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A proposed future space telescope will be designed
specifically to seek out signs of life in the atmospheres of nearby
planets.Image Credit: ESA, NASA, Hubble; Artist: M. Kornmesser
All good things must come to an end, and it’s best
to plan beforehand. Revolutionary as the JWST has been, it has a much shorter
life expectancy than the Hubble Space Telescope, let alone ground-based
instruments. NASA has revealed plans for what could be the replacement to its
replacement at the American Astronomical Society’s 241st meeting.
Their proposal is for an instrument that could carry
the space telescope torch after the Nancy Grace Roman Observatory (NGRO), which
is scheduled to launch around 2027, about the time the JWST ceases operations.
The future telescope does not have its final name
yet, but NASA’s Mark Clampin told the audience that the project is being
planned as the Habitable Worlds Observatory (HWO). Neither details nor funding
have been confirmed, but as its working name suggests the project will be much
more focused on a single task than the JWST or Hubble.
The JWST is already examining the atmospheres of
planets orbiting nearby stars. This, however, represents just a small part of
its operations, with more time studying the most distant galaxies, star-forming
regions in our own, and a host of other targets. The HWO will be designed to
look for “biosignatures”, gases in the atmospheres of rocky or watery planets
within stars’ habitable zones.
The plans are designed to meet the call in
astronomy’s decadal survey for an instrument capable of detecting signs of life
on 25 nearby planets. Hopefully, it will find unambiguous evidence for a
biologically created atmosphere before that – but 25 is considered sufficient
to indicate life is very rare if none show positive signs.
Although it may have a clearer prime objective than
its predecessors, the HWO will be capable of many other tasks. As probably the
most powerful space telescope in operation for at least the initial years of
its life, plenty of astronomers with other specialties will compete with
exoplanet researchers for time directing it to their projects.
The HWO is expected to be a similar size to the JWST
and likewise located at L2: the point 1.5 million kilometers (932,057 miles)
from Earth where gravitational forces cancel out sufficiently for orbital
stability.
The downside to this location is that repairs,
upgrades, and refueling have been considered impractical for the JWST, which is
why it's not expected to last more than ten years. Hubble, meanwhile, is in its
third decade thanks to several maintenance missions to Low Earth Orbit.
However, Clampin indicated that NASA thinks by the
time the HWO launches, robot missions will be able to reach the site to service
it. This will not only enable a much longer life than the JWST, but create the
possibility of upgrades making it more powerful with time.
“Serviceability will be huge,” Aki Roberge of NASA’s
Goddard Space Flight Center told ScienceNews. Although the mirrors would stay
the same, the instruments used to process the light they collect could improve,
creating what Roberge called a “mountaintop observatory at L2.”
The current HWO plans fall between two previous
concepts NASA has floated in more detail, known as HabEx and LUVOIR. It’s expected to build on the success of the
JWST’s unfolding multi-component mirror, keeping to a similar scale, since we
now know how to do this, and using features that will get a test run on the
NGRO.
LUVOIR’s design is much bigger and more ambitious,
but also likely to take longer and be more expensive, suggesting the HWO might
be an intermediary. HabEx has been foreseen as having a single mirror,
individually larger than any of the JWST’s and therefore capable of crisper
images, but smaller than the combined power of the JWST’s 18.
Unsurprisingly, considering the early stage of the
plans, there is no firm timeline for the HWO other than Clampin talking about
it launching in the 2040s. Considering how many delays were required for the
JWST, it may be just as well to provide a decade-long range, particularly with
the limitations on this portion of NASA’s budget.
Many other important but smaller and more
specialized space telescopes are, or recently have been, in operation,
including Gaia, Spitzer, Kepler and
TESS. However, when it comes to large
instruments operating in the optical or near-optical part of the spectrum the
HWO is intended to continue a dynasty that runs from Hubble to the JWST and
then the NGRO.
Reference: ScienceNews
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