Cheap Astronomy - Dear CA #142: Knowns & Unknowns

Hosted by Steve Nerlich.

Who knew?

Dear Cheap Astronomy – Do gravitons exist?

Once again we're dealing with something hypothetical here – so much like virtual particle pairs that pop out of nowhere and can evaporate black holes, it's entirely possible that gravitons exist, but at this time it's probably appropriate to entertain the notion that they might not exist either. Ten years ago we would have said the same thing about the Higgs boson, but that was positively identified by the Large Hadron Collider in 2012 and hence moved from being a hypothetical to a real particle at that time.

Dear Cheap Astronomy – Is the Universe full of explosions?

Well, yes it does seem that way. There are the various classes of novae, but also bursts of various kinds, ranging from radio to gamma ray bursts. They've traditionally been classified separately although the boundaries of those classifications often blur. The word nova means new – arising from the fact that when they happen a star may become visible due to a sudden transient brightening. A standard nova arises from binary systems in which one star is a white dwarf that gravitationally draws material off its binary companion star which is a red giant.

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