Newsgroups: sci.astro,sci.answers,news.answers Subject: [sci.astro] (Astronomy) Frequently Asked Questions (6/8) Followup-To: poster From: lazio@spacenet.tn.cornell.edu Summary: This posting addresses frequently asked questions about extraterrestrial life and the search for it. Approved: news-answers-request@MIT.EDU Last-modified: $Date: 1996/11/21 02:57:43 $ Version: $Revision: 2.1 $ URL: http://astrosun.tn.cornell.edu/students/lazio/sci.astro.html Posting-frequency: semi-monthly (Wednesday) Archive-name: astronomy/faq/part6 ------------------------------ Subject: Introduction sci.astro is a newsgroup devoted to the discussion of the science of astronomy. As such its content ranges from the Earth to the farthest reaches of the Universe. However, certain questions tend to appear fairly regularly. This document attempts to summarize answers to these questions. This document is posted on the first and third Wednesdays of each month to the newsgroup sci.astro. It is also available via anonymous ftp in the directory and it is on the World Wide Web at . Like many other FAQs it is also available from , , and their worldwide mirrors. Questions/comments/flames should be directed to the FAQ maintainer, Joseph Lazio (lazio@spacenet.tn.cornell.edu). ------------------------------ Subject: Copyright This document, as a collection, is Copyright 1995,1996 by T. Joseph W. Lazio (lazio@spacenet.tn.cornell.edu). The individual articles are copyright by the individual authors listed. All rights are reserved. Permission to use, copy and distribute this unmodified document by any means and for any purpose EXCEPT PROFIT PURPOSES is hereby granted, provided that both the above Copyright notice and this permission notice appear in all copies of the FAQ itself. Reproducing this FAQ by any means, included, but not limited to, printing, copying existing prints, publishing by electronic or other means, implies full agreement to the above non-profit-use clause, unless upon prior written permission of the authors. This FAQ is provided by the authors "as is," with all its faults. Any express or implied warranties, including, but not limited to, any implied warranties of merchantability, accuracy, or fitness for any particular purpose, are disclaimed. If you use the information in this document, in any way, you do so at your own risk. ------------------------------ Subject: F.00 Extraterrestrial Life [Dates in brackets are last edit.] F.01 What is life? F.02 Life in the Solar System 02.1 Is there life on Mars? [96-09-03] 02.2 Is there life in Jupiter (or Saturn)? [96-09-03] 02.3 Is there life on Jupiter's moon, Europa? [96-09-03] 02.4 Life on Titan? F.03 What is the Drake equation? [95-10-04] F.04 What is the Fermi paradox? [95-12-28] F.05 Could we detect extraterrestrial life? [96-11-20] F.06 How far away could we detect radio transmissions? [96-09-03] F.07 What is happening with SETI now? [96-04-20] See also the entry in Section G of the FAQ on the detection of extrasolar planets. ------------------------------ Subject: F.01 What is life? Author: none yet ------------------------------ Subject: F.02 Life in the Solar System Within the past 100--150 years, the conventional wisdom regarding life in the solar system (beside the Earth) has been on a roller coaster ride. Life on other planets used to be considered likely. Suggestions for sending messages to other planets included cutting down huge tracts in the Siberian forests or filling and setting afire trenches of kerosene in the Sahara. Lowell believed that he could see evidence for a civilization on Mars. During the Space Age the planets were explored with robotic craft. The images and other measurements sent back by these craft convinced most scientists that only the Earth harbored life. With even more recent findings, the possibility of life that life exists or existed elsewhere in the solar system is now being re-examined. ------------------------------ Subject: F.02.1 Is there life on Mars? Author: Steve Willner The Viking landers found conditions on the surface of Mars unlikely to support life as we know it. The mass spectrometer found too little carbon, which is the basis for organic molecules. The chemistry is apparently highly oxidizing as well. Some optimists have nevertheless argued