evidence for a 9th planet

[Umbran]

What does "close to the galaxy" mean in this context? Obviously it's in the galaxy; does that refer to it being in the direction of the galactic centre and thus possibly hard to see against the brighter background in that direction?

Sorry, I realized that I needed to edit that in. They mean that in terms of apparent position in the sky - Planet X probably has the band of the Milky Way behind it, making it difficult to find in the wash of light from the galaxy.

 

[Ryujin]

What does "close to the galaxy" mean in this context? Obviously it's in the galaxy; does that refer to it being in the direction of the galactic centre and thus possibly hard to see against the brighter background in that direction?

I would have thought that one of the ways to "see it", would be to look for known objects that it occludes.

 

[tomBitonti]

I would have thought that one of the ways to "see it", would be to look for known objects that it occludes.

I was wondering this, too.

Thx!
TomB

 

[Janx]

Including the named Dwarfs isn't there something like 20 Planet-things in the Solar system now? These kinds of announcements don't really spark the imagination like they use to as Planets are getting to be a bit common - its like they're out there just trying to find a little bit of space

that's the thing I was joking about. When I grew up, there were 9 planets.

Not being an astronomy person, at best, I now know Pluto is a dwarf planet.

Otherwise, I have no clue what these other 11 non-asteroid things orbiting the sun are called or roughly where they are.

 

[Umbran]

I would have thought that one of the ways to "see it", would be to look for known objects that it occludes.

Such occultations don't happen that often. From 1800 to 2100 there were only about 30 instances of planets in our solar system occulting known bright stars (other than the Sun, that is). That means it happens about once every couple of years.

https://en.wikipedia.org/wiki/Occultation#List_of_mutual_planetary_occultations_and_transits

This sounds surprising, because you figure there are a lot of stars. But remember that the occultation happens only when there is a *very* straight line from Earth, to the planet, and then to a bright star. It isn't like there's a huge disc of the Moon here - the planet itself is basically a dot, one pixel or less, passing in front of another dot.

Now, try to find that happening when you don't know where the planet is, or which star might be occulted, when you don't even know if you had a telescope pointing in the right direction when it happened.

 

[Ryujin]

Such occultations don't happen that often. From 1800 to 2100 there were only about 30 instances of planets in our solar system occulting known bright stars (other than the Sun, that is). That means it happens about once every couple of years.

https://en.wikipedia.org/wiki/Occultation#List_of_mutual_planetary_occultations_and_transits

This sounds surprising, because you figure there are a lot of stars. But remember that the occultation happens only when there is a *very* straight line from Earth, to the planet, and then to a bright star. It isn't like there's a huge disc of the Moon here - the planet itself is basically a dot, one pixel or less, passing in front of another dot.

Now, try to find that happening when you don't know where the planet is, or which star might be occulted, when you don't even know if you had a telescope pointing in the right direction when it happened.

Oh, I certainly get that we're dealing with point sources here, but I figured that the the dense starfield of the Milky Way would create an almost ideal condition for looking for occlusions. From my understanding typically a negative image is used because black dots are easier to see patterns in than are white ones, and we've got some pretty impressive computer horsepower to do the initial sorting these days. The hard part would be in narrowing down the area of sky to look at, but that's what orbital perturbations are for.

 

[tomBitonti]

Someone must have figured the probability of an occultation.

See, for example, http://www.slac.stanford.edu/pubs/slacpubs/12000/slac-pub-12216.pdf

'Search for Small Trans-Neptunian Objects by the TAOS project

TAOS is Taiwan-American Occultation Survey

I'm guessing that for this to work there would need to be a good initial guess at the target detection location.

Thx!
TomB

Edit: some data regarding a different but similar Planet X

http://www.zetatalk.com/usenet/use00932.htm

and according to Starry Night, Pluto is currently 29.48 AU
from Earth or 29.48 times 1.496*10^8km from Earth or 4.410
billion km.

Summarizing:

Pluto Diameter...: = 2,274 km
Pluto Distance...: = 4,410,000,000 km
Planet X Diameter: = 51,024 km
Planet X Distance: = 53,288,000,000 km

Calculating:

AAS Pluto...: = 2,274 / 4.410*10^9 = 515.67*10^-9 radians

AAS Planet X: = 51,024 / 53.288*10^9 = 957.51*10^-9 radians

So the apparent angular size of Planet X is greater than the
apparent angular size of Pluto by:

(AAS Planet X) / (AAS Pluto) = 957.51 / 515.67 = 1.857

This indicates to me that if using the same telescope,
Planet X, if it could be seen today, should appear nearly
twice as large (1.857 times) as Pluto.

 

[Umbran]

Oh, I certainly get that we're dealing with point sources here, but I figured that the the dense starfield of the Milky Way would create an almost ideal condition for looking for occlusions.

Most of that dense starfield is just that - a starfield, not a collection of known objects. Something less than 1% of the stars in that dense starfield have been cataloged.

From my understanding typically a negative image is used because black dots are easier to see patterns in than are white ones, and we've got some pretty impressive computer horsepower to do the initial sorting these days. The hard part would be in narrowing down the area of sky to look at, but that's what orbital perturbations are for.

Now, note that I also spoke about occultation of "bright" stars. That's because there are actually lots of stars in the catalog. Too many. Like, a bit short of 950 million in the Guide Star Catalog. There is no way you're going to watch to see which of 950 million stars got occulted. It doesn't matter how impressive your computer power is. The fact of the matter is that we are not *constantly watching* 950 million objects. We are not taking nightly catalogs of the entire sky that resolves each star. We have not even taken nightly catalogs of the regions we suspect the planet is in, because we had no reason to. The data you'd want simply has not been collected.

Specifically bright stars, however, get a bit more attention, but there are far fewer of them, and that leads to the problem that in all likelihood, none of those *just happen* to be in the path.

In addition, as I've been writing I've been realizing - we are talking about a thing that has an orbital period of 10,000 to 20,000 years. That means, since the time of Galileo, it has gone across an arc of *at most* 14 degrees of sky - a smidge less than the distance across the sky the Sun or Moon moves in an hour. In the time that we've had really serious telescopes and major catalogs such that we might have seen the occultation, it has gone more like 1 degree of sky - the distance the Sun or Moon moves in about 4 minutes (plus a little bit for parallax).

So, not a lot of opportunity for occultation.

 

[Hand of Evil]

Planet Nine, sounds like a sci-fi movie

 

[Jhaelen]

Planet Nine, sounds like a sci-fi movie

Small wonder, as there's already a (in)famous movie with that title:
Plan(et) 9 From Outer Space!