1071: "Exoplanets"

[ozatm]

Okay, for all you missing Pluto, I think a little fact checking is in order. Pluto's average diameter is somewhere around 2322km (smaller than our moon). If we compare that to the smallest accepted planet, Mercury (4880km), it's not even half. If this were pictured on Randall's chart it probably wouldn't even show up unless we increased the resolution.

[AvatarIII]

This new comic 1071, being named “exoplanets.png” has broken comic 786, which was also named “exoplanets.png”.

Does anyone else find it odd that the comic displaying all 786 planets broke comic 786, "Exoplanets"?

Gee Willikers, spooky!!!

spooky or intentional an ret-conning of an old comic out of existence?

[xaq]

Anyone know why there seems to be a pretty clear maximum size? A minimum size I can understand from observational challenges. Is it that anything bigger than the red ones becomes a star?

[mfb]

We detect most planets by their diminishing of stellar light by passing in front of their stars. More info here, on the Kepler Mission page.

Most exoplanets have been discovered via the radial velocity of the star, which changes due to orbiting planets. Wikipedia has a chart showing this - it is a bit outdated, and 2011/2012 might be dominated by transits due to the kepler mission, but most planets are known from radial velocity measurements.

Observationall sciences amuse me with they'reterrible language skills.

These are the 768 known planets.

Planets are turning out to be so common that to show all the planets in our galaxy, this chart would have to be nested in itself--with each planet replaced by a copy of the chart--at least three levels deep.

So... obviously we know about more?? DOH! This's how crap like the "only using 30% of your brain" rumor gets a started.

We know that there are more planets (and estimates are somewhere in the range of many billions in the milky way). However, there are only 768 planets where the location and some basic parameters (at least the orbital period and a lower mass limit) are known.

[AvatarIII]

Anyone know why there seems to be a pretty clear maximum size? A minimum size I can understand from observational challenges. Is it that anything bigger than the red ones becomes a star?

that's my understanding, yes,

http://www.dtm.ciw.edu/boss/definition.html

Objects with true masses below the limiting mass for thermonuclear fusion of deuterium (currently calculated to be 13 Jupiter masses for objects of solar metallicity)

Substellar objects with true masses above the limiting mass for thermonuclear fusion of deuterium are "brown dwarfs", no matter how they formed nor where they are located

so as soon as it hits that magic number of approx 13 Jupiter masses, it begins fusion and becomes a star.

[Thorbard9]

I first thought this was a color-blindness test...

Dear colorblind,
There is no hidden joke. Don't even worry about it.
Love,
Me

But is there a hidden message that only the colourblind can see (easily)!?!

Edit: Nevemind, set it to black and white in paint.net, there isn't

You don't understand how colourblindness works.

But still, no special joke for me; and i'm colourblind.

[YuriPup]

At 3 levels deep that is less than half a billion planets in the Milky Way. (768^3 = 452,984,832). Seems week as a

Per Wiki the Milky Way has 200-400 billion stars (didn't that number used to be 100b? Am I getting old?).

At 4 levels deep (768^4) you get ~350 billion planets--which doesn't seem unreasonable.

[egarcia8]

This xkcd is simply wrong. First off there are many more than 786 exoplanets. Due to the Kepler mission there are several thousand. Second off, we know plenty about whats on many exoplanets. Studying the atmospheres of exoplanets is a field thats been around (with data) for atleast 10 years since the first detection of sodium in 2002 HD20945b by hubble space telescope.

[JimsMaher]

This new comic 1071, being named “exoplanets.png” has broken comic 786, which was also named “exoplanets.png”.

Does anyone else find it odd that the comic displaying all 786 planets broke comic 786, "Exoplanets"?

Gee Willikers, spooky!!!

spooky or intentional an ret-conning of an old comic out of existence?

This comic is now receiving (dubious) and (citation needed) tags, regarding the number 786.

