Are aliens hiding behind starlight? #Beekhaybee

Could the light from stars be hiding evidence of
extraterrestrial life? A giant “Starshade” could
soon reveal answers.

Alien hunting isn’t just tabloid fodder anymore.
Over the last few years, astronomers have
discovered thousands of planets outside the Solar
System, suggesting that the galaxy is teeming
with worlds – at least as many as one planet per
star, on average.
The existence of so many planets raises the odds
that at least one of them has life – and it’s
possible there may even be an Earth “twin” –
making alien-hunting a bona fide scientific
endeavour. “We’re now ready to make the
transition from ‘are there planets?’ to ‘is there
life on these planets?’” says Nick Siegler, the
chief technologist of Nasa’s Exoplanet Exploration
Program. “That’s a huge shift in how Nasa’s
thinking about the search for life and what’s next
in the world of planetary science.”
It’s harder than it seems to spot life from millions
of miles away, especially if it’s not intelligent
The trouble is, it’s harder than it seems to spot
life from millions of miles away, especially if it’s
not intelligent. Last week in our series “The
Genius Behind”, we told the story of Sara Seager,
a scientist looking for signs of life on second
Earths, who believes that the key is to scrutinise
the atmospheres of these alien worlds. Find out
why in the film below:
One of the technologies that could help
researchers like Seager achieve their goal is a
seemingly crazy flower-shaped contraption called
Starshade. It’s a sort of giant space parasol
designed to block light from a star, allowing a
telescope to avoid the star’s glare and peer into
the planets in orbit – and, possibly, reveal signs
of alien life.
“If we want to find a true Earth twin in the near
future – like in the next decade or two – then
yes, we definitely need to do the Starshade,” says
Seager, who is based at Massachusetts Institute
of Technology (MIT).
That’s because a Sun-like star is 10 billion times
brighter than an Earth-sized planet. The only
hope astronomers have for glimpsing any hint of
life – likely some form of microorganism – would
be to somehow block the light from such a star,
allowing a telescope to directly observe the planet
itself. It’s a strategy radically different from the
main way astronomers have discovered and
studied planets so far.
Because planets are so distant, small, and faint,
astronomers have mostly probed them indirectly
– for example by detecting dips in starlight when
a planet passes in front of its star or by
measuring how the star wobbles when a planet’s
gravity tugs on it. But alien-hunting demands a
new tactic.
Scientists hope to identify the gases in the
planet’s atmosphere, and detect chemicals that
suggest the presence of life – chemicals like
oxygen, which comprises 20% of Earth’s
atmosphere.
“Without life – plants or photosynthetic bacteria
– we would have virtually no oxygen,” Seager
says. Which is why oxygen is one of the most
promising so-called biosignatures. But life on
Earth produces all kinds of gases, and alien life
could be even more diverse. The challenge is in
determining whether these chemicals are
biological in origin.
Although no-one’s found any signs of life yet,
astronomers have already sniffed out some
atmospheres
Although no-one’s found any signs of life yet,
astronomers have already sniffed out some
atmospheres. When a planet passes in front of its
star, the starlight penetrates the gaseous layer
enveloping the planet. The molecules in the
atmosphere absorb specific wavelengths of light,
depending on what the chemical is. By measuring
which wavelengths are absorbed, astronomers
can identify the gases.
Bigger telescopes like the James Webb Space
Telescope, slated for launch in 2018, will be able
to use this transit technique to resolve
atmospheric chemistry in greater detail. It could
even conceivably detect biosignatures. “It could
get lucky,” Siegler says. But this method is only
good for planetary systems around small stars
called M dwarfs – not around Sun-like stars.
Which is why astronomers like Seager want to
make Starshade a reality. The video below shows
how it might work in space, as well as a
timelapse of the instrument unfurling on Earth.
The Starshade is launched with a telescope, and
when it reaches its position in deep space, it will
unfurl and expand to a diameter as wide as 34m
(112ft). The petals, which will likely be razor-
sharp, remove the effects of diffraction, in which
light waves bend around the edge of the shade
and produce unwanted glare. The shade and
telescope will then separate by as much as
50,000 kilometres (31,250 miles) – almost four
times the diameter of Earth.
Suffice to say, this isn’t easy. But researchers
have shown the idea to work with experiments in
the desert, using a lamp, a model Starshade, and
a camera. Jeremy Kasdin of Princeton University,
one of the leaders of the Starshade project, is
conducting lab tests with a miniature model to
scale – the setup stretches for 78m (257ft), with
a Starshade about five centimetres wide.
If the project gets enough funding and all goes
well, Nasa could launch Starshade as early as
2026. “We don’t see right now any technical
impediments to complete a Starshade and flying
it in the 2020s,” Kasdin says.
But Starshade isn’t the only way to block
starlight. Its launch could coincide with WFIRST,
a next-generation space telescope that’s planned
to be fitted with an instrument called a
coronagraph, which blocks starlight from inside
the telescope. “We want multiple approaches in
case one doesn’t work,” Siegler says.
A coronagraph is a tried-and-tested technology –
first developed in the 1930s to study the outer
layers of the sun called the corona – and could
also find Earth’s twin. But, Siegler says, the
technology isn’t there yet.
Coronagraphs are complex and fragile
instruments, which make them susceptible to the
Sun’s heat and vibrations from things like the
telescope’s reaction wheels used to orient the
spacecraft. Anything that can knock the telescope
off-kilter means stray starlight gets into the
camera, ruining the observations. Deformable
mirrors can cancel out some distortions, but the
current systems can’t pick out an Earth-sized
planet awash in starlight.
Watch how coronagraphs work in this animation:
The Genius Behind
Be inspired by great minds and ideas
This is part of a series called The Genius Behind ,
about the most amazing and sometimes little
known technological breakthroughs, and the
innovative minds behind them.
With Starshade, however, the starlight never even
reaches the telescope. All you need is a relatively
simple and small telescope, which is cheaper and
easier to build. Alternatively, Starshade may not
even need its own telescope, and instead rely on
WFIRST.
In the meantime, the hunt for Earth’s twin is
heating up. “There’s a lot of great science to be
had by looking at planets of all size scales, but
ultimately, most of us really want to find an
Earth-like planet,” says Kasdin. If that happens,
calls will surely grow for answers about whether
it is inhabited – the Starshade and projects like it
may turn out to be our best chance.

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