Astronomers Discover New Planet Out Beyond Neptune (Jun, 1930)

Astronomers Discover New Planet Out Beyond Neptune

The recently discovered planet, already named Pluto, is judged to be the same size as the earth.

The late Percival Lowell, shown above, predicted the planet’s discovery 25 years ago. The picture of the planet was obtained with a 24-inch reflector and is from a 30-times enlargement of the plate. It was taken by Prof. George Van Biesbroeck of Yerkes Observatory at Williams Bay, Wisc. The bright glow on the plate is the near-by star, Delta Geminorum.

  1. rick says: February 4, 20101:17 pm

    If you visit the Lowell Observatory in Flagstaff, AZ, you can see and try out the actual blink comparator Tombaugh used to pick out the planet from the thousands of stellar images on the photographic plates. A simple but clever device. Not sure who actually invented it.


  2. Don says: February 4, 20101:29 pm

    New Planet . . . or *is* it??

  3. TomB says: February 4, 20102:03 pm

    I hope it is NOT the same size as the Earth, or we lose our planet too.

  4. Firebrand38 says: February 4, 20102:07 pm

    TomB: Don’t get too anxious…you do realize this story was in 1930?

  5. John Savard says: February 4, 20102:47 pm

    Pluto is much smaller than the Earth. We only learned this for certain, though, after its moon, Charon, was discovered, which enabled us to accurately measure Pluto’s gravity and therefore mass.

  6. Don says: February 4, 20103:05 pm


  7. Firebrand38 says: February 4, 20103:13 pm

    Don: Now I know you’ve seen more than your share of posts on this blog about folks getting outraged over something from fifty or seventy years ago.

  8. Mike says: February 4, 20103:14 pm

    I like the “new planet” and arrow pointing to the white spot in the drawing.

  9. Rick Auricchio says: February 4, 20105:04 pm

    They can take away Pluto’s status as a planet. But not his status as a dog.

  10. Firebrand38 says: February 4, 20105:21 pm

    Rick Auricchio: Well said. Which begs the eternal question if Pluto is a dog what is Goofy supposed to be?

  11. KD5ZS says: February 4, 20108:30 pm

    Goofy is a dog too; one that can talk.

  12. Richard @ The Bewildered Brit says: February 4, 201011:01 pm

    Fascinating! Does anyone know why they got the size so far out?

  13. Nomen Nescio says: February 4, 201011:06 pm

    they only got it wrong by about one order of magnitude (in radius; two, in surface area). by the standards of astronomy that’s pretty dead on, actually — especially for an early estimate made in the 1930’s. there are measurements in astronomy even today with much bigger error bars than that.

  14. StanFlouride says: February 4, 201011:12 pm

    Then, now, and FOREVER!…

    I always think of this exchange from “SOAP” when Billy Crystal’s character Jodie
    came out of the closet to his mom:

    Jodie Dallas:(listing famous people who were gay) …Plato was gay.
    Jessica Tate:(pause) Wait… Mickey Mouse’s dog was gay?
    Jodie Dallas: Yeah, that’s right mom. And Goofy was his lover.

  15. StanFlouride says: February 4, 201011:23 pm

    Sharpest ever images of Pluto show mottled world

    Pluto may take 248 years to orbit the sun, but its surface is changing at a much faster rate, new images reveal.


  16. Firebrand38 says: February 5, 201012:11 am

    StanFlouride: Global warming on Pluto. Who woulda guessed? 😀

  17. George says: February 5, 201010:58 am

    When I was your age, Pluto was a planet.

  18. jayessell says: February 5, 20102:12 pm

    a) Why is it an illustration of our Solar System as viewed from it’s south pole?
    Is it to represent how it would appear as seen from Alpha Centari?
    Maybe I should be asking why every other illustration is north of the plane of the orbits?

    2) KD5ZS…
    Yes. Goofy is an antropomorphic dog, As Mickey is a 3 foot tall antropomorphic mouse.

  19. rick says: February 5, 20103:35 pm

    Pictures of planets or moons as shown in astronomy texts or articles are always with the south pole up because that’s the way they appear in telescopes. The image is always reversed. That said, I don’t see any indication in the drawing of the solar system that the south pole is up. In fact, by looking at the directions of the planets shown and their rotation directions, the north pole seems to be up.


  20. Richard @ The Bewildered Brit says: February 5, 20103:42 pm

    @ Nomen Nescio. Excellent, thanks for the info! I love astronomy but I know next to nothing about it! 🙂

  21. KD5ZS says: February 5, 20104:36 pm

    Jayessell– I think you mean anthropomorphic

    Mickey, Minnie, Donald, et all just live across town from me (Disneyland is about 8 miles from my house.) Knott’s Berry Farm is also quite close.

  22. Charlene says: February 8, 20106:04 pm

    If Pluto the dog is Pluto the planet, then Goofy the dog is probably Earth.

  23. Jari says: February 9, 20101:21 pm

    Charlene: Hope not. Otherwice Earth suddenly trips over its own feet, get entangled to the scenery/props and says “Hyuck hyuck!” 🙂

  24. Toronto says: February 9, 20105:56 pm

    Jari: we seem to be doing that now.

