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Exoplanet discovery count by year (exoplanet.eu)
34 points by cryptoz 1635 days ago | hide | past | web | 18 comments | favorite

When I saw this on HN, I rewatched the Cosmos episode ("The Backbone of the Night", aired on Nov 1980) where Carl Sagan is lecturing sixth graders in a Brooklyn school (the one he attended as a kid) on techniques to search for exoplanets and then says (from http://www.american-buddha.com/backbone.night.htm):

Well, both of these methods are being used, and by the time that you people are as old as I am, we should know for all the nearest stars whether they have planets going around them or not. We might know dozens or even hundreds of other planetary systems and see if they are like our own, or very different, or no other planets going around other stars at all. That will happen in your lifetime, and it will be the first time in the history of the world that anybody found out really if there are planets around other stars.

His stress on "even hundreds" shows that even he thought this figure was unlikely. Sagan was 47 at that time, so assuming the kids were about 12, he was hypothesizing into 35 years to the future, to 2015. He would have been pleasantly surprised at the progress so far, I think.

I wonder if any one of those kids have looked at this page and thought of that day.

The amazing thing is that he was more optimistic than most astronomers at the time with regards to extrasolar planets. It's a funny thing, prior to the mid-1990s there had only been extremely incomplete searches for exoplanets, and they all came up negative. But if you looked at the search space of those studies you see right away that they were really quite pitiful. I suppose this is one of those "effort trumps reason" situations, as a lot of effort were put into searches though they had almost no hope of finding planets. And yet those efforts led to a bias against the idea that planet formation could be common, and a bias against the scientific value of looking for planets.

At the onset of the great exoplanet discovery breakthrough in the mid '90s only a few very meagerly funded teams working were actually searching. Once they started to find planets then the astronomical community started paying attention, and funding as well as access to the best observatories in the world started pouring in.

Also, an interesting point of fact is that Sagan was actually hugely excessively optimistic. The two techniques for exoplanet discovery he describes are direct observation through occultation or deep nulling of stellar light and astrometry. As it turns out, these techniques are very, very difficult to use and we have not actually built any special-purpose spacecraft that use either method. To date only one planet has been detected through astrometry, for example. But there are methods which work rather well (doppler radial velocity and transit detection) though they were not familiar to Sagan.

From what I understand, most known exoplanets are gas giants, and almost all orbit their sun at about the distance of Mercury, because those are easier to detect. That leaves a lot of harder-to-see exoplanets we can only guess at. There are about 20 stars within a dozen light years, so I wish we could send probes to them and take a closer look. It would be a gift to our grandchildren. The risk is that in the time they would take to get there, our detection capabilities may have improved so much they'd wind up being useless, but I sort of doubt it. Being 7-12 light years closer has got to make a difference.

EDIT: Here is an amazing video showing all known exoplanets orbiting one star, so you can see their relative sizes, distances, etc.:


Here is a similar visualization in webgl, superimposed on our solar system for reference: http://www.asterank.com/exoplanets

Nearly every single exoplanet discovered is within the orbit of Mercury.

These are confirmed exoplanets, totalling 872 so far. Kepler and other missions have found probably tens of thousands more planets that are in unconfirmed status and will take years to confirm. If I may speculate, and take SpaceX and Planetary Resources to be successful 10 years out, we might be able to build absolutely astonishingly large telescopes to resolve continent-scale features on exoplanets - and have discovered and mapped millions of them in the Milky Way.

By "confirmed" do you mean we've directly observed the planets as opposed to calculating that they exist due to changes in the light from their stars? Regardless I'm very excited about increasing our understanding of these planets.. Sounds like NASA is planning to launch a telescope specifically for discovering more about planets as well[1]


I believe confirmation is usually just a process of double-checking data and waiting to see a regular cycle of wobbles or occultations. Directly observing a planet with current telescopes is difficult but it has been done:


The other possibility (besides direct imaging) that's worth calling out is retrieving spectra that will establish atmosphere content. Also very much within our lifetimes.

Nice illustration. But the x-axis scaling seems a bit wrong to me. Like there's only 8 or 9 years in each decade.

Not to be that guy, but the fact that it plots 2013 and 2014 really messes up the impact of this chart. When I first saw it, I was thinking "whoa, we must have severely cut funding for such a huge dropoff!"

It just takes an extra bit of thought, that's all; look at the 2013 value and then remember it's only April. Then think about what 2014 might look like.

Edit: Here's the graph just up to 2012: http://exoplanet.eu/diagrams/?t=h&f=&x=discovered...

2012 shows a drop down to about 150 from 200 in 2011. So there is a drop off. I think? Or perhaps the graph is just horrible, it's very hard to tell.

Does anyone know if exoplanets can find a stable orbit around binary stars? I read recently that 50-80% of stars are multi-star systems. It seems like it'd be hard for planets even to form with such a varying magnetic field.

Yes, actually, and some have recently been found. http://phys.org/news/2013-03-capture-picture-tatooine-planet...

Note that there are two ways for this to happen (orbiting one of the stars, or both) and both have been discovered.


Just eyeballing, but I don't think there's enough data to call that exponential growth. And the log plot doesn't look like it's fitting a straight line -- it's curving down a bit at the end.

By the time we achieve technology where it is feasible for our species to utilize these exoplanets we will have sufficient technology for humanity to live normal lives without planets altogether.

The future of our species is huddling around the warmth of the campfire (sun) and using raw materials from the asteroid belt to create structures orbiting the sun, until we create a sphere around the sun and all space is exhausted... then.. maybe after another few hundreds after that point, will these planets become useful. But not for reasons we would think. Perhaps for research purposes to see if humans then have the capability to tune back in to evolution after a thousand years of being pampered and letting the DNA deteriorate by eliminating survival of the fittest.

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