Radio Waves From Earth Have Reached Dozens of Stars (technologyreview.com) 51
For billions of years, Earth has been playing a cosmic game of hide-and-seek. New research published today in Nature posits that roughly 1,700 stars are in the right position to have spotted life on Earth as early as 5,000 years ago. From a report: These stars, within 100 parsecs (or about 326 light-years) of the sun, were found using data from NASA's Transiting Exoplanet Survey Satellite and the European Space Agency's Gaia mission. And with thousands of exoplanets already found orbiting other stars in our universe, could we have already seen life on other planets come and go? Might they have seen us? "The universe is dynamic," says Lisa Kaltenegger, director of the Carl Sagan Institute at Cornell, and lead author of the study. "Stars move, we move. First the Earth moves around the sun, but the sun moves around the center of our galaxy."
About 70% of exoplanets are found using the transit method: when a planet passes between a star and an observer, the star dims enough to confirm the presence of a previously unseen celestial body. Kaltenegger and coauthor Jackie Faherty of the American Museum of Natural History compiled a list of stars that either will see or already have seen Earth transit in their lifetimes. Of these, they found seven stars with orbiting exoplanets that could potentially be habitable. Statistically, one out of four stars has a planet that exists in the "Goldilocks zone" -- not too hot, not too cold, and just far away from a star to support life. But how do we determine whether faraway exoplanets meet these criteria? When transiting exoplanets block stellar light, part of that light filters through the atmosphere. Energy and light interact with the molecules and atoms of that planet, and by the time that light reaches an astronomer's telescope, scientists can determine whether it has interacted with chemicals like oxygen or methane. A combination of those two, Kaltenegger says, is the fingerprint for life.
About 70% of exoplanets are found using the transit method: when a planet passes between a star and an observer, the star dims enough to confirm the presence of a previously unseen celestial body. Kaltenegger and coauthor Jackie Faherty of the American Museum of Natural History compiled a list of stars that either will see or already have seen Earth transit in their lifetimes. Of these, they found seven stars with orbiting exoplanets that could potentially be habitable. Statistically, one out of four stars has a planet that exists in the "Goldilocks zone" -- not too hot, not too cold, and just far away from a star to support life. But how do we determine whether faraway exoplanets meet these criteria? When transiting exoplanets block stellar light, part of that light filters through the atmosphere. Energy and light interact with the molecules and atoms of that planet, and by the time that light reaches an astronomer's telescope, scientists can determine whether it has interacted with chemicals like oxygen or methane. A combination of those two, Kaltenegger says, is the fingerprint for life.
Trans (Score:3)
I don't know if they're there yet, but improved monitoring of transit of a planet past a sun could, in theory, reveal a gas spectrograph of the atmosphere, which differs from the pure sun's, thus revealing chemicals that not just support life, but are direct evidence of it.
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Aside from the potential for Lrrr to want reruns of Single Female Lawyer, the chances of anybody listening for such faint emissions is vanishingly low.
Erath, with all of it's radio telescopes, only looks at a very narrow 'water band' of the EM spectrum
Re:Trans (Score:5, Interesting)
*ahem* I meant Earth... and the SETI effort around the 'Water Hole'
Does anybody know if SETI or another search effort is looking into the more common radio frequencies?
THE RATIONALE FOR A PREFERRED FREQUENCY BAND:
THE WATER HOLE
[65] Seventeen years ago Cocconi and Morrison (ref. 1) suggested that we search at frequencies near the hydrogen line for signals emitted by advanced extraterrestrial civilizations attempting to establish contact with us. At the time, the hydrogen line was believed to be unique but, since then, dozens of other microwave emission lines from a wide variety of interstellar molecules have been discovered. In 1971 the Cyclops study (ref. 2), for reasons that are believed to be rather fundamental, identified the band between 1400 and 1727 MHz bounded at the low end by the hydrogen line (1420 MHz) and at the high end by the hydroxyl lines (1612 to 1720 MHz) as a prime region of the spectrum to be searched for interstellar signals. Because of these limiting markers the Cyclops team dubbed this region the "water hole" and suggested that different galactic species might meet there just as different terrestrial species have always met at more mundane water holes.
