Starship Asterisk*

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A way of estimating more accurate distances to the thousands of so-called planetary nebulae dispersed across our galaxy has been announced by a team of three astronomers based at the University of Hong Kong: Dr. David Frew, Prof. Quentin Parker, and Dr. Ivan Bojicic. ...

Despite their name, planetary nebulae have nothing to do with planets. They were described as such by early astronomers whose telescopes showed them as glowing disc-like objects.

We now know that planetary nebulae are actually the final stage of activity of stars like our Sun. When they reach the end of their lives, these stars eject most of their atmosphere 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 thousands of planetary nebulae in our galaxy alone, and they provide targets for professional and amateur astronomers alike, with the latter often taking spectacular images of these beautiful objects. But despite intense study, scientists have struggled to measure one of their key properties -- their distance. ...

The solution presented by the astronomers is both simple and elegant. Their method requires only an estimate of the dimming toward the object (caused by intervening interstellar gas and dust), the projected size of the object on the sky (taken from the latest high resolution surveys) and a measurement of how bright the object is (as obtained from the best modern imaging). ...

• Monthly Notices of the RAS 455(2):1459 (2016 Jan 11) DOI: 10.1093/mnras/stv1516
  arXiv.org > astro-ph > arXiv:1504.01534 > 07 Apr 2015 (v1), 09 Jul 2015 (v2)