- 4074 - NEW
SPACE TELESCOPES - Depending on what they find, Roman and
Euclid telescopes could confirm that General Relativity and the predominant
model of the cosmos, the Lambda Cold Dark Matter (LCDM) model, is correct. On
the other hand, they could verify that our models need revision and point the
way toward a grand resolution.
-
---------------------------- 4074 - NEW SPACE TELESCOPES
- Since the 1990s,
thanks to observations by the Hubble Space Telescope (HST), astronomers have
contemplated the mystery of cosmic expansion. While scientists have known about
this since the late-1920s and early-30s, images acquired by Hubble‘s Ultra Deep
Fields campaign revealed that the expansion has been accelerating for the past
six billion years!
-
- This discovery led
scientists to reconsider Einstein’s theory that there is an unknown force in
the Universe that “holds back gravity,” which he named the “Cosmological
Constant”. To astronomers and cosmologists today, this force is known as “Dark
Energy.”
-
- Some scientists
believe that this cosmic expansion could mean there is a flaw in our
understanding of gravity. In the near future, scientists will benefit from
next-generation space telescopes to provide fresh insight into this mysterious
force.
-
- These new
telescopes include the ESA’s “Euclid” mission, scheduled for launch this July,
2023, and NASA’s “Nancy Grace Roman Space Telescope” (RST), the direct
successor to Hubble that will launch in May, 2027. Once operational, these
space telescopes will investigate these competing theories to see which holds
up.
-
- The expansion of
the cosmos was discovered by Belgian astronomer Georges Lemaître in 1927 and
independently by Edwin Hubble in 1929. These observations triggered a debate
about the nature of the Universe and whether every galaxy emerged from a single
event ( the Big Bang Theory) or new galaxies were added over time (the Steady
State Hypothesis).
-
- The debate would
be settled with the discovery of the Cosmic Microwave Background (CMB), the
“relic radiation” of the Big Bang, and improved instruments that allowed
astronomers to look deeper into space (and farther back in time).
-
- Over time,
astronomers and cosmologists were able to place tighter constraints on the rate
at which the cosmos is expanding – known as the Hubble Constant. But by the
1990s, observations of Type Ia supernovae (used to measure cosmic distances)
revealed that the rate began increasing about 8 billion years after the Big
Bang.
-
- This contradicted
the widely-held idea that cosmic expansion would slow over time as gravity
would slowly arrest it, eventually causing the Universe to contract, possibly
ending in a “Big Crunch.”
-
- The fact that it has
accelerated over time suggests that something is working against gravity (Dark
Energy) or that our understanding of how gravity works on the largest of scales
is incomplete. For over a century, scientists have looked to Einstein’s Theory
of General Relativity to describe this, but cosmic expansion has led scientists
to propose alternate theories, like Modified Newtonian Dynamics (MOND).
-
- Twenty-five years
after its discovery, the Universe’s accelerated expansion remains one of the
most pressing mysteries in astrophysics. With these upcoming telescopes, we
will measure Dark Energy in different ways and with far more precision than
previously achievable, opening up a new era of exploration into this mystery.
-
- Roman and Euclid
telescopes will provide separate data streams to fill the gaps in our
understanding, hopefully pinning down the cause of cosmic acceleration in the
process. This will start with both observatories studying the accumulation of
matter using a technique known as “weak gravitational lensing,” where the
presence of massive objects in the foreground warps and amplifies light from
more distant objects.
-
- This phenomenon is
predicted by General Relativity, which describes how the curvature of spacetime
is altered in the presence of gravitational forces. In this case, the observatories will look for
subtle effects caused by less concentrated masses, like clumps of Dark Matter.
-
- This data will be
used to make a 3D map of Dark Matter, which is theorized to account for
approximately 85% of matter in the known Universe and is what holds galaxies
and galaxy clusters together. By mapping the concentrations of Dark Matter,
this map will offer clues about the push-pull forces governing our Universe
since the gravitational pull of Dark Matter counteracts the expansionary forces
of Dark Energy.
-
- The two missions
will also study how galaxy clustering has changed from one era to the next.
When examining the local Universe, astronomers have noted a pattern in how
galaxies are distributed, where any galaxy is twice as likely to have a
neighboring galaxy about 500 million light-years away.
-
- This distance has
grown over time due to the expansion of space, which means that this “preferred
distance” has likely changed as well. Seeing how this has varied over time will
reveal the expansion history of the cosmos and allow for highly-accurate tests
of gravity to see if Dark Energy or MOND is at work.
--
- Roman telescope
will also conduct an additional survey of Type Ia supernovae and study how
quickly they appear to be moving away from us. Comparing the speed at which
they are receding at different distances, scientists will have another means of
tracing cosmic expansion and shed light on if and how the influence of Dark
Energy has changed over time.
-
- Euclid telescope
will rely on optical and infrared instruments to observe an area measuring
approximately 15,000 square degrees, much larger than the area observed by
Roman. It will peer back 10 billion years, roughly 3 billion years after the
Big Bang, when the Universe was expanding much slower than it is today.
-
- Roman teleacope
will study an area measuring about 2,000 square degrees (one-twentieth of the
night sky) but in much greater depth and detail. Using its advanced optical and
infrared imaging modes, Roman will visualize what the Universe looked like just
2 billion years after the Big Bang.
-
- This will allow
Hubble’s successor to examine galaxies that formed during Cosmic Dawn,
something the James Webb Space Telescope recently did for the first time. And
whereas the Euclid mission will focus exclusively on cosmology, the RST will
observe nearby galaxies, stars, and the outer Solar System.
-
-
July 1, 2023 4063
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Sunday, July 2, 2023
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