Thread by @plutokiller

It's now been a year since the Zwicky Transient Facility has been operating at Palomar Observatory. So it is time to answer the question everyone should have been (but no one was? maybe?) asking. Is Planet Nine in the public ZTF archive already?

ztf.caltech.edu/news/public-da…

The answer SHOULD be "probably not." ZTF runs on the relatively small 48-inch Schmidt telescope at Palomar (discoverer of Eris, Makemake, Gonggong, Sedna, and more), so unless P9 is brighter than anticipated it shouldn't show up there.

Our latest analysis (below), though, allows the possibility of P9 being closer and thus brighter than we originally thought. So it is worth combing through the ZTF data to see.

arxiv.org/abs/1902.10103

You can grab the daily ZTF data here ztf.uw.edu

So I did.

In the 1st year, ZTF reported more than 2 million individual transients near the expected path of P9.

The trick then is to ask if any 4 of those 2 million are consistent with the orbit of a distant object across the sky (4 is the practical minimum; with 3 you get a lot of chance alignments). This is a little complicated; things don't move in straight lines across the sky....

... but over the years we have developed pretty slick algorithms to pick real objects out of surveys like these. The main trick now is waiting for the computer to chug through all of the data.

... and waiting ...

... and waiting ...

When the analysis finished this week the answer was: there are 6 objects in the data that follow something that looks like a Keplerian orbit! Sadly, in detailed examination of all of them, I don't think any are real. The bottom line: Planet Nine is not in year 1 of ZTF.

How bright would P9 had to have been to be found? The answer was not obvious, so we calibrated the ZTF survey by looking for all of the asteroids that ZTF should have found. That way we know for each part of the sky how good our results are.

Here's a map of how good the survey is across the whole sky. The broad band is the ecliptic, where most of the asteroids are. We can't see the far south at all. The light blue regions don't have enough asteroids to measure. But in some places things are really pretty good.

So this means, of course, we keep looking, but at least we have verified that Planet Nine is not hiding in plain sight.

And, yes, really I should write all of this up as a real paper, but I'm leaving for Ireland on Monday so I figured Twitter is just as good no?

This thread brought to you by my desire to have something on Twitter about space today that it not idiotic.