Eccentric Orbits and Bold Predictions

by Paul Gilster on April 28, 2009

The 100th edition of the Carnival of Space is now up at the One-Minute Astronomer site, where I learned of the existence of Christopher Crockett’s Innumerable Worlds blog. Christopher’s story on two gas giants around subgiant stars is well worth reading. He’s a UCLA graduate student now working at Lowell Observatory who offers a good deal of background material in his posts, as in this comment on the new planets’ unusually eccentric orbits:

How planets end up on such crazy orbits is a matter that is currently being researched. These two worlds aren’t alone; many of the new worlds we’re finding sit on highly eccentric orbits. The leading hypothesis is that interactions between closely spaced planets might affect their orbits. If two planets get too close, the lighter one can get ejected from the planetary system entirely while the remaining, more massive, world is left behind on a very elliptical orbit. This is the same principle we use to slingshot probes out into deep space by stealing momentum from the planets. We may be seeing the remnants of long-past interplanetary bumper cars!

Interesting stuff, and it raises the issue of how many star-less planets might be wandering interstellar space. Not enough, according to recent studies, to explain the evident dark matter halo around the average galaxy, but enough to offer up a great deal of interesting real estate if we find that planetary ejection really is common.

Lots of good material on the latest Carnival besides this, including Brian Wang’s Projecting 250 years to a Star Trek Timeframe, which is packed with intriguing calls on population (89 billion by 2260) to the economy, with Brian’s usual set of useful links. One interesting possibility: A civilization reaching 100-200 light years in radius within 250 years. Also be sure to check astroENGINE‘s speculative piece on METI (transmitting to the stars) and Orbital Hub‘s Q&A session with alien hunter Seth Shostak, author of the recently released Confessions of an Alien Hunter.

{ 18 comments }

Ian O'Neill April 28, 2009 at 17:52

Hi Paul! Thanks for the link :) Glad you liked my METI-Twitter idea… perhaps I could get some research funding for that… ;)

Cheers! Ian

Ian O'Neill April 28, 2009 at 17:53

And I’m liking the new design of the site… I just realised there was a subtle change in the design – very nice :)

Administrator April 28, 2009 at 18:34

Always glad to hear from you, Ian, and loved the Twitter concept re METI! Thanks for the thoughts on the re-design, which was a long time coming, but something I’ve been needing to do. The server problem that happened last week really hastened my work on it.

Ian O'Neill April 28, 2009 at 19:23

Lol, same thing happened to me last week with Astroengine – server died, needed an urgent upgrade, so I threw a redesign in too :)

I like the clarity of CD now, a very open feel to it. Keep up the awesome work, loving the articles still!

Cheers, Ian

Administrator April 28, 2009 at 19:59

The blue artwork on Astroengine looks sharp indeed, and I have to say that your coding skills are far more accomplished than mine. Still, it’s fun to tweak things for maximum effect, a never-ending process.

bigdan201 April 28, 2009 at 23:59

ive thought of the possibility that there are planets floating through space without a star to orbit, due to ejection like you described. they would naturally be pretty cold, but theyd definitely be interesting real estate.

not sure what to say about dark matter.. its just an indicator that we still have much to learn about the universe. whether its a different form of matter that doesnt interact much with normal matter, or if theres a normal matter explanation for it, only time will tell.

CosmicThespian April 29, 2009 at 1:17

Thanks for the link to my article. My struggling little blog just got the biggest one day spike in traffic yet! I’m glad you found the article interesting; hopefully you’ll find future articles just as worthy.

Cheers,
Christopher

keith April 29, 2009 at 7:52

I’d like to make a kind of side-comment about the blog linked to: I don’t like the general assumption about planets being more common around high-metallicity stars. Now if you are a professional astronomer who wishes to maximise your chances of finding a planet, you will look for high metallicity: fine, what you will find are huge mis-behaving super-Jupiters like this.

