If the authors of an article published in the Monthly Notices of the Royal Astronomical Society turn out to be correct, George H.W. Bush’s signature “thousand points of light” slogan from 1989 was only about nine zeroes off the mark. Except it’s not stars we’re talking about — it’s exoplanets.
The solar system
Until the 17th century, the solar system consisted of six planets, the moon and the sun. In 1610, Galileo trained his telescope on Jupiter and Saturn, identifying nine new moons. Uranus and four of its moons were discovered in the 1780s, and Neptune and eight moons were found between 1846 and 1898. Pluto, along with 39 new moons were cataloged in the 20th century.
Pluto, a complex dwarf planet in the Kuiper Belt, has perhaps the most controversial categorization history in the solar system.
The rise and fall of Pluto
Lowell was an American astronomer, born in Boston, Massachusetts in 1855. After making his fortune in business, he acquired a passion for astronomy in his forties. In 1894, he built the Lowell Observatory in Flagstaff, Arizona.
By 1905, Lowell began searching for his hypothesized Planet X, which he was never located. His efforts, however, laid the groundwork for the discovery of Pluto by Clyde Tombaugh.
Percival Lowell’s mathematical calculations regarding unexplained gravitational influences on Uranus and Neptune narrowed the area of the sky Tombaugh studied. After a year of painstaking efforts, he discovered Pluto in 1930. The tiny sphere remained categorized as a planet until August 24, 2006 when the International Astronomical Union redefined it as a dwarf planet.
After 76 years of planetary status, Pluto was unceremoniously demoted, with the number of planets in the solar system decreasing to eight.
Exoplanets
The number of known exoplanets throughout the galaxy has exploded since HD 114762b was discovered in 1989.
The number of confirmed exoplanets is 4,001 as of this writing, with more cataloged almost every day. The closest is 4.25 light years from our star system, orbiting Proxima Centauri; the most distant is 27,723 light years away. The smallest exoplanet is one-third the size of Earth, with the largest 1.1 million times the size of our planet.
Rogue planets
The article Nomads of the Galaxy suggests that due to gravitational forces, collisions and other chaotic factors, there may be as many as 100,000 “nomad” planets for every star in the Milky Way; planets that do not orbit a host star but instead travel through interstellar space. Given that there are between 200 and 400 billion stars in our galaxy, the number of rogue planets could be in the quadrillions.
The existence of such exoplanets help explain a portion of the matter thought to be “missing” from the known universe. Furthermore, it is theorized that they could help propagate life throughout the cosmos. As rogue planets chaotically interact with other planets, organic material may transfer from one to the other. Such interactions would be particularly relevant within the habitable zones of host stars, where life is most likely to exist.
Dimitar D. Sasselov, Professor of Astronomy at Harvard University, said the following about rogue planets: “If you imagine the Earth as it is today becoming a nomad planet, life on Earth is not going to cease. That we know. It’s not even speculation at this point. Scientists already have identified a large number of microbes and even two types of nematodes that survive entirely on the heat that comes from inside the Earth.”
Quadrillions and quadrillions served
Once there were nine planets orbiting our sun, reduced to eight in 2006. Now there are over 4,000 known expolanets throughout the galaxy, with perhaps quadrillions more between those orbiting stars and others hurtling through the dark.
Explanets may resemble Earth, Jupiter, Uranus or Pluto, but one thing is virtually certain. Statistically, if not green men, there must be bugs, microbes or nematodes crawling around up there somewhere.
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