Caltech Researchers Find Evidence of a Planet Beyond Pluto • Hacker News Board

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#61

Post by sandworm101 » Wed, Jan 20, 2016, 7:04 PM UTC

slg wrote: post #50

sandworm101 wrote: post #21

Giant, weird orbit, debate ... there can be only one name. This is Planet X. Also because X would be 10th discovered planet, a reference that pluto, while not a planet today, was indeed the ninth _discovered_ planet.

If you are going by that logic, Pluto was at least the 10th planet discovered and this is at least the 11th. Ceres was discovered before either Neptune or Pluto and spent 50 years as a "planet". It eventually went through a similar reclassification process as Pluto as other similar objects were discovered. The only reason you don't see the same controversy around its classification is because it was recategorized a c…

If naming was all about logic then 1/2 the places on earth would need to be renamed. Naming is about emotion, style, history, and personal preference. Even total mistakes (the Giant Squid) are grandfathered through. Galileo named the moons of Jupiter after his sponsors. I just hope this thing doesn't become "X, brought to you by iPhone8".

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#62

Post by [deleted] » Wed, Jan 20, 2016, 7:06 PM UTC

lhorie wrote: post #33

mturmon wrote: post #7

Provocative title for this Caltech press release. Mike Brown, the co-author of the paper reported here, discovered Eris, a KBO like Pluto, in 2005. This discovery prompted the IAU in 2006 to demote Pluto out of the realm of "planet" into a "dwarf planet". At the time, Alan Stern's New Horizons mission to Pluto had just been launched, it finally arrived last year. Stern was incensed that NH started out as a visitor to…

Small nitpick: "largest" refers to mean radius, "massive" refers to mass (aka weight). Pluto is the second most massive, but it is the largest. (To be fair, it is a very close call: its diameter is only ~25km larger than Eris) I'm excited to see this story unfold, if nothing else because it's fun looking up the mythological[1][2][3] origins of the names given to new celestial bodies :) [1]( https://en.wikipedia.org/w…

[deleted]

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#63

Post by ahmedfromtunis » Wed, Jan 20, 2016, 7:07 PM UTC

overcast wrote: post #40

lhorie wrote: post #33

Earlier quoted context omitted.

Small nitpick: "largest" refers to mean radius, "massive" refers to mass (aka weight). Pluto is the second most massive, but it is the largest. (To be fair, it is a very close call: its diameter is only ~25km larger than Eris) I'm excited to see this story unfold, if nothing else because it's fun looking up the mythological[1][2][3] origins of the names given to new celestial bodies :) [1]( https://en.wikipedia.org/w…

Mass isn't weight, it's the amount of matter. Weight is the measure of the pull of gravity on mass.

You're right, but sorry, it does NOT matter: https://youtu.be/QSIuTxnBuJk

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#64

Post by gohrt » Wed, Jan 20, 2016, 7:09 PM UTC

antognini wrote: post #47

qb45 wrote: post #43

Earlier quoted context omitted.

Are you sure it's r^4 , not 4r^2 ?

Yes. The solid angle subtended by the planet (and hence the amount of reflected light) goes as 1/r^2, and then the apparent brightness of the reflected light to us goes as an additional 1/r^2. The total dependence is then 1/r^2 * 1/r^2 = 1/r^4.

This is a really good physics puzzler.

The key point is that Pluto does not reflect light like a mirror, it scatters light relatively uniformly, causing more light loss to an observer than, say, a mirror that points the reflection directly at an Earth observer.

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#65

Post by jcrites » Wed, Jan 20, 2016, 7:09 PM UTC

qb45 wrote: post #43

antognini wrote: post #9

Earlier quoted context omitted.

They do, and at the end of the press release it says that Brown has begun an observing campaign to find the planet. Unfortunately detecting these very distant objects is very difficult. The light we see from them is reflected light from the Sun, so their apparent brightness goes as 1/r^4, not 1/r^2 like most objects. And because they are so close, there is a strong parallax from the motion of the Earth. THe consequen…

Are you sure it's r^4 , not 4r^2 ?

The light reaching the object from the sun drops off by 1/r^2, and then the light reaching Earth from the object drops again by 1/r^2. Since the latter light is a portion of the former, you multiply them for 1/r^4.

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#66

Post by mast » Wed, Jan 20, 2016, 7:10 PM UTC

Very cool.

It reminds me about a book I read called "In Search of Planet Vulcan" (http://www.amazon.com/In-Search-Planet-Vulcan-Clockwork/dp/0...). Before Einstein, astronomers tried to explain the motion of Mercury by suggesting there might be another planet inside Mercury's orbit.

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#67

Post by ilyagr » Wed, Jan 20, 2016, 7:12 PM UTC

There is an awesome summary by Emili Lakdawala at the Planetary Society (as is often the case with such news).

http://www.planetary.org/blogs/emily-lakdawalla/2016/0120095...

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#68

Post by mud_dauber » Wed, Jan 20, 2016, 7:13 PM UTC

LV-426. Just sayin'.

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#69

Post by asavadatti » Wed, Jan 20, 2016, 7:19 PM UTC

sandworm101 wrote: post #61

slg wrote: post #50

Earlier quoted context omitted.

If you are going by that logic, Pluto was at least the 10th planet discovered and this is at least the 11th. Ceres was discovered before either Neptune or Pluto and spent 50 years as a "planet". It eventually went through a similar reclassification process as Pluto as other similar objects were discovered. The only reason you don't see the same controversy around its classification is because it was recategorized a c…

If naming was all about logic then 1/2 the places on earth would need to be renamed. Naming is about emotion, style, history, and personal preference. Even total mistakes (the Giant Squid) are grandfathered through. Galileo named the moons of Jupiter after his sponsors. I just hope this thing doesn't become "X, brought to you by iPhone8".

I think you are confusing naming and classification.

Re: Caltech Researchers Find Evidence of a Planet Beyond Pluto

#70

Post by School-Cotton » Wed, Jan 20, 2016, 7:32 PM UTC

logicallee wrote: post #54

tdaltonc wrote: post #25

> Batygin and Brown inferred its presence from the peculiar clustering of six previously known objects that orbit beyond Neptune. This raised a big red flag in my mind. This must produce a literally astronomical multiple comparisons problem. Yes they reported sigma = 3.8, but if they didn't do their multiple comparisons correction right (which I am in no position to determine), they're basically reading tea leaves. I…

So I might not have a great enough understanding but isn't 3.8 sigma not high for this kind of announcement (with the current title)? if someone wants to report finding a planet in the solar system ten times the size of Earth wouldn't they do so at more than @3.8 sigma. In particular, the prior is quite low because it would affect a bunch of other astronomical calculations, wouldn't it? So you would want the confiden…

I wish people wouldn't downvote you without explaining why you're wrong.

I have zero education in statistics and your comment makes intuitive sense to me so I'd like to learn more.