that there still might be life on Mars, either below the surface or in surface regions not sampled by the landers, but most scientists consider life on Mars quite unlikely. Evidence of surface water suggests, however, that Mars had a wetter and possibly warmer climate in the past, and life might have existed then. If so, there might still be remnants (either living or fossil) today, but close examination will be necessary to find out. More recently, McKay et al. have invoked biological activity to explain a number of features detected in a meteorite from Mars. See for additional information. ------------------------------ Subject: F.02.2 Is there life in Jupiter (or Saturn)? Jupiter (and Saturn) has no solid surface, like the Earth. Rather the density and temperature increase with depth. The lack of solid surface need not be a deterrent to life, though, as many aquatic animals (e.g., fish, jellyfish) never touch a solid surface. There has been speculation that massive gas-bag organisms could exist in Jupiter's atmosphere. These organisms might be something like jellyfish, floating upon the atmospheric currents and eating either each other or the organic materials formed in Jupiter's atmosphere. ------------------------------ Subject: F.02.3 Is there life on Jupiter's moon, Europa? This article is adapted from NASA Press Releases. In the late 1970's, NASA Voyager spacecraft imaged Europa. Its surface was marked by complicated linear features, appearing like cracks or huge fractures in the surface. No large craters (more than five kilometers in diameter) were easily identifiable. One explanation for this appearance is that the surface is a thin ice crust overlying water or softer ice and that the linear features are fractures in that crust. Galileo images have reinforced the idea that Europa's surface is an ice-crust, showing places on Europa that resemble ice floes in Earth's polar regions, along with suggestions of geyser-like eruptions. Europa's appearance could result from the stresses of the contorting tidal effects of Jupiter's strong gravity (possibly combined with some internal heat from decay of radioactive elements). If the warmth generated by tidal heating is (or has been) enough to liquefy some portion of Europa, then the moon may have environmental niches warm and wet enough to host life. These niches might be similar to those found near ocean-floor vents on the Earth. ------------------------------ Subject: F.02.4 Life on Titan? ------------------------------ Subject: F.03 What is the Drake equation? Author: John Pike , Bill Arnett , Steve Willner There are various forms of it, but basically it is a means of doing boundary calculations for the prevalence of intelligent life in the universe. It might take the form of saying that if there are: X stars in the Galaxy, of which Y % have planets, of which Z % can support life, on which A % intelligent life has arisen, with B representing the average duration of civilizations then you fool around with the numbers to figure out how close on average the nearest civilization is. There are various mathematical expressions for this formula (see below), and there are variations on how many terms the equations include. The problem, of course, is that some of the variables are easy to pick (e.g., stars in the Galaxy), some are under study (e.g., how many stars have terrestrial-like planets), and others are just flat-out wild guesses (e.g., duration of civilization, where we are currently running an experiment to test this here on Terra of Sol). One useful form says the number of detectable civilizations is: N = R * fp * ne * fl * fi * fc * L where R = "the average rate of star formation in the region in question", fp = "the fraction of stars that form planets" ne = "the average number of planets hospitable to life per star" fl = "the fraction of those planets where life actually emerges" fi = "the fraction of life-bearing planets where life evolves into intelligent beings" fc = "the fraction of planets with intelligent creatures capable of interstellar communication" L = "the length of time that such a civilization remains detectable". (If you want some definition of civilization other than detectability, just change your definition of fc and L accordingly.) Can we