One of the well-known occasions within the historical past of astronomy is the Wow! Sign that was picked up by Ohio State College’s Massive Ear radio telescope in August 1977. The sign entered folklore as a result of it couldn’t be defined by any recognized pure phenomena and didn’t seem to have originated from Earth.
That left open a rare risk: that it had been produced by an extraterrestrial civilization. Certainly, Jerry Ehman, the astronomer who seen the sign within the knowledge, was so shocked by it that he wrote “Wow!” on the info print out, which is the way it bought its title.
Since then, varied astronomers have educated their telescopes on the identical a part of the sky within the constellation of Sagittarius in search of a repeat or some clue to its origin. However none of those research has discovered something uncommon; so the thriller has by no means been solved.
Enter Abel Mendez on the College of Puerto Rico and colleagues who assume they’ve solved the puzzle and say they know the place the Wow! sign got here from. If they’re right, the sign is completely pure but additionally an instance of a wholly new class of false positives which will crop up in different searches for extraterrestrial civilizations.
ET Alerts
The Massive Ear radio telescope was inbuilt 1963 and spent a lot of its life in search of indicators of extraterrestrial life (it was decommissioned in 1998). Astronomers have lengthy imagined {that a} good a part of the radio spectrum to look is round 1411 to 1419 MHz, near the 1420 MHz line produced when atoms of hydrogen transition from their first excited state to their floor state.
This area is comparatively quiet and so eminently appropriate for interstellar or intergalactic communication, which ought to look very totally different to the faint, wideband alerts produced by most pure phenomenon. That’s why a robust, narrowband sign in Massive Ear’s knowledge in 1977 instantly stood out.
Though no person has noticed an analogous sign from that area of the sky, Mendez and co reasoned that if it had a pure origin, comparable alerts might need been recorded in different areas by different telescopes with a lot larger sensitivity. So that they started a scientific search via knowledge gathered on the identical frequency and in an analogous method by the well-known Arecibo Telescope in Puerto Rico, till its demise in 2020.
And so they discovered one thing fascinating. “We report the detection of narrowband alerts close to the hydrogen line just like the Wow! Sign, though two-orders of magnitude much less intense and in a number of places,” say Mendez and co. “The one distinction between the alerts noticed in Arecibo and the Wow! Sign is their brightness.”
That is a crucial clue to their origin, say the staff. They are saying the alerts are simply identifiable as these produced by clouds of chilly hydrogen when stimulated by different energetic phenomena.
The Wow! Sign was a lot brighter, nonetheless. This might have been potential if the cloud of hydrogen was stimulated to the extent that it acted as a maser, the microwave equal of a laser based mostly on the stimulated emission of radiation from hydrogen atoms.
In principle, a maser — a tool that amplifies electromagnetic waves via stimulated emission — might generate alerts which are billions of occasions stronger than these from atypical hydrogen clouds and so might simply account for the depth of the Wow! Sign.
There are one or two uncertainties in all this. The primary is that astronomers have by no means seen a hydrogen maser in area, though physicists have made them on Earth. So if Mendez and co are right, the Wow! Sign could be the primary recorded statement of an astrophysical maser.
Magnetar Thriller
The second drawback is that masers want an vitality supply. Mendez and co recommend it will need to have been the sudden brightening of a magnetar or mushy gamma repeater behind the cloud. Neither of most of these objects had been found in 1977 and would in all probability have been too faint to select up with tools out there on the time.
That’s fascinating work that purports to resolve the Wow! Sign thriller for the primary time. “Our speculation accounts for all noticed traits of the Wow! Sign, introduces one other supply of false positives in technosignature searches, and means that this sign represented the primary recorded astronomical maser flare within the hydrogen line,” say Mendez and co.
The duty now’s to seek for extra proof to again up this principle. The precise place of the Wow! Sign within the sky just isn’t clear due to the broad spatial decision of the unique Massive Ear Telescope. However Mendez and co recommend that if a hydrogen fuel cloud was accountable, then this ought to be discoverable with at present’s extra superior tools. “Given the detectability of the clouds, as demonstrated in our knowledge, this perception might allow exact localization of the sign’s origin and allow steady monitoring for subsequent occasions,” they are saying.
Then there’s the maser that supplied the vitality. That too might be detectable, regardless that it should be extra distant.
The subsequent step is unquestionably to seek out this proof. Mendez and co are actually looking via extra archived knowledge from the Arecibo Telescope however there should be different doubtlessly revealing databases elsewhere. Let the search start!
Ref: Arecibo Wow! I: An Astrophysical Rationalization for the Wow! Sign : arxiv.org/abs/2408. 08513
