Hello Space Fans and welcome to another edition
of Space Fan News.
In this episode, some astronomers, a former
astronaut, the current director of the Space
Telescope Science Institute as well as the
wife of Carl Sagan himself, got together and
wrote a white paper that makes the case for
a telescope, named after the famous astronomer
Carl Sagan, that will look for and directly
image planets like Earth around other stars.
If you are a professional astronomer or care
about the future of research in space astronomy,
as most of us Space Fans are, then the next
year or so promises to be rather exciting.
Anyone who’s followed this channel for any
length of time knows about a very important
thing that happens every ten years in professional
astronomy: the Astronomy Decadal Survey; a
once-in-a-decade astronomy nerd-fest where
decisions on what the next generation of astronomers
will be able to undertake, what questions
to ask and of those questions, which one are
within our grasp to definitively answer.
As part of this survey, which they’ve been
doing since 1964, several teams of scientists
create elaborate proposals submitted to the
National Academy of Sciences for missions
they would like to see built that would answer
some of the more exciting questions in astronomy
and cosmology.
These proposals are submitted and reviewed
by a NAS panel that will select and prioritize
these missions.
At the end, a report is written and submitted
to the community and government agencies spelling
out clearly and precisely what astronomers
in the field think are the most important
questions facing astronomy and which of the
proposed missions are best able to answer
them.
But the big winner will be the top priority
endorsed by the survey and that one usually
gets for sure built.
NASA for one, pays very close attention to
these priorities.
Last time it was WFIRST that won and it’s
being built now.
Before that it was JWST, and way back when,
Hubble won the blue ribbon.
So you can see that this event is a big deal
if you care about the direction and priority
of astronomy research.
So here we are at the end of 2019 and 2020
looms a couple of months away.
Now leading up to this moment, over the past
two years, I’ve held hangouts (twice!) with
four of the biggest contenders for the top
spot in the decadal survey and I’ve put
links in the description box if you want to
learn more, I’ve also made many shorter
videos on some of these as well.
The four biggest missions vying for attention
is: LUVIOR, HABEx, the Lynx X-Ray Telescope
and the Origins Space Telescope.
The first two LUVIOR and HABEx are especially
interesting because they are concerned with
looking for and characterizing habitable Earth-like
planets, they want to find out how many planets
like Earth are actually out there, not just
the one about the size of Earth, but ones
that are like Earth.
I don’t think anyone would be surprised
to learn that the question of life in the
universe is among our most important and astronomers
are slavering to get an answer to at least
some of these questions that we have only
begun to get some tantalizing answers for.
I mean, we now know there are other planets
around other stars in our galaxy and our kids
are the first generation to grow up knowing
this amazing fact.
But we need actual evidence that there are
not only other planets, but that some of these
planets are just like ours, with surface oceans
and atmospheres with carbon dioxide and maybe
even plants and animals.
These are burning issues that we’d all love
more evidence for.
Which brings me to the Carl Sagan Observatory,
or the Carl Sagan Space Telescope.
I was reading a very interesting white paper
written by some amazing people in the field:
Heidi Hammel from AURA, John Grunsfeld an
astronaut who repaired Hubble for the last
time, Ken Sembach Director of the Space Telescope
Science Institute and even Ann Druyan the
wife of Carl Sagan, and many others.
They were making the case that in order to
find other planets like ours, we need the
capability to directly image exoplanets around
other stars.
This telescope would be specially suited to
its task.
The Sagan Observatory would be a 12-meter
class space telescope, that’s 40 feet for
us Americans.
Here’s what it looks like compared to Hubble
and JWST.
As you can see, it’s a whopper, way bigger
than JWST.
The white paper went on to explain what else
this telescope would need: it would need to
provide reflected light spectroscopy of dozens
of planets around nearby stars.
This is measuring, not the light from the
star, but the reflected light of the star
from the planet!
As you can imagine, this is a tall order but
the spectra from this light will tell us whether
there is water there, in what form, whether
there are any biosignatures that would signal
plant life and what the compounds in the atmosphere
of the planet would be.
