NASA's next dream telescopes

13 December 2018

NASA is planning four of the largest space telescopes ever. Each would target different wavelengths and goals. Astronomers are now picking a favorite as a part of the decadal survey in astrophysics, so that it might launch sometime in the 2030s. Scroll down to learn more about these telescopes.

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Lynx X-ray Observatory

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Lynx detects X-ray

Primary mirror size: 3 meters

Instruments: Three

Orbit location: Sun-Earth L2

Launcher: Unspecified heavy launcher

Launch mass: 7.9 metric tons

Primary science targets: First supermassive black holes

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X-rays, so useful for doctors, are a pain for astronomers to gather. Earth’s atmosphere blocks them, so astronomers must get to space to see the million-degree gases that shine in x-rays. Even in space the energetic photons are elusive, penetrating conventional mirrors instead of reflecting. Only a few thousand x-ray sources are known, but Lynx would find thousands more by going deeper and fainter. It would use hundreds of thin silicon mirrors arranged in nested shells to focus x-rays in glancing reflections.

One target will be supermassive black holes in the early universe, puzzling because they could not have grown so big, so fast by gobbling up star-size black holes. Seeing the gas being sucked into them may yield clues to the puzzle. Lynx also would capture stellar winds, supernovae, and the energetic jets that expel hot gases from galaxies, quenching their star formation.

At a glance

X-rays penetrate conventional mirrors and so must be deflected at grazing angles. Lynx will use hundreds of concentric silicon mirrors, just 1 millimeter thick, to focus photons on detectors 10 meters away.

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Between the lines

Gratings that swing into the light path from behind the mirror can tease apart spectral absorption lines from gas clouds in galactic halos and in the cosmic web.

Counting photons

Lynx’s microcalorimeter takes both high- definition images and spectra. It logs every photon’s location and energy by recording temperature rises in an array of silicon sensors.

Habitable Exoplanet Observatory

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HabEx detects ultraviolet, visible and infrared light

Primary mirror size: 4 meters

Instruments: Three

Orbit location: Sun-Earth L2

Launcher: Space Launch System block 1B

Launch mass: 35 metric tons

Primary science targets: Earth-like exoplanets

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HabEx would look for signs of life light-years away. Although thousands of exoplanets have been discovered indirectly, only a few large ones have been seen directly, amid the glare of their star. Current telescopes cannot capture the faint light of small rocky worlds like our own, let alone tease it apart for biosignatures such as oxygen and methane.

HabEx’s 4-meter mirror would work in concert with a starshade, a flower-shaped mask 72 meters across that would float 124,000 kilometers away and block the light of a star so that HabEx can see planets around it. HabEx will also have an internal coronagraph, which also blocks starlight, but less effectively than the starshade.

No starshade has ever flown, but, proponents say, HabEx is still the surest way to answer the question: Are we alone?

Formation flying

The starshade must fly far from HabEx to block the glare of a distant star so that orbiting planets—one ten-billionth as bright—can be seen.

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Starshade petal

The petal shape softens the edge of the starshade, reducing the amount of scattered starlight.

Unobstructed view

The off-axis design avoids the need for secondary mirror support struts that could scatter light and swamp precious exoplanet photons.

The ultimate shades

A coronagraph does the job of a starshade, but internally. Deformable mirrors smooth incoming light. A mask less than a millimeter across removes the star’s glare, while a Lyot stop catches stray light.

The Origins Space Telescope

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Origins detects infrared light

Primary mirror size: 5.9 meters

Instruments: Five

Orbit location: Sun-Earth L2

Launcher: Space Launch System block 2

Launch mass: 30 metric tons

Primary science targets: Gas clouds and planet-forming disks

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Origins will stare at the cold universe: galactic gas clouds, planet-forming disks, and other objects that glow feebly in the far infrared. That means the telescope itself must be frigid to stanch its own infrared light. Few instruments have studied the far infrared, which is largely blocked by Earth’s atmosphere. Origins will be much more sensitive and long lived than its predecessors, with solar-powered mechanical cryocoolers to chill the entire 5.9-meter telescope to 4° above absolute zero. Its five instruments will go colder still, to a fraction of a degree.

Origins could follow gas clouds collapsing into stars and dust disks spawning planets. And by monitoring water’s spectral lines, Origins could track it from interstellar clouds to protoplanetary disks and on to habitable worlds.

Stay cool

Origins must be chilled to reduce its own infrared glow. Sunshields drop temperatures to 35 K. Solar-powered, mechanical cryocoolers take the telescope to 4 K without the need to rely on a limited supply of liquid helium.

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Approaching absolute zero

Detectors must be cooled even further, to 0.05 K. A magnetic field aligns salt molecules in a "salt pill." As they drift out of alignment they absorb heat. Realignment pumps heat out of the capsule.

Sensing the far infrared

Far-infrared photons are feeble. The detectors would rely on superconducting circuits with zero resistance. In one type, the detector is kept right at its superconducting transition temperature. Slight heating from an absorbed photon would create a sharp, detectable rise in resistance.

Large UV Optical Infrared Surveyor

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LUVOIR detects ultraviolet, visible and infrared light

Primary mirror size: 15 meters

Instruments: Four

Orbit location: Sun-Earth L2

Launcher: Space Launch System block 2

Launch mass: 25 metric tons

Primary science targets: Earth-like exoplanets and first galaxies

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LUVOIR, like the Hubble Space Telescope, would gather light over a broad spectrum. But Hubble’s mirror is 2 meters across, whereas LUVOIR’s may be 15 meters, larger than any ground-based telescope today. LUVOIR will scrutinize Earth-like exoplanets for signs of life, and watch gas cycling in and out of galaxies to fuel star formation.

LUVOIR comes with risks. Its mirror will require complex origami to fit inside a rocket fairing, and the necessary heavy-lift rocket, a version of NASA’s troubled Space Launch System, may never materialize. At more than twice the size of the James Webb Space Telescope(JWST), LUVOIR may cost twice as much, critics say.

Not so, supporters argue: The mirror is only a fraction of the mission’s cost, and LUVOIR won’t need the elaborate sunshield or cryocoolers that were essential for JWST’s infrared instruments.

Folded for liftoff

LUVOIR’s mirror will fold to fit inside the 8.4-meter-wide fairing of NASA’s Space Launch System (SLS) block 2. The troubled heavy-lift rocket isn’t expected until the 2030s, however, and it may never fly.

Movable mirrors

Tiny pistons will tip and tilt LUVOIR’s 120 mirror segments into a perfect shape with the help of 622 edge sensors.

Built to last

Robotic servicing missions could extend LUVOIR’s life to several decades. Standardized valves, latches, and rails ease the replacement of batteries, solar panels, computers, reaction wheels, and propellant. Rotating the mirror away from the sunshield eases instrument replacement.

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Producer: Jia You   Supervising producers: Alberto Cuadra, Beth Rakouskas   Graphics: Chris Bickel   Web development: Jia You   Illustration: Eiko Ojala   Animation: Nirja Desai   Text: Daniel Clery   Editor: Eric Hand