Archive
02/26/2021 – Ephemeris – Origin of the Moon
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
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
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 sample. Credit Larry Taylor U of TN Knoxville from https://ntrs.nasa.gov/api/citations/20090026015/downloads/20090026015.pdf
02/24/2021 – Ephemeris – Let’s search for the naked-eye planets for this week
This is Bob Moler with Ephemeris for Wednesday, February 24th. Today the Sun will be up for 10 hours and 55 minutes, setting at 6:24, and it will rise tomorrow at 7:26. The Moon, 3 days before full, will set at 6:56 tomorrow morning.
Let’s search for the naked-eye planets for this week. Unfortunately the only one you’ll find is Mars. The other four are hanging out in the direction of the Sun and won’t be seen for a week or two. They’ll be first seen low in the morning sky. Mars can be found high in the west-southwest and below the Pleiades at 8 pm tonight. Mars is moving rapidly eastward. It just entered the constellation of Taurus the bull, which is a lot wider than Aries, astronomically*, and will set at 1:26 am. Of the outer planets Mars is the fastest, being the nearest to the Sun, and to the Earth, so unlike Jupiter, Saturn and the stars which rise and set about four minutes earlier each night, Mars sets about a minute earlier each night now.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
* Astrologically the all the constellations or signs of the zodiac are 30 degrees wide. According to the International Astronomical Union (IAU) Aries is 25 degrees wide along the ecliptic, while Taurus is 37 degrees wide as measured using the Stellarium planetarium program. I do astronomy on Ephemeris, and consider astrology astronomy’s illegitimate parent.
Addendum
Mars finder animation with 3 layers: Unannotated chart, Labels and constellation lines added, and boundaries added. Created using Stellarium and GIMP.
The gibbous Moon as it might be seen in binoculars this evening at 8 pm tonight, February 24, 2021. Created using Stellarium.
Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on February 24, 2021. The night ends on the left with sunrise on the 25th. There is a planet traffic jam in the morning and the labels for Jupiter and Mercury overlap. Unfortunately these planets rise too soon before the Sun to be seen for us up north. It is a great sight for Southern Hemisphere observers. Click on the image to enlarge. Created using my LookingUp program.
02/23/2021 – Ephemeris – The Perseverance rover landed on Mars taking video all the way down
Note: There was a news conference at JPL, Monday at 2 pm EST where videos of the parts of the landing were shown. Most hadn’t made it to the https://mars.nasa.gov website by Monday night. The news conference with the videos can be found on NASA TV, NASA’s YouTube channel and other sites.
This is Ephemeris for Tuesday, February 23rd. Today the Sun will be up for 10 hours and 52 minutes, setting at 6:22, and it will rise tomorrow at 7:28. The Moon, halfway from first quarter to full, will set at 6:15 tomorrow morning.
It looks like the Perseverance Rover was gently lowered to a flat spot in Jezero crater on Mars about a kilometer or two from the edge of the river delta it was aiming to be near. It is in the midst of checkouts and the unfolding of its masts and its various appendages. For the third time the Mars Reconnaissance Orbiter was able to take a picture of the entry craft on its parachute seen above the delta, as it had with Curiosity and the Phoenix lander before all the while performing its communication relay duties. A few images have come back from Percy, as the Rover is nicknamed as I record this Sunday night. By Monday Percy should have sent back more images and perhaps parts of the landing video.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
A frame from the video looking down at the Perseverance rover from the Sky Crane. In the video as the rover neared the ground it was enveloped by a cloud of dust, so the support lines simply disappeared into the cloud of dust that enveloped the rover. Click on the image to enlarge. Credit NASA/JPL.
The Perseverance rover on the parachute over Jezero crater from the Mars Reconnaissance Orbiter. The circle on the image is the point where the rover landed. Click on the image to enlarge. Credit NASA/JPL-Caltech/University of Arizona.
02/22/2021 – Ephemeris – What’s happening with NASA’s Artemis Moon Program
This is Ephemeris for Monday, February 22nd. Today the Sun will be up for 10 hours and 49 minutes, setting at 6:21, and it will rise tomorrow at 7:30. The Moon, 3 days past first quarter, will set at 5:28 tomorrow morning.
It appears that the Artemis Moon Program is still on schedule despite a new administration and a setback when a few weeks ago an all up 8 minute firing of the 4 main engines of the Space Launch System Core Stage aborted after little over a minute. (NASA is scheduled to repeat this Green Run test this week) The first launch of the complete rocket is slated for later this year with an uncrewed lunar orbit mission. Recently NASA announced that Elon Musk’s SpaceX was awarded the contract to launch the first two lunar gateway modules on a single Falcon Heavy rocket. The two modules, Power and Propulsion Element (PPE) and Habitation and Logistics Outpost (HALO) will be placed in low earth orbit. From there the PPE would use its ion engines to propel the two modules out to a near rectilinear halo orbit of the Moon over many months.
