From the IOP website:
May 31, 2012
Tushna Commissariat
A method that uses laser frequency combs to calibrate astronomical spectrographs to unprecedented accuracies has been developed and successfully tested by researchers in Europe. The method could be used to find Earth-sized exoplanets by detecting their tiny influence on the motions of their companion stars. The comb was tested on the European Southern Observatory’s High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph at the La Silla Observatory in Chile.
Astronomical spectrographs separate light according to wavelength and the spectra that they produce play important roles in many aspects of astronomy. As a result, astronomers are constantly looking at ways to make their spectrographs more accurate, stable and precisely calibrated. Currently, the best spectrographs, such as HARPS, use thorium-argon lamps or iodine cells for calibration – however, these do not deliver the precision to detect the tiny shifts in the wavelength of starlight caused by the presence of an exoplanet.
These shifts in wavelength correspond to changes in the radial velocity of a star – which, in turn, could be caused by the gravitational influence of any exoplanets that may be orbiting the star. Radial-velocity changes are derived from shifts in the parent star’s spectral lines caused by the Doppler effect. While this method works very well for enormous planets that orbit very close to their parent stars, the accuracy needed to measure the tiny shifts caused by an Earth-sized planet orbiting within the habitable zone of a Sun-like star cannot be achieved today.
The idea of using a frequency comb to calibrate a spectrograph has been discussed for several years, but this is the first time that the technique has been tested and verified, thanks to the efforts of Tobias Wilken of the Max-Planck-Institute for Quantum Optics in Munich and colleagues in Germany and Spain, in collaboration with scientists at the European Southern Observatory (ESO).
Read the rest of the article here
This will be welcome news to Ian Wilson, who has a new article up on the search for advanced ET civilisation:
life are those that are located at just the right distance
from high metallicity G and K type main-sequence
stars that allow the bulk of their surface water to
remain in the liquid state.
The Sun’s [current] Habitable Zone extends from
0.95 A.U. to about 1.37 A.U. (i.e. from just outside
the orbit of Venus at 0.72 A.U. to just inside the orbit
of Mars at 1.52 A.U.).
As a general rule, the mean distance of the centre of
the Habitable Zone from a main-sequence star [in
Astronomical Units or A.U.] is given by
[1. Wikipedia Habitable Zone 2012]:
= SQRT (Lstar / Lsun)
where Lstar = luminosity of the parent star
_____Lsun = luminosity of the Sun
This information can be used to place approximate
limits on the MK spectral type of potential candidate
stars.
First, main sequence stars with masses above ~ 1.5
solar masses [i.e. MK spectral types of F5 or earlier]
have lifetimes that are shorter than about 5 billion years.
Hence, these type of main sequence stars are unlikely
to remain stable over the billions of years that are needed
to support the development of advanced civilizations.
In addition, these type of stars have convective cores
and radiative outer envelopes and so the type of solar
activity that they support will not be the same as that in
lower mass stars which have convective outer envelopes.
Second, the following table shows that as the luminosity
[and mass] of stars decrease along the main sequence,
the distance to the centre of the Habitable Zone (shown
in column 3), moves closer into the parent star. This
means that for late K spectral types stars [i.e. K6, K7,
K8,..etc.], any earth-like planet that is in the Habitable
Zone will be tidally-locked with their parent star, markedly
reducing its chances of producing advanced life-forms.
MK_____Luminosity____HZ_____Tidal-Locking
Spectral___(Solar_____Distance____Distance
Type____Luminosities)__(A.U.)[2]__(A.U.)[3]
F0________6.0________2.45______0.55
F5________2.5________1.58______0.53
G0_______1.10________1.05______0.51
G5_______0.79________0.89______0.49
K0_______0.40________0.63______0.47
K5_______0.16________0.40______0.43
M0_______0.063_______0.25______0.39
[2. Zombeck 1990]
[3. Kasting et al. 1993]
Hence, searches for advanced civilizations
should be restricted to single, high metallicity,
old [> 5 billion years] main sequence stars that
have MK spectral types between F8/F9V and
K5V.
