Free Republic
Browse · Search
General/Chat
Topics · Post Article

Skip to comments.

Toward a High-Velocity Astronomy
Centauri Dreams ^ | 5/15/19 | Paul Gilster

Posted on 05/15/2019 9:39:55 PM PDT by LibWhacker

Toward a High-Velocity Astronomy

by Paul Gilster
on May 15, 2019

Couple the beam from a 100 gigawatt laser with a single-layer lightsail and remarkable things can happen. As envisioned by scientists working with Breakthrough Starshot, a highly reflective sail made incredibly thin — perhaps formed out of graphene and no thicker than a single molecule — could attain speeds of 20 percent of c. That’s good enough to carry a gram-scale payload to the nearest stars, the Alpha Centauri triple system, with a cruise time of 20 years, for a flyby followed by an agonizingly slow but eventually complete data return.

A key element in the concept, as we saw yesterday, is the payload, which could take advantage of microminiaturization trends that, assuming they continue, could make a functional spacecraft smaller than a cell phone. The first iterations of such a ‘starchip’ are being tested. The Starshot work has likewise caught the attention of Bing Zhang, a professor of astrophysics at the University of Nevada, Las Vegas. Working with Kunyang Li (Georgia Institute of Technology) Zhang explores in a new paper the kind of astronomy that could be done by such a craft.

For getting to Proxima Centauri for the exploration of its interesting planet involves a journey that could itself provide a useful scientific return. The paper’s title, “Relativistic Astronomy,” flags its intent to study how movement at relativistic speeds would affect images taken by its camera. As Zhang explains in a recent essay on his work in The Conversation, when moving at 20 percent of lightspeed, an observer in the rest frame of the camera would experience the universe moving at an equivalent speed in the opposite direction to the camera’s motion.

Relativistic astronomy, then, explores these different spacetimes to observe objects we are familiar with from our Earth-based perspective as they are seen in the camera’s rest frame. Zhang and Li consider this “a new mode to study astronomy.” Zhang goes on to say:

…a relativistic camera would naturally serve as a spectrograph, allowing researchers to look at an intrinsically redder band of light. It would act as a lens, magnifying the amount of light it collects. And it would be a wide-field camera, letting astronomers observe more objects within the same field of view of the camera.

Image: Observed image of nearby galaxy M51 on the left. On the right, how the image would look through a camera moving at half the speed of light: brighter, bluer and with the stars in the galaxy closer together. Zhang & Li, 2018, The Astrophysical Journal, 854, 123, CC BY-ND.

Such observations become intriguing when we consider how light from the early universe is red-shifted as a result of the expansion of the cosmos. Zhang and Li point out that a camera moving at the relativistic speeds of the Proxima Centauri probe sees this redshifted light becoming bluer, counteracting the effect of the universe’s expansion. Light from the early universe that would have had to be studied at infrared wavelengths would now be susceptible to study in visible light. The camera, then, becomes a spectrograph allowing the observation of everything from remote galaxies to the cosmic microwave background.

Moreover, other relativistic effects come into play that add value to the fast camera. From the paper on this work:

…unique observations can be carried out thanks to several relativistic effects. In particular, due to Doppler blueshift and intensity boosting, one can use a camera sensitive to the optical band to study the near-IR bands. The light aberration effect also effectively increases the field of view of the camera since astronomical objects are packed in the direction of the camera motion, allowing a more efficient way of studying astronomical objects.

Let me depart for a moment from the Zhang and Li paper to pull information from a University of California at Riverside site, a page written by Alexis Brandeker, and presumably illustrated by him. In the figure below, we see only the effect of aberration at a range of velocities. Notice how the field becomes squeezed at we move from 0.5 c to 0.99 c. At 0.99 c, almost all visible radiation from the universe is confined to a region 10 degrees in radius around the direction of travel.

Image: This figure shows aberration effects for the ship travelling towards the constellation of Orion, assuming a 30 degrees field of view. The field of view is kept constant, only the speed is changed from 0 to 0.99c, showing dramatic effects on the perceived field. No radiative effects are considered, only geometrical aberration. Credit: Alexis Brandeker/UC-R.

But to get the overview, we have to fold in Doppler effects as infrared radiation is shifted into the visible. If we combine these effects in a single image, we get the startling view below.

Image: Both relativistic effects switched on. Credit: Alexis Brandeker/UC-R.

