It’s the simple formula we all know and recognize: inner, rocky worlds closest to the Sun, an asteroid belt farther out, and then gas giant worlds out beyond them. That’s how our Solar System works, at any rate. But what about the other star systems in the Universe?

Confirmed planets as of September 2014. Credit: PHL @ UPR Arecibo.

Confirmed planets as of September 2014. Credit: PHL @ UPR Arecibo.

We’ve finally got enough data to determine whether other planetary systems are like us or not, and if not, how common (or uncommon) our configuration actually is. But what’s also interesting is that despite the tremendous computational power needed, simulations are finally catching up to the data, too, allowing us to understand why the results are what they are.

Computer Simulation of a protoplanetary disk. Credit: W. Kley, R.P. Nelson.

Computer Simulation of a protoplanetary disk.
Credit: W. Kley, R.P. Nelson.

Come learn how special our Solar System truly is, thanks to Brian Koberlein!

Comments

  1. #1 Sean T
    March 31, 2015

    How much does selection bias affect the conclusion that our solar system is unique. IIRC, it’s much easier to detect planets that are closer to their parent stars and it’s easier to detect more massive planets. This seems to be borne out by the statistics on the confirmed planets as shown in the figure in the article. If I did the math right, approximately 93% of the confirmed planets are “superterrestrials” or heavier (126 out of 1812), and approximately 80% (361 out of 1812) are in the hot zone. Would we be able to reliably detect a solar system that is like ours?

  2. #2 Sean T
    March 31, 2015

    Sorry, I meant to use the same terminology that is used in the article, so I should have typed “superterrans” in place of “superterrestrials” in my post above. My question still stands, though.

  3. #3 Tom Campbell-Ricketts
    March 31, 2015

    Along similar lines to Sean T’s question:

    I wonder if the graphic near the top, showing the distribution planets per system might also owe something to selection bias. The graphic shows more than twice as many single-planet systems found than doubles, and so on. But both transit & stellar wobble methods must suffer some reduced sensitivity in cases with higher numbers of planets. As a simple example, if 2 massive objects circle a star in perfect anti-phase, then the Doppler signal ought to be weaker that what would manifest if one of the objects was magically removed, as the 2 together pull the star in opposite directions. With larger numbers of planets, the effect ought to be even worse.

    Ditto for the transit method – if there are many planets, then the brightness of the star ought to be more constant. In the extreme limit – on average – each planet that passes out of one limb, tending to increase the brightness of the star, will be simultaneously replaced by another planet entering the other limb.

    Has there been a good analysis of the magnitudes of these biases? Has anybody estimated a corrected version of the depicted distribution?

  4. #4 Ruan de Witt
    South Africa
    March 31, 2015

    This is fascinating. To think that our solar system actually is different from most solar systems out there. It kind of makes us feel special. It really makes one think of our place in the universe.
    15099157

  5. #5 David Andrews
    United States
    March 31, 2015

    Very interesting!
    In the dynamics of system formation, a migrating giant like Jupiter introduces variables that remind me of a roulette wheel, anything can happen… Like flinging mars sized planitoids around.
    Models and observations suggest the serendipity of a 3:2 resonance between giants that induced the migration rearrangeing our system is rare.
    I wonder about the implications such dynamics have on the formation of a system conducive to biological development.

    Looking at Venus, so near to Earth in mass and inside the habitable zone. Why so very different?
    It occurs to me that a major distinction is – our moon.
    What if it took a collision with a mars-sized object wiping away half of the primordial atmoshpere to set the stage for a habitable world?
    So many possible variables influencing system evolution, it could be that planets capable of supporting life require a specific set of events to occur, and are far more rare than we imagined.
    Thank you for you time!

  6. #6 Theo Hohls
    March 31, 2015

    Is this source of information really reliable?? considering the information we know about such called “dead stars” whereby light incoming from these stars a still on their way despite this star being dead for years can we conclude that maybe a solar system like ourselves did exist there near to that star or with a billionth mile region? Also it can be questioned as to why larger planets are the only ones being considered as they are the only ones being detected at a habit level due to the distance of the planets from our own!! very interesting topic to debate about however and cannot wait to find out more and the possibility of solar systems that might actually be similar to our own – 15016677

  7. #7 Vincent Mc Kinnon
    south africa
    March 31, 2015

    It is just amazing how awesome our solar system is and how diverse a network of solar systems there (not to mention galaxies !). To add on to Theo Hohls, how can we really trust the reliability of these statements and even start to imagine what possible outcomes there might be to all the test and all the variables that affect the outcome of each test ?
    Maybe one day we will know the mysteries that lie in our universe … Good job professor Brian, loved the article !

