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Whether it’s boots on the Moon, robots on Mars, or telescopes in space,
when NASA sets its sights on something, it can make scientific miracles happen.
But miracles don’t come cheap, and NASA missions on those scales
cost billions of dollars, and take years or decades to execute.
So in 2020, NASA decided to try something different.
They put out a call for proposals for innovative new missions with much smaller budgets,
capped at 20 million dollars, which sounds like a lot,
but is less than one percent of the budget for the Perseverance rover, for example.
Smaller costs also come with lower stakes, and the opportunity to give scientists
earlier in their careers a chance to lead groundbreaking missions.
NASA called the idea the Astrophysics Pioneers program,
and in January 2021, they announced four missions that had won funding from it.
These missions read like a best-hits album of the most exciting astronomical frontiers.
They have it all: from galaxy evolution and exoplanets,
to neutron star mergers and astroparticle physics.
So learning the science behind these missions can teach us a lot
about the biggest burning questions in astrophysics.
Three of the four missions are SmallSats.
These are small spacecraft that can be used as test platforms
to demonstrate new technologies and capabilities for a fraction of the cost.
They’re also small enough to be launched as secondary payloads on larger missions.
The first of these is a space telescope called Aspera, and it will do something
almost no other telescope is currently doing: It will look at ultraviolet light.
Much of UV light is strongly absorbed by Earth’s atmosphere,
which is great for preventing skin cancer, and not so awesome for astronomy.
So ultraviolet telescopes are usually placed in space,
where our atmosphere doesn’t get in the way.
But right now, the only active space telescope
that can see in the UV spectrum is the big one: Hubble.
And that’s kind of a pain, because there are plenty of things
that primarily emit or absorb UV light, like certain gases.
And with everything else it can do, research time on the Hubble is limited.
So, that’s where Aspera comes in.
It’s designed to directly detect the diffuse gases
that surround and permeate galaxies, called the circumgalactic medium.
We haven’t been able to accurately measure the medium yet,
so we only have theoretical models of how big a role these gases play.
But scientists hypothesize that for many galaxies,
this medium makes up a big chunk of their mass; maybe more than half.
These gases also play a large role in the formation and growth of galaxies.
They constantly flow into and out of them and provide fuel for star formation.
So understanding them can help scientists better piece together the story
of what galaxies are like, and how they form and change.
The trouble is, some of these gases can be notoriously difficult to detect.
But they are thought to emit some UV light, making them ideal targets for Aspera.
And there’s more.
The circumgalactic medium is only part of the story, because Aspera
is also designed to study the material between galaxies, or the intergalactic medium.
Astronomers think a large amount of the universe’s matter exists between galaxies,
in incredibly sparse filaments that form a kind of cosmic web.
And like how the circumgalactic medium affects the evolution of galaxies,
researchers think understanding the intergalactic medium
can help them get a handle on how the whole universe has evolved.
Since this medium might also emit light in the ultraviolet,
scientists hope that Aspera can help detect it, too.
The mission is being led by the University of Arizona,
and if all goes well, it’s expected to launch in 2024 and fly for about two years.
So we won’t have to wait long to find out more.
The next Pioneers mission is an exoplanet hunter:
a 45-centimeter SmallSat telescope called Pandora,
led by a researcher at NASA’s Goddard Space Flight Center.
Over the last couple of decades,
thanks to advances in technology around the world and in space,
astronomers have discovered thousands of planets outside our solar system, or exoplanets.
And when Pandora launches in late 2024 or early 2025,
it’ll add a powerful tool to astronomer’s exoplanet-hunting toolbelt.
But Pandora’s job won’t be to discover new planets.
Instead, it’ll study 20 known stars and their 39 known exoplanets in detail.
Pandora will discover things like whether the exoplanets have water on them,
and whether their atmospheres have clouds.
And it’ll do all that using a tried-and-tested method in exoplanet research:
exoplanet transmission spectroscopy.
When an exoplanet passes between its host star and us, or transits,
it blocks some of the light coming from the star.
But it doesn’t necessarily block all wavelengths of light the same amount.
For instance, if a planet with an atmosphere transits,
some wavelengths will get filtered by that atmosphere more than others,
just like how Earth’s atmosphere blocks UV light from the Sun.
The kinds of light an atmosphere absorbs depends on its chemical composition,
so ultimately, scientists can use this method to track down
what an atmosphere is made of, and also what its star is like.
One complication, though, is that stars can vary in brightness naturally.
Our own Sun does this, too: It’s a dynamic place with sunspots and flare-ups.
Pandora combats this issue with a unique approach: using not one, but two detectors.
One detector is designed to look for the telltale signs of water in a planet’s atmosphere,
while the other is tasked with monitoring the variation in the host star’s brightness.
By combining the data from the two detectors,
the team can infer how much water is in the exoplanets’ atmospheres,
without worrying about the star’s natural variations messing things up.