But back to Zhang and Li, whose camera aboard the probe is a spectrograph, a lens, and a wide-field camera all in one. The authors make the case that fast-moving cameras can likewise be used to probe the so-called ‘redshift desert’ (at 1.4 ≲ z ≲ 2.5) that coincides with the epoch of significant star formation (the name comes from the lack of strong spectral lines in the optical band here). Lacking data, we have no large sample of galaxies in a particular range of redshifts, which hinders our understanding of star formation.

Zhang and Li consider relativistic observations of gamma-ray bursts (GRBs) at extreme redshifts, as well as tracing the electromagnetic counterparts to gravitational wave events. Thus a Breakthrough Starshot payload enroute to Alpha Centauri offers a new kind of astronomy if we can master the construction of a camera that can withstand a journey through the interstellar medium without damage from dust as well as one that can transmit its data back to Earth.

What struck me as I began reading this paper is that when it comes to relativistic effects, 20 percent of lightspeed is actually on the slow side, making me wonder how much better the kind of observations the authors describe would be at higher velocities. But Zhang and Li move straight to this question, describing the relativistic effect of a Starshot probe as ‘mild,’ and noting that a Breakthrough laser infrastructure might be used for faster, dedicated astronomy missions.

If one drops the goal of reaching Alpha Centauri, cameras with even higher Doppler factors may be designed and launched. A Doppler factor of 2 and 3 (which gives a factor of 2 and 3 shift of the spectrum) is available at 60% and 80% speed of light, respectively. More interesting astronomical observations can be carried out at these speeds.

While probes in this range would demand ever more powerful acceleration from their laser energy source, they might actually be easier to build, for the need for cosmic ray shielding on a long cruise or data transmission at interstellar distances would be alleviated by sending them on missions closer to home. Of course, pushing probes to speeds much higher than 20 percent of c is even more problematic than the Centauri mission itself. Beyond Starshot, the authors argue that relativistic astronomy will repay the effort if we continue to push in the direction of beamed laser probes with an eye toward ever faster, more capable missions.

The paper is Zhang & Li, “Relativistic Astronomy,” Astrophysical Journal Vol. 854, No. 2 (20 February 2018). Abstract.



TOPICS: Astronomy; Science
KEYWORDS: alphacentauri; astronomy; graphene; high; laser; science; starshot; velocity; xplanets

1 posted on 05/15/2019 9:39:55 PM PDT by LibWhacker
[ Post Reply | Private Reply | View Replies]

To: LibWhacker

Bookmark


2 posted on 05/15/2019 9:54:14 PM PDT by DocRock (And now is the time to fight! Peter Muhlenberg)
[ Post Reply | Private Reply | To 1 | View Replies]

To: LibWhacker
Breakthrough Starshot, a highly reflective sail made incredibly thin — perhaps formed out of graphene and no thicker than a single molecule

It can't be graphene if it has to be reflective, graphene is transparent.

These probes are a neat idea, but for now staying home and building better telescopes can get us better information faster than travelling there. In the next hundred years we can build telescopes that will be able to resolve great detail on systems out to 300 light years or so. With them we can know what resources are available in those systems before we get there.

3 posted on 05/15/2019 9:58:51 PM PDT by Vince Ferrer
[ Post Reply | Private Reply | To 1 | View Replies]

To: LibWhacker

100 gigawatts GREAT SCOTT

4 posted on 05/15/2019 11:49:31 PM PDT by Pontiac (The welfare state must fail because it is contrary to human nature and diminishes the human spirit)
[ Post Reply | Private Reply | To 1 | View Replies]

To: LibWhacker
data transmission at interstellar distances would be alleviated by sending them on missions closer to home.

How is the Doppler shift going to effect the data transmission/reception?

5 posted on 05/16/2019 12:06:53 AM PDT by Pontiac (The welfare state must fail because it is contrary to human nature and diminishes the human spirit)
[ Post Reply | Private Reply | To 1 | View Replies]

To: Vince Ferrer

Do both. Telescope spacecraft like Hubble and here are 5 reasons why the coming James Webb Space Telescope is a big deal.

