Budding astrobiologists should be thinking about the significance of red dwarf stars as they approach their careers. Let’s say, as pure speculation, that one out of every thousand stars in class M has a planet in the habitable zone. That works out to 75 million potentially habitable planets around these stars in our galaxy alone.
Note the assumptions I’m making. First, I peg M dwarfs at 75 percent of the galactic population. That figure is widely in use and I’ve just run across it again in a new paper by Paul Shankland (US Naval Observatory), David Blank (James Cook University, Australia) and colleagues, about which more in a moment. Another assumption: That the Milky Way holds about one hundred billion stars. That’s low-balling the number, I think, because estimates seem to start at that figure and go up to four or five times as high. So my 75 million potentially habitable planets, while just a guess, may not be totally off the wall.
Image: An artist’s impression of a gas giant orbiting a red dwarf. Credit: NASA/ESA/STScI/G Bacon.
Now assume one out of every thousand G-class stars like the Sun has a planet in the habitable zone. Using the same assumption for stellar population in the galaxy and figuring that G-class stars represent approximately three percent of the stars in the Milky Way, we wind up with three million potentially habitable planets around them. Clearly those of us who dwell on odd, rotating planets in which there would be alternating times of light and darkness at the surface (!) and all too little of that helpful solar flare activity are very much in the minority.
We do slightly better with K stars (think Centauri B, for example, or Epsilon Eridani). Somewhat cooler than the Sun, these orange stars are more plentiful than G-class, making up about 15 percent of the galactic population. That leaves us, again using the one in a thousand assumption, with 15 million potentially habitable planets. K stars help, but even when we add them to the G-class, we wind up with substantially fewer habitable planets than around M-class dwarfs.
But note another assumption I’ve made above, one that could stand some scrutiny. I’ve set up one in a thousand as a figure for habitable planet occurrence without any reference to how planets form in the first place. A key question is whether we can assume roughly similar methods of planet formation around M dwarfs as around G stars and the other stellar types. We’re studying models like core accretion and gravitational instability as we develop consistent theories for all this, but our knowledge of what goes on around M dwarfs remains sparse.
What do we need to move forward on these questions? Aside from a lot more planetary detections around these stars, we need to learn more about dust disks around M dwarfs. It’s an interesting fact that a 2007 search around 123 late-type red dwarfs using the Spitzer Space Telescope produced no new detections. That leaves us with only a few M dwarf dust disks, the one around AU Microscopii being particularly well-resolved. We’ve also found them around Gl 842.2 and Gl 182.
Where to look for the next dust disk as we relate M dwarf planet formation to what we see happening around stars in other stellar classifications?
Image: Dust disks around the M dwarf AU Microscopii (left) and the G2 star HD 107146. 32 light years away, AU Microscopii is only twelve million years old. Note the gaps in the disk in both images, where planets may have cleared a path. Credit: G. Illingworth (UCO-Lick)/ACS Science Team.
The devil, it’s often said, is in the details. A friend, exasperated with my enthusiasm for tiny red stars, commented recently that he was tired of all the painstaking numbers — he simply wanted to know whether there was another habitable planet nearby or not. Ah, but it’s just such painstaking numbers that will tell us the tale. We would have no planetary detections at all without gigabytes of slowly accumulating data, from which the signature of distant worlds is finally drawn. A better statement might be, the truth is in the details. Painstaking as they might be, details are the stuff of discovery.
And sometimes even negative results are revealing. The nearby red dwarf Gliese 876, a fascinating, multi-planet system, has shown no evidence of a dust disk, as discussed in the above-mentioned Shankland/Blank paper. This team used the Very Large Array (VLA) and Australia Telescope Compact Array (ATCA) to search for microwave emissions from such a disk. What we learn is not so much that Gl 876 has no disk whatsoever, but that if there is one, it has to fit within a newly tightened series of constraints. From the paper:
…a negative detection (as is the result here) suggests that a thin dust mass could still exist about Gl 876 if the dust density were below the detection threshold of the individual VLA or ATCA resolution-per-pixel, or the overall upper mass limit. The yet-poorly understood dust density, temperature, spectral index, opacity and optical thinness muddies our understanding of the mechanisms at play, and inclination would be a factor in each of these. Still, there are other possibilities for our null result. Another may be that the formation and evolution of systems (disks and planets) is different in M dwarfs. At the least, any unexpanded composition in the system would lead to misunderstood opacities, albedos, radii, or black body behavior.
