How many planets are in our solar system?

[ICER]

Well, the answer just may surprise you. check out this artical I found

http://www.gemini.edu/index.php?opti...sk=view&id=142

[Willravel]

Pluto isn't a planet. I think we have 9 in our solar system, barring some gravitational oddity.

Edit: Pluto isn't a planet in my opinion because it is smaller than our moon which is not catagorized as a planet. If the term 'planet' verses the term 'moon' or 'asteroid' are dependant on size, then pluto would be a moon or asteroid. If, however, the terms 'planet', 'moon', and 'asteroid' also take into acocunt location, revolution, and orbit, then it's possible that we have hundreds of planets. Kinda makes me think....

[sapiens]

Originally Posted by willravel

Pluto isn't a planet. I think we have 9 in our solar system, barring some gravitational oddity.

I thought that this was a matter of debate. Also, I've read that whether or not an object is a planet is more of a political distinction than a scientific one. Members of the International Astronomical Union designate which astronomical objects qualify as planets and which do not. The line which distinguishes a planet from an asteroid, etc. seems arbitrary.

[Bill O'Rights]

Oh, great. So now I have to learn a whole new mnemonic to remember the order of planets? My Very Excelent Memory Just Served Up Nine Planets...well hell, what can you use for 2003 UB313?

[Rekna]

the difference between a moon and a planet has to do with what it orbits around in combination with it's size. pluto is to big for an asteroid and it doesn't orbit around a planet so it isn't a moon.

[Willravel]

My Very Eager Mother Just Sold Us New Playstation 2s

[Willravel]

Haha!! You're right!! I stand corrected.

Moon - any natural satellite orbiting a major planet. Pluto is not a moon.

Asteroid also called minor planet, or planetoid, any of a host of small rocky bodies, about 1,000 km or less in diameter, that orbit the Sun primarily between the orbits of Mars and Jupiter. It is because of their small size and large numbers relative to the nine major planets that asteroids are also called minor planets.

Since Pluto has a diameter of 2,360 km, it is a planet!!!

[Redlemon]

From the bottom of the link in the original post:

What in the World is a Planet Anyway?

With the recent discoveries of Sedna and now 2003 UB 313 at distances from the Sun well beyond those of the “traditional” planets that we all learned in elementary school, the question: “What is a planet?” has taken on added significance.

There is a diverse range of objects populating our solar system, and many objects are clearly not planets. These include: comets, asteroids (sometimes called minor planets), satellites, dust grains, charged particles, planetesimals and of course the sun. But what is it that makes a planet a planet?

Some have argued that Pluto does not fit the bill as a planet given its small size and highly eccentric, greatly inclined orbit.. However, it is countered that Pluto has a satellite like other planets, it orbits the sun like other planets and it is made up of planet-like material. Therefore, it is a planet. So where does that leave objects like 2003 UB 313?

Many of the same arguments that have been used to “demote” Pluto from planet status are also being used on 2003 UB 313 (as well as Sedna and similar objects), even though these arguments have not made much progress and often just cloud the issue with semantics.

Many of the same arguments that have been used to “demote” Pluto from planet status are also being used on 2003 UB 313 (as well as Sedna and similar objects that now number four).

The main differences between 2003 UB 313 and Pluto are: it is probably a bit bigger than Pluto, it is located in the Kuiper Belt about 3-times further from the sun than Pluto, and the inclination of its orbit is about 44° with respect to the plane of the solar system. (Note: 44° is a very high inclination, the second highest is of Pluto at 17°. One of the reasons UB 313 has not been discovered until now is because it was not believed that Kuiper Belt objects could have such a large inclination to the ecliptic.)

Given the fact that there is not a consensus on Pluto’s status, it is unlikely that there will ever be agreement on 2003 UB 313 or other objects like it. Suffice it to say that we are learning a lot more about our solar system and there will probably be more surprises as we explore to even greater depths.

[florida0214]

I can answer the question : "how many planets are in our solar system" without even reading the article.
Answer: Who cares. We are in a solar systemthere are planets on it. I am pretty sure that we live on one. How cool is that!

[ObieX]

As a side note: I would like to make a small addition to this post.

2 new moons possibly discovered around pluto!

http://www.nasa.gov/vision/universe/...ble_pluto.html

http://www.nasa.gov/images/content/1...luto1_full.jpg
The artist's concept above shows the Pluto system from the surface of one of the candidate moons. The other members of the Pluto system are just above the moon's surface. Pluto is the large disk at center, right. Charon, the system's only confirmed moon, is the smaller disk to the right of Pluto. The other candidate moon is the bright dot on Pluto's far left. Click image for full resolution.

