Space & astronomy · the experiment
Unmask the gamma-ray bump
Two virtual Milky Ways, supernovae flaring on and off, a bump that looks like Fermi's. Four questions, from beginner to expert, to judge whether the excess could just be bad timing.
1 · Find the only source
Beginner
In the two simulated galaxies, where does all the gamma-ray glow come from?
2 · Work out the spreading time
Cosmic rays spread out in a time τ ∼ L²/κ, where L is the size of the region and κ their diffusion coefficient. In the central kiloparsec, τ is about a million years.
Intermediate
With the same κ, how long would a region 2 kiloparsecs across take?
3 · Weigh the simulated galaxies
In their centres, the simulated galaxies form stars 10 to 100 times faster than the Milky Way's central zone.
Expert
What effect could this have on the gamma-ray bumps they produce?
4 · Read the authors' test
A future telescope observes other galactic centres. Each shows a gamma-ray bump, but all at different energies.
Expert
What would this result favour?
Bump unmasked
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