Is Planet 9 real?  New observations fail to reveal the hypothetical orb

Is Planet 9 real? New observations fail to reveal the hypothetical orb

We have a pretty one good idea of ​​what lurks in our solar system. We know there isn’t a Mars-sized planet orbiting between Jupiter and Saturn, nor a brown dwarf enemy on its way. Anything large and fairly close to the sun will be easily spotted. But we can’t rule out a smaller, more distant world, such as the hypothetical Planet 9 (or Planet 10 if you want to throw down above Pluto). The odds against such a planet existing are quite high, and a recent study finds it even less likely.

Many astronomers had wondered about the existence of planets that could be hiding on the outskirts of our solar system, especially when the power of our telescopes was quite limited. But when large sky probes began scanning the sky, they found nothing beyond asteroid-sized worlds. But the orbits of the worlds we found seemed to be clustered in a statistically odd way, as if they were being gravitationally perturbed by a larger object. If that were the case, this “Planet 9” would have a mass of about five Earths and an orbital distance of a few hundred to a thousand astronomical units. In other words, just small enough and distant enough that it is not easily seen in sky surveys.

Naturally, this motivated people to search for the world, but it is not easy. Planet 9 would be too distant to be seen by reflected light, so you’d have to look for it by its faint infrared glow. And with a mass of only five Earths, it wouldn’t give off much heat. Added to this is the fact that such a distant planet would orbit very slowly, so in a single set of observations you wouldn’t notice it moving at all. This is where this new study comes in.

To look for distant planets, the team used two infrared sky surveys, one from the InfraRed Astronomical Satellite (IRAS) and one from the AKARI Space Telescope. The two surveys were taken more than 20 years apart, giving any hypothetical planet plenty of time to move to a slightly different part of the sky. They assumed that any distant planets would be fairly close to the equatorial plane, and then combed through the data and noted potential planets.

Surprisingly, they found more than 500 candidates. Based on the energy distribution of their spectra, most of these candidates had orbital distances less than 1000 AU and masses less than Neptune, which is exactly the range expected for Planet 9. But don’t get too excited. When the team looked at the infrared signatures by hand, they found that none of them were very convincing. Most of them tended to be either within or near a faint integrated flux nebula, also known as galactic cirrus. They are diffuse clouds of interstellar gas that are not easily seen at visible wavelengths, but instead emit infrared light.

So it turns out that these candidates are not planets, but rather the echoes of a faint nebula. Which pretty much rules out Planet 9. Hope for another planet lost in the clouds.

This article was originally published on The universe today of Brian Koberlein. Read the original article here.

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