We are all, in my opinion, rightfully excited
about the James Webb Space Telescope launch
in 2021.
Such a powerful space telescope will allow
us to see things extremely far away with a
heretofore unprecedented fidelity.
However, there’s another telescope also
due to be completed in 2021 that no one is
talking about, even though it is the top-ranked
ground-based project in the Astrophysics Decadal
Survey of 2010.
What is it, and what does it do?
Why do astronomers consider this project to
be quite so important?
I’m Alex McColgan, and you are watching
Astrum, and together we will go through everything
you could want to know about the Vera C. Rubin
Observatory.
Very interestingly, the Rubin Observatory
is not connected to a major space agency.
Funding has actually come from the United
States’ National Science Foundation and
Department of Energy, and the management is
overseen by the Association of Universities
for Research in Astronomy.
Also, it’s being built in Chile, the location
of many ESO telescopes, but these aren’t
connected.
Chile just so happens to be an amazing place
for a ground-based telescope, with its high
mountain range and little to no cloud cover.
This is important, because the Rubin Observatory’s
primary goal is to survey the entire visible
sky every few days.
It will do this with its incredible 8.4m mirror
and 3.2 gigapixel camera.
Just to give you some perspective, the mirror
is the width of a tennis court, and the camera
is the largest ever constructed.
It’s 3m long and about 1.6m wide.
The lens of the camera allows the telescope
to view 3.5 degrees of the sky at the same
time.
This is a really big area of the sky; the
Moon and Sun are only about half a degree
across.
This camera is also capable of viewing from
the near ultraviolet to the near infrared
wavelengths.
It does this with a robotic arm that changes
filters placed in front of the sensors.
You see, certain objects or events that happen
in our sky are brighter in specific wavelengths
of light.
But what is the Rubin Observatory designed
to look at?
Because it’s conducting a sky survey, it’s
looking out for pretty much everything.
It’s particular science goals are to look
out for: Evidence of Dark Matter and Dark
Energy, mapping small objects in the solar
system, particularly near-Earth asteroids
as well as larger objects in the Kuiper Belt,
detecting supernovae in our galaxy and beyond,
gamma-ray bursts, quasar variability, gravitational
lensing, and lastly it will map the stars
in the Milky Way.
There have been plenty of sky surveys in the
past, notable mentions are the impressive
works done with Gaia, Pan-STARRS, DESI and
the Sloan Digital Surveys.
These are been extremely useful in mapping
our surroundings with extreme accuracy, cataloguing
galaxies, stars and asteroids.
However, the Rubin Observatory will be able
to see a lot more than any of these previous
surveys.
At the end of ten years of operation, it is
expected that data from the Rubin Observatory
will allow us to catalogue 10-100 times more
asteroids larger than 140m than what we currently
know about, or around 62% of what probably
exists in a near-Earth orbit.
With its wide field of view, gravitational
wave events that are detected by LIGO might
be visible in an image taken by the Rubin
Observatory.
LIGO is also predominately a National Science
Foundation project, a very special type of
observatory that uses mirrors spaced four
kilometres apart which are capable of detecting
a change of less than one ten-thousandth the
charge diameter of a proton.
These changes can occur as gravitational waves
pass through the facility.
The sources of these waves come from really
big events, like neutron stars or black holes
colliding, which creates a ripple in spacetime
that propagates outwards from the location
of the event.
These events are usually so far away that
by the time they reach us, we need a sensitive
observatory like LIGO to even detect them.
Gravitational waves travel at the speed of
light, so if we detect the gravitational waves,
there should also be light coming from the
source.
With such events, we only roughly know the
direction of where it could have come from
due to the way we detect the events with LIGO,
so to visually see it with a telescope, time
is spent scanning the sky, by which point
we may well have missed it.
However, if you have a telescope capable of
seeing a big chunk of the sky at the same
time with a super high resolution camera,
you can take lots of photos and search the
data later to try and locate the event and
see if it was visible.
So, how will it be able to achieve these science
goals?
The telescope will typically observe a section
of sky for 15 seconds.
A 15 second exposure is a compromise between
being able to see faint objects like distant
stars and moving objects like asteroids.
If you have much more of an exposure, you
may see more faint objects but streaks across
the image will ruin the shots from the moving
objects.
In order to eliminate the noise from cosmic
rays hitting the camera sensor, two images
of the same region will always be taken and
can then be merged.
The camera’s images will be so large that
a year’s worth of data will come to about
1.28 petabytes.
And because the observatory is located in
Chile, and the data processing facility is
in the States, a special 100 Gbit/s internet
connection had to be specially built between
the two locations.
Unfortunately though, there is a pretty major
problem coming up that designers may not have
fully envisaged when in the planning and early
construction phases of this project.
Any guesses to what would affect a highly
sensitive ground-based telescope that wasn’t
such an issue 10 years ago?
Not pollution, not light from cities, but
actually the tens of thousands of cube satellites
currently being launched into space from the
likes of SpaceX and Amazon.
If a satellite passes through an image, it
will ruin the exposure because it is so bright
compared to the dimmest objects the telescope
is looking for.
As a result, SpaceX have committed to painting
their future satellites black or send them
up with a kind of sunshade to reduce how bright
they are, but this certainly won’t negate
the problem.
And in reality, low-Earth orbit is only going
to get busier.
This puts a serious dampener on the future
of highly sensitive ground-based telescopes.
In reality, the serious issue here is that
there are currently no internationally agreed
regulations about what can be put into LEO,
it’s the wild west right now.
Not to mention how this increase the chances
of Kessler syndrome, which I have already
done a video about here if you want to know
more.
But all in all, this is a very exciting project,
and even with these obstacles, I’m sure
it will acquire a wealth of valuable data.
Perhaps it will even witness events we have
never even conceived possible before!
So, there we have it, an insight into the
most exciting telescope that hopefully more
people will begin talking about.
Thanks for watching.
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A big thank you as well to my patrons and
members, your support means a great deal.
All the best, and see you next time.
