Newly Found Planetoid Possibly Larger than Quaoar

I am Jack's username writes "A newly discovered planetoid (Google news cluster) 2004 DW in the Edgeworth-Kuiper belt, where some think objects larger than Pluto exist, may be larger than Quaoar - making it the second largest known trans-Neptunian object and 18th largest object in the solar system."

Comments

Re:Quaoar

[PhuCknuT]

Yeah, because the most distant galaxies are about 1000000000 (not exact, but you get the point) times larger and brighter than an asteroid 40au from earth. An asteroid or comet only reflects light, so the farther it is from the sun the harder it is to see. A galaxy on the other hand, will have billions of stars, each billions and billions of times brighter than what's reflected from an asteroid.

Re:Question for the astronomers among us...

[sdedeo]

I think the numbers are off relative to each other by many orders of magnitude. The real problem is that both KBOs and stars are essentially points. The chance of accidental overlap is vanishingly small. (If you stuck a telescope and watched a field of stars for brightness variations, you would see a lot of other stuff: eclipsing binaries, orbiting planets, etc -- see the OGLE project, e.g. They have been recently looking for eclipsing planets, but there are huge numbers of contaminants from plain old binary systems.

You need some mechanism to "increase" the apparent area of the (in this case KBO.) Unfortunately, KBOs are just small rocks, with not too much interesting going on. (Planets that eclipse their own star are easier to see, because they are fixed in the angle they explore on the sky relative to the star.)

If you're looking for some kind of "eclipse" effect on the background stars, the best way to increase the effective area of your object is to make it heavy enough that it can gravitationally lens something behind it. The lensing effect increases the angular size of the "sweet spot." See the various MACHO searches.