Tallbloke's Talkshop 
I’ve often wondered why they can’t use the Doppler effect to tease out the motion of the actual earth-sized planet, by ‘sweeping’ the infrared band over a period of three years (akin to Kepler’s minimum time frame). Whilst the actual luminosity of the planet in the planet in the infrared would be admittedly swamped by the star, the Doppler effect would be gigantic as the planet approached and receded, amounting to tens of kilometers per second as opposed to metres per seconds for the star. This would translate into a crest which would sweep up and down the infrared band as the redshift of recession and blueshift of approach reinforced the luminosity at each successive wavelength. I can only assume that the swamping is too great to see this signature. I do know that the first direct detection of an exoplanet was via infrared subtraction whereby the infrared signature of the star was subtracted from the signature of the planet-plus-star but this was for a massive planet at some distance. It was in fact this achievement, along with the usual Doppler studies which made me think of the planet Doppler effect. Can anyone explain why this isn’t possible?
Tallbloke,
Thank you for highlighting my article – much appreciated.
Below is the text of an update to the article today 01/06/2012
that might interest your readers concerning the link between
exo-planetary systems, metallicity and the level of stellar
activity.
~~~~~~~~~~~~~~~~
Supportive Evidence for the Proposition that Planetary
Systems May Be Responsible for Enhanced Stellar
Activity.
The following graph [Please click on graph – Gray et al. 2006]
shows the level of chromospheric activity, as measured by
log [R’HK], plotted against metallicity, for dwarf F, G, and K
stars. The histograms below this graph show that level of
chromospheric activity is bi-modal for high-metallicity stars
(i.e. [M/H] > -0.2) and single-peaked for low-metallicity
stars (i.e. [M/H] < -0.2). [Gray R.O. et al. 2006]
In order to see the graph, go to:
http://astroclimateconnection.blogspot.com.au/2012/05/earth-like-planets-in-habitable-zone.html
The most obvious explanation for lack of chromospherically
active stars amongst the low-metallicities stars is that they
are, on average, older than the high-metallicity stars. Hence,
the low activity is a direct consequence of the fact that older
stars are less chromospherically active because they are
rotating more slowly than the younger stars.
One problem with this explanation is that there is a very sharp
transition from bimodality to single-peak behavior in stellar
activity at [M/H] = -0.2.
Indeed, Gray et al. 2006 state that:
"This sharp transition from bimodality to single-peaked
behavior at [M/H] = -0.2 suggests that the cause of this
phenomenon is not primarily age-related but rather is
associated with some parameter necessary for the
generation of an active chromosphere that is switched
off at this divide.We expect that this parameter
has something to do with rotation or, more specifically,
differential rotation, but we do not have sufficient data
to speculate further."
Of course, another equally plausible explanation for the abrupt
onset of high stellar activity at [M/H] = -0.2 is the fact that the
likelihood of a stellar system containing a planet increases as
the square of the metallicity, with Fischer and Valenti 2005
finding that:
"From this subset of stars, we determine that fewer than 3% of
stars with 0.5 < [Fe/H] +0.3 dex, 25% of
observed stars have detected gas giant planets. A power-law
fit to these data relates the formation probability for gas giant
planets to the square of the number of metal atoms.”
[Fischer and Valenti 2005]
Hence, it is just possible that high stellar activity is a
direct consequence of planetary action and that the
presence of differential rotation in the outer layers
of a star is just an indication that this interaction is
taking place.
Scute says: June 1, 2012 at 12:38 am
“I’ve often wondered why they can’t use the Doppler effect to tease out the motion of the actual earth-sized planet, by ‘sweeping’ the infrared…”
I certainly don´t know much about this interesting problem but have a suggestion. Would it be technically easy to decide the planetary motion of our solar system planets by Dopler shifted infrared light? We certainly don´t need such technique since we can see light but a search of information in this direction might lead to an answer to your question (besides the probable swamping by a star which you suggest). Your suggestion might be spot on but isn´t there a lack of reference to specific
identifiable atomic frequencies needed for deciding a Dopler shift?
Off topic but can’t get suggestions to work
Hi a this piece sets cat among pigeons
http://www.quadrant.org.au/magazine/issue/2012/6/our-planet-saving-science-lobbyist-the-integrity-of-the-australian-academy-of-science
Cheers tony
Sent from my iPad
Hi Hans
Here is a picture of the planet I was talking about.
It was the VLT, very large telescope that took it using a stellar disc to block out the glare of the star despite the lesser glare in the infrared. The resolution to fractions of an arcsecond make me wonder whether the other proposed method would add anything. However, the VLT is a very expensive bit of kit and it was a large planet. I doubt if they would use it for routine searching.
