Solar probe touches the sun

On Christmas Eve, a spacecraft launched by NASA on a mission to “touch the Sun” reached closer to the star than ever before.

Since its launch in 2018, the Parker Solar Probe has used seven flybys of Venus to gravitationally direct it closer to the Sun, aiming to collect data that could help explain the workings of this star. On 26th December last year, a beacon signal was received from the probe indicating that it had survived its closest ever approach, passing through the corona (the outermost part of the Sun’s atmosphere) 6.1 million km from the solar surface and experiencing temperatures of around 980ºC.

It’s hoped that the probe will provide information about the origin and evolution of solar wind, a stream of electrically charged particles released by the Sun. As the solar wind streams outwards at speeds of more than 1 million miles per hour, it drags the Sun’s magnetic field with it. The charged particles follow the spiralled magnetic field lines as they burst out from the Sun, creating plasma waves that can be ‘heard’ by the probe.

“It’s hoped that the probe will provide information about the origin and evolution of solar wind, a stream of electrically charged particles released by the Sun”

The probe should also shed light on how the corona comes to be millions of degrees hotter than the solar surface below it. Moreover, it’s possible that the probe’s rapid speed (692,000 kilometres per hour during its closest approach, the fastest any human made object has ever travelled) could allow for the observation of relativistic effects in the spacecraft’s trajectory.

The data collected will be received later in January when the probe is in the correct orientation relative to Earth to send large amounts of information. This could be used to help forecast changes in the space environment and space weather that will affect life and technology on Earth in future, and to learn more about the workings of stars across the universe, which could aid in the search for other habitable worlds.

Loneliness affects protein levels

New research suggests that loneliness and social isolation cause changes in the levels of some blood proteins that could increase the risk of disease.

Researchers at the University of Cambridge conducted a protein-wide association study (PWAS) using data from UK Biobank, a health database holding detailed information on half a million volunteers. Information from more than 42,000 participants was analysed for the levels of nearly 3000 plasma proteins in an attempt to characterise the protein “signatures” of social isolation and loneliness.

After adjusting for potential confounding factors such as socioeconomic status and ethnicity, the study found that there were 175 proteins associated with isolation, and 36 with loneliness. The researchers then used a technique called Mendelian randomisation to determine the direction of this relationship: whether the correlation was because the proteins were increasing the risk of loneliness, or whether loneliness was affecting protein levels. They found that the proteins did not seem to cause social isolation or loneliness, but these factors did influence the levels of five of the proteins.

These proteins have roles in inflammation, the immune system and metabolic function, helping to crystallise the mechanisms by which social relationships can influence physical health. Identifying these changes in protein levels could also offer potential drug targets for the treatment of the health risks associated with loneliness in future.

How mice make memories

Studying neural activity in mice has shown that the brain may avoid rewriting old memories with new ones by processing the two types of memory in distinct phases of sleep.

During sleep, recently acquired memories like events of the preceding day are replayed in the hippocampus in preparation for long-term storage. However, this happens alongside the reactivation of more long-term memories, meaning scientists have long wondered how the brain avoids the phenomenon of ‘catastrophic forgetting’, where old memories are overwritten with new ones.

Researchers tracked the sleep of mice by measuring their pupil size, finding that during one of the deep phases of sleep, their pupils shrink and then return to their original sizes repeatedly. They used a technique called optogenetics, where light is used to control the electrical activity of genetically engineered neurons in the brain, to suppress neural firing during either the small pupil or large pupil stages of sleep, and compared the effects of this on memory.

“the mice forgot recently-acquired memories, such as the location of a hidden reward in a maze, when brain activity was suppressed during the small-pupil stage”

The scientists found that the mice forgot recently acquired memories, such as the location of a hidden reward in a maze, when brain activity was suppressed during the small pupil stage. When the large pupil stage was interrupted, more established memories (from a few days prior) were forgotten. This suggests that older memories were processed during the large pupil stage, while newer memories were being incorporated in the small pupil stage.

This separation of the replay of older and newer memories into two distinct temporal stages of sleep presents a solution to how the brain avoids catastrophic forgetting in mice, and the evolutionarily ancient nature of memory led one neuroscientist to suggest that a similar separation probably also occurs in humans. Catastrophic forgetting affects artificial neural networks (algorithms modelled on the brain that are involved in many AI tools used today), so understanding how the brain avoids this phenomenon may help in developing AI models that can avoid it too.

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