provide reasonable estimates for any of the above numbers? The "social/biological" quantities are at best speculative and aren't appropriate for this newsgroup anyway. (See _Bioastronomy News_, Third Quarter 1995 for biologist Ernst Mayr's rather negative view of these. A copy of the article is at http://planetary.org/tps/mayr.html .) Even the "astronomical" numbers, though determinable in principle, have considerable uncertainty. Nevertheless, I will attempt to provide reasonable estimates. I'll take the "region in question" to be the Milky Way Galaxy and consider only cases "similar to" our solar system. For R, I'm going to use only stars with luminosities between half and double that of the Sun. Dimmer stars have a very small zone where Earth-like temperatures will be found, and more luminous stars have relatively short lifetimes. Near the Sun, there are about 4.5E-3 such stars in a cubic parsec. I'm only going to consider stars in the Galactic disk, which I take to have a scale height of 660 pc and scale length of between 5 and 8 kpc. (Stars outside the disk either have lower metallicity than the Sun or live in a very different environment and may have formed in a different way.) The Sun is about 8 kpc from the Galactic center, and thus in a region of lower than maximum star density. Putting everything together, there ought to be around 1.4E9 stars in the class defined. This represents about 1% of the total mass of the Galaxy. The age of the Sun is about 4.5E9 years, so the average rate of formation R is about 0.3 "solar like stars" per year. Planets are more problematic, since extrasolar planets cannot generally be detected, but it is thought that their formation is a natural and indeed inevitable part of star formation. For stars like the Sun, in fact, there is either observational evidence or clear theoretical justification for every stage of the planet formation process as it is currently understood. We might therefore be tempted to take fp=1 (for stars in the luminosity range defined), but we have to consider binary stars. A second star may disrupt planetary orbits or may somehow prevent planets forming in the first place. Because about 2/3 of the relevant stars are in binary systems, I'm going to take fp=1/3. Now we are pretty much out of the range of observation and into speculation. It seems reasonable to take ne=1 or even 1.5 on the basis of the Solar system (Earth and Mars), but a pessimist could surely take a smaller number. You can insert your own values for the probabilities, but if we arbitrarily set all of them equal to one N <= 0.1 L seems consistent with all known data. A more detailed discussion of interpretation of the Drake equation and the factors in it can be found in Issue 5 of SETIQuest. ------------------------------ Subject: F.04 What is the Fermi paradox? Author: John Pike , Steve Willner One of the problems that the Drake Equation produces is that if you take reasonable (some would say optimistic) numbers for everything up to the average duration of technological civilizations, then you are left with three possibilities: 1. If such civilizations last a long time, "They" should be _here_ (leading either the the Flying Saucer hypothesis---they are here and we are seeing them, or the Zoo Hypothesis---they are here and are hiding in obedience to the Prime Directive, which they observe with far greater fiqdelity than Captain Kirk could ever muster). -or- 2. If such civilizations last a long time, and "They" are not "here" then it becomes necessary to explain why each and every technological civilization has consistently chosen not to build starships. The first civilization to build starships would spread across the entire Galaxy on a timescale that is short relative to the age of the Galaxy. Perhaps they lose interest in space flight and building starships because they are spending all their time surfing the net. (Think about it---the whole point of space flight is the proposition that there are privileged spatial locations, and the whole point of the net is that physical location is more or less irrelevant.) -or- 3. Such civilizations do not last a long time, and blow themselves up or otherwise fall apart pretty quickly (... film at 11). Thus the Drake Equation produces what is called the