Archive
Ephemeris: 08/03/2026 – The Milky Way, a spiral galaxy with a bar
This is Ephemeris for Monday, August 3rd. Today the Sun will be up for 14 hours and 34 minutes, setting at 9:05, and it will rise tomorrow at 6:32. The Moon, 2 days before last quarter, will rise at 11:07 this evening.
The Milky Way is classed as a barred spiral galaxy. It has an apparent spiral structure in its disk illuminated by bright massive short lived stars that don’t stray far from the nebulae they were born from. Nebulae, mostly dark, form the backbone of the spiral structure. The Andromeda Galaxy is also a spiral, a little larger than our Milky Way Galaxy. Dwarf galaxies like the Magellanic clouds which are seen from the southern hemisphere of the earth that happen to be satellites of the Milky Way, and are irregular in shape. A third type of galaxy is the elliptical galaxy, many of which are extremely large and contain pretty much nothing but old stars, and no nebulosity to make new ones.
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; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 07/30/2026 – The types and distribution of galaxies
This is Ephemeris for Thursday, July 30th. Today the Sun will be up for 14 hours and 44 minutes, setting at 9:10, and it will rise tomorrow at 6:27. The Moon, 1 day past full, will rise at 9:52 this evening.
Until a little over 100 years ago the Milky Way was thought to be the whole universe. Then with photography the great Andromeda nebula turned out to be not a cloud of gas but a great group of stars outside. Since then we have found billions upon billions of these galaxies. Galaxy simply is a derivation from “Milky Way” in Latin. Galaxies are not sprinkled through the universe uniformly. They appear in great clusters and in small groups. The Milky Way and the Andromeda Galaxy belong to a relatively small group of galaxies called the Local Group, which contains 130 or more, mostly dwarf galaxies of which Andromeda and our Milky Way are the largest. The Great Andromeda Galaxy will come in view into the evening sky this autumn.
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; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 05/04/2026 – Looking out of the Milky Way
This is Bob Moler with Ephemeris for Monday, May 4th. Today the Sun will be up for 14 hours and 23 minutes, setting at 8:51, and it will rise tomorrow at 6:26. The Moon, 3 days past full, will rise at 12:25 tomorrow morning.
The May evening sky, when it finally gets dark, contains fewer stars than those of winter. And they’re much dimmer. The main reason for that is that we are looking out the plane of the Milky Way Galaxy. The Milky Way is no nowhere to be seen, because it rings the horizon. A bit is visible in the north. The summer triangle of bright stars is not completely up in the evening, and it straddles the Milky Way. So we are looking out to the universe beyond the Milky Way, for the most part. Even amateur telescopes will reveal a great number of galaxies, because there’s a huge cluster of galaxies in the constellation Virgo which is right behind and below Leo the lion in the sky. However, just about 90° from the plane of the Milky Way is a star cluster that looks like strands of hair.
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; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 03/23/2026 – Looking out beyond the spring stars
This is Ephemeris for Monday, March 23rd. Today the Sun will be up for 12 hours and 19 minutes, setting at 7:59, and it will rise tomorrow at 7:38. The Moon, 2 days before first quarter, will set at 2:23 tomorrow morning.
It is becoming more obvious as the Moon waxes, that there’s more bright stars in the south and southwestern part of the sky than there are in the southeastern sky. That’s because the Milky Way runs through the winter part of the sky. It’s not as bright as the Milky Way appears in the summer since we are looking away from the center of our Galaxy. The disk of our galaxy causes stars to congregate near that Milky band, whether we can see it well or not. That is the main reason the winter stars are so bright. In the southeast we are looking at the spring sky. Leo the lion and of course the Great Bear with the Big Dipper are there, but we are mostly looking outside the disk or galaxy to the universe beyond. So we’re looking through fewer nearby stars, so the spring sky seems somewhat lackluster compared to the crazy chaos of the winter sky.
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: 10/28/2025 – The structure of the universe
This is Ephemeris for Tuesday, October 28th. Today the Sun will be up for 10 hours and 20 minutes, setting at 6:36, and it will rise tomorrow at 8:17. The Moon, 1 day before first quarter, will set at 11:38 this evening.
Dark matter makes up about 85% of all the matter in the universe, even though we can’t see it. It creates a kind of lattice on which the galaxies form. In looking out into the universe we see that there is a structure to it, not just random clusters of galaxies. The structure of the universe seems to be like a foam of bubbles where galaxies form along the intersection of these bubbles. The bubbles themselves are called voids. And with the expansion of the universe these voids are growing because space itself is expanding. So it’s not so much that the galaxies are fleeing each other, but that the voids are growing, pushing the galaxies apart. The galaxies are just going along for the ride.
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; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 10/10/2025 – Could radio noisy galaxies harbor many advanced civilizations?
This is Ephemeris for Friday, October 10th. Today the Sun will be up for 11 hours and 14 minutes, setting at 7:06, and it will rise tomorrow at 7:53. The Moon, 3 days before last quarter, will rise at 9:00 this evening.
