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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."
...since "weight" is a measure of gravitational pull on an object? Have denser mass, sure, but weight? Weird.
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.
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
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What's up with astronomers making outlandish claims based on the flimiest of evidence. There's a dozen or so other things than a dense core that would have shown up the same on their model. They have no way of knowing that a dense core, rather than, for example, a dense planet is causing the motions.
/. scientists saying "omg teh dakr spot! tere must be teh lakezorz!" http://science.slashdot.org/article.pl?sid=05/06/2 9/1610223&tid=160&tid=14
And this isn't new. Just a few days ago, we saw on
And remember the "scientists" who said "gee, there's sediment at the bottom of basins on Mars. 100% chance there was water there in Mars's history!"
Whatever happened to scientific restraint? Whatever happened to waiting for the right evidence?
I'd say it's time for IPX to head out and start mining that core.
An offtopic mod, and a comment about planetary rape - I guess you fell for the common mistake of assuming geeks are familiar with SciFi ;-) "What is this Babylon 5 of which you speak?"
Back on-topic, what is the deal with extra-planetary mining? Legally? Is it just a matter of time, or are other planets protected like Antartica, say?
This is where the serious fun begins.
Actually, we do.
Ben Hocking
Need a professional organizer?
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The page talks about the history of detecting the planets and the various methods used.
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?
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.
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."
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Linq
"Learning is not compulsory... neither is survival."
--Dr.W.Edwards Deming
Yes, it would have interesting effects. Fortunately, were quite a few orders of magnitude away from those sorts of issues. (The moon is ~10% of the mass of the earth. If we can remove enough mass to affect tides on earth, we probably aren't all that far from building a ringworld or dyson sphere)
Well, simply removing mass would not alter the moon's orbit, for the same reason that a hammer and a feather fall at the same speed in a vacuum. But, we would decrease tides significantly. Also, the mass has to go somewhere, ie it has to have some momentum, and depending on how we give it that momentum, conservation of momentum might mean that we had also given the moon an equal amount (although opposite in direction) amount of momentum, which could change its orbit.
SIGSEGV caught, terminating
wait... not that kind of sig.
if we finally got around to mining the moon, wouldn't we get to a point where we'd have removed so much mass as to alter the moons orbit?
Just an amusing note... if we mined that much mass from the moon and used it on earth we'd noticeably alter the force of gravity on earth first! Chuckle. By my calculations bringing just 3% of the moon to earth would increase earth's gravity enough to increase the average person's weight by an ounce. A nontrivial gravity change, and probably more signifigant than anything related to a 3% change in the moon itself.
Any mining operation having an actual impact on the MASS and ORBIT of the moon would require science and engineering on a level "sufficently advanced as to be indistinguishable from magic". Any discussion of enviornmental impact is meaningless, overwhelmed by the other unknown impacts and capabilites of that level of scientific magic.
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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.