Odd Planet Confuses Scientists

eldavojohn writes "While there's been a lot of debate about what is a planet, there is a recent discovery that has scientists even more confused. COROT (COnvection ROtation and planetary Transits) spotted an object that appears to be the size of Jupiter yet is 21.6 times more massive ... and orbits its star in a mere four days and six hours. Now, the other piece of the puzzle is that the star it orbits is more massive and only slightly larger than our Sun. But they can't describe this thing orbiting it. So far they think it is more likely to be a 'failed star' but have settled with 'member of a new-found family of very massive planets that encircle stars more massive than the sun' to describe it accurately."

I hate to say it..

... but that's no moon.

Re:I hate to say it..

You're so dense.

Is orbital mechanics fractal?

One thing I've wondered about: Does orbital mechanics lead to fractal planetary arrangements?

If so, binary stars and star/gas-giant planetary systems are just points in a continuum.

Re:Is orbital mechanics fractal?

My bet is that they just misplaced a decimal point somewhere. It's always some mundane detail like that.

Re:Is orbital mechanics fractal?

Does orbital mechanics lead to fractal planetary arrangements?

Good, question, but my "shooting at the hip" answer is that while there may be some tendencies toward that kind of arrangement, that applies to certain conditions that are limited. Roughly, around our star, each planet ~2x the distance as the previous, out to Neptune or so.

I'd guess that while it happened here, that it won't happen everywhere, or that there's only a tendency toward this.

I think the idea of trying to define a planet vs asteroid vs planetoid vs failed star is kind of like trying to define the difference between a pebble", a rock, a stone, and a boulder. When does a pebble become a rock? When does a rock become a stone, and when does a stone become a boulder?

There's no clear line, and there doesn't need to be. Seriously: why do we care?

Re:Is orbital mechanics fractal?

A usual property of fractal dimensions is they aren't integers. Cases with interger dimensionality in articles and books on fractals are simplified or 'degenerate' fractals. If scientists found themselves relying on math that involved non-integral dimensions to describe planetary systems, I could definitely see there being 'fractal planetary arrangements', but baring that, similarities across scales aren't enough to throw around a word such as fractals.
      The idea sounds like an extension of Bode's law, by people who are trying to modernize the old model. The original Bode's law may have been a case of people seeing patterns that aren't really there in reality at all, simply an overfunctioning of the brain's pattern detecting apparatus. Knowing there's a temptation to interpret the data this way, I'd be cautious trying to stretch fractal math to fit unless all of it fits.

That's no planet.

"the size of Jupiter yet 21.6 times more massive.. and orbits its star in a mere four days and six hours."

That's New Year roughly twice a week, by Jove.
Party on ; ).

Re:That's no planet.

He capitalized it. Maybe that's the name of his cat.

What's it made of?

If it is twice as dense as lead, what is it made of?

Re:What's it made of?

Metallic Hydrogen? Though you would think that it would begin to fuse at that kind of mass-density. Then again, 26 times the mass of Jupiter is still less than 3% the mass of the sun so perhaps not. My guess is that this is the edge case. If there were even a little more mass it would have collapsed into a red dwarf and started fusing hydrogen.

Don't think so

Actually, I don't think that metallic hydrogen is twice as dense as solid lead.

If you look at most metals, the higher the atomic weight, the higher the density of the solid. Depleted uranium is heavy, while Aluminium is lightweight, and Lithium is half the density of water, for example. So for hydrogen, metallic or not, to be denser than lead, you need it to be packed tighter than, I think, is physically possible.

At some quick maths, a hydrogen atom is 1, lead is 207-208 (82 protons and a load of neutrons.) I know that some mass is actually in the binding energy between those, but for some quick and very approximative maths let's say a lead atom is 200 times heavier than a hydrogen one. (Plus/minus something.) At the same distance between atoms, lead will be 200 times heavier than hydrogen. To go for twice as heavy, you need the hydrogen atoms to be packed at over 7 times less distance from each other than lead atoms are.

At a quick googling, the estimated range of densities for metallic hydrogen is anywhere between 0.4g per cubic centimetre (less than lithium) and 4g per cc (4 times as heavy as water), with apparently 0.8 being the most likely candidate for where it turns metal. Compress it any denser and it'll start to fuse. And we're still nowhere near as heavy as we need for that planet.

What throws a further spanner into it, is that our own gas giants _already_ have a core of metallic hydrogen. That' what's in the middle of Jupiter and Saturn. So something 26 times heavier, hmm, must be something else.

Re:

Really dense lead?

Re:What's it made of?

I wonder if this is just a result of some weird gravitational lensing effect? I'm not very familiar with the technique, but from what I understand, its kind of like looking at a shadow in order to try and figure out the shape of an object... except the light source is light years away and the object is equally far away.... I'm sure as time goes by and our observation techniques improve, we are going to see many different things that we never thought would be possible. Yes yes... physics is physics, but humanity has a problem with adjusting to scales, and space is a very, very big thing.

