Researchers measure orientation of multiplanet system, find it very similar to our own solar system

Jul 25, 2012 by Jennifer Chu
In this artist interpretation, the planet Kepler-30c is transiting one of the large starspots that frequently appear on the surface of its host star. The authors used these spot-crossing events to show that the orbits of the three planets (color lines) are aligned with the rotation of the star (curly white arrow). Graphic: Cristina Sanchis Ojeda

Our solar system exhibits a remarkably orderly configuration: The eight planets orbit the sun much like runners on a track, circling in their respective lanes and always keeping within the same sprawling plane. In contrast, most exoplanets discovered in recent years — particularly the giants known as “hot Jupiters” — inhabit far more eccentric orbits.

Now researchers at MIT, the University of California at Santa Cruz and other institutions have detected the first exoplanetary system, 10,000 light years away, with regularly aligned orbits similar to those in our solar system. At the center of this faraway system is Kepler-30, a star as bright and massive as the . After analyzing data from NASA’s Kepler space telescope, the MIT scientists and their colleagues discovered that the star — much like the sun — rotates around a vertical axis and its three planets have orbits that are all in the same plane.

“In our solar system, the trajectory of the planets is parallel to the rotation of the sun, which shows they probably formed from a spinning disc,” says Roberto Sanchis-Ojeda, a physics graduate student at MIT who led the research effort. “In this system, we show that the same thing happens.”

Their findings, published today in the journal Nature, may help explain the origins of certain far-flung systems while shedding light on our own planetary neighborhood.

“It’s telling me that the solar system isn’t some fluke,” says Josh Winn, an associate professor of physics at MIT and a co-author on the paper. “The fact that the sun’s rotation is lined up with the planets’ orbits, that’s probably not some freak coincidence.”

Setting the record straight on orbital tilts

Winn says the team’s discovery may back a recent theory of how hot Jupiters form. These giant bodies are named for their extremely close proximity to their white-hot stars, completing an in mere hours or days. Hot Jupiters’ orbits are typically off-kilter, and scientists have thought that such misalignments might be a clue to their origins: Their orbits may have been knocked askew in the very early, volatile period of a planetary system’s formation, when several giant planets may have come close enough to scatter some planets out of the system while bringing others closer to their stars.

Recently, scientists have identified a number of hot Jupiter systems, all of which have tilted orbits. But to really prove this “planetary scattering” theory, Winn says researchers have to identify a non-hot Jupiter system, one with planets circling farther from their star. If the system were aligned like our solar system, with no orbital tilt, it would provide evidence that only hot Jupiter systems are misaligned, formed as a result of planetary scattering.

Spotting sunspots in a far-off sun

In order to resolve the puzzle, Sanchis-Ojeda looked through data from the Kepler space telescope, an instrument that monitors 150,000 stars for signs of distant planets. He narrowed in on Kepler-30, a non-hot Jupiter system with three planets, all with much longer orbits than a typical hot Jupiter. To measure the alignment of the star, Sanchis-Ojeda tracked its sunspots, dark splotches on the surface of bright stars like the sun.

“These little black blotches march across the star as it rotates,” Winn says. “If we could make an image, that’d be great, because you’d see exactly how the star is oriented just by tracking these spots.”

But stars like Kepler-30 are extremely far away, so capturing an image of them is almost impossible: The only way to document such stars is by measuring the small amount of light they give off. So the team looked for ways to track sunspots using the light of these stars. Each time a planet transits — or crosses in front of — such a star, it blocks a bit of starlight, which astronomers see as a dip in light intensity. If a planet crosses a dark sunspot, the amount of light blocked decreases, creating a blip in the data dip. 

“If you get a blip of a sunspot, then the next time the planet comes around, the same spot might have moved over here, and you’d see the blip not here but there,” Winn says. “So the timing of these blips is what we use to determine the alignment of the star.”

From the data blips, Sanchis-Ojeda concluded that Kepler-30 rotates along an axis perpendicular to the orbital plane of its largest planet. The researchers then determined the alignment of the planets’ orbits by studying the gravitational effects of one planet on another. By measuring the timing variations of planets as they transit the star, the team derived their respective orbital configurations, and found that all three planets are aligned along the same plane. The overall planetary structure, Sanchis-Ojeda found, looks much like our solar system.

