Archive
Ephemeris: 08/29/2025 – Late August crescent Moon stays low in the western sky
This is Ephemeris for Friday, August 29th. Today the Sun will be up for 13 hours and 22 minutes, setting at 8:24, and it will rise tomorrow at 7:03. The Moon, 2 days before first quarter, will set at 10:48 this evening.
There’s an interesting feature that I’ve noticed about the Moon this time of year. When there’s a waxing crescent Moon in the evening, in late summer to early autumn, it’s seen pretty low in the southwestern sky after sunset. Tonight it’ll be two days before first quarter so it’ll be a fat crescent. However, when it’s seen after sunset, it will be very low in the southwestern sky. Contrast that for early risers, at this time of year the waning crescent Moon moves at a steep angle to the horizon, as do the planets now in the east. And of course the opposite is true for late winter and early spring moons. By the way, the Harvest Moon is in early October this year. The Harvest Moon is the nearest full moon to the autumnal equinox.
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: 08/28/2025 – The first stars
This is Ephemeris for Thursday, August 28th. Today the Sun will be up for 13 hours and 25 minutes, setting at 8:26, and it will rise tomorrow at 7:02. The Moon, 3 days before first quarter, will set at 10:23 this evening.
Astronomers think that the first stars that formed after the Big Bang were very different from the stars we see around us today. They are called Population 3* stars. In fact, none of them have survived to this time. Back then there were no heavy elements, just hydrogen and helium. This allowed much more massive stars to form than stars today. The reason is the lack of heavier elements that make the interior of the star to be more opaque. This allows the core’s radiant energy to counteract the gravity of the star’s mass better and limit the stars’ growth. Supermassive stars burn hotter and live much shorter lives, exploding to spew the core contents of heavier elements, enriching the nebulae from which later stars form.
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
The above illustration comes from an article by Daegene Koh: Population III stars: The Universe’s ultimate reclusive pop stars.
* Stars are grouped into 3 populations based on their order of being recognized. The stars around us are population 1 stars. They have a lot of, what astronomers call, metals in their atmospheres. To an astronomer, when talking about stars, metals are any elements heavier than helium. Older stars we find in globular star clusters or in the centers of galaxies are classed as Population 2. They have lower amounts of metals in their atmosphere. The term for the amount of metals in a star’s atmosphere is called metallicity. Population 3 stars are the stars that are born just after The Big Bang when the universe was filled with just hydrogen and helium with possible tiny amounts of lithium and beryllium. These stars can grow very massive, and live very short lives, which is why we don’t see them anywhere near us. To spot the Population 3 stars we need a time machine. Fortunately we have one, the telescope. In looking back in space we are looking back in time, since the speed of light is finite. And the greatest time machine of all is the James Webb Space Telescope. Astronomers are hoping they can look back far enough to see Population 3 stars. Not individually, I don’t think, they’re too far away for that. But whole galaxies of them, at the dawn of time.
Like I’ve been saying in a whole bunch of contexts… They don’t make them like that anymore!
Ephemeris: 08/27/2025 – Taking our weekly look at the whereabouts of the naked-eye planets
This is Ephemeris for Wednesday, August 27th. Today the Sun will be up for 13 hours and 28 minutes, setting at 8:27, and it will rise tomorrow at 7:00. The Moon, halfway from new to first quarter, will set at 10:02 this evening.
Let’s take our weekly look at the whereabouts of the naked-eye planets. The Red Planet Mars is too close to the direction of the Sun to spot. This is the curse of trying to view evening planets, which are near the direction of the Sun in late summer and early fall, for us at higher latitudes. Saturn now rises at 9:27 PM in the east. In a telescope Saturn sports a very thin ring, a bit more than 3° from being edge on. This angle will decrease to about a third of a degree by November 23rd before increasing. By 6 AM Saturn will be in the southwest. Jupiter will appear above the brighter Venus in the Eastern sky And among the brighter winter stars. Mercury will be in line with Venus and Jupiter very near the horizon.
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: 08/26/2025 – Update on our expected nova T Coronae Borealis
This is Ephemeris for Tuesday, August 26th. Today the Sun will be up for 13 hours and 31 minutes, setting at 8:29, and it will rise tomorrow at 6:59. The Moon, 3 days past new, will set at 9:44 this evening.
There is a star in the constellation of Corona Borealis, the Northern Crown, which astronomers are expecting to become a nova which means become rapidly very bright. The initial predictions favored last year, 2024, but it has yet to explode. The star’s designation is T Coronae Borealis, or T CrB for short. It’s a variable star designation. And an explosion occurs on one member of this binary star system about every 80 years. The last time was in 1946. Jean Schneider* of the Paris Observatory thinks they found a pattern within the 80-year time frame. The 227.6-day period of the white dwarf star orbiting its much larger primary. This seems to match the last three explosions. So the next likely date will be November 10th this year. We’ll see.
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.
* I found a link to this on the spaceweather.com website in a section called T CrB Nova Watch.
Addendum
Ephemeris: 08/25/2025 – Two fascinating constellations in and near the Summer Triangle
This is Bob Moler with Ephemeris for Monday, August 25th. Today the Sun will be up for 13 hours and 33 minutes, setting at 8:31, and it will rise tomorrow at 6:58. The Moon, 2 days past new, will set at 9:27 this evening.