At present there is no serious interference in the water hole but navigational satellites and other systems are being planned that would fill the band with interfering signals such as continuous pseudo-random wide band noise. If these systems become operational as allocated, a substantial fraction if not all of the water hole may be rendered unusable for the search. The proposed services can be shifted to other frequencies without appreciable loss of effectiveness but, if the rationale for the water hole is correct, the search for intelligent extraterrestrial life cannot. It would be a bitter irony if the desire to know exactly where we were at all times on Earth were to prevent us from ever knowing where we are with respect to other life in the Galaxy. It is therefore timely to reexamine the case for the water hole in order that we do not, out of ignorance or carelessness, forever blind ourselves to the signals from advanced societies (see Sections III-8 and III-9).
The basic premise that leads us to the water hole is that any advanced society wishing to establish contact will choose the least expensive means that will nevertheless ensure success. As we shall see, one of the dominating factors is the energy that must be expended by the society to announce its existence over interstellar distances, not just to us but to all likely planetary systems. It is this consideration that leads to the radiation of electromagnetic waves rather than probes or spaceships and to the spectral region of the water hole.
https://history.nasa.gov/SP-41... [nasa.gov]
Headline has nothing to do with the article (Score:4, Informative)
The headline seems to have nothing to do with the article. The headline is about radio waves produced by humans. The article is about observing transits by the Earth from distant stars.
Knowing that radio signals from Earth have reached distant stars is trivial, of course. All you need to know is the speed of light, the distance to stars, and the date when Earth radio signals started broadcasting. if you say the first broadcast of not-trivial power was the 1910 public broadcast by Lee de Forest, then signals from Earth have reached all the stars within 101 light years. (Of course, the signal would have been far too weak to detect, but that wasn't the question a phrased.)
... in terms of the question asked in the comment, yes of course SETI searches search the frequencies suggested by Cocconi and Morrison in 1959. And, since many researchers suggest that we don't know how other civilizations might choose a frequency, they search many other frequencies as well.
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> In 1960, a radioastronomer named Frank D. Drake was the first person to try to detect interstellar radio transmissions, focusing on two stars 11 light-years away and similar in age to our sun. Though that attempt was unsuccessful, scientists and amateur enthusiasts have continued to look for such signals ever since.
> But whether the signals we send are getting through is another matter entirely. In the new study, Kaltenegger and Faherty reported that human-made radio waves had already swept over the
They are sending probes to find out (Score:5, Funny)
...if we are delicious.
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Either that or they open a worm hole to our solar system which they want to turn into a Dyson sphere [wikipedia.org] so they can hide from their nemsis.
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some of the best drugs are incompatible or harmful to our own biology.
God help us. (Score:3)
When the first episodes of Jerry Springer start reaching them, we're fucked.
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Don't worry, the Kardiashian show will frighten them away. Their booties are our scarecrows.
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Don't worry, the Kardiashian show will frighten them away. Their booties are our scarecrows.
Came here to post this.
If the first radio broadcast [www.ieee.ca] is reaching them right now, then it will be 106 years until they're hit with Keeping up with the Kardashians [wikipedia.org].
Which is when they'll start launching the attack fleets.
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So they are not keeping up with the Kardashians. Damned "c".
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Don't worry, the Kardiashian show will frighten them away. Their booties are our scarecrows.
No, it's the I Love Lucy episodes that are causing them to attack in the first place. Finding out about the Kardashians will turn our punishment from slavery to genocide.
Re:God help us. (Score:5, Insightful)
When the first episodes of Jerry Springer start reaching them, we're fucked.
I take it you haven't seen the movie Contact. [youtube.com]
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Inverse Square (Score:5, Insightful)
Being Radio Waves don't spread like a Laser but disperse over an area, it would mean while they could indeed make it to other stars, they would be so over powered by other interference that its communication would be mathematically unreadable. At best a close by star might, be able to determine that the Sol system may have a bit higher than average radio static, but I am unsure, if it would be out of the normal margin of error.
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Closest star is proxima, about 4 light years and we have picked up clear radio signals from there. Not saying that Podunk local radio is going to make it, but the 1400 kW transmitter in Roumoules, France should be able to make it, I think.
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How much stronger are radio emissions from a star compared to a human radio station?
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How much stronger are radio emissions from a star compared to a human radio station?
What wavelength and how directional is the antenna? It’s almost trivial to exceed the power of a star when your beam is narrowly focused and there isn’t much activity in that band anyhow.
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Are you suggesting that someone is wasting cash beaming radio signals directly into space instead of to terrestrial antennas?
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Like AM radio does? Their real waste is hiring moron pundits.
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If I had a megabuck a year to play with, I might choose to invest in beaming radio waves at (say) the hundred closest stars, carrying a fairly simple message ("here's a signal, here's something wildly improbable to be accidental, ..." and have to figure out how to send a "red flag" message, conveying the concept "don't do what we did").
