At this point, we’ve discovered lots of exoplanets that fall under the general label “Earth-like.” They’re rocky, and many orbit at distances from their host stars to potentially have moderate temperatures. But “like” is doing a lot of work there. In many cases, we have no idea whether they even have an atmosphere, and the greenhouse effect means that the atmosphere can have a huge impact on the planet’s temperature. So the Earth-like category can include dry, baking hellscapes like Venus with its massive atmosphere, as well as dry, frozen hellscapes with sparse atmospheres like Mars.

But we’re slowly getting the chance to image the atmospheres of rocky exoplanets. And today, researchers are releasing the results of turning the Webb Space Telescope on a rocky planet orbiting a nearby star, showing that the new hardware is so sensitive that it can detect the star blocking out light originating from the planet. The results suggest that the planet has very little atmosphere and is mostly radiating away heat from being baked by its nearby star.

The ultra-cool dwarf and its seven planets

TRAPPIST-1 is a small, reddish star—in astronomical terminology, it’s an “ultra-cool dwarf”—that’s about 40 light-years from Earth. While the star itself is pretty nondescript, it’s notable for having lots of planets, with seven in total having been identified so far. All of these are small, rocky bodies, much like the ones that occupy the inner portion of our Solar System. While the star itself emits very little light, the planets are all packed in closer to it than Mercury is to the Sun.

That leaves a number of them in what’s called the habitable zone, the area at which the heat delivered by the star could allow liquid water to exist on the planet’s surface. But that again depends on the properties of the planet’s atmosphere, should one exist. And there are reasons to think planets so close to a dwarf star might lack atmospheres. For the first billion years or so of a dwarf star’s existence, it’s prone to violent outbursts that could cook off any atmospheres that are not protected by strong magnetic fields.

There’s still a chance that geological processes could create a secondary atmosphere after the star settles down. But these atmospheres are likely to be rich in oxygen or carbon dioxide, with little in the way of hydrogen-containing molecules.

So, TRAPPIST-1 provides a fantastic opportunity—really, seven opportunities—to test some of our ideas about exoplanet atmospheres. And both the Hubble and Spitzer space telescopes have imaged some starlight that passes close to some of the planets as they pass between Earth and TRAPPIST-1. These observations didn’t provide any indications of an atmosphere, setting limits on how thick any gases above these planets could be.

But there’s a lot of uncertainty in those measurements. And the Webb Telescope, with its huge mirror and advanced imaging hardware, offers a new opportunity to take a second look at some of the TRAPPIST planets.

A little more than six months after the failure of its New Shepard rocket, Blue Origin has published a summary of the findings made by its accident investigation team.

For a private company flying a private launch system, the analysis of this “NS-23” mission is reasonably detailed. Essentially, the rocket’s main engine nozzle sustained temperatures that were higher than anticipated, leading to an explosion of the rocket.

The accident occurred at 1 minute and 4 seconds into a research flight that launched on September 12, 2022. The emergency escape system performed as intended, rapidly pulling the spacecraft away from the disintegrating rocket. Had a crew been on board this flight, they would have experienced a significant jolt and some high gravitational forces before landing safely in the West Texas desert.

Blue Origin led the investigation, with assistance from the Federal Aviation Administration and the National Transportation Safety Board. Investigators had a wealth of data to pore over, both from telemetry obtained during the flight and hardware recovered from the desert in West Texas.

From this information, the mishap team noted “hot streaks” on the nozzle and determined that it was operating at higher temperatures than it was designed for. Although the summary does not explicitly say so, it appears that at some point in the flight campaign of this booster, design changes were made that allowed for these hotter temperatures to be present.

“Blue Origin is implementing corrective actions, including design changes to the combustion chamber and operating parameters, which have reduced engine nozzle bulk and hot-streak temperatures,” the company stated.

