The Week in Space and Physics #16
The Week in Space and Physics #16
On the Great Dimming of Betelgeuse, extreme exoplanets, Voyager I and Europe's new rockets
The giant star Betelgeuse has long fascinated the inhabitants of our planet. The ancients saw fire and war in its deep red image; its flickering gaze was associated with great predators hunting amongst the heavens. Today the star forms a prominent part of Orion, the Hunter, easily visible on even the brightest of nights.
Yet Betelgeuse is dying. The red colour comes from its cool outer layers. Its inner core now burns helium rather than hydrogen: a step that brings it closer to an inevitable doom. Quite when that end will happen is unknown: in astronomical terms it should be soon; in human terms it may not be for a hundred millennia or more.
Whenever it happens, it promises to be dramatic. Betelgeuse will detonate in a violent supernova; one bright enough to light up the night sky for weeks on end. That possibility has often led to media speculation. When the star unexpectedly dimmed in 2019, the event sparked sensational headlines predicting an imminent supernova.
That, of course, never came to pass. The star eventually brightened again, and now appears much as it has for millennia past. Yet the reason for the dimming – a sudden darkening of the star – has continued to fascinate researchers. Now a clear answer may have come from an unexpected source: an orbiting weather satellite.
Normally the satellite, Himawari-8, is focused on more mundane matters: the clouds and vegetation marking the changing weather on Earth. Yet, it turned out, the telescope also happened to capture an image of Betelgeuse once every two days. A team in Japan found these observations stretched over four years between 2017 and 2021, a span that conveniently covers the great dimming.
The data supports an earlier theory that the dimming was caused by a cloud of dust. Astronomers now think that the star threw out a blob of gas sometime in late 2019. Soon afterwards Betelgeuse cooled, as part of a regular cycle of brightening and dimming that regulates the star. The gas then also cooled, condensing into a cloud of dust. Together these – the normal cooling and the dust cloud – cut the light seen from Earth; creating the illusion Betelgeuse was cooling by more than expected.
Betelgeuse, then, seems likely to stick around for a bit longer. It will, nonetheless, remain an object of intense fascination for astronomers and the media alike. It is the closest supergiant star in the sky, and the first star – bar the Sun – for which we managed to directly image the surface. Astronomers are sure to continue probing the dying giant for years to come.
The James Webb Gets Ready For Science
As the James Webb Space Telescope draws to the end of commissioning, attention is starting to turn to its first scientific targets. Two are already drawing interest: a pair of rocky and odd exoplanets sitting a few dozen light years from Earth. Both are categorised as “super-Earths”, but neither are expected to look anything like our green and blue world.
The first, 55 Cancri e, orbits just over a million miles from its star. That distance is unbelievably close – even Mercury, scorching under the Sun’s heat, lies more than twenty times further. The planet, therefore, is expected to be extreme: the sun side of the planet should be so hot that its rock surface melts, forming a vast ocean of lava.
Depending on how 55 Cancri e rotates, that could imply bizarre weather conditions. Astronomers speculate that some of the lava might evaporate, creating clouds of liquid rock in the heat of day. As night falls, that lava would plunge to the surface, producing the horrifying idea of superhot liquid rock raining from the skies. This, for sure, is no world humans will ever visit.
The second is LHS 3844 b. Like 55 Cancri e, this planet is also close to its star, completing each orbit in less than twelve hours. Yet this star is cool, so LHS 3844 b should have a solid surface. Astronomers are hoping the James Webb will be able to pick out the surface of the planet, allowing them to figure out what kind of rocks are found there.
Both planets promise to demonstrate the power of the James Webb, giving us an unprecedented look at two extreme exoplanets close to Earth. Other science will follow over the first year: including a look at the Kuiper Belt, a cloud of comets surrounding the solar system; observations of the deep and ancient universe; and studies of several distant and intriguing galaxies.
NASA has also announced when the first set of science-quality images from the telescope will be released. The package, which will celebrate the end of commissioning, will be made public on July 12. But what, exactly, the telescope has been looking at is a closely guarded secret. NASA says only that the images will be in full colour and will show off the full range of the telescope’s capabilities.
Voyager I Sends a Stream of Nonsense
Forty-five years after leaving the Earth, Voyager I now lies more than twenty billion kilometres from Earth. It is thus the most distant relic of human civilization. Around a decade ago the probe crossed a boundary recognised as the edge of the Solar System: a point at which the solar wind ceases to flow and the effects of interstellar space are felt more keenly.
Now the probe seems to be encountering some technical issues. While Voyager is, according to NASA, still working normally, operators are getting odd data from its attitude control system. This is the part of the spacecraft responsible for rotating the probe, ensuring the antennas are precisely pointed at Earth.
Though the data received looks odd, operators have said that the attitude system seems to be working as expected. The antenna itself, vital for communicating with the satellite, is still pointed towards the Earth. That suggests the fault may lie in the reporting of the data, rather than in an actual fault with the attitude control system.
Quite how much longer the probe will keep working is debatable. Engineers have hacked together a series of workarounds to keep Voyager running; making use of every watt of power available. Before long, however, the onboard power generation will fall so low that instruments will no longer be able to run. Its great distance, too, means that the signal we receive is growing ever weaker,
For those that have spent decades – sometimes their entire careers – working on Voyager, that end will be a sad moment. It will, indeed, mark the conclusion of one of the most fascinating and ambitious projects ever attempted by humanity.
Arianespace Prepares Its New Rockets
Arianespace, the largest European rocket company, plans to fly two new rockets this year. The first, scheduled for launch in July, will be the Vega-C rocket, a small launcher designed to reach low Earth orbit. Then, close to the end of the year, the company will make the first flight of Ariane 6: the latest of Europe’s powerful and reliable Ariane series of rockets.
Engineers will be hoping to avoid a repeat of the first test flight of the Ariane 5. Forty seconds after liftoff that rocket dramatically exploded. The issue was eventually traced to a software bug in old code; an error since labelled “the most expensive bug in history”. Since that incident, however, the Ariane 5 flew almost without fault; notching up over one hundred successful launches. Perhaps most notably, it was an Ariane 5 that lofted the James Webb into space at the end of last year.