Next Mercury Sized Object In The Solar System?

[jkmccrann]

Just a thought, given this whole issue of defining a planet is raging at the moment - when do people think the next Mercury-sized object will be discovered in the Solar System?

In fact, its been nearly 160 years since the discovery (and subsequent confirmation), of an object larger than Mercury in the Solar System.

The 160th Anniversary of the discovery of Neptune is coming up on September 23rd, and the 160th Anniversary of the discovery of Triton is coming up a few weeks later on October 10th.

(In fact other notable Anniversaries in terms of Solar System object discovery coming up are the 200th Anniversary of the discovery of Vesta on March 29th 2007 & the 400th Anniversaries of the discoveries of the Galilean Moons - due to happen in January 2010 - Does anyone think they'll be reclassified as Planets of some description by the time their Anniversaries roll around in 3 1/2 years?)

So, when do you guys expect to see a Mercury sized KBO, SDO, OCO or whatever playing havoc with whatever definition is eventually settled upon?

[George]

There seems to be respectable models demonstrating a lot of planetary activity in the solar accretion disk. Planets can migrate into their host star; the larger planets may migrate faster, maybe. I suspect this migration, along with the number of total plaents formed (including the fried ones) could toss some Mercury-sized planets out there. Have there been any articles on this?

Also, you don't have to go all that far out there for a Mercury-sized planet to drop below a 30 magnitude level. [I'll compute if you like.]

[jkmccrann]

There seems to be respectable models demonstrating a lot of planetary activity in the solar accretion disk. Planets can migrate into their host star; the larger planets may migrate faster, maybe. I suspect this migration, along with the number of total plaents formed (including the fried ones) could toss some Mercury-sized planets out there. Have there been any articles on this?

Also, you don't have to go all that far out there for a Mercury-sized planet to drop below a 30 magnitude level. [I'll compute if you like.]

Yep, feel free to make any interesting calculations you like on this matter!

[Ara Pacis]

I voted 2006-2008 because of recent activity by Mike Brown, et al.. It's reported that his team is working on several new items. In recent quotes, he seems to come across as nonchalant with regard to the status of his discoveries, like "Xena" and other TNOs. Maybe I am misreading his quotes, but I'm thinking that his team may have bigger fish to fry... possibly one or more much larger objects in the trans-neptunian region. But I'm just guessing.

[George]

The Hubble can see down to a level of about 30 magnitude. [Spitzer might do better here in this case, actually, but I'm not sure.]

The following is the distances for a given magnitude for a Mercury object.
100 AU .... 17.5 mag.
275 AU..... 22 mag.
500 AU.... 24.5 mag.
1750 AU... 30 mag.

The distance to the beginning of the Oort Cloud is about 50,000 AU, I think. However, there is an inner Oort Cloud zone that is much closer. The solar system is very, very large.

[tony873004]

Keep in mind, our main obstacle in finding such an object is not our ability to detect faint objects. The difficulty is in detecting slow objects. There may already be many pictures of > Mercury size objects, but if they don't move fast enough for our detection techinques, we can't tell them from a background star.

Xena is a perfect example. It's the 4th brighest KBO, yet over 500 KBOs were discovered before it. Why? Because the detection techniques, in an effort to reduce false positives to a managable number, did not look for objects that moved less than about 1.5 arcseconds per hour. It was only after they lowered the search threshold to 1 arcsecond per hour that Xena was found.

An Earth-sized (or larger) object could be lurking at 2x Xena's distance, moving at 0.5 arcseconds per hour and go completely undetected.

[Lord Jubjub]

What is the likelihood that New Horizons will image something large once it turns away from Pluto?

[Eckelston]

I'm pretty sure it won't be Hubble that finds the next large KBO. It will either be a dedicated survey (a la Brown and his team) or a general purpose survey imaging large parts of the sky at rapid intervals. PAN-STARRS is the only such project I'm aware of and it won't be running before 2008.
After that the question is whether there is a Mercury sized object within 500 AUs and the answer to that is more likely to be yes than no.

[Doodler]

I picked 2008-2015, and my personal belief is that the mode of detection will be the result of a passive occultation sweep of some part of the sky well off the ecliptic.

[George]

After that the question is whether there is a Mercury sized object within 500 AUs and the answer to that is more likely to be yes than no.

Has this been discussed much lately. [I have eschewed much of the Plutomania.]

I would think you are probably correct. There seems to be more support for migration of large, early planets. I would guess these large bodies alone, drifting in toward, and into, the sun, would do some heafty slinging of smaller planets.

[Eckelston]

Has this been discussed much lately. [I have eschewed much of the Plutomania.]

No idea. My brain filters out threads with Pluto or planet definition in their title.

I would think you are probably correct. There seems to be more support for migration of large, early planets. I would guess these large bodies alone, drifting in toward, and into, the sun, would do some heafty slinging of smaller planets.

Though less likely I think finding a captured object near perihelion is not entirely impossible either.

[ToSeek]

I'm pretty sure it won't be Hubble that finds the next large KBO. It will either be a dedicated survey (a la Brown and his team) or a general purpose survey imaging large parts of the sky at rapid intervals. PAN-STARRS is the only such project I'm aware of and it won't be running before 2008.

Very likely true. Hubble's field of view is like looking through the end of a soda straw - it's not intended to be a survey instrument.