Archive
Ephemeris: 06/29/2026 – Red stars large and small
This is Ephemeris for Monday, June 29th. Today the Sun will be up for 15 hours and 32 minutes, setting at 9:32, and it will rise tomorrow at 6:00. The Moon, at full today, will rise at 9:53 this evening.
There are two kinds of red stars very bright ones and very dim ones. The bright red ones are very few. One of them in the evening sky now is Antares in the heart of Scorpius the scorpion. Another one is in the winter sky and the most famous red giant of all, Betelgeuse in the shoulder of Orion the hunter. These are giant stars have exhausted the hydrogen in their cores to produce helium and are working on helium or even heavier elements fusing them to still heavier elements at even higher temperatures to keep them alive, but since they are working on the ash of the previous reaction, they won’t last very long, and the star dies, possibly cataclysmically. The higher internal heat bloats the star to be, huge, making its outer layers are actually cooler.
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: 06/26/2026 – How do we know so much about those points of lights in the sky?
This is Ephemeris for Friday, June 26th. Today the Sun will be up for 15 hours and 33 minutes, setting at 9:32, and it will rise tomorrow at 5:59. The Moon, 3 days before full, will set at 3:37 tomorrow morning.
All but a handful of stars are mere points in even our largest telescopes. How do we know so much about them then? The reason is the science of spectroscopy, breaking down light into its constituent colors where color equals frequency or the energy of the light. Isaac Newton was the first to discover that by passing white light through a prism it turned into a rainbow of colors that the colors were actually combined within the white light. Passing sunlight through a vertical slit and smearing the light horizontally with the prism into its constituent colors, many dark vertical lines within that spectrum of colors appear. They turned out to be the fingerprints of the elements within the atmospheres of the stars, and that is just the beginning.
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: 06/25/2026 – The color of stars
This is Ephemeris for Thursday, June 25th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:58. The Moon, halfway from first quarter to full, will set at 3:03 tomorrow morning.
Looking out at the night sky casually, the first impression is that the stars all appear to be white. Closer inspection shows that some appear with tinges of red or orange or maybe yellow while other stars have a bluish cast to them. The color of stars is due to their surface temperature which physicists call black body radiation. A rainbow is a spectrum of colors from red through orange yellow green blue and violet. These colors represent the different wavelengths of light. The peak wavelength determines the star’s surface temperature. The Sun’s in the green in the middle of our visual field. Cooler stars have their peak in the red, while hotter stars have their peak output to the blue end of the spectrum.
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: 06/24/2026 – Where are the naked-eye planets this week?
This is Ephemeris for Wednesday, June 24th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:58. The Moon, 3 days past first quarter, will set at 2:36 tomorrow morning.
Let’s take our weekly look at the whereabouts of the naked-eye planets. By 10:30 PM tonight, nearly an hour after sunset, Venus and Jupiter are seen in the western sky, with Jupiter below and right of the brighter Venus. Mercury, though being just above the horizon at that time, is completely overcome by the twilight. A telescope will show a very tiny gibbous disc of Venus, because it is still pretty much beyond the Sun, 102 million miles (164 million kilometers) away from us. Over the next 4 months it will be moving closer to us and becoming much larger. In the morning, Saturn will rise at 1:52 AM, followed by dimmer Mars nearly 2 hours later. The Earth is now chasing down Mars, and soon the launch window will open to send spacecraft to the Red Planet.
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: 06/23/2026 – How the Sun sizes up to other stars
This is Ephemeris for Tuesday, June 23rd. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:58. The Moon, 2 days past first quarter, will set at 2:13 tomorrow morning.
Stars big and small, where does the Sun rank? It depends on the criteria. As far as mass goes, it’s pretty much in the middle. One can’t get stars much more than 20 times the mass of the Sun stars or stars less than a 10th the mass of the sun. As far as brightness goes, there are stars 100,000 times brighter than the sun and stars hundreds of times dimmer. All the stars that you can see with the naked eye, with very few exceptions, are all brighter than the sun intrinsically. As far as size goes from the largest and smallest, the sun ranks near the bottom, in a range from 1,000% down to 15% the sun’s diameter. Don’t feel bad about the sun’s ranking. Stars like the sun in mass, which determines those other qualities, live long enough for life like us to evolve.
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: 06/22/2026 – Will SpaceX and Blue Origin be ready for Artemis 3?