You were wondering whether my proposed method would have enough identifiable atomic frequencies. I presume you mean absorption frequencies whose absorption lines would ebb and flow as the planet advanced and receded? This is where I get shaky because I only did high school spectroscopy in the visible spectrum. However, in my research today I did read that the WMAP Cosmic Microwave Background detector used radiometers that could jump to different microwave frequencies to avoid manmade radio noise. I’m not sure if they could do that in the infrared but if there were several radiometer tripwires, so to speak, spread across the suspected infrared bandwidth for earth type planets in one year orbits at 1AU (surely a very precise bandwidth) then the planet signature would be seen to cross each tripwire i.e. reinforcing the radiative flux as it did so. The time lag between tripwires would vary, betraying movement that was close to Simple Harmonic Motion, allowing for a planetary ephemeris to be established and then refined on each subsequent orbit.
Your idea of testing the basic principles in our own solar system is clever. Mercury couldn’t be more ideal: hot and fast!
Ninderthana,
I see that your Case Study A, 61 Cygni A/B is number 15 on the SETI nearest 100 target list, but was
listed “No” in the “HabCat” list:
http://iopscience.iop.org/0067-0049/149/2/423/fulltext/58676.tb2.html
In your list of prime candidates, HD26965 (GJ 166A, o 2 Eri) is also listed in the nearest 100 target list (Number 48 in that list, but also as “No” in the “HabCat” list, and is noted to be a flare star). GJ166B and GJ166C are also listed in the SETI target list, but as “NA” in the “HabCat” list.
The SETI nearest 100 target list does not include stars more distant than 22.4 light years, which all your other prime candidates exceed. It appears that SETI might get around to investigating 61 Cygni A/B and o 2 Eri, but I gather that the “No’s” in the “HabCat” list might make them, at best, secondary SETI targets rather than prime targets. Do you think this is the case?
Gerry,
The disorganized nature of my post has lead you to use the wrong criterion to judge the
worthiness of the proposed candidates on my list.
The point of my list was to choose candidates that meet [what I regard as] three out of the dozen or so essential requirements for habitable planets with complex life forms. It is not
a sure-fire, dead-certain list of stellar systems that I believe will definitely contain complex
alien life.
The list contains those stellar systems which I believe will have:
1. Jupiter-size planets rotating in near circular orbits around the parent star at distance greater than about 3 to 5 A.U. This requirement is essential for terrestrial planets to form in the life zones (i.e. with orbital radii of ~ 0.5 to 1.5 AU) with stable near circular orbits.
2. Parent stars that last long enough for complex life to form i.e. those with main sequence stars that have MK spectral types later [cooler surface temperatures] than about F7V or F8V. This boundary could be pushed towards earlier spectral types (e.g. F5V) but these type of stars start developing radiative, rather than convective envelopes and so I am not sure if planetary gravitational/tidal models would drive solar activity in these type of stars.
3. Parent stars that are luminous and warm enough to have Habitable life zones that are far enough away from the star to avoid tidal-locking. The life zone of stars later [cooler] than K7V or K8V are so close to the parent star that any planet orbiting the star in the life zone will always present the same face towards the star – severely restricting the planet’s ability to support complex life.
However, it needs to be emphasized that there are a number ways that the stellar systems on my list could be disqualify as potential candidates for supporting complex extra-terrestrial life.
Here are just a few:
a. The Stellar system must have planets. Hence, only those systems with high metallicty (i.e. comparable to solar or greater) should be considered, since this seems to be a requirement for the formation of rock (Terrestrial) worlds. This may eliminate some of the candidate stars from my list as not all of the stars in my preliminary list have measured metallicities.
b. The primary star in the stellar system must be old enough for complex life forms to develop.
So any stellar system on my list that is younger than ~ 3 – 5 billion years will not have had time
to develop complex life. This does not rule out the possibility that the system will host an advanced civilization in a billion years or so but it does mean that the SETI crowd may a little reticent to put their collective energies into looking at these systems. In addition, it may eliminate some of the candidate stars from my list as not all of the stars in my preliminary list have measured ages.
c. The parent star may [CURRENTLY] be a strong source of flaring activity, either because the star is intrinsically variable (e.g. a BY Draconis star) or because the star is in its infancy and so its rapid rotation is producing lethal levels of flaring and stellar activity. So again, ths may eliminate some of the candidate stars from my list as not all of the stars in my preliminary list have measured ages.
and I could go on…..
