Evidence for the Local Bubble has been brewing for several decades and its presence was inferred from X-ray observations of the local galaxy - a background glow of X-ray radiation was detected in all directions. Although the evidence seemed strong for an ancient supernova soup, there was other possible interpretation.
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"Within the last decade, some scientists have been challenging the (supernova) interpretation, suggesting that much or all of the soft X-ray diffuse background is instead a result of charge exchange," said F. Scott Porter of the Goddard Space Flight Center, Greenbelt, Md.
Charge exchange can occur between solar wind ions (charged particles that lack electrons) and neutral gases. When the two gases come into contact within the solar system - between the solar wind and a comet's coma, for example - electrons can be stripped from the neutral particles, generating X-ray emissions.
Therefore, many astronomers argued that this diffuse X-ray glow observed in all directions may be a phenomenon inside the solar system and not superhot particles from 10 million year-old supernovae outside the solar system.