In the sequence 0.4, 0.7, 1, 1.6,…, 5.2, 10, 19.6, that, as we saw last week, corresponds with remarkable precision with the successive distances of the planets to the Sun expressed in astronomical units, the missing term between 1.6 and 5.2 is 2.8. This sequence is obtained by dividing the successive values of n + 4 by 10, where n successively takes the values 0, 3, 6, 12, 24… Thus, for n = 0, (0 + 4): 10 = 0.4, which is the distance from Mercury to the Sun in UA.
This sequence was discovered by the German astronomer Johann Titus in 1766, was included by Elert Bode in his prestigious astronomy books (which is why it is known as the Titus-Bode Law) and stimulated the search for a new planet at a distance of 2.8 AU of the Sun, then, as Titus himself said, the Creator could not have left that gap empty. And, as we saw a couple of weeks ago, that search led to the discovery of the first object found in the asteroid belt: the dwarf planet Ceres, discovered in 1801 by the Italian astronomer Giuseppe Piazzi.
The issue of space mining sparked a lively debate (see comments from last week), and our “outstanding user” Manuel Amorós proposed, in this regard, the following problem:
10 speakers attend a Space Mining Congress. In any group that can be formed from 3 of them, there are at least two that are not known. Prove that there is a group of at least 4, where nobody knows each other.
The six dwarfs
Since Pluto was expelled from the planetary Olympus, the Solar System is no longer what it was. Although the planetitude Pluto was always questioned (it was thought that it was a satellite of Neptune), since its discovery, in 1930, until 2006 it was officially the ninth planet of the Solar System. But starting in the nineties of the last century, other celestial bodies of similar dimensions and characteristics began to be discovered in the same orbital area, with which astronomers saw themselves in the dilemma of expanding considerably (and indefinitely, given the continuous discovery of new celestial objects) the cast of the planets, or agree on a more restrictive definition. The issue was officially settled (although not without controversy) in 2006, when the International Astronomical Union (UAI) established a new definition of planet, according to which it was not enough for a celestial body to revolve around the Sun and have enough mass to have adopted the spherical shape due to its own gravity, but also had to reign alone in its orbital area, a condition that Pluto did not meet. And neither does Ceres, which is part of the asteroid belt. In this way, Pluto was degraded, and Ceres promoted, to the status of "dwarf planet."
In addition to Pluto and Ceres, the dwarf planets are Eris, Makemake, Haumea and Higia, the latter recently added to the list, as it was last month when it was discovered that this asteroid (or former asteroid, rather) met all the requirements. With only 430 kilometers in diameter, Higia is for now, the smallest of the dwarf planets.
Carlo Frabetti He is a writer and mathematician, a member of the New York Academy of Sciences. He has published more than 50 popular science works for adults, children and young people, including Damn physics, damn math or The big game. He was a screenwriter of The Cristal ball.
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