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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.
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: 10/19/2023 – The southern star of autumn – Fomalhaut
This is Bob Moler with Ephemeris for Thursday, October 19th. Today the Sun will be up for 10 hours and 48 minutes, setting at 6:51, and it will rise tomorrow at 8:04. The Moon, 2 days before first quarter, will set at 9:39 this evening.
There’s a bright star that appears for only seven and a half hours on autumn evenings. Its appearance, low in the south-southeast at 9 p.m., is a clear indication of the autumn season. It is currently below the much brighter Saturn. The star’s name is Fomalhaut, which means fish’s mouth. That’s fitting because it’s in the constellation of Piscis Austrinus, the southern fish. At our latitude it’s kind of the fish that got away, because usually Fomalhaut appears to be quite alone low in the sky. For the last few years Jupiter and then Saturn have kept it company. In a couple of years Saturn will have moved on leaving Fomalhaut to its lonely vigil in the south.
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: 07/18/2023 – Vega, the brightest star of the Summer Triangle
This is Ephemeris for Tuesday, July 18th. Today the Sun will be up for 15 hours and 9 minutes, setting at 9:23, and it will rise tomorrow at 6:15. The Moon, 1 day past new, will set at 10:30 this evening.
Vega, in the constellation Lyra the harp, is the highest bright star In the east and brightest star of the Summer Triangle also rising in that direction. It is an important and much studied star, first as a standard for brightness for the magnitude scale at almost exactly zero. In 1983 the Infrared Astronomy Satellite, IRAS, discovered an excess of infrared radiation coming from the star. It seems now that there are two orbiting rings around the star, an inner warm ring and an outer cold ring. This is somewhat like the two disks of material the Sun has: The asteroid belt between Mars and Jupiter and the Kuiper belt, beyond Neptune. No planets have yet been discovered around Vega, but I wouldn’t bet against it.
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
07/17/2023 – Ephemeris – Arcturus, a look at the Sun’s future
This is Ephemeris for Monday, July 17th. Today the Sun will be up for 15 hours and 11 minutes, setting at 9:24, and it will rise tomorrow at 6:14. The Moon is new today, and won’t be visible.
Arcturus, a red giant star, is about two thirds the way up the sky in the southwest at 10:30 or 11 p.m. It’s one of the earliest stars to appear in twilight, being nearly tied in brightness with Vega, a white star about as high in the east. 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
07/03/2023 – Ephemeris – The Sun is more massive than most stars
This is Bob Moler with Ephemeris for Monday, July 3rd. Today the Sun will be up for 15 hours and 29 minutes, setting at 9:31, and it will rise tomorrow at 6:02. The Moon, at full today, will rise at 10:28 this evening.
The Sun appears to be a singular object in the sky. There is none other. But is that true? No, it’s not. The Sun is a star, middle-aged for a star of its mass. The Sun is bigger than most stars, because most stars are runty red dwarf stars. In fact the closest star to our Sun is a red dwarf, called Proxima Centauri, the third, outlying star in the triple star system whose brightest star is called Rigil Kentaurus, though better known by its 1603 Bayer catalog designation, Alpha Centauri. Proxima is a challenge to spot even with binoculars. It turns out that stars visible to the naked eye are all brighter than the Sun. As far as the range of stellar masses go, the Sun is pretty much in the middle. Rigil Kentaurus itself is 8 percent more massive than the Sun and 50 percent brighter. Both Rigil Kentaurus and Proxima are too far south to see from Michigan.
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
Bob Moler's Ephemeris Blog 