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02/26/2021 – Ephemeris – Origin of the Moon

February 26, 2021 Leave a comment

This is Ephemeris for Friday, February 26th. Today the Sun will be up for 11 hours and 1 minute, setting at 6:26, and it will rise tomorrow at 7:23. The Moon, 1 day before full, will set at 7:59 tomorrow morning.

The origin of the Moon is a question that has vexed astronomers for years. Did it break off the molten Earth like a cell dividing? Was it captured by passing too close to the Earth? Neither is satisfactory. Chemical elements have different isotopes depending on the number of neutrons in their nucleus. The rocks brought back by the Apollo astronauts show that the isotopes of the elements in the rocks are the same as for the Earth. We know that Mars and the asteroids have different isotope ratios. The hypothesis that seems most likely is that another planet, the size of Mars collided with the 100 million-year-old Earth in a glancing blow that gave rise to a disk of material that eventually coalesced to form the Moon.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

How the Moon may have formed

A progression of how the Moon may have formed by a small protoplanet crashed into the Earth. Credit: Brian Koberlein.

02/25/2021 – Ephemeris – Moon Dust, bad stuff

February 25, 2021 Leave a comment

This is Ephemeris for Thursday, February 25th. Today the Sun will be up for 10 hours and 58 minutes, setting at 6:25, and it will rise tomorrow at 7:24. The Moon, 2 days before full, will set at 7:30 tomorrow morning.

One of the big problems that will have to be solved before the Artemis program sets up a permanent base on the Moon is what to do about lunar soil or Moon dust. That stuff gets into everything. The Apollo astronauts said it smelled like gunpowder. Unlike beach sand the particles aren’t rounded, but angular, being produced by rocks being hit by meteoroids large and micro over the eons by space weathering. With no atmosphere small particles can even weld themselves together. Though no studies have been done, any brought into the habitat would do damage to the lungs, like that to miners on Earth. Moon dust has compromised the seals on the containers of soil the Apollo crews brought back from the Moon.

The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Lunar soil

Lunar soil sample. Credit Larry Taylor U of TN Knoxville from https://ntrs.nasa.gov/api/citations/20090026015/downloads/20090026015.pdf

02/19/2021 – Ephemeris – Let’s look at the first quarter Moon tonight

February 19, 2021 Comments off

This is Ephemeris for Friday, February 19th. Today the Sun will be up for 10 hours and 40 minutes, setting at 6:17, and it will rise tomorrow at 7:34. The Moon, at first quarter today, will set at 2:32 tomorrow morning.

I love a first quarter Moon. The terminator or sunrise line cuts the Moon in half. Lots of craters are easily seen due to the long shadows cast by their crater walls. Best seen in a small telescope or strong pair of binoculars is a three crater chain just below left of the center of the Moon. The top and largest crater is Ptolemaeus. Below and connected to it is Alphonsus. A bit below Alphonsus is Arzachel. Alphonsus is the interesting one. In the pre-Apollo days amateur and some professional astronomers saw glows or mists in Alphonsus. In 1958 a Russian astronomer obtained spectra of one such mist. In 1965 the last Ranger mission to impact the Moon was sent to Alphonsus, but it didn’t find anything unusual.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The first quarter Moon tonight at 8 pm, February 19, 2021, as it might be seen in binoculars. Created using Stellarium.

First Quarter Moon

A telescopic like view of the Moon via the Virtual Moon Atlas pointing out the craters discussed in the text.

Ranger image 1

Ranger 9 Image of Alphonsus #1. Credit NASA/JPL.

Ranger Program

Left: The Ranger spacecraft. Right: The floor of the crater Alphonsus form Ranger 9. Only the last 3 spacecraft were successful. They transmitted images all the way down as they crashed into the Moon. Credit NASA/JPL.

02/15/2021 – Ephemeris – For a few months the Earth had two moons

February 15, 2021 Comments off

This is Ephemeris for President’s Day, Monday, February 15th. Today the Sun will be up for 10 hours and 29 minutes, setting at 6:11, and it will rise tomorrow at 7:41. The Moon, halfway from new to first quarter, will set at 10:22 this evening.

The Moon tonight is a waxing crescent. A four-day-old moon. In binoculars, it shows one complete lunar sea, the Sea of Crises, or if seen on a moon map, Mare Crisium. Speaking of the Moon, for the last few months the Earth had a second moon, with the asteroid designation 2020 SO. This was traveling slowly behind the Earth, and is suspected to be the Centaur upper stage of the Surveyor 2 lunar landing craft launched in 1966. It ended up orbiting the Sun. 2020 SO took a loop and a half around the Earth and is heading back in solar orbit. The ascent stage, Snoopy, from Apollo 10 is also in solar orbit. I hope one day it can be captured on a close approach and brought back to the Earth or the Moon for display. That would be really cool!