Fermi Paradox (i.e., "Where are They?"), in that the implications of #3 and #2 are not terribly encouraging to some folks, but the two flavors of #1 are kinda hard to come to grips with. An alternate version of 2 is that interstellar travel is far more difficult than we think it is. Right now, it doesn't seem much beyond the boundaries of current technology to launch "generation ships," which amount to an O'Neill colony plus propulsion and power systems. An alternative is robot probes with artificial intelligence; these don't seem so difficult either. The Milky Way galaxy is well under 10^5 light years in diameter and over 10^9 years old, so even travel beginning fairly recently in Galactic history and proceeding well under the speed of light ought to have filled the Galaxy by now. (Travel very near the speed of light still seems very hard, but such high speed isn't necessary to fill the Galaxy with life.) The paradox, then, is that we don't observe evidence of anybody besides us. ------------------------------ Subject: F.05 Could we detect extraterrestrial life? Author: Steve Willner Yes, although present observations can do so only under optimistic assumptions. Radio and optical searches currently underway are aimed at detecting "beacons" built by putative advanced civilizations and intended to attract attention. More sensitive searches (e.g., Project Cyclops) that might detect normal activities of an advanced civilization (similar for example to our military radars or TV stations) have been proposed but so far not funded. No funding of these is likely until the search for beacons is far closer to being complete. Why get involved with the difficult until you are done with the easy? Ordinary astronomical observations are most unlikely to detect life. The kinds of life we speculate about would be near stars, and the light from the star would conceal most signs of life unless a special effort is made to look for them. Within the solar system, the Viking landers found conditions on the surface of Mars unlikely to support life as we know it. The mass spectrometer found too little carbon, which is the basis for organic molecules. The chemistry is apparently highly oxidizing as well. Some optimists have nevertheless argued that there still might be life on Mars, either below the surface or in surface regions not sampled by the landers, but most scientists consider life on Mars quite unlikely. Evidence of surface water suggests, however, that Mars had a wetter and possibly warmer climate in the past, and life might have existed then. If so, there might still be remnants (either living or fossil) today, but close examination will be necessary to find out. Other sites that conceivably could have life include the atmosphere of Jupiter (and perhaps Saturn) and the presumed liquid water under the surface ice of Jupiter's satellite Europa. Organisms living in either place would have to be very different from anything we know on Earth, and it's hard to know how one would even start to look for them. Concepts for specialized space missions that could detect Earth-like planets and return spectral information on their atmospheres have been suggested, and either NASA or ESA may launch such a mission some time in the next two decades (see and ). The evidence for life would be detection of ozone (implying oxygen) in the planet's atmosphere. While this would be strong evidence for life---oxygen in Earth's atmosphere is thought to have come from life---it would not be ironclad proof, as there may be some way an oxygen atmosphere could form without life. For more information, see references at the end of F.06. Also, check out the SETI Institute Web site at . A long article on detectability of various signals and more is at . ------------------------------ Subject: F.06 How far away could we detect radio transmissions? Author: Al Aburto Representative results are presented in Tables 1 and 2. The short answer is (1) Detection of broadband signals from Earth such as AM radio, FM radio, and television picture and sound would be extremely difficult even at a fraction of a Light-Year distant from the Sun. For example, a TV picture having 5 MHz of bandwidth and 5 MWatts of power could not be detected beyond 0.01 Light-Years of the Sun even with