Sedna

[Kolano]

http://www.theaustralian.news.com.au/common/story_page/0,5744,8968352%255E29098,00.html

Is there enough info for Sedna to be defined in Celestia yet?

[selden]

I can't find any MPC circular that would seem to correspond to this one.

There were a half-dozen discovered by Kitt Peak a few days ago that seem to have orbits that are about the right size (see MPC Circular #2004-K36) but none of them are bright enough. The brightest has an H value of 5.9, which would imply a diameter less than 500km. (See http://cfa-www.harvard.edu/iau/lists/Sizes.html)

[selden]

I found a mention on the main NASA site. Apparently it was discovered using the Spitzer Space Telescope. No additional information will be available until 1800 U.T, 15 March.

See http://www.nasa.gov/home/hqnews/2004/mar/HQ_n04040_solar_object.html

[galileo]

haul out the "is pluto a planet?" debate cards again.. this one could be the clincher.

how about this for qualification:

1. orbits sun
2. min. radius of 2,000km
3. rocky core? (not sure if this is true for all 4 of the gas giants)

care to expand?

[Art Vandelay]

1) orbits the sun;
2) minimum diameter equal to that of Pluto.

Anybody agree? This way there are still only nine planets, with Pluto being the smallest planet. If this new body falls in this criteria, it will be the tenth planet. It's mainly for sentementality, since Pluto appears to be one of many such bodies at that distance from the Sun. However, if many such bodies are discovered that are larger than Pluto, I feel it would be best if Pluto was demoted.

BTW, just wait until Cassini gets to Saturn. I guarantee you it will discover new small moons that Voyager missed, and this will ignite a debate about whether objects are moons or ring particles...

[selden]

The argument as to whether or not Pluto is a planet is a dead horse beaten to a bloody pulp by the professional astronomers. The final decision was that, while it actually is just one of many large TNOs that are in a 3:2 resonance with Neptune, it will continue to be called a planet because that's what people want.

[Evil Dr Ganymede]

Here's another one...

http://news.bbc.co.uk/2/hi/science/nature/3511678.stm

All this is still conjectural at this stage though - I'll laugh if they've actually found a Brown Dwarf out there .

[Ynjevi]

I don't think it makes sense to call Sedna (or Pluto) planet. There are probably dozens of bodies with diameters over 2,000 km.

[Evil Dr Ganymede]

As far as I'm concerned, Pluto is a planet purely for historical reasons, and that's how it'll stay in my opinion. If more KBOs had been discovered in the months/years immediately after Pluto was discovered in 1930, we'd almost certainly not be having this argument now, since we'd think they're all KBOs anyway.

Or alternatively, if the second ever asteroid had been discovered over 70 years after Ceres was found, then we'd probably having the same argument about whether Ceres is a planet or not.

And at the end of the day, does it even really matter whether something is classed as a big asteroid or a small planet? It doesn't somehow change their physical natures and make them more or less important or interesting...

[Ynjevi]

As far as I'm concerned, Pluto is a planet purely for historical reasons, and that's how it'll stay in my opinion. If more KBOs had been discovered in the months/years immediately after Pluto was discovered in 1930, we'd almost certainly not be having this argument now, since we'd think they're all KBOs anyway.

True, altough IMHO reclassification from planetary oddball to largest and most interesting known KBO is hardly a "demotion".

Or alternatively, if the second ever asteroid had been discovered over 70 years after Ceres was found, then we'd probably having the same argument about whether Ceres is a planet or not.

Actually Ceres was considered a true planet for some time. Bode's "law" predicted a planet between Mars and Jupiter, so it was expected. A bit same way as (nonexistant) disturbations in Neptune's orbit lead to discovery of Pluto. Only after few more asteroids were found, they were demoted to minor planet status. They even had own planetary signs.

And at the end of the day, does it even really matter whether something is classed as a big asteroid or a small planet? It doesn't somehow change their physical natures and make them more or less important or interesting...

Indeed.

PS. Looks like Sedna homepage is online.

[Ynjevi]

This is told now:

* provisional designation 2003 VB16
* perihelion 76 AUs, aphelion near 900 AUs -> it is not a KBO but possibly a Inner Oort Cloud object
* orbital period 12,260 years
* it was not detected with Spitzer or IRAM, thus

* surface reflectivity lies between 20%-100%
* and size between 1/3 and 2/3 the size of Pluto

Local6.com article says

The team also have indirect evidence a tiny moon may trail Sedna, which is redder than all other known solar system bodies except Mars.

Umm... what about Amalthea?

[Evil Dr Ganymede]

PS. Looks like Sedna homepage is online.

Looks like it's down now...

Honestly, NASA have really ballsed up this press release, if the announcement that was scheduled to be made in about 40 minute's time is actually the "discovery announcement". They've had people blabbing about this to newspapers, other agencies scooping those papers, webpages going up and down...

