Did Our Sun Capture Alien Worlds?

[alexblackwell]

There's an interesting paper in the December 2, 2004 issue of <i>Nature</i>:<br /><br /><b>Stellar encounters as the origin of distant Solar System objects in highly eccentric orbits</b><br />Scott J. Kenyon and Benjamin C. Bromley<br /><i>Nature</i> <b>432</b>, 598-602, (2004).<br />doi:10.1038/nature03136<br />First paragraph<br /><br />For those without access to <i>Nature</i>, there is a 321 Kb PDF reprint available.<br /><br />See also:<br /><br />Did Our Sun Capture Alien Worlds?<br /><br />Alien Treasures In Our Backyard<br /><br />Earth's Solar System Shaped by Brush with Star, Astronomers Say

 

[earthseed]

If the Kuiper Belt was cut off at 50 AU from the sun, where does that leave the Oort Cloud that is supposed to be further out?

 

[alokmohan]

Actually after discovery of sedna we have opened up a new vista.

 

[CalliArcale]

Now that's an interesting idea. Perhaps some of these eccentric objects weren't perturbed by passing extrasolar objects -- perhaps they ARE passing extrasolar objects! (Or at least, they were until they were captured by the Sun.)<br /><br />This makes me even more excited about plans to study KBOs and other exotic objects. Damoclids would also be a good object of study. There's got to be a way to compare their composition with other bodies in the solar system and determine if they formed here or elsewhere. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[tony873004]

Astronomers Alessandro Morbidelli and Harold F. Levison investigated Sedna's origins by performing numerical integrations using the Swift_rmvs3 orbit integrator to explore the idea that Sedna may have once been gravitationally bound to another star or brown dwarf, and stripped away by the Sun, where it entered a highly eccentric solar orbit. <br /> <br />Using Gravity Simulator, I reproduced their experiment. Morbidelli and Levison set up the following starting conditions: The visiting brown dwarf has a mass of 0.05 solar masses. It is has a velocity of 1 km/s relative to the Sun at infinity. Its approach distance to the Sun is 200 AU. The brown dwarf has a disk of test particles orbiting it in the plane of the encounter at random distances between 20-100 AU. <br /><br /><br />In Morbidelli and Levison's experiment, 44% of the Brown Dwarf's objects were captured into Solar orbit. In Gravity Simulator, consistant with Morbidelli and Levison's experiment, 8 of 20 objects were captured into Solar orbit. <br /><br />As the simulation begins, the Brown Dwarf system is closing in on the Solar System <br />from a distance of just under 1 trillion kilometers. <br />http://orbitsimulator.com/gsimyabb/1.GIF<br /><br />The Brown Dwarf system closes its distance to the Sun. <br />The green planet around the Sun is Neptune. <br />http://orbitsimulator.com/gsimyabb/2.GIF<br /><br />As the Brown Dwarf system gets even closer, <br />the Sun's gravity starts distorting the system. <br />http://orbitsimulator.com/gsimyabb/3.GIF<br /><br />The Sun sends a strong gravitational tidal force through the Brown Dwarf system. <br />Objects outside the Brown Dwarf's Hill sphere are stripped away. <br />Some enter a Solar orbit. <br />http://orbitsimulator.com/gsimyabb/4.GI</safety_wrapper

 

[bobvanx]

Very impressive!

 

[silylene old]

very interesting, Tony !<br /><br />nice work <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>Course that will probably take generations to do, sending an unmanned probe out, collect various samples in a number of regions on Sedna and then analyzing them there and sending the digital data back to a radiotelescope in the outer worlds. <p><hr /></p></p></blockquote><br /><br />All the more reason to get cracking now! <img src="/images/icons/wink.gif" /> C'mon, Congress, fund some outer solar system probes! <img src="/images/icons/cool.gif" /> <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[tony873004]

