Archive
Ephemeris: 08/23/2024 – The dimmest star of the Summer Triangle is really the brightest
This is Ephemeris for Friday, August 23rd. Today the Sun will be up for 13 hours and 39 minutes, setting at 8:34, and it will rise tomorrow at 6:56. The Moon, 3 days before last quarter, will rise at 10:29 this evening.
This evening when it gets dark enough the bright star Deneb in Cygnus the swan will be very high in the east. Deneb is the dimmest star of the Summer Triangle. Of the other stars of the triangle, Vega is nearly overhead, while Altair is lower in the south-southeast. Deneb’s apparent magnitude, or brightness as seen from Earth, makes it the dimmest of the three bright stars. Its vast distance of possibly 2,600 light years is over 100 times the distance of Vega. If brought as close as Vega, Deneb would be as at least as bright as the quarter moon. It is possibly as bright as 200 thousand Suns; and a huge star, possibly as large in diameter as the orbit of the Earth. For all this it is only 19 or so times the mass of the Sun.
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
Ephemeris: 08/13/2024 – Antares and the Moon
This is Ephemeris for Tuesday, August 13th. Today the Sun will be up for 14 hours and 7 minutes, setting at 8:50, and it will rise tomorrow at 6:44. The Moon, 1 day past first quarter, will set at 12:41 tomorrow morning.
The Moon tonight will have a companion. Just to the left of it will be a star. That star may not look very bright because it is overpowered by moonlight, but it is one of the brightest stars of the sky. It is Antares in Scorpius the scorpion, a red giant star. Every month for the last several years and for the next several years the moon will pass in front of that star. Unfortunately due to the timing and to the path of the Moon it doesn’t happen for any particular spot on the Earth very often. Tonight, as the Moon sets it will be approaching Antares but will appear about to pass below it at the time it sets. We will not be able to see the Moon actually cover or occult Antares from Northern Michigan until May 2028, nearly four years from now.
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
Ephemeris: 07/08/2024 – The Summer Triangle dominates the eastern sky
This is Ephemeris for Monday, July 8th. Today the Sun will be up for 15 hours and 23 minutes, setting at 9:29, and it will rise tomorrow at 6:06. The Moon, 3 days past new, will set at 11:34 this evening.
We’re two weeks into summer, and the asterism or informal constellation called the Summer Triangle can be seen in the eastern sky as it gets dark. The highest of the three bright stars is Vega in the constellation Lyra the harp, whose body is seen in a narrow parallelogram just below it. The second star of the triangle is Deneb, in Cygnus the swan, lower and left of Vega, It appears dimmer than Vega because it is by far the most distant of the three. The third star of the Summer Triangle is seen farther below and a right of Vega. It is Altair in Aquila the eagle, and the closest. Altair is 16.5 light years away, Vega is 27 light years, while Deneb may be a whopping 2,600 light years away. One light year by the way, is 6 trillion miles (9 trillion kilometers).
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
Ephemeris: 05/28/2024 – Finding Spica and Virgo
This is Ephemeris for Tuesday, May 28th. Today the Sun will be up for 15 hours and 15 minutes, setting at 9:18, and it will rise tomorrow at 6:01. The Moon, 2 days before last quarter, will rise at 2:06 tomorrow morning.
The Big Dipper, near the zenith at 10:30 pm points to several stars and constellations. It’s handle points to two bright stars. First we follow the arc of the handle to the bright orange star Arcturus, the 4th brightest nighttime star. The reason I say nighttime is that the Sun is a star also, but by definition is not out at night. The arc to Arcturus is a way to find Arcturus and a clue to its name. Arcturus, high in the south-southeast, lies at the base point of the kite shaped constellation of Boötes the herdsman. From Arcturus, straighten out the arc to a spike and one soon arrives at Spica a blue-white star in Virgo the virgin, now in the south. Spica is also sometimes pronounced ‘Speeka’.
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
Ephemeris: 05/17/2024 – The famous Big Dipper stars Mizar and Alcor
This is Ephemeris for Friday, May 17th. Today the Sun will be up for 14 hours and 55 minutes, setting at 9:07, and it will rise tomorrow at 6:10. The Moon, 2 days past first quarter, will set at 4:01 tomorrow morning.
In tonight’s sky, the Big Dipper is nearly overhead. In its handle is a star or two that are interesting. It’s the star at the bend in the handle. It’s called Mizar. Next to it, for those with good eyesight, is a dimmer star, called Alcor. The name Mizar is from the Arabic, meaning apron or cover, while Alcor means the forgotten one. Before optometrists, the ability to actually see both stars was a test for good eyesight, especially for Arabic warriors. The pair is also known as the “Horse and the Rider”. I’ve been told that some Native American tribes saw the handle stars as hunters following the Great Bear, Ursa Major, of which the Big Dipper is a part, rather than its very unnatural tail. Dim Alcor became a hunting dog.
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
Ephemeris: 05/06/2024 – The star Arcturus: Not from around here
This is Ephemeris for Monday, May 6th. Today the Sun will be up for 14 hours and 29 minutes, setting at 8:54, and it will rise tomorrow at 6:23. The Moon, 1 day before new, will rise at 5:53 tomorrow morning.
