The Week in Space and Physics
Black holes, life beyond Earth, expanding the International Space Station and the race for quantum technology.
From a safe distance - fifty-three million light years, to be precise - it looks like nothing special. A fuzzy orange halo, a small dark spot, invisible to all but the most powerful telescopes. But this is a black hole, and a big one at that, one of the most terrifying and mysterious objects in the Universe. So big that no ray of light can ever escape, so dense that they bring an end to time itself.
Despite its frightening size, it was surprisingly hard to photograph. Black holes emit no light, almost by definition, which rules out the usual routes astronomers use to catch a glimpse of distant objects. Instead they looked to the surroundings of the black hole, hoping they would give a hint to the presence of one of the deepest voids in creation.
Anything that gets too close to a black hole - be it a star, planet, or an unfortunate astronaut - will be ripped apart by intense gravitational forces. The resulting debris tends to stick around for a while, before either falling into the black hole or getting flung out at tremendous speed.
Two years ago, when astronomers tried imaging a black hole for the first time, they chose M87*, one of the biggest visible from Earth. It was, as astronomers had hoped, surrounded by a glowing disk of debris - the fuzzy orange ring in the photo. In the centre was a dark spot: the shadow of the black hole, exactly as predicted by Einstein’s equations.
The image was a triumph; an outstanding opening move for the telescope that captured it, the Event Horizon Telescope. Now researchers have directed its gaze elsewhere, revealing the secrets of a second black hole in a nearby galaxy.
That is the powerful black hole at the centre of Centaurus A, one of the most beautiful galaxies in the night sky. Millions of years ago that galaxy collided with another. When it did, the sudden inflow of material created a wave of star birth that is still ongoing.
That collision also disturbed the central black hole, awakening it from a long slumber. As it roared to life, it fed upon the clouds of gas and dust pouring into the galaxy, spitting out two long streams of matter on either side of the galaxy.
Exactly how these streams are formed has long puzzled astronomers, making it an inviting target for the EHT. So far the results, which include a detailed image of the black hole, have revealed some surprises. That could mean we need to revise our theories of exactly what happens in the extreme environment around black holes.
Astronomer’s next target for the EHT could give them a better idea of how to do that. At the heart of our own galaxy, twenty-five thousand light years away, lies another supermassive black hole: Sagittarius A*. This is the biggest and most powerful black hole in our galaxy, but one we have so far never directly seen. The EHT promises to offer a staggering first glimpse of this beast in our own back yard.
The hunt for life beyond Earth is one of the biggest quests in science. Researchers have stumbled across some tantalising hints - on both Mars and Venus - but no definite proof has ever been found. Part of the problem lies in working out what exactly a proof looks like. Short of spotting something that moves and talks, researchers must look for chemical evidence of its presence.
So far that has focused on gases like methane and phosphine. These normally break down rapidly, so their presence in an alien atmosphere means something must be creating them. That can be biology - creatures on Earth give out both gases - but it can also be geological, as volcanoes or other natural processes can produce them.
The trouble is distinguishing these two causes. Mars may be the best studied planet beyond Earth, but we still don’t understand its geology well enough to rule out geological causes for such signs. On other less studied worlds - Venus, or the moons of Jupiter - scientists are often making little more than educated guesses.
Now, though, a team of researchers has proposed looking for wider signs of active biology on a planet. Instead of looking for specific chemicals, the team suggests looking at the proportions of elements found in samples. Those proportions seem to follow certain patterns on Earth, whenever life is present, and the same should be true on other worlds.
To get an idea of where we should focus our efforts, biologists on Earth often study extremophiles - life forms that thrive in extreme places. There seems to be no shortage of such beings: life has been discovered in nearly every environment on Earth, no matter how harsh. That has often been taken as a good sign for the possibility of life on other worlds.
Now, for the first time, researchers have found a sample of soil that appears to be completely sterile. The sample was collected near the Shackleton Glacier in Antarctica, which is one of the coldest and driest places on Earth. Could this discovery finally place a limit on what life can handle?
Understandably, the researchers were cautious in their conclusion. Ruling out the presence of life is hard, and it is possible something was living there that our techniques can’t detect. Even if there was, the fact that so little life was present is an intriguing discovery.
For the first time in years, the International Space Station is to be expanded. Construction of the station was completed in 2011, with the addition of the final Leonardo module during one of the last shuttle flights. Apart from an experimental commercial module added in 2016, the structure has changed little since then.
Now the Russians have launched a new module, Nauka. It will provide an extra seventy cubic meters of space, a new robotic arm, and new water and oxygen generating systems.
The module has a long and convoluted history. First built as a backup in case of a problem with Zarya, the first module of the ISS, it was later repurposed as a science laboratory. Sometime during that redesign an extra robotic arm, created in partnership with the European Space Agency, was added.
At the time, launch was expected by 2007, but delays pushed that back until 2012. Then disaster struck - tests revealed serious issues with the propulsion system. Years of work followed as engineers tried to fix the issues before deciding to replace it altogether.
By 2020 the module finally seemed ready for launch - until the coronavirus pandemic struck and delayed things even more. The long, sorry saga seemed to come to an end last week, when the module finally took flight and started heading to the space station.
Unfortunately things still have not gone to plan. Problems with computer systems caused the module to miss the first planned orbital changes, raising fears that it might burn up in the atmosphere. Fortunately backup engines did work, and mission controllers were able to raise the orbit.
Several problems still remain. Reports have circulated that antennas and docking units have failed to deploy as expected. That could threaten the ability of the module to dock at the space station. After so many problems and delays, you could be forgiven for wondering if the module is somehow cursed.
The future is quantum, probably. Several technologies stand to be revolutionised by quantum theory, especially communications, security and computing. But will this be the first technological revolution in decades to take off outside America?
The Chinese government is investing heavily in quantum research, and they seem to be pulling ahead in some areas. They have already proven an edge in quantum encryption, sending quantum keys across continents back in 2017. Now, according to an analysis by Scientific American, they may be advancing faster in quantum computing too.
A series of papers show that China has built a computer roughly equal in power to one built by Google in 2019. That places them as a serious competitor for quantum superiority, and may, with their more advanced quantum networks, put them in the lead.
The two countries are following different paths in developing the technology. China, naturally, focuses on government funded research. America, by contrast, is more mixed, with private companies like Google and IBM leading much of the work.
Two papers this week show that America is not out of the running just yet. One, published by Google, suggests that the company is close to reducing the effect of random quantum noise on their computers. That should make it easier to build more powerful computers, which have so far suffered greatly from this noise.
The other, from Harvard University, announced a 256 qubit quantum simulator, the largest ever built. While this is not a full quantum computer, it does use techniques that could help build larger computers than we currently have.
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