Imagine what space exploration would look like if the Sun were a member of a binary system. Suppose we had another star a few hundred AU away, one that had built its own planetary system. The second star, a thousand times brighter than any other star in our night sky, would be an object of obvious interest, its planets visible to our astronomers and reachable targets for early space technology. The question of life on a planet in that star’s habitable zone would be relatively easy to resolve, and the imperative to study that world first-hand would surely drive space science.
Now we learn that a binary system some 1300 light years from Earth may be evolving in a similar direction. Located in the Orion Nebula, a region rich in star-birth, the stars are about a third the mass of the Sun, considerably cooler and redder in color. One is known to be an M2 dwarf, while the other’s spectral type hasn’t been precisely identified because of obscuration by the disk. The stars are 400 AU apart, so that a single orbit around their common center would take 4,500 years. As this news release from the University of Hawaii at Mânoa points out, that’s about the length of recorded human history.
Researchers have been able to study the pair in the extreme infrared, using the Submillimeter Array on Mauna Kea. That adds to earlier Hubble work showing the presence of one of the disks, visible only as a shadow. The Hawaii researchers have now confirmed the existence of the second. Studies of binary protostars in other regions have generally discovered protoplanetary disks (proplyds) around only the primary star, making this binary system, called 253-1536, an intriguing find.
From the just published paper on this work:
The binary proplyd 253-1536 stands out as the first example of two optically visible stars each with sufficient mass to form a Solar System. Their separation, > 440 AU in projection, is large enough that both the evolution of the disks and their prospects for planet formation can be considered independently of each other.
Remember, too, that at least twenty percent of exoplanets found thus far have been in binary star systems. We’ll learn more about how planets form around binaries — and about how the mass ratio of the stars involved contributes toward the result — as we sample more disks. A key issue considered in this paper is the effect of ionizing radiation from nearby massive stars on the viability of emerging circumstellar disks.
The paper is Mann and Williams, “Massive Protoplanetary Disks in Orion beyond the Trapezium Cluster,” in Astrophysical Journal 699 (June 15, 2009), L55-L58 (abstract).
On the Relationship Between Debris Disks and Planets
Authors: Ágnes Kóspál (1), David R. Ardila (2), Attila Moór (3), Péter Ábrahám (3) ((1) Leiden Observatory, Leiden University, (2) NASA Herschel Science Center, Caltech, (3) Konkoly Observatory)
(Submitted on 30 Jun 2009)
Abstract: Dust in debris disks is generated by collisions among planetesimals. The existence of these planetesimals is a consequence of the planet formation process, but the relationship between debris disks and planets has not been clearly established.
Here we analyze Spitzer/MIPS 24 and 70 micrometer data for 150 planet-bearing stars, and compare the incidence of debris disks around these stars with a sample of 118 stars around which planets have been searched for, but not found.
Together they comprise the largest sample ever assembled to deal with this question. The use of survival analysis techniques allows us to account for the large number of non-detections at 70 micrometer.
We discovered 10 new debris disks around stars with planets and one around a star without known planets. We found that the incidence of debris disks is marginally higher among stars with planets, than among those without, and that the brightness of the average debris disk is not significantly different in the two samples.
We conclude that the presence of a planet that has been detected via current radial velocity techniques is not a good predictor of the presence of a debris disk detected at infrared wavelengths.
Comments: Accepted for publication in the Astrophysical Journal Letters, 20 pages, 2 figures, 3 tables (Table 2 is available in machine readable form in the online journal)
Subjects: Solar and Stellar Astrophysics (astro-ph.SR)
Cite as: arXiv:0907.0028v1 [astro-ph.SR]
Submission history
From: Ágnes Kóspál [view email]
[v1] Tue, 30 Jun 2009 21:36:08 GMT (57kb)
http://arxiv.org/abs/0907.0028
distance > 440 AU
That could offer them a huge telescope. For free!
Depending on the mass of the other star, I suppose.
Hans
Of course we might be in a binary system and the other star is made of Mirror Matter and is thus a lot less visible than a regular matter star. It might be visible in reflected light due to its gravitational capture of regular matter, but we wouldn’t see its emissions of mirror light. The Binary Research Institute, which is a New Age style organisation rather than scientific, believes the observed ‘precession’ is actually due to the Sun shifting around the barycentre of the binary system it’s a part of over a 24,000 year period. Problem is that’s far too short a period for any kind of visible star, even most brown dwarfs would still be too bright after 4.6 billion years. But Mirror Matter might do the job – if the whole “Sun is a binary star system member” idea can be independently verified.
