- 3925 - GAMMA RAY BURSTS - detected by satellites? Tiny satellites could revolutionize the study of “Gamma Ray Bursts” which are the most energetic explosion in the cosmos and help astronomers untangle the mysteries of colliding stellar remnants that produce powerful gravitational waves.
-------- 3925 - GAMMA RAY BURSTS - detected by satellites?
- The birth of
“cubesats” is perhaps the space industry's most game-changing innovation of
recent decades. Big science can be done
with these cheap, easy-to-build space satellites the size of a bread box.
-
- Elusive
gamma ray bursts are really bright and all you need is a relatively small
detector to spot them. Gamma-ray bursts
are the highest-energy explosions known to take place in the universe.
Astronomers believe that only the Big Bang produced more energy than these
mysterious flashes of super-energetic photons that come from distant galaxies.
-
- In the 1990s
astronomers first discovered that short gamma-ray bursts are likely caused by
collisions of neutron stars, super-dense remnants of giant stars that prior to
their death were over ten times more massive than our sun.
-
- The
long-lasting bursts occur when even larger stars explode into supernovas at the
end of their lives and then turn into black holes. Both of these events emit
jets of super energetic material that illuminate the surrounding universe like
the beam of a flashlight.
-
- Satellites
orbiting Earth only detect a gamma-ray burst when this flashlight is directed
toward our part of the cosmos, but detecting a gamma-ray burst is not a rare
event. Almost every day, one flashes briefly at our planet from somewhere in
the universe. Many more are believed to take place throughout the cosmos that
go undetected because the "flashlight" is not aimed at us.
-
- Because
gamma-ray bursts are so fleeting, astronomers don't always manage to locate
their source. In fact, only about 30% of detected gamma-ray bursts get tracked
to their origins. This is a problem that
cubesats could solve.
-
- The
15-year-old Fermi satellite is the current flagship gamma-ray burst
spotter. Optimized to detect super high
energy gamma radiation, which is billions of times more energetic than what
human eyes can see, this spacecraft detects the vast majority of gamma-ray
bursts aimed at Earth.
-
- However,
they don't do a very good job finding the source of those flashes. Another NASA
spacecraft, “Swift”, just a year and a half short of its 20th birthday, is
equipped to find the source of gamma-ray bursts. Swift, however, only sees
about one ninth of the sky. And since gamma-ray bursts are distributed evenly
all over the universe, Swift only detects a small fraction of them.
-
- “Swift” misses 8 out of 9 gamma-ray bursts. We don't have a mission that would cover the
full sky and also provide localization. A whole constellation “Cubesats” could
make up for the shortcomings of the existing, aging gamma-ray burst-detecting
fleet.
-
- Astronomers
can then measure the difference in time between when the different cubesats
detect the gamma-ray burst and you can triangulate the position of the
gamma-ray burst on the sky.
-
- A new
detector that would fit on a cubesat, the smallest type of cubesat measuring
only 3.9 by 3.9 by 3.9 inches in size.
“GRBAlpha” has been orbiting Earth 340 miles above the planet's surface.
-
- The
innovative detector bolted to the tiny satellite's surface has been exceeding
the team's expectations from the start.
The first burst was detected in August 2021. Since then, GRBAlpha has detected 22
gamma-ray bursts.
-
- In 2020,
three times larger than GRBAlpha, the Czech Republic's VZLUSAT-2 has been
orbiting Earth since January 2022, having scored 12 gamma-ray bursts since
then.
-
- In
addition to these powerful flashes of light, colliding neutron stars (and
possibly supernova explosions too) produce another fascinating phenomenon:
Gravitational waves.
-
- First
predicted by the iconic physicist Albert Einstein in 1916, gravitational waves
are ripples in spacetime that arise from the interplay of gravitational forces
of two or more supermassive objects, such as neutron stars and black holes.
-
- Across the
universe, these objects frequently get pulled into each other's sphere of
gravitational influence and start orbiting each other. Gradually, they spiral
closer and closer to each other and eventually collide, the collision producing
a gravitational tsunami that can be detected from Earth by gravitational wave
detectors such as the American LIGO (The Laser Interferometer
Gravitational-Wave Observatory) and the European Gravitational Observatory
Virgo.
-
- Having made
its first ground-breaking gravitational wave detection in 2015, LIGO is
currently undergoing upgrades and will start its next observing run later this
year, 2023
-
- Swift,
Integral and Fermi are all way past their originally planned lifetimes.
Replacing them with new, large space telescopes would take years and cost
hundreds of millions of dollars. In comparison, the constellation of cubesats
would come with a friendly price tag of only about 10 million dollars and could
be up and running within less than three years.
-
- Teams from
all over the world working on cubesat missions to detect gamma-ray bursts met
at a conference in Brno, the Czech Republic, in 2022.
-
- An Italian
project called HERMES won European Union funding in 2018 to build and launch a
constellation of six gamma-ray burst-detecting 3U cubesats (three times larger
than the tiny, pioneering GRBAlpha).
-
- The first
of these spacecraft is expected to launch in the second half of 2024. Prior to that, the HERMES project team will
fly a hosted payload on a cubesat built by the University of Melbourne,
Australia, which is set for launch at the end of 2023.
-
- The HERMES
satellites are quite a bit more sophisticated than GRBAlpha, featuring a
detector sensitive to gamma-rays but also the slightly less energetic X-rays.
-
- The
satellites are also equipped with a set of high-tech sensors including GPS
receivers and accelerometers that will be able to report the spacecraft's
positions with an accuracy of a few meters. And since there will be six of
these satellites astronomers will be able to use the minuscule time difference
in the arrival of the gamma-ray burst at the individual satellites, to
calculate the location of the burst's source.
-
- NASA is
also working on a gamma-ray burst-detecting cubesat. The BurstCube, twice as
big as the HERMES satellites, is expected to launch by the end of 2023.
-
- GRBAlpha's
somewhat larger and more complex successor GRBBeta has its ride to space booked
on the debut flight of Europe's new Ariane 6 heavy-lift rocket, which is
expected to take place by the end of this year, 2023.
-
- Now we can
all coordinate our efforts and build the constellation together. Most of these
cubesats are built by small teams that have limited funding, but by working
together, we can do it easier with the funding that we have.
-
March 21, 2023 GAMMA RAY
BURSTS - detected by satellites? 3925
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