Astronomical Research II
Commentary: Toshihiro Handa
(professor at Kagoshima University Science Department)
Cooperation: Yamato 2199 Production Committee
The writer gives public performances about the voyage of Yamato 2199 at the Synra Dome in the Science and Technology Museum. As an astronomer, his main occupation is to study the Milky Way Galaxy by radio observations. He was in charge of scientific research for the Yamato 2199 TV series and the new movie Ark of the Stars.
Readers will be aware that more than a year has passed since the October 2013 issue of Star Navi. That is a longer time than Yamato’s round trip between Earth and Iscandar. Time flies like an arrow. At the time, the story was unfinished on both TV and in theaters, with the Battle of the Rainbow Star Cluster still ahead. Therefore, this time we’ll introduce astronomy-related topics that appeared in the latter part of the story.
The stage of Yamato 2199 (The Large Magellanic Galaxy)
Iscandar and Garmillas, toward which Yamato travels, are fictional planets, but the Large Magellanic Galaxy is a real celestial body. It is located near our Milky Way Galaxy, but is about 1/10 the size. In the first Space Battleship Yamato series, it was said that “the Large Magellanic Cloud is 148,000 light years away,” but after measuring the distance with multiple methods, it was announced with confidence in 2013 that the value is 163,000 light years. This Large Magellenic Galaxy becomes the stage for the end of the Yamato 2199 TV series.
The destination is the fourth planet of the star Salezar
After the fierce battle in the Tarantula Nebula, Space Battleship Yamato made its long-awaited breakthrough when it warped-out in the vicinity of the fixed star Salezar. It was near Epitora, a gas planet similar to Saturn. Since we only have Jupiter and Saturn to compare to when observing the surface features of gaseous worlds, an astronomer could only expect that Epitora is a similar planet, but who can say if that’s true in the end?
The Dessler gun attacks Yamato. It is a secret weapon of Garmillas, and its firing point is midway between the twin fourth planets (Garmillas and Iscandar). This is the spot where the gravity of the two planets is balanced, which is referred to as Lagrange Point 1 in celestial mechanics, or L1 for short. (Though it was Euler who discovered this, rather than LaGrange.) This is how it’s shouted in a line by Yuria Misaki, who is filling in for Yuki Mori as the person in charge of search operations.
Significantly, at this time, two distant planets are depicted. One is Garmillas, the other is Iscandar. On the screen, both of them are about the same size, but spaced about 22 diameters apart.
When we watch the movements of people on Garmillas and Iscandar, the surface gravity of these planets seems to be about the same as on Earth. Surface gravity can be deduced by the planet’s diameter and mass. When the average density is the same, it becomes stronger in proportion to the diameter. Comparing the rocky planets Mercury, Venus, Earth and Mars, Earth is definitively the largest and has the stronger surface gravity. Therefore, it is reasonable to deduce that Garmillas and Iscandar have about the same diameter and mass as Earth. Therefore, the diameter is about 12,700km.
A double planet with a contrasting appearance
Yamato barely manages to escape the enemy attack and makes its destination Garmillas, the stronghold of the enemy. Although most of Garmillas’ surface is green, the characteristic of this planet is that it has vast underground cavities. If a planet with similar topography exists, there is not one in our solar system. So if such a planet is discovered in reality, geologists and planetary physicists will have to rack their brains to explain it.
By contrast, a sea covers most of Iscandar’s surface. It has the same characteristics as Earth, and an arc-shaped archipelago. Given the diameter and distance of the similar planet, there must be about 280,000 km between the two. However, since the invisible line connecting them could be diagonal (as seen on screen), it might be a little farther.
If it is 380,000km, both their surfaces would be subjected to 80 times the tidal force Earth receives from the moon. It’s difficult to calculate the high and low tides that would be caused in the sea of Iscandar under this influence, but there is no doubt that huge tides would produce a sloping effect.
However, if tidal forces are large, they can affect rotational speed, and the planet would eventually come to match the rotational speed of its celestial partner. This is why the moon always shows its same face to the Earth. Considering this, I can expect that Iscandar and Garmillas would always show the same face toward each other. This is known as tidal locking.
By the way, if Earth and a similar celestial body orbited each other at a distance of 380,000km, the orbital period would be about 16 days. So the rotational period of Iscandar should be about 16 Earth days. The orbital period around their star, Salezar, is not clear, but over a single day on Iscandar, its impact would be much greater than the sun’s on Earth. However, when we see life on Iscandar, one day there is about the same as one day here.
If it hasn’t been long since these double planets were formed, it would mean the tides aren’t yet fixed. Rather than being born on these planets, could the people of Garmillas and Iscandar have emigrated from other worlds?
Saying that reminds me of something we should focus on. The base DNA sequence of Garmillas people and Earthlings is identical.
The feature film and the Panspermia hypothesis
There is a hypothesis that life on Earth originated in space rather than on the planet. This is called the panspermia hypothesis. This theory is based on the fact that amino acids recovered by spacecraft in the tails of comets could contribute to complex molecules discovered in interstellar dust, which may have fallen to Earth and played a part in the development of life. If this is correct, the possibility is high that biological creatures similar to those on Earth could be found on various planets in space. However, identical base DNA sequences could not happen by accident.
Besides Earth and Garmillas, there is Iscandar. What kind of secrets are there between these three planets? There is a rumor than something will be shown in Ark of the Stars, the new feature film to be shown in December…
A huge region of ionized hydrogen that exists in the Large Magellanic Galaxy. There is a massive cluster of stars in its center called R136a, which gives off strong ultraviolet rays that ionizes the gas between the stars, and produces a variety of spectral lines. This is the setting Garmillas General Domel chooses for the Battle of the Rainbow Star Cluster. Because its density is less than a quadrillionth of Earth’s atmosphere, a space ship would not be washed away by gas turbulence as seen on TV.
Double planetary system
A pair of stars that orbit each other is called a binary star. Therefore, a pair of planets such as Garmillas and Iscandar should be called a double planet. In fact, Charon is a satellite of Pluto. But since the two bodies share a common center of gravity, International Astronomical Union general meeting of 2006 proposed that the term “double planets” be included in a draft to define the planet.
Special thanks for astronomer Marc Hairston for input. Extra information from Marc: it’s generally held that once planets get to the size of the Earth or larger, you couldn’t have a true double planet where both planets are roughly the same mass. It would be unstable and over geologic time (10s of millions of years or so) the orbits would become unstable and either one would escape or, more likely, they would collide and coalesce into a single body.
Special thanks to Neil Nadelman for translation support