I'm not going to trust any numbers or figures till after their announcement is done, then I know whether what I've been hearing about the past day or so is actually real or not!

[Evil Dr Ganymede]

...and it's official!

http://www.nasa.gov/vision/universe/sol ... _body.html

Get a load of that orbit though - it takes 10,500 years to complete one orbit, and goes way out to 900 AU?!?! (it's currently around 86 AU, and it's getting closer over the next few decades).

So who's going to write up the orbit for Celestia?!

[Evil Dr Ganymede]

Well, if ynjevi's link to the orbital parameters was correct, then they are:

Code: Select all

2003 VB12
Epoch 2004 July 14.0 TT = JDT 2453200.5                 MPC
M 357.88147              (2000.0)            P               Q
n   0.00008040     Peri.  311.82711     -0.11942975     -0.98555605
a 531.6576335      Node   144.49288     +0.96115905     -0.14507665
e   0.8574338      Incl.   11.93041     +0.24881681     +0.08736153
P 12260            H    1.7           G   0.15           U   4


So the Celestia version is:

Code: Select all

"Sedna" "Sol"
{
   Class "asteroid"
   Texture "asteroid.jpg"
   Radius 850
   Albedo 0.05

   EllipticalOrbit
   {
   Epoch         20040714
   Period         12260
   SemiMajorAxis      531.6576335
   Eccentricity      0.8574338
   Inclination      11.93041
   AscendingNode      144.49288
   ArgOfPericenter      311.82711
   MeanAnomaly      357.88147
   }
}


[granthutchison]

The Epoch in Celestia is given in Julian days, so that would be:

Code: Select all

"Sedna" "Sol"
{
   Class "asteroid"
   Texture "asteroid.jpg"
   Radius 850
   Albedo 0.05

   EllipticalOrbit
   {
   Epoch         2453200.5 #<= Julian date
   Period         12260
   SemiMajorAxis      531.6576335
   Eccentricity      0.8574338
   Inclination      11.93041
   AscendingNode      144.49288
   ArgOfPericenter      311.82711
   MeanAnomaly      357.88147
   }
}


Grant

[Evil Dr Ganymede]

The Epoch in Celestia is given in Julian days, so that would be:

Oops. That would explain why Sedna appeared to be about 350 AU from Sol on its orbit then . I've corrected it now - thanks, Grant.

Here's a view from 4000 AU above Sol (I labelled Sedna as a planet here, to make it stand out more)... look at the size of that orbit!!!



(the blue circle is Pluto's orbit!)

[Evil Dr Ganymede]

The official Sedna homepage linked to earlier is back up again.

http://www.gps.caltech.edu/~mbrown/sedna/

Lots more info there!

EDIT: I spotted a mention there of a possibly 40 day long rotation period. That's something to add to the ssc code...!

[brunetto_64]

wooooow.....it's very far!!!!!

[Evil Dr Ganymede]

I took the liberty of adding a moon as well, since there might possibly be one. I figure it must be fairly large considering that there is a suspicion that one is present (it must be big enough for the astronomers to have detected it somehow).

The parameters for the moon are at the moment entirely conjectural (I borrowed them from a tiny satellite of Jupiter ).

Code: Select all

"Sedna" "Sol"
{
   Class "Planet"
   Texture "asteroid.jpg"  #or amalthea.jpg?
   Radius 850
   Albedo 0.05
   RotationPeriod 960
   Obliquity 67

   EllipticalOrbit
   {
   Epoch         2453200.5
   Period         12260
   SemiMajorAxis      531.6576335
   Eccentricity      0.8574338
   Inclination      11.93041
   AscendingNode      144.49288
   ArgOfPericenter      311.82711
   MeanAnomaly      357.88147
   }
}

"Sedna B" "Sol/Sedna"
{
   Class "moon"
   Mesh "roughsphere.cms"
   Texture "asteroid.jpg"
   Radius 200

   EllipticalOrbit
   {
   Period            43.88
   SemiMajorAxis     50000
   Eccentricity      0.04
   Inclination       25.851
   AscendingNode   312.669
   ArgOfPericenter  172.672
        MeanAnomaly     329.329
   }

   RotationPeriod   960.0
   Albedo            0.04
}


#2003 VB12
#Epoch 2004 July 14.0 TT = JDT 2453200.5                 MPC
#M 357.88147              (2000.0)            P               Q
#n   0.00008040     Peri.  311.82711     -0.11942975     -0.98555605
#a 531.6576335      Node   144.49288     +0.96115905     -0.14507665
#e   0.8574338      Incl.   11.93041     +0.24881681     +0.08736153
#P 12260            H    1.7           G   0.15           U   4

# Moon data is hypothetical at this point


[Thalass]

I just got linked to this, which has some info, probably already stated in the other links. heh.


Oh! and hi, by the way.