrow at 7:30. The Moon, 1 day before last quarter, will rise at 1:26 tomorrow morning.
I’ve talked about the Winter Circle of bright stars already this winter, but some other astronomers talk about the Winter Triangle. The stars involved are Betelgeuse in the hunter Orion, Sirius in Canis Major, Orion’s large hunting dog, and Procyon in Canis Minor, his other small hunting dog. These three stars enclose a rather blank piece of sky with the faint Milky Way running through it and the almost invisible constellation of Monoceros the unicorn. The Summer Triangle has three bright stars with no other close competition. The Winter Triangle has four other bright stars near it. Any three of these would make a nice triangle. One of these constellations, Canis Minor, is tiny with Procyon and one other star. It makes me think of a dachshund, or maybe, if I’m hungry, a hot dog.
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
The Winter Triangle. It encloses a pretty blank space where Monoceros the unicorn lies. Created using Stellarium with my annotations for the Winter Triangle.
01/31/2022 – Ephemeris – The winter circle of bright stars
This is Ephemeris for Monday, January 31st. Today the Sun will be up for 9 hours and 47 minutes, setting at 5:50, and it will rise tomorrow at 8:01. The Moon, 1 day before new, will rise at 8:48 tomorrow morning.
The winter skies are blessed with more first magnitude stars than any other season. Six of these stars lie in a large circle centered on the seventh, It’s called the Winter Circle. This circle is up in the evening. Starting high overhead is yellow Capella in Auriga the charioteer. Moving down clockwise is orange Aldebaran in the face of Taurus the Bull. Then down to Orion’s knee, we find blue-white Rigel. Down and left is the brightest star of all the brilliant white Sirius the Dog Star in Canis Major, lowest of these stars in the south-southeast. Moving up and left is white Procyon in Canis Minor, Above Procyon is Pollux in Gemini, the twins. All these are not quite centered on Betelgeuse, the bright red star in Orion’s shoulder.
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
The bright stars of winter arrayed in a not so accurate circle. Some call it the Winter Hexagon. These stars are what make the winter sky so brilliant on the rare clear night in winter. Created using Stellarium.
01/06/2022 – Ephemeris – The named stars of Orion
This is Ephemeris for Thursday, January 6th. Today the Sun will be up for 8 hours and 58 minutes, setting at 5:18, and it will rise tomorrow at 8:19. The Moon, 3 days before first quarter, will set at 10:07 this evening.
Orion is still on an angle, leaning to the left, at 8 to 9 pm in the southeastern sky. It’s seven brightest stars have names from antiquity, and some of them are familiar. Starting from the top left, the bright reddish star is famous Betelgeuse. The top right star is Bellatrix, a name familiar to Harry Potter fans. The three stars of his belt, from bottom to top, are Alnilam, Alnitak, and Mintaka. The final bottom two stars from left to right are Saiph, pronounced “safe”. And blue-white Rigel, usually the brightest star of the constellation. These are the stars of Orion’s shoulders, belt and knees. He has other stars that delineate an arm with an upraised club and an arm holding a lion skin shield and a sword hanging from his belt.
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. Betelgeuse means “Armpit”. Bellatrix means “Female warrior”. The names of Orion’s 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.
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