Flag that latter possibility: The formation and evolution of systems may be different around M dwarfs. No one can say at this point that it is or isn’t, but the fact that we don’t know reminds us that to this date we have only six M dwarfs with known planetary systems, and very little information about the disks that give rise to planets in the first place. Broadening that information may involve using different instrumentation, which should be turned upon the known M dwarf planets. Note this comment (internal references deleted for brevity):
It is also worth mentioning that because of the low luminosity of M dwarfs… that leads to cooler dust about them, sub-millimeter or millimeter telescopes may be more sensitive than mid-infrared ones in detecting such planet-associated-disks. We would encourage observations at these wavelengths be explored further. In particular, we recommend that the six M dwarfs found with planets so far be comprehensively checked for dust, to include Gl 876 (with greater sensitivity than us), Gl 436, Gl 674. Gl 849, Gl 581, and GJ 317. Understanding the dust in such planet-bearing systems… may be a key not just to making a first exo-Earth detection, but will more importantly offer a broader understanding of planets and their formation about the populous M-type stars.
By putting limits on the amount of debris that might be found in the Gl 876 system, these astronomers have also given a nudge to the theory that close-in gas giants may have an effect on clearing out a dust disk. But this is one among a range of possibilities discussed in a paper that advances our knowledge of what is possible around one nearby red dwarf and its implications for planets elsewhere. The paper is Shankland, Blank et al., “Further Constraints on the Presence of a Debris Disk in the Multiplanet System Gliese 876,” accepted by the Astronomical Journal (abstract).
Hi Paul
Rough guess – dust needs source materials, else the PR and Yarkovsky effects clear it out of a system very quickly in cosmic terms. But the gravitational field of a red dwarf is a lot tighter – at equivalent insolation levels – than for bigger stars and more destructive, collision grinding is present to reduce meteoroids into dust that can be swallowed or blown away. Consider how much chillier our Main Belt or Kuiper Belts would be if the Sun was even an M0 star putting out 1/16th of its current output. Would that make them so much harder to detect in IR bands?
Problem here is determining the frequency of debris discs associated with planetary systems, particularly older ones. Even among the known planetary systems of FGK stars, there are not many with debris discs as well. A further question is how detectable the dust associated with the asteroid and Edgeworth-Kuiper belts would be.
If I understood the abstract wel enough, this does not bode too well for M dwarfs in relation to primordial dust disks and terrestrial planets.
But what is at least as important is that the equal assumptions for M, K and G stars (1 in a thousand having a planet in the habitable zone) is not entirely fair: as we know and has been mentioned several times before, the hab zone of G stars is vastly wider than that of M stars. Hence, the statistical chances of having a planet in the hab zone are also much better.
I still think it is no coincidence that we are orbiting a G star. Of course, a sample of 1 is minimal, but all the same, with some 75% M dwarfs and 3% G stars (I actually thought it was closer to 7%), it may be telling.
“The devil, it’s often said, is in the details.”
We’ll make a biologist of you yet, Paul — or, at least, an astrobiologist! (*smiles*)
Hey Athena, I’m all for it! New worlds to conquer and all that… :-)
A few thoughts …
Can we consider the evidence of bodies smaller than the sun in our own solar system? Jupiter and Saturn have substantial retinues of satellites. What would be the difference between them and candidate red dwarfs? Many red dwarfs are part of multiple-star associations. Would they produce their own disks, plus gather material from companions as Jupiter and Saturn have done?
Can we make assumptions about the relative sizes of the planetary zones of a red dwarf system? What would be the relative stability of a planetary system spread out over tens of millions of miles rather than 3 billion? Have astronomers compared dust disk sizes to stellar mass?
