ESO's Very Large Telescope has combined the light from all four of its Unit Telescopes into its ESPRESSO instrument for the first time, effectively creating a 16 meter aperture optical telescope:
The ESPRESSO instrument on ESO's Very Large Telescope in Chile has for the first time been used to combine light from all four of the 8.2-metre Unit Telescopes. Combining light from the Unit Telescopes in this way makes the VLT the largest optical telescope in existence in terms of collecting area.
One of the original design goals of ESO's Very Large Telescope (VLT) was for its four Unit Telescopes (UTs) to work together to create a single giant telescope. With the first light of the ESPRESSO spectrograph using the four-Unit-Telescope mode of the VLT, this milestone has now been reached.
After extensive preparations by the ESPRESSO consortium (led by the Astronomical Observatory of the University of Geneva, with the participation of research centres from Italy, Portugal, Spain and Switzerland) and ESO staff, ESO's Director General Xavier Barcons initiated this historic astronomical observation with the push of a button in the control room.
[...] Light from the four Unit Telescopes is routinely brought together in the VLT Interferometer for the study of extremely fine detail in comparatively bright objects. But interferometry, which combines the beams "coherently", cannot exploit the huge light-gathering potential of the combined telescopes to study faint objects.
Previously: First Light for VLT's ESPRESSO Exoplanet Hunter
Related Stories
The Echelle SPectrograph for Rocky Exoplanet- and Stable Spectroscopic Observations (ESPRESSO) has begun operations at the Very Large Telescope in Chile:
A new exoplanet-hunting instrument, attached to one of the world's largest telescopes, has seen its first glimpse of the sky, the European Southern Observatory (ESO) announced today. The Echelle Spectrograph for Rocky Exoplanet and Stable Spectroscopic Observations (ESPRESSO) detects exoplanets by measuring shifts in the spectrum of light from stars caused by the gravity of planets tugging on them. For this technique, the signal of the stellar wobble is bigger for more massive planets in closer orbits. ESPRESSO, with improved spectral resolution, a wider wavelength range, and fixed to ESO's Very Large Telescope (VLT) at Cerro Paranal in Chile, hopes to discern the fainter tugs of planets with Earth-like masses and orbits.
"It's the most mature facility in the world of this kind," says astronomer Didier Queloz of Cambridge University in the United Kingdom, co-discoverer of the first exoplanet around a normal star in 1995. [...] The previous generation of spectrographs could reach stellar wobbles of around 1 meter per second—a slow walking pace. Jupiter, for example, shifts the sun by 13 meters per second, but Earth's much weaker tug only achieves a velocity of 9 centimeters per second. ESPRESSO, at the forefront of the new generation, aims to put Earth-like planets within reach, with a sensitivity of 10 centimeters per second or even slower. "We're the first to be mad enough to try to achieve that," says lead scientist Francesco Pepe of the University of Geneva in Switzerland.
An exact twin of Earth is probably out of reach, but ESPRESSO should be able to detect super-Earths three or four times heavier than Earth that orbit sun-like stars. It may also detect Earth-sized planets around smaller stars, where a weaker tug achieves more movement.
ESPRESSO is roughly three times more sensitive than HARPS. The CODEX spectrograph attached to the Extremely Large Telescope (ELT) should be about five times more sensitive than ESPRESSO. The ELT's first light is scheduled for 2024.
Also at Space.com.
Telescope array will spy on spy satellites, star surfaces and black holes
At a time when astronomers are building billion-dollar telescopes with mirrors 30 meters across, the 1.4-meter instrument being installed this month atop South Baldy Mountain in New Mexico may seem like a bit player. But over the next few years, nine more identical telescopes will join it on the grassy, 3200-meter summit, forming a Y-shaped array that will surpass any other optical telescope in its eye for detail. When it's complete around 2025, the $200 million Magdalena Ridge Observatory Interferometer (MROI) will have the equivalent resolution of a gigantic telescope 347 meters across.
MROI's small telescopes can't match the light-gathering power of its giant cousins, so it will be limited to bright targets. But by combining light from the spread-out telescopes, it is expected to make out small structures on stellar surfaces, image dust around newborn stars, and peer at supermassive black holes at the center of some galaxies. It will even be able to make out details as small as a centimeter across on satellites in geosynchronous orbit, 36,000 kilometers above Earth, enabling it to spy on spy satellites.