Simulations such as the one posted earlier aren't trying to prove that this is how Sedna got its orbit. It merely points out that this is a possiblity, one among many theories that should be considered. Even though simulations quickly loose accuracy the longer they are run, much can still be learned by running them. The lost accuracy would only be an issue if the simulation were trying to prove something very exact. A simulation might fail if trying to predict the exact date of Sedna's next perihelion 10 thousand years from now. But it would be accurate enough to suggest a useable window of dates.<br /><br />As far as the Sun losing comets to the brown dwarf, this is much less likely because the Sun is 20x more massive.<br /><br />Here's a simulation similar to the last one, but this includes Solar comets.<br /><br />The first picture shows the Sun. The green planet is Neptune. The 20 blue objects are Kuiper Belt Objects and extended KBO's. They range from 50 - 250 AU. The 50 red objects are inner Oort cloud members. They range from 300 to 1700 AU. Although the Oort Cloud is theorized to be spherical, only Oort Cloud members that orbit in the ecliptic are included in this simulation as it is easier for the brown dwarf to capture or eject objects that orbit in the plane of the encounter.<br />http://orbitsimulator.com/gravity/sd/sd1.GIF<br /><br />The second picture shows the brown dwarf system. The 20 purple objects are comets orbiting between 20 - 100 AUs.<br />http://orbitsimulator.com/gravity/sd/sd2.GIF<br /><br />The simulation is very similar to the one posted earlier. It begins with the brown dwarf aproaching the Sun at approximately 1 km/s, from about 1 trillion km. Its closest passage to the Sun will be 200 AU. The brown dwarf will pass through the Sun's Oort cloud and continue until it reaches the edge of the e

 

[vogon13]

Assuming Sedna spends some of its orbit outside of the heliosphere, would atoms and molecules and dust grains collect on its surface from dust clouds, supernova remnants, and nebulae that the solar system has encountered in its galactic orbit since its formation? <br />What a treasure chest Sedna's surface may be if we are smart enough to get there and study it! <br /><br />Please! Mr. Congressman, I want ANOTHER expensive probe! <div class="Discussion_UserSignature"> <p><font color="#ff0000"><strong>TPTB went to Dallas and all I got was Plucked !!</strong></font></p><p><font color="#339966"><strong>So many people, so few recipes !!</strong></font></p><p><font color="#0000ff"><strong>Let's clean up this stinkhole !!</strong></font> </p> </div>

 

[mikeemmert]

Good morning, Mr. Blackwell;<br /><br />I'm surprised that I haven't run into 2004 XR 190 "Buffy" yet in this discussion:<br /><br />http://www.space.com/scienceastronomy/051219_mystery_monday.html<br /><br />http://en.wikipedia.org/wiki/2004_XR_190<br /><br />This thing's been all in the news.<br /><br />This orbits just outside the edge of the "inner" Kuiper belt. It's orbit is inclined about 45 degrees to the ecliptic. What makes it so valuable for studies like this is that the orbit is circular. Being so close compared to other candidate alien star captures, it probably has not been perturbed significantly in it's history in the solar system.<br /><br />Buffy's not big enough to clear out the outer Kuiper belt, but if it was captured by some other star or other massive object, then the parent body most likely was the culprit in clearing out the outer Kuiper belt. I think it might be possible, comparing it's orbit with other objects we may find out there, to actually recreate the path of that intruding object.<br /><br />I agree with eburacum that there were most likely more than one of these. The object that cleared out the outer Kuiper belt and left Buffy is almost certainly not the one that left long period comets with perihelia clustered at 50,000 AU.<br /><br />I enjoyed watching Tony's "sedna" simulation, which is included in the GravitySimulator package. {Howdy, Tony. I'll get in touch soon.}<br /><br />I responded to borman's post already concerning the "figure 8 capture" in his thread, "Dry Soda Pop Moon". Rather than repeat myself, here's the link:<br /><br />http://uplink.space.com/showthreaded.php?Cat=&Board=sciastro&Number=426703&p

 