Credit: NASA, ESA and G. Bacon (STScI)

http://www.nasa.gov/images/content/1...luto2_full.jpg
The Hubble Space Telescope images above, taken by the Advanced Camera for Surveys, reveal Pluto, its large moon Charon, and the planet's two new candidate satellites. Between May 15 and May 18, 2005, Charon, and the potential moons, provisionally designated P1 and P2, all appear to rotate counterclockwise around Pluto.

P1 and P2 move less than Charon because they are farther from Pluto, and therefore would be orbiting at slower speeds. P1 and P2 are thousands of times less bright than Pluto and Charon. The enhanced-color images of Pluto (the brightest object) and Charon (to the right of Pluto) were constructed by combining short exposure images. The images of the new satellites were made from longer exposures. Click image for full resolution.

Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the Hubble Space Telescope Pluto Companion Search Team


In the short-exposure image (above left), taken June 11, 2002, the candidate moons cannot be seen. They do, however, appear in the middle and right-hand images. Longer exposure times were used to take these images. Pluto and Charon are overexposed in these images, causing the bright streaks or "blooms" that emerge vertically from them.

The candidate moons are not overexposed because they are thousands of times less bright than Pluto and Charon. In these unprocessed images, various optical artifacts of the Advanced Camera for Surveys system are visible, such as the radial spokes of light caused by the telescope's optics.

Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the Hubble Space Telescope Pluto Companion Search Team

[ObieX]

To expand, once again, on this thread: here's some more info about other planetoids that have been discovered so far.

http://www.spacetoday.org/SolSys/KuiperBelt/Quaoar.html

Here's a list from the site of a couple that are note worthy, and compairs their sizes.

Sizes Compared
In recent years, astronomers have found several big objects beyond Neptune. Here are the approximate diameters of some discovered objects:
Object
Name Year Discovered Diameter in Miles
Sedna 2004 995
Orcus 2004 995
Quaoar 2002 745
Ixion 2001 660
Varuna 2000 560
Pluto 1930 1429
Earth 7,926

[ObieX]

http://www.spacedaily.com/news/kuiper-05e.html

When Copernicus Smiled
by S. Alan Stern
Boulder CO (SPX) Sep 06, 2005


This chart shows the various sizes of major Kuiper objects discovered to date, and compared to our own moon. Image courtesy: Sky & Telescope.

Planetary science is awakening to the realization that our solar system contains many more planets than any 20th century textbook ever envisioned. It's not your father's solar system.

A real revolution is afoot in planetary science. The first shot was fired in 1930, with the discovery of Pluto, but almost no one realized its import. The second and third shots came in the late 1970s, with the discovery of distant objects called Chiron and Charon, but again, few recognized what they would portend.

Rapid-fire volleys began in the 1990s, as myriad discoveries of icy bodies 100km to well over 1000 km across occurred in the Kuiper Belt, just beyond Neptune, became an observational reality. But it was only this year, with the recently announced discovery of 2003 UB313—a world larger than Pluto—that we have heard the equivalent of the American Revolution's "shot heard round the world."

When I was a boy in the 1960s, in college in the late 1970s, and in graduate school in the 1980s, we were taught that our solar system contains four rocky planets on the inside, four giant planets on the outside, and one spit of a planetary misfit called Pluto, moving in a markedly elliptical, and oddly inclined orbit beyond Neptune. Like many people, I recall thinking: What an odd bird that lone Pluto is.

Today, however, we see a very different picture of our home solar system is emerging, one which reveals Pluto in context—as a nearby example representing what is almost certainly the most populous class of planet in our solar system—the "ice dwarfs."

Consider that less than 2% of the Kuiper Belt has been thoroughly catalogued, yet over a thousand plus rogue worlds and worldlets have already been spotted there. And among just those bodies catalogued to date, we know that half a dozen (like Sedna and Quaoar) already rival—and in the case of the just discovered 2003 UB313—exceed Pluto's size. Moreover, most of these new worlds follow orbits that are as cockeyed as Pluto's—some even more so.

Now we can see just how naive our 20th century perspectives were: Pluto is no misfit. Instead, once the advance of technology allowed us to probe deeply enough, it is becoming clear that Pluto was the advance harbinger of a populous new region of the solar system lying beyond the giant planets.

Modern simulations of planetary formation, performed by different research groups around the world, led to broad agreement that in the process of forming the giant planets, some hundreds to thousands of smaller worlds, ranging from a goodly fraction of Pluto's size to at least Earth's size, were also formed.

Most of these bodies were dwarf planets, like Pluto, with steeply declining populations at larger and larger sizes, so that only a few or few tens of bodies Earth's size were formed.

