The Nine Planets 'Solar System Tour'

Devantè · 2006-08-05 05:32:37

http://www.nineplanets.org/

I found this site last year, while googling for some information on Phobos (one of Mars' moons). I think it is a very valuable source of information, and is good when researching something you need about science (planets). Some facts that have been newly updated, and some new pictures are the Sun are being reguarly updated and replaced with new ones (or so I have seen and been told). Very good source of information, and easy-to-remember URL, which is a good thing (like NASA's website).

MathsIsFun · 2006-08-05 10:52:53

Great site, Devanté. Luckily the tenth planet is debateable: http://www.gps.caltech.edu/~mbrown/planetlila/

Devantè · 2006-08-05 18:45:44

Very interesting find, MathsIsFun. I've never seen a picture of something in space so blurry, though. It's orbit looks pretty impressive - According to their information, it has an orbit that is the furthest away from all the planets! O_o

luca-deltodesco · 2006-08-06 05:13:59

the only problem is there are 10 actual planets, and if anything, pluto shouldnt be named a planet because of its size

Kurre · 2006-08-19 03:30:24

wonderful site Devanté, thanks. Awesome!

mikau · 2006-08-25 13:58:40

um.... I have nothing to say.

Last edited by mikau (2006-08-25 14:26:18)

Zhylliolom · 2006-08-25 14:23:38

Darn you Mikau, I just thought about posting that here. You've ruined my night and potentially my life.

mikau · 2006-08-25 14:26:36

what did I say? I didn't say anything! ;-)

Zhylliolom · 2006-08-25 15:44:30

Sorry, my recent solution of a long-standing problem of functional analysis has dazed me in such a manner that I experience hallucinations.

You kind folks should check out this article, which contains information nobody here has heard about yet, especially Mikau:

http://edition.cnn.com/2006/TECH/space/ … index.html

Last edited by Zhylliolom (2006-08-25 17:18:21)

mikau · 2006-08-25 17:17:54

hahaha....

Devantè · 2006-08-25 18:17:02

I saw the exact thing on CNN yesterday...but still, nice read.

Similar to the article 'Definition of a Planet Debatable'.

George,Y · 2006-10-01 01:16:29

Poor Pluto! He no longer has a name!!

Toast · 2006-10-08 21:58:24

A planet should be something large enough to be round, small enough to not combust, and orbit around a star... hmmm. It sounds good enough to me, and therefore we have 30+ planets in our solar system.

Devantè · 2006-10-09 00:11:50

The definition of a planet is still debateable.

Monox D. I-Fly · 2019-11-29 20:05:23

Devantè wrote:

The definition of a planet is still debateable.

And now what defines as a planet?

Jai Ganesh · 2019-12-01 16:16:14

Monox D. I-Fly wrote:

Devantè wrote:
The definition of a planet is still debateable.
And now what defines as a planet?

The IAU defines a true planet as a body that circles the sun without being some other object's satellite; is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a star); and has "cleared its neighborhood" of most other orbiting bodies. Yeah, it's a mouthful.

But that restrictive definition helped isolate what should and should not be considered a planet — a problem that arose as astronomers discovered more and more planet-like objects in the solar system. Pluto was among the bodies that didn't make the cut and was re-classified as a dwarf planet.

The problem with Pluto, aside from its small size and offbeat orbit, is that it doesn't clear its neighborhood of debris — it shares its space with lots of other objects in the Kuiper Belt. Still, the demotion of Pluto remains controversial.

The IAU planet definition also put other small, round worlds into the dwarf planet category, including the Kuiper Belt objects Eris, Haumea and Makemake.

Ceres, a round object in the Asteroid Belt between Mars and Jupiter, also got the boot. Ceres was considered a planet when it was discovered in 1801, but it was later deemed to be an asteroid. That still didn't quite fit because it was so much larger (and rounder) than the other asteroids. Astronomers instead deemed it a dwarf planet in 2006, although some astronomers like to consider Ceres as a 10th planet (not to be confused with Nibiru or Planet X).

(IAU is International Astronomical Union.)

Planets, Dwarf Planets and Small Solar System Bodies: Questions and Answers

Q: What is the origin of the word planet?
A: The word planet comes from the Greek word for "wanderer", meaning that planets were originally defined as objects that moved in the night sky with respect to the background of fixed stars.

Q: Why is there a need for a new definition for the word planet?
A: Modern science provides much more information than the simple fact that objects orbiting the Sun appear to move with respect to the background of fixed stars. For example, recent new discoveries have been made of objects in the outer regions of our Solar System that have sizes comparable with and larger than Pluto. Historically Pluto has been recognised as the ninth planet. Thus these discoveries have rightfully called into question whether or not the newly found Trans-Neptunian Objects should also be considered as new planets.