Makes you wonder if he even sized all those circles in correspondence to actual found exoplanets, or just an approximation of the percentage of sizes.
My hypothesis of this comic's creation: Let's say he went with 10% small, 30% medium, 60% large circles ... vary the buggers up a bit for each group and viola! Instant pseudo-scientific visual representation!

"786" Dubious and citation needed.

[beav]

Where's Elmo?

[Elirra]

Makes you wonder if he even sized all those circles in correspondence to actual found exoplanets, or just an approximation of the percentage of sizes.
My hypothesis of this comic's creation: Let's say he went with 10% small, 30% medium, 60% large circles ... vary the buggers up a bit for each group and viola! Instant pseudo-scientific visual representation!

"786" Dubious and citation needed.

Ok, looking through the Extrasolar Planets Encyclopedia http://exoplanet.eu/catalog.php their current number is 778. 10 of which have been updated in the month of June. 1 of those 10 was discovered in 1999. I suspect some fudging but Randall's count is correct from a certain point of view. If its good enough for Obi Wan's ghost its good enough for me.

Now I wonder how long he's been sitting on this image just waiting to post it when the count got to 768.

[JimsMaher]

So, at the time of posting, he's over-estimating so he can point out that he already had a comic by that name whose comic number was CLOSE to the number at time of posting, so he could do this all on the solstice? Numerological BS. Approximation is one thing, when attempting to reflect reality ... and quite another when "fudging" to play off of quirky coincidences or whatever.

So very disappointed right now.

[dp2]

Observationall sciences amuse me with they'reterrible language skills.

These are the 768 known planets.

Planets are turning out to be so common that to show all the planets in our galaxy, this chart would have to be nested in itself--with each planet replaced by a copy of the chart--at least three levels deep.

So... obviously we know about more?? DOH! This's how crap like the "only using 30% of your brain" rumor gets a started.

Yup. It's also why scientists can't get their own special definition of "theory" to sink in.

When you tell people you know something scientifically even though you haven't proven it, where do you think they're going to go with that? Is it really any surprise?

[BrianB]

You know what really gets me is everytime the mainstream media reports on some new planet(s) found, they always refer to them as "new solar systems". Umm, no. Our's is the only "solar system", because it is named after our star, Sol. The correct term is more like "planetary system" or "star system" or some such.

If I were more ambitious, I'd point this fact out to these clueless reporters.

[GodShapedBullet]

I first thought this was a color-blindness test...

Dear colorblind,
There is no hidden joke. Don't even worry about it.
Love,
Me

But is there a hidden message that only the colourblind can see (easily)!?!

Edit: Nevemind, set it to black and white in paint.net, there isn't

Those are crazy hard to do well.

[Red Hal]

Observationall sciences amuse me with they'reterrible language skills.

These are the 768 known planets.

they'reterrible language skills.

the 768 known planets.

they'reterrible

768

[AvatarIII]

Aside from being awesome this xkcd cartoon looks like a colorblind test. http://xkcd.com/1071/
3:03 PM - 20 Jun 12

I'm not surprised that John Scalzi reads xkcd.

[ElWanderer]

This comic is now receiving (dubious) and (citation needed) tags, regarding the number 786.

Ok, looking through the Extrasolar Planets Encyclopedia http://exoplanet.eu/catalog.php their current number is 778.

So, at the time of posting, he's over-estimating...

778 exoplanets + 8 planets in our own star system would be 786 "known planets".

[cellocgw]

My only argument w/ the text is that at least one person (me) assumed all along that it was statistically a given that a reasonably large number of stars would sport planets. But then, I never was anthrocentric in the least.

Side note to some pedant complaining about news reports calling other planet-star collections "solar systems" : I'm sure the inhabitants of other stellar systems have a generic name for their star. The fact that we can't pronounce "i'xawob#!ph4sa" correctly doesn't change the fact that it's synonymous with "sun" in our language.

