宇宙望遠鏡「DAMPE」を用いた研究チームは、複数の種類の粒子において、宇宙線のスペクトルが共通して軟化する現象を特定した。このパターンは、陽子から鉄原子核に至るまで、剛性約15テラ電子ボルトの地点で現れる。学術誌「Nature」に掲載されたこの発見は、銀河系内における高エネルギー粒子の挙動について新たな知見をもたらすものとなる。
1世紀以上にわたり、科学者たちは自然界で最もエネルギーの高い粒子である宇宙線を研究してきた。2015年12月に打ち上げられたDAMPEミッションの観測データから、これらの粒子の数が特定の剛性閾値を超えると急激に減少することが明らかになった。この現象は陽子、ヘリウム、炭素、酸素、そして鉄原子核のいずれにおいても確認されている。
New research suggests the Amaterasu particle, one of the most energetic cosmic rays detected, could be an ultraheavy atomic nucleus rather than a proton. The findings, from scientists at Penn State, were published in Physical Review Letters. They indicate such nuclei could retain extreme energy over vast distances in space.
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Building on prior detections of gamma-ray emissions from the Milky Way's center, physicists led by Gordan Krnjaic at Fermilab propose dark matter consists of two distinct particles that interact to produce detectable signals. This resolves the puzzle of signals in the Milky Way but none in dark-matter-rich dwarf galaxies, as observed by the Fermi Gamma-ray Space Telescope.
Physicists with the STAR collaboration have observed particles emerging directly from empty space during high-energy proton collisions at Brookhaven National Laboratory. The experiment provides strong evidence that mass can arise from vacuum fluctuations, as predicted by quantum chromodynamics. Quark-antiquark pairs promoted to real particles retained spin correlations tracing back to the vacuum.
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Scientists have detected traces of iron-60 in Antarctic ice up to 80,000 years old, showing that the solar system is moving through material from an ancient stellar explosion. The findings come from a study published in Physical Review Letters and point to the Local Interstellar Cloud as the source of the radioactive isotope.