Q: How did astronomers reach a consensus for a new definition of planet?
A: The world's astronomers, under the auspices of the International Astronomical Union, deliberated on a new definition for the word planet for nearly two years. The results of these deliberations were channelled to a Planet Definition Committee and ultimately proposed to the IAU General Assembly. Continued evolution of the definition through debate and further discussion allowed a final consensus and vote.

Q: What new terms are used in the official IAU definition?
A: There are three new terms adopted as official definitions by the IAU. The terms are: planet, dwarf planet and small Solar System body.

Q: In plain language, what is the new definition of planet?
A: A planet is an object in orbit around the Sun that is large enough (massive enough) to have its self-gravity pull itself into a round (or near-spherical) shape. In addition a planet orbits in a clear path around the Sun. If any object ventures near the orbit of a planet, it will either collide with the planet, and thereby be accreted, or be ejected into another orbit.

Q: What is the exact wording of the official IAU proposed definition of planet?
A: A planet 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.

Q: Does a body have to be perfectly spherical to be called a planet?
A: No. For example, the rotation of a body can slightly distort the shape so that it is not perfectly spherical. Earth, for example, has a slightly greater diameter measured at the equator than measured at the poles.

Q: Based on this new definition, how many planets are there in our Solar System?
A: There are eight planets in our Solar System; Mercury, Venus, Earth,Mars, Jupiter, Saturn, Uranus, Neptune. Mnemonic: *My Very Educated Mother Just Served Us Nachos.

Q: Is that all, only eight planets?
A: No. In addition to the eight planets, there are also five known dwarf planets. Many more dwarf planets are likely to be discovered soon.

Q: What is a dwarf planet?
A: A dwarf planet is an object in orbit around the Sun that is large enough (massive enough) to have its own gravity pull itself into a round (or nearly round) shape. Generally, a dwarf planet is smaller than Mercury. A dwarf planet may also orbit in a zone that has many other objects in it. For example, an orbit within the asteroid belt is in a zone with lots of other objects.

Q: How many dwarf planets are there?
A: Currently there are five objects accepted as dwarf planets. Ceres, Pluto, Eris, Makemake and Haumea.

Q: What is Ceres?
A: Ceres is (or now we can say it was) the largest asteroid, about 1000 km across, orbiting in the asteroid belt between Mars and Jupiter. Ceres now qualifies as a dwarf planet because it is now known to be large enough (massive enough) to have self-gravity pulling itself into a nearly round shape. (Thomas, 2005) Ceres orbits within the asteroid belt and is an example of the case of an object that does not orbit in a clear path. There are many other asteroids that can come close to the orbital path of Ceres.

Q: Didn't Ceres used to be called an asteroid or minor planet?
A: Historically, Ceres was called a planet when it was first discovered in 1801, orbiting in what is known as the asteroid belt between Mars and Jupiter. In the 19th century astronomers could not resolve the size and shape of Ceres, and because numerous other bodies were discovered in the same region, Ceres lost its planetary status. For more than a century, Ceres has been referred to as an asteroid or minor planet.

Q: Why is Pluto now called a dwarf planet?
A: Pluto now falls into the dwarf planet category on account of its size and the fact that it resides within a zone of other similarly-sized objects known as the transneptunian region.

Q: Is Pluto's satellite Charon a dwarf planet?
A: For now, Charon is considered just to be Pluto's satellite. The idea that Charon might qualify to be called a dwarf planet in its own right may be considered later. Charon may receive consideration because Pluto and Charon are comparable in size and orbit each other, rather than just being a satellite orbiting a planet. Most important for Charon's case as a dwarf planet is that the centre of gravity about which Charon orbits is not inside of the system primary, Pluto. Instead this centre of gravity, called the barycentre, resides in free space between Pluto and Charon.

Q: Jupiter and Saturn, for example, have large spherical satellites in orbit around them. Are these large spherical satellites now to be called dwarf planets?
A: No. All of the large satellites of Jupiter (for example, Europa) and Saturn (for example, Titan) orbit around a common centre of gravity (called the "barycentre") that is deep inside of their massive planet. Regardless of the large size and shapes of these orbiting bodies, the location of the barycentre inside the massive planet is what defines large orbiting bodies such as Europa, Titan, etc. to be satellites rather than planets. [Actually, there has been no official recognition that the location of the barycenter is involved with the definition of a satellite.]