  8. #8 Omega Centauri
    March 31, 2015

    Is something like a 3:2 resonance really rare, or could it be the result of the migration of two gas giants, once they reach a resonance the dynamics of the interaction changes, then??

    I saw something a couple of months back. Astrobiologists make a big deal out of needing plate tectonics to recycle materials important for life, and we think we need enough Uranium in the core to power mantle convection. Now I saw a paper that looked at a rare isotope of Plutonium in sea floor sediments. This is supposedly a tracer for heavy elements in the interstellar gas, and there was a couple of orders of magnitude less than expected. The speculative conclusion: maybe core collapse supernovas, can’t create heavy ( atomic number >>56) elements, and only neutron star mergers are violent enough. Perhaps the nebula that formed the sun had been enriched by a nearby NS merger event, and most planetary systems have very much less heavy elements?
    [ I’m not convinced something like tidal heating might not also allow plate tectonics]

  9. #9 Birger Johansson
    March 31, 2015

    Systems with higher metallicity tend to look different from our system (superterrestrials, hot Jupiters).

    Selection bias really kicks in against terrestrial planets orbiting G stars and will do so until we get even more sensitive instruments. Cold Jovians need decades of study to show up in the doppler signal.
    — —
    Since massive stars with a short lifspan are ubiquitous in large nebulas, the second generation of stars born from them will get plenty of uranium and other unstable nucleids from the supernovae, providing plenty of heat for planetary interiors.

  10. #10 PJ
    Perth, west Oz
    March 31, 2015

    Using the transit method of detecting the presence of planetary bodies around a star, what percentage of stars are we observing with potential planets versus those who’s orbit plane does not align with our position in space?

  11. #11 Omega Centauri
    March 31, 2015

    Birger Johansson
    My main point was it is not known whether SNs create the heavy elements. If they are only forged by NS merger events, they will be much rarer.

  12. #12 Michael Kelsey
    SLAC National Accelerator Laboratory
    March 31, 2015

    @PJ #10: That’s a great question. The radial velocity method of detecting exoplanets is sensitive to the orientation of the plane via the factor “sin i”, where “i” is the inclination angle. The transit method preferentially picks out i ~ 90 deg. You can estimate the range by considering a vaguely solar-systemish configuration.

    Take a Sun-like star, with a diameter of 1.5E6 km. Consider a planet in a 1 AU orbit (1.5E8 km). The star subtends an angle of 10 mrad, or 0.57 degrees. That’s the full range of inclination angle that a transit (for that size orbit!) will get you: +/- 0.28 deg.

  13. #13 Jim Moser
    United States
    April 1, 2015

    If Jupiter’s orbit moved from the position of Mars to that of Venus then back outward, shouldn’t our asteroid belt be considerably younger than our solar system? Jupiter would have cleared out smaller objects as its orbit shifted so today’s asteroid belt would have formed after Jupiter obtained its current orbit.

  14. #14 T. Duvenage
    April 1, 2015

    Wow, I definitely learned something new. It is amazing to think that our solar system is more like the exception and that the galaxy has 300 billion stars that all has the potential for life but so far we are the only living system. -15057357

  15. #15 Justin Zimmerman
    United States
    April 1, 2015

    PJ, I believe most of the planetary systems in our milky way lie on the same “galactic plane’, as do we.

  16. #16 Andy Eppink
    Lake Los Angeles
    April 1, 2015

    My Lord! It’s not obvious by this late God has Engineered our home, the Eatth, and everything surrounding it?
    Dumbbells.

  17. #17 Wow
    April 1, 2015

    What is obvious is that your claim is just your assertion, of no more validity than that of someone that they are, indeed, Napoleon.

  18. #18 S Makhwaza
    April 1, 2015

    Our earth is unique and it looks different because of its rocky and gassy planets and the changes between the two caused by planetary differences. Since scientific processes are continuous, is our solar system still changing, and is it possible that there will be another “bang” changing the solar system from what it is now?
    14258537

  19. #19 PJ
    Perth, west Oz
    April 1, 2015

    @Michael #12. Thanks Michael. I appreciate your response.

