During the past five years we have pursued the detection of extrasolar planets by the photometric transit method, i.e. the detection of a planet by watching for a drop in the brightness of the light as it crosses in front of a star. The planetary orbit must cross the line-of-sight and so most systems will not be lined up for such a transit to ever occur. However, we have looked at eclipsing binary systems which are already edge-on. Such systems must be very small in size as this makes the differential light change due to a transit much greater for a given planet size (the brightness difference will be proportional to the area of the transiting planet to the disc area of the star). Also, the planet forming region should be closer to the star as small stars are generally less luminous (that is, if the same thermal regime for planet formation applies as in the solar system). This led to studies of the habitable zone around other stars, as well. Finally, we discovered that our data could be used to detect giant planets without transits as we had been carefully timing the eclipses of the stars (using a GPS antenna for time) and this will drift by being offset by any giant planets orbiting around the system, as well. The best summary of our work may be to just summarize the 21 refereed papers produced during the time of this grant. This will be done is chronological order and in each section separately

Doyle, Laurance R.

English

NASA Technical Reports Server

"7 B
Final Technical Report
NASA Cooperative Agreement NCC2-874
"TRANSIT OF EXTRASOLAR PLANETS"
June 16, 1998
by
Laurance R. Doyle,
Principal Investigator
SETI Institute
https://ntrs.nasa.gov/search.jsp?R=19990028492 2020-06-15T22:32:50+00:00Z
Final Report on NCC 2-874: Transit of Extrasolar Planets
L.R. Doyle, SETI Institute June 1998
During the past five years we have pursued the detection of extrasolar
planets by the photometric transit method, i.e. the detection of a planet by
watching for a drop in the brightness of the light as it crosses in front of a star.
The planetary orbit must cross the line-of-sight and so most systems will not be
lined up for such a transit to ever occur. However, we have looked at eclipsing
binary systems which are already edge-on. Such systems must be very small in
size as this makes the differential light change due to a transit much greater for
a given planet size (the brightness difference will be proportional to the area of
the transiting planet to the disc area of the star). Also, the planet forming region
should be closer to the star as small stars are generally less luminous (that is, if
the same thermal regime for planet formation applies as in the solar system).
This led to studies of the habitable zone around other stars, as well. Finally, we
discovered that our data could be used to detect giant planets without transits
as we had been carefully timing the eclipses of the stars (using a GPS antenna
for time) and this will drift by being offset by any giant planets orbiting around
the system, as well.
The best summary of our work may be to just summarize the 21 refereed
papers produced during the time of this grant. This will be done is chronological
order and in each section separately.
Detection of Extrasolar Planets (papers 1-12)
Paper 12 by Hale and Doyle is essentially a catalogue of the space orientation of stars
determined by using their Calcium II H & K-line emission to get the periods of rotation (P) of each
star. From the rotational velocity (V sin i, where V = rotational velocity and i = rotational axis
inclination from the line-of-sight) and the circumference of the star of radius R, one can get the
star's inclination toward or away from the observer using 2_r / P = V, and V sin i / V = sin i. Dr. Hale
and I obtained a list of likely edge-on systems in this way in which the photometric method could
be applied. Incidentally, every system around which planets have been discovered since has
been contained in our catalogue list of likely candidates.
Paper 11 by Schneider and Doyle outlines a Iroadmap for the transit detection of Earth-
like planets around some very special small-mass eclipsing binaries. Inthis work we show that
precessional damping will occur within the protoplanetary disc so that as planets form they should
collisionally damp into the binary orbital plane. Example systems to be observed, and possible
follow-up observations to detect exobiology are also outlined. This paper announced the
organization of the TEP (Transit of Extrasolar Planets) observing network, with participating
observatories in California, Korea, Russia, Crete, France, Canary Islands, New York, and New
Mexico, which the authors organized.
