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12/16/2021 – Ephemeris – The brightest spot on the Moon
This is Ephemeris for Thursday, December 16th. Today the Sun will be up for 8 hours and 49 minutes, setting at 5:03, and it will rise tomorrow at 8:14. The Moon, 2 days before full, will set at 6:53 tomorrow morning.
The Moon tonight is bright. The sunrise line or terminator on the moon is crossing the large gray plain called Oceanus Procellarum, the largest of the moon’s seas. These seas were figments of the first telescopic observers imagination. They are really huge impact basins into which interior lava flowed. On the upper left edge of the moon near the terminator is a bright spot visible in binoculars. In a telescope, it is a crater called Aristarchus. It is a fairly new crater, probably less than a billion years old. As a rule the brighter the crater the newer it is. Aristarchus is the brightest spot on the moon. Over the years, visual astronomers have seen hazes and bright spots from time to time in and near Aristarchus. Their cause is still a mystery.
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
The brightest spots on the Moon as they might appear tonight, December 16, 2021. This is not a photograph. But created using Stellarium, presumably from lunar satellite photographs that simulate the phase and shadows.
Oblique view of the crater Aristarchus from a lunar orbiting satellite. Credit: NASA/GSFC/Arizona State University.
12/14/2021 – Ephemeris – The Moon tonight will reveal more than you think
This is Ephemeris for Tuesday, December 14th. Today the Sun will be up for 8 hours and 49 minutes, setting at 5:02, and it will rise tomorrow at 8:13. The Moon, halfway from first quarter to full, will set at 4:45 tomorrow morning.
The gibbous Moon tonight is revealing a bit more of itself. In binoculars the dark oval spot visible on the Moon’s right side is the Sea of Crises or Mare Crisium a small dark lava plain. The Moon’s rotation is quite uniform, however its orbit isn’t circular, so the Moon’s face seems to rock a bit back and forth over the month. It’s an effect called libration. And one way to track that is to note how close the Sea of Crises is to the edge of the Moon. Right now that sea is as far from the Moon’s right edge or limb as it gets, and reveals two other seas in the edge: Mare Marginis, the Border Sea, and Mare Smythi, Smith’s Sea.
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
The Moon showing Maria Marginis and Smythi past Mare Crisium at 9 pm tonight, December 14, 2021. Created using Stellarium.
The Moon, seen as if flying over the border area of what we could see from the Earth. To the left is the Moon’s near side. To the right is the far side to the terminator or sunset line. Created using Virtual Moon Atlas.
Both the Stellarium and Virtual Moon Atlas apps are free. Links to them are elsewhere on this page.
11/18/2021 – Ephemeris – An almost total eclipse of the Moon will be visible early tomorrow morning
This is Ephemeris for Thursday, November 18th. Today the Sun will be up for 9 hours and 27 minutes, setting at 5:11, and it will rise tomorrow at 7:45. The Moon, 1 day before full, will set at 7:58 tomorrow morning.
Should our normal November clouds depart in the early morning hours tomorrow, we will be treated with a very deep partial eclipse of the Moon. At 4:03 am, the Moon will be 97% immersed into the Earth’s inner shadow, with lower left edge peeking out into sunlight. I haven’t heard of any massive volcanic eruptions in our Southern Hemisphere, so the light leaking and bent though the Earth’s atmosphere from all the simultaneous sunrises and sunsets during the eclipse won’t be too diminished and give us a coppery hue in the shadow. The shadow will touch the Moon at its top edge at 2:19 am. The maximum will occur at 4:03 am, and the last bit of the shadow will depart at the lower right edge of the Moon at 5:47 am.
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
November 19, 2021, partial lunar eclipse maximum at 4:05 am EST. Orientation of the Moon and shadow could be different if not viewing from Northern Michigan. Created using Stellarium.
Lunar Eclipse Diagram for November 19, 2021. Effects of the eclipse on the Moon at P1 and P4 are not visible. U1 is the Moon at the beginning of the partial eclipse. U4 is the Moon at the end of the partial eclipse. A duskiness on the Moon’s face on the side closest to the umbral shadow will be visible just before and after the partial eclipse. Note that this diagram is not at the same orientation that an observer might experience. Created from a NASA PDF document on the NASA Eclipse Website. https://eclipse.gsfc.nasa.gov/eclipse.html.
11/16/2021 – Ephemeris – How China retrieved a sample from the Moon, and what Chang’e 5 is up to next
This is Ephemeris for Tuesday, November 16th. Today the Sun will be up for 9 hours and 31 minutes, setting at 5:13, and it will rise tomorrow at 7:42. The Moon, 3 days before full, will set at 5:49 tomorrow morning.
