Australasian Science: Australia's authority on science since 1938

Galactic Democracy

By Stephen Luntz

Public outrage over Pluto’s demotion as a planet has inspired a unique attempt to engage the public in astronomical decision-making.

The full text of this article can be purchased from Informit.

Prof Duncan Forbes of Swinburne University has teamed with Prof Pavel Kroupa of Universitaet Bonn to offer members of the public a chance to vote on the definition of a galaxy.

On its discovery, Pluto was thought to be larger than Mercury. With no clear definition of the boundary between a planet and smaller objects, its planetary status survived even as its size was revised downwards. Eventually, the discovery of increasing numbers of objects of similar size forced the astronomical community to come up with a consistent definition.

Something similar is happening with galaxies. Increasing numbers of objects have been found that fill the gap in size between dwarf galaxies and globular clusters. Meanwhile, astronomers are starting to wonder how many globulars are actually the cores of former dwarves. Forbes came up with an estimate of 25% (AS, May 2010, p.5), but other astronomers think it is possible all of them are (AS, Jan/Feb 2011, p.12).

“I think it is important to have a clear definition and well-defined process for determining what is a galaxy. Such a process may provide new insight into how galaxies form and evolve with time,” says Forbes.

However, Forbes is keen to avoid the situation where the ruling is hijacked by astronomers attending an International Astronomical Union conference, as happened in Pluto’s case. The angst created by the...

The full text of this article can be purchased from Informit.