Paper 10 of Brandmeier and Doyle is the first paper showing the quasi-periodicity of
planetary transits around eclipsing binary stars. This lead to the development of a transit detection
algorithm to cross correlate all possible transit models that could take place around eclipsing binary
stars of a given type (varying phase and periods of the planets and stars).
Paper 9 by Jenkins, Doyle, and Cullers is the actual transit detection algorithm developed
along the lines of signal detection theory. We had preliminarily characterized the observational
noise as white and Gaussian (WGN) but later found it to be a bit red. Nevertheless, in this paper we
showed that Earth-sized planets could indeed be detected using ground-based 1-meter-class
telescopes photometrically.
Paper 8 by Doyle et al. reported on the actual characteristics of observational data taken at
the University of California's Lick Observatory Crossley O.9-meter reflector. At his time we had
hundreds of hours of observing time and were able to characterize the noise well, and place limits
on extrasolar planets around the smallest star in our sample, CM Drac, of sizes a bit smaller than
Neptune (which is about the detection limit of most other systems). We also here pointed out that
giant planets could be detected without transits just by GPS timing eclipses of the binary stars
well.
Paper 7 is a semi-technical article aimed at the advanced amateur astronomy community to
point out to them that with 1% photometric CCD capabilities and a GPS timing chip in their data
acquisition computers, they could participate in the detection of jovian mass planets.
Paper 6 is a report by one of the TEP network observatories on multicolor photometry and
flare activity of CM Draconis (one of the many astrophysical asides of the data when looking for
extrasolar planets).
Paper 5 is a report from the Canary Islands node of the TEP Network regarding the
characterization of our d_ta reduction software and processes. As part of the effort, we invented
new aperture photometry software tools that have been incorporated into the National Optical
Astronomy Observatory's IRAF image processing package and is available on the TEP Network
web site.
Paper 4 outlines the process and procedure of calibrating and reducing multi-site
photometry and integrating it into one common light curve. We rejected all data that was of a
precision worse than about 0.8%.
Paper 3 is a demonstration of the jovian planets detection method along with data
obtained at Lick Observatory and the Canary Islands Observatory for about 15 small mass
eclipsing binaries. In this article we put limits on the presence of any jovian-to-brown-dwarf masses
around these stars.
Paper 2 is a 5-year report on the 1000+ hours of observations taken to date by the TEP
network including a full description of the data, its noise characteristics, the observatories,
telescopes, and phase coverage of possible planets these observations have achieved to date.
Paper I is a final report (if not funding is obtained) on the CM Drac Earth-like planets
detection limits we have reached. It shows that Earth-like planets can indeed be detected from the
ground using 1-meter-class telescopes around selected stars. The limit we report here is for 3-
Earth Radii planets being detectable at the 90% confidence level (this is a planet 2% the size of
Jupiter!)
Circumstellar Habitable Zones [papers 13-19)
Paper 19 outlines a theory to explain how liquid water could have existed on early Mars,
while also necessarily addressing the problem of the solar lithium depletion, excess heavy
element abundances in older lunar soils, and Venus' early ocean loss. We proposed that the early
Sun could have been 3-7% more massive.
Paper 18 addresses the stellar considerations of the history of the young Solar System,
specifically showing that if young solar-type stars lose a small percentage of their masses this can
be detected at radio wavelengths.
Paper 17 argues that the best solution to liquid water on early Mars might be early solar
mass loss as the idea of condensation of greenhouse gasses due to the early dimmer Sun as well
as substitution of other atmospheric greenhouse constituents is not viable as an explanation of
liquid water on early Mars.
Paper16reportsVLAmuitispectralradioobservationsofyoungsolartypestarswithlimits
ontheirpossiblemasslossrate.Whilethisstudywasnotconclusiveasyet,it demonstratedthat
suchradioobservationsareindeedcapableofdetectingsuchamasslossrateandsocould
confirmif,ingeneral,youngsolar-typestarsdohaveslightlymoremasswhenyoungcomparedto
theirlatermain-sequencelifetimes.Thiswouldhavesignificantrepercussionsforour
understandingofthehistoryoftheSolarSystem,includingtheoriginofbiologicalsystems.