There is little way to control the environments in order to do controlled experiments, all we have are observations... which at such great distances, must be very susceptible to nearly infinite sources of interference that we simply cannot identify with present means.

With that said... a new category of planets off of one object? Getting carried away much...?

Bad Data

This was followed up on the astro mailing lists as faulty data -- the observers mistook sunspot-dimming for a planet passing in front of the star. The correction hasn't made it to journalists yet and the science article is still in draft, so no link-to-reference, sorry! Planetary formation theory is fragmented and deeply in need of reworking (anyone want a phd topic?), but not to incorporate Jupiters in Mercury-orbits (yet).

Re:Bad Data

Uh, we know of a bunch of Jupiter or larger sized planets in closer than Mercury orbits. This isn't anywhere near the first. It's density is it's unique trait.

Hold on a minute here...

The density of Jupiter is about 4/3, so 21 times that would put it at 28 and change. That means it would have to be significantly denser than Iridium (about 22). That means it would have to be either:

• An enormous lump of some element with a very short half life
• Something from some island of stability
• An ultra-compact degenerate form of normal matter (iron nickel compote)
• A data error

Guess where I'd put my money...

--MarkusQ

Re:

The core of a brown dwarf has a density somewhere between 10 and 10^3 g/cm^3. That means the cores of brown dwarfs have to be either:

• Enormous lumps of some element with a very short half life
• Something from some island of stability
• An ultra-compact degenerate form of normal matter (iron nickel compote)
• A data error
• Something that's not in your list (like compressed gas)

Guess where I'd put my money....

Seriously: brown dwarfs all have about the same radius as Jupiter, but range in mass up to about 60 times that

Caught me

density is unitless ?

In some systems, yeah, it is. Set c=1 (space-time unification), measure masses and energies in the same units (E=mc^2), and so on. But I (obviously) wasn't using one of those systems, I was using g/cm^3, as you probably realized.

--MarkusQ

Re:Caught me

Density isn't exactly dimensionless, but if you set things up so the density of water is 1 in a system of measurements, the densities of other things (i.e. Lead, Iridium, or this planet) will come out the same numbers, regardless of the units used. So it's not necessary to really specify the units, just that H2O at STP = 1 in whatever system you are using.

Re:

Now, take something the size of Jupiter, put it close enough to orbit every 4 days, and ask yourself: could that maybe be an environment where gas laws might become significant?

Admittedly I'm just eyeballing it, but I can't see how you can make that work. Remember the T part of P=T/V works against you here; the higher temperature should make it less dense, which both reduces the gravitational forces on the outer portions (larger r) and increases their area and thus the amount of energy those on the sunwar

Good point

Good point. This planet should be about

(0K+6000K)/2
------------------
150000000K

or about 1/50000 the temperature and thus could on that basis be up to 50000 times as dense.

But that can't be the whole picture. At those pressures you'd no longer be dealing with a gas--the volume-per-atom of He would be way out of line. A helium atom occupies about (3.1e-9 cm)^3 or 3e-26 cm^3, and has a mass around 4 * 1.66e-27 kg = 6.66e-24 g, for a per-atom density of about 222 g/cm^3.

So if you could get a core m

Re:why not classify them with letters? ala star tr

Because the astrological community is too busy hoodwinking people with talk of Jupiter in the Second House, and horoscopes, and other nonsense.

Re:

Comprised of PS3? It will be hotter than the sun if someone turns that thing on and starts folding!

Re:

Dyson Sphere's got the Sun in the middle,

Sun in the middle, Sun in the middle

Dyson Sphere's got the Sun in the middle, and a great big bubble all around.

Detecting Exoplanets

There are two ways of detecting exoplanets:
1. Wobbles -- what you explained: watch a star for deviations in its orbit by observing tiny redshifts and blueshifts. Our own sun does a little jiggle thanks mostly to Jupiter.
2. Dimness -- what they did for this object. Watch a star for dimming as something passes in front of it, although you have to be careful of other causes of temporary decreases in luminescence (like sunspots).

In both cases, it really needs repeated observations over time to establish that it's an orbital event and not something random. In the good ol' days of exoplanet discovery when the equipment wasn't so hot & we expected to find planets pretty much like ours, it took a whole lot of observations before anyone was willing to take the risk of announcing a discovery. Now, with better equipment making it easier to detect hiccups in a star's routine and a more open attitude about how planets behave, discoveries are being announced a lot earlier in the observation process.

To be fair, TFA does give itself a whole lot of wiggle room in interpreting the data. It just fails to mention that follow-up observations aren't confirming the orbital parameters of the assumed planet.