That's one reason why the U.S. Air Force, which wants to monitor its own orbital assets and presumably those of others, is funding MROI. "They want to know: Did the boom break or did some part of the photovoltaic panels collapse?" says Michelle Creech-Eakman, an astronomer at the New Mexico Institute of Mining and Technology in Socorro and project scientist on MROI. But if the facility succeeds, its biggest impact could be on the field of astronomy, by drawing new attention to the promise of optical interferometry, a powerful but challenging strategy for extracting exquisitely sharp images from relatively small, cheap telescopes.
Wikipedia article on Astronomical Optical Interferometry.
Related: Very Large Telescope's MUSE Instrument Studies the Hubble Ultra-Deep Field
Very Large Telescope's ESPRESSO Combines Light From All Four Unit Telescopes for the First Time
Very Large Telescope Captures First Direct Image of a Planet Being Formed
Submitted via IRC for Fnord666
If Lowell Observatory's Gerard van Belle gets his way, you'll soon be watching an exoplanet cross the face of its star, hundreds of light-years from the Earth. He can't show you that right now, but he should be able to when the new mirrors are installed at the Navy Precision Optical Interferometer in northern Arizona. They're arriving now and should soon start collecting starlight—and making it the highest-resolution optical telescope in the world.
Van Belle recently showed Ars around the gigantic instrument, which bears almost no resemblance to what a non-astronomer pictures when they hear the word "telescope." There are a couple of more traditional telescopes in dome-topped silos on site, including one built in 1920s in Ohio, where it spent the first few decades of its life.
The best way to improve imagery on these traditional scopes is to increase the diameter of the mirror catching light. But this has its limits—perfect mirrors can only be built so large.
[...] A bigger mirror provides two advantages: it catches more light (making fainter objects visible) and it produces a higher-resolution image. If you give up on the first advantage, you can go all in on the second by laying out a handful of small mirrors over a considerable distance. The total mirror area (and therefore light collection) won't be that great, but the tremendous diameter of the array cranks the resolution up to 11. That's the principle behind the Navy Precision Optical Interferometer, a Y-shaped installation with a functional diameter of up to 430 meters.
Source: https://arstechnica.com/science/2018/07/meet-the-telescope-that-may-soon-show-you-an-exo-eclipse/
Related: Very Large Telescope Interferometer Captures Best Ever Image of Another Star (Antares)
Very Large Telescope's MUSE Instrument Studies the Hubble Ultra-Deep Field
Very Large Telescope's ESPRESSO Combines Light From All Four Unit Telescopes for the First Time
High-Resolution View Into The Infrared Universe
Very Large Telescope Captures First Direct Image of a Planet Being Formed
Magdalena Ridge Observatory Interferometer Will Have Resolution of a 347-Meter Telescope for $200m
The Swarm Telescope Concept
Proxima Centauri b confirmed as nearest exoworld
Four years ago, scientists made one of the most exciting exoplanet discoveries so far, a rocky planet similar in size to Earth orbiting the nearest star to the sun, Proxima Centauri. While the detection seemed solid, more confirmation is always good, and now the ESPRESSO spectrograph on the Very Large Telescope (VLT) in Chile has provided that extra and more detailed confirmation. The news was announced by the University of Geneva (UNIGE) on May 28, 2020.
[...] Proxima Centauri b is very similar in size to Earth, with a mass of 1.17 Earth masses. It orbits its star in only 11.2 days, in contrast to our Earth's year-long orbit around our sun. That means Proxima Centauri b is a lot closer to its star than Earth is to the sun. But, because the star is a red dwarf – much smaller and cooler than our sun – its orbit is indeed within the habitable zone of Proxima Centauri. Interestingly, Proxima Centauri b receives about the same amount of solar energy from its star that Earth does from our sun.
[...] The mass of Proxima b was previously estimated to be 1.3 Earth masses. The accuracy of the new measurement of 1.17 Earth masses is unprecedented, according to Michel Mayor, the "architect" of all ESPRESSO-type instruments:
ESPRESSO has made it possible to measure the mass of the planet with a precision of over one-tenth of the mass of Earth. It's completely unheard of.
