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Planet Discovered with a Massive Core
helioquake writes "A collaboration of astronomers discovers possible a 'Rossetta Stone' of planetary formation study, reported by San Francisco State Univerity and Subaru Observatory. This new planet, orbiting around G-star like our Sun (HD 149026), weighs roughly equal to that of Saturn, while its size is significantly smaller in diameter. Planetary modeling suggests that the core of the planet alone must have 70 times more mass than Earth, indicating the possible existence of a metallic solid core inside the planet. Just like the rocky planet discovered earlier, the finding of this dense-core planet may lead to better understading of the formation of rockey planets in the Universe."
I'd say it's time for IPX to head out and start mining that core. There's probably quite a bit of rare minerals in it.
Its influence on the star's wobble, AFAIR.
Me (Blog)
Undoubtedly they measure it by the effect it has on its surroundings. Mass equates to gravitational pull, which can manifest itself in the curvature of light as it passes by it.
Call me when they discover a giant planet, with a metallic core outside the planet. That's the armored base from which they keep sending us aliens like Ann Coulter and Tom Cruise. Then we just drop magnet-tipped nukes into space, and finally it's safe to watch TV again.
--
make install -not war
It's too bad that the only planets we can reliably locate at this time are the freaky-deeky ones that are too massive, too close to their primary, or are in orbits far too elliptical to give life a decent chance...each new system looks like a good example of how not to design a solar system capable of sustaining life.
Hopefully, this will change when the interferometer goes up around 2015.
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~ |rip/\/\aster /\/\onkey
Well, its sun must exert quite a gravitational pull on it to maintain its orbit, so in that respect it does have weight.
Though I agree, I believe the poster was mistaken (as is often the case when talking about "weight" versus "mass", especially for celestial objects).
Heavy Metal planets are so Hard Core.
I'll be your candy shop of infinite deliciousity if you'll be my discotheque of endless rump-shaking.
Managerium
- None can love freedom heartily, but good men; the rest love not freedom, but license. -- John Milton
It's not too difficult, conceptually. The star's mass is a function of its brightness. So, you already know the mass of the star. The orbiting planet causes the star to wobble a bit. The more massive the planet, the more the star wobbles. Weight is not the same as mass, by the way. Weight is what you get when you place a mass in a gravitational field. More info on this: http://ethel.as.arizona.edu/~collins/astro/subject s/srchplanet5.html
----- One learns to itch where one can scratch.
...Scientists at Tom's Astrophysics Guide and Ars Astra estimate that this new massive core planet is still capable of outperforming the latest Intel dual core planets by up to 20% in the all-important Halo 2 benchmark.
AMD vows to release planet with dual massive cores by end of '05. Intel responds by renegotiating contracts with its distributors.
How much can we model to show what an environment like this is like? That planet's magnetosphere must be fierce. There must be a lot of side effects from that, both for it and any moons it may have.
Actually, we do.
Ben Hocking
Need a professional organizer?
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~ |rip/\/\aster /\/\onkey
I have a massive core but no one ever writes about me.
The page talks about the history of detecting the planets and the various methods used.
1) An object travelling in a circular (or eliptical) orbit requires a certain force toward the center of the focus of the orbit, called centripetal force. It is proportional to the product of the mass times the radius of the orbiting body, and inversely proportional to the square of the period of the orbit.
2) Two massive objects will assert an attractive gravitational force on each other, proportional to the product of their masses, and inversely proportional to the square of the distance between the objects.
All astonomers do is equate one force to another. Astronomers believe that they can calculate the mass of the star by observing the star's apparent brightness, and looking at the star's spectrum to figure out what kind of star it is. Unfortunately, the observed brightness of a star is a function of its distance from Earth, and this measurement has a large degree of error for most stars.
Next, astronomers look at how quickly the star "wobbles" due to the orbit of the planet. This gives a good measure of the period of the planet's rotation.
The final step is to figure out how far the planet is from the star. After entering in all the data, you are left with the mass of the planet being a function of its distance from the star. If you apply some trickery in the form of Kepler's Laws, you can see that the period and radius of an orbit are related.
And that's it! Put all the pieces of the puzzle together, and you have an equation for the mass of the planet. If you are lucky, then the plain of the orbit is end-on when observed from Earth--this allows you to see how much of the star's light is blocked from the eclipsing planet, giving you some measure of the planet's size and composition.
/*No comment*/ #No comment
And co-orbital planets probably wouldn't last long. An exception to this are asteroid belts. However, in general, two (or n) planets would show up as different frequencies in the wobble of the star. The magnitude of each frequency gives you a lower limit on the mass of the star. You can only get a true measure (as opposed to a limit) by also knowing the inclination of the planets' orbit relative to our line of sight.
Ben Hocking
Need a professional organizer?
