No Tenth Planet Yet From IRAS

Several times per year, IPAC gets the same question about:

Is there any truth to the rumor that IRAS discovered a very distant mystery celestial body beyond Pluto about 4 times the size of earth and moving in our Direction?

The short answer is "no", no one has demonstrated that IRAS observed any solar system body at a distance beyond the known planets.

IRAS cataloged 250,000 sources in the Point Source Catalog, supplemented by an additional 100,000 in the Faint Source Catalog, and the vast majority of these have not been followed up to date. IPAC did optical associations to the catalogs, which showed that most of the sources outside of the Galactic Plane had not moved between the epoch of the optical observations and the IRAS observations, and therefore were non-solar system bodies. However, most of the sources in the Galactic Plane have no optical counterparts due to optical obscuration in the Plane, and hence one of those sources could indeed be such a body. When 2MASS completes its survey, a cross-correlation of those two catalogs will establish whether any of those sources show any motion.

There are at least three sources of the rumor that IRAS observed such a mystery source:

  1. A paper published in the March 1, 1984 Astrophysical Journal Letters (278:L63) by Houck et al titled Unidentified point sources in the IRAS minisurvey discussed nine 60 µm sources which had "no counterparts in a variety of catalogs of nonstellar objects. Four objects have no visible counterparts."

    It was speculated in that paper that the sources could be either a galaxy emitting much more infrared radiation relative to optical radiation than usual; or be a cool object in the outer solar system; or be a brown dwarf just outside the solar system; or be something else.

    This paper caused quite a commotion in the press when this was publicized at a press conference in Washington, D.C.:

    Headlines read "Giant Object Mystifies Astronomers" and "Mystery Body Found in Space." In The Washington Post was the headline and story "At Solar System's Edge Giant Object is a Mystery --- A heavenly body possibly as large as the giant planet Jupiter and possibly so close to Earth that it would be part of this solar system has been found in the direction of the Constellation Orion by an orbiting telescope called the IRAS. So mysterious is the object that astronomers do not know if it is a planet, a giant comet, a 'protostar' that never got hot enough to become a star, a distant galaxy so young that it is still in the process of forming its first stars, or a galaxy so shrouded in dust that none of the light cast by its stars ever gets through. 'All I can tell you is that we don't know what it is,' said Gerry Neugebauer, chief IRAS scientist."
    from an interesting webpage, The Planet Nibiru (page no longer online; see a copy of it).

    See The full Washington Post article.

    These objects were therefore "mystery objects", at least until the mysteries were solved in short order. These sources all turned out to be distant galaxies except one which was a wisp of Galactic infrared cirrus (Soifer 1987, Annual Review of Astronomy & Astrophysics 25:187), and no such source has ever turned out to be a solar-system object.

    Nonetheless, The Planet Nibiru goes on to say:

    The United States Government squashed the story immediately! For some arcane top-secret reason the government doesn't want to alarm or panic the general public by disclosure of this discovery. Why? Because a race of super-beings inhabits that planet, and common knowledge of this fact would have people screaming in the streets.

    Somehow the author of that page missed the following papers which reported the follow-up results for the eight galaxies out of the nine sources:

    but that is probably understandable, since few non-astronomers read the technical astronomical literature, and since no press conference was held to announce those results. Even if a press conference had been held, it probably wouldn't have been published by the press anyway since this news wasn't nearly as exciting.

    The amusing thing is that probably every one of those authors, and certainly myself as well, would much rather have these "mystery objects" turn out to be a solar-system object filled with life. (Although perhaps not inhabited by a race of "super-beings" - the fun would go out of science for us if we were hopelessly behind these "super-beings" in science abilities....) Further, I take no small amount of pleasure in being designated as part of a U.S. Government conspiracy to "squash" this delightful story!

  2. Nearly everyone on the IRAS Science Team who looked at the early IRAS data found at least one source that they initially thought could be "the tenth planet". Many of these observations turned out to be IRC+10216, a bright previously known source which is almost exactly in the ecliptic plane (the plane of the planets). I found a 12 µm source at high galactic latitude without an optical counterpart which was thought to be a potential brown dwarf for about a week, during which time rumors circulated through the astronomical community. The rumor came back to me in a much-changed form, as all rumors do, into a possible report of a tenth planet, so this could be another source of a "mystery object". This 12 µm source turned out to be a peculiar carbon star, quite distant.