I’d like to caution that many planet forming models predict that terrestrial planets are more likely in low-metallicity systems. The density of planet kernals around high metallicity stars leads a few huge masses mopping up all available kernals in short order. With low metallicity, in contrast, the kernals persist with fewer mergers, leading to a larger number of small planets (and no inward-wandering hot super-Jupiters).

One model predicts that there may be hundreds of planets per star formed in the low-metallicity stars of a globular cluster (many of which get ejected by close encounters with other cluster stars). The optimum metallicity for terrestrial planet formation could turn out to be less than the sun’s metallicity.

Administrator April 29, 2009 at 9:27

CosmicThespian, glad to hear of the traffic spike! And always glad to find new blogs exploring exoplanet science. We’re truly living in a golden age of discovery.

Administrator April 29, 2009 at 9:28

Keith writes:

I’d like to caution that many planet forming models predict that terrestrial planets are more likely in low-metallicity systems.

Good point. We do have a lot less information about metallicity and terrestrial planet formation than with regard to gas giants. Much to learn on this.

kurt9 April 29, 2009 at 11:44

Having followed this and other exoplanet blogs for the last couple of years, it appears that higher metallicity corresponds with larger in-system planets. The huge Jupiters they have found are mostly in high metallicity systems. The higher the stellar metallicity, the bigger the Jupiter. However, this correlation is not so apparent for Neptune and smaller planets, although there is not enough data to make meaningful statistical inferences on this.

It is worth noting that the 3 red dwarfs that have had planets found around them are all of lower metallicity than the sun. All three of these have multiple planets closer to Earth-size than most other findings.

Computer simulations are useful. But they must always be backed by actual observation.

ljk April 29, 2009 at 12:01

An important point has been missed in that article on the Star Trek
timeline, an error that has not been corrected in over 40 years.

The original ST series did not take place in the 23rd Century but the
22nd Century. Proof of this comes from such direct sources as the
episode “Tomorrow is Yesterday”, when the USAF officer who captures
Kirk in 1969 says he is going to lock him up for 200 years, and Kirk
replies that would be just about right. 1969 plus 200 is 2169.

Kirk told Kahn in “Space Seed” that he had been in suspended animation
aboard the SS Botany Bay for about two centuries. Khan left Earth in
the year 1996. There was also a comment made in this episode that they
no longer needed sleeper spaceships after advances made in 2018, FWIW.

In the third season episode “The Savage Curtain”, the image of Abraham
Lincoln is told he is 300 years from his time. 1865 plus 300 equals 2165.

In the episode “Wolf in the Fold”, the years of when a malevolent creature
conducted a series of murders throughout the galaxy are given, which
include a Martian colony in 2105 and the last at Alpha Eridani II in 2156.

Of course the timeline has been firmly established as the 23rd and 24th
Centuries ever since despite these original series dates, so it probably
won’t matter now, but as a one-time Trekker I felt it is my duty to inform
the public on this discrepancy.

Oh for the days when 1996 seemed like such a distant future time.

keith April 30, 2009 at 7:54

kurt9, I fully endorse your view that computer models need to be validated by actual observations. It’s also good to see that, so far at least, the evidence is certainly not stacked up against the idea I was trying to get across.

Brian Wang May 2, 2009 at 17:58

the fifth live action TV series Enterprise quoted years and not star dates. TV series is clearly canon.

http://memory-alpha.org/en/wiki/Star_Trek:_Enterprise

2151-2155.

Archer’s enterprise in one century before Kirk and Spock.

Many books and shows and dedicated online sources confirm the dates. Kirk and Spock are 23rd century.
http://memory-alpha.org/en/wiki/Five-year_mission
2265-2270 Five year mission of Kirk and Spock

I believe the newest movie to be release in a few days will go a bit earlier with an altered time-line. Pike is still Captain and events in the movie have Kirk taking command, I think this will happen before the 2264 of the old timeline. The actors look younger. I am guessing 2259-2261.

