Archive
08/04/2022 – Ephemeris – The Late Heavy Bombardment
This is Bob Moler with Ephemeris for Thursday, August 4th. Today the Sun will be up for 14 hours and 32 minutes, setting at 9:04, and it will rise tomorrow at 6:33. The Moon, 1 day before first quarter, will set at 12:19 tomorrow morning.
The face of the Moon is nearly half uncovered from our point of view, with first quarter occurring at 7:06 tomorrow morning. It shows the string of lunar seas, those gray areas on the moon which lead to the terminator, the Moon’s sunrise line. There are even more and larger seas on the east half of the Moon, as we see it. Most were created about 3.9 billion years ago by asteroid strikes. The same thing happened to the Earth, but plate tectonics destroyed the evidence. Not so on the Moon. The result, many planetary scientists think, was the Late Heavy Bombardment, caused by the changing orbits of mainly Saturn, Uranus and Neptune disrupting the smaller asteroids, and sending them careening through the solar system.
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
First quarter Moon with prominent seas labeled. Created using Stellarium, GIMP and LibreOffice.
Nice model infographic: Evolution of the solar system. Step 6, with the exchange of Neptune’s and Uranus’ orbits, cause the Late Heavy Bombardment. The Nice model isn’t that nice. It’s named for Nice, France, the city where the model was first developed. The original on the web page was smaller. I enlarged it and sharpened it a bit, so it’s more readable. Credit: Nora Eisner.
The above infographic is from the blog post at https://blog.planethunters.org/2019/04/29/formation-of-our-solar-system/ by Nora Eisner.
08/02/2022 – Ephemeris – Where did the Moon’s “seas” come from?
This is Ephemeris for Tuesday, August 2nd. Today the Sun will be up for 14 hours and 37 minutes, setting at 9:07, and it will rise tomorrow at 6:31. The Moon, 3 days before first quarter, will set at 11:37 this evening.
As the days progress to full moon on the 13th, the Moon will reveal its many maria or seas, as the first telescopic astronomers called these blemishes. Many have roughly circular outlines bounded by mountains. They have flat floors that are darker than the heavily cratered parts of the moon, and have very few craters on them. That means they were created after the major craters were made, and obliterated the craters beneath. The majority of the cratering came very early, as the Moon accreted from the material the was produced when a Mars sized protoplanet hit the early Earth about 4.51 billion years ago. That’s according to most planetary scientists. The maria are actually huge craters produced by large asteroids later, about 3.9 billion years ago.
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
Lunar “seas” seen on a first quarter moon. Mare is Latin for sea. Sinus means bay. Created using Stellarium, GIMP and LibreOffice.
Lunar “seas” and some other prominent features labeled on the last quarter moon.
02/10/2022 – Ephemeris – The waxing gibbous Moon is revealing more seas and craters
This is Ephemeris for Thursday, February 10th. Today the Sun will be up for 10 hours and 14 minutes, setting at 6:04, and it will rise tomorrow at 7:48. The Moon, 2 days past first quarter, will set at 4:38 tomorrow morning.
The Moon tonight is a waxing gibbous phase. More gray lunar seas are appearing near the terminator, the sunrise line. From north to south these seas, most only partially in sunlight, are: At the far north, the Cold Sea, Sea of Showers, The sea where the famous crater Copernicus is, the Sea of Islands. The southernmost sea at the terminator is the Sea of Clouds. Some large and prominent craters can be seen with binoculars or a small telescope can be seen in the south, the striking and relatively fresh Tycho, with its Moon girdling ejecta rays, though the rays are best seen at full moon. And the huge crater Clavius, with an arc of 5 smaller craters, one on its wall and the others on its floor, in ever diminishing sizes.
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
2 days past first quarter Moon as it would be seen in a small telescope or even binoculars, annotated. For this evening, February 10, 2022. Click on the image to enlarge it. Created using Virtual Moon Atlas. Annotations in white are from the app, mine are in green. Translations of the sea names are below.
Translations
Mare Crisium – Sea of Crises
Mare Fecunditatis – Sea of Fertility
Mare Frigoris – Sea of Cold
Mare Imbrium – Sea of Showers
Mare Insularum – Sea of Islands
Mare Nectaris – Sea of Nectar
Mare Nubium – Sea of Clouds
Mare Serenitatis – Sea of Serenity
Mare Tranquilitatis – Sea of Tranquility
A closer look
A montage of Clavius as photographed by one of the Lunar Orbiter spacecraft in the 1960s From Digital Lunar Orbital Photographic Atlas. Credit Jeff Gillis, Lunar and Planetary Institute.