The astronomical event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
SLS first green run of all 4 RS-25 engines mounted on the core stage for the Artemis-1 mission on a test stand at Stennis Space Center in Mississippi. Credit: NASA.
An artist’s depiction of the Lunar Gateway PPE and HALO modules in lunar orbit. The PPE module is the part with the solar panels. Credit: NASA.
02/19/2021 – Ephemeris – Let’s look at the first quarter Moon tonight
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.
A telescopic like view of the Moon via the Virtual Moon Atlas pointing out the craters discussed in the text.
Ranger 9 Image of Alphonsus #1. Credit NASA/JPL.
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.
02/18/2021 – Ephemeris – The Perseverance Rover will land on Mars this afternoon
This is Ephemeris for Thursday, February 18th. Today the Sun will be up for 10 hours and 37 minutes, setting at 6:15, and it will rise tomorrow at 7:36. The Moon, 1 day before first quarter, will set at 1:30 tomorrow morning.
Later this afternoon the Perseverance Rover will land in Jezero crater on Mars. NASA will have a live Internet feed from the Jet Propulsion Laboratory starting at 2:15 pm EST (19:15 UTC). Atmospheric entry will be at 3:48 pm EST (20:48 UTC), landing at 3:55 pm EST (20:55 UTC). This is Earth received time. The events actually happened 11 minutes 22 seconds earlier on Mars. Though cameras on the spacecraft will be recording the landing activity it will not be sent to Earth in real time due to the weak signal during entry. The spacecraft will be sending tones only for specific events during what is called EDL, Entry, Descent and Landing or “Seven Minutes of Terror”. If all goes well the first images will be taken and sent of its surroundings. And in the next weeks we’ll get an actual replay sent back of the landing with color and sound. It will be so cool!
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Links
NASA on YouTube: https://www.youtube.com/results?search_query=nasa
NASA TV: https://www.nasa.gov/multimedia/nasatv/#public
Graphic of the Entry, Descent and Landing of the Perseverance Rover. Click on the image to enlarge. Credit: NASA/JPL.
Perseverance drilling for a sample in Jezero crater. Artist drawing – NASA/JPL
02/17/2021 – Ephemeris – Let’s search for the naked-eye planets for this week
This is Bob Moler with Ephemeris for Ash Wednesday, Wednesday, February 17th. Today the Sun will be up for 10 hours and 34 minutes, setting at 6:14, and it will rise tomorrow at 7:38. The Moon, 2 days before first quarter, will set at 12:27 tomorrow morning.
Let’s search for the naked-eye planets for this week. Unfortunately the only one you’ll find is Mars. The other four are hanging out in the direction of the Sun and won’t be seen until spring. They’ll be first seen in the morning sky. Mars can be found high in the southwest and above the waxing crescent Moon at 8 pm tonight. They will be even closer Thursday night. Mars is increasing its speed eastward through the constellation of Aries the ram, which it’s two thirds the way through, and will set at 1:32 am. Of the outer planets Mars is the fastest, being the nearest to the Sun, and the Earth, so unlike Jupiter, Saturn and the stars which rise and set about four minutes earlier each night, Mars sets less than a minute earlier each night now.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Mars and the Moon in the southwestern sky at 8 pm tonight, February 17, 2021. Created using Stellarium.
The Moon as it might appear tonight at 8 pm, February 17, 2021. Created using Stellarium.
Planets and the Moon at sunset and sunrise of a single night starting with sunset on the right on February 17, 2021. The night ends on the left with sunrise on the 18th. There is a planet traffic jam in the morning and the labels for Jupiter and Mercury overlap. Unfortunately these planets rise too soon before the Sun to be seen for us up north. It is a great sight for Southern Hemisphere observers. Click on the image to enlarge. Created using my LookingUp program.
02/16/2021 – Ephemeris – Perseverance lands on Mars in two days
This is Ephemeris for Fat Tuesday, Tuesday, February 16th. Today the Sun will be up for 10 hours and 32 minutes, setting at 6:13, and it will rise tomorrow at 7:39. The Moon, 3 days before first quarter, will set at 11:24 this evening.
In two days, Thursday afternoon, the Perseverance Rover will land on the planet Mars in a crater call Jezero. It’s mission to actually look for evidence of past life, fill specimen tubes to be cached for later pickup and returned to earth by a future mission, presumably by the end of the decade. It is also bringing a helicopter drone named Ingenuity to check out the feasibility of using future aircraft in Mars rarefied atmosphere. The vehicle, including the back shell and descent stage sports 23 cameras. Even Ingenuity has 2 cameras. That shouldn’t be a big deal today. Heck, my smartphone has 5 cameras, each with lots more megapixels than the digital camera I bought 15 years ago. Only two days to go to landing.
The event times given are for the Traverse City/Interlochen area of Michigan. They may be different for your location.
Addendum
Graphic of the Entry, Descent and Landing (EDL) of the Perseverance Rover. Click on the image to enlarge. Credit: NASA/JPL.
02/15/2021 – Ephemeris – For a few months the Earth had two moons
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
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.