James Tiberius (“Jim”) Kirk was a Human born on March 22nd, 2233 (Stardate 1277.1), in Iowa on the planet Earth. (TOS: “Where No Man Has Gone Before”, “The Deadly Years”; Star Trek IV: The Voyage Home; ENT: “In a Mirror, Darkly, Part II”). At 31 years of age in 2264, he was promoted to captain. Christopher Pike was captain of the starship USS Enterprise from 2251 to 2264, as the successor of Robert April and immediate predecessor to James T. Kirk.

By 2250, Kirk had returned to Earth, ready to begin his Starfleet training. With some assistance from a man named Mallory, he was accepted into the Starfleet Academy in San Francisco.

As a young lieutenant in 2255, Kirk was assigned to command his first planetary survey mission, on Neural. Kirk met and befriended one of the planet’s natives, the Hill man Tyree. His report described a primitive but promising culture, and Starfleet endorsed his recommended policy of non-interference. (TOS: “A Private Little War”)

http://memory-alpha.org/en/wiki/In_a_Mirror,_Darkly_(episode)
This drew the USS Defiant of 2268 to the rift.

Administrator May 3, 2009 at 13:18

I stand in awe of both ljk and Brian, whose knowledge of Star Trek arcana can hardly be equaled anywhere. I plan to see the new film next week, so we may have some further ST talk soon.

ljk May 3, 2009 at 21:20

By the time Enterprise came along, the 23rd/24th Century dates
had been established and the evidence I produced above was
ignored and/or misinterpreted.

So I reject the Enterprise dates, even though it will do me no good,
plus that last series is why the new film is coming out to save a
dying franchise.

Ronald May 4, 2009 at 4:53

With regard to keith and kurt9: as with temperature, it looks like if there could be a kind of Goldilocks zone for metallicity as well: to low (below about 1/3 to 1/2 of solar) and all you get is dust and asteroids, too high (above 1.5 to 2 x solar) and you get hot Jupiters. Of course, this is very (VERY) preliminary.

Optimum metallicity for terrestrial planets in stabel orbits may indeed be a bit lower than solar, just as the optimum luminosity for a life-giving solar star maybe a bit lower.

We often (in fact usually) observe in nature, that our conditions are somewhat below or beside optimum.

ljk July 2, 2009 at 15:14

Which Radial Velocity Exoplanets Have Undetected Outer Companions?

Authors: Timothy J. Rodigas, Philip M. Hinz

(Submitted on 30 Jun 2009)

Abstract: (Abridged) The observed radial velocity (RV) eccentricity distribution for extrasolar planets in single-planet systems shows that a significant fraction of planets are eccentric ($e > 0.1$). Here we investigate the effects on an RV planet’s eccentricity produced by undetected outer companions.

We have carried out Monte Carlo simulations of mock RV data to understand this effect and predict its impact on the observed distribution. We first quantify the statistical effect of undetected outer companions and show that this alone cannot explain the observed distribution. We then modify the simulations to consist of two populations, one of zero-eccentricity planets in double-planet systems and the other of single planets drawn from an eccentric distribution.

Our simulations show that a good fit to the observed distribution is obtained with 45% zero-eccentricity double-planets and 55% single eccentric planets. Matching the observed distribution allows us to determine the probability that a known RV planet’s orbital eccentricity has been biased by an undetected wide-separation companion.

Our simulations show that moderately-eccentric planets, with $0.1 < e < 0.3$ and $0.1 < e < 0.2$, have a $\sim 13%$ and $\sim 19%$ probability, respectively, of having an undetected outer companion.

We encourage both high-contrast direct imaging and RV follow-up surveys of known RV planets with moderate eccentricities to test our predictions and look for previously undetected outer companions.

Comments: 23 pages (12 text, 2 tables, 9 figures). Accepted to the Astrophysical Journal 30 June 2009

Subjects: Earth and Planetary Astrophysics (astro-ph.EP)

Cite as: arXiv:0907.0020v1 [astro-ph.EP]

Submission history

From: Timothy Rodigas [view email]

[v1] Tue, 30 Jun 2009 20:20:58 GMT (280kb)

http://arxiv.org/abs/0907.0020

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