James Lloyd, an assistant professor of astronomy at Cornell University who was not involved in this research, says that studying planetary orbits may shed light on how life evolved in the universe — since in order to have a stable climate suitable for life, a planet needs to be in a stable orbit. “In order to understand how common life is in the universe, ultimately we will need to understand how common stable planetary systems are,” Lloyd says. “We may find clues in extrasolar planetary systems to help understand the puzzles of the solar system, and vice versa.”

The findings from this first study of the alignment of a non-hot Jupiter system suggest that hot Jupiter systems may indeed form via planetary scattering. To know for sure, Winn says he and his colleagues plan to measure the orbits of other far-off solar systems. 

“We’ve been hungry for one like this, where it’s not exactly like the solar system, but at least it’s more normal, where the and the star are aligned with each other,” Winn says. “It’s the first case where we can say that, besides the .”

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vega12
not rated yet Jul 25, 2012
I'm curious as to what the time scales are of the planetary transit periods compared with the movement of sunspots (using our Sun as a base for example). Also, if all the planets are moving in the same plane, that might bias your sampling of sun spots to only ones in the plane. I'll probably have to check out the article itself to see what the team did about this, but an interesting study nonetheless.
Osiris1
1 / 5 (1) Jul 26, 2012
Could it be that systems like our sun's are the norm for newly formed systems, and for systems that are stable, but the plethora of 'hot jupiters' may make a case for intervention into stable systems by rogue planets, even rogue jupiter sized ones or larger. Such intervention may have destabilized many systems, leaving idiotic and/or chaotic excuses for systems in their wake. This also leaves possibility for stellar and/or black hole interventions as well. Such would have to be rare however, although our Milky Way has 'captured' several dwarf galaxies including the Sagittarius Dwarf Galaxy of which our system has been postulated as being part of, since for one thing our local group appears to be in an inclined orbit, and maybe even an elliptical one about the Milky War galactic center. That is why we cross thru an arm of the Milky Way every 65 millions of years and are due to be crossing it now. Such crossing usually results in large collision events and other nasties.
Anda
5 / 5 (1) Jul 26, 2012
U don't need rogue planets for this osiris, as stable systems aren't stable forever.
antialias_physorg
5 / 5 (2) Jul 26, 2012
The usual explanation why everything is in a plane is that when you have other planets around whenever one goes above the plane th net gravitational vector from all the others will point downward (and vice versa)

But aren't these 'Hot Jupiters' really massive? Could they not resist this averaging effect much longer than other planets?
Being as they are probably the most prominent gravity factor in the system, anyhow - aside from the central star which doesn't contribute to averaging effect...and having scooped up any dust close to them (i.e. no planets in close by orbits that could have a marked effect).
vega12
not rated yet Jul 26, 2012
That's a good point about the massive planets being more "resistive". Interesting thought. But I have one small point to add. The gravitational vector going down is not enough to create planar motion, but that coupled with friction during the passing through the disk/cloud is what can cause such uniform planar motion from what I understand.
antialias_physorg
5 / 5 (1) Jul 26, 2012
Very massive bodies should be pretty good at clearing up the dust in their lanes. Hot Jupiters are also close to the parent star. Radiation pressure from the star should also clear the inner part of the solar system of any remaining dust (at least as compared to further out). So I would expect this 'passing the dust disc'-effect to be somehwhat less for them than for, say, an Earth sized planet further out.

Then there's the issue of how much braking force is applied. A hot Jupiter has a larger effective area that passes through a dust disc - proportional to r squared - the trasnmitted braking force is therefore also proportional to r squared.
But its momentum is propotional to r to the third power (proportional to mass - i.e. volume). So in comparison to smaller planets the relative loss of momentum is less.

(Countering this would be the fact that such planets close to stars pass though the disc more frequently but the ratio of r squared to r cubed feels still way more important)
Torbjorn_Larsson_OM
not rated yet Jul 26, 2012
This work seems a bit oversold.

- Good alignments and better than the solar system has been found before. (E.g. Kepler-11; http://en.wikiped...epler-11 )

- Retrograde hot Jupiters already shows that they can migrate.

