Astronomers discover "10th planet"

http://skyandtelescope.com/news/article_1560_1.asp

This is very confusing, this is not the same body of my other thread. It's 3000 km across (Pluto is 2250 km)

"The object, designated 2003 UB313, is currently 97 astronomical units (Earth-Sun distances) away — more than twice Pluto's average distance from the Sun. It is a scattered-disk object, meaning that at some point in its history Neptune likely flung it into its highly inclined (44°) orbit. It's currently glowing at magnitude 18.9 in the constellation Cetus"

"A second big Kuiper Belt discovery also made news today: 2003 EL61. That body, located about 52 a.u. away, was discovered by Brown and his team and independently by astronomers at the Sierra Nevada Observatory in Spain. It appears to be the third-largest Kuiper Belt object known to date, with about 70 percent of Pluto's diameter —"

 

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mmm, interesting

I have an old thought that Pluto should not be called a planet at all and all other objects further than Neptune if they are not equal or larger in diameter to it.

Of course this leads to the age old discussion - what is a planet?

 

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From what I understand, in the "Solar nebula theory", the objects of the Kuiper belt are planetesimals that didn't collide to form planets, so given that Pluto is very likely a body captured from the Kuiper belt, I think that is wrong to call it a planet. This new object discovered shouldn't be called a planet. A definition of planet should be: a body formed through the process of aggregation of planetesimals, and orbiting a star (or more than one)

 

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So what would be the planets that have been thrown out of their star system? Do they become asteroids?
I think that your definition is sound, it just needs a little edit -> a body that has been formed through the process of aggregation of planetesimals while orbiting a star (or more than one)

???

 

Hum,
How weird was that,
You wait around for ages and two come at the same time…

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They have proposed a name for the `planet` -<b> lila </b>- to the IAU, and will announce it when that name is accepted.

The word on the street is that <b>Lila</b> is the name of Mike Brown's newborn daughter

 

umm....sorry for a basic question; but by defintion a planet is to be revolving around a star necessary? in that sense since most of the systems, except ours are twin star systems so are these stars revolving around giants also planets? material wise there's no distinction right? since there are types of planets jupiter for example is a sort of gaseous planet, then there are solid planets like ours....so what exactly is a planet and how would you classify a body as a planet?

 

I believe there is a seperate discussion here at sciforums, Zion. There were many points made. Try the search.

p.s. I'd be careful with that most. Most of what we have found maybe. Maybe it's easier to notice a planet in a twin star system.

 

Agreed. Pluto is not a planet at all, but an orbitting asteroid.

 

the moon is a planet like the earth, just that it's even deader.

if a planet is thrown out from the solar system it becomes a planet that has been thrown out from the solar system.

maybe we shouldn't use the definition planet, but instead just use the definition satellites when we talk about satellites orbiting the sun.

like satellites that orbit the nucleus of an atom. the electrons are the same thing as protons except under different circumstances.

so... it's unnecessary to use the word planet.

 

The moon is not a planet, is just a chunk of material kicked off the Earth 4'5 billions of years ago by a planetesimal (Giant impact theory). It was not formed as the rest of planets, so it's not a planet--it's a satellite

 

Hum,
Perhaps we could qualify it by saying that they are Kuiper belt planets…

As such the three big discoveries announced this week could all be called Kuiper belt planets…

<b>Round up:</b>
At magnitude 17.5, <b>2003 EL61</b> orbits 51 AU from the Sun. It has a diameter about 0.70 Pluto diameters but elongated. Its mass is 0.30 the mass of Pluto. The Keck LGSAO system delivered images with a typical resolution of 0.06 arc seconds at 2.1 microns wavelength. Observations made during 5 commissioning nights between 26 January and 30 June 2005 allowed the researchers to derive the following orbital solution for the delta K=3.8 magnitude satellite with respect to the primary:
<b>a</b>=49100±400 km
<b>P</b>=49.05±0.03 days
<b>e</b>=0.048±0.002.
This implies a total mass of the system of 3.9±0.1 x 1021 kg, or 30.2±0.8% the mass of Pluto.
The orbit is steeply inclined at 28 degrees to the solar plane. The Period is 285 years. It has a moon 1% of primary mass in 49-day orbit.
Discoverer: Ortiz; Moon discovered by Mike Brown who had also discovered the primary but did not announce it first.