02/07/2022 – Ephemeris – The Moon tonight
This is Ephemeris for Monday, February 7th. Today the Sun will be up for 10 hours and 5 minutes, setting at 6:00, and it will rise tomorrow at 7:53. The Moon, 1 day before first quarter, will set at 1:29 tomorrow morning.
Tonight, let’s take a look at the nearly first quarter Moon. The small, nearly circular gray spot is the sea of Crises. A diagonal chain of larger seas run from the terminator, the sunrise line, to below the Sea of Crises. They are, from the terminator, the seas of Serenity, Tranquility and Fertility. NASA is hoping to launch its uncrewed mission to the Moon, Artemis-1, next month with a large block of launch dates. The launch window begins on March 12th and ends on the 27th, with two blackout dates. Two lengths of missions are possible, a long 38 to 42 day mission is possible in the first part of the launch window, and a shorter 26 to 28 day mission is possible in the latter part of the window.
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 as it might appear tonight in binoculars or a small telescope at 7 pm tonight, February 7, 2022. I labeled the lunar seas with their English names, translated from the Latin. Also labeled is the Sea of Nectar, which wasn’t mentioned in the program. Moon image created using Stellarium.
05/17/2021 – Ephemeris – The Moon tonight
This is Ephemeris for Monday, May 17th. Today the Sun will be up for 14 hours and 54 minutes, setting at 9:06, and it will rise tomorrow at 6:11. The Moon, 2 days before first quarter, will set at 2:25 tomorrow morning.
The Moon tonight reveals a bit more territory than it did last night, and will every night until full moon. The Moon’s solar day equals a lunar month of about 29 and a half of our days. As seen in binoculars, below and left of The distinctly oval Sea of Crises, or Mare Crisium, is the Sea of Fertility, or Mare Fecunditatis. To the left of the Sea of Crises, the Sea of Tranquility (Tranquilitatis) where the Apollo 11 crew landed. Above that half of Sea of Serenity has come into daylight. Tonight the Beehive star cluster will be visible below and left of the Moon. It should be easily visible in binoculars and has a vaguely triangular shape. It was known to the ancients as Praesepe, the manger, who saw it as a glowing spot on moonless nights.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
05/28/2020 – Ephemeris – The Moon tonight and the origin of the lunar seas
This is Ephemeris for Thursday, May 28th. Today the Sun will be up for 15 hours and 15 minutes, setting at 9:18, and it will rise tomorrow at 6:01. The Moon, 1 day before first quarter, will set at 2:25 tomorrow morning.
Tonight’s Moon is a fat crescent. The lower or southern part of the Moon are brighter. These are the lunar highlands, the more rugged crater filled part of the Moon. The darker areas are the so-called lunar seas, huge lava filled craters. Note that they appear to be roughly circular. They are thought to be the result of large asteroid impacts that occurred four billion years ago during what is known as the late heavy bombardment. The late heavy bombardment is still controversial. One theory has that the outer planets changed their orbits in time disrupting the two areas of small bodies, the asteroid belt inside Jupiter’s orbit and the Kuiper belt beyond Neptune, sending some of them into the inner solar system.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon at low magnification this evening, May 28, 2020 with the English names for the visible lunar seas. Created using Stellarium.
06/25/2015 – Ephemeris – Lunar seas and highlands tell the story of the Moon’s history
Ephemeris for Thursday, June 25th. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32. The Moon, 1 day past first quarter, will set at 2:26 tomorrow morning and tomorrow the Sun will rise at 5:58.
Tuesday I talked about the brightness variation on the Moon, the bright and ancient highlands and the darker areas called seas, but a large asteroid impact areas that welled up magma from the moon’s interior erasing prior craters. The dark seas were created after most cratering had ended, or they’d be heavily cratered too. They seem to have occurred about 4 billion years ago, about 500 million years after the Moon formed. This appeared to be a period when the giant planets came closer to the Sun than they are now, before retreating again. This period is called the late heavy bombardment. Not all astronomers give it credence, but it bears out what we see in planetary systems around other stars.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon tonight with pointers to seas near the crater Copernicus and the highlands near the crater Tycho. 10:30 p.m. June 25, 2015. Created using Virtual Moon Atlas.