These simulations also show that most of these bodies were ejected from the giant planets region to more much more distant orbits as Jupiter, Saturn, Uranus, and Neptune, neared their current sizes and gravitationally cleared out their formation zones, some 4+ billion years ago.

Importantly, these numerical models are supported by some solid forensic clues that are scattered about the outer solar system, and which lead us to similar conclusions: One such clue is the fact that Pluto's moon, Charon (itself half of Pluto's size) seems to have been formed by a giant impact with a body nearly as large as Pluto itself.

What is most important in this finding is that, in order to make such a collision probable, there must have been hundreds or more 1000-km diameter bodies orbiting in the ancient outer solar system. A second clue comes in the form of Triton, a 2700 km diameter moon, which circles Neptune on a retrograde orbit that is the hallmark of gravitational capture from a previous orbit around the Sun. Triton is compositionally much like Pluto, but a tad larger.

Apparently, it is one of the "many Plutos" that once formed, and it seems to have escaped ejection by becoming caught in a long-lasting orbit around Neptune. Yet another clue comes from the polar tilts or Uranus (98 degrees) and Neptune (30 degrees).

The only viable mechanism known to be able to generate such extreme tilting of these gargantuan (15 Earth mass-class) planets, are off-center collisions with bodies of one to several Earth masses. Crucially, calculations also reveal that in order for both Uranus and Neptune to have had a high probability of suffering such collisions, as many as a few dozen such Earth-mass objects may have once orbited in their region of the solar system.

As a result of the modeling capability that modern computers give us, combined with the forensic observational clues just discussed, and now the discoveries of rivals and even successors to Pluto's throne, we are slowly but surely coming to a simultaneously jarring and exciting new conclusion: that our solar system formed not just the nine planets we were taught to name in school, but many dozens, if not hundreds of others as well!

A revolutionary aspect of this emerging, new paradigm is the dawning realization that the long-known eight rocky and giant planets, Mercury through Neptune, now seem to be the misfits.

Indeed, from today's 21st century perspective, the solar system seems likely to be dominated by a huge population of rock and ice planets ranging from dwarf sizes like Pluto to perhaps super-Earth's. Most of these new worlds are expected to follow elliptical, highly-inclined orbits, like those of Pluto, Quaoar, Sedna, and UB313.

Further still, of all the planets now expected to orbit within our sun Sol's grasp, most orbit between ten and a thousand times farther than do any of the planets we were taught about in school. It's not at all your father's solar system.

Less than two centuries ago it was discovered that all the stars one can see by eye, and their innumerable brethren seen by telescope, are distant Suns, with numbers too great to count. Similarly, it was just under a century ago that our galaxy, the Milky Way, was realized to be but one of literally billions of galaxies.

Both of these realizations, like the 16th century realization that the Sun (not Earth!) is the center of our solar system, jarred perceptions and changed textbooks in revolutionary ways.

Just as jarring to us now is the newly emerging view that our solar system made, and is still littered with, very many distant planets, most of which are nothing like the familiar planets that orbit close to the Sun, like Earth.

In a real sense, we are seeing a new chapter unfold in the revolution that Copernicus wrought when he displaced the Earth from the center of everything. Another slice of humble pie, anyone?

Alan Stern is a planetary scientist at the Southwest Research Institute and the Principal Investigator of NASA's New Horizons mission to Pluto and the Kuiper Belt.

[proplyd]

It has been a while since anyone posted here. It has been since before the International Astronomy Union demoted Pluto to a dwarf planet. If this one goes though, it will be my first.

They unintentionally demoted another planet when they got Pluto, the smallest of the traditional nine planets. They also demoted Jupiter, the largest of them.

The new definition of a planet requires that it orbit the Sun. Jupiter does not, technically. The center of mass between Jupiter and the Sun, their barycenter, lies a whisker outside the surface of the Sun. Technically, Jupiter and the Sun orbit each other. Jupiter does not orbit the Sun, and therefore is not a planet.

[Redlemon]

Originally Posted by proplyd

It has been a while since anyone posted here. It has been since before the International Astronomy Union demoted Pluto to a dwarf planet. If this one goes though, it will be my first.

They unintentionally demoted another planet when they got Pluto, the smallest of the traditional nine planets. They also demoted Jupiter, the largest of them.

The new definition of a planet requires that it orbit the Sun. Jupiter does not, technically. The center of mass between Jupiter and the Sun, their barycenter, lies a whisker outside the surface of the Sun. Technically, Jupiter and the Sun orbit each other. Jupiter does not orbit the Sun, and therefore is not a planet.

That, sir, is one WICKED first post. Welcome.

