DOUBLE FEATURE: An artist's illustration of the alien solar system Kepler 47, a twin star system that is home to two planets. The planets have two suns like the fictional planet Tatooine in the Star Wars universe.
Image: NASA/JPL-Caltech/T. Pyle
The more stars a system of alien worlds starts with, the more likely those planets will orbit those stars at odd tilts, scientists say.
The discovery, based on a study unveiled Nov. 14, suggests that even Earth's own sun may have had a companion star early in its development.
In recent years, astronomers have detected hundreds of exoplanets — worlds circling distant stars. Many of these are "hot Jupiters" — gas giants like Jupiter or Saturn that are closer to their stars than Mercury is to the sun.
Researchers had thought hot Jupiters arose when giant planets were dragged inward by protoplanetary disks of gas and dust falling toward stars. However, this idea was recently cast into doubt by the surprising discovery that a major fraction of hot Jupiters have orbits that are tilted in respect to their stars' rotation.
Stars all spin, just as Earth's does, and their worlds often line up with this spin — they orbit around the equators of their stars and revolve in the same direction. However, sometimes alien planets have misaligned orbits instead, ones that are at slight or even sharp angles around their stars. The orbits of some exoplanets are so far tilted that they are actually backwards — they move in retrograde orbits in exactly the opposite direction of their stars' spin.
Scientists had thought if hot Jupiters were dragged toward their stars by protoplanetary disks, they would all end up in relatively normal orbits around the equators of their stars. However, astronomers recently discovered that a whopping 25 to 50 percent of these planets actually may have misaligned orbits.
"The misalignments seemed to point towards a much more volatile, violent evolutionary path for hot Jupiters," said study author Konstantin Batygin, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics.
For instance, perhaps it was a gravitational tug of war between exoplanets that hurled some inward at their stars. Still, it seemed unlikely such processes were responsible for all these misaligned planets.
"A crude and oversimplified analogy is taking a machine gun, shooting in every direction possible, and hitting the correct target about 1 percent of the time," Batygin said. "Surely not impossible, but it seems unlikely."
Now Batygin has discovered protoplanetary disks can indeed produce such tilted orbits if these systems each harbored multiple stars. [Photos: Alien Planet With Twin Suns Found]
Although the solar system has only one sun, most stars like Earth's sun are binaries— two stars orbiting each other as a pair. Increasingly, astronomers are discovering planetary systems with twin suns (like Luke Skywalker's fictional home planet Tatooine in "Star Wars"). There are also many three-star triples in the universe, at least one of which is known to host planets, and the number of stars a system has can even climb as high as seven.
Through computer modeling, Batygin found that the complex system of gravitational pulls that binary stars exert on protoplanetary disks would disrupt them enough to misalign the disks. He added that the more stars a system has, the more likely its planets orbits would be tilted.
This idea does not require that a system have multiple stars for billions of years, Batygin added.
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7 Comments
Add Comment"Batygin noted the orbital plane of the solar system's planets is misaligned from the sun's equatorial plane by 7 degrees. Given this skew, "I think it is safe to say that the solar system falls into the misaligned category." In other words, the sun once may have had a companion star very early in its history."
Reply | Report Abuse | Link to thisIt's actually only the Earth's orbit that is inclined by 7 degrees in relation to the Sun's equator. The other planets' orbits have less inclination, especially the two nearest the Sun.
http://en.wikipedia.org/wiki/Invariable_plane
details the orbital inclination of each planet in relation to the Sun's equator. The Earth's inclination is greater than any other Solar system planet, nearly twice that of Mercury and Venus. The inclination of more distant planets is generally around six degrees.
I suggest that the inclination of Earth's orbit was produced by the same giant impact hypothesized to have created the moon - that a Mars sized protoplanet ('Theia') collided with the early Earth. Presuming the giant impact event, this explanation seems far more plausible than a lost star that is otherwise not in evidence. Exoplanetary systems' wild orbital configurations might be the product of the violent ejections of companion stars, but the minor inclinations of the Solar system are more reasonably the product of planetary interactions.
From the Solar system's planetary inclination information I suggest than not only was the Earth's orbital inclination the product of the 'giant impact', but that perturbation also affected the orbits of all other planets. The Earth's perturbational influence would have been greatest for more distant planets, since the inner planets are more stabilized by the proximity of the Sun's enormous mass.
Mr. Dyer, shame we won't be here when the Milky Way and Andromeda pass through each other and begin the deadly dance that ends in an Elliptical Galaxy. At that point who knows who our Sol will be dancing with and and what planets may be tossed out beyond the reach of a stellar warmth.
