The 500th planet! reports that a milestone has been reached in the discovery of planets orbiting other stars.

The 500th alien world appears to have been discovered, according to extrasolar planet trackers.

Less than 20 years after confirming the first planet beyond our own solar system, astronomers have bagged exoplanet No. 500. The milestone was reached Friday (Nov. 19), according to the Extrasolar Planets Encyclopedia, a database compiled by astrobiologist Jean Schneider of the Paris-Meudon Observatory.

As of today (Nov. 22), the count stands at 502 alien worlds, the database reports.

The 500th extrasolar planet was reported in the midst of the discovery of several others. And there’s always the risk a previous discovery turns out to be a false alarm, dropping the count.

For such reasons, it makes little sense to permanently anoint one particular world as “exoplanet 500,” Schneider told

That being said, the 500th alien planet currently appears to be one of four newfound extrasolar worlds, based on Schneider’s list. They appear on the list just after another extrasolar planet, HIP 13044 b, which astronomers announced last week to be from an alien galaxy.

All of the newfound planets are less massive than Jupiter (they range between 15 and 50 percent of Jupiter’s mass), and the planets’ distances from Earth range from 58 light-years to 196 light-years.

The find comes less than two months after another watershed moment — the discovery of the first potentially habitable extrasolar planet. And astronomers are sure to hit other big milestones soon, as data rolls in from instruments like NASA’s planet-hunting Kepler space observatory.

“In some sense, 500 is an artificial milestone,” said Jon Jenkins of the SETI (Search for Extraterrestrial Intelligence) Institute. Jenkins is the analysis lead for the Kepler mission.

“It’s much more fun to watch the nature of the discoveries change over time,” Jenkins told “The variety of planets we’ve discovered has also increased.”

Astronomers aren’t just discovering scorching-hot gas giants anymore, he added. They are finding smaller, rocky worlds, too — planets that could be a lot like Earth.

There’s more at the link.

Dang, these astronomers are making progress! I can remember when they announced they’d found the very first extra-solar-system planet, back in 1988. That was disputed for a long time until it was confirmed, but another discovery in 1992 put the existence of extrasolar planets beyond doubt. Now they’ve counted over 500 of them! I guess I won’t live to see any of them, but who knows? Two or three generations from now, children may be growing up with the option of taking a one-way ride out of our solar system into the great unknown, to colonize a planet from which they’ll never return.

How I’d love to have that opportunity! What an adventure!



  1. Sorry Peter, but unless man can figure out a way to duplicate earth level gravity, that can be sustained throughout interstellar flight, that's not going to happen, and I don't even know any physicists who even have a clue for a theory as to how such a thing could be accomplished.

    It's one of the little known, but open secrets of the space exploration world. Send probes? Sure. Homo sapiens? Not so much.

  2. Sustained one G thrust? The problem isn't creating it, it's sustaining it(fuel). Let's not get into maximum duration of that thrust before hitting a maximum speed(where the engines fail to give thrust due to relativistic, or just particle speed reasons, the idea of a "ram scoop" fusion drive for example had, IIRC a maximum speed of 0.8C) and various other problematic bits and bobs(like micrometeorite protection at those speeds).

    I am sure solutions will eventually be found, even if it's out of left field(like a way to circumvent the degradation the human body experiences in zero gravity so we can coast the distance). However my bet is on engines/fuel solutions, and either thrust/break cycles or simply a distance limit on the single thrust/break cycle.

  3. Moshe: Spin the craft. Problem: solved.

    Peter: Wow, I had no idea. I too recall the discovery of the first one, and how amazed everyone was, that we finally had proof that planets weren't simply a local phenomenon, but I didn't realise that we were up to 500 of them.

    And it makes sense that we'd find the big ones first, of course. As our technique and tools get better, the little ones more to our spec will become easier to see.

    The Japanese probe that went to the asteroid belt was a good start. Now we need to make one that's basically a Von Neumann machine, to go out there, start mining the asteroid, and building more of itself, and then start building (at least the hull) of our interstellar craft. 🙂

  4. And if you spin the craft for earth-equivalent gravity, 1 gee thrust isn't needed (or even desirable at that point). But you run into sociological issues after a few generations: after living in an artificially controlled, predictable environment, how many are even going to want to settle on a (dirty, icky) planet?


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