The countless frustrated attempts to find planet 9, a hypothetical giant gas in the confines of our solar system, have aroused the ingenuity of some Taiwanese scientists.
Short. For years, astronomers have swept the sky in search of the weak reflection of sunlight that should get to us from planet 9, a demonstratedly ineffective task.
Now, a team of researchers has changed the rules of the game with an ingenious idea: instead of looking for it, they have tried to detect their heat. Well, they have found two very promising candidates.
Context. Beyond the orbit of Neptune, in an icy and dark region known as the Kuiper belt, the orbits of several objects seem to be grouped in a way that challenges chance. The trajectories of these transneptunian objects (TNos) align as if an invisible hand were guiding them.
The most accepted hypothesis to explain this behavior is the existence of an unknown massive planet, the planet 9. Of existing, this distant world would have a mass of between five and ten times that of the earth. The problem is that it would be more than 400 astronomical units, so its light would be incredibly dim. To put it in perspective, Neptune is “only” 30 UA or 4,496 million kilometers.
If we can’t see it, maybe we can feel its heat. A team from the National University Tsing Hua in Taiwan believes to have the strongest track in years on the real existence of the most wanted object in our neighborhood. The results of their study are not final, but they reach two promising candidates.
Every object with a temperature above absolute zero emits thermal radiation, that is, heat. But while the light decreases with the distance following a relationship of the inverse of the fourth power (1/d4), the heat only decreases with the square of the distance (1/d2). This abysmal difference is the argument used by researchers to focus their search on the heat signature of planet 9.
A needle in a haystack. The team resorted to the data of the Akari Space Telescope of Japan. Throwed in 2006, Akari dedicated his useful life to sweeping the full sky in distant infrared light, the perfect range to detect the thermal brightness of the planet 9. And he did it from space, without the interference of the Earth’s atmosphere.
Astronomers set out from a list of unprocessed Disssdl detections: more than 5.2 million signals with many false positives. After limiting the search zone, eliminating known objects, filtering sources contaminated by galactic dust clouds and excluding static objects, which seem to be at the same point in observations separated by months, the list was reduced to 393 candidates.
Of 393 candidates to. He touched his hands dirty. The investigators visually inspected the images of the 393 candidates. They ruled out weak detections, artifacts at the edges of the sensor and, above all, the impacts of cosmic rays that can be perceived as a specific source of heat.
After this thorough process, there were only two candidates. Two heat points that appeared where planet 9 was expected, had the predicted brightness for the theory and showed the expected movement: they were detected in the same place in a period of 24 hours, but there was no trace of them in the same place six months later.
All to demonstrate. The two candidates were baptized as FISSDL J0250422-15011 and FISSDL J0301112-164240. But to verify if these two heat points are really a single object moving in an orbit compatible with planet 9 will need new observations in visible light, with sufficiently powerful telescopes to detect its weak optical brightness and measure its movement with precision.
If confirmed, the discovery would not only solve one of the greatest mysteries of modern astronomy, but would revolutionize our understanding about how our own system was formed and evolved. Everything is to be demonstrated, but at least we have a hot trail to continue hunting.
Imagine | ESA, Hubble, M. Kornmesser, CC by
