Seven new satellites of Jupiter have been found, the total number is 91 | sorae Portal site to space

The answer to the question ‘Which planet has the most (natural) moons’ varies? ”depending on the time of year.

From October 8, 2019, to January 5, 2023, the planet with the most moons was Saturn. With the addition of nine moons on October 8, 2019, Saturn has 82 moons. (※ 1) , surpassing Jupiter, who was 80 years old at the time. One satellite was added on November 16, 2021, bringing the total number of Saturn’s moons to 83.

*1… This number does not include several small masses in Saturn’s A ring and three candidate satellites observed around the F ring. These have been missing since observation at a certain point, and presumably were temporary masses that lasted only a few years at length.

Meanwhile, Jupiter, which follows Saturn, added one new satellite on November 15, 2021, two on December 20, 2022, and two on January 5, 2023. So, the total number of satellites is 84, and it has recently regained its position from the planet with the most satellites of Saturn.

a relationship:Four new moons of Jupiter discovered the restoration site as the planet with the most moons(January 12, 2023)

Remember Scott S. Shepard, who is known for discovering many moons, presented seven new discoveries of Jupiter’s moons, which were published in the Asteroid Electronic Bulletin on January 19 and 29, 2023. And it was done. With Shepherd’s new discovery,The total number of moons of Jupiter is 91had become.

These moons have not yet been officially named, and have been given provisional designations according to naming conventions.「S / 2021 J 2」 「S / 2018 J 3」 「S / 2021 J 3」 「S / 2021 J 4」 「S / 2021 J 5」 「S / 2021 J 6」 S / 2018 J 4 」Attached. As you can see from the tentative tags, 2 of the seven were first observed in 2018, while the remaining five were first observed in 2021. (※ 2) . While it is not uncommon for a discovery to be recognized five or ten years after the first observation, this is a fairly fast pace.

*2 … For S/2021 J 6 only, the first observation record is October 2, 2010. This is because after the first observation on September 5, 2021, an older observation record was found by searching archives of previous data. For this reason, the temporary code is based on the year 2021.

【▲ Figure 2: Overview of the newly added seven satellites (the author estimates groups) (Picture source: Riri Ayae)】

【▲ Figure 3: Naming rules for temporary satellite symbols (Image credit: Riri Ayae)】

Of the five new satellites discovered this time, S/2018 J4 has particularly interesting properties. First, most of the new moons of Jupiter and Saturn are retrograde (satellites orbiting in the opposite direction of the planet’s rotation), but S/2018 J 4 is a retrograde satellite, which is a rare find. The orbital inclination and orbital radius of S/2018 J 4 are similar to “Calpo”, but Calpo’s orbit is completely elliptical with an orbital eccentricity (a numerical value representing the orbit’s ellipticity) of 0.4316. In contrast, the orbital eccentricity of S/2018 J 4 is 0.0573, which is very close to a full circle.

Calpo’s orbit is known to be constrained by a mechanical system called the Kozai mechanism. This is because the inclination of Calpo’s orbit is kept within a certain range due to the gravitational interaction between Jupiter’s moons. If this value is exceeded, the orbit will enter a highly elliptical orbit that reaches the vicinity of Jupiter’s Galilean satellites, and will either collide with the Galilean satellites or be ejected from Jupiter’s orbit. Due to its unique orbit, Carpo is the only satellite that belongs to the “Carpo constellation”.

S/2018 J 4, which orbits similar to Kalpo’s with these characteristics, should be a dynamically attractive satellite. S/2018 J 4 may be a second object in the Carpo group, or it may be in its own group, different from the Carpo group.

It is not known how many moons Jupiter and Saturn actually have. For example, Jupiter is estimated to have 600 satellites that are 800 meters or more in diameter. There is a good chance that more satellites will be discovered in the future as telescopes improve in resolution. Just days ago, I wrote an article explaining the discovery of a new moon of Jupiter based on Mr. Shepherd’s discovery report, but I didn’t expect the next one to come so soon. In the future, there may be another discovery report at an unexpected speed.

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Text: Rare Aya