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Binocular Moon

The moon as it might appear tonight, at 8 pm, February 15, 2021. Mare Crisium is the round gray sea near the lower right edge. Created using Stellarium.

Animation of object 2020 SO as it encounters the Earth. Also shown is the orbit of the Moon and geostationary satellites. Credit: NASA/JPL – Caltech.

 

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01/28/2021 – Ephemeris – Checking out the full Moon in binoculars

January 28, 2021 1 comment

This is Bob Moler with Ephemeris for Thursday, January 28th. Today the Sun will be up for 9 hours and 40 minutes, setting at 5:46, and it will rise tomorrow at 8:04. The Moon, at full today, will rise at 5:37 this evening.

The winter full moon rises very high in the sky. It follows a path across the sky at night that the Sun will take six months from now in July. On the full moon with binoculars or small telescope most craters are not very visible due to the lack of shadows. There are exceptions, those with dark or bright floors. The lunar seas are the large dark areas. These positions are for the early evening, as the Moon rises. Grimaldi can be seen as a dark ellipse near the lower left edge. Plato another dark ellipse is in the upper left. A bright spot with a darker circle around it on the lower right is the crater Tycho, which has several rays of ejecta laid out over long distances across the face of the Moon. Finally, there’s a bright spot on the left side of the Moon. That is the crater Aristarchus.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Annotated full Moon

Annotated full Moon. Major seas in upper case. Prominent craters in lower case. See text below. The image is rotated for 8 pm in late January. Credit Bob Moler.

Lunar seas

A – Mare Crisium (Sea of Crises)
B – Mare Fecunditatus (Sea of Fertility)
C – Mare Tranquillitatis (Sea of Tranquility)
D – Mare Serenitatis (Sea of Serenity)
E – Mare Imbrium (Sea of Showers)
F – Oceanus Procellarum (Ocean of Storms)
G – Mare Nubium (Sea of Clouds)
H – Mare Humorum (Sea of Moisture)
I – Mare Nectaris (Sea of Nectar)

Craters

a – Grimaldi
b – Plato
c – Tycho
d – Aristarchus
e – Copernicus (Not mentioned in the program due to time constraints)

01/19/2021 – Ephemeris – The Moon is a pretty straight up orb

January 19, 2021 Comments off

This is Ephemeris for Tuesday, January 19th. Today the Sun will be up for 9 hours and 20 minutes, setting at 5:33, and it will rise tomorrow at 8:13. The Moon, 1 day before first quarter, will set at 12:36 tomorrow morning.

The Earth has an axial tilt to its orbit of the Sun of 23 ½ degrees. So the Earth has seasons, the cycle of which last one orbit of the Sun, or one year. Our Moon on the other hand has a 5 ½ degree axial tilt to its orbit of the Earth, but more importantly for future moon colonists, has only a degree and a half tilt compared to the Earth’s own orbit of the Sun. So there are spots at the north and south poles that never get the Sun’s heat or light. The Moon’s south polar region is more rugged with more and smaller craters than the north, so has collected, over the eons, what seems to be a great amount of water ice that is cold enough to be stable in the vacuum of space. That makes it an ideal place to build a sustainable lunar base.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Map of water at the Moon's poles

The Moon’s south pole area on the left and north pole on the right. The cyan color shows shadowed areas where ice is located. Credit NASA

11/23/2020 – Ephemeris – Our Moon is different

November 23, 2020 Comments off

This is Bob Moler with Ephemeris for Monday, November 23rd. Today the Sun will be up for 9 hours and 16 minutes, setting at 5:07, and it will rise tomorrow at 7:52. The Moon, 2 days past first quarter, will set at 1:55 tomorrow morning.

The Earth’s Moon is different from most other moons. First it is very big when compared to the Earth. The Moon is a bit more than quarter the Earth’s diameter. Only Pluto’s moon Charon is larger compares to its primary, being half the size of Pluto. Most big moons orbit over their planet’s equator. Our Moon orbits the Earth close to the plane of Earth’s orbit of the Sun. That’s why the Moon is seen passing the planets each month. The Moon is too big to have been captured by the Earth in a chance flyby. The moon rocks brought back during Apollo showed that the Moon was made of the same crustal material as the Earth, so the impact theory was put forth that the Moon was the result of a collision of the Earth and a Mars sized body soon after they were formed.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

The Moon's orbit vs the ecliptic

The Moon’s orbit (red) vs the ecliptic or plane of the Earth’s orbit (orange). The Moon’s orbit is tilted to the Earth’s orbit by 5 degrees. This is for 4:30 pm or a little more than a half hour before sunset. The black sky is due to removing atmospheric scattering in the program. Click on the image to enlarge. Created using Stellarium.

In the image note that the Moon’s orbit crosses the ecliptic just east of the Sun’s position. That crossing point is called the Moon’s descending node, since the Moon’s eastward motion will take it from north of the ecliptic to south of it. When the Sun is close to a node eclipses can occur. The ascending node is at the opposite side of the ecliptic so both solar and lunar eclipses occur in an eclipse season that lasts about a month.