The primary purpose of my list is not to produce a list potential candidates for the SETI program.
It is to point out that if they want have a snow-ball’s chance in hell of finding complex life in the great unknown, they will have to start by compiling a list of stellar systems that meet conditions listed in points 1 to 3 above. Once they have a list [no mean feat in itself] of this sort, containing all potential candidates out to say 40 parsecs, they will then have to whittle out all of those systems who do not meet points a to c listed above [and I am sure that you could throw in
one or two other restrictions for good measure].
I hope this clears up a little of the confusion of my post.
Ninderthana,
Apparently, one of the principal criteria being used to decide which stars qualify for the HabCat is constant luminosity. From
http://www.nasa.gov/vision/universe/newworlds/HabStars.html:
“Turnbull and Tarter took on the daunting task of evaluating 118,218 nearby stars, using membership criteria of constant luminosity and potential habitable zones. A database search gave them their first cut, which they call the “Celestia sample.” If a star fluctuated by 3 percent in its luminosity, the level of variability detectable to Hipparcos, complex life would be imperiled.”
Since the 3 percent luminosity variation detectable by the Hipparcos satellite is a huge variation compared with maximum solar luminosity variations, believed to be less than 0.5 percent, this HabCat rejection criterion is not in direct conflict with acceptance of stars with activity periods similar to solar activity periods. However, when satellites are able to detect luminosity variations of 1 percent, it will not surprise me if stars with that level of variation will also not qualify for inclusion in the HabCat. This would be a mistake, in my opinion.
Binary and trinary systems are also disqualified from HabCat consideration on the grounds that planetary orbits in the habitable zone would be too unstable. This is undoubtedly true in many cases, but there may be important exceptions. My concern is that the apparent eagerness for blanket disqualification of stars that do not meet unnecessarily strict guidelines may result in disqualification of stars with the very kind of planets we should be looking for.
Gerry,
You have a number of good points about the selection criterion used in the HabCat.
I am afraid that Science is littered by samples and searches were the boundaries that have been set are so far off that they either:
a. waste resources and time by including too many data points that are almost certainly going to give a negative result.
b. actually exclude the phenomenon that is being sought.
If a star fluctuates by 3 % on short time scales [in one given direction] it would be a serious impediment to development of complex life, particular if it was in the X-ray, UV and visible. However, a 3 % variation in the UV may not be serious if the planet in the Habitable Zone has a oxygen rich atmosphere that develops a thick ozone layer.
I agree with you that excluding all multiple stars is a not the wisest of boundary choices.
This is particularly true if you have a single star, with another single star or close binary pair,
that is separated from each other by hundred of A.U. It is still possible for stable orbits to form
around the isolated single star that could harbor life.
In order to produce cyclical solar activity cycles in the parent star, my VEJ Tidal-Torquing model:
a. needs a massive Jovian planet (or star/brown dwarf) that is moving in a near circular orbit at a large enough distance so that it does not disrupt the orbits of terrestrial planets in the stars’ Habitable Zone.
b. must have a Jovian planet (or star/brown dwarf) that is the dominant gravitational force that is acting upon the star.
c. requires that this Jovian planet (or star/brown dwarf) pulls and pushes upon a tidal bulge(s) that is(are) periodically formed by alignments of terrestrial planet located with a few A.U. of the parent star.
Thus, the VEJ Tidal-Torquing model intrinsically requires a long term quasi-resonance between the orbits of the outer Jovian planets (or star/brown dwarf) and the inner terrestrial planets that
are conducive to producing stability (via near circular orbits) in the Terrestrial and Jovian orbital
regions.