China’s Chang’e sample return mission of late last year was quite a feat. The spacecraft had an orbiter that orbited the Moon, and sent a lander with an ascent rocket. After the lander secured its samples, it put them in the ascent rocket, which launched back up to the orbiter. The samples were placed in a reentry capsule attached to the orbiter, which left the Moon’s orbit and headed back to the Earth. Near Earth, it ejected the reentry capsule and swung past Earth and headed out to the Earth-Sun Lagrangian point 1 between the Earth and Sun. There are already several satellites in halo orbits around L1, because it’s a great spot to be to study the Sun unobstructed by the Earth, and detect Coronal Mass Ejections (CMEs) about an hour before they reach Earth. NASA, NOAA and the European Space Agency all have satellites out there.
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
Chang’e 5 Descent Capsule lands. It looks like a miniature Russian Soyuz Descent capsule. Credit Chinese Space Agency via Global Times.
Earth-Sun Lagrangian Points. These are where a small body can stay. L1, 2 and 3 are unstable, so some little effort is needed to keep a spacecraft near there. L4 and L5 are stable. Source: Wikimedia Commons, Xander89. Click to enlarge.
1/15/2021 – Ephemeris – What the Chinese Chang’e 5 lunar mission found
This is Bob Moler with Ephemeris for Monday, November 15th. Today the Sun will be up for 9 hours and 34 minutes, setting at 5:14, and it will rise tomorrow at 7:41. The Moon, halfway from first quarter to full, will set at 4:45 tomorrow morning. | Late last year, the Chinese sent an uncrewed spacecraft to the Moon to collect samples of the surface material. That material is called regolith, and they drilled down at least a meter, which they returned to the Earth. An international team of geologists has been studying the material, and we have the first reports. Apparently the material they picked up was dated at 2 billion years, which is an intermediate age to the material picked up by the Apollo missions that dates either 3 billion years or older or 1 billion years. That helps fill gaps in the Moon’s history. Of course, all the material in the solar system is 4.5 billion years old. But the radioactive dating clock is reset when a rock is melted and solidifies.
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
Chang’e 5 Landing-Site on full moon map. Created using Virtual Mon Atlas.
11/12/2021 – Ephemeris – The Moon appears to wobble slowly over the month
This is Ephemeris for Friday, November 12th. Today the Sun will be up for 9 hours and 41 minutes, setting at 5:17, and it will rise tomorrow at 7:37. The Moon, 1 day past first quarter, will set at 1:27 tomorrow morning.
When I look at the Moon, I check the position of one particular feature. A small, nearly circular gray area near the right or western edge of the Moon’s disk. It’s called the Sea of Crises, or in Latin, Mare Crisium. The reason I check it is that over the month its distance from the edge, or what astronomers call the limb, changes. That sea is about as far as it can get from the limb now. The reason for this wobbling back and forth, called libration, is that the Moon rotates at a constant rate due to angular momentum, but its revolution around the earth is an ellipse, so it doesn’t move with a uniform speed in its orbit. It moves faster at its closest to the Earth, called perigee, and is slowest at apogee, its farthest from the Earth.
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.
The Moon tonight (November 12, 2021) showing Mare Crisium (Sea of Crises) about as far from the limb (Moon’s edge) as it can get. Created using Stellarium.
Simulation of the Moon’s phase and libration for October 2007 by Tomruen. Image is in the Public Domain.
09/20/2021 – Ephemeris – The Harvest Moon rises tonight
This is Ephemeris for Monday, September 20th. Today the Sun will be up for 12 hours and 15 minutes, setting at 7:43, and it will rise tomorrow at 7:29. The Moon, at full today, will rise at 8:03 this evening.
Tonight’s full moon is the Harvest Moon. It is the most famous of the named full moons, and was very useful in the days before electric lights. The reason is that the Moon, around the time it is full now, doesn’t advance its rising time very much from night to night, effectively extending the light of twilight to allow more time to gather in crops. This is because the Moon is moving north as well as eastward. The farther north it is, the longer it stays up and retards the advance in rise times. On average, the Moon rises 50 minutes later each night. This week, the interval is down near 20 minutes advance in moonrise times per day, extending twilight and the time each day to harvest the crops for a few more days.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT-4 hr). They may be different for your location.
Addendum
The autumn vs spring sunset ecliptic. I’m using the autumnal equinox 2021, with the tip of the spout of the Sagittarius Teapot at due south, and vernal equinox 2022, with the red star Betelgeuse in Orion at due south as examples. Click on the image to enlarge it. Created using Stellarium and GIMP.
The ecliptic for the autumnal equinox runs low in the south, a preview of the Sun’s apparent travel for the next six months of fall and winter. Besides the planets, the Moon at sticks close to that line, as do the planets. The full moon rising in the east as the Sun sets does so at a shallow angle, so for a week or so around the full moon, its advance in rise times can be as little as 20 minutes per night. In spring, it can be much longer than an hour.