The company says it intends to return to flight “soon” with an uncrewed flight to give the three dozen payloads that were flying on the NS-23 mission another shot at weightlessness. Previously, Blue Origin said that it plans to resume human flights on the suborbital space tourism spacecraft later in 2023.

The summary omits some key information. For example, the company has not precisely said what forces the spacecraft experienced during its emergency escape other than to say that humans on board would have survived the experience.

Additionally, it is not clear what rocket will be used to launch the return-to-flight mission. The company’s first New Shepard rocket, Booster 1, was lost during an April 2015 flight. Booster 2 was retired in October 2016 after performing a successful test of the launch escape system on its fifth and final flight. Booster 3, which launched the NS-23 mission in September, was the company’s oldest operational rocket, making its debut in December 2017.

The company has used its newest rocket, Booster 4, exclusively for human launches. It has some modifications from Booster 3 to qualify it as a human-rated rocket. The company has also built a fifth booster that may be ready for its debut flight. A company spokesperson told Ars that she could offer no information about the next flight beyond what was in the summary.

In 1960, visionary physicist Freeman Dyson proposed that an advanced alien civilization would someday quit fooling around with kindergarten-level stuff like wind turbines and nuclear reactors and finally go big, completely enclosing their home star to capture as much solar energy as they possibly could. They would then go on to use that enormous amount of energy to mine bitcoin, make funny videos on social media, delve into the deepest mysteries of the Universe, and enjoy the bounties of their energy-rich civilization.

But what if the alien civilization was… us? What if we decided to build a Dyson sphere around our sun? Could we do it? How much energy would it cost us to rearrange our solar system, and how long would it take to get our investment back? Before we put too much thought into whether humanity is capable of this amazing feat, even theoretically, we should decide if it’s worth the effort. Can we actually achieve a net gain in energy by building a Dyson sphere?

Spherical Dyson cows

I’ll state from the outset that I’m a theoretical cosmologist, not an engineer. I have absolutely no idea how to go about building a bridge, let alone a structure that reshapes the very face of our Solar System. But I’m willing to bet that nobody knows how to engage in these kinds of mega-engineering challenges. We can’t say for certain what kind of advances in which technologies would be necessary to build a structure that even partially encloses the sun. To speculate on that would be science fiction—fun, but not very meaty.

What I do know, though, is physics, and there are some things we can say about the physics of a Dyson sphere. We can use building one as a thought experiment to explore fundamental principles of energy, orbit, and motion. And this is important because no matter what technology-so-advanced-it’s-indistinguishable-from-magic our descendants come up with that allows them to rip apart planets, they still have to face the cold hard realities of our physics. They can’t get something for nothing. If they want to resculpt a planet, that takes energy. If they want to move a mountain-sized solar panel into a different orbit, that also takes energy.

For these and many other reasons, a Dyson sphere costs energy. So we’re going to see how long it will take to recoup the energy investment of building one and what the optimal design might be to minimize the initial investment.

To get at some numbers, we’re going to make a lot of assumptions. People like to poke fun at physicists for simplifying complex problems, sometimes beyond recognition. The old joke goes that dairy farmers reached out to a nearby university to help understand why milk production was low, and the response from the physicists began by assuming that the cows were spherical.

But there is something powerful about this simplifying approach, which is why physicists are trained in it from day one. First, it lets us answer questions when we’re not interested in precise numbers at the outset. Here, we just want a general sense of feasibility—will building a Dyson sphere take a (relatively) small, medium, or extreme amount of energy? Second, simplifying the problem helps cover up mistakes (either in calculations or our starting assumptions). If all we’re going after is a general ballpark, then a factor-of-two mistake (or even 10 or 100) won’t really change the overall intuitions our calculations enable.

Lastly, we literally don’t know how to build a Dyson sphere, so trying to go for anything more complex will simply lead to us introducing many more assumptions to handle all the small details. Each of those assumptions will increase the uncertainty of any numbers we produce, and that uncertainty will probably end up buried in the analysis rather than handily stated upfront.