Also, Pandora will be able to gather lots of data on the stellar variations themselves,
something that will likely help other exoplanet-hunting teams for years to come.
The last of the SmallSat missions is StarBurst, led by NASA’s Marshall Space Flight Center.
It’s an instrument payload designed to detect high-energy gamma rays
from dramatic cosmic events like neutron star collisions.
Neutron stars are the small, dense remnants of dying stars,
and their collisions are among the most violent events out there.
It’s thought that a lot of heavy elements, like gold and silver,
are mainly forged in events like these, so learning more about them
is crucial to understanding the overall history of the universe.
And detecting these gamma ray bursts
is also important for the new field of gravitational wave astronomy.
In 2017, scientists detected a neutron star merger by seeing its gravitational waves,
ripples it made in the fabric of spacetime itself.
But what was extra cool was that at the same time,
other researchers detected light from the same collision.
Having two independent indicators of the same event helped astronomers
to triangulate the collision, working out where in the universe it happened.
These teams also detected lots of different kinds of light coming from the collision,
including a burst of gamma rays.
And that was a big deal, because astronomers had long wondered
about the source of gamma-ray bursts, sometimes called GRBs.
So, researchers can now say that at least some come from neutron star collisions.
Since then, though, no one has seen any more of this kind of multi-messenger event:
events where scientists can detect and observe a phenomena
using more than one technique at a time.
StarBurst aims to change that, while also helping researchers
learn loads of fundamental physics and cosmology.
Right now, there are quite a few GRB-detecting instruments in space,
and together, they see roughly one burst each day somewhere in the universe.
But the existing detectors don’t cover the whole sky,
and some events are too faint to detect with our current instrumentation,
so some events are still getting missed.
And that’s where StarBurst might help.
If mission development and testing go well, it’ll launch around 2024 or 2025.
And hopefully, it’ll be able to detect about ten GRBs each year
that otherwise would’ve gone unnoticed.
That will give astronomers more chances to potentially
see gamma rays and gravitational waves coming from the same source.
And that means more chances to learn about these incredible, dramatic events.
The last of the Pioneers missions is quite a bit different from the others,
but it also has a lot to say about incredibly violent cosmic events.
It’s called PUEO, and it’s led by the University of Chicago.
It’ll detect particles from a variety of sources,
ones generally lumped into the category of “cosmic rays.”
And it’ll look for these particles in an unusual place: the Antarctic ice sheet.
Oh, and another big difference? It’s not a satellite, it’s a balloon.
PUEO is a follow-up to a 2006 NASA experiment.
That study launched a helium balloon in Antarctica
carrying a small, uncrewed antenna array called ANITA.
The balloon reached an altitude of around 40 kilometers
and drifted around Antarctica for 35 days gathering data.
And three further flights over the next decade did something similar.
ANITA was looking for ultra-high energy neutrinos:
tiny, subatomic particles that can
pass through anything in the universe almost entirely undisturbed.
And it did that by staring at Antarctic ice sheets.
See, when neutrinos collide with the atoms of other materials,
each interaction produces a distinct radio signal.
And ice is a radio transparent medium,
meaning it allows radio waves to pass through it without really disturbing them.
So, watching ice is a great way to observe neutrino interactions.
That said, not every neutrino will collide with an atom in a material,
so you also need a huge detection area.
And the radio signals produced by these interactions are also very faint,
so you need a fairly radio-quiet area without a lot of interference from other signals.
And that makes the big, quiet expanse of Antarctica a good place to look.
From above, ANITA could pick up neutrino signals
coming from the 1.5 million cubic kilometers of ice within its horizon.
Still, it only detected a couple dozen ultra-high energy neutrinos and, even then,
there’s still some uncertainty over what kinds of neutrinos they actually were.
So, PUEO will hopefully improve on its predecessor.
If building and testing go well, it’ll launch in 2024, will be more sensitive,
and will have the ability to detect a wider range of signals.
Most of the neutrinos it detects will likely have come from
cosmic collisions and explosions, like the gamma-ray bursts StarBurst will look at.
And since neutrinos are the only particles
that can travel billions of light-years with this much energy,
researchers will be able to learn a lot about the kinds of physics that happen there.
When NASA put out a call for proposals for the Pioneers program,
they weren’t sure whether it was possible
to do really great astrophysics at a fraction of the usual cost.
But the scientific community delivered these innovative ideas, and now,
the four early-career researchers who lead these projects will get to show what they can do.
Before you go, I wanted to give you a heads-up that
your last opportunity to get the SciShow Space Pin of the Month is coming up!
Every month, we release a new space-related pin,
and the one for March is a dark matter star.
They’re hypothetical, but some researchers have ideas about what they might look like.
We talked about them in a recent episode, which you can watch any time.
But you can only get the pin until the end of the month.
After that, we’ll have a new design in April.
If you want to learn more, head over to DFTBA.com/SciShow.
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