Eksperimentelle kosmologer bruger fotonik til at søge Andromeda efter tegn på fremmed liv

"Er vi alene i universet?" Spørgsmålet har fascineret, pirrede og endda forvirrede mennesker, så længe vi kan huske.

Indtil nu, det ser ud til, at intelligent udenjordisk liv - i det mindste som passer til vores snævre definition af det - ingen steder er at finde. Teorier og antagelser florerer om, hvorfor vi hverken har taget kontakt med eller set beviser for avancerede udenjordiske civilisationer på trods af årtiers lange bestræbelser på at gøre vores tilstedeværelse kendt og for at kommunikere med dem.

I mellemtiden en konstant strøm af opdagelser demonstrerer tilstedeværelsen af ​​jordanaloger - planeter, der som vores egen, eksisterer i en "Goldilocks zone" afstand fra deres egne respektive stjerner, hvor forholdene er "lige rigtige" for at flydende vand (og dermed liv) kan eksistere. Måske endnu mere overvældende er tanken om, at der er, gennemsnitlig, lige så mange planeter, som der er stjerner.

"Det er, Jeg tror, en af ​​de fantastiske opdagelser i det sidste århundrede eller deromkring - at planeter er almindelige, " sagde Philip Lubin, en eksperimentel kosmolog og professor i fysik ved UC Santa Barbara. I betragtning af det, og antagelsen om, at planeter giver betingelserne for liv, spørgsmålet til Lubins gruppe er blevet:Leder vi hårdt nok efter disse rumvæsner?

Det er driveren bag Trillion Planet Survey, et projekt af Lubins studerende forskere. Det ambitiøse eksperiment, drevet næsten udelukkende af studerende, bruger en række teleskoper nær og fjern rettet mod den nærliggende galakse Andromeda såvel som andre galakser inklusive vores egen, en "pipeline" af software til at behandle billeder og en lille smule spilteori.

"Først og fremmest, vi antager, at der er en civilisation derude af lignende eller højere klasse end vores, der forsøger at udsende deres tilstedeværelse ved hjælp af en optisk stråle, måske af den "dirigerede energi"-array-type, der i øjeblikket udvikles her på Jorden, " sagde ledende forsker Andrew Stewart, som er studerende ved Emory University og medlem af Lubins gruppe. "Sekund, vi antager, at transmissionsbølgelængden af ​​denne stråle er en, vi kan detektere. Til sidst, vi antager, at dette fyr har været tændt længe nok til, at lyset kan registreres af os. Hvis disse krav er opfyldt, og den udenjordiske intelligenss strålekraft og diameter er i overensstemmelse med en jordisk civilisationsklasse, vores system vil registrere dette signal."

Fra radiobølger til lette bølger

I det sidste halve århundrede, den dominerende udsendelse fra Jorden har taget form af radio, TV- og radarsignaler, og søgende efter fremmed liv, såsom forskerne ved Search for Extraterrestrial Intelligence (SETI) Institute, har brugt kraftige radioteleskoper til at lede efter disse signaler fra andre civilisationer. For nylig dog og takket være den eksponentielt accelererende fremskridt inden for fotonisk teknologi, optiske og infrarøde bølgelængder giver muligheder for at søge via optiske signaler, der giver mulighed for langt længere rækkevidde detektion for sammenlignelige systemer.

I et papir udgivet i 2016 kaldet "The Search for Directed Intelligence" eller SDI, Lubin skitserede den grundlæggende detektion og spilteori om et "blind-blind" system, hvor hverken vi, heller ikke den udenjordiske civilisation er opmærksomme på hinanden, men ønsker at finde hinanden. Dette papir var baseret på anvendelsen af ​​fotonik udviklet ved UC Santa Barbara i Lubins gruppe til fremdrift af små rumfartøjer gennem rummet med relativistiske hastigheder (dvs. en betydelig brøkdel af lysets hastighed) for at muliggøre de første interstellare missioner. Det igangværende projekt er finansieret af NASAs Starlight og milliardæren Yuri Milners Breakthrough Starshot-programmer, som begge bruger teknologien udviklet på UCSB. Papiret fra 2016 viser, at den teknologi, vi udvikler i dag, ville være det klareste lys i universet og dermed i stand til at blive set på tværs af hele universet.

