Sky & Telescope - August 2024 - 19

GABRIEL PÉREZ DÍAZ / IAC / CC BY-NC-ND 2.0 DEED
CTAO SCOPES
This schematic shows
the three classes of telescopes
that the CTAO will
ultimately include. Each
is designed for a different
energy range. Four
Large-Sized Telescopes
(LSTs) will cover 20 to
100 GeV, 23 MediumSized
Telescopes (MSTs)
will observe the core
energy range (100 GeV to
10 TeV), and 37 SmallSized
Telescopes (SSTs)
will reach up to 300 TeV.
see the same white dwarf erupt multiple times.
On August 8, 2021, the light of one of these explosions
from the object RS Ophiuchi reached Earth, after traveling
for nearly 9,000 years. Again, the Fermi satellite alerted
MAGIC, which was able to detect gamma-ray emission in the
60 to 250 GeV energy range.
By combining the Fermi and MAGIC observations,
researchers concluded that the gamma rays detected by
MAGIC were from protons accelerated to near the speed of
light by powerful shockwaves produced by the nova explosion.
This discovery helps explain the origin of a portion of cosmic
rays out there, because it shows that novae can accelerate
protons to these high energies.
" For galactic cosmic rays, we still don't know how or where
[they] are accelerated or how they propagate, " says LópezCoto.
" There are lots of open questions, and being able to add
one piece to the puzzle, to say, 'There, what is being accelerated
are protons,' is very important. "
Looking Forward
Given MAGIC's ongoing discoveries, scientists are eager to
start working with the new CTAO. However, after navigating
both a global pandemic and a volcanic eruption in 2021 that
halted operations for months, those in charge are wary of giving
dates for the beginning of science observations.
" I expect in my best dreams that the first telescope will be
opening for early science by 2026 or late 2025, " Calisse says.
La Palma's three remaining LSTs and the smaller telescopes
should follow soon thereafter. In the meantime, in Chile, the
access road to the observatory has just been completed, and
the construction of the inner roads and telescope foundations
will begin soon. Construction of the first telescopes
there won't start until 2026.
That isn't stopping astronomers from doing research now,
though. The LST-1, still under commissioning, is already
making discoveries. In December 2023, scientists reported
the detection of the most distant quasar emitting at very high
energies that's been found to date. It's the second most distant
gamma-ray source ever observed, with a redshift of 0.997,
meaning its light has traveled nearly 8 billion years to reach us.
When completed, CTAO will be the largest and most sensitive
detector of gamma rays in the world. It will cover a wide
range of energies, from 20 GeV up to 300 TeV, pushing the
edge of the observable electromagnetic spectrum. Researchers
expect that it will add more than 1,000 new sources to the
roughly 250 known today.
" For everybody in the field it's evident that we are seeing
only the tip of the iceberg, " Lindfors says. " There are a lot of
sources that we can only see when they are brightly flaring,
because the current telescopes aren't sensitive enough. " Then
there's the unexpected, she adds. " The history of science
shows that in addition to the guaranteed, you will see some
things that you didn't expect, and of course that is the most
exciting part. "
¢ Contributing Editor JAVIER BARBUZANO (@javibarbuzano)
is a science journalist based in Barcelona, Spain. He daydreams
about living on La Palma.
sk yand tele scope .o r g * AUGUST 2024 19
https://skyandtelescope.org/
Sky & Telescope - August 2024

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