  25. hwertz says: February 17, 201012:02 am

    Why was the initial size so far off? Charon I think. It is almost half the size of Pluto, and was only discovered in the 1970s. Even then Charon just looked like a bulge — it took the newest telescopes, Hubble and earth-based scopes with adaptive optics, to actually see Pluto and Charon as 2 seperate objects. So pre-1970s it would have been natural to assume Pluto is much larger than it is.

    As for Plutos status as a planet — it was somewhat controversial. Who’d have thought that astronomers were all political, but they are. It seems at the IAU meeting where they voted to demote Pluto, there was still a lot of disagreement.. and some have thought the vote may have been “rigged”. There’s 10,000 IAU members, 2700 showed up for the 10 day IAU conference. But the vote was late the last day, after many had already left, and only 424 members actually participated in the vote.

  26. Rahul says: March 11, 20104:46 am

    I think it’s not a new discovery at all .
    there is no planet as it is mentioned above .
    It was just the mistake of the observer

  27. Our Solar System says: June 14, 20104:14 pm

    Poor old Pluto wasn’t a planet for very long

  28. Laurel Kornfeld says: August 9, 20102:16 pm

    Pluto’s small size does not preclude it from being a planet, as it is large enough to be rounded by its own gravity, a state known as hydrostatic equilibrium. Kudos to hwertz for recognizing the political nature of the IAU decision, which remains just one opinion in an ongoing debate. It was opposed in a formal petition by hundreds of professional astronomers led by New Horizons Principal Investigator Dr. Alan Stern. Notably, the New Horizons mission continues to refer to Pluto as a planet.

  29. Mike Burdoo says: September 12, 201012:05 pm

    If you have an interest in how it was discovered, read Percival’s Planet by Michael Byers. Historical fiction – but great fun!

  30. rick s. says: September 12, 201012:52 pm

    Thank you Mike Burdoo. I just ordered the book from the library and look forward to reading it. Thanks again for the heads up!


  31. Solar System says: December 9, 20102:02 am

    Clyde Tombaugh’s ashes are whizzing their way towards Pluto as we speak, on board NASA’s New Horizons craft.

  32. Phil says: September 21, 20116:42 pm

    Pluto is just as much of a planet as Europe is a continent. Nobody’s ever talked about demoting Europe to the status of a blob on Asia because Europe’s always been considered a separate continent in terms of culture and history.

    Personally I like Issac Asimov’s suggestion in 1980 (shortly after Charon was discovered). Since Pluto was so much larger than any (known) minor planet at the time, and so much smaller than the major planets it should be put into its own category – a mesoplanet (from “meso” the Greek word for middle). Any future objects could join Pluto in that class. This suggestion was made about two decades before such objects were discovered in the outer asteroid belt, Kuiper belt, and even further objects which orbit the sun.

    The reason Pluto was assumed to be the size of the Earth when it was discovered in 1930 was a combination of factors – its brightness, its distance, and assumptions about how reflective it’s surface is (is it rocky or icy). There was also another assumption – that a planet beyond Neptune’s orbit was needed to account for anomalies in Uranus’s orbit. (It turns out there were no anomalies, just the limitations of the accuracy of observations of Uranus and Neptune’s orbits – including observations made in the 1800s manually, before the use of film for astronomical purposes).

    With each serious observation of Pluto from 1930 to 1980 the maximum possible size shrank. My college astronomy professor suggested that if the trend continued Pluto would effectively vanish by the end of the 20th century. It wasn’t until the discovery of the moon Charon that hard estimates could be made for Pluto’s size and mass.

  33. Jari says: September 22, 20111:24 pm

    Phil: That’s why the continent is actually called Eurasia. Which effectively drops the bottom out of the “Pluto is a planet” sentence. Anyway, I look forward, when New Horizon gets there, regardless of classification of Pluto.

  34. Laurel Kornfeld says: September 22, 20111:34 pm

    #33, your argument does not “drop the bottom out of the ‘Pluto is a planet sentence.'” First, the term “Eurasia” is rarely used, and almost every textbook lists Europe and Asia as separate continents. Even if this were corrected, it has nothing to do with Pluto. The division of Europe and Asia is arbitrary. So is the designation of “dwarf planets” not being planets. The fact is, in terms of what they are, dwarf planets are very much akin to planets. They are large enough in mass and size to be rounded by their own gravity; have geology and weather; and are often geologically differentiated into core, mantle, and crust just like Earth. This makes dwarf planets much more like the bigger planets than like shapeless asteroids and comets that are nothing more than rocks or iceballs shaped by their chemical bonds. In fact, New Horizons Principal Investigator Dr. Alan Stern is the person who first coined the term “dwarf planet” in 1991, and his intention was to create a third class of planets in addition to terrestrials and jovians, small planets large enough to be rounded by their own gravity but not large enough to gravitationally dominate their orbits. He never intended for dwarf planets to not be considered planets at all.

