A John Hopkins University astrophysicist, Kevin Schlaufman, has issued a proposal to his fellow scientists. He considers that they need to come up with a new meaning for the word “planet.”
Writing in The Astrophysical Journal, Schlaufman suggests that a space object should be given the term “planet” based on its surroundings. These could give a good indication of how the object was formed.
“Under a formation-based definition, planets are celestial bodies that form through core accretion. Conversely, brown dwarfs and stars form through direct gravitational collapse, either at the disk or core scale,” he said.
What Does the Term Planet Mean Now
The term planet is currently defined by rules made in August 2006. These say that one, this orbits the Sun and second, it has enough self-gravity to be nearly round. The third and final rule states that a planet has cleared its orbit of other bodies. Pluto got ousted because of this latter since its orbit crosses over with that of Neptune.
The problem is that we have discovered numerous exoplanets, ones which do not orbit our Sun, and which only have a working definition. This matter is especially muddied because of brown dwarfs. These are space objects which are somewhere between large, Jupiter-sized planets, and small stars.
According to the proposed exoplanet definition, brown dwarfs are considered neither planets nor stars. They are defined by the fact that they achieve deuterium fusion. Schlaufman says that this varies based on an object’s composition and internal properties, so a new meaning is needed.
He also notes that looking at the star area that an object orbits is a good clue about its origin. Brown dwarfs, which are made from gas and dust, can wind up around different kinds of suns.
In contrast, gas giants like Jupiter nearly always orbit iron-rich stars, because these have heavier elements in their accretion discs. These allow them to build one up from the core.
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