Your "waste" ; my "investment".
Re:Inverse Square (Score:4, Interesting)
You might be surprised how good we are at recovering signals from noise. For example LoRA networks work with signals below the noise floor.
I think there's a decent chance that someone receiving those signals could at least detect that there is some sort of artificial signal there, even if they can't recover it into anything useful.
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You might be surprised how good we are at recovering signals from noise.
And you might be surprised at how low the received power is at a distance of ten to the seventeenth or ten to the eighteenth meters.
Re: Inverse Square (Score:2)
So with inverse square law, signal "only" one million times stronger (in radiant power, eg watts per steradian) transmitted from a planet in next star system would be potentially detectable and decodable.
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There's another possible transmission window up in the THz range (far IR to short microwave) IIRC, but I don't think we have transmitters that can get to the necessary power level (to out-shine the Sun) at reasonable price.
Yet.
People do work on it. (But as of ~ten years ago, they were running into problems in their science work
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For example, a single sideband signal on a carrier. It's relatively easy to generate reasonably clean radio signals, and if they blend, you'd get a double sideband signal, again "relatively easily", naturally. But a single sideband? Much, much harder.
Being able to decode a signal from that requires a considerably higher signal to noise ratio, but that there is an odd pattern of signal stren
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All true, but as someone pointed out above, only the headline mentions radio; the article talks about detecting transits of the Sun by the Earth from other stars, out to 100 parsecs = 326 light years. And 326 years ago, Newton had only recently published Principia. So no radio broadcasts.
Show me (Score:2)
Those poor aliens (Score:2)
No Netflix nor Amazon ever, only Allo, Allo and I love Lucy.
How many are we missing? (Score:1)
I've read about the transit method before, but I was just wondering how many planets might be out there whose orbits don't intersect our line of sight to their star. Anyone have references for further reading?
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So, by the transit method we're missing 99% of them.
(We miss fewer of them if they're orbiting in the habitable zone of cooler stars, since they're closer).
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Are you sure about that 1% number? How is it calculated? I would have thought that it depends on the angular diameter of the star as seen from the planet. For Earth, the Sun is about half a degree across. So I'm thinking the cone of visibility is 1/2 degree divided by 180 degrees (since the planet looking back at us could be anywhere in an arc of 180 degrees relative to the Earth's orbital plane), or 1 in 360--about a quarter of 1%. But maybe I have the math wrong.
(Surprisingly, I didn't run across a c
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But maybe I have the math wrong.
(Surprisingly, I didn't run across a clear discussion of this in a web search.)
You have the math nearly right.
As you say, it depends on the angular diameter of the sun as seen from the planet. Over the course of one orbit, the sun covers an area of the sky equal to that half a degree times 360 degrees. Call it 0.009 radians by 2 pi radians. The full sky is 4 pi sterradians. So, looks like the area covered by the disk of the sun, as a fraction of the full sky, is 0.0045, or 0.45%. (as you correctly note, looking the opposite direction, this also equals the fraction of the sky f
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Do some geometry to work out which range of angles from the star-obser
Is the signal to noise ratio good enough? (Score:3)
Is the signal to noise ratio of these radio signals good enough so that they can detected? If the signal power is below noise and it is not a spread spectrum signal it will be next to impossible for anyone to detect it.
The neighbors will probably file a complaint (Score:3)
Is this just a bad summary? (Score:2)
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No radio wave did not reach dozen of stars (Score:4, Interesting)
Theoretically yes, but.... (Score:2)
Just 5000 years? (Score:2)
Life on Earth has been around and messing with the atmosphere for billions of years, and therefore detectable to anyone looking in with sufficient technology. The "signal" created by the presence of a biosphere may be stronger than anything we could produce intentionally, and random spillover from radio and TV broadcasts is not even on the scale. As a techno-signature, the anthropogenic doubling of CO2 might be the loudest thing we've done.
Terrible summary by OP (Score:2)
This isn't about radio waves, it's about planets which (if they had life on them) would be able to see Earth's shadow crossing the sun.
However, even the article itself is wildly unrealistic. So far we have found no planet even remotely capable of multicellular life. To have that you need:
Bloody paywalled shite (Score:2)
The abstract [nature.com], reads.
"seen Earth transit in their lifetimes" (Score:2)
That is a strange sentence. Earth makes one transit across the Sun every year. How could any star not witness that, multiple times, in its lifetime? Unless the star had a lifetime of less than one year, which is impossible.