Stars like dust: the LMC in ultraviolet light


The above image mapped with an optical view here, shows up the hot, blue stars of the Large Magellanic Cloud in ultraviolet light. The image is a composite in three narrow colour bands located in the 160 to 330 nanometer wavelength range. These are A stars and hotter; for example, the peak of the emission spectrum of a star with effective temperature 10000 Kelvin is 290 nanometers.

Readers will realise we have all kinds of extreme physics here, and I share this piece from the cutting edge of particle physics, concerning the mysterious XYZ particles, related to charmonia, heavy meson pairs consisting of a charm and anti-charm quark. The new particles, which are named rather after their own naming scheme, might be tetraquark combinations or hybrid particles also containing gluons in excited states. The Y(4260), discovered in 2005, is the first example, as it appears to be made of a charm quark, an anti-charm quark, and an extra gluon:

Charmonia, which are heavy mesons, contain a charm and anti-charm quark. Because they are a composite particle, they can exist in a number of different energy states – the most famous being the first excited state called the J/ψ particle. Discovered in 1974, the J/ψ particle made physicists realize for the first time that quarks are real. Although physicists have learned much about quarks over the past four decades, current theories are still not good enough to predict which of the many possible combinations of quarks will form stable mesons.


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