The new confirmation of Proxima Centauri b is exciting, but there may be more surprises in store ... there is also possible evidence of another and smaller planet in the newest data. A secondary detection was also made, although it isn't certain whether it is actually a planet. If it is, it is even smaller than Proxima Centauri b. [...] If it is a planet, it would be more akin to Mars or Mercury in size and mass – estimated at a minimum Earth mass of 0.29 ± 0.08 – and orbits the star in only 5.15 days. It wouldn't be too surprising, though, in that low-mass stars like red dwarfs tend to have multiple planets in their systems. More observations will be required to either confirm or refute this possible second planet.
Journal Reference
Mascareño, A. Suárez, Faria, J. P., Figueira, P., et al. Revisiting Proxima with ESPRESSO, (https://arxiv.org/abs/2005.12114v1)
Proxima Centauri - Planetary system
Previously: ESO Confirms Reports of Proxima Centauri Exoplanet
Proxima b May Have Oceans
Dust Belts and Possible Additional Exoplanet Spotted Around Proxima Centauri
First Light for VLT's ESPRESSO Exoplanet Hunter
Very Large Telescope's ESPRESSO Combines Light From All Four Unit Telescopes for the First Time
Proxima Centauri's No Good, Very Bad Day
High Levels of Ultraviolet Radiation Should Not Preclude Life on Exoplanets
Icy second planet potentially spotted orbiting Proxima Centauri
(Score: 1, Redundant) by aristarchus on Wednesday February 14 2018, @08:41AM
And? We are supposed to trust Astronomers all hopped up on caffeine? What did they see? And how well did they see it?
And can it be replicated in a 203mm Newtonian? (Asking for a friend)
(Score: 3, Interesting) by JoeMerchant on Wednesday February 14 2018, @02:11PM (7 children)
If this technology could be applied to a swarm of small space-based telescopes, that could have very exciting possibilities. Each individual scope could be compact, cheap to build and launch, but acting in concert they could form a huge optical collector. A continuously funded program could launch a number of scopes per year, growing the collector until the size of the swarm is so large that the new scopes are just replacing failed units.
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(Score: 2) by HiThere on Wednesday February 14 2018, @06:26PM (6 children)
Synchronizing the distance between the telescopes to in integral number of wavelengths (or figuring a correction factor) when they aren't attached to a stable platform is a bit questionable, though. Radio telescopes have done the equivalent for a long time, and part of the reason they could and optical telescopes couldn't is that the wavelengths they were dealing with were enough longer to make it practical That they can do it with light at all is rather amazing. I'd be really surprised if they could do it cheaply with telescopes not attached to a fixed relative position.
OTOH, calculating the current atmospheric distortion isn't something I would have believed possible either, but these days all the big telescopes to it. So maybe. But it's a lot more difficult that you seem to be thinking. I still think two 5-mile mirror telescopes in Neptune's orbit would be better, and probably easier. The orbital diameter would be enough that you could use parallax to measure the distance to a lot of stars that we believe we know the distances to, but where the chains of reasoning have lots of "almost certainly"s in them.
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(Score: 0) by Anonymous Coward on Wednesday February 14 2018, @07:10PM
The great advantage that radio astronomers have is that they can do all of their image formation well after the fact. Their wavelengths are so long that they can digitize the radio waves as they arrive and time-tag them with an atomic clock (each antenna has its own clock and digitizer). Because of the time-tag, you can easily combine the signals from other telescopes because their data are time-tagged as well. You can sample many many points of the radio wave, and the errors from the time-tagging and digitization are well below what is needed to phase them all up later in software. In the optical regime you just can't digitize the waveform fast enough, nor time-tag it, so you have to do it all on the fly and only record the phased up image. The big segmented mirror telescopes have to do that for each segment.
As you mention, you're screwed when it comes to free-flying telescopes (or telescopes on floppy booms, for that matter). Positioning something to a gnat's ass is hard enough, but to position and control it to a gnat's ass, you have to sample and know it's position to a gnat's ass of a gnat's ass, and that ain't easy when you're talking nanometers on top of things that are vibrating at a kilohertz and higher.
