It really is kind of a mad scientist atmosphere when you’re essentially blowing things up, and it’s all legal. It’s like Dr. Frankenstein came back to life. He would be running a lab like this. If he could really bring things back to life with intense energy, this would be the place. Astrophysicist Mike Montgomery is talking about the Z Machine — one of the most powerful devices on Earth, capable of firing more than 20 MEGAJOULES of energy at a tiny target at its center.
It’s used to uncover some of the greatest mysteries of our universe. So there’s an enormous release of energy. And in just a few nanoseconds, you release more energy than five times all the power plants on the Earth. It’s an incredible powerful thing, it’s the most powerful X-ray source on planet Earth by a lot. When it goes off, there’s a nenormous boom. You feel it move through you, the doors vibrate, the ground shakes.
The Z Machine is helping drive innovation in the fields of radiation sciences, material sciences, and fusion studies. Even redefining the field of astronomy by making experimentation possible. We can actually create the cosmic conditions in the laboratory. Now we can turn astronomy into an experimental science like physics or any other science.
Always before we say, well it’s an observational science. And we go out to McDonald Observatory. But now we go to Sandia National Labs and do these experiments and create those conditions. Don Winget and Mike Montgomery from the University of Texas at Austin are here to fire the Z and create conditions similar to the interior of a star. The stakes are very high — because, the Z shots are very precious. There’s one a day at Sandia, basically, atmost.
So you only get a very precious handful of shots. If you’re the white dwarf experiment, you may only get something like 15 of these shots a year — if you’re lucky. You realize you’re using something very few people are privileged to be able to use to do something that’s very rare and very special. You don’t want to lose one because you didn’t hook up a cable correctly. Or because something wasn’t aligned perfectly. And you don’t want to lose a shot because a leak is making it impossible to create a vacuum in the experiment chamber.
Unfortunately, this is the scenario Mike, Don, and the Z Team currently face. More than 16 hours have passed since yesterday’s scheduled shot and technicians have finally located the leak. They work quickly and carefully to seal it. The care that has to be taken with the entire operation at Z is a little like the US Space program. In the space program they’re doing hard things, and they’re doing hard things that can’t go wrong.
It gives you a tremendous amount of respect for the team that does it, you realize that this is a very special operation and that they’re highly skilled, and it’s an amazing instrument. And so I’m delighted to be able to take part in an actual laboratory experiment, which I didn’t really think was going to happen in my astronomy career. Mike and Don have spent decades observing and studying white dwarf stars.
Now, they’ll get the chance to recreate one on Earth. As we look at our Milky Way we look at say, a couple hundred billion stars. Most of those stars, about 97% plus, almost98% we think will become white dwarf stars. White dwarfs are the burnt out cores of red giant stars — but I hate describing them that way. White dwarfs are the natural endpoint for most stars. Once they become a white dwarf they’re fossil remnants of stars.
They’re finally a stable form. And because white dwarfs are typically the oldest celestial bodies in their star systems, they’ve been used as reliable time keepers of the cosmos. An age is one of the hardest things to determine. You can’t measure an age. It’s a derived quantity. You can measure how bright something is or how far away it is, but without a model for how that object changes with time, you cannot measure an age. To break this down further — we can measure a star’s brightness using powerful telescopes.
These powerful telescopes record visible spectra that provide clues about a star’s composition and temperature. Each element has a fingerprint that’s unique to that element, and so that tells you what elements are present. So you break the light apart into its colors and you look for the signature of these elements, and the relative strengths of the various lines that you see contains information about the temperature. Visible spectra can also be used to determine a star’s mass.
All this information can be used to create cooling models to determine a star’s age. You’ve got a block of iron, and you’ve been heating it in the fire up to 800 or 1,000 degrees, and you take it out, and you measure its temperature versus time, it just gets cooler and cooler. It’s not that hard to calculate how fast its would get cooler and cooler either. So, with the white dwarf, it’s the same thing. Astrophysicists like Mike and Don can then use the oldest white dwarfs to estimate the age of other celestial bodies, galaxies, and even the universe itself.
The research that Don did back in the late’80s showed that you could use these coolest white dwarfs to figure out how old the disk of our galaxy is. Don’s groundbreaking work not only resulted in recalibrating the age of the Milky Way — but also resulted in adjusting the estimated age of our universe from roughly 20 billion years to 13 billion years. But what if those models used to determine the age of white dwarfs still aren’t quite right? We knew that there was physics yet to be understood in the white dwarf spectra.
So we’ve started to realize we’re having systematic problems with that, so that the spectroscopic values of the mass that we’re deriving may have systematic problems of 10% errors in mass. It could be larger. For those who haven’t yet done the math– a 10% error on 13 BILLION means the current estimated age of the universe could be off by MORE THAN A BILLION YEARS! And that’s why we’re now trying to do experiments on Earth which will nail down these problems. With the leak sealed and the Experiment Chamber pumped down to create the necessary vacuum, all systems are go for fire.
Here we go! With this shot, the Z Machine will recreate the conditions of the interior of a star allowing researchers to examine the properties of plasma x-rays and investigate how hydrogen atoms absorb light. Unfortunately, due to safety protocol, our cameras aren’t allowed beyond these doors. Charge complete. Ready to fire. Yeahhh! I saw a flash! In astronomy, we wait for the universe to make the experiment and then we look at the results, but we can’t ask nature to repeat the experiment.
Almost every one of you guys jumped! We did not jump. We reacted. Now we have a real laboratory so it just leverage show much more information we can get from astrophysical objects if we can calibrate the models that we’re using to interpret them. Now the rest of the data will come out; it’ll percolate out over the course of the next 24 hours, but now we know that the experiment was successful. And that’s the whole idea, benchmarking the observations and the theory, benchmarking the theory that’s used to create the models through which we interpret the observations.
Astronomy is great and it has all these pretty pictures, but it’s really understanding the pretty pictures, that’s the fun part.