It is in this way that HabCat’s avoidance of binary stars may in fact exclude actual systems like
61 Cygni that could in fact be the very place to look for complex life forms.
Gerry,
There is an interesting discussion on the stability of orbits for planet in the Habitable Zone at:
http://iopscience.iop.org/0004-637X/583/1/473/fulltext/56743.text.html
A pertinent quote from this article is:
“In that respect, it is significant that most of the extrasolar giant planets recently discovered (compare Table 2 to Table 1) are of the distant, eccentric type, which is most disturbing to potentially habitable terrestrial planets. The discoveries of 55 Cnc d and Gl 777A b show, however, that Doppler surveys just began to reveal distant, low-eccentricity giant planets that are more akin to the solar system giants and do not perturb potentially habitable terrestrial planets significantly. While the solar system is expected to remain roughly as dynamically habitable as estimated in our equivalent model when the other three giant planets are included, the dynamical habitability of known extrasolar planetary systems will mostly depend on whether radial velocity surveys establish or rule out the presence of giant planets with strongly perturbing influences at ~ 0.5 to 2 AU distances from the parent star.”
I am claiming that stars with 5 – 15 year stellar activity cycles have a Jovian-like planet(s) [or a star/Brown dwarf] in a near circular orbit(s) that is(are) further than 3 – 5 A.U. from the parent star and so these stellar systems are likely to have terrestrial planets in or near the Habitable Zone which are in stable orbits.
Another useful quote is:
2.3. Zone of Influence and Classes of Dynamical Habitability
The definition of a planet’s gravitational zone of influence often used in dynamical studies is 3 times its Hill radius,
RHill = a (Mp/(3 x M*))^(1/3)
where a is the planet’s semimajor axis, Mp is the planet’s mass, and M* is the mass of the central star. Three Hill radii cover the region of close encounters with the planet, which typically result in collisions with the planet, the central star, or ejections from the system. Since a planet with finite eccentricity, e, experiences radial excursions from (1 – e)a to (1 + e)a, we generalize the definition of the planet’s zone of influence to include the entire region extending from
Rin = (1 – e)a – 3RHill
to
Rout = (1 + e)a + 3RHill.
The values of the inner and outer radii of the zone of influence of all extrasolar giant planets are reported in Tables 1 and 2 (a planetary mass corresponding to sin i = 0.5 was specifically assumed for these numerical estimates).
Based on the degree of overlap between the planet’s zone of influence (ZI) and the system’s habitable zone (HZ), we define four classes of dynamical habitability:
Class I: a 0.25 AU.
Class II: a > 0.25 AU and no overlap between HZ and ZI.
Class III: a > 0.25 AU and partial overlap between HZ and ZI.
Class IV: a > 0.25 AU and HZ is fully inside ZI.
Class I is defined to include close-in extrasolar giant planets that, because of their proximity to the parent star, should not gravitationally influence much planets in the habitable zone.
In systems with multiple giant planets, dynamical habitability will be determined by the planet that most strongly influences the habitable zone (i.e., of highest class, according to the definitions above).
Because of the complete overlap between zone of influence and habitable zone, systems containing class IV giant planets are unlikely to harbor habitable terrestrial planets.7 It is more difficult to estimate the likelihood of finding habitable terrestrial planets in systems containing class III giant planets, however, because the overlap is then only partial.
7 We note that it is, in principle, still possible for these systems to harbor habitable terrestrial planets at the stable Lagrange points of their giant planets. This possibility may be limited to the five giant planets identified in § 2.2.2 as good potential hosts for habitable moons.
Ninderthana,
I found in the catalog of 774 discovered exoplanets,
http://exoplanet.eu/catalog-all.php
Planet HD 3651 b, Mass = 0.2 Jupiter mass, Period = 62.23 days, Semi-Major Axis = 0.284 AU, Eccentricity = 0.63, Inclination ?83 deg, Status R (planet detection published in Refereed papers), Discovered 2003, Update 19/10/10
The eccentricity of this planet’s orbit is very high, but the fact that HD 3651 is one of your prime candidate stars makes the find exciting nevertheless. Congratulations!
Gerry,
Thanks for the approbation but this planet was discovered in 2003. In addition, a
brown dwarf companion (M = 20 to 60 MJup, projected separation 480 AU) has been detected by direct imaging (Luhman et al. 2006, Mugrauer et al 2006).
The parent star (54 Psc) is a K0V that has a tentative age of 5.6 Giga-years and metallicity of
0.05 (log(Fe/H) =0.0 is solar metallicity), so it’s old enough for a complex civilization to develop.
The stars’ stellar activity cycle is 13.8 years long.
The exo-planet at 0.284 A.U. [i.e. HD 3651b] has a mass comparable to Saturn [i.e. 0.2 MJupiter], however, its orbit is highly elliptical e= 0.63, which means that it there is a good chance that it would de-stabilize any planet that would be orbiting in the stars Habitable Zone centered at 0.63 A.U.