Hi All
andy, what the Main Belt and EK Belt look like from outside our system is a very good question that dust specialists would like an answer to. There’s only so much simulations can tell us.
Jupiter and Saturn have substantial retinues of satellites. What would be the difference between them and candidate red dwarfs?
Good question, and I would like to throw brown dwarf ‘stars’ into the mix also.
My question is, “At what point would a star’s ‘habitable’ zone would be determined more by gravitational tidal effects than heat and light?”
What say you esteemed commenters?
Is the age of M-dwarfs not also a factor?
If they get older, there more time to lose dust.
Hans
Hi Folks;
Great discussion!
Red dwarfs are an excellent candidate type of star for the very long term evolution of perhaps a very wide variety of lifeforms into ETI civilizations providing these systems are conducive to the formation of habitable zones. Were the Sun to be able to survive another 10 EXP 15 years, the upper age limit for red dwarfs based on current stellar evolution models, just imagine all of the odd and varied life froms that might evolve on Earth.
When we realize the number quantum mechanical states possible within the entire future life of habitable red dwarf zones and the huge numbers of chemical reactions that can be run on the natural evolutionary computers known as red dwarf habitable zones, one can only dream of the numbers of possible life forms can can and might develope on these zones.
At some point, should animal and ETI lifeforms evolve in a given red dwarf zone, one can imagine the number of evolutionary trees that might be possible, and even given the notion that certain trees are preferentially weeded out leaving certain other evolutionary paths as much more probable, the number of evolutionary degrees of freedom is still huge. One just has to look at the wide variety of animals, plants, fungi, bacteria, viruses, and the like that have evolved on Earth over the past 1 billion years.
When a given civilization such as ours developes technologies like genetic engineering, hybridization, and artificial intellegence based and other very complex computational systems, and the like, the number of possible evolutionary trees becomes even more dramatic.
I’ll continue to dream the dream of Centuari Dreams and frame the motto of Tau Zero over and over in my mind of “To The Stars!” as we look for habitable red dwarf zones.
Thanks;
Jim
James,
shouldn’t that upper age limit for red dwarfs rather be 10 exp 12 (a thousand billion years or 1 trillion or 1000 gy) ? Still enormous of course, roughly 70 times the lifetime of our universe so far.
A spoiler, however, might be the geological aging of a planet in such a habitable zone. What would happen when the initially habitable planet becomes geologically inactive, more or less ‘dead’? Would such a planet end up more like a Mars then, mainly suitable for adapted (and continuously adapting) microbial life?
I think I would rather go for the K-stars then: still a very long lifespan (tens to hundreds of gy), stable, warmer and brighter than M dwarfs, rather abundant.
Hi Ronald;
Thanks for the comments. You make a good point. I will have to check the papers on the lifetimes of the longest living red dwarfs according to sensitivities within the latest stellar evolution models. Even so, a trillion years as you said is a long long time.
And yes. absolutely about planets becomming geologically inactive. It is commonly held that Mars lost its atmosphere in large part due to the weakening of its magnetic field upon the cooling of its core. As its magnetic field was reduced, the solar wind gradually, in effect, pushed its atnosphere off into space leaving what little is left of its atmosphere today.
Once again, Thanks for the input.
Regards;
Jim
Yes, dust has lifetimes of the order of only a few million years so their presence around mature stars means that they are being generated by the collisions of small bodies. Roughly 10 to 20% of main sequence A, F, G and K stars have debris disks, the statistics are even more uncertain for M dwarfs though a paper by Lestrade et al. (2007), http://arxiv.org/abs/astro-ph/0609574 suggest that the percentage may be similar. The Lestrade et al. paper also goes into why detection of disks around M dwarfs may be easier with mm and sub-mm telescopes than telescopes operating in the mid-IR.
Yes, in general the older the star, the less massive any debris disk is likely to be though there are exceptions. Epsilon Eridani has a debris disk about 50 times more massive than our Edgeworth-Kuiper belt, but the star is about 3 billion years older than the Sun.
