The Week in Space and Physics
On the Hycean planets, the birth of supermassive black holes, Musk's turn at private spaceflight and China's ambitions in space
In many ways, the history of science is a history of our own arrogance and delusion. Centuries ago the wisest men - the scholars and priests - placed the Earth, and therefore mankind, at the centre of creation. We were a chosen species, occupying a special place in the universe.
Over time science has stripped that deceit away. Humanity gradually lost its self-important place in the universe; the Earth was demoted to nothing more than a small rock around an average star. But one last claim to glory remains: Earth is the only place in the known universe to support life and, by extension, civilization.
Scientists have long put that down to a magical combination of carbon, oxygen and water, the three ingredients considered essential for life. When we peer across the cosmos at distant planets it is those chemicals we look for; it is their absence that dooms a world to an eternal death.
That betrays a lack of imagination. The thousands of planets we have discovered come in staggering variety. Some, bigger than Jupiter, boil close to their stars. Others, smaller than Mercury, freeze in the depths of space, coming alive only briefly as they swing by their stars. Few are like Earth.
Many of those worlds are clearly inhospitable. Life cannot exist in a superheated atmosphere or on a planet frozen to its core. But between these two extremes lie an immense variety of options. Only now are astronomers starting to grasp the implications they offer for life beyond Earth.
One such option, reported in a paper from Cambridge University, are the so called Hycean planets. At first glance these worlds do appear intensely alien and hostile to any life from Earth. They are larger than Earth – perhaps three or four times bigger – and host vast oceans. Instead of the kind of atmosphere we typically associate with life – warm and oxygen filled – these planets are hot and blanketed in a thick layer of hydrogen.
That heat would normally rule out prospects for life. But astronomers now think the oceans could be cool enough for micro-organisms to thrive. How temperate those oceans might be depends both on the size of the planet’s sun - small stars tend to be colder - and how far away the planet orbits. But the researchers believe the range of viable combinations is surprisingly high.
Since such Hycean worlds are thought to be common, that range of possibilities hints that many habitable worlds might be out there. The team of researchers suggest a list of nearby planets - within 150 light years of Earth - that match their criteria, and suggest follow up studies.
Upcoming telescopes, especially the James Webb Space Telescope, could examine potential Hyceans. Scientists would be especially interested in examining their atmospheres. If traces of certain gases, perhaps methyl chloride or dimethyl sulfide, are found, that would be an exciting sign of possible life.
Either way, the research shows that the possibilities for life in our galaxy are far more varied than astronomers had earlier thought. Planets come in many bizarre forms. Life should too.
How the Giants Were Born
The heart of our galaxy hosts a monster: a black hole four million times bigger than our Sun. That sounds impressive, true, but compared to some of our neighbours that monster looks positively puny. Andromeda - the nearest big galaxy - is home to a black hole fifty times bigger. The giant in Messier 87 - the first black hole photographed from Earth - is perhaps thirty times bigger again.
Astronomers have long questioned how such enormous black holes formed. A typical black hole is created in the dying moments of a giant star, though these are often just a few dozen times bigger than the Sun. Given enough time they can grow, perhaps, some have reasoned, reaching supermassive status after gorging on stars and dust for a few billion years.
But some observations contradict this idea. Two distant black holes seem to have reached enormous sizes while the universe was still young - just a few hundred million years old. It seems unlikely that a small black hole could really have grown fast enough to explain their presence.
Instead, some astronomers think giant black holes emerged in the strange conditions prevailing at the dawn of time. Back then the universe was mostly made up of two things: hydrogen atoms and the mysterious dark matter. Some models wonder if that dark matter somehow played a role - if it had gathered in large enough halos, it may have collapsed into a black hole.
Alternatively, both hydrogen atoms and dark matter could have collected to form strange quasi-stars, supermassive objects that dwarf even the largest stars around today. Such objects could not have survived long. Their cores, growing denser and denser, would inevitably collapse into a small black hole. The rest of the star would soon have followed.
The result would have been a black hole bigger than any that could form today. As the universe evolved, many of those black holes likely found themselves at the centre of coalescing galaxies. Over time they would have grown larger, fed by a rich diet of stars and gas. Some, as galaxies collide, would have merged, growing even bigger - until they reached supermassive sizes.
Others may have been cast aside, doomed to wander the outer fringes of galaxies. Dozens may lurk there, almost invisibly, according to one recent study. If models of galaxy dynamics are correct, galactic collisions should sometimes displace a black hole from the centre of a galaxy. Such black holes would be hard to detect, though traces of devastated stars or sudden flares may reveal their presence.
Inspiration4 Gets Ready for Launch
Jeff Bezos and Richard Branson may have captured the world’s attention with their two short journeys to space, but both will soon be upstaged by Elon Musk. In a launch scheduled for September 15, SpaceX will put the first entirely private crew of astronauts into orbit.
The mission, named Inspiration4, is funded by Jared Isaacman, an American billionaire aged just 38. Isaacman will be joined by three crew members: Sian Proctor, Hayley Arceneaux and Christopher Sembroski. For each this will be their first experience in space. That makes this the first orbital flight in four decades with no experienced astronauts onboard.
The crew will fly on SpaceX’s Dragon 2 capsule, the vehicle that the company also uses to fly astronauts to the International Space Station. Indeed, the particular capsule in question, named Resilience, has already been to the space station. In November last year it carried a team of four NASA astronauts, and only returned to Earth in May.
The Inspiration4 crew will not head to the space station, or anywhere else in fact. The capsule will spend three days orbiting the Earth, before re-entering and splashing down in the Atlantic Ocean. A blitz of media coverage is certain to surround the mission. Netflix have already announced a documentary and the crew are planning to perform songs and teach art lessons from orbit.
In many ways, however, this flight will represent a milestone in private spaceflight; one more significant than either Bezos or Branson achieved earlier this year. For the first time in history, a crew of amateur astronauts will be carried into orbit with no involvement of a national government. That will certainly be something to write home about.
China Dreams Big
The American space program has often seemed indecisive. NASA’s goals tend to be re-orientated every four or eight years as each new president seeks to imprint their own ideas on the agency. China, by contrast, seems to be developing a long-term plan for the conquest of space.
Though details of that plan are sometimes hard to divine, the country appears to have ambitious ideas for exploring both the Moon and Mars. China is already developing spacecraft and landers for a crewed Moon mission - which seems likely to happen sometime in the 2030s.
China also seems interested in building massive structures in space. A recent report suggests the country is investigating ways to construct objects a kilometre long or more. That’s roughly ten times bigger than the International Space Station.
Such enormous platforms would permit new ways of using space. One area China seems interested in is orbital solar farms - giant arrays of solar panels that beam back energy to Earth. But China may also be interested in building vast space stations for research and even security (dare we say military?) purposes.
A third area of interest lies in satellite mega-constellations, like the Starlink constellation SpaceX are currently deploying. China last week launched two demonstration satellites intended as precursors to a larger constellation of thousands of communication satellites.
Filings with the International Telecommunications Union indicate China is planning to launch up to 13,000 satellites - a thousand more than SpaceX currently has permission for. Though SpaceX currently have the lead in actual satellites in orbit, China seems keen to catch up soon.
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