Honing the search for alien civilizations

Please consider donating to Behind the Black, by giving either a one-time contribution or a regular subscription, as outlined in the tip jar to the right. Your support will allow me to continue covering science and culture as I have for the past twenty years, independent and free from any outside influence.

Worlds without end: In order to increase the odds of contacting extraterrestrial civilizations, astronomers have calculated the area in the sky where an alien-built Kepler could have seen the Earth transit the sun, thus increasing the chances that those alien-astronomers have discovered Earth and have tried to contact us.

“The key point of this strategy is that it confines the search area to a very small part of the sky. As a consequence, it might take us less than a human life span to find out whether or not there are extraterrestrial astronomers who have found the Earth. They may have detected Earth’s biogenic atmosphere and started to contact whoever is home,” explains René Heller from the MPS.

Not every star is equally well suited as a home of extraterrestrial life. The more massive a star, the shorter is its life span. Yet, a long stellar life is considered a prerequisite for the development of higher life forms. Therefore the researchers compiled a list of stars that are not only in the advantageous part of the sky but also offer good chances of hosting evolved forms of life, that is, intelligent life. The researchers compiled a list of 82 nearby Sun-like stars that satisfy their criteria. This catalogue can now serve as an immediate target list for SETI initiatives.


  • pzatchok

    Trouble getting to the link. But not your fault.

    I would think there would be three areas that would be best for detecting Earth.
    The Earth transit line which is along the plane of the orbit.
    And the two polar axis lines, North and South, for detecting the suns wobble as our planetary gas giants orbit it.

    The article might mention both though.

  • pzatchok

    Finally got there.

  • Edward

    Pzatchok wrote: “And the two polar axis lines, North and South, for detecting the suns wobble as our planetary gas giants orbit it.”

    That was the early method that was used, and it did not work so well from North and South, as the wobble was detected through Doppler shifts in the light rather than a change in position of the star. Masses of those planets were relative to the angle of the orbital plane.
    “Until the year 2014, the radial-velocity [Doppler] method was by far the most productive technique used by planet hunters.”

    About a year before they started finding exoplanets, I went to a talk on methods for finding planets and the advantages and disadvantages of each method. Doppler and transit were two that seemed most promising.

    A video embedded in the following link gives a nice description of how coronagraphs find hidden planets and can help examine their atmospheres. It seems to be a technology so far advanced that it is indistinguishable from magic.

    Wayne recently wrote in another post: “how Cool is all this!”

    Way cool!

  • wayne

    It’s all “Blow Your Mind” type Cool!

    Personally, I’m neutral on the Seti-type Projects, but fully support robotic exploration of the Solar System
    -Not seeing any warp-drive in the near future, so I vote we fully take over the Moon, colonize it, then onward to Mars.
    “Courage Boys! Who’s with me this?!

    Q: Does Alpha Centauri A, B, or C, have any detected Planets? At least it’s relatively “close.”
    What sort of vantage point do those 3 stars have, looking toward us?

  • pzatchok

    Thanks Edward.


    I’m with you. I would go for a mining colony on the Moon.

  • wayne

    Edward– always interesting idea’s and factoids to ponder.

    pzatchok wrote: “I would go for a mining colony on the Moon.”

    Absolutely with you on that. We need to figure out how to convert all the minerals into useful products, like oxygen, water, and rocket-fuel.
    –was listening to Mr. Z on The Space Show (from last year) discussing the engineering problems of going to the Moon vs. Mars. (I always thought “skipping the Moon,” as in Colonization, was a dead-end.)
    –I would advocate for a push ala the Clay Mathematics’ Institute Millennium Problems, but for Moon Colonization.
    (Personally, I want the USA to completely control the Moon & abrogate any Treaty’s we signed to the contrary. But that’s a whole different thread in itself.)
    –Big supporter of the Commercialization of Space movement. (Big opponent of crony’s & progressive’s getting their hands on the Moon or anything connected with Space.)
    [tangent– leery of Elon Musk & his crony electric-cars, but he appears to be getting his rockets in order, slowly but surely.]
    -If we can’t get our own house in order however, we’ll never go forth-boldly. And that includes engineering & politics.
    –Complete tangent– Anyone see the “Man In the High Castle” series on Netflix?

  • Edward

    Wayne asked: “Q: Does Alpha Centauri A, B, or C, have any detected Planets?”

    Excellent question. One study thought that they found a planet, but no one has yet been able to confirm it. Despite a solar system with multiple stars orbiting each other, computer simulations suggest that plants are possible, that they don’t get tugged away from their star by the other star, at least in the Alpha Centauri system.

    Wayne wrote: “I vote we fully take over the Moon, colonize it, then onward to Mars.”

    There have long been two schools of thought. I once argued for a return to the moon before going to Mars, but now I argue that commercial space should target the moon while Congress and NASA work on getting to Mars. I think, however, that commercial space will reach Mars before government, because governments are slow to action, and none are committed to doing the task — even the US is all talk and no plan or funding.

