A Long Distance Call
Rather than using very high power transmitters, current research study by Stephen Kerby and Jason T. Wright shows that we might make usage of a natural signal gain boost developed into solar systems– the gravitational lensing of a solar systems star. Networking a series of stars as nodes might get signals throughout vast systems of the Milky Way. And we may be able to find if our Sun is already part of an alien galactic communication network.
Remote Satellites at the far reaches of the solar system might use the natural focusing of light by the Sun to interact across area– c. NASA
What is Gravitational Lensing– Video by Fraser Cain of Universe Today
A communication spacecraft with a more effective propulsion system might keep position and focus for a longer time. With the Sun as an example planetary system, a spacecraft utilizing our chemical rocket propulsion could preserve focus position for a few a century. Offered the light travel time between stars within our galaxy– dozens, hundreds, or even countless years– this isnt a substantial amount of time. With ion thrusters, likewise used by a few of our present day satellites and probes, you might maintain focus for nearly a millennia. What if you were an alien civilization with more sophisticated propulsion innovation?
Are We In The Loop?
We are already experimenting with combination based rockets that might support a craft for tens of thousands of years. Beyond our current technology, but hypothetically possible, is an antimatter propulsion system that could support a craft for millions of years. Exotic thrusters like antimatter may be more quickly detectable than other types of propulsion meaning if there is an interaction craft currently in our solar system put there by another civilization we may be able to see it.
What do I indicate by “currently?” The authors note its possible the Sun is currently a member of an interaction network– one node among numerous that is hosting an alien communication craft. How would not we already understand that? Well, if an alien spacecraft is utilizing our Suns gravitational lens, it will be challenging to spot as it would be numerous AU away– a future location of interest for artifact SETI research study (Search for Extraterrestrial Intelligence looking for alien artifacts). An unique propulsion system might offer it away. The signals focused by gravitational lensing are formed into a narrow cone that the Earth might not orbit through. If Earth doesnt pass through this cone of signal, a network of alien communication cloud pass right through our solar system undiscovered– an explanation to the tranquility of the galaxy if there are alien civilizations using gravitationaly lensed signals.
” If an ETI can conquer the engineering obstacles we examined, they might use gravitational lenses to send out transmissions throughout the galaxy in a huge network of interaction nodes. They might get rid of the big areas of area and interact more dependably. While we need to carry out observations to see if the Sun or another star is being used for this function, it likewise gives a plan for how humanity might interact across the galaxy in the remote future.”- Stephen Kerby, Lead Author
Presuming that gravitational lensing is being used for interstellar interaction, and that some galaxy may make better receiving/transmitting points than others, we might narrow radio SETI (Search for ETI using radio transmissions) searches to these ideal systems. A more complete study of neighbouring star systems would expose if they are much better network prospects– round stars with less wobble. We might then browse for outbound/inbound signals from a region opposite of their place in our own solar system where their light would be focused by our Sun toward a possible transmitting/receiving craft.
An entire constellation of interaction craft could be placed in orbit of the Sun. Each would preserve position for a brief time and then allow itself to fall out of place, orbit the Sun, and then return to place. If an alien civilization is using numerous craft in a system, then theres a much better possibility of finding a specific craft.
James Webb Space Telescope 6.5 m Primary Mirror. By contrast, the Hubble Space telescopes mirror is just 2.4 m c. NASA/JPL
Super Scopes
Simply as the Suns lensing result improves signal gain, so too would the result magnify remote star systems and other cosmic objects producing a giant super telescope. A gravitational scope would be far more effective than anything weve created capable of viewing expolanets with a similar clarity as we see the planets in our own solar system!
And if we ever do release a gravitational lens scope/transmitter, perhaps well discover another one already out there from someone else! Its amazing to think that possibly, MAYBE theres currently a highway of comms traffic passing through our system.
” The search for extraterrestrial intelligence is so multidisciplinary that researchers from all fields can contribute. Its a vision of unbiased and diverse expedition that should be a goal for the clinical community, and its extremely fulfilling for me to gain from astronomers from various scholastic and individual backgrounds. SETI also captures the publics creativity and assists everyone show about humankinds place in the universes.”- Stephen Kerby, Lead Author
Like a heavy ball put on a trampoline, a massive things such as a star will cause space itself to curve producing a “gravity well.” Both mass and energy travelling through curved area will follow that curve. Our orbit around the Sun is actually the Earth following the curve in area made by our stars mass. As light travels through space, its path likewise follows these curves triggering the light to bend. The effect resembles how light is bent by a glass lens which is why the flexing of light due to gravity is called “gravitational lensing”. Like a lens, stars can focus a far-off source of light, such as a radio signal, significantly improving signal gain or similarly focus an outbound signal for much better transmission. Gravitational lensing is likewise noticeable to our telescopes called “Einstein Rings” as it was Einsteins work on relativity which showed mass curves space.