Arcturus, a red giant star in the constellation of Boötes the herdsman, is about two thirds the way up the sky in the east-southeast at 10 pm. It’s one of the earliest stars to appear in twilight, being nearly tied in brightness with Vega, a white star low in the northeast. A pointer to Arcturus is the handle of the Big Dipper, following the arc of the handle to Arcturus. Though only 37 light years away, it’s not from around here. It’s passing through the galactic disk from north to south. Arcturus is about 7 billion years old, and is about 8% more massive than our Sun. It appears to be starting its red giant phase, after running out of hydrogen to fuse into helium in its core, and is beginning to fuse the helium. It’s 25 times the size of the Sun and 170 times brighter, and a preview of our Sun when it gets that old.
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
* Hertzsprung-Russell Diagram of a star’s surface (photosphere) temperature vs luminosity. The Main Sequence is where a star lives when it is burning hydrogen, and spends most of its life.
Ephemeris: 02/05/2024 – Looking at the star Procyon
This is Ephemeris for Monday, February 5th. Today the Sun will be up for 9 hours and 59 minutes, setting at 5:56, and it will rise tomorrow at 7:56. The Moon, 3 days past last quarter, will rise at 5:44 tomorrow morning.
The star Procyon is in Orion’s little hunting dog Canis Minor, which contains only one other star. It can be found by using the shoulder stars of Orion, Bellatrix and Betelgeuse, pointing to the left and down a bit to Procyon in the evening. The word Procyon appears to mean “Before the Dog” meaning that rises before the Dog Star, Sirius, even though it is east of it. Procyon is also north of Sirius, which for observers above 30° north latitude does indeed rise before the Dog Star. It is a star like Sirius, though it’s not as bright, or white. Procyon is 11.5 light years away while Sirius is 8.4 light years away. Both have tiny white dwarf companion stars.
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: 01/22/2024 – The Dog Star’s little buddy
This is Ephemeris for Monday, January 22nd. Today the Sun will be up for 9 hours and 24 minutes, setting at 5:37, and it will rise tomorrow at 8:11. The Moon, 3 days before full, will set at 7:14 tomorrow morning.
Sirius is the brightest nighttime star and is located low in the southeast at 9 p.m. below and a bit left of Orion the Hunter. We’ve visited Sirius on Tuesday, but there is another star in the Sirius system that is practically invisible due to Sirius’ dazzling glare. Its name is Sirius B, nicknamed the Pup, alluding to Sirius’ Dog Star title. The tiny star was suspected as far back as 1834 due to Sirius’ wavy path against the more distant stars in the sky. Sirius and the Pup have 50-year orbits of each other. The Pup was first seen in 1862. It was the first of a new class of stars to be discovered, white dwarfs. The Pup is a dying star with the mass of the Sun, collapsed down to the size of the Earth after running out of hydrogen fuel in its core.
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: 01/19/2024 – Finding the Dog Star
This is Bob Moler with Ephemeris for Friday, January 19th. Today the Sun will be up for 9 hours and 18 minutes, setting at 5:33, and it will rise tomorrow at 8:13. The Moon, 2 days past first quarter, will set at 3:59 tomorrow morning.
In the evening, the great constellation of Orion the hunter can be seen to slowly move from the south-east to the south. Its large rectangle of bright stars is easily visible, even with a full moon. The three stars in a straight line, his belt, tilt downward to the left to a very bright star merrily twinkling lower in the sky. This star is called Sirius, also known as the Dog Star because it’s in the heart of Orion’s larger hunting dog, Canis Major. It is an arc light white star as seen in binoculars or telescope. It is the brightest star in the night sky, and a neighboring star, just twice the distance of the closest star to the Sun at 8.6 light years. Its name, Sirius, has nothing to do with a dog, but is from the Greek meaning scorching for its brightness and sparkling, due to its intense twinkling.
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: 01/11/2024 – Rigel, the star in Orion’s knee or is it his foot?
This is Bob Moler with Ephemeris for Thursday, January 11th. Today the Sun will be up for 9 hours and 4 minutes, setting at 5:23, and it will rise tomorrow at 8:18. The Moon is new today, and won’t be visible.
Orion’s second first magnitude star is Rigel in the lower right corner of the constellation this is a blue-white star in contrast to Betelgeuse which is a reddish star. The name Rigel is part of a phrase that means Left foot of Jauzah. Jauzah being the old name of the constellation Orion. It’s where we place Orion’s left knee now. In older drawings of the constellation, Orion has his left foot raised as if charging towards Taurus who’s charging at him. Rigel is about the same mass as Betelgeuse, though it’s nearly twice as far away at nearly 900 light years. Rigel is a quadruple star system. The bright Rigel A itself has what looks like a companion in small telescopes. That companion is actually three stars orbiting each other.
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
right-most bright star Is Rigel, a bluish white star, in contrast to Betelgeuse which has a ruddy glow. Here it looks like Betelgeuse and Bellatrix are in Orion’s shoulders and Saiph and Rigel are in his knees, with the belt star halfway in between. The word Rigel, however, means foot, and Saiph means sword. Check out the star chart below. Created using Stellarium.
Bob Moler's Ephemeris Blog 