“Budding astrobiologists should be thinking about the significance of red dwarf stars as they approach their careers. Let’s say, as pure speculation, that one out of every thousand stars in class M has a planet in the habitable zone.”
I think we should be careful about discussing habitabilty/exoplanetary systems in terms of spectral class, particularly when it comes to M stars. If (for the purposes of this exercise) we increase the mass of the sun by the square root of 10, 3.16, we get an AO star. If we decrease the sun’s mass by a similar amount, we get an M3 star. If we then decrease the mass by a similar factor again, we get an M8 star. So a M3 star to an M8 star is like the sun to a M3. Since luminosity is proportional to the approx. 3.5 power of mass, then the type of M star we are talking about makes a big difference to the width of the habitable zone and its distance from its primary.
We talk about M class stars being the most common class but that is partly due the enormous mass range they have. And whether the stellar frequency peaks at high end of the spectral class or the low end will make a big difference on our frequency assumptions.
Dave.
Hi Folks;
It occurred to me that perhaps the lifetime of red dwarfs could be extended for time periods of perhaps as long as 10 EXP 20 years if not longer, essentially for as long as hydrogen gas can be accumulated from the interstellar and intergalactic medium, and for as long as galaxies can survive before the process of stellar evaporation and gravitational radiation emmission induced orbital decay of the remaining stars results in the infall of the remainin stars into the central supermassive central blackholes thus resulting in galactic death.
A mechanism might be devised to position huge bean stalks or elevators in geostationary orbit around such red dwarfs wherein very long conduits composed of super high strength, highly refractive materials would pump freshly collected hydrogen down into the stars and also, in either continuous and/or in batch mode, remove gas from the stars and process the gas to remove helium and any heavier elements produced by nucleo-synthesis whereupon the filtered gas would then be redeposited into the surface of the star. The light generated from the star and/or the heavier atomic number species such as helium and the like could be used to power these beam stalk pumping stations. The helium and heavier elements could be also used to power interstellar and intergalactic frieghters that mine the galaxies and the voids between for fresh hydrogen.
Since the smallest red dwarfs have an absolute luminosity of about four orders of magnitude less than that of the Sun, they fuse about 40,000 metric tons of hydrogen per second. I think huge pumping stations could keep these stars running for several orders of magnitude longer than their maximum natural lifetimes; in short for as long as collectable supplies of hydrogen last. Perhaps when natural hydrogen is depleated, huge membranous CMBR collectors could capture CMBR or by that time CRfBR in order to power proton generators for the poduction of hydrogen stocks to fuel the Red Dwarfs.
Regards;
Jim
OGLE-2005-BLG-071Lb, the Most Massive M-Dwarf Planetary Companion?
Authors: Subo Dong, Andrew Gould, Andrzej Udalski, Jay Anderson, G.W. Christie, B.S. Gaudi, M. Jaroszynski, M. Kubiak, M.K. Szymanski, G. Pietrzynski, I. Soszynski, O. Szewczyk, K. Ulaczyk, L. Wyrzykowski, D.L. DePoy, D.B. Fox, A. Gal-Yam, C. Han, S. Lepine, J. McCormick, E. Ofek, B.-G. Park, R.W. Pogge, F. Abe, D.P. Bennett, I.A. Bond, T.R. Britton, A.C. Gilmore, J.B. Hearnshaw, Y. Itow, K. Kamiya, P.M. Kilmartin, A. Korpela, K. Masuda, Y. Matsubara, M. Motomura, Y. Muraki, S. Nakamura, K. Ohnishi, C. Okada, N. Rattenbury, To. Saito, T. Sako, M. Sasaki, D. Sullivan, T. Sumi, P.J. Tristram, T. Yanagisawa, P.C.M. Yock, T. Yoshoika, M.D. Albrow, J.P. Beaulieu, S. Brillant, H. Calitz, A. Cassan, K. H. Cook, Ch. Coutures, S. Dieters, D. Dominis Prester, J. Donatowicz, P. Fouque, J. Greenhill, K. Hill, et al (20 additional authors not shown)
(Submitted on 9 Apr 2008)
Abstract: We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first in a high-magnification event. These include photometric and astrometric measurements from Hubble Space Telescope, as well as constraints from higher-order effects extracted from the ground-based light curve, such as microlens parallax, planetary orbital motion and finite-source effects.
Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is a foreground M dwarf, with mass M = 0.46 +/- 0.04 Msun, distance D_lens = 3.3 +/- 0.4 kpc, and thick-disk kinematics v_LSR ~ 103 km/s. From the best-fit model, the planet has mass M_p = 3.5 +/- 0.3 M_Jup, lies at a projected separation r_perp = 3.6 +/- 0.2 AU from its host and has an equilibrium temperature of T ~ 50 K, i.e., similar to Neptune. A degenerate model less favored by \Delta\chi^2 ~ 4 gives essentially the same planetary mass M_p = 3.3 +/- 0.4 M_Jup with a smaller projected separation, r_perp = 2.1 +/- 0.1 AU, and higher equilibrium temperature T ~ 70 K.
These results from the primary analysis suggest that OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that is hosted by an M dwarf. However, the formation of such high-mass planetary companions in the outer regions of M-dwarf planetary systems is predicted to be unlikely within the core-accretion scenario. There are a number of caveats to this analysis, but these could mostly be resolved by a single astrometric measurement a few years after the event.
Comments: 50 pages, 13 figures, 3 tables, Submitted to ApJ
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0804.1354v1 [astro-ph]
Submission history
From: Subo Dong [view email]
[v1] Wed, 9 Apr 2008 19:29:02 GMT (948kb)
http://arxiv.org/abs/0804.1354
Hi Folks;
Speaking of the very long term duration of habitability within our universe, we will at some point, I am afraid, have to deal with the possibility of another phase change that would occur in a universe wide manner, perhaps even a phase change that could occur effecting the whole multiverse, omniverse, or meta verse (whatever word you choose) as in the form of the cosmos in the conjecture of the theory of Chaotic Inflation or other multiverse theories.
Our Big Bang has apparently experienced universe wide symmetry braking transitions or phase changes as well as inflation. As a result, I see no reason why such phase changes might not occur again, even ones that occur as a result of quantum indetermancy as a result of the quantum mechanical tunneling out of our universe from a local minimum-energy-well-based-state in which it may rest in a meta-stable state.
According to the theory of Chaotic inflation, our whole multiverse may rest in a metastable local minimum state within a socalled scalar vacuum field wherein such fields would be gradientless on a macroscopic scale but wherein on a microscopic scale, random or some what random energy state fluctuations occur, for which on a larger scale, they are normally washed out by the cancellation effects of pairs or groups of oppositely directed net gradients occuring on the microscopic scale.
The good news is that there might be innumerable multiverses, each multiverse existing as an ever growing fractal tree of parent and baby universes wherein each such multiverse is casually decoupled from the rest or at least increadably minimally casually coupled to the point of being safe from what would normally occur to our multiverse.
Thanks;
Jim
Hi James
What do you think that means for the Fermi Paradox if we’re in a Multiverse produced by eternal inflation? In my mind it implies that Life never survives the local death of its originating sub-universe – kind of a gloomy prospect.
Hi Adam;
Thanks for the insight and comments. Gloomy prospect indeed. I get through the day when contemplating all the forces that could put an end to humanity and also to the whole entirety of any ETI civiliztions within our universe by resorting to my personal religious faith and hoping in a Final Resserection and a new heavens and a new Earth. I do not mean any attempt to convert anyone here but rather just intend to share with fellow interstellar manned travel enthusiasts just one anecdotal account of how a fellow space head comes to grip with his utter insignificance within the vast scheme of things and his own frail bodily mortality. My large husky 440 pound frame is no match for the many cosmic phenomena that could reduce my body to a ionized plasma or worse including my brain in an instant.