Reply | Report Abuse | Link to thisWe hardly realize how lucky we are to be here now and in a short period of 1 billion years as the oceans boil away only the extremophiles and underground organisms that may last long enough to be here for that show. But at least we know it is coming and thanks to our astronomical tools we can see how the dance works.
We are lucky to be able to have these conversations and we take so much for granted. :) Miss you Jim, hope all is good.
Thanks you, sir - I appreciate your kind sentiments. I only hope that my living grandchildren will be able to live a satisfactory life on what's left of this planet.
Reply | Report Abuse | Link to thisBest wishes!
Jim if you get a chance you may well enjoy the book 'Waking the Giant' by Bill McGuire. It discusses how the Earth is somewhat of a self sustaining harbor for life. I have often thought to find life in the Solar system and beyond, look for interesting chemistry. Anyway here is the link to the overview https://www.kirkusreviews.com/book-reviews/bill-mcguire/waking-giant-changing-climate/ . I read a lot of Freeman Dyson and he was of the same mind set that GAIA is what we live on and the feed back loops are what sustains us and what allows for change and new niches for evolution to keep working. I think you will enjoy it and we are seeing the chickens come home to roost.
Reply | Report Abuse | Link to thisI really think it is too late to stop the coming changes but with proactive responses instead of knee jerk reactive responses we can survive. The Earth has sustained CO2 levels of 1,000 PPM and we are only approaching 400 ppm. The Earth has also been much hotter with sea level some 120 meters higher than current.
But with that in mind and the fact that nearly 75% of the human population lives near water we do need to think ahead. Trying to fix it with artificial steps (Sulphates or Aluminum strips could lead to wars) and still not have effects we desire.
What I fear is Cascadia, Yellowstone, the Canary Island, the Ice Sheets of Greenland, Antarctica and many of the sleeping giants that were once violent volcanoes are about to wake from their slumber.
That's an interesting point - what effect the shift of ice mass at high elevations to water mass at low elevations might have on tectonic activity...
Reply | Report Abuse | Link to thisThere's no precedence for mass migrations involving billions of people, but prospects are not good. I suspect the Earth will rebound in the long run, but the nature of its flora and fauna will likely be changed.
Best wishes to all...
"The misalignments seemed to point towards a much more volatile, violent evolutionary path for hot Jupiters,"
Reply | Report Abuse | Link to thisYes, indeed; and the reason is fundamentally a simple one - fragmentary birth of stars and large planetary bodies in the cosmos, as opposed to an accretionary mechanism; but kindly hear me out here.
"Based on computer simulations Mark Krumholz from Princeton University, Christopher McKee from the University of California at Berkeley, and Richard Klein from Berkeley and Lawrence Livermore National Laboratory now claim [Nature 438, 332-334 (2005)] that the bottom-up theory is incorrect because the seeds cannot grow fast enough during the lifetimes of the clouds to reach typical star sizes. …
'Our result is that the bottom-up idea doesn't work,' Krumholz told PhysicsWeb, 'because seeds can't accrete quickly enough to grow to stellar masses within the lifetimes of the clouds out of which they are born. Instead, stars form by fragmentation, and the fragmentation process determines their masses.'
The results also explain, the team says, why observations suggest that objects as different as small brown dwarfs and massive stars have a common formation mechanism. In contrast, the accretion model involves different mechanisms for making objects with different masses. A universal formation process might also explain why the mass distribution of newly formed stars – the initial mass function – seems to be constant throughout our galaxy and other galaxies.
'Many earlier simulations of star formation processes made a significant error because they modelled environments with properties that are very different from those observed,' says Krumholz. 'A lot of these simulations are now going to have to be reconsidered and probably re-done.'"
How do stars form? Belle Dumé, PhysicsWeb, 16 November 2005.
Please see also: http://www.sittampalam.net/StarFormation.htm
Now, stars generally appear as binaries, ternaries, and so on in a star cluster; and should the smallest member in any such multi-star group fail star-billing, it would be seen as a 'Hot Jupiter' as the one in the article here.
Thus, our own Jupiter and even Saturn could well be splinters from the early, violent and volatile Sun!
See: http://www.sittampalam.net/TheSun.htm
Thank you all for the time.
www.toe.tv
Here's another observational fact out there in support of my above comment:
Reply | Report Abuse | Link to this"Astronomer spies improbable world with three suns. Meet the impossible planet. This world nestles inside a system containing three stars that, according to current theories, should have denied it the chance to develop. But..."
The triple sunset that should not exist, Mark Peplow, News@Nature, 11 July 2005
Please see also: http://www.sittampalam.net/TheQuaternary.htm
Thank you all, and Cheers!