I ran across an article on the Universe Today website a few days ago about galaxies with high radio emissions, that could be home to many advanced civilizations. Some galaxies do emit a lot of radio emissions, mainly because they have a black hole in the center that it was, in the past, active throwing out material from the galaxy that didn’t make it into the black hole. But this would be emissions from the actual disk of the Galaxy, inside which would be the cacophony of many advanced civilizations and their normal transmissions of their version of I Love Lucy. When combined, it enhances the general radio noise, so it can be detected as being out of ordinary. And there are a few galaxies like that. It would make the universe less lonely.
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; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Here’s a link to the Universe Today article: https://www.universetoday.com/articles/galaxies-with-high-radio-emissions-could-be-home-to-many-advanced-civilizations
Ephemeris: 07/21/2025 – When our knowledge of the size of the universe expanded
This is Ephemeris for Monday, July 21st. Today the Sun will be up for 15 hours and 2 minutes, setting at 9:20, and it will rise tomorrow at 6:18. The Moon, 3 days before new, will rise at 3:18 tomorrow morning.
A little over 100 years ago astronomers the Milky Way and the surrounding stars were thought to be the entire universe. A universe which was, apparently, disc shaped. Astronomers photographed examples of objects they called spiral nebulae, which they thought belonged to the Milky Way. Then Edwin Hubble photographed stars in the Andromeda spiral nebula. One star changed brightness in a way like some of the stars we know in our Milky Way. These stars are called Cepheid Variables and the rate of variation in brightness is related to their true brightness. This star that Hubble found was much too dim and much too far away to be in the confines of the Milky Way. Soon we found that we are in a spiral nebula or galaxy, like billions of others.
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; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Left: Carnegie Observatories. Right: NASA, ESA, and the Hubble Heritage Team (STScI/AURA); Acknowledgment: R. Gendler
The universe “expanded” again, when astronomers found out there were two types of Cepheids, one 4 times brighter than the other. Using the brighter Type I Cepheids, the measurement doubled the estimated distance*. This was about the time in the early 1950s when I was getting interested in astronomy, so the quoted distance to Andromeda and all the other galaxies doubled from older astronomy books to the newer ones.
* Inverse square law: brightness drops with the square of the distance. Double the distance and the brightness drops by 22 or 4.
Ephemeris: 05/13/2025 – Arcturus, extragalactic visitor?
This is Ephemeris for Tuesday, May 13th. Today the Sun will be up for 14 hours and 45 minutes, setting at 9:02, and it will rise tomorrow at 6:15. The Moon, 1 day past full, will rise at 10:39 this evening.
The bright orange star high in the southeast at 10 PM is Arcturus. Remember: Follow the arc of the handle of the Big Dipper to find Arcturus. It is an interesting star in many respects. Arcturus is somewhat more massive than the Sun and a bit older. It is starting its red giant phase having run out of hydrogen in its core and starting to use helium as its heat source, transmuting it into carbon and other elements. It has a very high velocity with respect to the Sun of about 100 kilometers per second. Arcturus is thought to be, by some astronomers, part of the remnants of a dwarf galaxy that collided with the Milky Way, and has now been assimilated. So Arcturus isn’t from around here.
-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; EDT, UT – 4 hours) unless stated otherwise. Times will be different for other locations.
Addendum
Ephemeris: 09/30/2024 – Andromeda’s treasure, its great galaxy
This is Bob Moler with Ephemeris for Monday, September 30th. Today the Sun will be up for 11 hours and 43 minutes, setting at 7:24, and it will rise tomorrow at 7:41. The Moon, 2 days before new, will rise at 6:27 tomorrow morning. | For at least the last thousand or so years a fuzzy spot in the constellation of Andromeda has been known. It was known as the Great Andromeda Nebula until about 100 years ago. Nebula means cloud, and it belonged to the Milky Way. At that time it was finally recognized as another Milky Way just like ours. So the word to call it was galaxy, a word that means Milky Way. It looks to be among the stars of Andromeda, but it’s far beyond the stars that we make of the constellation Andromeda. Current estimates place it at about two and a half million light years away, well beyond the stars that we see in Andromeda that range to only a few thousand light years distance. It will collide with our galaxy in about 4 billion years.
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: 05/30/2024 – Virgo and what’s hidden within
This is Bob Moler with Ephemeris for Thursday, May 30th. Today the Sun will be up for 15 hours and 18 minutes, setting at 9:20, and it will rise tomorrow at 6:00. The Moon, at last quarter today, will rise at 2:52 tomorrow morning.
One of the large constellations we see in the south at 11 p.m. can be found using the Big Dipper overhead, follow the arc of the handle to the bright star Arcturus, then straighten the arc to a spike to reach Spica, a bright blue-white star in the south. Spica is the brightest star in the constellation Virgo, the virgin. She represents the goddess of the harvest, Virgo is holding a sheaf of wheat in depictions of her, and Spica is placed at the head of the sheaf. In the space between Spica and Leo the lion to her upper right is, a great cluster of thousands of galaxies just below naked eye visibility. The Virgo Cluster. Inside that cluster is galaxy M87, in whose center lies a black hole with the mass of 6.5 billion suns. The center of the cluster is at about 54 million light years away. The first black hole imaged by the Earth spanning Event Horizon Telescope.
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 