Comment by Aachen
21 hours ago
Exoplanets also aren't planets. Some things just seem to have definitions with a history that get applied to new discoveries that don't fall within the definition. Distinguishing random rocks in space from planets was done by requiring planets to orbit around the sun, and so planets elsewhere cannot be called planets no matter that it's 1:1 the same thing. Biology probably has a similar history of trying to draw a line somewhere between what was created and what evolved to be part of the 'natural' world
Exoplanets are planets. Also, for clarification, biology is not defined as “the study of things produced exclusively by natural evolution.” Synthetic biology works with biological components and living systems (DNA, proteins, regulatory networks, cells and organisms). It differs from much traditional biology mainly in its constructive, engineering-oriented approach. Synthetic systems are often built precisely to test hypotheses about how natural biological systems function. Claiming it is not biology is wrong IMO.
For anyone else that might be curios, the definition of a planet you will often see quoted online applies to bodies in our Solar System. It comes from the International Astronomical Union in 2006. This is the famous definition that dropped Pluto as a planet. While the criteria are widely quoted, that actual resolution isn't. The resolution:
The IAU...resolves that planets and other bodies, except satellites, in the Solar System be defined into three distinct categories in the following way:
(1) A planet [1] is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.
(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape [2], (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
(3) All other objects [3], except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".
The definition here only applies to bodies in the Solar System.
Still a bad definition IMO. According to the definition if a catastrophic event were to occur that cluttered the neighborhood of a planet it would cease to be a planet until it was cleaned up. The definition of a planet should be based in the physical attributes of the celestial body itself, not in its role or relationship with other bodies. I'm a bit of an extremist on this front. Even our Moon would be a planet in my opinion. Seems silly when you think about our barren moon but there are for sure habitable moons out there. I can't imagine asking an alien "What planet are you from?" and them responding "erm, actually we are from a moon/planetary satellite".
> Captain's Log, Stardate 1513.1. Our position, orbiting planet M-113. On board the Enterprise, Mr. Spock, temporarily in command.
<<insert nerd screeching about the word planet>>
Eh, that doesn't make sense.
What's a meteor?
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Right? It's biology when you study enzymes in vitro, but as soon as you put a membrane around them then it's ... something else?
Bizarre argument.
> Exoplanets also aren't planets.
That is flatly wrong.
https://en.wikipedia.org/wiki/Exoplanet
"An exoplanet or extrasolar planet is a planet outside the Solar System."
The GP post's point was that, logical as this would be, the IAU definition explicitly states that planets are "in the Solar System". So no, exoplanets are exoplanets, not planets. And Pluto isn't an example of either.
No, The IAU definition does not say that. You and others are confusing the definition of a planet with its application to planets in the solar system (and thus to Pluto) -- IAU Resolution 5A: Definition of a Planet in the Solar System.
The IAU of course does not assert that only planets in the solar system are planets ... that would be ridiculous, and the interpretation of the IAU's stance as being so ridiculous is ridiculous and then some.
https://science.nasa.gov/solar-system/planets/what-is-a-plan...
"The definition of a planet adopted by the IAU says a planet must do three things:
It must orbit a star (in our cosmic neighborhood, the Sun).
It must be big enough to have enough gravity to force it into a spherical shape.
It must be big enough that its gravity has cleared away any other objects of a similar size near its orbit around the Sun."
https://www.iau.org/IAU/Science/What-we-do/Pluto-and-the-Dev...
"More generally, a planet:
a. orbits its host star, just as the Earth and Jupiter orbit the Sun,
b. is large enough to be mostly round, and
c. must have an important influence on the orbital stability of the other objects in its neighbourhood."
> Exoplanets also aren't planets.
Imagine writing this.
What they meant when they said "planets" was the 8 (previously 9, previously to that 8, previously 7...) known and named planets in our own solar system. A hypothetical "Journal of Planets" that was actually about solar system astronomy wouldn't necessarily have known what to do with a new paper about 51 Pegasi b published 30 years ago. They're thinking "when we said planets, we actually always meant solar system planets, it just never came up until now".
The reviewer of this paper is saying that by biology they always meant naturally evolved cellular biology, not synthetic biology - there's just never been an example of the latter before.
I think the take is wrong, the receiving journals should be excited to expand their scope rather than frustratedly redefine their scope more narrowly, but definitions and categorization are hard.
> What they meant when they said "planets"
Who is "they", and how do you know what they meant?
The relevant fact is that the claim "Exoplanets also aren't planets" is simply wrong -- exoplanets are by definition planets outside the solar system. It's like claiming that a brown furple isn't a furple -- the claim is wrong, regardless of what one thinks a furple is.
> The reviewer of this paper is saying that by biology they always meant naturally evolved cellular biology, not synthetic biology - there's just never been an example of the latter before.
They aren't saying that, and that isn't true.
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The argument you describe is as if Neil deGrasse Tyson took a course about “How to be even more extremely and inappropriately pedantic,” and decided he wanted to become the undisputed world expert at that.
Anyone who says “exoplanets aren’t planets” really needs to think a little harder about the actual meaning of what they’re saying.
Actually, that is the IAU stance. And their definition for exoplanet includes small, non-rounded objects orbiting stars which would be asteroids (or comets or whatever) if they happened to be around the Sun.
All that debacle around dwarf planets to prepare for future observations, and yet the distinction ceases to apply the moment you go outside the Oort cloud...
But really, that's just the naming systems being bad, obviously common people don't think asteroids around other stars are "exoplanets" or should be called that way
I'm not talking about edge cases like asteroids or planetoids or dwarf planets. I'm talking about actual planets. Like a gas giant orbiting a star. It's obviously a planet even if it's not orbiting Sol.
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This is quite wrong.
https://www.iau.org/IAU/Science/What-we-do/Pluto-and-the-Dev...
"More generally, a planet:
a. orbits its host star, just as the Earth and Jupiter orbit the Sun,
b. is large enough to be mostly round, and
c. must have an important influence on the orbital stability of the other objects in its neighbourhood."
Exoplanets are planets by that definition where the host star is not our Sun:
"Researchers have found hundreds of extrasolar planets, or exoplanets, that reside outside our solar system. "