[mikeemmert]

<blockquote><font class="small">In reply to:</font><hr /><p>Orbital calculations give possibilities but no assurances. Most orbits are predictable back in time NO more than about 100K years, before large uncertainties arise.<p><hr /></p></p></blockquote><br />Unfortunately, this is correct as a general statement. Depending on what kind of equipment you are using and, more important, what you are trying to model, that 100K figure is highly variable. But if you want some ballpark figure, that will do.<br /><blockquote><font class="small">In reply to:</font><hr /><p>The best evidence that Sedna might be extra-solar origin would be isotopic composition. <snip>...<br />Course that will probably take generations to do...<p><hr /></p></p></blockquote><br />Here is a discussion on the latest in propulsion technology in Missions & Launches, "Europeans And Australians Make Space Propulsion Breakthrough":<br /><br />http://uplink.space.com/showflat.php?Cat=&Board=missions&Number=425365&page=0&view=collapsed&sb=5&o=0&fpart=2#Post426984<br /><br />That's about a <font color="yellow">**NEW! IMPROVED!**<font color="white"> ion engine. They were able to tweak it quite a bit, I was surprised. As for the power source, I read in Scientific American print version several years ago about a new type of nuclear electric generator which uses solar cells instead of thermocouples to generate electricity (it also works with natural gas or kerosene). The heat source is painted black in the colors to which the solar cells are sensitive and white in other colors so that the heat source radiates in colors to which the solar cells are sensitive. It's quite efficient, >30% as opposed to 1% - 2% for thermocouples. I wonder what happened to that, I haven't heard much lately.<br /><blockquote><font class="small">In</font></blockquote></font></font>

 

[najab]

><i>In order to get a craft out there in any time within the reliability of the space craft operating life time, would require enormous & extended acceleration, and that's only possible with a huge, work horse, rocket engine.</i><p>Steve, I wouldn't question you on matters of Psychiatry, but here you are totally wrong. Chemical propulsion is by far inferior to ion-propulsion for missions to the Outer Solar System. As this technology matures - it's only 8 years or so since the first mission using Ion-propulsion as its primary thrust - we are going to see more and more missions using NEP to get to the outer reaches of the realm.</p>

 

[CalliArcale]

<blockquote><font class="small">In reply to:</font><hr /><p>It would require huge velocity and considerable rocket fuel to accelerate something out to that distance.<p><hr /></p></p></blockquote><br /><br />How much propellant is required to acheive the delta-vee is of course dependent on two things: whether or not any gravitational assist can be exploited, and the specific impulse of the engine. Ion drives have enormous specific impulse -- it is common for it to be in the thousands of seconds, whereas chemical engines often don't break 300 seconds.<br /><br />The main problem with ion drives to the Kuiper Belt and beyond is <i>not</i> the low thrust. They have enormous Isp, so as long as you've got time to kill, it's not a problem. What <i>is</i> a problem is the electrical power source for the engine. Currently, the only ion drives to fly have been solar powered. That greatly limits the distance from the Sun at which you can get enough power out of the engine. I could see using a solar powered ion drive on a Kuiper belt probe, but it would have to do all of its thrusting early in the mission (in the first year or so), because after that there just won't be enough sunlight. Plus, you'd be stuck dragging along a power supply that's going to do no good out in the Kuiper belt. I'd prefer nuclear electric propulsion for that sort of a mission.<br /><br />If we're just talking about a flyby and not an orbital insertion, I think a mission to Sedna is acheivable. It's not cheap, but it's acheivable with current technology. I'm rather doubtful of finding somebody to pay for it, though. It was enough of a fight to get New Horizons funded. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[CalliArcale]

BTW, there are production solar-electric engines using xenon propulsion currently in service with specific impulses of over 2500 seconds. By comparsion, the SSMEs have a specific impulse of 453 seconds in ideal conditions (i.e. vacuum). And that's just about as good as you're going to find in conventional chemical engines. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>