Introduction and Monthly Reminders
The first half of the month brought mountain snow and valley rain over much of Utah. While it has been cooler, it is still unusually warm for this time of the year. During the short breaks in the clouds, the evening planets and constellations could easily be seen, in addition to Venus and early morning stars. Due to the active Sun, there was an unusual opportunity to view the northern lights over Utah. Unfortunately, it was stormy during those days from my location.
Observers may still have the chance to view the leftover meteors from the Geminids. The Ursids are still fast approaching, with their peak on the evening of the 21st and morning of the 22nd. The Winter Solstice will occur on the 21st. Observers can still watch three asteroids reach opposition: Vesta (21st), Metis (22nd), and Astraea (27th).
The Moon
The next planet out from the Sun is the Earth. Instead of discussing the Earth, the Moon would be a more appropriate subject. The Moon is the closest astronomical object to the Earth and is the only natural satellite to our planet. The most popular theory is that a Mars-sized object collided with the Earth billions of years ago, causing debris from the impact to eventually coalesce, forming the Moon. The size of the Moon is roughly one-third of the size of the Earth. If the Earth were the size of a nickel, the Moon would be about the size of a green pea.
The Moon lies, on average, approximately 239,000 miles from the Earth. The orbit of the Moon around the Earth is not a perfect circle, so this distance varies, with the apogee being about 252,100 miles and its perigee at 225,600 miles. This change in distance means that the Moon appears slightly larger when it is closest to the Earth, a phenomenon known as a supermoon. The Moon is moving away from the Earth at the face-melting speed of about one inch per year.
As an observer, an individual may notice that they only ever see one side of the Moon. This is due to the Moon being tidally locked with the Earth. It is thought that after the collision between a Mars-sized object with the Earth, the debris that was flung off the two bodies that later joined together to create the Moon, was molten debris. As the Moon orbited the Earth and cooled, the heavy materials were pulled toward the Earth due to its gravity. When I think of this theory, I think of a piece of bread with peanut butter on it. As the bread falls to the ground, it usually flips, so the peanut butter lands face down.
Like Mercury and Venus, the Moon goes through phases. Unlike the inner two planets, the Moon can reach a "full" phase or have the Earth-facing side completely lit up from the Sun. It takes the Moon about 27 days to complete one full rotation around the Earth. During this rotation around the Earth, the phases of the Moon change, typically going from Full phase to Full phase in 27 days.
During its orbit around the Earth, the Moon can pass directly between the Earth and the Sun, casting its shadow on the Earth and creating an eclipse. Depending on where an individual lies on the eclipse path, they may see a total eclipse, where the maximum amount of the Moon blocks the Sun from view, or a partial eclipse, where only part of the Moon blocks the Sun. As previously mentioned, the orbit of the Moon around the Earth is not a perfect circle, so the Moon can be closer (perigee) or further (apogee) from the Earth. When the Moon is at apogee during an eclipse, we experience an Annular Solar Eclipse, like the one many Utahns experienced in October 2023. During an Annular Solar Eclipse, the Earth-Moon distance is too great for the entirety of the Sun to be blocked. Check out the two images below that I took during the Annular Solar Eclipse from Richfield, Utah.
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| Image taken with my phone through my astronomy binoculars. |
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| Annular Solar Eclipse taken with my phone. Focus on the reflection above the Sun. |
When the Moon is at perigee during an eclipse, we experience a Total Solar Eclipse like what occurred most recently in August of 2017 across much of the US and will again in April of 2024. During this type of eclipse, the entire Sun and its light will be blocked by the Moon, revealing planets, stars, and the corona of the Sun. Check out these two images that I took during the Total Solar Eclipse in 2017 from Mud Lake, Idaho.
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| Total Solar Eclipse taken with my phone in 2017. |
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| "Diamond Ring" taken during the Total Solar Eclipse in 2017 with my phone. |
The Moon is the only body in the solar system, other than the Earth, that humans have visited. The first Moon landing occurred on 20 July 1969 with Apollo 11 and involved the NASA astronauts Neil Armstrong, Buzz Aldrin, and Michael Collins. A total of 24 humans and over 100 robots have visited the surface of the Moon. These missions have returned over 800 pounds of Moon rocks to the Earth.
There are currently seven active missions on and around the Moon from different countries worldwide. The Lunar Reconnaissance Orbiter (LRO) from NASA has been mapping the surface of the Moon since 2009, has collected a treasure trove of data, and has located some possible landing sites for future crewed missions. Several future missions are planned for our closest celestial neighbor, including Artemis, a mission designed by NASA to land humans on the Moon as early as 2025.
Be sure to check back soon for new posts on upcoming astronomical events in 2024 and my January Monthly Night Sky Report.
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| Now get outside and look up! |
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