(Score: 0) by Anonymous Coward on Wednesday February 14 2018, @08:09PM (1 child)
I just read the press release. They are not interferometrically combining the light from the four telescopes, just incoherently. That means they've quadrupled their photon collecting capability, but they haven't increased their angular resolution. You wouldn't want to run a swarm of small telescopes this way (except maybe for some very specific purposes) because you'd only have the angular resolution of the small telescopes.
For instance, take the 2.4 m diameter Hubble primary. That's the same collection area as 2200 50-mm apertures, but why would you want to fly 2200 cubesats that gives you the image resolution that you'd get with a 50-mm telescope? Now, if you could combine those 2200 apertures interferometrically, and fly them in a swarm that had a diameter of 24 meters (or 240 meters), that would be very interesting.
(Score: 2) by bob_super on Wednesday February 14 2018, @08:30PM
As fine controls improve, the swarm of mirror-sats reflecting light onto a sensor-and-analyzer center sat starts to make a lot more sense than the massively costly and risky business of the Webb.
Serviceability and upgrades would be a lot better too: just switch the sat at the focal point for an upgraded one every decade, without having to relaunch the mirror array (or vice versa).
(Score: 2) by bob_super on Wednesday February 14 2018, @08:14PM (1 child)
> Synchronizing the distance between the telescopes to in integral number of wavelengths (or figuring
> a correction factor) when they aren't attached to a stable platform is a bit questionable
It's absolutely amazing the precision that can be achieved:
https://arstechnica.com/science/2018/02/lisa-pathfinder-mission-a-glorious-success/ [arstechnica.com]
Now, that's with a much smaler mass than a telescope would be, but swarms of satellites keeping very precise tabs on each other to run observations are not a new topic.
(Score: 2) by HiThere on Thursday February 15 2018, @06:24AM
Well, my first thought was "I think that's only two independent pieces" and my second was "that sure wasn't any cubesat"...
But it *is* an sort of existence proof that the thing should be doable. I don't, however, think it would be doable with cubesats...at least not any way that they're normally launched. IIRC the LISA pieces needed to be in stable relation to each other to make that work (though I'm not sure quite what that means when things are in independent orbit...possibly it had to do with calculating a correction factor).
But the proposal was for lots of independent launches of the cubesats, which would make positioning them a real challenge, unless it's all done by calculating correction factors. But for that to work relative motion would need to be essentially nil (or at least calculable by a simple function) and accurate to a fraction of a wavelenght. Now the light collecting power of a telescope depends on the area of the mirror, but the resolution depends on the diameter. So for a decent telescope you'd need hundreds of cubesats whose position relative to each of the others was calculated to, I think, 1/8 of the shortest wavelength you want to observe, and for the advantage you'd want them spread in a plane over as wide an area as possible. (You'd need to talk to a telescope builder to get that figure accurate. but it's in the same range as the Lisa positioning.) This hasn't been done on the ground until recently, because accurate positioning was too difficult. I think I read when they started doing it with mirrors on tracks at one of the large telescopes a couple of decades ago...and ran into problems with getting position accurate enough. With radio telescopes they do it from one side of the earth to the other, but those wavelengths are between meters and kilometers, so positioning is a lot easier. (OTOH, since each cubesat would have it's own focal point, I think the plane over which they are spread can be flat rather than the surface of a parabola. Or if you're going to use fancy calculations to form your image, perhaps it could be spread in a 3-d cloud of known positions, and then you could look in any direction just by rotating the cubesats independently...which would mean they'd need to handle their gyroscopes with exceedingly fine precision.)
So, while it's got lots of possibilities as a design, I think it's well beyond the state of the art. (That said, I'm a programmer, not a satellite designer, and even then I'm essentially retired, so perhaps it isn't as far beyond the state of the art as I think.)
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(Score: 2) by JoeMerchant on Wednesday February 14 2018, @08:47PM
The small-satellite telescopes could be free floating, that seems to be... ambitious, unless you're willing to accept resolution at a fraction of the digital sensor and use stellar navigation to correct for pointing errors.
What seems more practical to me would be for the swarm to dock to itself - changing pointing direction could be a challenge, but if the docking mechanism is robust enough, it should be able to handle hundreds, if not thousands of separate mirrors and sensors.
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