Q: What was 2003 UB313?
A: 2003 UB313 was a provisional name given to a large object discovered in 2003 that resides in an orbit around the Sun beyond Neptune. It is now called Eris and is recognised as a dwarf planet.

Q: Why is Eris a dwarf planet?
A: Hubble Space Telescope images have resolved the size of Eris showing it to be as large as, or larger than Pluto, Brown (2006).More important, Eris was found to have a satellite, which was later named Dysnomia, after the Greek demon of lawlessness who was Eris' daughter. In 2007, the mass of Eris was determined to be (1.66 ± 0.02)×10^22 kg, 27% greater than Pluto, based on observations of the orbit of Dysnomia. Eris also orbits within the transneptunian region - a region that has not been cleared out. Therefore Eris is a dwarf planet.

Q: What is an object called that is too small to be either a planet or dwarf planet?
A: All objects that orbit the Sun that are too small (not massive enough) for their own gravity to pull them into a nearly spherical shape are now defined as being small Solar System bodies. This class currently includes most of the Solar System asteroids, near-Earth objects (NEOs), Mars and Jupiter Trojan asteroids, most Centaurs, most Trans-Neptunian Objects (TNOs) and comets.

Q: What is a small Solar System body?
A: The term "small Solar System body" is a new IAU definition to encompass all objects orbiting the Sun that are too small (not sufficiently massive) to satisfy the definition of planet or dwarf planet.

Q: Is the term minor planet still to be used?
A: The term "minor planet" may still be used. But generally the term small Solar System body will be preferred.

Q: How will an official decision be reached on whether or not to call a newly discovered object a planet, dwarf planet, or a Solar System body?
A: The decision on how to classify newly discovered objects will be made by a review committee within the IAU. The review process will be an evaluation, based on the best available data, of whether or not the physical properties of the object satisfy the definitions. It is likely that for many objects, several years may be required to gather sufficient data.

Q: Are there additional planet candidates currently being considered?
A: No. None appear likely in our Solar System. But there are planet discoveries galore around other stars.

Q: Are there additional dwarf planet candidates currently being considered?
A: Yes. Some of the largest asteroids may be candidates for dwarf planet status and some additional dwarf planet candidates beyond Neptune will soon be considered.

Q: When will additional new dwarf planets likely be announced?
A: Probably within the next few years.

Q: How many more new dwarf planets are there likely to be?
A: There may be dozens or perhaps even more than a hundred waiting to be discovered.

Q: What are plutoids?
A: Plutoids are celestial bodies in orbit around the Sun at a semimajor axis greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit. Satellites of plutoids are not plutoids themselves, even if they are massive enough that their shape is dictated by self-gravity. The two known and named plutoids are Pluto and Eris. It is expected that more plutoids will be named as science progresses and new discoveries are made. (Read more)

Q: Can a satellite orbiting a plutoid be a plutoid too?
A: No, according to the IAU Resolution B5 a dwarf planet can not be a satellite, even if they are massive enough that their shape is dictated by self-gravity.

Math Is Fun Forum

#1 2006-08-05 05:32:37

The Nine Planets 'Solar System Tour'

#2 2006-08-05 10:52:53

Re: The Nine Planets 'Solar System Tour'

#3 2006-08-05 18:45:44

Re: The Nine Planets 'Solar System Tour'

#4 2006-08-06 05:13:59

Re: The Nine Planets 'Solar System Tour'

#5 2006-08-19 03:30:24

Re: The Nine Planets 'Solar System Tour'

#6 2006-08-25 13:58:40

Re: The Nine Planets 'Solar System Tour'

#7 2006-08-25 14:23:38

Re: The Nine Planets 'Solar System Tour'

#8 2006-08-25 14:26:36

Re: The Nine Planets 'Solar System Tour'

#9 2006-08-25 15:44:30

Re: The Nine Planets 'Solar System Tour'

#10 2006-08-25 17:17:54

Re: The Nine Planets 'Solar System Tour'

#11 2006-08-25 18:17:02

Re: The Nine Planets 'Solar System Tour'

#12 2006-10-01 01:16:29

Re: The Nine Planets 'Solar System Tour'

#13 2006-10-08 21:58:24

Re: The Nine Planets 'Solar System Tour'

#14 2006-10-09 00:11:50

Re: The Nine Planets 'Solar System Tour'

#15 2019-11-29 20:05:23

Re: The Nine Planets 'Solar System Tour'

#16 2019-12-01 16:16:14

Re: The Nine Planets 'Solar System Tour'

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