[Baraka_Guru]

"RESOLUTION 5A ... (1) A planet1 is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit."

Earth has near Earth objects (NEOs) and Jupiter has Trojans, which means neither of them have "cleared the neighbourhood around its orbit."

Earth and Jupiter Join Pluto as Non-Planets? | NASA Watch

But I'm no astronomer, so I can't validate this claim.

Originally Posted by Redlemon

That, sir, is one WICKED first post. Welcome.

Indeed.

[mixedsubstance]

All i can say is- Pluto has been denounced as a planet. But then scientists discovered a new 'planet'= Planet X. I think all of this is f'd up. Leave the planets as they were.

[yellowmac]

Originally Posted by mixedsubstance

All i can say is- Pluto has been denounced as a planet. But then scientists discovered a new 'planet'= Planet X. I think all of this is f'd up. Leave the planets as they were.

Um, what?

[mixedsubstance]

Originally Posted by yellowmac

Um, what?

Explain your question....

[yellowmac]

Originally Posted by mixedsubstance

Explain your question....

Could you elaborate on your Planet X claim from scientists? 'Cause that's news to me.

[Catdaddy33]

They discoved Sedna which is part of the reason that Pluto got the demotion.

SPACE.com -- Weird Object Beyond Pluto Gets Stranger

They still think there is a larger body Planet X that orbits well beyond Pluto.

SPACE.com -- Large 'Planet X' May Lurk Beyond Pluto

[yellowmac]

Originally Posted by Catdaddy33

They discoved Sedna which is part of the reason that Pluto got the demotion.

SPACE.com -- Weird Object Beyond Pluto Gets Stranger

They still think there is a larger body Planet X that orbits well beyond Pluto.

SPACE.com -- Large 'Planet X' May Lurk Beyond Pluto

Ok, sure. But Sedna and the other KBOs that have been discovered in the past few years aren't the elusive Planet X that people have been searching for. I think it's doubtful that a large "Planet X" (i.e. Neptune mass) exists, because it probably would have perturbed the orbits of Kuiper Belt and Oort Cloud objects to adversely affect the inner and outer solar system.

[Catdaddy33]

I agree, I was just reporting out what "they" are looking for. I would think that something that big would have already been found.

[yellowmac]

Originally Posted by Catdaddy33

I agree, I was just reporting out what "they" are looking for. I would think that something that big would have already been found.

Probably, but through indirect means. If something that big but that far away exists, it might still be too faint to be detected even by today's sophisticated equipment. But this is just rampant speculation on my part.

[Sun Tzu]

Originally Posted by yellowmac

Ok, sure. But Sedna and the other KBOs that have been discovered in the past few years aren't the elusive Planet X that people have been searching for. I think it's doubtful that a large "Planet X" (i.e. Neptune mass) exists, because it probably would have perturbed the orbits of Kuiper Belt and Oort Cloud objects to adversely affect the inner and outer solar system.

From the research I have done there is debate as to whether or not something is pulling on the orbit of pluto that has to be significantly larger than the recent pluto like planetoid. To me I dont understand how there can be debate with the present technology we have even from a visual telescope; numbers dont lie.

I have also heard speculation that planet X "Nibiru" is actually a brown dwarf on its own 36,000 year orbit because this was supposedly a binary solar system. Again there is not much of a foundation to support that either.

The one intersting thing though which finds its way into this discussion is the ancient Sumerians believed there were 10 planets.

[passthru]

Originally Posted by Sun Tzu

The one intersting thing though which finds its way into this discussion is the ancient Sumerians believed there were 10 planets.

I count twelve. There are nine with a similar orbit and three others off to the right. One could be part of the middle persons headdress, another is barely peeking out of the shadow.

[Sun Tzu]

Originally Posted by passthru

I count twelve. There are nine with a similar orbit and three others off to the right. One could be part of the middle persons headdress, another is barely peeking out of the shadow.

They are counting the moon as one. The other is where it gets shady. They believed in Nibiru. As it stands there is no substantial proof of it, and we are still here. If it were going to come around the "2012" time we would have seen it by now.

[alexruseell]

Originally Posted by Willravel

Pluto isn't a planet. I think we have 9 in our solar system, barring some gravitational oddity.

Edit: Pluto isn't a planet in my opinion because it is smaller than our moon which is not catagorized as a planet. If the term 'planet' verses the term 'moon' or 'asteroid' are dependant on size, then pluto would be a moon or asteroid. If, however, the terms 'planet', 'moon', and 'asteroid' also take into acocunt location, revolution, and orbit, then it's possible that we have hundreds of planets. Kinda makes me think....

I little bit agree with you.

But, then which is the planet of pluto?