My guess (I really have no idea, but it seems reasonable) would be that they can tell it's a gas giant, and may even be able to determine the type of gas by the reflected light. This means they can rule out the planet in its entirety being superdense. Then, based on the wobble of the star, they can determine the planet's mass. Since they already know the possible mass for a gas giant of its size, they know there is something within it that must have far greater gravitational attraction, and hence greater mass. Therefore, it must have a superdense core of some type.
Let me reiterate, I really have no idea what I'm talking about. Then again, that doesn't mean I'm not right ^_^.
Let me add to that. We know that a G0 star has roughly the same mass as that of our Sun (*). Once you have some handle on its mass, you can do the following:
(1) examine the wobble pattern of the main star,
(2) then examine the effect of occultation (eclipse) by the planet (i.e., when the planet goes in front of the star, the brightness of the star decreases...which gives you a sense on how big this planet is with respect to the star's apparent disc),
(3) then use Kepler's third law to derive the size of its orbit,
Now you have two unique information: the orbital radius and apparent size of the planet. Unlike the earlier finding of the rocky planet, this study can provide you a quantitative estimate on how physically big this planet must be. And that turns out to be quite smallar than Saturn. You can also derive the mass of the planet from the scale of the wobble in the main star. Combining that with the physical size of the planet, you can derive the density of the planet.
(*) Kepler's law goes like this:
(2*pi/Period)^2 * (size)^3 = G * Mass
where G = gravitational constant.
If you plug in the Period (==2.87days) and size (0.046AU...circular logic, I know) of the planet, then you'd get the total mass of the star system to be about twice the mass of the Sun, roughly what we expect to be for a G0 main sequence star.
Who cares if it's far away. I want to know how they measure the Earth's mass. I always figure they just turned a bathroom scale upside down.
Stop Global Warming!
Just say no to irreversible processes!
...if they have crappy movies about their core too. Poor bastards.
Authority questions you. Return the favor.
Key word: little bit. Given that this happening REALLY far away, and we're only observing it through telescopes, it's almost impossible to measure accurately.
We can measure the effect of wobble quite accurately. The current accuracy is about +/- 1 or 2 meters per second. That's usually good enough to detect a planet like this.
But your points are well taken. There are uncertainties to be considered in the analysis. I'm sure these guys did take that into account in their work.
If you have no interst in the universe outside your basement you probably won't get excited. However if you happen to be an astrophysicist or even have a remote interest in new discoveries then you might just find this interesting, because we've never seen anything like this before.
The planet in question posses the largest known core of any known extrosolar planet. So what? you say, well this just happens to be the first observational evidence supporting a planetary formation theory known as core accretion. So thanks to this observation confirming the theory, we now know that there should be a lot more of these planets. And as such a little bit more about the universe around us.
But of course because we cant get there tommorow this sort of work is a waste of time.... Tell you what, why don't you return to your cave and I'll send you an email when we've invented warp drive and found another planet. Then you can go live on it and the rest of us can waste out time with these boring discoveries.
Those bastard scientists - studying things that interest them. We should round them up and force to study more practical things... you know... your onto something there... but why stop at scientists? I say we round up all the programmers and make them do something useful like farming while we're at it. Why waste their time making video games, when they could be growing crops for hungry Africans?
The concept of a "Rosetta Stone" in a generic discovery of signifigance. Rosetta Stone referes to a tablet that had a simultaneous translation of Heiroglyphics, Latin, and Greek, that allowed linguists to finally start cracking the secrets of the ancient Egyptian's written Language.
This specimin that takes science in a new direction is more akin to "Mercury's Orbit."
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
Of course this means that planets are weightless. That seems entirely reasonable, it's the mass that's being measured, and weight isn't a terribly useful concept when you're talking about planets.
Doesn't it make you feel good to know that our freedoms are protected by politicans, lawyers and journalists.
While its all well and good to insist that corporations only spend money on things that make a profit - that has never been, and hopefully will never be, the mission of the US government.
Although, as someone (Martin Gardner?) once put it: If a stool weighs ten pounds, then the planet weighs ten pounds relative to the stool. (Turn the stool upside down!)
Just so you know, "subaru" is the Japanese name for the star cluster Pleiades.
No luck finding the preprint so far. But here is the thing.
This is a G0 star, so it's likely to have a similar scale size as our Sun. Looking up Simbad, I see that this star is located roughly 80 parsec away, which isn't too far. Now, this new planet. It is 0.72 times the size of Jupiter. So if you take the ratio of apparent discs, it'd be
(pi * (0.72 * 0.7e5km[Jupitar])^2) / (pi * (7.0e5[Sun])^2) ~ 0.005
or 0.5%. So all you need is to achieve +/- 0.1% accuracy in photometry to derive the apparent size...there, easier said than done. No wonder they needed a big telescope to do this accurately.
I think it's doable, though your points are well taken, too. I wouldn't be surprised if there is a factor of two errors.
Subaru is a Japanese constellation name. The logo for Subaru cars looks like a bunch of stars, but it actually depicts that constellation.