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The Astrophysics Pioneers program is funding four innovative new missions that read like a best-hits album of the most exciting astronomical frontiers: from galaxy evolution and exoplanets, to neutron star mergers and astroparticle physics.

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[♪ INTRO].

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 [♪ OUTRO].