প্রকাশ: 12/12/2021
Peering into
deep space and billions of years back in time, the James Webb telescope
promises to offer the clearest glimpse yet of the Universe's cosmic dawn, when
the earliest galaxies began to form.
The largest
and most powerful telescope ever to be launched into space, which will take
over from Hubble, will "directly observe a part of space and time never
seen before", says NASA.
This is the
Universe in its youth, just a few hundred million years after the Big Bang.
With
"very lofty science goals in mind", Webb will look back 13.5 billion
years to when the first galaxies evolved in the Universe, said Begonia Vila,
instrument systems engineer at NASA's Goddard Space Flight Center in a
briefing.
It aims to
allow us to observe "how they change and evolve to get to the type of
galaxy where we live in today," she said, as well as looking at the first
stars and trying to detect "the type of elements that we identify as a
sign of the life as we know it; water, carbon dioxide, methane".
Looking
farther into space means looking farther back in time because of how long it
takes for light to travel -- sunlight, for example, takes eight minutes to
reach our eyes on Earth.
Hubble
reached its limit at 13.4 billion years, with the discovery of the oldest
galaxy yet observed, GN-z11.
That ancient galaxy may have been an unprepossessing little dot but it was also "a surprise, with a luminosity that one did not expect at such a distance", said the Swiss astrophysicist Pascal Oesch, who first reported GN-z11.
Hubble, which
was launched in 1990, looks mainly at visible light -- but Webb, set to launch
on December 22, focuses on infrared.
Light emitted
by the very first luminous objects has been "redshifted" by the
Universe's continual expansion, according to NASA, arriving today as infrared.
Webb, with
its significantly greater sensitivity than Hubble, is expected to provide much
more detailed images, which Oesch said "will allow us to explore this era
in extraordinary detail".
He is betting
that "many, many more galaxies will then be revealed, but they will be
much less luminous".
Its infrared
capability will also allow Webb to penetrate the interstellar dust clouds that
absorb starlight and hide them from Hubble's view.
This
"makes it possible to see what is hidden in the clouds, the birth of stars
and galaxies", said David Elbaz, an astrophysicist at the French Atomic
Energy Commission.
Webb has been
jointly developed by NASA, the European Space Agency and the Canadian Space
Agency.
The ambition
is to help explain a key stage in the evolution of the Universe, when "the
lights went on, when the very first stars began to form", said Oesch.
After the Big
Bang triggered the expansion of the Universe, it entered a virtually lightless
period, the cosmic dark ages, where it was cast in a gaseous fog of hydrogen
and helium swirled, making it opaque.
This period
continued for hundreds of millions of years until the first stars began to
form.
These are
thought to have been giants -- up to 300 times more massive than our Sun --
that burnt only for a few million years before exploding as supernovae.
How and when
those first stars were formed remains uncertain. One idea is that dark matter
-- a substance whose existence is so far still theoretical -- played a role.
This was a
crucial time in the Universe's evolution, with the radiation from these massive
stars able to split hydrogen atoms back into electrons and protons -- ionising
them.
As it
ionised, the Universe became more transparent, leading eventually to the
"clear" conditions now detected in much of Space.
To study this
phenomenon is to investigate the formation of galaxies.
The hope with
Webb is to see "the first galaxies, which carry the second generation of
stars, which will perhaps teach us things about the first", said Nicole
Nesvadba, astronomer at the Lagrange laboratory of the Observatory of the
Riviera.
And this,
experts hope, will ultimately provide clues to our own existence.
"If we really want to know where our atoms came from, and how the little planet Earth came to be capable of supporting life, we need to measure what happened at the beginning," said John Mather, senior project scientist for the Webb telescope, in comments on the project's website.
প্রধান সম্পাদকঃ সৈয়দ বোরহান কবীর
ক্রিয়েটিভ মিডিয়া লিমিটেডের অঙ্গ প্রতিষ্ঠান
বার্তা এবং বাণিজ্যিক কার্যালয়ঃ ২/৩ , ব্লক - ডি , লালমাটিয়া , ঢাকা -১২০৭
নিবন্ধিত ঠিকানাঃ বাড়ি# ৪৩ (লেভেল-৫) , রোড#১৬ নতুন (পুরাতন ২৭) , ধানমন্ডি , ঢাকা- ১২০৯
ফোনঃ +৮৮-০২৯১২৩৬৭৭