Nice video about 2:40 long.

https://www.mnn.com/earth-matters/space/stories/5-reasons-why-james-webb-space-telescope-rocks


6 posted on 05/16/2019 12:26:49 AM PDT by dragnet2 (Diversion and evasion are tools of deceit)
[ Post Reply | Private Reply | To 3 | View Replies]

To: KevinDavis; annie laurie; Knitting A Conundrum; Viking2002; Ernest_at_the_Beach; Mmogamer; ...
Couple the beam from a 100 gigawatt laser with a single-layer... highly reflective sail... perhaps formed out of graphene... could attain speeds of 20 percent of c. That's good enough to carry a gram-scale payload to the nearest stars, the Alpha Centauri triple system, with a cruise time of 20 years, for a flyby followed by an agonizingly slow but eventually complete data return... the payload, which could take advantage of microminiaturization trends that, assuming they continue, could make a functional spacecraft smaller than a cell phone.
Thanks LibWhacker.
 
X-Planets
· join · view topics · view or post blog · bookmark · post new topic · subscribe ·
Google news searches: exoplanet · exosolar · extrasolar ·

7 posted on 05/16/2019 12:46:02 AM PDT by SunkenCiv (Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
[ Post Reply | Private Reply | View Replies]

To: LibWhacker

l8r


8 posted on 05/16/2019 3:00:34 AM PDT by preacher ( Journalism no longer reports news, they use news to shape our society.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: LibWhacker

Wasn’t the Motie spaceship in Niven and Pournelle’s The Mote in God’s Eye a laser-driven lightsail? And the mote was the laser seen from the destination end.


9 posted on 05/16/2019 3:53:57 AM PDT by FreedomPoster (Islam delenda est)
[ Post Reply | Private Reply | To 1 | View Replies]

To: LibWhacker
A key element in the concept, as we saw yesterday, is the payload, which could take advantage of microminiaturization trends that, assuming they continue...

Neglecting the sophon-barrier to further technological advancement (/somewhat obscure sci-fi reference)

10 posted on 05/16/2019 4:15:54 AM PDT by Tallguy (Facts be d*mned! The narrative of the day must be preserved!)
[ Post Reply | Private Reply | To 1 | View Replies]

To: LibWhacker

so the solar winds always blow in the same direction?


11 posted on 05/16/2019 5:28:53 AM PDT by PeterPrinciple (Thinking Caps are no longer being issued but there must be a warehouse full of them somewhere.)
[ Post Reply | Private Reply | To 1 | View Replies]

To: SunkenCiv

The speed of light is not fast enough.

Even integer multiples of the speed of light are not fast enough.

Even if you had a ship that could do 10 times the speed of light, getting to a star 40 light years away, a relatively short, ‘neighborhood’ distance in galactic terms, it would still take 4 years to traverse the distance and 4 to get back home.

Unless and until man invents some ‘Star Trek’ type of propulsion system that will allow us to travel the stars in comfort and luxury, then we, as a species are essentially locked within our own solar system.

And so is everyone else in the universe...................


12 posted on 05/16/2019 6:20:53 AM PDT by Red Badger (We are headed for a Civil War. It won't be nice like the last one....................)
[ Post Reply | Private Reply | To 7 | View Replies]

To: Red Badger
The article isn't about sending humans to Alpha Centauri, it's about sending a probe there. Besides being the nearest star cluster, Alpha's very similar to our own Sun, oh, and I think that's where Spock's ancestors live ;^); Proxima is a red dwarf and the closest of the bunch.

13 posted on 05/16/2019 10:13:21 AM PDT by SunkenCiv (Imagine an imaginary menagerie manager imagining managing an imaginary menagerie.)
[ Post Reply | Private Reply | To 12 | View Replies]

To: SunkenCiv; Red Badger

And that’s a great point, it’s too slow for interstellar travel outside our solar system. And this will likely be the case for human for a long time due to the lack of technology available for humans to exceed light speed. Unmanned spacecraft of all types are here for the long term as they have already provided us with enough data to study/analyze for decades to come, far beyond what our primitive manned spacecraft are capable of at this point.


14 posted on 05/16/2019 10:38:47 AM PDT by dragnet2 (Diversion and evasion are tools of deceit)
[ Post Reply | Private Reply | To 13 | View Replies]

To: LibWhacker
So... this camera will take 10 pounds off me? 😀

-PJ

15 posted on 05/16/2019 10:47:33 AM PDT by Political Junkie Too (The 1st Amendment gives the People the right to a free press, not CNN the right to the 1st question.)
[ Post Reply | Private Reply | To 1 | View Replies]

Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.

Free Republic
Browse · Search
General/Chat
Topics · Post Article

FreeRepublic, LLC, PO BOX 9771, FRESNO, CA 93794
FreeRepublic.com is powered by software copyright 2000-2008 John Robinson