University Assitant Professor Saurabh Jha co-authored the High-z
Supernova Search team’s discovery paper in 1998 that explained how
the expansion of the universe was accelerating rather than
decelerating.
This same paper earned the research team’s leaders Brian Schmidt
and Adam Reiss the 2011 Nobel Prize in Physics, which were awarded
last week.
“What astronomers and physicists expected was that if you were to
watch the galaxies for a long time, you would still see them move
apart, but that expansion should be slowing down,” said Jha, an
assistant professor for the Department of Physics and
Astronomy.
But the research showed the universe was in fact moving apart
faster, Jha said.
Edwin Hubble, Hubble Space Telescope’s namesake, discovered that
the universe is expanding in 1929, he said. This means that distant
galaxies are moving away from our Milky Way galaxy, demonstrating
all galaxies are moving apart from other galaxies.
A useful analogy to understand the concept is to imagine throwing a
ball up in the air and watching it rise, Jha said. The ball
represents a galaxy, and as it moves away from us, it shows that
the universe is expanding.
Since we expect the ball to slow down as it moves away, we
eventually expect the ball to stop and come back down, all due to
the force of gravity, he said.
“There is gravity between all the galaxies, too, and so that’s why
everyone expected that the expansion of the universe should be
slowing down as well,” Jha said.
Scientists believed it was possible for expansion to stop at some
point, resulting in the universe collapsing in on itself — a
scenario called “big crunch,” he said.
Rather than waiting a long time to see what the expansion of the
universe does in the future, both the High-z Supernova Search Team
and fellow researchers at the Supernova Cosmology Project went out
to try to measure this with telescopes to see what it was like in
the past, Jha said.
“We used many telescopes, both on the ground, like at the Cerro
Tololo Inter-American Observatory in Chile, as well as the Hubble
Space Telescope to measure the distance to the supernovas and the
speed at which their galaxies were moving away from us,” he
said.
It is possible to look into the past, because light from objects
that are billions of light-years away can be seen by capturing
pictures from telescopes, Jha said.
“We observed a certain class of objects, exploding stars called
type 1a supernovas, which helped us measure how fast the universe
was expanding in the past,” he said.
To everyone’s surprise, the hypothesis did not match the
observation, and the universe was expanding faster.
“It was as if you threw a ball up in the air, and instead of it
rising and falling back down, it started speeding up faster and
faster. A ball on earth doesn’t do that, but the universe does,” he
said.
The third Nobel Prize laureate, Saul Perlmutter, who was the leader
of the Supernova Cosmology Project team, came to the same
conclusion and received the Nobel Prize independently, Jha
said.
One of the major implications of the research is the discovery that
something has to cause the Universe to expand faster, and no one
knows what it is, Jha said.
“From the measurements and subsequent work, we know that about 70
percent of the universe must be made of this, what we call, ‘dark
energy,’” he said. “That is incomprehensible.”
Eric Gawiser, assistant professor in the Department of Physics and
Astronomy, said the research has raised more questions.
“We still have no idea what dark energy really is or why it exists,
so this discovery created the biggest current mystery in physics,”
he said
If the dark energy continues to act like it does today, the
universe will continue to expand faster and faster, Jha said.
“That means all the other galaxies that are out there will
eventually get so far away from us that we won’t be able to see
them anymore. So it could be that the universe will become a very
lonely place in the next 100 billion years,” he said.
Many people are working to try to understand the properties of dark
energy more precisely and tell the difference between the different
possibilities, Jha said. It is right at the forefront of modern
astrophysics research.
Jack Hughes, a professor in the Department of Physics and
Astronomy, said the big question in cosmology for the last 70 years
was how fast is the universe slowing down.
“This boiled down to how much matter the universe contained. More
matter [meant] the universe slows down more quickly, less matter
and the universe slows down less quickly,” he said.
But since then discovery theorists are working to come up with
other models to explain the accelerating universe, Hughes
said.
“It is also possible that Einstein’s theory of general relativity
is incomplete and needs to be modified,” he said.
But Albert Einstein might have already come up with an explanation
for the phenomenon, Jha said.
Einstein proposed the theory of the “cosmological constant,” which
argued that empty space itself has a tendency to expand. This
results in the creation of more empty space, which also wants to
expand — creating more empty space at a faster rate.
“Because there was no evidence for this during Einstein’s life, he
is supposed to have called it his ‘greatest blunder,’” he said.
“However, this work shows that Einstein might have been right after
all.”
Another major implication is measuring how the expansion of the
universe has been changing by figuring out when the expansion
started — that is the beginning of the universe’s “big bang,” Jha
said.
“Based on the supernova measurements and other recent work, we now
know that the Universe is 13.7 billion years old,” he said.
Nobel prizes are not awarded right away — often the prizes are
given many decades after a discovery, when people are able to
determine the importance of a particular discovery, Jha said.
“Since 1998, our two teams’ discovery has been checked and
confirmed with more data and different techniques, such that the
accelerating universe is now an accepted part of astrophysics and
is in all the modern textbooks,” he said. “It really was a
revolution in our understanding of the universe.”
Hughes said the expansion of the universe has dominated the field
of cosmology since the discovery in 1998 for both theorists and
observers.
“Both NASA and the European Space Agency are planning new space
telescopes designed to characterize the properties of the
mysterious ‘dark energy’ that is driving the acceleration of the
universe,” he said.
Article source: http://www.dailytargum.com/news/professor-plays-role-in-prize-winning-research/article_6d951c82-f3ba-11e0-8217-001a4bcf6878.html
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Name: Eduard Rusu