  3. J. Fowler found a "mystery source" near the nucleus of M31, the other large galaxy in our Local Group of galaxies.

    From Carol Lonsdale:

    I may also have traced the origin of the actual rumor. It could be due to an investigation into a strange source found in the galaxy M31. Several IRAS team members identified this bright and extremely cold source close to the nucleus of M31, and studied it closely because it had such peculiar characteristics for actually being in the galaxy. At one point it was called ``the mystery source''. For a time it was believed to be in the solar system because it was thought there was evidence for motion. However that evidence was finally shown to be due to hysteresis (the after effect on the detectors of crossing bright sources) due to the nucleus of M31; the hysteresis caused the effect to occur in different directions on scans passing over M31 at different angles. IPAC's John Fowler is the person who followed up this peculiar object and provided this information. The study was never published.

    Please make it quite clear that this source is not thought to be in the solar system. It's probably an AGN behind M31. I'd hate to start a new rumor about tenth planets or Earth threatening asteroids!

    More detailed explanation from J. Fowler:

    It seems remotely conceivable that multiple retellings (with plenty of transmission errors) could have mutated the following into something resembling this idea.

    When George Aumann and I first tried computing flux-ratio maps using HiRes images of M31 at 60 and 100 microns, we each noticed what seemed to be a VERY cold object near the nucleus, about 4 arcmin NW of it. After I had gotten Mike Melnyk's cross-band simulation idea working, I was able to get compatible-resolution images to compute ratios from, and along with the fitting-variance images, the evidence that the object was real and very cold became undeniable. We were unable to construct an astrophysical model that fit this observation, and invited others to try. Francois Boulanger studied the images in all wavelengths and claimed it was some sort of cirrus, having the spectrum of cirrus over the four bands; George claimed that Francois had no S/N in any band but 100 microns, and I had to agree with George. Attempts to associate the object with known objects in the UV, X-Ray, CO maps proved fruitless. Dave van Buren looked at about a dozen possible models and concluded that (as I recall) nothing was satisfactory, but the closest would be an AGN seen THROUGH M31.

    I tried checking the object at different epochs to see if anything was variable. The photometry appeared stable, but by comparing AOs taken in February with survey observations in June, I was able to show that the data were incompatible, with a very high statistical significance (seems like 25 sigma or so, as I recall). This incompatibility applied ONLY to the mysterious object; nothing else in the image was inconsistent between the two epochs. I concluded that the object could be local, i.e., the inconsistency could be due to motion of the object, since the flux seemed the same.

    The best-fit motion was about 45 arcsec IN THE ECLIPTIC DIRECTION. With the assumption of a circular solar orbit with the motion due to the Earth's orbital motion (creating parallax on a distant body), and given the time baseline and solar elongation, I got about 3000 AU. The flux was pretty much all in the 100 micron channel, so at 3000 AU, the total absolute flux came out about 0.7 times Jupiter's luminosity.

    However, this motion is entirely compatible with the effects of hysteresis in the IRAS detectors, and thus I found the entire nonstationary effect to be explainable as hysteresis.

See also Paul Schlyter's great webpage giving the history and follow-up of most hypothetical planets (mirror site 1 and mirror site 2). Paul discusses the curious report of John Anderson of JPL, who in 1987 analyzed the motion of Pioneer 10 and 11 and found no evidence of any unknown gravity forces affecting those spacecraft, yet who concluded "that a tenth planet most likely exists" from that observation! This is sometimes confused with the IRAS mystery object as well, since an Astronomy magazine article in October 1982 mentioned them together.

Reader's may be amused by a synopsis of some of the following site, The Planet Nibiru:

Sirius and the Sun are gravitationally tied systems, orbiting Alcyone in "the Pleiades Quadrant". 500,000 years ago another planet in the Sirius system, Nibiru, "strayed off course" and "drifted our way", was "unwittingly captured by our Sun" and is now at the edge of our Solar System, inhabited by "a reptilian super-race". To stay warm, they nabbed some gold from Earth, via a spaceport in Kuwait, and now have a nice gold heat-shield all around their planet. Later a collision of one of Nibiru's moon's with Earth created the Pacific Ocean, with all the ejecta creating the asteroid belt. And there's more....

If any IRAS people remember further 'mystery planet' tales, please let me know.

Comments and Suggestions to: Tom Chester
Last modified: 5 May 1998 (url of planet nibiru updated 26 February 2000, and as of that date no one has yet found a tenth planet despite further searches)