There are two small constellations in and near the Summer Triangle of bright stars. Both are near Altair the bottom star of the triangle in the southeast. The first is Delphinus the dolphin to the left of Altair. Delphinus is made-up of a small squished box of stars with another star below. It does look a dolphin leaping out of the water. The legendary Greek poet Arion, according to myth, was rescued by a dolphin. Also, the little squished box is an asterism called Job’s Coffin, though no one knows the origin of that name. The second constellation is above Altair, and within the Summer Triangle. It is called Sagitta the arrow. The stars do line up to look like a short arrow. It’s supposed to represent Cupid’s dart.
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: 08/22/2025 – Star Party tomorrow night the 23rd
This is Ephemeris for Friday, August 22nd. Today the Sun will be up for 13 hours and 42 minutes, setting at 8:36, and it will rise tomorrow at 6:55. The Moon, 1 day before new, will rise at 7:10 tomorrow morning.
Weather permitting, the Grand Traverse Astronomical Society and the Park Rangers will host a star party at Sleeping Bear Dunes National Lakeshore, at the Dune Climb tomorrow night, starting around 9 PM. The parking lane closest to the dune will be blocked off for telescopes. The start time is after sunset, and the brighter stars will be visible by 9:15. As it gets darker some of the brighter interstellar wonders of our Milky Way galaxy, will appear, with many star clusters and nebulae, including a peek at the Great Andromeda Galaxy next door. The Rangers will leave around 11 PM however if it stays clear and there’s enough interest, society members with their telescopes will stay longer. This is the last Sleeping Bear Dunes star party this year.
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: 08/21/2025 – The Milky Way’s Great Rift
This is Ephemeris for Thursday, August 21st. Today the Sun will be up for 13 hours and 45 minutes, setting at 8:38, and it will rise tomorrow at 6:53. The Moon, 2 days before new, will rise at 5:57 tomorrow morning.
Once one finds the Milky Way which is pretty hard to miss this month, it becomes obvious that the Milky Way is split lengthwise starting near Deneb, the northernmost star of the Summer Triangle, almost all the way to the Teapot of Sagittarius low in the south. That dark split is called the Great Rift. Galileo first discovered that the hazy clouds of the Milky Way were actually made of faint stars, so it was thought the dark areas were due to a lack of stars. The great 18th century astronomer William Herschel did star counts all over the sky with his telescope. A map his sister drew of the flattened shape of his universe shows the lack of distant stars in one direction. It’s not really fewer stars, but interstellar clouds of dust blocking the light of the stars behind them.
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: 08/20/2025 – Taking our weekly look at the whereabouts of the naked-eye planets
This is Ephemeris for Wednesday, August 20th. Today the Sun will be up for 13 hours and 48 minutes, setting at 8:39, and it will rise tomorrow at 6:52. The Moon, 3 days before new, will rise at 4:41 tomorrow morning.
Let’s take our weekly look at the whereabouts of the naked-eye planets. The Red Planet Mars is too close to the direction of the Sun to spot. This is the curse of trying to view evening planets, which are near the direction of the Sun in late summer and early fall, for us at higher latitudes. Saturn now rises at 9:55 PM in the east. In a telescope Saturn sports a very thin ring, a bit less than 3° from being edge on. By 6 AM Saturn will be in the southwest. Jupiter will appear above the brighter Venus in the Eastern sky And among the brighter winter stars. Venus is by far the brighter of the two planets. Mercury will be below the crescent Moon tomorrow morning.
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: 08/19/2025 – Mercury makes its morning appearance
This is Ephemeris for Tuesday, August 19th. Today the Sun will be up for 13 hours and 51 minutes, setting at 8:41, and it will rise tomorrow at 6:51. The Moon, 3 days past last quarter, will rise at 3:25 tomorrow morning.
The tiny planet Mercury is making an appearance in the morning sky now. For the next week or so it will be visible around 6 AM. At least it’s time to start looking for it. Once found, it might be followed for another 20 minutes or so. This morning Mercury was at its greatest angular separation or elongation from the Sun of 18.6°. We have two periods where Mercury is easier to spot: on late winter and early spring evenings, and in the morning sky in late summer and early autumn. Of course Mercury must be at the proper elongation point at the time. Mercury is the smallest of the planets, being only 50% larger in diameter than our moon. In closeup, it looks much like our Moon, gray and cratered.
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: 08/18/2025 – Wandering through Sagittarius with binoculars
This is Ephemeris for Monday, August 18th. Today the Sun will be up for 13 hours and 54 minutes, setting at 8:43, and it will rise tomorrow at 6:50. The Moon, 2 days past last quarter, will rise at 2:12 tomorrow morning.
Let’s look around the Teapot shape of stars that is the constellation of Sagittarius. A pair of binoculars or a telescope with a very low magnifying power is all that’s needed. The purpose here is not so much to make things bigger, but make them brighter. Right off the tip of the teapot’s spout is a large and bright patch of light. This is the farthest we can see, in visible light that is, toward the center of our galaxy, part of the central bulge. Astronomer Walter Baade discovered that fact in the mid 1940s. The center of the galaxy is 4 moon-widths or 2 degrees to the right of it, but obscured by a cloud of interstellar dust. It is called the Large Sagittarius Star Cloud or Baade’s Window, peering out 25 thousand light years away.
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
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