Selvfølgelig, ikke alle er trygge ved at reklamere for vores tilstedeværelse til andre, potentielt avanceret, udenjordiske civilisationer.

"Vi udsender vores tilstedeværelse til universet, tro det eller ej, turns out to be a very controversial topic, " Stewart said, citing bureaucratic issues that arise whenever beaconing is discussed, as well as the difficulty in obtaining the necessary technology of the scale required. Følgelig, only a few, tentative signals have ever been sent in a directed fashion, including the famous Voyager 1 probe with its message-in-a-bottle-like golden record.

Tipping the concept on its head, the researchers asked, 'What if there are other civilizations out there that are less shy about broadcasting their presence?'

"I øjeblikket, we're assuming that they're not using gravity waves or neutrinos or something that's very difficult for us to detect, " Lubin said. But optical signals could be detected by small (meter class) diameter telescopes such as those at the Las Cumbres Observatory's robotically controlled global network.

"In no way are we suggesting that radio SETI should be abandoned in favor of optical SETI, " Stewart added. "We just think the optical bands should be explored as well."

Searching the Stars

"We're in the process of surveying (Andromeda) right now and getting what's called 'the pipeline' up and running, " said researcher Alex Polanski, a UC Santa Barbara undergraduate in Lubin's group. A set of photos taken by the telescopes, each of which takes a 1/30th slice of Andromeda, will be knit together to create a single image, forklarede han. That one photograph will then be compared to a more pristine image in which there are no known transient signals—interfering signals from, sige, satellites or spacecraft—in addition to the optical signals emanating from the stellar systems themselves. The survey photo would be expected to have the same signal values as the pristine "control" photo, leading to a difference of zero. But a difference greater than zero could indicate a transient signal source, Polanski explained. Those transient signals would then be further processed in the software pipeline developed by Stewart to kick out false positives. In the future the team plans to use simultaneous multiple color imaging to will help remove false positives as well.

"One of the things the software checks for is, sige, a satellite that did go through our image, " said Kyle Friedman, a senior from Granada Hills High School in Los Angeles, who is conducting research in Lubin's group. "It wouldn't be small; it would be pretty big, and if that were to happen the software would immediately recognize it and throw out that image before we actually even process it."

Other vagaries, ifølge forskerne, include sky conditions, which is why it's important to have several telescopes monitoring Andromeda during their data run.

Thanks to the efforts of Santa Barbara-based computer engineer Kelley Winters and the guidance of Lubin group project scientist Jatila van der Veen, the data is in good hands. Winters' cloud-based Linux server provides a flexible, highly connected platform for the data pipeline software to perform its image analysis, while van der Veen will apply her digital image processing expertise to bring this project to future experimental cosmologists.

For Laguna Blanca School senior and future physicist Caitlin Gainey, who joins the UCSB physics freshman class this year, the project is a unique opportunity.

"In the Trillion Planet Survey especially, we experience something very inspiring:We have the opportunity to look out of our earthly bubble at entire galaxies, which could potentially have other beings looking right back at us, " she said. "The mere possibility of extraterrestrial intelligence is something very new and incredibly intriguing, so I'm excited to really delve into the search this coming year."

The search, for any SETI-watcher, is an exercise in patience and optimism. Andromeda is 2.5 million light-years away, van der Veen pointed out, so any signal detected now would have been sent at least 2.5 million years ago—more than long enough for the civilization that sent it to have died out by the time the light reaches us.

"That does not mean we should not look, " van der Veen said. "After all, we look for archaeological relics and fossils, which tell us about the history of Earth. Finding ancient signals will definitely give us information about the history of evolution of life in the cosmos, and that would be amazing."

While the data run and processing time for this particular project could occur in a span of weeks, according to the researchers this sequence could be repeated indefinitely. Teoretisk set, like all the sunrise and sunset watchers, and stargazers before us, we could look at the sky forever.

"I think if you were to take someone outside and you were to point at some random star in the night sky and see that is where life is, I think you would be hard pressed to find anyone who would not look at that star and just feel something very deep within themselves, " Polanski said. "Some very deep connection to whatever is up there or some kind of solace, Jeg tror, knowing that we're not alone."

The latest UCSB data and game theory of the "blind-blind" detection strategy used is being presented at the NASA Technosignatures workshop in Houston on September 28.