a radio telescope with 100 times the sensitivity of the 305 meter diameter Arecibo telescope. (2) Detection of narrowband signals is more resonable out to thousands of Light-Years distance from the Sun depending on the transmitter's EIRP and the receiving antenna size. (3) Instruments such as the Arecibo radio telescope could detect narrowband signals originating thousands of Light-Years from the Sun. (4) A well designed 12 ft diameter amateur radio telescope could detect narrowband signals from 30 to 300 Light-Years distance assuming the EIRP of the transmitter is in the terawatt range. What follows is a basic example for the estimation of radio and microwave detection ranges of interest to SETI. Minimum signal processing is assumed. For example an FFT can be used in the narrowband case and a bandpass filter in the broadband case (with center frequency at the right place of course). In addition it is assumed that the bandwidth of the receiver (Br) is constrained such that it is greater than or equal to the bandwidth of the transmitted signal (Bt) (that is, Br >= Bt). Assume a power Pt (watts) in bandwidth Bt (Hz) radiated isotropically. At a distance of R (meters), this power will be uniformly distributed (reduced) over a sphere of area: 4 * pi * R^2. The amount of this power received by an antenna of effective area Aer with bandwidth Br (Hz), where Br >= Bt, is therefore: Pr = Aer * (Pt / (4 * pi * R^2)) If the transmitting antenna is directive (that is, most of the available isotropic power is concentrated into a narrow beam) with power gain Gt in the desired direction then: Pr = Aer * ((Pt * Gt) / (4 * pi * R^2)) The transmit antenna gain, Gt, is given by the following expression: Gt = Aet * (4 * pi / (w^2)), where Aet = effective area of the transmitting antenna (m^2), and w = wavelength (m) the antenna is tuned to. f = c / w, where f is the frequency and c is the speed of light. c = 2.99793E+08 (m/sec) pi = 3.141592654 For a parabolic "dish" transmit or receive antenna: Aer = nr * pi * dr^2 / 4, and Aet = nt * pi * dt^2 / 4, where nt = efficiency of the transmit antenna nr = efficiency of the receive antenna dt = diameter (m) of the transmit "dish" antenna. dr = diameter (m) of the receive "dish" antenna. Similarly, the receiver gain Gr is given by: Gr = Aer * (4 * pi / (w^2)), but it is not used explicitly in the range equation. Only the effective area (Aer) intercepting the radiated energy at range R is required. The Nyquist noise, Pn, is given by: Pn = k * Tsys * Br, where k = Boltzmann's constant = 1.38054E-23 (joule/kelvin) Tsys = is the system temperature (kelvins), and Br = the receiver bandwidth (hertz). The signal-to-noise ratio, snr, is thus given by: snr = Pr / Pn. If we average the output for a time t, in order to reduce the variance of the noise, then one can improve the snr by a factor of sqrt(Br * t). Thus: snr = Pr * sqrt(Br * t) / Pn. The factor Br*t is called the "time bandwidth product," of the receive processing in this case, which we'll designate as: twp = Br * t. We'll designate the integration or averaging gain as: twc = sqrt(twp). Integration of the data (which means: twp = Br * t > 1, or t > (1 / Br) ) makes sense for unmodulated "CW" signals that are relatively stable over time in a relatively stationary (steady) noise field. On the other hand, integration of the data does not make sense for time-varying signals since this would distroy the information content of the signal. Thus for a modulated signal twp = Br * t = 1 is appropriate. In any case the snr can be rewritten as: snr = (Pt * Gt) * Aer * twc / (4 * pi * R^2 * Br * k * Tsys) Pt * Gt is called the Effective Isotropic Radiated Power (EIRP) in the transmitted signal of bandwidth Bt. So: EIRP = Pt * Gt, and snr = EIRP * Aer * twc / (4 * pi * R^2 * Br * k * Tsys) This is a basic equation that one can use to estimate SETI detection ranges. ####################################################################### # If Rl is the number of meters in a Light-Year # # (9.46055E+15 (m/LY)) then the detection range in Light-Years # # is given by: # # # # R = sqrt[ EIRP * Aer * twc / (4 * pi * snr * Br * k * Tsys) ] / Rl # # # # If we wanted the range in Astronomical Units then replace Rl # # with Ra = 1.496E+11 (m/AU). # ####################################################################### Note that for maximum detection range (R) one would want the transmit power (EIRP), the area of the receive antenna (Aer), and the time bandwidth product (twp) to be as big as possible. In addition one would want the snr, the receiver bandwidth (Br), and thus transmit signal bandwidth (Bt), and the receive system temperature (Tsys) to be as small as possible. Now we are in a position to carry out some simple estimates of detection range. These are shown in Table 1 for a variety of radio transmitters. We'll assume the receiver is a parabolic type ("dish") antenna, similar to Arecibo, with diameter dr = 305 m and an efficiency of 70% (nr = 0.7). We'll also assume snr = 3 is required for detection and that twp = Br * Tr = 1. Note that with more refined signal processing, the detection ranges could perhaps be increased by a factor of 2 to 3 over those shown in the table. An "educated" guess for some of the parameter values, Tsys in particular, was taken as indicated by the question marks in the table. As a reference note that Jupiter is 5.2 AU from the Sun and Pluto 39.4 AU, while the nearest star to the Sun is 4.3 LY away. Also note that signal attenuation due to the Earth's atmosphere and ionosphere have been ignored. AM radio for example, from Earth, is trapped within the ionosphere. The receive antenna area, Aer, is thus: Aer = nr * pi * dr^2 / 4 = 51,143.2 m^2 Hence the detection range (Light Years) becomes: R = 1.0478E-03 * sqrt[ EIRP / (Br * Tsys) ]. Table 1 Detection ranges of various EM emissions from Earth and the Pioneer spacecraft assuming a 305 meter diameter parabolic ("dish") receive antenna, similar to the Arecibo radio telescope. Assuming snr = 3, twp = Br * Tr = 1, nr = 0.7, and dr = 305 meters. -------------+--------------+-----------+--------+--------+-----------+ Source | Frequency | Bandwidth | Tsys | EIRP | Detection | | Range | (Br) |(Kelvin)| | Range (R) | -------------+--------------+-----------+--------+--------+-----------+ AM Radio | 530-1605 kHz | 10 kHz | 300 ? | 100 KW | 12 AU | -------------+--------------+-----------+--------+--------+-----------+ FM Radio | 88-108 MHz | 150 kHz | 100 ? | 5 MW | 38 AU | -------------+--------------+-----------+--------+--------+-----------+ UHF TV | 470-806 MHz | 6 MHz | 50 ? | 5 MW | 9 AU | Picture | | | | | | -------------+--------------+-----------+--------+--------+-----------+ UHF TV | 470-806 MHz | 0.1 Hz | 50 ? | 5 MW | 1.0 LY | Carrier | | | | | | -------------+--------------+-----------+--------+--------+-----------+ WSR-88D | 2.8 GHz | 0.63 MHz | 20 | 32 GW | 0.05 LY | Weather Radar| | | | | | -------------+--------------+-----------+--------+--------+-----------+ Arecibo | 2.380 GHz | 0.01 Hz | 20 | 22 TW | 10,990 LY | S-Band (CW) | | | | | | -------------+--------------+-----------+--------+--------+-----------+ Arecibo | 2.380 GHz | 0.01 Hz | 20 | 1 TW | 2,343 LY | S-Band (CW) | | | | | | -------------+--------------+-----------+--------+--------+-----------+ Arecibo | 2.380 GHz | 0.01 Hz | 20 | 1 GW | 74 LY | S-Band (CW) | | | | | | -------------+--------------+-----------+--------+--------+-----------+ Pioneer 10 | 2.295 GHz | 1.0 Hz | 20 | 1.6 kW | 593 AU | Carrier | | | | | | -------------+--------------+-----------+--------+--------+-----------+ It should be apparent then from these results that the detection of AM radio, FM radio, or TV pictures much beyond the orbit of Pluto will be extremely difficult even for an Arecibo like 305 meter diameter Radio Telescope! Even a 3000 meter diameter Radio Telescope could not detect the "I Love Lucy" TV show (re-runs) at a distance of 0.01 Light-Years! It is only the narrowband high intensity emissions from Earth (narrowband radar generally) that will be detectable at significant ranges (greater than 1 LY). Perhaps they'll show up very much like the narrowband, short duration, and non-repeating, signals observed by our SETI telescopes. Perhaps we should document all these "non-repeating" detections very carefully to see if any long term spatial detection patterns show up. Another question to consider is what an Amateur SETI radio telescope might achieve in terms of detection ranges using narrowband FFT processing. Detection ranges (LY) are