This month is the twentieth anniversary of the discovery of exoplanets, which are really just planets that are not in our solar system. (Frankly, I dislike the term exoplanet. It is so solarcentric.)
When you think about it, the discovery of planets outside our solar system (we need a word for that) is a special thing. On a graph of how expected and mundane a scientific discovery is vs. how exciting a scientific discovery is, these planets are distant outliers.
For years astronomers and cosmologists and others assumed that stars would generally have planets around them, or at least, this would often be the case. This is all part of the famous Drake Equation, best stated by Carl Sagan using the word "Billions" (with two b's) over and over again. Like this.
OK, he didn't really use "Billions" a bunch of times. But he might have.
Anyway, Nature.com has a nice set of infographics on the topic, one of which I've posted above. The rest are here.
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I think the words are "another planet,"
Jupiter is another planet, but is in our solar system.
Hate to be too pedantic and its a minor thing but actually the first exoplanets (& I agree about that word*) were found in 1991-2 around the Pulsar PSR B1257+12 (See : https://en.wikipedia.org/wiki/PSR_B1257%2B12 ) by Aleksander Wolszczan and Dale Frail.
As a sidenote, I think there were also competing claims of an earlier planet or brown dwarf around another star the orange giant Gamma Cephei or Errai A which was thought to exist in 19988 but not have a strongly proven enough case until later studies confirmed it's existence.
There is also "Latham's planet" or HD 114762 b which may be a superjovian world or a brown dwarf depending one its exact unknown orbital inclination found in 1989 around an F9 type Procyonese - but low "metalicity" subdwarf - star.
So, its complicated but basically yeah except for the pulsar planets!
Still great article though.
* The IAU definition of planet among many other severe flaws breaches the Copernican principle by stating all planets must orbit our sun which is frankly ridiculous.
SteveR, that seems right.
Here's what they say specifically:
"Twenty years ago this month, astronomers announced the discovery of 51 Pegasi b, the first confirmed planet orbiting a Sun-like star. The hellish gas giant orbits just beyond the searing heat of its parent star, and it opened astronomers’ eyes to the astonishing range of alien worlds that exist throughout the Galaxy."
So maybe they have a specific definition of "confirmed" in mind.
"The IAU definition of planet among many other severe flaws breaches the Copernican principle by stating all planets must orbit our sun which is frankly ridiculous."
Pedantic...someone has been watching too much of Sheldon Cooper on the Big Bang Therory