back to article Mass limit proposed so boffins can tell when they've fingered a brown dwarf or a fat planet

The official definition of a planet should be updated to include an upper mass limit, so scientists can agree on whether a large newly found celestial body is either a huge planet – or a tiny failed star. That's according to Kevin Schlaufman, an assistant professor of astrophysics at Johns Hopkins University in Maryland, US. …

  1. Anonymous Coward
    Anonymous Coward

    I had a few scoops and a curry last night and even I'm unsure if it was a brown dwarf, it felt like a planet to be fair.

    1. I ain't Spartacus Gold badge
      Flame

      Surely a planet. It was in close proximity to uranus...

  2. Dodgy Geezer Silver badge

    Surely..p

    ..a brown dwarf is a racist, sizeist designation?

    Demonstration at the IAU IMMMEDIATELY!!

    1. Michael Habel Silver badge

      Re: Surely..p

      What do you expect from a bunch of elderly overprivleged white cis-genderd men?

    2. Alistair Silver badge
      Windows

      Re: Surely..p

      I'm thinking the gnomes may have something to say about this.

  3. missingegg

    Makes me cringe

    That artist's conception is just terrible. The diameter of the Sun is roughly 1% of the distance from the Sun to Earth. If the actual scale of the solar system even vaguely resembled the picture, the Sun would fill most of the day time sky.

  4. jmch Silver badge

    Arbitrary?

    Seems like a fairly arbitrary cutoff, even the proposers themselves say that it's probabe rather than definite that anything above 10XJupiter is a brown dwarf. Why insist on a definite classification of objects about which we don't have enough information for classification?

    1. Pascal Monett Silver badge

      Re: Arbitrary?

      Because until such time as we have a complete definition, we still have to classify the discovery.

      It wouldn't do to throw everything in the "Undefined" folder, and we can't reasonably put it in "Supermassive" either (or "Sun-like", etc). So we have a category that requires refining, but we still need the category.

      1. jmch Silver badge

        Re: Arbitrary?

        "until such time as we have a complete definition, we still have to classify the discovery"

        Do we HAVE to? It sounds like the type of thinking Feynman was railing against - that just beause you can give something a name you know anything about it

        "It wouldn't do to throw everything in the "Undefined" folder"

        No, but if the mass is the only reason to think it could be a brown dwarf, how about "Probable Brown Dwarf". Otherwise there is the big risk of mischaracterising a number of celestial bodies, and once a label is given it's difficult to shake off (see - Pluto: planet)

  5. alain williams Silver badge

    "about ten times that of Jupiter – or ten times 1.898×10^27kg"

    If it is "about" then why give a number to 4 places of decimal ? "ten times 2×10^27kg" would have been accurate enough - especially considering how the whole tone of the article was about the difficulties of being precise. Did Ms Quach understand what she was writing about ?

    1. Swarthy Silver badge
      Headmaster

      Re: "about ten times that of Jupiter – or ten times 1.898×10^27kg"

      But 1.898×10^27 isn't to four decimal places, rather it's followed by 24 digits before the decimal.

      24 digits leaves quite a bit of room for "about" and "approximate", wouldn't you say?

      1. Not also known as SC Silver badge
        Coat

        Re: "about ten times that of Jupiter – or ten times 1.898×10^27kg"

        Alain obviously meant 2 significant figures instead of decimal places, and Alain is right, anything much more precise is meaningless. It is like giving the distance from London to New York to the nearest 10 whole miles (3470) which is sensible or to the nearest inch / cm which is so precise it becomes meaningless.

  6. Destroy All Monsters Silver badge
    Paris Hilton

    Trigger arning!

    Similar to "chain migration", "master-slave wiring" and "Tom Cotton", I find "brown dwarf" and "fat planet" offensive to our diverse co-inhabitants. I won't literally even go into "black hole". I expect a name insulting to alternate sexuelative persons will occur soon.

    Can't something be done?

    1. Pascal Monett Silver badge

      Re: Can't something be done?

      Yes : educating people that Science has no social or sexual connotations and none should be inferred. A black hole is a hole in space/time that is black because no light can be emitted from it. End of.

      That education will likely take until the heat death of the Universe, though.

    2. Anonymous Coward
      Anonymous Coward

      Re: Trigger arning!

      I always worry when their is an aeroplane accident and they start searching for the black box.

      1. I ain't Spartacus Gold badge

        Re: Trigger arning!

        Especially as the black box is orange.

        It must be terribly confused.

        1. Anonymous Coward
          Anonymous Coward

          Re: Trigger arning!

          "Especially as the black box is orange."

          The airplane crashed. Sad!

  7. steelpillow Silver badge
    Mushroom

    Firing up

    Unh. So if a star blows off its outer layers and the remnant is smaller than ten Jupiters, then it becomes a planet?

    Seems to me that the critical distinction should be whether the core is, or has ever been, capable of starting nuclear reactions, i.e. of actually creating more heat than its collapse did. Stars can shine, planets only cool. Simple.

    1. cray74 Silver badge

      Re: Firing up

      Seems to me that the critical distinction should be whether the core is, or has ever been, capable of starting nuclear reactions,

      Agreed, but that's harder to verify for borderline cases. Mass is relatively easy, especially if an exoplanet/brown dwarf was spotted by the Doppler effect.

    2. Rich 11 Silver badge

      Re: Firing up

      Unh. So if a star blows off its outer layers and the remnant is smaller than ten Jupiters, then it becomes a planet?

      No. You're confusing smaller with less massive.

      All known white dwarfs have a mass of between 0.5 and 1.44 solar masses, yet their radius is no more than that of the Earth. The Chandrasekhar Limit of 1.44 solar masses is accepted as the theoretical maximum mass for a standard electron-degeneracy white dwarf and is supported by observation, while the existence of helium white dwarfs of below 0.5 solar masses is hypothesised but not yet supported by observation (possibly because the hypothesis also suggests that it would take longer than the current age of the universe for a candidate star to reach this stage of its life).

      Stars can shine, planets only cool. Simple.

      No, it's really not that simple. White dwarfs do only cool (unless they acquire sufficiently more mass from somewhere, anyway). They are not producing heat by fusion; they are extremely hot stellar cores radiating inherent heat and will take tens of billions of years to reach background temperature. Rocky planets, on the other hand, are still capable of generating heat and radiating it away, although by nuclear fission rather than fusion (and don't get me started on gas giants).

    3. Rattus Rattus

      Re: Firing up

      Stars can shine

      People can try

      But that's about it

      (Apologies to Dan Salvato)

  8. IHateWearingATie

    Units of Measure!!

    Kilograms?

    What happening to the accepted measure of mass on El Reg, the KiloJub

    I demand an apology. And the article to be amended to a mass unit we can all appreciate.

  9. Ugotta B. Kiddingme

    tangentially relevant question

    If a brown dwarf were to somehow acquire more mass in the form of hydrogen or other fusionable* material, would it ignite and thereby drop "failed" from its "star" status?**

    * yes, I know that's probably not the correct word but I don't think fusile or fusible are correct because they can mean blending materials together by simple melting

    ** not trying to be a smartass. Trying to ask a legitimate question to expand my knowledge.

  10. Anonymous Coward
    Anonymous Coward

    Irony

    The lifeforms on a planet circling a brown dwarf, in orbit around a nearby star turn out to be... 2.8 feet high, have dark grey skin, huge eyes and biomimetic abilities. Saw this on a documentary a while back.

    The politically correct term is "SkyriwiiuhIans" or whatever that translates to in English.

    Damn universal translator!

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