Ixnay to Planet X – no sign of ‘death star’ in WISE sky survey

Tyche, a hypothetical large planet, was proposed to account for the regular pattern of biological extinctions across Earth’s history. It was thought that a large planet or small star hiding out far from the sun could sweep through bands of comets in its orbit, periodically sending flurries of them hurtling our way. Data from WISE nixed the idea.

Just two days ago a reader asked whether NASA’s Wide-field Infrared Survey Explorer (WISE) had found any sign of a hypothesized companion to the sun dubbed “Planet X” also known as “Nemesis”, “Tyche” and “Nibiru”.  After searching through hundreds of millions of images and turning up no sign of the object, it looks like we can finally put the idea to bed.

The third closest star system to the sun, called WISE J104915.57-531906, is at the center of the larger image, which was taken by NASA’s Wide-field Infrared Survey Explorer (WISE). Credit: NASA/JPL/Gemini Observatory/AURA/NSF

WISE swept the sky once in 2010 and again in early 2011. Objects close to us appear to move faster than distant objects when viewed over time. Nearby stars appear to move more quickly across the sky than distant ones much like a low-flying plane appears to zoom by compared to the same plane flying at high altitude.

By comparing images taken by WISE six months apart, astronomers have found thousands of stars and brown dwarfs in our sun’s “backyard” by flagging those moving fastest.

All told, WISE turned up 3,525 stars and brown dwarfs within 500 light-years of our sun, objects totally overlooked or unseen by ground-based optical telescopes. Take the pair of brown dwarfs hidden practically under our noses only 6.5 light years away. Called WISE J104915.57-531906, it’s the third closest star system to Earth and the closest discovered since astronomer E.E. Barnard spotted “Barnard’s Star” in 1916 nearly a hundred years ago.

Data from WISE has found no evidence for a hypothesized body sometimes referred to as “Planet X.” The chart shows that WISE can easily spot a Jupiter-sized object out to 10,000 AU, but if one existed at 100,000 AU, it would too faint to see. Credit: Penn State University

But WISE’s two complete infrared sweeps of the sky found that no object the size of Saturn or larger exists out to a distance of 10,000 astronomical units (AU), and no object larger than Jupiter exists out to 26,000 AU or 2.4 trillion miles. One astronomical unit equals 93 million miles or Earth’s distance from the sun. Dwarf planet Pluto orbits about 40 AU from the sun.

Illustration of the WISE spacecraft orbiting Earth. The probe was put into hibernation at the end of its mission in 2011 and then re-activated late last year as NEOWISE. NEOWISE will survey for comets and asteroids. Credit: NASA/JPL-Caltech

“The outer solar system probably does not contain a large gas giant planet, or a small, companion star,” said Kevin Luhman of the Center for Exoplanets and Habitable Worlds at Penn State University, University Park, Pa., author of a paper in the Astrophysical Journal describing the results.

Meanwhile, astronomers have been sifting through the reams of WISE data since the probe wrapped up its mission in 2011. In addition to the new stars mentioned, the orbiting spacecraft captured photos of nearly 750 million asteroids, stars and galaxies. Since scientists continue to pour over the data, there’s a remote chance a Planet X might be found, but much more likely we’ll continue to find other stars never seen before in regular optical telescopes.

14 Responses

  1. Bob Crozier

    So, just out of curiosity, how close would a brown dwarf or red dwarf star system have to come in traveling past our solar system in order to cause significant changes in the orbits of Oort cloud objects? How much closer would it have to pass in order to effect changes to the Kuiper Belt objects? And if something like that did pass by close enough to effect Kuiper Belt objects, how huge would the effect have been in the Oort cloud?

    1. Profile photo of astrobob

      Great questions that I’m not able to answer definitively. It’s long been thought that Milky Way stars, giant molecular clouds and matter ‘tides’ in the disk of the Milky Way can trigger comets in the Oort Cloud to drop into the inner solar system. As for how close a star or something as small as a brown dwarf has to come, I’ve always wondered but have never seen figures.

  2. Troy

    I’ve seen a hypothesis that impacts (and corresponding mass extinctions) correlate with the solar system entering galactic arms during its 200 million year orbit of the galactic center. For example in 6 million years the solar system will penetrate the Orion arm of the galaxy where presumably there is a pool of possible impactors. I find it interesting anyway.

      1. Troy

        Most large impactors when and where they occur is known. If you chart out when the Solar system enters various arms of the galaxy (during its galactic orbit) with these impacts there is correlation between the impacts with the solar system crossing galactic arms. Keep in mind even the author refers to it as a hypothesis so how the exact mechanism manifests itself isn’t even mentioned. It also assumes a galactic circuit every 186 million years, so there may be a bit of post hoc number trimming to get things to work out right. (I believe the poster is the “correlated history of the earth” or something like this)

        1. Troy

          P.S. I’m not sure if I explained my response well enough. An example of an impact listed is the infamous Chicxulub impact of 66 million years ago, that likely ended the reign of the dinosaurs.

        2. Profile photo of astrobob

          I’ve never heard of us knowing where large impactors are outside the solar system. They are much too faint to see. I assume the spiral arm crossings have to do with molecular clouds – we know about their size, location.

          1. Troy

            Sorry, I don’t know enough about it to defend the hypothesis, I just thought it was interesting. Coming from within the our solar system doesn’t preclude an ultimate cause from an outside influence slightly perturbing the regular orbits, and given the time frame of millions of years sending stuff towards the inner solar system.

          2. Profile photo of astrobob

            Well Troy, who knows but that you might be right. There’s a lot of stuff out there. Stars and molecular clouds make a difference – for fun, let’s toss in a few of those rogue planets to stir things up too!

    1. Sean

      the only reason I can think of that entering a galactic arm might increase comet activity would be that there would be more matter which could possibly perturb Oort cloud residents etc, rather than “impactors” of some sort in the arm which we would “run into”. Or whatever.

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