Look at me! I'm a star!

17P/Holmes is a big showoff.

A comet that unexpectedly brightened in the last couple of weeks and is now visible to the naked eye is attracting professional and amateur interest. [...] The comet is exploding and its coma, a cloud of gas and dust illuminated by the sun, has grown to be bigger than the planet Jupiter. The comet lacks the tail usually associated with such celestial bodies but can be seen in the northern sky, in the constellation Perseus, as a fuzzy spot of light about as bright as the stars in the Big Dipper. [...]

Until October 23, the comet had been visible to modern astronomers only with a telescope, but that night it suddenly erupted and expanded. A similar burst in 1892 led to the comet's discovery by Edwin Holmes. [...] Scientists speculate the comet has exploded because there are sinkholes in its nucleus, giving it a honeycomb-like structure. The collapse exposed comet ice to the sun, which transformed the ice into gas.