My latest astronomy article involves planetary nebulae, which, despite their name, have nothing to do with planets. Instead, they are actually stars that have reached the end of their lives. During this final stage, they eject most of their atmosphere out into space, leaving behind a hot dense core. Light from this core causes the expanding cloud of gas to glow in different colors as it slowly grows, fading away over tens of thousands of years.
There are literally thousands of planetary nebulae in the Milky Way alone, and these are favored targets for professional and amateur astronomers alike. Despite intense study, however, scientists have struggled to measure their distance.
Now, a trio of astronomers based at the University of Hong Kong have figured out a way to more accurately estimate the distance to these cosmic beauties.
Image Above: A collage showing 22 individual planetary nebulae artistically arranged in approximate order of physical size. The scale bar represents 4 light years. Each nebula’s size is calculated from the authors’ new distance scale, which is applicable to all nebulae across all shapes, sizes and brightnesses. The very largest planetary nebula currently known is nearly 20 light years in diameter, and would cover the entire image at this scale. Credit: ESA/Hubble & NASA, ESO, Ivan Bojicic, David Frew, Quentin Parker.