[dp2]

Side note to some pedant complaining about news reports calling other planet-star collections "solar systems" : I'm sure the inhabitants of other stellar systems have a generic name for their star. The fact that we can't pronounce "i'xawob#!ph4sa" correctly doesn't change the fact that it's synonymous with "sun" in our language.

"Solar System" has a meaning in English. The meaning is not "a group of planets orbiting a star". The word for that, again in English, is "planetary system". "Solar System", in English, is a proper noun referring to the planetary system that Earth is in. That's the point.

[okin15]

Would be really cool to see these organized by date discovered.

[Elirra]

This comic is now receiving (dubious) and (citation needed) tags, regarding the number 786.

Ok, looking through the Extrasolar Planets Encyclopedia http://exoplanet.eu/catalog.php their current number is 778.

So, at the time of posting, he's over-estimating...

778 exoplanets + 8 planets in our own star system would be 786 "known planets".

Whoops, apparently I had a touch of dyslexia thinking the number in the comic was 768.

Still, I get the feeling that this was drawn a while ago and Randall's been carefully waiting for the 786th planet to be discovered so he can drop this comic, replace xkcd/786 and begin his campaign of making everyone believe he's a wizard.

[airdrik]

You know what really gets me is everytime the mainstream media reports on some new planet(s) found, they always refer to them as "new solar systems". Umm, no. Our's is the only "solar system", because it is named after our star, Sol. The correct term is more like "planetary system" or "star system" or some such.

If I were more ambitious, I'd point this fact out to these clueless reporters.

Ironically within a couple minutes of reading this comic I came upon this (which was posted yesterday):

nooburl=http://www.dailygalaxy.com/my_weblog/2012/06/two-new-alien-planets-discovered-in-andromeda-resets-the-bar-for-weird.html Two New Alien Planets Discovered in Andromeda /url

Randall is right... this IS an exciting time right now. Oh, if only humankind had the sense to devote more of it's "planetary wealth" towards the right things...

Aside from the various uses of "solar systems" (as well as "extrasolar planets") this one struck me as extra painful:

because it orbits its host star once every 30 hours, a solar “year” on KELT-1b passes in a little more than one Earth day

So what ever are they meaning by that 'solar "year"': the time it takes that planet with its star to orbit our sun? the time at which all things that orbit that star orbit it? I suppose that the time it takes that star to wobble around the system's center of gravity kind of makes sense, but isn't really what they are referring to.
It is apparent from the couple other places they referenced that data point that they were referring to the time it takes that planet to orbit its star, however the term "solar year" just doesn't make sense (especially in that context).

[siosilvar]

Does the color have any significance (such as what we believe it's made out of, etc.) or just for effect?

It appears to be related to the size. Big ones are red, slightly smaller is brown, then that yellowish color, and the smallest ones are blue.

[Nylonathatep]

Wouldn't It be funny if the methods in which we detect exo-planets are actually flawed and the results really doesn't conform the fact that exoplanets actually exist? : i.e. The diming of distant stars at a certain interval are actually caused by accmulating space dust that drifts in the void in space/ Distant stars have regular "pulse" that causes lightwaves to dim and shine at regular interval / The results they are getting are actually the sunspots for the distant stars instead of actual planets?

You know, just like now Astromoners used to believe there are canals in Mars and actually drew maps of them when actually it's just an optical Illusion, and they think there maybe seaons on Mars because the surface colors change at a yearly cycle when it's actually the sandstorm that caused the change?

[richP]

This new comic 1071, being named “exoplanets.png” has broken comic 786, which was also named “exoplanets.png”.

Picture postcards of the old comic suddenly became extremely valuable.

/obscure?
/online substitute for picture postcard here

With this crowd, that's not a particularly obscure reference, especially considering the topic.