  35. Phil says: September 22, 20111:52 pm

    Okay, along with demoting Europe since it’s not a continent (see #34) let’s demote Indigo as a color on the rainbow.

    It should be clear to anybody looking with an unbiased view that the continents are North America, South America, Antarctica, Australia, Africa, and Asia – with Europe just a subset of Asia just as Patagonia is a subset of South America. (Greenland is no where large enough to be considered a continent – it’s just a flaw in Mercator projection maps which makes it look so large.)

    Likewise looking at the rainbow it’s clear that the visible colors are Red, Orange, Yellow, Green, Blue, and Violet. Indigo is just a transition between Blue and Violet, no more of a color than Yellow-Green or Orange-Yellow (unless you’ve got a 64 box of Crayola crayons of course). From what I’ve read Newton thought that 7 was a mystical number (seven seas, seven days of the week, seven planets in his time (Mercury, Venus, Mars, Jupiter, Saturn, Sun, and Moon – the Earth didn’t count), etc.) so when he discovered that white light was actually the combination of all colors he “found” seven colors in the rainbow. It’s interesting to note that most modern pop-art rainbows (the Apple logo, the gay flag, etc.) use six colors – I suspect that’s because most folk can’t figure out which crayon (or Panatone) color to use for Indigo. 🙂

    The point I’m making is it’s all arbitrary – it depends on who makes the definitions. Pluto is a planet and Europe is a continent if you want them to be planets and continents.

    Culturally Pluto is a planet, the only one discovered by brute force. But from an astronomical point of view it’s incredibly difficult (if not impossible) to make a sensible definition of what is a planet which includes Pluto but not the other minor planets.

  36. Laurel Kornfeld says: September 22, 20112:04 pm

    “But from an astronomical point of view it’s incredibly difficult (if not impossible) to make a sensible definition of what is a planet which includes Pluto but not the other minor planets.”

    This is just plain not true. First, Pluto is not a “minor planet.” The term “minor planet” is a synonym for asteroids and comets, objects too small to be rounded by their own gravity. Dr. David Weintraub discusses this is his book “Is Pluto A Planet.” These objects are planetoids. There IS a strong scientific, sensible definition of planet that includes not just Pluto but all dwarf planets. It’s called the geophysical planet definition. According to the geophysical planet definition, a planet is any non-self-luminous spheroidal body in orbit around a star. In other words, if the object is large enough to be rounded by its own gravity, it is not a “minor planet” but a dwarf planet, which is a subclass of planets, at least according to this definition. The problem is only if one assumes there are only two classes of planets, terrestrials and jovians. If one accepts that there are three rather than two classes of planets, with dwarf planets being the third category, then it is not at all difficult to have a sensible planet definition that includes Pluto. Yes, such a definition also includes other small spherical bodies orbiting the Sun such as Ceres, Haumea, Makemake, and Eris. Just like we have a wide spectrum of stars, as demonstrated in the Herzsprung-Russell Diagram, we also have a wide spectrum of planets.

  37. Phil says: September 25, 20112:06 am

    I should have been more specific. Let me rephrase it as it is incredibly difficult (if not impossible) to make a definition of what is and isn’t a planet which includes Pluto as one of the nine planets in the solar system.

    It’s easy to count eight (per Pluto’s demotion) and that is a non-arbitrary criteria.

    It’s easy to have 11 (including Ceres, Pluto, and Chiron) – although you’ve got to set some limits (distance or eccentricity) to leave out the other Trans-Neptune objects.

    I don’t disagree that we do have a wide range of planets – gas giants, rocky, etc. and that the dwarf planets (or whatever label you wish to use) do count as planets, just as asteroids count as “microplanets”.

    When there was less knowledge about the solar system it was easy to label objects as planets, moons, asteroids, and comets. But as we gain more knowledge we’ve got to have more sub-categories and objects which can fit into multiple categories, and those labels will also change as further knowledge is gained.

  38. Laurel Kornfeld says: September 25, 20111:26 pm

    When you say it’s easy to count “Ceres, Pluto, and Chiron,” are you referring to Chiron the centaur orbiting between Saturn and Uranus or Charon, Pluto’s moon?

    As you can see from my comments above, I am not at all wedded to the notion of having nine planets in our solar system. In fact, I like the way Alan Boyle, in his book The Case for Pluto, describes our solar system’s planet count: Four (terrestrials) plus four (jovians) plus more (dwarf planets). The number of dwarf planets is in flux as more are being discovered. So far, there are five recognized by the IAU that are known to be large enough to be spherical, and three more were just discovered. There are others, such as Quaoar and Ixion, for which we do not yet have sufficient data to determine what I see as the crucial factor in determining whether an object is a type of planet–that is, whether it is large enough and massive enough to be rounded by its own gravity. As for Charon, I can see it being counted jointly as a dwarf planet (part of a binary dwarf planet system) and as a moon/satellite planet since the barycenter between Pluto and Charon is not within Pluto but between the two bodies.

    Dynamicists can make a case for eight planets; however, the IAU definition does a poor job at accomplishing this, with its vague terms requiring objects to “clear their orbits” and its complete exclusion of exoplanets.

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