Depiction of a gravity well– the warping of area created by an enormous things like a world. The Moon takes a trip through the Earths gravity well keeping it in orbit– c. NASA
An “Einstein Ring” created by Luminous Red Galaxy LRG 3-757– the centre red point in the image. The horseshoe shape surrounding the galaxy is a more far-off galaxy behind LRG 3-757 in the background. The inbound light of the more far-off background galaxy is being bent AROUND LRG 3-757 in the foreground due to gravitational lensing allowing us to see the more distant galaxy though it lags the foreground galaxy– c. NASA/HUBBLE
As our Suns gravity focuses light, a getting or transferring craft can be positioned along an axis that runs in between a distant target star where a signal may stem, the Sun, and a focal line where the Sun focuses that signal from the target star. The target star then is directly opposite the spacecraft on the other side of the Sun which the spacecraft sees not through but around the Sun as the Sun bends light around itself due to gravity. Envision it like an eyeball– the Sun is the lens of your eye with the spacecraft the back of your retina (but the light is walking around the glass of the “lens” instead of through it).
As signals are received, the craft could communicate information to the Earth or send out the signal to another transmitter/receiver stationed around the Sun aligned with a different remote target star to forward the signal onward. A connection to another galaxy would need another craft stationed at the remote target star. We have yet to develop a network like this, however possibly other civilizations have.
How the eye focuses light. Think of the far point is the far-off target star, the lens is the gravitational lensing result of the Sun, and the retina is where a getting communication spacecraft would be. c.Public Domain
Far Out
Utilizing relativity, a measurement of our Suns minimum focal distance out in space can be identified … 550AU about thirteen times the distance to Pluto. And 550AU just represents the minimum focal distance at which the light from a target curves around the Suns surface rather than being lost in the Sun itself. Some targets might be focused by the Sun even further out into space.
How much signal gain could be attained by the Suns gravitational lens? Price quotes in the research program that an incoming transmission focused by the Sun might increase gain by 120db (decibels). We can utilize the more efficient natural signal gain produced by the Suns gravity.
” Stars work like lenses, meaning that they supply a effective and natural way to improve signals across interstellar distances. An example might be hilltops and cell towers: sure you could build a cellular network without putting any towers on hilltops, however if the hills are there anyway, why wouldnt you use them?
Thrusters at Station Keeping
Using thrusters, a spacecraft sending or getting signals at the ideal focal place will require hold position relative to the Sun to within a hundred meters. At the severe focal distance, the Suns gravity is reasonably weak compared to where our solar systems worlds orbit. Loosing thrust would still cause the craft to fall into the solar system in an eccentric “comet like” orbit eventually plunging into the Sun itself in a few thousand years.
The 2nd significant cause of misalignment is the wobbling motion of the Sun. The orbit of a stars worlds, particularly huge gas giants like Jupiter, causes a star to wobble as its planets exert a gravitational pull. Our Suns wobble is the largest interruption of alignment between a remote target star, the Sun, and an interaction spacecraft. The craft could be fitted with an optical scope that would communicate position details to the crafts assistance computer system utilizing the relative position of other stars. The telescope could point towards to Sun to guarantee the target star from which a signal is being received is repaired in the Suns Einstein Ring. Just as the Einstein Ring photo of LRG 3-757 above programs how a remote background galaxy shines around a better foreground galaxy, a far-off target star from which the spacecraft is getting a transmission would appear as a ring of light surrounding the Sun from the crafts viewpoint.
The wobbling effect of a star due to the orbit of a world in the stars solar system c.NASA
Which stars would make perfect nodes in a hypothetical network? The authors recommend looking for round stars needing less focus modification and for that reason less fuel consumption by the spacecraft. Less round stars misshape signals. Even our Sun is not completely spherical. Stars with faster rates of rotation bulge toward their equator and are less ideal. More huge stars with more gravity put in more pull on the spacecraft. Stars with more worlds, or with gas giants in close orbits– hot Jupiters– have a more pronounced wobble requiring more thrust to maintain position. Stars with buddy stars, trinary or binary systems, will have a lot more pronounced wobbles.
Function Image: Fig1 from Kerby and Wright 2021 “A schematic of a on-axis outstanding relay transmission system, opening angles, distances, and sizes not to scale. The preliminary unfocused transmission beam may even have an annular pattern to avoid flux from being lost to the disk of the Sun.
More to Explore
[2109.08657] Stellar Gravitational Lens Engineering for Interstellar Communication and Artifact SETI (arxiv.org) (Originating Open Access Research Article by Kerby and Wright).
Stephen Kerby|Eberly College of Science (psu.edu).
Jason T Wright|AstroWright (psu.edu).
ESA– ESA invites Webb in French Guiana for launch on Ariane 5.
Plasma Thruster Could Dramatically Cut Down Flight Times to the Outer Solar System– Universe Today.
If We Used the Sun as a Gravitational Lens Telescope, This is What a Planet at Proxima Centauri Would Look Like– Universe Today.
What is Gravitational Lensing?– Universe Today.
The Ultimate Space Telescope Would Use the Sun as a Gravitational Lens|Daily Planet|Air & & Space Magazine (airspacemag.com).
solar gravitational lens TVIW-presentation (nasa.gov).
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As our Suns gravity focuses light, a sending or getting craft can be positioned along an axis that runs between a distant target star where a signal may originate, the Sun, and a focal line where the Sun focuses that signal from the target star. The target star then is directly opposite the spacecraft on the other side of the Sun which the spacecraft sees not through but around the Sun as the Sun flexes light around itself due to gravity. And 550AU just represents the minimum focal distance at which the light from a target curves around the Suns surface area rather than being lost in the Sun itself. Our Suns wobble is the largest interruption of positioning between a remote target star, the Sun, and a communication spacecraft. The telescope might point towards to Sun to guarantee the target star from which a signal is being gotten is fixed in the Suns Einstein Ring.