We can check this by using the formula for the outer zone of planetary influence for HD 3651b:
Rout = (1 + e) x a + (3 x a x (Mp/(3 x M*))^(1/3)
Rout = 0.5 A.U.
for a stellar mass = M* = 0.79 Msun (N.B. Msol = 1047 x MJupiter)
Hence, if there is a Earth-like planet in the Habitable Zone it would have to be located towards the outer half of this zone [i.e. > 0.7 A.U.]
If the V-E-J Tidal-Torquing model is correct, HD 3651b would play the role of Venus in
our solar system and there would have to be some other planet periodically reinforcing its tides.
An additional requirement would be a large Jovian planet somewhere beyond 3 to 5 A.U.
Hi Rog,
Just been over at WUWT and the change in Willis in his direction and civility is profound.
This is good for he is an original thinker and he seems to have come to terms with you and your imputs from the way out there. He is a very good weapon in the search for the truth. Regards
[Reply] I think you spoke too soon. Mr Hyde has taken over again. He’s a weapon alright. 🙂
BREAKING EXOPLANET NEWS
The consensus view that the parent star must have high metallicity is now being questioned with this latest find:
“A new-found planet is in a ‘just-right’ location around its star where liquid water could possibly exist on the planet’s surface. A team of international astronomers have discovered a potentially habitable super-Earth orbiting a nearby star in a habitable zone, where it isn’t too hot or too cold for liquid water to exist. The planet, GJ 667Cc, has an orbital period of about 28 days and with a mass about 4.5 times that of the Earth. The star that it orbits is quite interesting. It is an M-class dwarf star and is a member of a triple star system and appears to be quite different from our Sun, relatively lacking in metallic elements.”
http://www.universetoday.com/93265/potential-goldilocks-planet-found/
Announcement PDF:
Click to access 1202.0446v1.pdf
For whatever this is worth, GJ 667Cc at this time has the highest “Earth Similarity Index” (ESI=0.85) of any known exoplanet:
http://phl.upr.edu/press-releases/apotentialhabitableexoplanetinanearbytriplestarsystem
Gerry,
The “consensus” view is not that low metallicity stars have no planets, it is that the likelihood of a planet forming around a star depends on the square of the metallicity. Indeed,
this heuristic law was derived from the observation of planets around both low, medium and high metallicity stars. The metallicity rule only states that there is a lower likelihood of finding planets around low metallicity stars.
What is interesting about this system is that you have a stable planet in the habitable-zone
in a triple star system:
Wikipedia states that GI 667 (HD156384) forms a triplet with the following characteristics:
The two brightest components of this system, Gl 667 A and Gl 667 B, are orbiting each other with a physical separation of about 12.6 AU. Their eccentric orbit brings the pair as close as about 5 AU to each other, or as distant as 20 AU, corresponding to an eccentricity of 0.6. This orbit takes approximately 42.15 years to complete and the orbital plane is inclined at an angle of 128° to the line of sight from the Earth.
The third component, Gl 667 C, orbits the Gl 667 AB pair with a physical separation of about 56 to 215 AU.
_____GJ 667 A is a K3V star with 0.73 Msun
_____GJ 667 B is a K5V star with 0.69 Msun
and__GJ 667 C is a M1.5V flare star with 0.31 Msun. It rotation period is 105 days, metallicity [Fe/H] = -0.59 and Age ~ 2 – 10 Gyrs.
It appears that the only system with known planets is GJ 667C
Planet__Mass____Semi-Major___Orbital Period___Eccentricity
__________________Axis__________(days)______________
b______5.68 M⊕___0.049____7.20066 ± 0.00067___0.172 ± 0.043
c______4.54 M⊕___0.123_______28.155 ± 0.017___<0.27
d (?)___5.65 M⊕___0.235___74.79 ± 0.13 / 91 ± 0.5__0 (fixed)
(Saturn?)__0.25 MJ__2.577________7100__________0 (fixed)
An M0V star will have tidal locking out to about 0.39 A.U., hence, there
are two possible strikes against GJ 667Cc being a site for complex life:
1. The parent star is a known flare star
2. The super-Earth-like planet is likely to tidally locked – i.e. it always presents the same face towards its sun or it will be a orbital-rotation period resonance like the planet mercury. This does not rule out the development of a complex civilization or even pre-sentient life, it just makes it more difficult.
