The Futile Search for Planet 9

I got interested in Planet 9 a week or so back. Planet 9 is a theoretical planet, estimated to be 3 or 4 times the size of the Earth, in a highly elliptical 20,000 year orbit around the Sun. And a new website was calling for volunteers to look at starfield photos to try to spot moving bodies – and hopefully Planet 9 – among the fixed stars. Here’s a full-size example of one of the photos they were supposed to look at:

The numbers along the side are degrees Declination, and along the bottom degrees Right Ascension. So we’re looking at a piece of sky 0.25 degrees square. For comparison, the apparent diameter of the Sun and Moon are about 0.5 degrees.

The idea was for people to look at a rapid succession of images of the same 0.25 x 0.25 degree patch of sky, taken at different times, and try to spot stars that were moving.

I rapidly decided it was an impossible task.

For all I could see was a whole bunch of things jiggling around. Everything was jiggling around. And the brightest stars were surrounded by what seemed to be halos as well. It was futile to even try.

Eventually, I got hold of the images in my MS Paint utility, and used its cursor to give me the X-Y pixel locations of one particular little blue star in each photo. I found it was moving around by several pixels from one image to the next. In the example below (click on the image for full size version), the little blue star was 4 pixels different in X, and 3 pixels different in Y, in just these two images. It wasn’t much better with other images either. No wonder everything was jiggling around: even the fixed stars weren’t fixed.

Eventually, I took all 4 photos of one particular patch of sky, and used MS Paint to line them up properly (or what I thought was properly ) over each other, and wrote a little programme to remove all the “stars” that didn’t appear in the same place in every photo.

Here’s the result (right) with fixed stars shown in white, everything else black. I’d managed to pull out a relatively small number of bright fixed stars from the murk. Included among them was the little star I’d used to re-align the images.

It looks like there may be a lot of noise in these images.

I left a comment on the website saying I thought that the stars were misaligned. I thought that the moderators would come back and say, “Yes, we know they are misaligned. But it’s the best we’ve got.” But nobody commented at all for about 4 days, until some guy said that he too had concluded that the stars were misaligned. Nobody else seems to have noticed.

And they’ve got 16,000+ volunteers scouring these misaligned starfield images for Planet 9!

It’s like getting people to watch a video of a football game where the players are standing kicking the ball around between them, and asking them to spot the moving ball. Only the video is so jumpy that all the players are jiggling around, and the ball is jiggling around as well, and so is everything else.

It’s a great idea for a crowd-sourcing project. And the website and the comments and everything was really pretty slick. But the entire project was badly compromised by giving them such poor quality starfield images to compare. Couldn’t they have got the images properly aligned before asking 16,000 people to devote (waste) hours of their precious time looking at them?

I couldn’t be bothered. And I bet they never find Planet 9. But it got me interested in starfield image analysis. It’s something I’ve not looked into before. I’ve been figuring out different ways of correctly aligning multiple starfield images. I’ve already got 2 computational methods sort of working. And I’ve got a few ideas about how to pull out moving stars from starfields composed of fixed stars.

So I’ve been wasting my precious time slightly differently.