When the still unnamed tenth planet was discovered, the claim was made that it could not be larger than 3,550 kilometers in diameter. The reason: the Spitzer Space Telescope had failed to detect its heat. This meant the new world was probably smaller than the Moon, whose diameter is 3,475 kilometers. (Pluto, for comparison, is about 2,300 kilometers across.)

However, the Spitzer observations were incorrect and place NO size constraint on the object:

Thus, the new object could be larger than the Moon--possibly much larger.

Didn 't the discoverer have a chart on his website that showed if the object was comparable to Pluto, its brightness would place its size just about 1.25 times larger, is all?

Yes, if the new world is as reflective as Pluto (60% reflective), then its diameter is 1.25 times Pluto's. But Pluto is quite reflective--that's one reason it was found so long ago, before all the other objects in the Edgeworth-Kuiper belt.

If the new object is darker--that is, less reflective--than Pluto, then it's larger. For example, if its reflectivity is 40%, then its diameter is 3,490 kilometers--bigger than the Moon. if its reflectivity is 20%, then its diameter is 4,940 kilometers--bigger than Mercury. If its reflectivity is 10%, then its diameter is 6,990 kilometers--bigger than Mars. And if its reflectivity is 3%--if you're going to dream, dream BIG--then it's bigger than the Earth!

Are you saying it's a lot different than all the other objects?

Interesting find Crimson.

If it turns out to be significantly larger, the controversy as to whether 2003 UB313 is a "true" planet or not will no longer be an issue. I'm looking forward to Brown's followup observations.

Like Crimson said, this object could really be any size (larger than Pluto)...I think the average albedo for a TNO is only 4%.

with regards

__________________
All words, phrases, definitions and theories provided in the above post are, unless otherwise stated, the property of Champion Munch © 2005.

Sign up to sue the Sun

The typical reflectivity of Edgeworth-Kuiper belt objects has recently been revised upward to 12%--but that's still much less than Pluto's reflectivity of 60%.

Why is Pluto so reflective? Crimson guesses it's because
a) Pluto is large enough to have an atmosphere; and
b) Pluto gets close enough to the Sun to give birth to an atmosphere, produced when the Sun's heat vaporizes some of the planet's ices.

Because Pluto has an atmosphere--at least when it comes closest to the Sun--and is large enough to retain that atmosphere, fresh ice condenses on the planet's surface as the planet recedes from the Sun and cools. Fresh ice is highly reflective, accounting for Pluto's high reflectivity of 60%.

Because of its large size, the new object may have an atmosphere, too. But it does not come as close to the Sun as Pluto does--Pluto's perihelion distance is 29 AU, the new object's is 38 AU--so even at its best, the new object may have less of an atmosphere than Pluto. Less atmosphere may mean less fresh ice; less fresh ice may mean a darker surface; and a darker surface means a larger size.

Does that mean that Pluto's albedo would vary quite a bit, depending on where it is in it's orbit?

with regards

__________________
All words, phrases, definitions and theories provided in the above post are, unless otherwise stated, the property of Champion Munch © 2005.

Sign up to sue the Sun

I hope it's at least larger than Mars. Then we'll see what the IAU will do...

__________________
Do not taunt Happy Fun Ball.

Will they wait for the size of this object to be worked out first, before they announce anything? What happens if we discover more UB313-like objects in the upcoming weeks/months...

I'd sure like it to be that big, don't think it will be though.

with regards

__________________
All words, phrases, definitions and theories provided in the above post are, unless otherwise stated, the property of Champion Munch © 2005.

Sign up to sue the Sun

The highly elliptic orbit of Sedna can be explained by the presence of an Earth-sized planet in the Kuiper Belt. Another explanation for the strange orbit is the influence by a nearby-passing star

Some of the brighter KBOs are much brigher than 12% -- for example, Ixion which was originally thought to be one of the largest (well, it still is, but not among the very largest), may have a reflectivity of 50%.

And still, some are dark. KBOs seem to be much more diverse group than originally thought.

__________________
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

Yup. As Pluto approached the Sun, it darkened--its reflectivity (or albedo) went down.

Not to mention that Pluto has one of the most varied surface albedo in the Solar system.

__________________
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

Cool.

with regards

__________________
All words, phrases, definitions and theories provided in the above post are, unless otherwise stated, the property of Champion Munch © 2005.

Sign up to sue the Sun

They still wouldn't call it a planet. (Just to be difficult) There must be some NCAA folks on that board.

Nemesis?