The Transiting Exoplanet Survey Satellite (TESS) from NASA could hold a Clue to The Mysterious Planet Nine.
In the far reaches of the Solar System there seems to be something big lurking, messing with some of the Kuiper Belt’s orbits rocking past Neptune. Some astronomers think it’s a planet, about five times the Earth’s mass. They are calling it Planet Nine.
But it’s not so easy to find this possible lurker. It would seem incredibly small and faint from here, and we don’t even know where to look in the sky. Astronomers quest (and find some other really nice things in the process), but it’s slow and painful work.
However, there might be another way, according to a new paper: The Transiting Exoplanet Survey Satellite (TESS) from NASA. And the planet has already been observed, it is possible, and it is hidden in the TESS data.
You may think “duh, it’s a planet-hunting telescope,” but there are two different things to look for planets that are very far away and to look for planets that are relatively close.
TESS uses the transit approach to search for exoplanets. It looks for long duration to a particular section of the sky, looking for faint, regular starlight dips caused by planets orbiting between us and the star (known as a transit).
In the case of Planet Nine, it would be impossible to detect its transit, as it would not pass between TESS and the Sun.
And a single exposure would not reveal such a faint object as Planet Nine. The way TESS looks at sections of the sky, however, could be combined with a technique of astronomy called digital tracking.
TESS takes a lot of pictures from one field of view to reveal transit dips. Faint objects can become much clearer when you stack these images, exposing objects that would otherwise be hidden.
Since Planet Nine is a moving body, it would not automatically reveal the planet just by stacking the images. That is where you need to do some guesswork to measure the object’s estimated orbit and kind of change the exposures to concentrate on your projected location-and then stack the pictures.
“We can try all possible orbits to find new objects with unknown trajectories,” the researchers wrote in their paper.
Just feed the images and orbit and parallax corrections into a software program and wait for the results (TESS has a highly elliptical orbit around Earth, so the line-of-sight is moving).
It sounds like an approach to scattershot, but it could actually work. For example, the Hubble Space Telescope used digital tracking to discover a number of objects out past Neptune.
The next question is if TESS is sufficiently powerful to detect the planet. But there is also a way to test it.
Models indicated that Planet Nine has an apparent magnitude between 19 and 24 – that is, brightness as seen from Earth. Several known trans-Neptunian orbital objects within this range have apparent magnitudes -namely, Sedna (20.5 to 20.8), 2015 BP519 (21.5) and 2015 BM518 (21.6).
So, to solve each of these three objects the group used digital tracking… and all three showed up, clear as a crystal that was really blurry in low resolution. But it can still be identified. You can see them in the image above: Sedna, 2015 BP519 and 2015 BP518 is from the left. The photos are shown in negative to make it easier to see the objects.
Hypothetically, at these magnitudes, TESS should be able to see any object. That means it should also be able to see Planet Nine, the researchers said. It may even be in the data – just haven’t found it yet.
You would have to search for all orbits that might require a lot of computation. So … Does anyone have a supercomputer of their own?
The research was published in the AAS Research Notes.