Regards;
Jim
jim, just read your comments above and you are 100% correct we are an integral part of the universe! saw neil degrasse tyson on tv recently saying that when he considers how small we are in the scheme of things…but how we are A PART OF THE UNIVERSE it makes him feel really quite good! also,not to get religious or anything but heck when i look at the world today, the dalai lama in the united states, the pope in the united states…i think thats really good – it could only help to pay some respect to fine men as they are! too many problems around today is what i mean. maybe to look at another point of view wqould not be so bad. respectfully to one and all your friend george
Hi George;
Thanks for the above response.
I could not agree with you more. I am also happy to be part of something much larger than myself, i.e., the universe. Maslow was right on when he developed the concept of the hierarchy of needs. These two fine gentlemen, the Pope and the Dalai Lama can help usher in an era of peace and economic prosperity for all and the great forwrd leaps in science and technology that all of us space heads so eagerly await in the hopes that we will reach the stars. Thus I strongly feel that a civilization of hope and love can be established by us as humanity as we work toward the ultimate prolife goal of giving countless humans a chance to be born commensurate with the huge numbers of human persons that can be supported by the vaste mineral and other natural resources thoughout the universe.
Thanks;
Your Friend Jim
Hi James & George
Discussing these issues inevitably leads into eschatology – the ‘logia’ of ‘last things’ – and talking about the far ends of time usually runs into God or the Singularity. One concept which is key is the idea that Life can affect the evolution of the Cosmos. We will either adapt to the Cosmos or we adapt it to us. The former is more liable to lead to extinction when conditions change.
adam yes your above comments make alot of sense.thank you your friend george
Hi Adam;
Thanks for the comments and insights.
The concept that we might adapt the cosmos to our needs is interesting. I can see a whole engineering program taught in schools perhaps 10 EXP 100 or so years into the future refered to as Sustainable Cosmic Engineering. Talk about the ultimate in Green programs!
Regards;
Your Friend Jim
jim yes talk about the ultimate program in general! yes sir! we here often consider LARGE SCALE engineering. good reason why i hang around. thank you one and all your friend george
Hi George;
Thanks for the above comments.
A really cool program of R&D would be to learn out how to produce our own universes. I have made simmilar comments before but summarize the basic concepts as they were developed by others before me.
It would be interesting if the mechanics of the formation of baby universes from parent universes could be worked out in such great detail such that tailored made universes with appropriate laws of physics, dimensionality, numbers and types of particles and forces, etc., could be produced which would be compatable for future human habitation.
Another concept for producing universes involves the concept of acquiring about 50 Kg of an exotic material called false vaccuum, compressing this material to the size of roughly that of a proton, and then letting it spontaneously decay until it detonates or inflates into a universe with simmilar properties of our own universe. Such a creation has been proposed as perhaps possible with the ceveat being the acquisition of 50 kilograms of the yet to be discovered exotic material referred to as false vaccuum and some how compressing it to the size of a proton.
If we can create a universe, perhaps we can learn how to create an entire multiverse. According to the theory of Chaotic Inflation, baby universes allegedly form as a result of the formation of random statistical microscopic embalances in scalar fields resulting in a vacuum fluctuation thus leading to a bootstraping and runaway effect wherein an inflating universe is formed. It has been suggested that whole multiverses or parent-child universe lineages or family trees can form starting from a initial fluctuation in an analogous field inwhcih baby iniverses form.
Thanks;
Your Friend Jim
jim,everybody,when it comes to really cool r&d programs,don’t worry,hold the phone! i’m there! but producing others universes!? well maybe so i know there is a lot of talk going on about subjects like that . can only in my opinion add to our scientific knowledge which can only lead to good! LOL jim i’ve said it before, you think BIG! have a great sunday my friend and i’ll talk to you soon in the new week. all the best to every one of you,please keep those thoughts ideas and theories comming! your griend george
Hey Jim, George and all
I have high hopes for M-dwarfs. Since according to my theories the oldest stars in the observable universe would be more than twice the current predicted age of the universe. If true this would provide much more time for many of the planets that orbit these stars to develop life.