Paper15is533-page62-authorvolumewhichwe refereed and edited. It is the result of a
conference we organized and held at NASA Ames Research Center in Moffett Field, California.
Paper 14 is a review article over viewing the current state of the field of Circumstellar
Habitable Zones, with updates in may of the related multi-disciplinary fields.
Paper 13 is an article addressing the problem of complex photosynthetic biological
habitability around M-stars (i.e. stars in which the peak flux is in the infrared and any planets in the
habitable zone will be tidally locked in rotation). We are, as far as we know, the first to address this
interesting problem; of some significance since as much as 75% of stars may be M-spectral-type
dwarfs stars.
Peripherally related work [papers 20-21]
Paper 21 reviews all the work done on archaeoastronomy in sub-Saharan Africa. As this
grant has not been fully funded, as a part time job, the author taught History of Science as a
visiting professor at Principia College in Illinois, and this paper is the result of some of that
research, as well as two expeditions to Africa he led at an earlier time with Mr. Frank.
Paper 20 introduces a new tool for objectively intercomparing various species
vocalizations. It does this by using Information Theory statistics (originally developed for
telephone line capacity measures) to the analysis of dolphin whistle vocalizations, also showing
their applicability to other diverse species.
One can see that many basic scientific breakthroughs in various field have been made
through this agreement over the past five years. An average of over 4 refereed paper per year
during this time demonstrates out'productivity. Given that during this time period two NASA Ames
Research Center Director's Discretionary Funds ($40K per year for two years) and a special $5K
grant were our only sources of funding, this might be viewed as particularly remarkable.
References
1) Doyle, L.R., H.-J. Deeg, J.M. Jenkins, V. P. Kozhevnikov, E. Martin. E. Palaiologou, J. Schneider, Z.
Ninkov, L. Rottler, "Detectability Limits on Habitable-Sized Planets Around CM Draconis," to be
submitted to Astronomical Journal..
2) Deeg, H.-J., L.R. Doyle, V. P. Kozhevnikov, E. Martin, E. Palaiologou, J. Schneider, C. Afonso, E.T.
Dunham, J.M. Jenkins, Z. Ninkov, R. Stone, and P.E. Zakharova, 1998, "A Photometric Search for
Transits of Extrasolar Planets: Observations and Photometric Analysis of CM Draconis," Astronomy &
Astrophysics, in press.
3) Doyle, L.R., H.-J. Deeg, J.M. Jenkins, J. Schneider, Z. Ninkov, R. P.S. Stone, J.E. Blue, H. G_tzger,
B, Friedman, and M.F. Doyle, 1998, "Detectability of Jupiter-to-Brown-Dwarf-Mass Companions Around
Small Eclipsing Binary Systems," in Brown Dwarfs and Extrasolar Planets, A.S.P. Conference
Proceedings, in Brown Dwarfs and ExIrasolar Planets, R. Rebolo, E. L. Martin, and M.R.Z. Osorio (eds.),
A.S.P. Conference Series 134, San Francisco, California, 224-231.
4) Martin, EL., H. Deeg, L.Doyle, and J. Schneider, 1998, "Planets in CM Dracoins: A Multi-Site
Photometric Approach," in Infrared Space lnterferometry: Astrophysics and the Study of Earth-Like Planets,
C. Eiroa et. al. (eds.), Kluwer Academic Pub. 215, 59.
5)Deeg,H.-J.,E.Martin.J.Schneider,M.Chevreton,L.R.Doyle,J.M.Jenkins,Z.Ninkov,1997,
"ObservationstoDetectTerrestrialPlanetsMoundCMDraconis,Astron.& Ap. Tr.ans, 23, 23-43.