At magnitude 18.9, <b>2003 UB313</b> orbits 97 AU from the Sun. It is twice as big as Pluto. The orbit is inclined at 44 degrees to the solar plane. The period is 557 years. It is a very bright object, Like Pluto; the object's surface is believed to be predominantly methane. At its present distance the surface is chilled to just 30°C above absolute zero.
The object was discovered by Mike Brown.
News of the discovery was announced earlier than expected after hackers broke into Brown's website and stole news of it…(<i>Ed</i>- according to reports)
That led him to announce the planet and a third object - temporarily designated 2005 FY9 by the Minor Planet Centre.

<b>2005 FY9</b> orbits 52 AU from the Sun.
It is estimated to have an absolute magnitude of -0.4; with a Pluto-like albedo of 0.6 this would give it a diameter that is slightly less than the diameter of Pluto, about 1990km. Its orbit is inclined at 29 degrees to the solar plane, and has a Period of 308 years.
It was also discovered by Mike Brown.

Heres a long list of other trans-neptunian objects… (187kb)

 

I think that thoes objects which do not have atmosphere should not be called planets, We should draw the lines somewhere.

 

Yeah, I don't particularly understand what constitutes a planet. I thought it was a large body with it's own atmosphere - but some moon's have their own atmosphere.

I think in the end, there are just differently sized, shaped and created objects. Asteroids, comets, planets and moons are the same thing just at different stages. They start as large, atmospheric planets, then become degraded as they slip further away from heat source and become moon.. Then it becomes an asteroid.. and then! it becomes a comet when it's wore down to it's core.

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I'm sure everything I just said sounded stupid to an astronomer. Has anyone ever thought of this before? I really came to this idea after looking at some comets and asteroids.. I still don't see that great a difference.

 

I think tristan can answer the question better,can he not? he's better half of carl IMHO.

 

Currently there is no definate definition for what is and isn't a planet and it continues to be a hotly debated topic.

 

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An artist concept of 2003UB313, the Sun can be seen in the distance

http://www.nasa.gov/vision/universe/solarsystem/newplanet-072905-images.html

 

Hum,
the sun looks (slightly) too big...

Seemingly it can be covered up with the head of a pin, held at arms length, if you were standing on 2003 UB₃₁₃

 

I like the idea of "planetesimal". And I would include pluto and Charon into that category. However, calling pluto (by all accounts a rounded planet-like object with some evidence of an atmoshere (mostly heating and freezing of the nitrogen because of the eccentricity of its orbit) an asteroid is jut not right. An captured asteroid, if you feeling calling something that, would more appropriately be Phobos or Deimos. while were at it, should we stop calling those moons and start calling them asteroids?

Its essentially a matter of semantics at this point. Astronomers arent going to give up and say pluto is a real, genuine, "planet" given the hard facts. On the other hand, popular culture, and more specifically school children, are not going to call the famed 9th planet and favorite "planet" a captured asteroid.

So, let the astronomers dispel the myths in planetariums and lectures (like the other day when people in my planetarium actually believed the north star was the brightest one in the sky), and let the school children and popular culture have what they want. When it comes down to it, what we classify these things for the public isnt going to hinder the science that goes on to discover more.

Later
T

(IMHO, when something looks like a potato or squished egg or some other vegtable, and is flying through space in a highly eccentric orbit... thats an asteroid or otherwise.... if its round, and big enough to be rare, have a smaller eccentricity, then call it a planet. Or if you cant bare, slap it in a new category, the planetesimals.)

 

I'm sure that the designation of planet for Pluto won't hold in the future. It will be called some of these things:

-Trans-Neptunian object: any object in the solar system with all or most of its orbit beyond that of Neptune.

-Plutino: a plutino is a Pluto-like object, insofar as it has the same relative orbit as Pluto

-Minor planet: Minor planet is the official term for asteroids and trans-Neptunian objects.

-Kuiper belt object: An ice-and-rock body that resides in the Kuiper belt

-Captured Kuiper belt object


I personally like the designation of Pluto as a Minor Planet, this way it is related to KBOs and Oort cloud objects, and also to the asteroids of the Asteroid Belt

 

I don't like the term -> Trans-Neptunian object,
because it will then suck if we find something bigger than Neptune out there,
or is it impossible?