Another interesting point is that there is tentative evidence for a Saturn-like planet (0.25 MJupiter) at 2.58 A.U. with a period of 19.45 years. If this is true then this system may be a good test of the V-E-J Tidal Torquing model. Though, I would add the caveat, that an M1V1.5 star would be getting close to having and interior that is completely convective and so planetary resonances may not be able to induce stellar activity the parent star as easily as an early G2V star like the Sun were only ~ 2% of the stars mass is in the convective envelope.
A much better candidate to test the V-E-J Tidal Torquing model would be HD 154345. This star is a lot like the Sun (it’s a G8V). Its planet (called HD 154345b) has a mass of no less than
0.95 times that of Jupiter, and orbits the star 4.2 AU, taking a little over 9 years to revolve around the star in a near-circular orbit.
Ninderthana,
Thanks for the information about HD 154345b. I see that the host star has been observed to have a magnetic and photometric activity cycle with the same apparent period as the radial velocity curve used to estimate the mass and orbital elements of its Jupiter-twin exoplanet!
This is rather astounding. Leif Svalgaard wrote, on page 20 of his Dec7, 2011 paper,
“Is Solar Activity Modulated by Astronomical Cycles?”
http://leif.org/research/AGU%20Fall%202011%20SH34B-08.pdf:
“The recent discovery of exoplanets and the possibility of detecting magnetic cycles on their host stars offers a near future test of the [planetary influence] hypothesis, based on more than the one exemplar, the solar system, we have had until now.”
Apparently Dr. Svalgaard was not aware that this test was actually performed to some extent in 2008, with somewhat positive results. Or perhaps he is aware of the finding, but has dismissed it on the grounds that “correlation is not causation.”
In The Astrophysical Journal, 683: L63–L66, 2008 August 10 paper, THE JUPITER TWIN HD 154345b,
http://iopscience.iop.org/1538-4357/683/1/L63/pdf/1538-4357_683_1_L63.pdf,
I now read
“We announce the discovery of a twin of Jupiter orbiting the slightly metal-poor ([Fe/H] p 0.1) nearby (d p 18 pc) G8 dwarf HD 154345. This planet has a minimum mass of 0.95 M and a 9.2 year, circular orbit with radius 4.2 AU. There is currently little or no evidence for other planets in the system, but smaller or exterior planets cannot yet be ruled out. We also detect a ~ 9 year activity cycle in this star photometrically and in chromospheric emission. We rule out activity cycles as the source of the radial velocity variations by comparison with other cycling late G dwarfs.”
NB: The activity cycle was ruled out as the source of the radial velocity variations, so that exoplanet b, with the same orbit period as the activity cycle, is therefore most likely the source.
“We monitor all of our program stars for variations in chromospheric
activity, extracting Mount Wilson S-indices from
our RV science spectra (H. Isaacson, in preparation; Wright et
al. 2004).We have found that HD 154345 shows clear evidence
of a stellar cycle. Figure 2 shows that the magnetic activity
level of HD 154345 varies sinusoidally with a ~ 9 year period.
Photometric monitoring from Fairborn Observatory (Henry
1999) confirms the presence of this activity cycle: Figure 3
shows a ~ 1 mmag photometric variation in phase with the
chromospheric emission.11”
Figures 1 and 2 show what appears to be a clear positive correlation between the activity cycle of HD 154345 and the orbit of HD 154345b:
“Fig. 2.–Mount Wilson activity index measured from RV science spectra
taken at Keck Observatory. Except for a few small discrepancies, the temporal
coverage of these data is the same as that of the RV data for both of these
stars. Data from prior to 2004 are taken from the “differential” measurements
inWright et al. (2004); subsequent data have been extracted in a similar manner
(H. Isaacson, in preparation). Both HD 154345 and the RV-stable star HD
185144 show strong evidence of activity cycles, although the cycle strength
and overall activity level in HD 185144 is considerably larger. Cycles such
as these are not uncommon in old G dwarfs, typically have ~10 year periods,
and are not observed to have an effect on long-term RV stability. Data for
the two stars are plotted on the same scale.”
Excellent spot Gerry! I’m making a new post for this one, stand by.