However, it is a new promising technique, and likely the aligned system is much larger than earlier such and comparable in size with our own. Exciting!
Torbjorn_Larsson_OM
not rated yet Jul 26, 2012
@ Osiris1:

Our own system fits best a tumultuous start, with a Nice theory (a resonance between Jupiter & Saturn, throwing Neptune and Uranus further out and initiating the Late Heavy Bombardment), a Great Tack (having J&S initially migrating inwards before S caught up and stopped J) and a 5th expelled giant (allowing U & N to growth large by an initially thicker disk). It predicts upward of tens of different observations of our system (size, asteroid belt and its parameters, Kuipers and their parameters, captured moons, diverse Trojans and their parameters, et cetera).

The reason planets align is because they can exchange eccentricity for inclination by interactions, and those interactions cool (in the thermodynamical sense) the system over time. (Kozai mechanism.) But above all, the system can settle a lot before the ring disappears as already described here, by having smaller bodies act as frictional forces (gravity braking, as they pass).
Sonhouse
not rated yet Jul 26, 2012
Nobody has mentioned the actual distance of the planets from its parent star. Are they close to a goldilocks zone? Also, is that star similar to ours in energy output? Like at 1 AU, our sun puts out about 1350 watts per meter squared. What would that star put out?
Modernmystic
not rated yet Jul 26, 2012
Nobody has mentioned the actual distance of the planets from its parent star. Are they close to a goldilocks zone? Also, is that star similar to ours in energy output? Like at 1 AU, our sun puts out about 1350 watts per meter squared. What would that star put out?


http://kepler.nas...pler30c/

Short answer to the goldilocks question is no.
kevinrtrs
1 / 5 (6) Jul 26, 2012
In our solar system, the trajectory of the planets is parallel to the rotation of the sun, which shows they probably formed from a spinning disc,

Except of course for the hideous exceptions that are contrary to this idea:
1. The axis of sol is tilted 7 degrees relative to the plane of the planets.
2. Most of the angular momentum is not found in the sun as it should be if the above were true, instead is found in the planets - notably Jupiter.
3. Jupiter spins around its axis in 10 earth hours. How can this amount of energy be gained from a cloud of dust?
4. Uranus is rolling along like a top on its side. Whhat exactly is there in a disc that could impart such a motion to a body as big as Uranus. PLUS - all its moons are orbiting quite happily as they would be expected to.

Perhaps this little quip made by the researcher should be taken with a spade of salt. The actual, real, physical observations contradict it completely.
Torbjorn_Larsson_OM
not rated yet Jul 26, 2012
Creationists should comment on science, it is hilarious!

First the Other Troll blathered it, now the Resident Evil blathers the same thing in the same day.

The disk model is the accepted model of early protoplanetary systems, and it is plenty observationally verified. How ignorant must you be to implicitly claim that it isn't mainstream?

Or to discuss the early system with its migrating planets as how it looks today? In the modern Nice theory with Grand Tack, Jupiter and Saturn where tacking down towards 2 au before Jupiter was turned around and the resonance scattered the system. NT w ejected 5th giant predicts 20ish observations on the system (size, asteroid belt and its parameters, size and orbits of J/S/U/N, diverse trojans and their parameters, Kuipers and their parameters, et cetera).
Shifty0x88
not rated yet Jul 27, 2012
"Their orbits may have been knocked askew in the very early, volatile period of a planetary systems formation, when several giant planets may have come close enough to scatter some planets out of the system while bringing others closer to their stars."

Maybe this is where some rogue planets come from, or some rogue planet caused this, possibly both.
Modernmystic
1 / 5 (3) Jul 27, 2012
Creationists should comment on science, it is hilarious!


Is it hilarious? Why? Share the joke.
Torbjorn_Larsson_OM
3.7 / 5 (3) Jul 29, 2012
@ Modernmystic:

Mostly because it is funny how they misunderstand the simplest and most well known facts or methods.

But it is also fundamentally a joy to observe how they attempt to use creationist 'science' to 'refute' science instead of just be forthright with that they are unhappy with observed reality and prefer to make shit up.
Modernmystic
not rated yet Jul 30, 2012
Mostly because it is funny how they misunderstand the simplest and most well known facts or methods.


How is another human being's misunderstanding or ignorance funny? Do you really need that kind of immature humor to make yourself feel smart, or important, or superior?

Would you find it funny if someone slipped on the ice and broke a leg?
Modernmystic
not rated yet Jul 30, 2012
As an aside, how do you ever expect them to learn if all they get is snide comments, and invitations not to express themselves? Do you want to continue to deal with creationism and creationists? How do you think they'll best respond to you? If you humiliate them? How's that been working out?