A new definition of a planet could help to distinguish gas giants from brown dwarfs:
Schlaufman found that objects of at least 10 Jupiter masses tend not to form around metal-rich solar-type dwarf stars:
Planets like Jupiter are formed from the bottom-up by first building-up a rocky core that is subsequently enshrouded in a massive gaseous envelope. It stands to reason that they would be found near stars heavy with elements that make rocks, as those elements provide the seed material for planet formation. Not so with brown dwarfs. Brown dwarfs and stars form from the top-down as clouds of gas collapse under their own weight.
Schlaufman's idea was to find the mass at which point objects stop caring about the composition of the star they orbit. He found that objects more massive than about 10 times the mass of Jupiter do not prefer stars with lots of elements that make rocks and therefore are unlikely to form like planets. For that reason, and while it's possible that new data could change things, he has proposed that objects in excess of 10 Jupiter mass should be considered brown dwarfs, not planets.
Abstract:
Celestial bodies with a mass of M ≈ 10 MJup have been found orbiting nearby stars. It is unknown whether these objects formed like gas-giant planets through core accretion or like stars through gravitational instability. I show that objects with M ≲ 4 MJup orbit metal-rich solar-type dwarf stars, a property associated with core accretion. Objects with M ≳ 10 MJup do not share this property. This transition is coincident with a minimum in the occurrence rate of such objects, suggesting that the maximum mass of a celestial body formed through core accretion like a planet is less than 10 MJup. Consequently, objects with M ≳ 10 MJup orbiting solar-type dwarf stars likely formed through gravitational instability and should not be thought of as planets. Theoretical models of giant planet formation in scaled minimum-mass solar nebula Shakura–Sunyaev disks with standard parameters tuned to produce giant planets predict a maximum mass nearly an order of magnitude larger. To prevent newly formed giant planets from growing larger than 10 MJup, protoplanetary disks must therefore be significantly less viscous or of lower mass than typically assumed during the runaway gas accretion stage of giant planet formation. Either effect would act to slow the Type I/II migration of planetary embryos/giant planets and promote their survival. These inferences are insensitive to the host star mass, planet formation location, or characteristic disk dissipation time.
[Ed. note: I long ago stumbled upon an image showing the relative sizes of the planets against the size of the sun... and now can no longer find it, or anything like the one I remembered. Does anyone have a good link to recommend? --martyb]
(Score: 5, Informative) by bradley13 on Thursday January 25 2018, @01:11PM (2 children)
Personally, I am very fond of the illustration used in Wikpedia, which shows not only how tiny our planets are compared to the Sun, but how tiny the Sun is amongst stars [wikipedia.org].
If you just want the solar system, there are lots - dunno which one struck your fancy. Here's one from Wikipedia that seems quite good [wikipedia.org].
Everyone is somebody else's weirdo.
(Score: 4, Insightful) by takyon on Thursday January 25 2018, @01:17PM
I've been on that page before. It's pretty jaw-dropping to see the Sun and Sirius compared to Aldebaran, and then Aldebaran compared to Antares/Betelgeuse.
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]
(Score: 2, Interesting) by Anonymous Coward on Thursday January 25 2018, @02:17PM
My favorite is a gif I saw 10+ years ago, though it seems to be slightly out of date (it says the largest known star is VY Canis Majoris, which according to the Wikipedia page is no longer true).
You can see it here. [educationalgifs.com]