The Week in Space and Physics
The Week in Space and Physics
On Hubble, a failed attempt to launch the SLS, lunar nuclear reactors and a black hole controversy
Hubble, for decades the pride of astronomy, seems to have rather lost its shine in recent months. A rival, in the shape of a golden infrared telescope, has dislodged it from its throne, made its once praised images look dull and blurred, and mocked its ability to look deeper into space than any other.
In a rather symbolic opening, the James Webb did all three of these at once: replicating an earlier deep field taken by Hubble. The new image, produced in the fraction of the time used by Hubble, shows the distant universe in astonishing clarity and depth; revealing details Hubble could never have seen.
Yet the symbolism is misplaced, for Hubble is far from obsolete. True, the James Webb may better its abilities in some areas, but it is no successor or true replacement of Hubble. The two telescopes are complementary instruments, each bringing a unique vision and ability. Indeed, by working together, the two telescopes can reveal detail that neither could alone.
The image above, of the Phantom Galaxy, shows an early demonstration of this partnership. Hubble’s image, on the left, is taken in optical wavelengths. It shows, more or less, how the galaxy would look with our own eyes, if only we could get close enough to view it.
Webb’s image, on the right, shows something else: the galaxy in infrared, a kind of light invisible to our eyes. Instead of stars and other bright objects, the Webb traces the presence of cooler things. Streams of gas and dust, for example, or filaments stretching for thousands of light years across the galaxy’s arms.
When the two views are combined, as in the central image, a more complete picture of the galaxy emerges. Astronomers can match the gas filaments with glittering clusters of newborn stars. They can map out how dust and gas has moved across the galaxy, how it has fed the birth of stars, how supernova have cleared bubbles and voids.
Hence the importance of the Hubble-Webb collaboration. When the two telescopes are pointed at the same object, they can together spot details and map processes that either alone would miss. When dramatic events light up the sky - perhaps an erupting supernova, or a flaring black hole - the two will work in tandem to monitor what is happening. Indeed, the two can even work together when examining exoplanet atmospheres. Hubble can spot gases that the Webb, even with its more powerful gaze, may miss.
Hubble, then, still has good work to do. Yet its time may be limited anyway: the observatory has been in space for more than three decades now, and some parts are beginning to break down. Of most concern are its gyros, components that allow astronomers to swing and point the telescope at targets. Three of the six onboard have failed. A fourth failure may well spell the beginning of the end for Hubble.
When Will The SLS Fly?
On the 13th June, 2009, NASA tried to launch the Space Shuttle Endeavour. As they pumped gas into the shuttle’s fuel tanks, they encountered a problem. Hydrogen was escaping from a seal, creating a dangerous risk of fire and explosion. The launch was cancelled, the seal replaced and another attempt scheduled.
Yet during that second go another leak was sprung, and NASA was forced to delay again. Two more aborted attempts followed - thanks this time to lightning and bad weather - until Endeavour finally took flight on the fifth attempt in mid-July.
History, then, seemed to repeat itself last Saturday afternoon, as a hydrogen leak scuppered the second attempt to launch the SLS rocket. Engineers detected the leak during preparations for launch but, despite frantic efforts to fix it, failed to do so before the launch window closed.
The problem, NASA later reported, lay in a seal that should have secured the hydrogen inlet. This seems to have been damaged during the fuelling process when operators accidentally opened the wrong valve. Though the error was caught and corrected within a few seconds, it appears to have been long enough to damage the seal and cause hydrogen to leak out.
The similarity with the earlier Shuttle delays is more than just a coincidence. The SLS, thanks to pressure from Congress, was designed around components used in the Shuttle. That means it has inherited many of the faults that engineers uncovered in the Shuttle’s design, including those related to the hydrogen fuelling.
NASA has few good options from here. Another attempt to launch in early September seems out of the question. A second window of opportunity opens at the end of the month – but if the rocket must be taken back to the hanger for remedial work, as seems likely, NASA will not be ready in time to make use of it. A later window, in the second half of October, therefore looks like a more likely bet.
The failed attempts to launch are disappointing and somewhat embarrassing for NASA. The events of the past two weeks have done nothing to silence the many critics of the SLS rocket, and may embolden calls to find an alternative. If Elon Musk succeeds in launching Starship, a spacecraft of similar power, before NASA can put the SLS in orbit, those calls are bound to grow even louder.
China Plots a Nuclear Future
China’s plans to build a nuclear reactor designed for use in space seem to be making progress. According to several reports, a prototype reactor recently passed a series of performance tests. That may now pave the way for its use in actual missions.
According to Chinese media, the reactor project was launched in 2019, possibly in response to American plans to develop new nuclear systems for use in space. Though such reactors could be used in power hungry satellites and missions to the dark outer solar system, they are more likely to find use in future lunar bases.
Both America and China have expressed ambitions for long term stays on the Moon. That – if stays are to last longer than two weeks – means finding a way to power bases through the long cold lunar nights. Solar power, often used for missions to Mars or elsewhere in the inner solar system, can’t do this, but nuclear reactors probably could.
Few details are available about the Chinese project. The country has a plan to build out a lunar base over the next decade – though this will initially be fairly simple and visited only by robots. Over time, however, Chinese space scientists may build this up into a more sophisticated facility; one visited regularly by Chinese astronauts. If so, this new nuclear reactor could be a key part of China’s future presence on the Moon.
Black Hole Ring… or Not?
The first image of a black hole brought worldwide attention and praise. Yet it has also recently drawn criticism, as some scientists questioned the techniques and algorithms used to stitch the image together. Now a more detailed probing of the image, which claimed to reveal a slender ring of light around the black hole, has raised even more controversy.
This circle of light, known as a “photon ring”, comes from the very edge of a black hole, the last point at which escape from its immense gravity is still possible. It is an effect predicted by models of black holes, yet – until two weeks ago – one that no one had ever seen. That seemed to have changed with the publication of a new paper, which claimed to have reprocessed the black hole image and detected the ring.
Yet other researchers have been quick to criticise this claim. The ring appears brighter than expected – a factor that some have said makes the discovery unlikely. Others have criticised the reprocessing effort, arguing that stronger evidence is needed to claim the discovery. Finer images, with more powerful telescopes, could resolve the question – but, for now at least, the claimed photon ring is far from a sure thing.