Happy 26th birthday to the Hubble Space Telescope! It's a helluva thing that the finest space imaging instrument of 1990 also happens to be the finest space imaging instrument of 2016.
That isn't a knock on technological progress since then, but a hat tip to the NASA engineers who designed not just a space telescope capable of seeing very nearly the beginning of the universe, but a space telescope that could be upgraded and repaired over time as a technology platform. In 2016, Hubble remains the only telescope that can be attended to in orbit by astronauts, a feature that famously allowed it to survive a near-fatal design error.
As a result, we now know about (if not understand) such things as dark energy and the accelerating expansion of the universe; the staggering prevalence of black holes among nearby galaxies; the likely prevalence of extrasolar planets around Sun-like stars; how young stars and solar systems develop in cloud-nurseries of dust and gas; supernova prediction; how to map dark matter; and what the likely age of the universe itself is and when it will die. How about a comet with six tails? Or the tragically beautiful death of a star? Or the first maps of the surface of Pluto?
For the telescope's birthday, NASA is pushing this image of the Bubble Nebula. This is a thing the telescope does every year for its anniversary: Find something awesome and gaze at it.
The Bubble Nebula lives about 8,000 light-years away in the constellation Cassiopeia. Hubble has imaged it before, but only scraps of it at a time. This latest image is the result of a mosaic of four images collected by Hubble's Wide Field Camera 3, the platform's most recent upgrade (2009).
The bubble in question surrounds the star SAO 20575, which is 10 to 20 times the size of our own Sun. It's the result of intense stellar winds racing outwards at some 100,000 kilometers per hour, which can be imagined as just an unfathomable outward pressure. The sphere itself is where these winds meet the cloud of gas surrounding the star. The boundary is hardly static, however, and the bubble is still expanding. Currently, it's about 10 light-years in diameter.
The Bubble Nebula also presents an interesting mystery. Why isn't the nebula's core star centered within the bubble? The roundness and symmetry of the bubble would seem to imply this, but instead we have the above. Perhaps the answer to this Hubble mystery will once again point astronomers toward new knowledge.