We're no longer biggest star system!

DaveC426913

Yet to be confirmed, but they've discovered a star system with 9 planets! (And those are just the big detectable ones!)

The two latest are (nearly) super Earths. (well, 12x and 32x Earth's mass...), probably rocky.

http://news.nationalgeographic.com/n...space-science/

http://exoplanet.eu/star.php?st=HD+10180

TGlad

Fantastic. I was waiting for that to happen... I think 6 planets was the most last time I looked at exoplanet.eu. I wasn't expecting 8 to be bettered so soon.

HallsofIvy

Dang! I want Pluto back!

Steely Dan

This just in: the IAU votes to reverse its 2006 decision, and adds Eris to the list of planets as well, citing a need for our solar system to remain on top.

Whovian

Why? Why should our Solar System need to be the biggest?

SHISHKABOB

you must be an alien spy from this HD 10180 system! Trying to trick us into thinking we are still "adequate" with our smaller number of planets!

Orion1

Stars with larger accretion discs produce more planets?

What would the planet number theoretical limit be for stars with large accretion discs?

msouth

We still have nine planets--Earth's moon is large enough that its orbit is always concave toward the sun. It's a planet, with an orbit highly perturbed by a larger neighbor.

The idea of de-planeting Pluto without admitting that we have been miscategorizing the moon as a mere satellite makes me laugh.

If your orbit is always concave toward the sun YOU ARE ORBITING THE SUN.

That's a much more compelling, understandable, and intuitive description than something that needs to fuss about where the barycenter is. You could have an added descriptive for a double planetary system with a barycenter inside one of the planets.

Seriously--who lets these guys make this stuff up?

Whovian

First of all, how does its size affect whether or not its orbit is always concave towards the sun? Second, by your arguments, pretty much everything in the Asteroid Belt should also be considered a planet?

True, but you're also orbiting the Earth.

I don't understand. Are you saying we had it wrong before, or that we still have it wrong?

Okay ... but again, the Moon's also orbiting the Earth.

\Ignores that question

ViewsofMars

Thanks Dave I recall reading back in 2010 about HD10180.

"The HD 10180 system represents an interesting example of
the various outcomes of planet formation. No massive gas giant
was formed, but instead a large number of still relatively massive
objects survived, and migrated to the inner regions. Building a
significant sample of such low-mass systems will show what are
the relative influences of the different physical processes at play
during planet formation and evolution." (C. Lovis et al.: The HARPS
search for southern extra-solar planets, Astronomy & Astrophysics
manuscript no. HD10180 ESO 2010 - August 13, 2010, p.15 :
http://www.eso.org/public/archives/r...35/eso1035.pdf)

SHISHKABOB

moon = planet?

I feel like you're saying this just to be contrary >.>

DaveC426913

OK, let's assume you're not pulling our leg.

1] By definition, if it's orbiting a planet, it's not a planet. And yes, the Moon is orbiting Earth.

2] Size has nothing to do with it. If did want to factor size in as part of some new msouthian definition of planets, why start with the Moon, why not start with all the objects larger than the Moon yet still not planets?

mfb

We are still in the system with the most known objects [optional: orbiting the star].
And this won't change in the foreseeable future, unless some aliens send us terabytes of data about their own system.

So we have trillions of planets? Cool.

TGlad

"We are still in the system with the most known objects. And this won't change in the foreseeable future"

I'm not so sure. Anyway, counting numbers of objects is unhelpful when they follow a power law, since the number is effectively infinite for most star systems. Better to get a fractal measure, i.e. plot quantity against radius (or mass) on a log-log graph, and compare the height and slope for different star systems.

DaveC426913

Well, there are currently 88 objects in the solar system larger than 200 miles in radius. It is going to be quite a while before we are able to detect objects smaller than that in extrasolar systems.

TGlad

True, but simulations are getting more sophisticated, I could imagine simulations being able to show beyond reasonable doubt that a system must have over a certain amount of mass in its vicinity in order to fit with various stellar observations. And given that no giant planet is found, it there must be at least 100 objects bigger than 10km in order to be stable... or whatever.

So yeah, I don't imagine us detecting 89 individual small objects in a faraway star system anytime soon, but I could see how one could build sufficient evidence for a system requiring over a 100 such objects in order to fit with observations and simulations and accurate models of that star's formation etc.

DaveC426913

I don't think anyone doubts that other systems are probably like our own. We are simply talking about what is currently known and factual.