    NASA ideas usually involve a large, expensive craft, such as the Hermes in “The Martian.” An alternate idea was proposed a couple of decades ago, Mars Direct, which should be cheaper but may be harder on the crew. If commercial space goes to Mars first, then I would expect them to use a methodology similar to this.

    Colonizing the moon may be trickier than first glance indicates. The agriculture* would have to be protected from radiation, and there is not a magnetic field or atmosphere to help do it. It is not impossible, but it needs some solutions that currently seem expensive or impractical.

    Mars has more promise for colonization, as the agriculture may be a little easier. The atmosphere and magnetic fields are thinner than Earth’s, but they exist and provide more protection than the moon.

    It will be interesting to watch how the future history of the solar system plays out.

    * As in “The Martian,” we could define a colony as a place where people produce some, most, or all of their own food.

  • Steve Earle

    Whether we colonize the Moon or Mars (or Phobos, or Ceres, etc) the one thing we’ll need to succeed will be Water Ice.

    Wherever we can find accessible water ice should be our first target. It gives you water, oxygen, and hydrogen. From those building blocks you can build a colony.

    Once you have reasonably easy access to it, the rest of the job becomes much simpler, and more importantly less costly.

  • wayne

    Thanks, great points to ponder & research further! (I’m following most all of it.)

    Can you clue me in on the total-radiation-exposure, for astronauts travelling to Mars?
    I was under the impression that was a limiting factor on travel to Mars. (?)

    So, how far under the surface of the Moon would provide an adequate radiation shield?
    Do we have any clue on the engineering involved in digging on the Moon?

    How difficult is it to dump heat on the Moon & is that a problem?– as-in, if we use some form of nuclear power, like RTG’s or even a small reactor, does that produce a heat problem or can we utilize that?
    Are there engineering upsides with nuclear, in a low-gravity, vacuum environment?

    Any studies on extracting oxygen, hydrogen, etc., from the Mar’s atmosphere? (We do air liquefaction on Earth. Is that electric-intensive?)

    Yes– agree that Big-Space is not quick, efficient, or bold, in large part.

  • Steve Earle

    I can’t speak to the Engineering aspects, but my common sense tells me that we will need to use compact, reliable sources of electricity to make any colony work. That would probably be a combo of RTG’s and PhotoVoltaic panels.

    If you parked next to water ice you could also use fuel-cells, but I am not sure if that would be efficient enough to bother with. In an ideal world, you break down the existing water to make Oxygen and Hydrogen, then use the excess to turn back into electricity and drinking water using a fuel cell. I am guessing that would be very “lossy” in real life?

    I also guess that it would be a lot easier to use the existing ice than try and extract from the atmosphere. All the more reason that Ice is the Key no matter where we go. It should be the number one search priority, even the Moon has some hidden away at the poles hopefully.

    And, IIRC, even after the trip there, the radiation exposure on Mars would also require caves or other shielding, since it does not have a magnetic field for protection.

  • Edward

    What a lot of questions, wayne!

    There is some concern that the total radiation dose gets close to NASA’s limits, but there may be solutions:

    There were suggestions, decades ago, that two or three feet of lunar regolith placed over lunar habitats would be sufficient radiation shielding for humans. Agriculture could be different, as we would want the sunlight to come through but not much of any other radiation, so putting regolith over the “fields” may be less desirable. The regolith is very much like sand, so digging it is relatively easy. There is no need to dig underground habitats (and I once read a suggestion that large “3D printers” build up habitats from the lunar soil), but last year, Robert posted an article about lava tubes from ancient lava flows.

    Heat rejection would not be much more difficult than it is on a satellite. The radiative surface would look into deep space and would need to be shaded from the sun, Earth, and the lunar surface. Alternatively, depending upon the temperature of the lower parts of lunar soil or rock, waste heat may be able to be dumped into the moon itself.

    Nuclear power may be more of a political problem than using solar arrays (photo voltaic panels). I would count on solar arrays as a major power source, but something will have to be there for night time (two weeks!) and emergency backup. Maybe batteries, capacitors, or nuclear plants — maybe we will have compact fusion by then (or am I dreaming?). I like Steve’s suggestion of fuel cells, depending upon how “lossy” batteries or capacitors are. However, nuclear power plants, such as RTGs, would best be located a little way away from the habitat/base/colony.

    There is serious evidence that salty water exists on Mars, just below the surface, and Steve is right that there is serious evidence that there is water ice in a crater at the south pole of the Moon.

    Mars’s atmosphere is mostly CO2, so a little energy can extract oxygen for use to breath or for propellant. Not much hydrogen has been found on Mars, but the subterranean (submarsean?) water would be a good source.

  • wayne

    Edward My Man!

    Appreciate the links– I’ve actually been utilizing the Search-feature more & more. There is a wealth of information archived here!
    Yeah….I do ask a lot of questions, (HAR) partially just force-of-habit & thinking “out-loud.”
    You have no idea my friend, how often I get sidetracked on interesting stuff, while on my way to research other interesting stuff!

    Again, truly appreciate your efforts! Always interesting!

Leave a Reply

Your email address will not be published. Required fields are marked *