09/17/2021 – Ephemeris – The Moon has an atmosphere of sorts; Plus, I capture Inspiration 4 passing overhead
This is Ephemeris for Friday, September 17th. Today the Sun will be up for 12 hours and 24 minutes, setting at 7:49, and it will rise tomorrow at 7:25. The Moon, 3 days before full, will set at 4:24 tomorrow morning.
Jupiter, tonight, will be above the Moon. Everyone knows that the Moon is airless, that is has no atmosphere. That is not strictly true. Apollo astronauts saw glows and crepuscular rays in the direction of the Sun before its rising an after it set as they orbited the Moon. In 2013 NASA sent an orbiter spacecraft named LADEE to the Moon to investigate. LADEE stands for Lunar Atmosphere and Dust Environment Explorer. It orbited low over the Moon’s equator. The atmosphere of the Moon consists of some gasses like sodium, neon, argon and helium plus dust electrostatically charged by the Sun’s x-ray and ultraviolet emissions and sent aloft, up to many kilometers. The dust will fall back down, but the gasses will be dissipated by the solar wind. It’s very tenuous.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.
Addenda
Jupiter, Saturn and the Moon tonight at 9 pm tonight, September 17, 2021. Jupiter will be moving to be directly below Jupiter by one in the morning. Created using Stellarium.
Apollo 17 twilight ray sketches. Credit: NASA/Apollo 17 Astronauts.
Artist’s depiction of LADEE in orbit of the Moon. Courtesy NASA.
Inspiration 4 spacecraft caught flying over Northern Michigan
The thin vertical streak on the left side of the image is the Inspiration 4 spacecraft against the stars of Hercules in a 15 second exposure with a Canon Rebel T5 camera, f/3.5, ISO 6400, 18 mm fl. The famous Keystone of Hercules asterism is to the upper right of center. It’s a bit out of focus due to my problem seeing the screen at a high angle. (Getting old). It was quite dim, so I actually couldn’t see it in the moonlight. Credit: mine.
I was guided to the time and place in the sky by heavens-above.com.
09/14/2021 – Ephemeris – Lack of spacesuits just one of Artemis problems of getting humans back to the Moon
This is Ephemeris for Tuesday, September 14th. Today the Sun will be up for 12 hours and 33 minutes, setting at 7:54, and it will rise tomorrow at 7:21. The Moon, 1 day past first quarter, will set at 12:53 tomorrow morning.
The bright gibbous Moon is a feast for binoculars or a telescope. However, the speed-up plan to land crews on the Moon in 2024 proposed by the former President is not appearing to pan out. One major item is space suits, which must be more rugged and impervious to the Lunar regolith, or soil, whose grains are tiny, angular and sharp, and get into everything, and can destroy spacesuit joints. NASA has been working on them for 14 years, and by itself could cost a billion dollars. They might be ready by 2025. Besides delays to the SLS rocket, the contract with SpaceX to furnish a lunar lander is now tied up in litigation by one of the contract losers. NASA’s trying to land humans on the Moon on one half of one percent of the Federal budget, plus do everything else it does.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.
Addendum
Prototype lunar spacesuit. xEMU stands for Exploration Extravehicular Activity Mobility Unit. Of course. This uncredited image is from slashgear.com in 2019, so I wouldn’t believe the date. These xEMU suits may eventually cost a billion dollars to develop and produce. Click on the image to enlarge it.
09/13/2021 – Ephemeris – The Greeks knew the size and shape of the Earth and estimated the distance to the Moon a long time ago
This is Bob Moler with Ephemeris for Monday, September 13th. Today the Sun will be up for 12 hours and 37 minutes, setting at 7:56, and it will rise tomorrow at 7:20. The Moon, at first quarter today, will set at 11:57 this evening.
The Ancient Greeks used lunar eclipses to determine that Earth is a sphere, and worked on determining the distance to the Moon. From ancient times, the Greeks knew that an eclipse of the Moon was caused by the Earth’s shadow falling on the Moon. Since the Earth’s shadow was always circular, no matter where the Moon was in the sky during an eclipse, the Earth must be a sphere since that’s the only three-dimensional body that always casts a circular shadow. They also used the size of the Earth’s shadow to estimate the distance to the Moon. The lunar distance, on average, is 60.8 times the Earth’s radius away. The first estimates were about one third of that. Hipparchus in the 2nd century BC got much closer. It got even better from there.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan (EDT, UT – 4 hr). They may be different for your location.
Addendum
Partial Lunar Eclipse showing circular arc of the Earth’s shadow. Taken 04:15 UT August 17, 1970. Credit: the author.
The size of the Earth was unknown until Eratosthenes did in 240 BC. He came up with the circumference of the Earth to a fairly high degree. The Circumference is equal to the radius of a sphere or circle by 2πr.
Bob Moler's Ephemeris Blog 