given in Table 2 assuming a 12 ft (3.6576 m) dish antenna operating at 1.420 GHz, for various FFT binwidths (Br), Tsys, snr, time bandwidth products (twp = Br*t), and EIRP values. It appears from the table that effective amateur SETI explorations can be conducted out beyond approximately 30 Light-years provided the processing bandwidth is near the minimum (approximately 0.01 Hz), the system temperature is minimal (20 to 50 Degrees Kelvin), and the EIRP of the source (transmitter) is greater than approximately 25 terawatts. Table 2 Detection ranges (LY) for a 12 foot diameter amateur radio telescope SETI system, operating at 1.420 GHz. +-------------------------------+ | EIRP | +-------+--------+------+-------+ | 100TW | 25TW | 1TW | 100GW | -------+-------+----------+------+-------+--------+------+-------+ Br | Br*t | Tsys | snr | Detection Range | (Hz) | | (kelvin) | | (LY) | -------+-------+----------+------+-------+--------+------+-------+ 0.01 | 2 | 20 | 3 | 334 | 168 | 33 | 11 | -------+-------+----------+------+-------+--------+------+-------+ 0.01 | 1 | 20 | 3 | 281 | 141 | 28 | 9 | -------+-------+----------+------+-------+--------+------+-------+ 0.01 | 2 | 50 | 3 | 211 | 106 | 21 | 7 | -------+-------+----------+------+-------+--------+------+-------+ 0.01 | 1 | 50 | 3 | 178 | 89 | 18 | 6 | -------+-------+----------+------+-------+--------+------+-------+ 0.05 | 2 | 20 | 3 | 150 | 75 | 15 | 5 | -------+-------+----------+------+-------+--------+------+-------+ 0.05 | 1 | 20 | 3 | 126 | 63 | 13 | 4 | -------+-------+----------+------+-------+--------+------+-------+ 0.01 | 1 | 20 | 16 | 122 | 61 | 12 | 4 | -------+-------+----------+------+-------+--------+------+-------+ 0.1 | 20 | 50 | 3 | 119 | 59 | 12 | 4 | -------+-------+----------+------+-------+--------+------+-------+ 0.01 | 1 | 50 | 16 | 77 | 39 | 8 | 2 | -------+-------+----------+------+-------+--------+------+-------+ 1.0 | 200 | 50 | 3 | 67 | 33 | 7 | 2 | -------+-------+----------+------+-------+--------+------+-------+ 0.05 | 1 | 50 | 16 | 34 | 17 | 3 | 1 | -------+-------+----------+------+-------+--------+------+-------+ REFERENCES: Radio Astronomy, John D. Kraus, 2nd edition, Cygnus-Quasar Books, 1986, P.O. Box 85, Powell, Ohio, 43065. Radio Astronomy, J. L. Steinberg, J. Lequeux, McGraw-Hill Electronic Science Series, McGraw-Hill Book Company, Inc, 1963. Project Cyclops, ISBN 0-9650707-0-0, Reprinted 1996, by the SETI League and SETI Institute. Extraterrestrial Civilizations, Problems of Interstellar Communication, S. A. Kaplan, editor, 1971, NASA TT F-631 (TT 70-50081), page 88. ------------------------------ Subject: F.07 What is happening with SETI now? Author: Larry Klaes Some of the following material is from SETIQuest Magazine, copyright Helmers Publishing, and used by permission. For subscription or other information, contact Helmers Publishing, 174 Concord Street, Peterborough, NH 03458-0874. Phone (603) 924-9631, FAX (603) 924-7408, Internet: sqinqnet@pixelacres.mv.com or see http://www.setiquest.com/ . Project BETA (Billion-channel ExtraTerrestrial Assay) is a radio search begun 1995 October 30. It is sponsored by the Planetary Society and is an upgraded version of Project META (Million...). (Actually META I; see below for META II.) META I/BETA's observatory is the 26-meter radio antenna at Harvard, Massachusetts. Information at http://planetary.org/tps/meta_be.html seems to be old, but there are some nice pictures at http://www.setiquest.com/beta.htm . META II uses a 30-meter antenna at the Argentine Institute for Radio Astronomy, near Buenos Aires, Argentina. META I/II monitored 8.4 million channels at once with a spectral resolution of 0.05 Hz, an instantaneous bandwidth of 0.4 MHz, a total frequency coverage of 1.2 MHz, a maximum sensitivity of 7x10^-24 W m^-2, and a combined sky coverage of 93 percent. After five years of observations from the northern hemisphere and observing 6x10^13 different signals, META I found 34 candidates, or "alerts". Unfortunately, the data are insufficient to determine their real origin. Interestingly, the observed signals seem to cluster near the galactic plane, where the major density of Milky Way stars dwell. META II, after three years of observations and surveying the southern hemisphere sky