The Week in Space and Physics: Farewell to the Ariane 5
The Week in Space and Physics: Farewell to the Ariane 5
On the Ariane 5 and a European rocket crisis, slow clocks in the early universe, long ago supernova and the roundness of the electron.
Flawless was the term NASA later used to describe the launch. When the Ariane 5 rocket lifted off on Christmas Day of 2021, it did so with extraordinary precision. The rocket not only sent the James Webb Space Telescope hurtling into space, it did so with such accuracy that the telescope needed far less fuel than expected to reach its destination. That, operators later confirmed, will extend the life of the telescope by a decade, pushing its useful lifespan well into the 2030s.
That flight was perhaps the crowning achievement of the Ariane 5. Yet it also launched over one hundred other missions. Among them were JUICE, an orbiter now heading to Jupiter, BepiColombo, a Mercury explorer, and Rosetta, a probe that visited in a comet in 2014. It did all this almost without fault, suffering only two clear failures during its twenty-seven year lifespan.
Last Wednesday, however, the Ariane 5 took flight for the final time. The rocket, carrying German and French satellites, lifted-off from its usual Caribbean launch pad in Kourou. Soon after it once again reached space, delivered its cargo into orbit and fell back to Earth.
Arianespace, the company behind the Ariane rocket, and ESA, the European space agency, have been planning to replace the rocket with a more advanced and cheaper version, known as the Ariane 6. Under original plans, that rocket should be flying by now, thus removing the need for the Ariane 5.
Yet technical problems have delayed the maiden flight of that rocket. When it will actually fly is unclear. When development started, engineers were targeting a launch in 2019. That has now slipped to the end of 2023, though unofficial reports suggest it will not happen until sometime in 2024.
As production of the Ariane 5 has ceased, that delay now leaves Europe without an independent launch option of its own. In the past Europe and ESA might have turned to Russia for help - several European missions have historically launched on the Soyuz rocket. The war in Ukraine, however, has put an end to the possibility. Short of other options, ESA has instead turned to SpaceX to launch its missions, including the recent Euclid space telescope.
That, as ESA chief Josef Aschbacher puts it, represents somewhat of a launch crisis for Europe. Fortunately, the continent seems to be taking active steps to address it. Arianespace is no doubt under pressure to deliver soon, but Europe is also supporting a set of rocketry startups. Several are now developing rockets, and have received plenty of money to help them to so.
Europe will probably feel the shortage of rockets over the next year or so. But in time these investments will hopefully bear fruit. Within a few years, if things go to plan, Europe could be home to several thriving rocket companies. That would give them no shortage of options for launching probes and satellites into space.
Slow Clocks in Distant Quasars
Light, Einstein postulated, always has the same speed, no matter how you look at it. The repercussions of this simple statement turned out to be profound. From it, Einstein was able to unlock the secrets of relativity and gravity, thereby reshaping our view of time, space and the cosmos itself.
As a result, physicists now know that time is malleable. Observers moving at speeds close to that of light will see stationary clocks running slow and find, when they reach their destination, that more time has passed than they experienced. Gravity can distort time as well, with heavy objects like black holes altering the flow of time for those who pass close by.
The same effect, cosmologists have long thought, should be present in the early universe. Since light has a fixed speed, the more distant an object is the longer its light has taken to reach us. Yet cosmologists also know the universe is expanding, which implies this light has been “stretched” on its voyage towards this. That stretching should alter the way we see time flowing in distant objects, making far away clocks appear to run slow.
That light is indeed stretched by the expanding universe has been confirmed on many occasions. Yet proving that time seems to run more slowly in the ancient cosmos has been harder to do. Some evidence emerged in 2008, when surveys of distant supernovae showed the expected effects. Yet observations of other distant objects failed to show time running slowly.
Now, however, researchers have spotted the effect in quasars, a kind of energetic galaxy. By examining measurements of more than a hundred quasars taken over two decades, a pair of astronomers in New Zealand and Australia confirmed that time really does run more slowly the further back you look.
For some of the oldest objects, appearing as they did a billion years after the Big Bang, time passes at roughly a fifth of the rate that it does here on Earth. Of course, that is relative - anyone in those quasars would experience time passing at a normal rate. It is only from our viewpoint that their clocks appear to run slow - a consequence, and another proof, of Einstein’s relativity and the expansion of the universe.
Did a Supernova Shake the Early Solar System?
Little is known for sure about the origins of our solar system. Most likely it formed in a molecular cloud, as is typical of stars like our Sun. Yet where that cloud was, or which other stars formed along with the Sun, is unknown.
A recent study, however, hints that the infant Sun survived a close brush with a nearby supernova explosion. Traces of radioactive elements found in meteorites might, they say, have come from such an event long ago. If so, however, the solar system would also have been buffeted by a shock wave. That, given how close the supernova would have been, should have ripped the solar system apart.
To explain how it survived, the researchers revisited models of how stars form within molecular clouds. Inside these clouds, we now think, stars form along filaments of gas, with massive stars forming where the filaments cross. Those big stars tend not to live long, and so are prime candidates for supernova eruptions.
Crucially, however, the filaments also provide protection against those supernovae. The study showed that the filament around our Sun could have survived for hundreds of thousands of years, even as shockwaves from the dying star swept across it. That would have saved the solar system, while also enriching it with the heavy elements generated in the heat of the supernova.
How Round is an Electron?
In the hunt for new physics, researchers are making ever more precise measurements of fundamental parameters. The most recent target was the electric dipole moment of the electron, a number that in some ways measures the “roundness” of the particle.
Some theories suggest that a slight non-roundness in the electron could explain why the universe is made of matter and not antimatter. The known laws of physics treat matter and antimatter more or less identically. We also believe that they were created in equal amounts in the Big Bang. Somehow, however, most of the antimatter has since vanished, leaving a surplus of matter.
If the electron turned out to be slightly non-round, then that could point to the existence of new particles exerting subtle influences on it. Yet new measurements of the electron, carried out in the United States, show no evidence that the electron is not perfectly round. No luck yet, then, in the search for the missing antimatter.