Even the many young “planemos” observed in young star clusters might be planets attached to Mirror Stars. And the many oddly over large Hot Jovians might actually be Mirror Planets…
I just read Robert Foot’s book on Mirror Matter, “shadowlands”, so these ideas have been percolating in my head. Since he wrote that in 2001 some more evidence, for and against, Mirror Matter has cropped up, so it’s still a live option for some cosmic oddities. Would be fun if the Sun did have a Mirror Companion, but hard to get really excited about if we can’t ever observe it. Foot suggests a weak force that allows Mirror and plain matter to exchange some photons, so maybe it won’t remain a “Dark Matter” forever.
So far no planetary systems are known around the companions of extrasolar planet host stars (the closest thing to this currently known are triple systems where the third star is a brown dwarf). I’ve often wondered about what’s in orbit around the companion star to the planetary system around 55 Cancri A: with the primary star apparently having such a high efficiency of forming massive gas giants, it would be odd to have a barren secondary system. Unfortunately the faintness of the red dwarf 55 Cancri B makes the prospects of such a detection less than ideal.
Ref. andy; could the observed absence of planets around the companion stars be related to the (small) separation distance, resulting in the primary star absorbing most of the material? In that case, there could be a minimum separation, not only for any planet formation, but also for double planet formation. Matter of some good modelling, I would think.
BTW, I think there is another, even more fascinating example of a binary system, consisting of two solartype stars and with (more than) sufficient separation: Zeta Reticuli (G1, G2; some 6000 AU apart).
This brings me to a question that has been on my mind for a long time, may even have mentioned it before somewhere in another thread:
It is assumed (or known) that by far most binary and multiple stars formed together (in-situ binary system). However, theoretically there is a (small) chance that a binary system could be the result of two stars of independent origin meeting and being caught into an orbit by their gravity and hence becoming a binary system (ex-situ binary system).
Question: does anyone indeed know of such ex-situ origin binary systems? I would think it should be possible to deduce such an origin from the two stars being very different in composition (metallicity) and age. Furthermore, I would expect there to be a maximum separation distance for binary stars to originate from the same primordial cloud. In other words: if the separation is very large, such as in the case of Zeta Reticuli, wouldn’t this by itself indicate different origins?
It is really neat to have the privaledge to witness whole new star systems in formation. Perhaps in another couple billion years, when any ETI life have evolved on planets surrounding such stars, such beings may or may not by happenstance notice our Sun and wonder if there is any ETI life around any planets orbiting it.
Adam;
Thanks very much for making the above points.
I find the notion of mirror matter fascinating. In theory, it still interacts with gravity. However, I wonder if any attention has ever been payed to the possibility of matter or should I say more appropriately physical material that interacts much more weakly with gravity then known matter, or perhaps not at all, and neither with the other 3 known forces, but which nonetheless would occupy real space within the 4-D space time dimensions of our universe and consequently, would not be located in a parallel universe, nor an alternate and separate universe from our own.
The Caveat here is that such gravitationally non-interacting mattergy would or could still occupy the ordinary 4-D Einsteinian Space Time of our universe, a tall order for assumption, perhaps too tall, given the intimate definitional relationship between gravitation, space time curvature, and the fabric of space time as unified under the equations of General Relativity. Nonetheless, given that nornal baryonic matter constitutes at most 15 percent of the mass in our universe, there is a whole lot of territory to explore regarding the possibility of ETI life forms, and almost certainly for novel physics on which to base our future manned interstellar space craft propulsion systems and methods.
Eitherway, I am pleased with the formation of such new low mass star systems. These particular K or M class stars might just provide us with habitats for 100s of billions or more years to come.
Ronald: at present I think there’s too much observation bias involved to distinguish the physical effects. Most of the time the companions are too faint to get decent radial velocities. As far as I can tell, there isn’t an “observed absence of companions” to the companion stars, but a lack of observations…
Dust retention in protoplanetary disks
Authors: T. Birnstiel, C.P. Dullemond, F. Brauer
(Submitted on 6 Jul 2009)
Abstract: Context: Protoplanetary disks are observed to remain dust-rich for up to several million years. Theoretical modeling, on the other hand, raises several questions.