    @Justin #15. Since the plane of our solar system is inclined to the galactic plane by some 60 degrees, or so, probably the solar planes of other systems are at random inclinations to the galactic plane also. Ergo, the odds of finding planets in those systems which align with us are diminished even further.

  20. #20 PJ
    Perth, west Oz
    April 1, 2015

    Have a safe easter break, everyone.

  21. #21 Roland
    April 1, 2015

    Energy balance:
    So, Jupiter& Saturn first spiraled in. They must have given up energy to do that. Where did it go? Did it accelerate the surrounding material to the outer solar system? Did they spin up the Sun via tides?
    Then they spiraled out. This is the big question. Where did they get the energy to do that? Big planets, lots of energy. From where? Did they spin down the Sun somehow? That might work if they’re close in, but the effect would fade quickly.

  22. #22 EP Blignaut
    South Africa
    April 2, 2015

    Wow, this is truly amazing how unique our solar system works compare to other solar systems. I would really be updated on other solar systems similarities to that of ours. Do you think there are other solar systems just like ours? Thank you for this awesome fact.
    15076874

  23. #23 Sarah J
    South Africa
    April 2, 2015

    It is far too exciting that the advancement in technology has led to us being able to study other extraterrestrial bodies, planets and galaxies. Being able to study the similarities and differences between our galaxy and other existing galaxy will enable us to predict what type of life forms exist there and will also provide great support to theories stating that there could be other worlds out there in the universe. To what extent has research proceeded in proving that there are other life forms existing in the universe in other galaxies. Thank you for your time! 15007473

  24. #24 Joshua Ndoli(u15401104)
    Gauteng,Johannesburg
    April 2, 2015

    It’s fascinating to actually imagine this huge space filled system(our solar system), still and continues introducing new discoveries and aspects to Astronomic science.

    As a future scientist I truly believe, our knowledge of the solar system will not be limited by any factor.

  25. #25 Khanyisile Hlongwane
    Gauteng
    April 4, 2015

    It is wonderful to see that new discoveries are still coming to light as time goes by.This is an interesting topic because there is always something new to discover in regards to the solar system.

  26. #26 BD NHLAPO
    April 5, 2015

    It is studies like these that leave us more puzzled than provide answers. 14032164

  27. #27 15016669
    gauteng
    April 5, 2015

    its amazing how our world is but the funny thing is where on the universe is heaven located?

  28. #28 Joshua Ndoli (u15401104)
    Gauteng
    April 5, 2015

    Astronomy is wonder branch of science,which intrigues the soul to ask questions of how such beauty occurred.

  29. #29 Khanyisile Hlongwane
    Gauteng
    April 5, 2015

    When it comes to the question about heaven I am as curious as you are. (u15097367)

  30. #30 dean
    April 5, 2015

    …where on the universe is heaven located?

    That is not purely a science question, but: given the lack of scientific evidence in favor of a heaven, the answer would be “to the best of our knowledge, nowhere”

  31. #31 Mashaba FS-u13356004
    Pretoria
    April 5, 2015

    Dean and Khanyisile Hlongwane, heaven may be located in the universe(I do not know), but what I know is that it is a spiritual place, it cannot be located by human instruments like spaceships. Only the spiritual man can access it , not a man in a suit(body).

  32. #32 jacobus du plessis, 15037909
    April 6, 2015

    our universe are unique and all the stars and planets are placed exactly in the right place so that live can be present on earth. the question is where did the universe got energy from ate the start.? 15037909

  33. #33 Wow
    April 6, 2015

    No, the thing we know about heaven is that it doesn’t exist. There is no spirit, nothing living after death, death is the end of it. Stop fearing it and believing any old rubbish that pretends to tell you you’ll never die.

  34. #34 Arri.K
    April 6, 2015

    Is it safe to assume that all solar systems would resemble our solar system due to the Nebula Hypothesis? (u04541686)

  35. #35 Khanyisile Hlongwane
    Gauteng
    April 6, 2015

    Thanks for the response Mashaba and what you are saying really makes a lot of sense,you really answered my question. u15097367

  36. #36 Wilhelm Briers (u15080430)
    University of Pretoria
    April 6, 2015

    The solar system and all its content have always inspired me. There is so much to still explore and so much information that we have not gathered yet. It is truely special. The fact that there is more than just our solar system makes it even more mind wrecking and that is a great challenge for us to keep digging and searching for more information. I just really would like to know why there are so many elements on other planets that does not exist on Earth is it because of temperature difference or what? This article was really interesting.

