Friday, July 29, 2005

Off-topic: Tenth Planet Found

Busy day today, news wise. First we have active venting found on Enceladus announced. And now, a new planet! News reports have been circulating today regarding a newly found Trans-Neptunian object called 2003 EL61. Early reports, from a team of astronomers led by Jose Ortiz, suggested that the object was perhaps as large as Mars. However, a team led by Mike Brown announced that results from Spitzer suggested that 2003 EL61 is much smaller, maybe 1500 km across, smaller than Pluto. In addition, a much smaller moon was found orbiting 2003 EL61. By measuring the orbital period (49 days) and the orbital distance, Brown's team found the mass of the system to be only 30% of Pluto.

But that's not what I am talking about. I am talking about another discovery made by Mike Brown's team, 2003 UB313. A lower limit of the size for this object is a little larger than Pluto, meaning this world is definitely larger than Pluto. Size estimates assuming an albedo of 0.25, or around the albedo of other large bodies in the Kuiper Belt suggest a size around that of Mars.

So definitely an exciting discovery. Again, because this is off-topic from the discussion of outer planet satellites, I will limit discussion of 2003 UB313 to this post, unless of course a moon is found...

UPDATE: 07/29/2005 6:25pm: JPL has a press release now on their site about 2003 UB313. The new planet appears to be 2600 km across with bounds of around 2300 km (assuming it reflects all the light it receives from the sun, an unlikely proposition) and 3000 km (because it failed to be detected by Spitzer). Spectroscopy of 2003 UB313 indicates the presence of methane ice on the surface. In addition, Mike Brown's group has a website about the new planet that might be worth monitoring for the next few days, as well as the Wikipedia page.
UPDATE: 07/29/2005 8:08 pm: Planet not named Lila nor is the proposed name Lila. Please disregard.


Anonymous Anonymous said...

Let us not forget 2005 FY9, the third of the trio of giant KBOs announced today. From the given H value, it appears to be between 2003 UB313 and 2003 EL61 in size:

2003 UB313 : H = -1.1 D = ~2600 km
2005 FY9 : H = 0.1
2003 EL61 : H = 0.4 D = ~1600 km

For comparison, we have:
Pluto : H = -1.0 D = 2320 km
Charon : H = 1.0 D = 1270 km
Sedna (2003 VB12) : H = 1.6 D = ~1600 km
90482 Orcus (2004 DW) : H = 2.3 D = ~1500 km
50000 Quaoar (2002 LM60) : H = 2.6 D = ~1300 kn
28978 Ixion (2001 KX76) : H = 3.2 D = ~1065 km
55636 (2002 TX300) : H = 3.3
55565 (2002 AW197) : H = 3.3 D = ~890 km
55637 (2002 UX25) : H = 3.6
20000 Varuna (2000 WR106) : H = 3.7 D = ~900 km
2002 MS4 : H = 3.8
2003 AZ84 : H = 3.9
90568 (2004 GV9) : H = 4.0


7/29/2005 07:58:00 PM  
Blogger Jason said...

The debate is now raging on whether this (and Pluto) should be a planet. My personal opinion is to make the cutoff size pluto (diameter = 2250 km) and every thing orbiting the sun, regardless of location or orbit (since objects can easily be thrown into an orbit with high inclination). Thus new object is a planet, IMHO.

That and Pluto and this object are clearly different compositionally from the rest of the Kuiper Belt objects. So there is a nice descriminator (other than size) that distinguishes very large KBOs/planets from large KBOs/non-Planets.

8/01/2005 10:05:00 AM  
Blogger Bruce Moomaw said...

Uh-uh. They're "compositionally different" only in the sense that they have methane frost, which is due to their large size. Somewhat smaller objects are likely to have smaller amounts of CH4 frost, all the way down to negligible quantities. So, yet again, there ain't no real dividing line -- which is the main thing we ought to be teaching grade-school kids about this whole subject. Contrary to some dire predictions, I really think most kids are emotionally resilient enough that the revelation won't blight the rest of their lives.

8/02/2005 01:21:00 PM  
Anonymous Emily Lakdawalla said...

One thing I always find sad about this debate is that no definition of "planet" will ever include some of the most fascinating worlds in our solar system -- Io, Europa, Ganymede, Titan, Enceladus, Iapetus, Triton. It's sad because Pluto is a place we've never seen, and I rather doubt we'll send a ship to 2003UB313 in my lifetime; by contrast, we've been to all those other places and discovered amazing things. Yet kids and adults can cite the little that is known about Pluto, but give you blank looks when you talk about even the most sensational moons like Europa and Titan. All the discussion about "what is a planet" takes the focus away from all these other worlds.

We'd like to light a fire under the space agencies to send a mission to Europa, but it's going to be much harder to drum up public support than it was for Pluto, because Pluto is a planet, and Europa isn't.

8/02/2005 06:03:00 PM  

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