6) Kim, S.-L., M.-V. Chun. W.-B. Lee, and L.R. Doyle, 1997, "CM Draconis Flare Detection," Intnl.
Bull. Variable Stars, No. 4462.
7) Doyle, L.R., 1996, "In the Wink of a Star," Mercu_, May/June, 51-53.
8) Doyle, L.R., E.T. Dunham, H.-J. Deeg, J.E. Blue, and J.M. Jenkins, 1996, "Ground-Based Detection of
Terrestrial-Sized Extrasolar Planets: U.C. Lick Observations of CM Draconis," J.G.R. Planets, 101,
14823-14829.
9) Jenkins, J.M., L.R. Doyle, and K. Cullers, 1996, "A Masked-Filter Method for Ground-Based Sub-
Noise Detection of Extrasolar Planets in Eclipsing Binaries: Application to CM Draconis," Icarus, 119,
244-260.
10) Brandmeier, S, and L.R. Doyle, 1996, "Modeling of Extrasolar Planetary Transits in Eclipsing Binary
Systems," Circumstellar Habitable Zones: Proceedings of the First International Conference, Travis House
Publications, Menlo Park, CA, 251-263.
11) Schneider, J. and L.R. Doyle, 1995, "Ground-Based Detection of Terrestrial Extrasolar Planets By
Photometry: The Case For CM Draconis," Earth, Moon, and Planets, 71, 153-173.
12) Hale, A., and L.R. Doyle, 1994, "The Photometric Detection of Extrasolar Planets Revisited,"
Astrophy. & Space. Sci. 212, 335-341.
13) Heath, M., L.R. Doyle, M.M. Joshi, and R. Haberle, 1998, "Habitable Zones Around M-Dwarf
Stars,"Origins of Life, in press.
14) Doyle, L.R., J. Billingham, and D.L. DeVincenzi, 1998, "Circumstellar Habitable Zones: An
Overview," Acta Astronautica, in press.
15) Doyle, L.R., 1996, (Ed.), Circumstellar Habitable Zones: Proceedings of the First International
Conference, Travis House Publications, Menlo Park, CA.
16) Doyle, L.R., N.C. Heather, R. Vikramsingh, and D.P. Whitmire, 1996, "Early Solar Mass Loss and
the Solar System Habitable Zone," in Circumstellar Habitable Zones: Proceedings of the First International
Conference, (ed) L.R. Doyle, Travis House Publications, Menlo Park, CA, 157-179.
17) Whitmire, D.P., L.R. Doyle, R.T. Reynolds, JJ. Matese, 1995, "A Slightly More Massive Sun as an
Explanation of Warm Temperatures on Early Mars, ", J. G. R. Planets 100, 5457-5464.
18) Doyle, L.R., R. Vikramsingh, D.P. Whitmire, and N.C. Heather, 1995, "Circumstellar Habitable
Zones and Mass Loss from Young Solar-Type Stars. II. Observational Considerations," in Progress in the
Search for Extraterrestrial Life, A.S.P. Conf. Series 74, (ed) S. Shostak, 195-204.
19) Whitmire, D.P., L.R. Doyle, J.J. Matese, and R.T. Reynolds, 1995, "Circumstellar Habitable Zones
and Mass Loss from Young Solar-Type Stars. I. Theory," in Progress in the Search for Extraterrestrial Life,
A.S.P. Conf. Series 74, (ed) S. Shostak, 183-193.
20) McCowan, B., S.F. Hanser, and L.R. Doyle, 1998, "A Quantitative Tool for Comparing Animal
Communication Systems: Information Theory Applied to Bottlenose Dolphin Whistle
Vocalizations,"Anbnal Behavoir, in press.
21) Doyle, L.R. and E.W. Frank, 1997, "Astronomy of Africa," in Encyclopedia of the History of Science,
Technology and Medicine in Non-Western Cultures, H. Selin (ed.), Kluwer, Netherlands, 96-99.


Transit of Extrasolar Planets

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