Pluto is not worth it.

[moonlord]

I've heard on the TV a few minutes ago that Pluto is no more considered a planet. It's not even considered part of the solar system. So from now on, there are 8 planets orbiting the Sun.

Off-topic: I suggest subscribing to the Softpedia newsletter (softpedia.com). Although most of the entries are IT-related, there are many related to science, in general.

[jinydu]

It's not even considered part of the solar system.

Surely that's an exagerration. Pluto's trajectory is still dominated by the Sun's gravitational field.

[houserichichi]

I agree...but then would Halley's comet part of our solar system too?

Sean Carroll made a very good point that the news about Pluto has been making its rounds much more efficiently and quickly than the news about dark matter, something that actually has importance. And I quote,

the Bullet Cluster data [re: dark matter] have taught us something profound about the constituents and forces of our universe, while the “planet” business has taught us about the vote of a committee on what to call stuff. Why is that?

[Hugh]

It's not even considered part of the solar system.

Surely that's an exagerration. Pluto's trajectory is still dominated by the Sun's gravitational field.

Here is what the Science & Space article at CNN.com said about this:

Much-maligned Pluto doesn't make the grade under the new rules for a planet: "a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit."

Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.

Instead, it will be reclassified in a new category of "dwarf planets," similar to what long have been termed "minor planets." The definition also lays out a third class of lesser objects that orbit the sun -- "small solar system bodies," a term that will apply to numerous asteroids, comets and other natural satellites.

Check out 2003 UB3113 at: http://en.wikipedia.org/wiki/2003_UB313, it's actually bigger than Pluto.

[moonlord]

Softpedia news - 20 aug (link):

Should Pluto be considered a planet? What about "Xena" which is even further away from the Sun but which proved to be even larger than Pluto. The International Astronomical Union debated such issues and tried to come up with a definition of "planet". Insofar, their proposal states that anything which is round and orbits the Sun is a planet.

This allows Pluto to remain a planet but also grants the former asteroid Ceres, which is between Mars and Jupiter, the planetary status. Moreover, astronomers noted that Charon, previously considered Pluto's satellite, is in fact so big compared to Pluto that it doesn't really revolve around Pluto - rather, both Pluto and Charon revolve around their center of mass which is somewhere in space outside Pluto itself. Thus, they want to call Charon a planet too - the Pluto-Charon system becomes a "binary planet".

"Xena", still waiting for an official name, is also labeled a planet. And probably there are many more planets to come... At least if this draft definition gets accepted.

Read the full article here.

However, it seems this has not been accepted.

http://en.wikipedia.org/wiki/Definition_of_planet
http://en.wikipedia.org/wiki/2006_redefinition_of_planet

Like this, there are eight planets and four dwarf planets (Ceres, Pluto, Charon and "Xena").

I believe this is final.

[Nick]

It's not even considered part of the solar system.

Surely that's an exagerration. Pluto's trajectory is still dominated by the Sun's gravitational field.

I heard about this the other day to. Haven't read any articles in detail, though.
It's part of something new called the Kuipper belt; sort of like a second asteroid belt. Apparently, it's not a planet if its own gravity can't make it somewhat round

[houserichichi]

The Kuiper belt is a region of space directly after Neptune which has always included Pluto. Pluto's gravity is enough to make it roughly spherical. In fact, there was another possible planet when they were still deliberating over the definition that looks less spherical than the others in this photograph (top-left). What killed Pluto as a planet is that its orbit brings it back across that of Neptune's rather than off on its own around the sun.

[papernuke]

there are 8 planets orbiting the Sun.

I thought they found like 2 more orbiting the sun.

[houserichichi]

Here's the little picture to help out and tell you who's who in the solar system.

http://apod.nasa.gov/apod/image/0608/planets_iau.jpg

[Hugh]

there are eight planets and four dwarf planets (Ceres, Pluto, Charon and "Xena").

I believe this is final.

"Xena", or 2003 UB3113 now has a new name; Eris, (officially 136199 Eris). See http://www.physorg.com/news77463802.html and http://en.wikipedia.org/wiki/136199_Eris.

[houserichichi]

Three cheers for Eris!!!

[Nick]

Edited the Eris wiki page to read "Kuipper Belt", instead of "Scattered Belt". This is interesting stuff, though. I wonder what we'll find next in our solar system? Think this might be it?

[Hugh]

I wonder what we'll find next in our solar system? Think this might be it?

Nope. There are all kinds of ways that things could be hidden from our present view.

I remember as a kid hearing about various ideas of the time. The Earth's moon always faces the Earth with the same face. People wondered if there was some higher civilization living on "the far side".

Another one was that there was another planet directly opposite the Earth on the other side of the Sun which we never saw because the Sun was in the way. Our probes eventually found that both ideas are false, or so we think with our current technology.

Who knows? With several hundred more years of technological advancement, future humans would be able to hide themselves completely from the technology of today. Who is to say that it is impossible that advanced civilizations aren't already present in our solar system now... even here on Earth?

[papernuke]

I heard on the news yesterday that pluto and that other planet they found were considered dwarf planets, at least better than an asteroid. Also, they named the planet somthing like Eiuion.