NASA’s Next “Hubble” Will See 100x More Sky

Representing a narrow “keyhole” view stretching to the visible horizon of the universe, this 1995 Hubble Deep Field image covers just a speck of the sky.  In this small field, Hubble uncovered at least 1,500 galaxies at various stages of evolution. NASA/ESA

Do you drool over Hubble Space Telescope photos like I do? The color, clarity and level of detail astound. Of course, it helps that the scope does its work above the blurring effects of Earth’s atmosphere. What makes the images even more amazing is that Hubble’s field of view — the little circle of sky the camera sees — is only 2.6 arc minutes wide or less than 1/10th the apparent diameter of the full moon. That’s narrower than looking through a skinny, juice-box straw.

Astronomers get around this restricted view by taking multiple photographs and stitching them together. The first Hubble Deep Field image that revealed more than 1,500 galaxies in a minute bit of sky in Ursa Major required 342 separate exposures.

Hubble sees only a tiny bit of sky at a time compared to the view in the new WFIRST scope. NASA/ESA

That’s soon to change. NASA’s now in the early stages of designing its next big space telescope with a picture window view called the Wide-Field Infrared Survey Telescope or WFIRST. Scheduled to launch in the 2020s, WFIRST will be equipped with a 300-megapixel camera that will image a sky area 100 times larger (equal to 18 arc minutes or two-thirds the apparent diameter of the full moon) than Hubble with the same clarity. Put another way, a single WFIRST image will hold the equivalent of 100 Hubble photos.

“A picture from Hubble is a nice poster on the wall, while a WFIRST image will cover the entire wall of your house,” said David Spergel, co-chair of the WFIRST science working group, in a press release.

Rather than orbit the Earth as Hubble does, WFIRST will orbit about a stable region of space located a million miles on the opposite side of the Earth from the sun called the L2 Langrange point. With the sun, moon and Earth behind it, the new telescope will get choice views of deep space. WFIRST will let astronomers take extremely detailed wide-field views of the sky in hopes of shedding light on lots of thorny topics such as dark energy (the energy behind the unexplained acceleration of the expansion rate of the universe) and the nature of dark matter. Regular matter, like the material found in a good hamburger, makes up just a fifth of all the matter in the universe. The rest is invisible but detectable through its gravitational pull on ordinary matter. What it’s composed of remains a mystery.

WFIRST will have the same size mirror as the Hubble but a camera with a field of view 100 times wider.  It’s optimized to study the universe in near-infrared light (light just beyond the red end of the spectrum), good for penetrating dust. NASA

To learn more about dark energy, WFIRST will use its powerful 2.4-meter (94.5-inch) mirror and Wide Field Instrument to do two things: map how matter is structured and distributed throughout the cosmos and measure how the universe has expanded over time. In the process, the mission will study galaxies across cosmic time, from the present back to when the universe was only half a billion years old, or about 4% of its current age.

“To understand how the universe evolved from a hot, uniform gas into stars, planets, and people, we need to study the beginnings of that process by looking at the early days of the universe,” said WFIRST Project Scientist Jeffrey Kruk.

WFIRST will study exploding stars called supernovae, determine precise distances to galaxy clusters and map out the distribution of galaxies in three dimensions to learn how they grew over time. The mission will also pinpoint the distances to millions of galaxies by measuring how their light becomes redder at greater distances, a phenomenon called redshift and due to the expansion of the universe. The farther off a galaxy is, the redder its light appears when we see it. Mapping out the 3-D positions of galaxies will allow astronomers to measure how the distribution of galaxies has changed over time, due in part to dark energy’s effects.

WFIRST’s coronagraph will blot out the glare of a planet’s host sun to get direct images of the planet itself (right). NASA

WFIRST will also monitor 100 million stars for hundreds of days and detect some 2,600 new planets through microlensing events. In microlensing, a foreground star in our galaxy acts as the lens. When its motion randomly aligns with a distant background star, the lens magnifies, brightens and distorts the background star. As the lensing star drifts along in its orbit around the galaxy and the alignment shifts, so does the apparent brightness of the star. These changes can reveal planets orbiting the lensing star because the planets themselves serve as miniature gravitational lenses. Lots of these will lie in the habitable zones around their host suns where liquid water may exist.

Even more exciting, WFIRST will have a coronagraph to block out the light from a host sun and directly photograph giant planets and measure their atmospheric compositions.

Just thought you’d like to have something to look forward to in case you’re tired of all the cold weather.

8 Responses

  1. Catherine Koemptgen

    Thanks, Bob, for sharing this exciting news. We’re currently in Tucson and Joel and I want to visit the Mirror Lab at the U of AZ. I’m going to ask them if they will be (or already are) creating the WFIRST mirror lens.
    Catherine Koemptgen

    1. astrobob

      Hi Catherine,

      Nice to hear from you. Sounds like a place I’d enjoy visiting, too. Let us know if they’re working on it.

    1. astrobob

      Hi Jack,

      I don’t know for a fact but given that the telescope’s resolution will be the same as Hubble’s, it will be able to image the planets and detect atmospheres but not show them as disks.

    1. astrobob

      Hi Art,

      Hubble’s field is 2.6 arc minutes by 2.6 arc minutes (Wide-field planetary camera). Multiply by 100 and you get 260 arc minutes wide, then divide by 60 to get 4.3° = about 8 full moons wide. Check the math for me but this looks correct.

        1. astrobob

          Hi Art,
          Thank you for pointing this out. I interpreted the 100x based on WIDTH of field rather than area. I think you’re right, so I’ll make the correction. I very much appreciate your input on this.

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