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Australian astronomers picked up a strange radio signal in mid-June. It was one of the closest to our planets and for a while it surpassed everything else in the sky. Subsequent searches searched its sources and raised new questions about the growing problem of debris in Earth’s orbit.
But at first, researchers thought they were observing something exotic.
“They’re doing this,” said Clancy James, an associate professor at the Institute of Radio Astronomy at Curtin University in Western Australia.
The data James and his colleagues were looking at came from Askap Radio Telescope, an array of 36-dish antennas in Wajaliyamaji. Typically, teams search for a type of signal called “fast radio bursts,” a flash of energy that explodes from a distant galaxy.
“These are very powerful explosions of radio (waves) that last about milliseconds,” James said. “We don’t know what they’re producing. They’re really trying to find out because they’re really trying to know physics. They’re very bright. They’re also trying to use them to study the distribution of matter in the universe.”
Astronomers believe that these bursts could come from magnetores, according to James. These objects are very dense remnants of dead stars with powerful magnetic fields. “The magnetor is totally, completely crazy,” James said. “These are the most extremes you can get in space before something turns into a black hole.”
However, this signal appeared to come from a very close Earth. “We managed to solve it that it came from about 4,500 kilometers (2,800 miles). And we got a very accurate match with this old satellite called Relay 2. We had a database where we could find where a particular satellite should be, and there were no other satellites nearby,” James said.
“We were all disappointed with that, but then we thought, ‘Wait a second. What really created this anyway?” ”
NASA put Relay 2, an experimental communications satellite, into orbit in 1964. It was released two years ago and used to relay signals between the US and Europe, and to broadcast the 1964 Summer Olympics in Tokyo.
Just three years later, its mission ended and Relay 2 has already turned into space junk as both major equipment was breached smoothly. Since then, it has orbited our planet aimlessly until James and his colleagues linked it to a strange signal they detected on June 13th.
But after decades of silence, can a dead satellite suddenly come back to life?
To answer that question, astronomers wrote a paper on analysis. It will be published in The Astrophysical Journal Letters on Monday.
They realized that the signal was not caused by anomalies in distant galaxies, but when they saw the image rendered by the telescope (a graphical representation of the data) being blurred, there was something nearby.
“I got this blurry image
This discrepancy in data between different antennas caused blur, and to remove it, researchers eliminated signals coming from the outer antennas to support only the inner portion of the telescope, spreading around 2.3 square miles in the Australian Outback.
“When we first detected it, it looked pretty weak. But when we zoomed in, it was brighter and brighter. The entire signal is about 30 nanoseconds, or 1/30 billion seconds, but the main part is about 3 nanoseconds, and in reality it’s something our instrument can see,” James said. “The signal was about 2,000 or 3,000 times brighter than all the other wireless data our (equipment) detects. It was the brightest in the sky, with thousands of people.”
Researchers have two ideas about what could have caused such a powerful spark. The main culprit was probably accumulation of static electricity on the metal skin of the satellite, which was suddenly released, James said.
“It starts with the accumulation of electrons on the surface of the spacecraft. The spacecraft begins to charge for the accumulation of electrons. It continues to charge until there is enough charge to shorten some of the components of the spacecraft, and suddenly it sparks. “It’s exactly the same as rubbing your foot on the carpet and stabing your friend with your fingers.”
A less likely cause is the impact of micrometeorites, collisions of space rocks smaller than 1 millimeter (0.039 inches). “And this plasma can emit short bursts of radio waves.”
However, strict circumstances must occur for this micrometeorite interaction, and research suggests that it is unlikely that it is the cause. “I know that (electrostatic) discharges can actually be very common,” James said. “As far as humans are concerned, they are not at all dangerous. But they can absolutely damage the spacecraft.”
Because these discharges are difficult to monitor, James shows that radio signal events can reveal “the strange thing happening to satellites,” and that researchers can search for similar events to use building devices that are much cheaper than the vast telescope they used. He also speculated that since Relay 2 is an early satellite, it is more likely to cause static charging accumulation than modern satellites designed with this issue in mind, and that the material it is made to be more likely to be static charging.
However, the perception that satellites can hinder galaxy observations presents a challenge and adds to the list of threats posed by space junk. Since the dawn of the space age, almost 22,000 satellites have reached orbit, with over half still operating. Over the decades, dead satellites collided hundreds of times, creating a field of thick debris, giving birth to millions of small pieces orbiting at speeds up to 18,000 miles per hour.
“We’re basically trying to see something nanoseconds coming from space. If a satellite can generate this, we really need to be careful,” James noted the possibility of confusing satellite bursts with astronomical objects. “As more and more satellites rise, it will make this kind of experiment more difficult.”
James and his team’s analysis of the event was “comprehensive and wise,” according to James Cordes, a professor of George Feldstein astronomy at Cornell University, who was not involved in the study. “I think their interpretation is probably correct given the long known phenomenon of electrostatic discharge. I don’t know if the microterroid ideas featured on paper as an alternative are mutually exclusive. The latter could trigger the former.”
Ralph Spencer, professor emeritus of radio astronomy at the University of Manchester in the UK, was not involved in the work, but agreed that the proposed mechanism could be realized and noted that spark discharges from GPS satellites have been previously detected.
This study shows that celestial bursts must be careful not to confuse radio bursts from astrophysical sources with electrostatic discharge or microsequential bursts, noted by both Code and Spencer.
“The results show that such narrow pulses from space may be more common than previously thought, and careful analysis is required to show that radiation comes from stars and other astronomical objects rather than artefacts close to Earth,” Spencer added in an email.
“New experiments currently under development, such as the low-frequency array of square kilometre arrays (SKA-low), built in Australia, can shed light on this new effect.”