almost three times, found nineteen signals with similar characteristics to the META I results. META II has also observed eighty nearby, main sequence stars (less than fifty light years from the Sun) that have the same physical characteristics as Earth's star. These observations were performed using the tracking mode for periods of one hour each at two different epochs. On 1992 October 12, NASA began its first SETI program called HRMS---High-Resolution Microwave Survey. Unfortunately for all, Congress decided the project was spending way too much money---even though it received less funds per year than your average big league sports star or film actor---and cut all money to NASA for SETI work. This act saved our national deficit by all of 0.0002 percent. Fortunately, NASA SETI was saved as a private venture called Project Phoenix and run by The SETI Institute. It operates between 1.0 and 3.2 GHz with 1 Hz resolution and 2.8E7 channels at a time. Earlier this year they completed a six-month survey of the Southern sky from Australia (no confirmed ETI signals) and are now trying to find another radio observatory which will help them scan the Northern skies. More details are in SETIQuest issue 3. The Project Phoenix home page is: http://www.seti-inst.edu/phoenix/Welcome.html . They have lots of general information about SETI as well as details of the survey. Since 1973, Ohio State University has conducted a radio search with a telescope consisting of a fixed parabolic reflector and a tiltable flat reflector, each about 110 m wide and 30 m high. Information is available at http://everest.eng.ohio-state.edu/~klein/ro/ or a longer version in SETIQuest issue 3 (also at http://www.setiquest.com/ohio.htm). The "wow" signal, detected in 1977, had the appearance of an extraterrestrial signal but was seen only briefly and never repeated. The latest news is bad, though. The University administration has decided to let the landlord who owns the property on which Big Ear resides tear down the radio telescopes and put up condos and a golf course instead, starting in 1998. Ironically it will cost more to tear the dishes down than to pay for their upkeep. OSU SETI is considering its next step, Project Argus, at an undetermined location. The UC Berkeley SETI Program, SERENDIP (Search for Extraterrestrial Radio Emissions from Nearby Developed Intelligent Populations) is an ongoing scientific research effort aimed at detecting radio signals from extraterrestrial civilizations. The project is the world's only "piggyback" SETI system, operating alongside simultaneously conducted conventional radio astronomy observations. SERENDIP is currently piggybacking on the 1,000-foot dish at Arecibo Observatory in Puerto Rico, the largest radio telescope in the world. Information at http://albert.ssl.berkeley.edu/serendip/ , from which this paragraph was extracted. SERENDIP operates at 430 MHz; more information is given in SETIQuest issue 3. Project BAMBI is an amateur SETI effort operating at a radio frequency of 4 GHz. See SETIQuest issue 5 for a status report. The Columbus Optical SETI Observatory uses visible light instead of radio waves. More information in SETIQuest issue 4 and at . Much of the work on "Optical SETI" comes from Dr. Stuart A. Kingsley , who also maintains BBS on Optical SETI. The Planetary Society maintains a list of online SETI-related material at http://planetary.org/tps/seti.html . And of course SETIQuest magazine, Larry Klaes, Editor. See subscription information above. Other references: Frank Drake, Dava Sobel, Is Anyone Out There: The Scientific Search For Extraterrestrial Intelligence, 1992, Delacorte Press, ISBN 0-385-30532-X. Frank White, The SETI Factor, 1990, Walker Publishing Company, Inc., ISBN 0-8027-1105-7. Donald Goldsmith and Tobias Owen, The Search For Life in the Universe, Second Edition, 1992, Addison-Wesley Publishing Company, Inc., ISBN 0-201-56949-3. Walter Sullivan, We Are Not Alone: The Continuing Search for Extraterrestrial Intelligence, 1993, Dutton, ISBN 0-525-93674-2. G. Seth Shostak, Editor, Progress In The Search For Extraterrestrial Life, 1993 Bioastronomy Symposium, Santa Cruz, California, 16--20 August 1993. Published in 1995 by The Astronomical Society of the Pacific (ASP). ISBN 0-937707-93-7.