A 12-meter telescope will be large to enough
to enable direct imaging of planets in solar
systems like our own.
It would need some mechanism to block out
the light from the star, like a coronagraph
or a starshade to get higher contrast observations.
Using such a system, Hammel et al, estimates
that for the likely fraction of earth-like
planets in a habitable zone, say n sub earth
to be between 0.05 and 0.2, the Sagan Observatory
would have the capability to characterize
dozens of earth-like planets.
Here’s a simulated image of what the 12
meter optical component of the Sagan Observatory
would see around a nearby G star.
If this were our solar system the Sagan could
see Venus, Earth, Mars, Jupiter and Saturn.
Along with, and this is important, the spectra
of the reflected light from the planets themselves.
Here is an example of the resolution improvement
of a 12-meter class system compared to Hubble.
From this image you can see the limitations
of a 2.4 meter telescope and why all future
scopes are so big.
What matters now is providing observations
that answer some of the most pressing questions
in astronomy, is resolution.
So the white paper concludes with this: “We
assert that Astro2020” that’s the name
of the upcoming decadal survey, “should
endorse the idea of accomplishing the longstanding
decadal and scientifically-compelling goal
of finding the signature of life on another
world.
We also encourage Astro2020 to recognize that
to do so requires high resolution, high sensitivity
UV/Optical capability.”
They also propose putting it out to the L2
point where everything else is going these
days.
So as I was reading this, I kept thinking,
well just pick LUVIOR, why make the case for
a special telescope designed for this?
To review for those who didn’t watch my
hangouts on this, LUVIOR is a proposed 15
meter telescope, bigger than the Sagan Observatory,
and would be designed for use with a coronagraph,
a starshade or both but it is pretty flexible.
This would have more than enough resolution
and would include a high definition imager
that could image from the near-UV to the near-IR
with enough wavelength range to make the observations
required.
It also has a multi-object spectrograph and
a UV spectro-polarimeter so based on what
I know about LUVIOR, it’s a pretty good
bet it can make the observations advocated
by the authors of the Sagan Observatory white
paper.
HABex on the other hand is a much smaller
telescope, proposed to be between 4 and 8
meters but reading their final proposal it
looks like they settled on 4m, and it would
require both a coronagraph and a starshade
to work.
At that diameter, direct imaging of Earth-sized
planets would be a challenge but it does have
a spectrograph and an imager to make the observations.
So maybe these guys are trying to split the
difference and make a 12-meter space telescope
that can do most things LUVIOR can do but
more specialized towards characterizing Earth
like planets, I dunno.
Either way, I’d love to see this thing get
built.
I’m not sure what the final cost estimates
are for LUVIOR but this paper estimates that
the Sagan Observatory would be somewhere in
the Great Observatories cost range of 10 billion
dollars.
I know we’ve been here done that with JWST,
so it will no doubt cost more, a lot more.
But one thing I thought was interesting was
this quote supplied in the paper from Dennis
Overbye of the NY Times who was covering a
talk at the Hayden Planetarium about the Sagan
Observatory:
“I used to think $10 billion was a lot of
money before TARP, the Troubled Asset
Relief Program, the $700 billion bailout that
saved the banks in 2008...
Compared with this, the science budget is
chump change, lunch money at a
place like Goldman Sachs.
But if you think this is not a bargain, you
need look
only as far as your pocket...
...all that NASA money — whether for planetary
probes or space station trips —
is spent on Earth, on things that we like
to say we want more of: high technology, education,
a more skilled work force, jobs, pride in
American and human innovation, not to mention
greater cosmic awareness, a dose of perspective
on our situation here among the stars.
Even if we never discover even a single microbe
anywhere else, the money
spent on the search for life out there will
make life better for those of us stuck
here on Earth.”
I wish I had said that.
Anyway, what’s next is everybody just submitted
their final proposals and the National Academy
of Science with a final report with recommendations
and priorities listed will be made available
in late 2020.
Well that’s it for this episode Space Fans,
thanks to all Deep Astronomy Patreon Patrons
who every month contribute to these videos.
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Thanks to all of you for watching and as always,
Keep Looking Up!