[Cervisiae Amatorem]

So if we can only detect a planet when it passes in front of its star, does that mean we can only detect planets that "line up" with us? Meaning there has to be a whole bunch of planets that never pass between us and their star during their orbits. I'm very uneducated in astronomy, but I don't think there's an intergalactic "up", is there? There's no reason for an orbit to in the same plane as us except by chance. Can someone straighten me out?

[Kristopher]

A better Hubble is needed.

If there are habitable planets within 20 light years, we have the tech needed to send an unmanned probe to one with a trip time of less than the lifetime of the folks who launched it.

[radtea]

Wouldn't It be funny if the methods in which we detect exo-planets are actually flawed and the results really doesn't conform the fact that exoplanets actually exist?

I see this a lot in response to empirical discoveries, presumably from people who don't really understand how Bayesian inference works. The first thing you have to realize is that we live in the Age of Precision, and this is one of the big things that distinguishes science from everything that came before it.

Scientists don't usually just notice a vague similarity between, say, the shape of a rock when viewed at a particular angle and the shape of a human face. We make the most precise and accurate quantitative predictions that we can about what--in this case--a planet passing in front of its star ought to look like using a particular instrument, and we make a detailed comparison between that prediction and the results of actual observation. The "canals" are Mars were only seen by a few people and treated with a certain amount of skepticism by most from the get-go, and this is typical of the cases where laypeople claim that scientists completely blew it.

Doing this kind of detailed work well is, to put it simply, really really hard. Most people don't have anything like the degree of obsession and meticulous attention to detail required, to the extent that they can't even appreciate that people like this even exist. So they fail to understand what an incredible thing it is that scientists are doing.

This is not to say that nature never fools us. On a few occasions there have been other, unaccounted-for phenomena that emulated the expected results in sufficient detail to fool us for a while, but it never lasts. The truth dwells in the details, and if you look at them hard enough you'll eventually find it. In the case of extra-solar planets the data are in detailed agreement in a large number of cases and there are no plausible alternatives (the ones you suggest are frankly silly because they would result in completely different data than what is observed) so we're as confident as we can be (which is always less the 100% because scientists can always update their beliefs in the face of new data) that these are planets and not sunspots or similar.

[lemmings]

I first thought this was a color-blindness test...

Dear colorblind,

There is no hidden joke. Don't even worry about it.

Love,

Me

Anyone else see the '3' in the lower left corner? It's rotated like 30 degrees counter clockwise!

[Chicagojon]

This comic makes me think of two recent things I found on the the internets:

"Better Hubbles" already exists (but it's ex-military and NASA can't afford to put it in orbit)
http://www.washingtonpost.com/national/health-science/nasa-gets-military-spy-telescopes-for-astronomy/2012/06/04/gJQAsT6UDV_story.html

We should mine mercury (literally removing it) to create an energy source to allow us to launch probes to all of the "nearby" stars. The currently known planets would be identified and explored locally in no time at all
(video presentation) http://www.youtube.com/watch?feature=player_embedded&v=zQTfuI-9jIo
(text summary) http://www.sentientdevelopments.com/2012/03/how-to-build-dyson-sphere-in-five.html

[sk8ingdom]

This new comic 1071, being named “exoplanets.png” has broken comic 786, which was also named “exoplanets.png”.

Does anyone else find it odd that the comic displaying all 786 planets broke comic 786, "Exoplanets"?

Gee Willikers, spooky!!!

I found this equally creepy and awesome. Do we have any idea if it was intentional?

This truly is an amazing time. Now if only I could hop a ride on Prometheus to visit one of these planets...

[JohnTheWysard]

So if we can only detect a planet when it passes in front of its star, does that mean we can only detect planets that "line up" with us? Meaning there has to be a whole bunch of planets that never pass between us and their star during their orbits. I'm very uneducated in astronomy, but I don't think there's an intergalactic "up", is there? There's no reason for an orbit to in the same plane as us except by chance. Can someone straighten me out?