  37. #37 Khanyisile Hlongwane
    Gauteng
    April 6, 2015

    It is really interesting to see that there are still new discoveries being made about our solar system and the universe as a hole.These discoveries however bring up more questions than answers but I guess that is a great thing because this makes room for more discoveries to be made.(u15097367)

  38. #38 U15054153
    April 7, 2015

    If Jupiter’s orbit moved from the position of Mars to that of Venus then back outward, shouldn’t our asteroid belt be considerably younger than our solar system? Jupiter would have cleared out smaller objects as its orbit shifted so today’s asteroid belt would have formed after Jupiter obtained its current orbit

  39. #39 U15054153
    April 7, 2015

    So, Jupiter& Saturn first spiraled in. They must have given up energy to do that. Where did it go? Did it accelerate the surrounding material to the outer solar system? Did they spin up the Sun via tides?
    Then they spiraled out. This is the big question. Where did they get the energy to do that? Big planets, lots of energy. From where? Did they spin down the Sun somehow? That might work if they’re close in, but the effect would fade quickly.

  40. #40 u15162258
    Pretoria
    April 7, 2015

    The good thing about this is that more is still to be revealed and discovered.

  41. #41 Mamobu Mabunda
    Jane Furse
    April 7, 2015

    What fascinates me most about our solar system is that it’s mystery is forever unfolding and there will never be a point when the human race has officially figured out everything about the solar system and all its twists and turns. It brings great joy to me to be part of a universe that is so unique and stands out from the rest, there is no place i would rather be☺. there is so much more to be discovered.
    u15053050

  42. #42 Khanyisile Hlongwane
    Gauteng
    April 7, 2015

    I do agree with you Mamobu, at some point we will eventually know everything about our solar system and the universe as a hole.However I think we are a long way from reaching that point as more questions are asked which lead to more discoveries. (u15097367)

  43. #43 u15025935
    Pretoria, South Africa
    April 8, 2015

    Absolutely intriguing. Bias can influence us to be believe it is special compared to others but it truly is a majestic solar system.

  44. #44 Mashaba FS-u13356004
    Pretoria
    April 10, 2015

    The complete picture of the solar system being discovered may take forever, because the more discoveries are made the more the questions with unknown answers yet to be discovered.

  45. #45 u15108342
    Pretoria South Africa
    April 11, 2015

    I’ve done some research on the Drake’s equation and Fermi paradox which deals with how many other earth like planets there are in the universe. It seems as if the first is much more popular even though most of the variables in the equation is still unknown and all known evidence supports the Rare Earth Theory. This questions the validity of Drake’s equation. Can it be viewed as a scientific formula or just science fiction?

  46. #46 T Masilonyane
    Pretoria
    April 14, 2015

    ‘The most intriguing is that planets can be formed by more than one mechanism and the assumption astronomers have made until now – that all planets formed in basically the same way – is a mistake.’ said Martin Beer about formation of planets in 2004. Its quite interesting to know that our solar system is different from others in the universe. it really proves how special our solar system is and the blog details that very well despite this being an explanation that is not easily quantifiable.
    15301983

  47. #47 D Wertheimer
    Hamburg
    April 14, 2015

    Our solar system truly is amazing for having just the right conditions to support biological life, although I still think that it is possible to find other solar systems with very similar qualities given the enormous number of stars in a single Galaxy.
    The Keplar space mission has already discovered some very interesting cases, do yourselves a favour and go check it out!

  48. #48 Z Nkonzo
    Pretoria
    April 15, 2015

    15053840

    It truly is amazing how diverse diverse our solar system is, how every detail about it works to sustain and maintain life. The planets that surround us are majestic both scientifically and artistically, there is nothing not to love.

  49. #49 Janet
    Alex
    April 17, 2015

    is there another solar system or is it the only one?

  50. #50 rathile mathosi
    cpt
    April 17, 2015

    its very beautiful to know how much god loves us,its evidence is astonishing

  51. #51 Michael Kelsey
    SLAC National Accelerator Laboratory
    April 17, 2015

    @Janet #49: If you can’t be bothered to read before commented, maybe you’d at least be willing to click a link:

    https://en.wikipedia.org/wiki/Planetary_system

    Or maybe not.

  52. #52 Wow
    April 17, 2015

    its evidence is astonishing

    You mean nonexistent, right?

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