The Lunar seas near the crater Copernicus showing the smooth surface with relatively few craters. Credit: Virtual Moon Atlas with the texture from NASA’s Lunar Reconnaissance Orbiter. The lunar phase was omitted.
The Lunar highlands near the crater Tycho showing a surface saturated with craters. Credit: Virtual Moon Atlas with the texture from NASA’s Lunar Reconnaissance Orbiter. The lunar phase was omitted. Both images are shown to the same scale.
06/23/2015 – Ephemeris – What can you tell about the appearance of the Moon to the naked eye?
Ephemeris for Tuesday, June 23rd. Today the Sun will be up for 15 hours and 34 minutes, setting at 9:32. The Moon, 1 day before first quarter, will set at 1:31 tomorrow morning and tomorrow the Sun will rise at 5:57.
The Moon is at nearly half phase or first quarter. The unaided eye can see that the Moon has darker and lighter areas. The Greeks, who thought the objects in the heavens were perfect thought that the Moon was a silvery sphere. They never quite figured out why the moon had this mottled appearance. So why are the bright parts different from the darker parts? The bright parts are called the highlands and are the oldest part of the Moon’s surface. It’s saturated with craters from impacts since the Moon formed. The dark areas are roughly circular, and are really vast craters that penetrated through the Moon’s crust to bring up molten lava that repaved the surface of the Moon some 500 million years after it formed.
Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The Moon tonight (June 23, 2015). Look at the difference in the surface albedo (reflectance) between the light and dark areas and wonder about their origins. Created using Virtual Moon Atlas.
03/29/2012 – Ephemeris – The moon tonight
Ephemeris for Thursday, March 29th. The sun will rise at 7:28. It’ll be up for 12 hours and 38 minutes, setting at 8:06. The moon, 1 day before first quarter, will set at 2:55 tomorrow morning.
Tonight’s moon will be nearly half full. The gray patches on the moon are from the upper right the sea of Crises, Below it is the sea of fertility, centered on the moon’s equator is the sea of Tranquility. Above that is the scallop shaped sea of Serenity. One of the interesting craters in viwe for a telescope now is the ruined crater Julius Caesar. It’s on the edge of Tranquility near Serenity. This is an ancient crater whose crater walls were breached by the impact that created the sea of Tranquility, so it kind of looks like the letter C. So how did this crater become named for a Roman Emperor? My only guess is that it was for his calendar reform giving us the 365 day year with a leap year every 4th. This is also a good time to check out the rest of the moon.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The moon at 10 p.m. 3/29/2012. Created using Virtual Moon Atlas.
03/08/2012 – Ephemeris – The full moon
Ephemeris for Thursday, March 8th. The sun will rise at 7:06. It’ll be up for 11 hours and 33 minutes, setting at 6:40. The moon, at full today, will rise at 7:30 this evening.
The full moon, contrary to what you’d think is a poor time to observe it. The moon is essentially gray on gray. And at full moon we are looking at the moon from about the same perspective as the sun, so there are no shadows to delineate its fine features. Since the actual instant of full moon occurred at 5 this morning, some shadows will be creeping in on the moon’s upper right face as it is seen in the evening. Full moon is the best time to see the maria or lunar seas, the dark areas that make up the man in the moon. In binoculars can be seen the bright rays emanating from the crater Tycho near the south end of the moon. Other craters have rays too, but none so long and distinctive. Night by night for the next two weeks the moon’s illuminated landscape will wane.
* Times are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
The image below is of the waxing gibbous moon presumably from last Sunday night. The phase fits Virtual Moon Atlas for that date. And I received the photo Monday. many of the full moon features including the maria and the crater Tycho can be seen on it. Click on it to see the larger version.
The gibbous moon 03/04/2012 by Scott Anttila
This is from Scott: “The full-size image is huge, a 6 panel mosaic by my DSLR in the (Celestron) C11. It has had the saturation boosted to show detail in the seas that otherwise is difficult if not impossible to detect. You can also see where different minerals are located in the highland areas. Not many people like this view of the moon, I’m fairly fond of it.”
Bob Moler's Ephemeris Blog 