You're quite correct! There are two main methods used to detect planets around distant stars: one uses very precise measurements of the wavelength of light given off by the star to see when the star is moving rythmically toward us and away from us, pulled by the gravity of an unseen planet in orbit around us. This works best for very big (heavy) planets close in to the star, so the star is pulled strongly.

The newer technique, using the Kepler (and now other) space telescopes, is looking for transits. This works only for the (small!) fraction of systems where the plane of the planet's orbit happens to point toward Earth. There is no preferred direction of orbits (so far as anyone knows), so it's just chance whether the plane lines up. Even in our own system, we just had a transit of Venus, and there won't be another one for over a hundred years - and we're IN the same orbital plane! So Kepler is missing a lot of what's out there.

There's also a selection bias in the transit technique - it is more likely to detect large-diameter planets (because they dim the light more), and close-in planets (because they transit more frequently). If we were looking at the Solar System from afar, even if we were in the right plane, Earth would only transit once every 365 days; Jupiter only once every twelve years! So most of the planets Kepler has found are "hot Jupiters" - large, massive planets close in to the star. It's possible that such systems are more common than systems like ours (where the big planets are much further out), but more likely it's just that this kind of system is easier to detect, and that if we had better telescopes and/or better techniques, we could find far more.

[Stormarov.45]

I just want to point out that according to the IAU, a planet, is defined as:

According to the new definition, a full-fledged planet is an object that orbits the sun and is large enough to have become round due to the force of its own gravity. In addition, a planet has to dominate the neighborhood around its orbit.
Pluto has been demoted because it does not dominate its neighborhood. Charon, its large "moon," is only about half the size of Pluto, while all the true planets are far larger than their moons.
In addition, bodies that dominate their neighborhoods, "sweep up" asteroids, comets, and other debris, clearing a path along their orbits. By contrast, Pluto's orbit is somewhat untidy.


Therefore, there are only 8 known planets

[WolfieMario]

Planets are turning out to be so common that to show all the planets in our galaxy, this chart would have to be nested in itself--with each planet replaced by a copy of the chart--at least three levels deep.

Challenge accepted.


Okay, so it's only nested 1 level, but you couldn't tell the difference anyhow.

Fun fact: There are only 748 planets in the original, not 786 - and I found that out as a side-effect of creating that many sublayers in Fireworks.

[salty]

Hey, does anyone know how the comic was created?
I suspect Randall didn't draw every dot by Hand carefully finding the right composition to form a perfect cycle.
So this must be done automatically by some algorithm?
How would you do it? Suggestions?

[hikeeba]

Waitaminute! - Where's Alderaan? How could someone leave that out? Alderaan is peaceful! They have no weapons...

[spartahawk]

Re: colorblindness test:

If you have tetrachromacy, and you turn the screen upside down, you can see a two on the left and a seven on the right.

Also, if you are not light-blind, you can see the white mushroom shape containing the text while it is still right side up

[spartahawk]

Planets are turning out to be so common that to show all the planets in our galaxy, this chart would have to be nested in itself--with each planet replaced by a copy of the chart--at least three levels deep.

Challenge accepted.


Okay, so it's only nested 1 level, but you couldn't tell the difference anyhow.

Fun fact: There are only 748 planets in the original, not 786 - and I found that out as a side-effect of creating that many sublayers in Fireworks.

Now THAT is awesome. Well done! (I don't think we could see the second level anyway, if you had done it, unless it were an enormous image.
Also, how did you approach doing that exactly??

[decaelus]

Great comic. As an exoplanet astronomer, it's exciting to see an xkcd comic about my field.

In fact, this comic was recently shared on an e-mail list of professional astronomers and planetary scientists to which I subscribe. As always occurs in such a group, there were some suggested revisions. In particular, we were worried that the line "We know nothing about what's on any of them." is a bit misleading. We actually know what many of the planets are made of, what's in their atmospheres, some things about their weather and internal structures. We WOULD like better telescopes, though.

Thanks for all your work, Randall.