This is Ephemeris for Monday, June 22nd. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32, and it will rise tomorrow at 5:57. The Moon, 1 day past first quarter, will set at 1:53 tomorrow morning.
NASA and it’s partners SpaceX and Blue Origin are having problems on their way back to the Moon. On April 28th, Blue Origin’s New Glenn Rocket blew up doing a static firing of its engines, destroying the rocket and severely damaging the launch pad, the only one they had. History has shown that launch pads take a year or more to rebuild. The New Glen Rocket is to launch their moon lander. SpaceX had a partially successful flight of their Starship, but had loss of engines, and didn’t perform an in space relight of a starship engine, to prove they could deorbit it. These two companies are suppliers of the lunar landers, prototypes of which must be ready next year for the Artemis 3 mission and a real lander must be ready in 2028 to stay on schedule.
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: 06/19/2026 – Summer begins Sunday as the Sun reaches the summer solstice
This is Ephemeris for Juneteenth, Friday, June 19th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:31, and it will rise tomorrow at 5:57. The Moon, 2 days before first quarter, will set at 12:58 tomorrow morning.
Summer will arrive at 4:25 AM Sunday morning (8:25 UT). Then the Sun will be out 15 hours 34 minutes for us in the Interlochen/Traverse City area. That’s within the same minute as today. Also, the Sun will reach up to nearly 69 degrees altitude above the southern horizon at local noon, that’s 1:44 pm. After the summer solstice we will begin to climb down from those extreme values, at first slowly, but with increasing rapidity as summer goes on. However, the Northern Hemisphere is continuing to warm up. Our warmest average temperatures tend to be near the end of July. What’s really neat is, the Earth is farther from the Sun than it was six months ago as winter started. It doesn’t make us any cooler, but makes summer longer.
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: 06/18/2026 – Looking to summer with the Summer Triangle
This is Ephemeris for Thursday, June 18th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:31, and it will rise tomorrow at 5:56. The Moon, 3 days before first quarter, will set at 12:36 tomorrow morning.
Summer skies are coming. It’s only 3 days until summer officially arrives. Looking to the eastern sky at 11 PM are three of the brightest stars in a large triangle. The top star Vega is about halfway up the sky to the zenith, and the brightest of the three. It’s in the small constellation of Lyra the harp. Lowest of the stars and just about due east is Altair in Aquila the eagle. Completing the triangle is Deneb in the northeast in the tail of Cygnus the swan or the head of the horizontal Northern Cross. These three stars make up the Summer Triangle, which isn’t an official constellation. It’s one of the many informal star patterns called asterisms. The Summer Triangle will be in our evening sky moving slowly westward until December.
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: 06/17/2026 – Checking out all the naked-eye planets for this week.
This is Ephemeris for Wednesday, June 17th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:31, and it will rise tomorrow at 5:56. The Moon, 3 days past new, will set at 12:09 tomorrow morning.
Let’s take our weekly look at the whereabouts of the naked-eye planets. By 10:15 PM tonight, nearly an hour after sunset, Venus and Jupiter, and even Mercury may be seen in the western sky, with Jupiter below and right of the brighter Venus, and Mercury below and right of Jupiter. Jupiter appears to be chasing Mercury back toward the sun. But Mercury is getting dimmer, and will soon be lost in the twilight glow. A telescope will show a very tiny disc on Venus, because it is still pretty much beyond the Sun, 106 million miles (171 mil km) away from us. Over the next 4 months it will be moving closer to us and becoming much larger. In the morning, Saturn will rise at 2:37 AM, followed by dimmer Mars an hour and a half later.
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: 06/16/2026 – More pointers to help you find Mercury tonight
This is Bob Moler with Ephemeris for Tuesday, June 16th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:30, and it will rise tomorrow at 5:56. The Moon, 2 days past new, will set at 11:34 this evening.
The planet Mercury, which had its greatest elongation or separation east of the sun yesterday, is still visible in line with Venus and Jupiter down to the lower right. It is also below the thin crescent moon tonight. There are a couple of other stars which you might mistake for Mercury. They’re higher in the sky, above the Moon and to the upper right of Jupiter. These are some of our leftover winter stars, Castor and Pollux of Gemini. Pollux is the slightly brighter one and closer to Jupiter of the two. Mercury is below them. A pair of binoculars is really helpful in picking Mercury out from the twilight.It seems to increase the contrast between star-like objects from the background. Actually, binoculars make a great first telescope.
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
