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My understanding is that according to the IAU definition, a "planet" must orbit the sun and not any other star. Kind of reminds me of when people thought the so

by rlanday 10y ago

My understanding is that according to the IAU definition, a "planet" must orbit the sun and not any other star. Kind of reminds me of when people thought the solar system was the center of the universe.

acqq 10y ago
The word planet comes from the ancient Greek word for "wanderer" which they used to refer to the wandering stars, the only stars that moved across the sky in relation the all other stars, only five of them visible, assigned to the gods and one goddess: Hermes, Aphrodite, Ares, Zeus and Cronus. Since then, the definition of the planet had to be modified as there are a lot of bodies orbiting the Sun known today. According to the latest precise definition, even Pluto isn't a planet anymore (but a dwarf planet). In this light, I don't see the problem in making the difference between the planets (orbiting our Sun) and the exoplanets (orbiting other stars, see my other post here). These guys however would like to remove the International Astronomical Union's definition from 2006 and to introduce the new with which even the moons(!) of the planets would be called "planets": https://arstechnica.com/science/2017/02/how-positively-peeved-pluto-people-plan-to-pluck-back-plutos-planethood/ https://arstechnica.com/science/2017/02/how-positively-peeve... As the reporter cleverly summarized, their definition could be simpler stated as, "round objects in space that are smaller than stars." Then there would be around 110 such "planets" around the Sun, and the exoplanets would also be, of course, just "planets." Their reasoning: "In the mind of the public, the word “planet” carries a significance lacking in other words used to describe planetary bodies. In the decade following the supposed “demotion” of Pluto by the International Astronomical Union (IAU) [1], many members of the public, in our experience, assume that alleged “non-planets” cease to be interesting enough to warrant scientific exploration, though the IAU did not intend this consequence [1]. To wit: a common question we receive is, “Why did you send New Horizons to Pluto if it’s not a planet anymore?” To mitigate this unfortunate perception, we propose a new definition of planet, which has historical precedence [e.g., 2,3]. In keeping with both sound scientific classification and peoples’ intuition, we propose a geophysically-based definition of “planet” that importantly emphasizes a body’s intrinsic physical properties over its extrinsic orbital properties."

by rlanday 10y ago

acqq 10y ago

The word planet comes from the ancient Greek word for "wanderer" which they used to refer to the wandering stars, the only stars that moved across the sky in relation the all other stars, only five of them visible, assigned to the gods and one goddess: Hermes, Aphrodite, Ares, Zeus and Cronus. Since then, the definition of the planet had to be modified as there are a lot of bodies orbiting the Sun known today. According to the latest precise definition, even Pluto isn't a planet anymore (but a dwarf planet). In this light, I don't see the problem in making the difference between the planets (orbiting our Sun) and the exoplanets (orbiting other stars, see my other post here). These guys however would like to remove the International Astronomical Union's definition from 2006 and to introduce the new with which even the moons(!) of the planets would be called "planets": https://arstechnica.com/science/2017/02/how-positively-peeved-pluto-people-plan-to-pluck-back-plutos-planethood/ https://arstechnica.com/science/2017/02/how-positively-peeve... As the reporter cleverly summarized, their definition could be simpler stated as, "round objects in space that are smaller than stars." Then there would be around 110 such "planets" around the Sun, and the exoplanets would also be, of course, just "planets." Their reasoning: "In the mind of the public, the word “planet” carries a significance lacking in other words used to describe planetary bodies. In the decade following the supposed “demotion” of Pluto by the International Astronomical Union (IAU) [1], many members of the public, in our experience, assume that alleged “non-planets” cease to be interesting enough to warrant scientific exploration, though the IAU did not intend this consequence [1]. To wit: a common question we receive is, “Why did you send New Horizons to Pluto if it’s not a planet anymore?” To mitigate this unfortunate perception, we propose a new definition of planet, which has historical precedence [e.g., 2,3]. In keeping with both sound scientific classification and peoples’ intuition, we propose a geophysically-based definition of “planet” that importantly emphasizes a body’s intrinsic physical properties over its extrinsic orbital properties."