Also large intergalactic clouds have been found that might accordingly produce at least elementary life forms within the pressures and temperatures of these large galactic sized clouds that also could accordingly be twice as old as the BB model asserts. This would provide enough time for life to evolve within these intra-galactic clouds which could spread to many planets once such life-containing clouds would develop stars and planets or merge with an existing galaxy.
your friend forrest
forrest maybe things are swinging in your direction. i see alot of things lately that imply that the universe is older than we had supposed! your book will be up there with the best yet my friend! have a great day,george
Hi forrest
You’ve piqued my interest – I will have to finish reading your book.
Adam
Hi Adam, George, Jim
After reading the first 25, e-mail me for the next 25. Maybe the most interesting part of the text, according to my editors so far, is the large Predictions Section starting at page 104, and the related logic of why these predictions would be directly implied from the Pan Theory — maybe 40 pages.
Could just send the Predictions but then the logic and mathematics behind why all these predictions would be implied by the theory, would be missing. But maybe that would still be enough to peek ones interest to later read the related logic.
The Title of the Book that I’m currently leaning toward is “The Pan Theory — a General Unified Model of cosmology, physics, and the quantum theory.” The present English publication is scheduled for the fall of 2010. I presently have just one current editor, in San Diego. He’s about 3/4 of the way through the text. Anyone that would like to be an editor for editors’ credits, the job is available. Need all types of editors with interests in these areas to provide questions and comments concerning the text. The deadline for extraneous editors is probably the summer of 09, only about one plus years from now.
forrest_forrest@netzero.net
your friend forrest
Dangerous Sunrise on Gliese 876d
Illustration Credit & Copyright: Inga Nielsen (Hamburg Obs., Gate to Nowhere)
Explanation: On planet Gliese 876d, sunrises might be dangerous. Although nobody really knows what conditions are like on this close-in planet orbiting variable red dwarf star Gliese 876, the above artistic illustration gives one impression. With an orbit well inside Mercury and a mass several times that of Earth, Gliese 876d might rotate so slowly that dramatic differences exist between night and day.
Gliese 876d is imagined above showing significant volcanism, possibly caused by gravitational tides flexing and internally heating the planet, and possibly more volatile during the day. The rising red dwarf star shows expected stellar magnetic activity which includes dramatic and violent prominences. In the sky above, a hypothetical moon has its thin atmosphere blown away by the red dwarf’s stellar wind. Gliese 876d excites the imagination partly because it is one of the few extrasolar planets known to be close to the habitable zone of its parent star.
http://antwrp.gsfc.nasa.gov/apod/ap080521.html
A potential new method for determining the temperature of cool stars
Authors: S. Viti, H. R. A. Jones, M. J. Richter, R. J. Barber, J. Tennyson, J. H. Lacy
(Submitted on 21 May 2008)
Abstract: We present high resolution (R = 90,000) mid-infrared spectra of M dwarfs. The mid infrared region of the spectra of cool low mass stars contain pure rotational water vapour transitions that may provide us with a new methodology in the determination of the effective temperatures for low mass stars. We identify and assign water transitions in these spectra and determine how sensitive each pure rotational water transition is to small (25 K) changes in effective temperature. We find that, of the 36 confirmed and assigned pure rotational water transitions, at least 10 should be sensitive enough to be used as temperature indicators.
Comments: accepted by MNRAS
Subjects: Astrophysics (astro-ph)
Cite as: arXiv:0805.3297v1 [astro-ph]
Submission history
From: Serena Viti [view email]
[v1] Wed, 21 May 2008 15:07:17 GMT (269kb)
http://arxiv.org/abs/0805.3297
While it’s true that about 75% of all stars in the Milky Way are red dwarfs, what your model fails to take into account is that a LARGE number of these, perhaps even the MAJORITY, are Population II red dwarfs — that is, red dwarf stars that formed when the galaxy was new and no heavy-element enrichment had yet taken place.
Around such metal-poor stars, there isn’t going to be enough carbon, silicon, oxygen, etc. to form solid planets AT ALL. Any planets they have are going to be hydrogen-and-helium gas giants.