Follow two astronomers, Mike Brown and Konstantin Batygin, as they’re on the hunt for Planet Nine — a hypothesized ninth planet at the edge of our solar system.
Inside the Search for Planet Nine
Published: June 10, 2019
Onscreen: At the top of Mauna Kea in Hawai`i, when the sun goes down, the planet hunters come out.
Mike Brown: You know, we never know. Any night could be the one where we actually find it.
Onscreen: And tonight, they are…
Hunting for Planet 9. Funded in part by Draper.
It’s a hypothesized 9th planet in our solar system that’s so far away, it’s hard to spot.
Brown: Somewhere in the sky, there is a single moderately faint object, slowly moving. Go find it. That’s the challenge.
It’s gonna be a great night. Not even as windy as it was supposed to be, I think.
Konstantin Batygin: Yep. Hopefully we don’t break the telescope.
Onscreen: The Subaru telescope at the peak of Hawai’i’s tallest mountain is perfect for the job.
Brown: Subaru is a huge telescope. It also has this camera that’s able to look at a big monster patch of sky.
Onscreen: In the control room, Mike and Konstantin get right to work. But because of the altitude, it’s hard to think.
Brown: Konstantin almost always takes oxygen.
The trick to doing this right is to think as little as possible at 14,000 feet, because thinking at 14,000 feet rarely works.
Onscreen: Fortunately, they don’t have to search the whole sky. The same gravitational physics that suggests Planet 9 exists, also predicts the orbital path of the planet through the sky.
Batygin: That orbit projected onto the night sky will appear in some swath, but we don’t know where inside that swath Planet 9 is hiding.
We know it’s orbit pretty well. We still argue about how well we know it. Mike thinks we know it better than we know it.
Brown: I think I know it better than you know it.
Batygin: Mike is delusional.
Brown: This is a map of the sky. The two big red lines show the expected path of Planet 9. Planet 9 is somewhere between these two spots in the sky.
Onscreen: They systematically take a picture at each spot in Planet 9’s orbital path.
Brown: You can see every place the telescope points is a little circle.
Onscreen: Each picture is focused on a piece of sky that is about nine times the size of the moon.
Batygin: At the end of the day, all that is going on is that you ultimately just look for an object that moved. That’s the goal.
Onscreen: To actually spot Planet 9, Mike and Konstantin will have to back the next night and do it all over again.
Brown: Basically, we have to check every single star. Every single smudge that might be there, and see if it is moving at all. Is it in the same spot last night? Is it in the same spot tonight?
Onscreen: Doing this by eye would be crazy. So, they use sophisticated software that searches for moving dots of light. And this takes time.
This method has been used to find lots of distant rocks, like Sedna and Quaor, orbiting beyond Pluto. But Planet 9 will be even fainter.
Brown: If it’s going at the right speed, that is Planet 9. The day we find it, telescopes everywhere will be able to go look at it. Because once you know the coordinates, its easy. Simple. We are going to study it and try to learn where it came from what is made of, what does it tell us about the story of the solar system and that's the real promise here.
Produced and Directed by: Caitlin Saks and Terri Randall
Camera: Dave Arabia
Digital Producer: Ana Aceves
Additional Footage: Adler Planetarium, ESO/A. Santerne, Gemini Observatory/AURA, Mike Brown, Konstantin Batygin
© WGBH Educational Foundation 2019