Firstly, dust coagulation is so fast, that if the small dust grains are not replenished by collisional fragmentation of dust aggregates, most disks should be observed to be dust poor, which is not the case. Secondly, if dust aggregates grow to sizes of the order of centimeters to meters, they drift so fast inwards, that they are quickly lost.
Aims: In this Letter we wish to verify if collisional fragmentation of dust aggregates is effective enough to keep disks ‘dusty’ by replenishing the population of small grains and by preventing excessive radial drift.
Methods: With a new and sophisticated implicitly integrated coagulation and fragmentation modeling code we solve the combined problem of coagulation, fragmentation, turbulent mixing and radial drift and at the same time solve for the 1-D viscous gas disk evolution.
Results: We find that for a critical collision velocity of 1 m/s, as suggested by laboratory experiments, the fragmentation is so effective, that at all times the dust is in the form of relatively small particles. This means that radial drift is small and that large amounts of small dust particles remain present for a few million years, as observed. For a critical velocity of 10 m/s we find that particles grow about two orders of magnitude larger, which leads again to significant dust loss since larger particles are more strongly affected by radial drift.
Comments: Letter accepted for publication in Astronomy and Astrophysics
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:0907.0985v1 [astro-ph.EP]
Submission history
From: Tilman Birnstiel [view email]
[v1] Mon, 6 Jul 2009 14:02:08 GMT (62kb)
http://arxiv.org/abs/0907.0985
Probing the Impact of Stellar Duplicity on Planet Occurrence
Authors: A. Eggenberger, S. Udry, G. Chauvin, J.-L. Beuzit, A.-M. Lagrange, M. Mayor
(Submitted on 5 Jul 2009)
Abstract: The presence of a stellar companion closer than ~100 AU is likely to affect planet formation and evolution. Yet, the precise effects and their actual impact on planet occurrence are still debated. To bring observational constraints, we have conducted with VLT/NACO a systematic adaptive optics survey for close stellar companions to 130 solar-type stars with and without planets.
In this paper we present observational and preliminary statistical results from this survey. Observational results reveal about 20 true companions, of which 4 are new companions to planet-host stars. As to preliminary statistical results, they suggest that circumstellar giant planets are less frequent in binaries closer than ~100 AU than around single stars, in possible agreement with the theoretical studies that predict a negative impact of stellar duplicity on giant planet formation in binaries closer than ~100 AU. These statistical results will need confirmation, however, as they are severely limited by small sample sizes.
Comments: 4 pages, 3 figures, in Proceedings of the conference “Extreme Solar Systems”, ASP Conference Series, Eds. D. Fischer, F. A. Rasio, S. E. Thorsett, and A. Wolszczan, Vol. 398, p. 179, 2008
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Journal reference: ASPC 398 (2008) 179
Cite as: arXiv:0907.0864v1 [astro-ph.EP]
Submission history
From: Anne Eggenberger [view email]
[v1] Sun, 5 Jul 2009 14:49:30 GMT (78kb)
http://arxiv.org/abs/0907.0864
The Stability and Prospects of the Detection of Terrestrial/Habitable Planets in Multiplanet and Multiple Star Systems
Authors: Nader Haghighipour
(Submitted on 30 Aug 2009)
Abstract: Given the tendency of planets to form in multiples, and the observational evidence in support of the existence of potential planet-hosting stars in binaries or clusters, it is expected that extrasolar terrestrial planes are more likely to be found in multiple body systems.
This paper discusses the prospects of the detection of terrestrial/habitable planets in multibody systems by presenting the results of a study of the long-term stability of these objects in systems with multiple giant planets (particularly those in eccentric and/or in mean-motion resonant orbits), systems with close-in Jupiter-like bodies, and systems of binary stars.
The results of simulations show that while short-period terrestrial-class objects that are captured in near mean-motion resonances with migrating giant planets are potentially detectable via transit photometry or the measurement of the variations of the transit-timing due to their close-in Jovian-mass planetary companions, the prospect of the detection of habitable planets with radial velocity technique is higher in systems with multiple giant planets outside the habitable zone and binary systems with moderately separated stellar companions.
Comments: 9 pages, 5 figures, to appear in the proceedings of the conference “Extrasolar planets in multi-body systems: theory and observations” (August 2008, Torun, Poland)
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:0908.4412v1 [astro-ph.EP]
Submission history
From: Nader Haghighipour [view email]
[v1] Sun, 30 Aug 2009 18:28:34 GMT (562kb)
http://arxiv.org/abs/0908.4412