An indeed there will be a penumbral eclipse of the Moon on the 30th, and a total solar eclipse for Chile and Argentina December 14th. The nodes don’t stay in one place, but they move westward, making one rotation around the ecliptic in 18.61 years. Since the nodes are moving westward it is called the regression of the nodes. So eclipse seasons occur about every 5 2/3 months, moving backwards in the calendar.

11/19/2020 – Ephemeris – Looking at the crescent Moon tonight

November 19, 2020 Comments off

This is Ephemeris for Thursday, November 19th. Today the Sun will be up for 9 hours and 24 minutes, setting at 5:10, and it will rise tomorrow at 7:47. The Moon, 2 days before first quarter, will set at 9:31 this evening.

Tonight the Moon shows two seas. Easiest to spot is Mare Crisium or the Sea of Crises. It is a large gray basin near the edge. It is easily spotted in binoculars. Because it’s near the Moon’s limb or edge it is foreshortened into an ellipse, with the long axis running north and south. In actuality, it is elliptical with the long axis east and west. It looks funny on a geologic map of the whole moon or a Moon globe. Its dimensions are 345 by 375 miles (570 by 620 kilometers). It’s really a crater as are all seas whose impact asteroid reached down to the Moon’s magma and caused lava to well up to produce the flat floor. When the sunlight is low on the sea telescopes show wrinkle ridges that appear where successive lava flows have stopped and solidified.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Crescent Moon-Mare Crisium

Crescent Moon with pointer to Mare Crisium at 8 pm tonight, November 19, 2020.

Mare Crisius via LRO

Mare Crisium from overhead with Lunar Reconnaissance Orbiter. The vertical lines are due to the north-south scans by the polar orbiting satellite. Credit: NASA/LRO/Virtual Moon Atlas.

11/05/2020 – Ephemeris – Water found on the daylit side of the Moon

November 5, 2020 Comments off

This is Ephemeris for Thursday, November 5th. Today the Sun will be up for 9 hours and 58 minutes, setting at 5:25, and it will rise tomorrow at 7:28. The Moon, 3 days before last quarter, will rise at 8:55 this evening.

Last week NASA announced some results from their SOFIA airborne observatory. They had detected the spectral signature of water in a large crater on the Moon named Clavius. This was a high latitude crater, 58.6 degrees south. Supposedly one could process a cubic meter of the regolith to extract a half liter of water. Clavius, which science fiction fans will note was the location of the American base on the Moon in 2001 a Space Odyssey. It is also one of my favorite lunar craters, one of the largest with a distinctive arc of diminishingly sized craters in its floor. As far as resources go, we’ve just literally scratched the surface of the Moon in its equatorial regions with our Apollo and other country’s robotic missions.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

Moon with Clavius circled

The Moon as seen from Australia (south up) with the crater Clavius circled. This is the same view of the Moon that users of a Newtonian reflector telescope in the northern hemisphere see, and how I first explored the Moon with my reflecting telescope. Source abc.net.au.

Closeup of Clavius

Closeup of Clavius from the Lunar Reconnaissance Orbiter. Credit: NASA/LRO.

Sophia Airborne Observatory

The SOFIA Airborne Observatory. A modified Boeing 747 with a 106 inch (2.7 meter) telescope mounted crosswise in its fuselage. It is a joint project between NASA and the German Aerospace Center (DLR) and for some reason always on the verge of being canceled. Credit: NASA.

SOFIA is of course an acronym for Stratospheric Observatory for Infrared Astronomy. For more on SOFIA click here: https://www.nasa.gov/mission_pages/SOFIA/index.html.

10/26/2020 – Ephemeris – Why does everyone want to go to the Moon’s south pole?

October 26, 2020 Comments off

This is Bob Moler with Ephemeris for Monday, October 26th. Today the Sun will be up for 10 hours and 26 minutes, setting at 6:39, and it will rise tomorrow at 8:14. The Moon, 3 days past first quarter, will set at 4:01 tomorrow morning.

Why are the United States and other countries interested in the south pole of the Moon? Two reasons: Water and power. The Moon’s axial tilt to the Earth’s orbit is only a degree and a half. And I’ve seen a mountain peak at the south pole of the Moon sticking out in sunlight in a telescope on a crescent moon, with black all around it. While most of the Moon gets two weeks of daylight and another two of night, that peak is probably always in sunlight. And on the Moon there’s no atmosphere to diminish the strength of the Sun when its low in the sky. And there’s the floors of craters that have never seen the Sun where water ice and other volatile compounds from comets have collected over the eons.

The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.

Addendum

South pole ice

The south pole of the Moon where the presence of water ice is detected by the absorption of neutrons by the hydrogen atoms in the ice. Credit NASA/GSFC/SVS/Roscosmos.