The ominous warning – "winter is coming", popularised by fantasy series Game of Thrones – applies equally well to Pluto.
The dwarf planet's tenuous atmosphere appears to be on the verge of a stunning collapse due to a change in the seasons and approaching colder conditions, according to research to be published in the journal Astronomy & Astrophysics.
Astronomers - Pluto - Atmosphere - Atmosphere - Observations
Discovered in 1930, it was only around 1980 that astronomers began to suspect Pluto might have an atmosphere. That atmosphere was tentatively discovered in 1985 and fully confirmed by independent observations in 1988.
At the time, astronomers had no way of knowing what dramatic changes were in store for the little world's thin envelope of nitrogen, methane and hydrocarbons.
Coincidence - Decades - Century - Decades - Alignment
By a cosmic coincidence, the last decades of the 20th century and first decades of the 21st also saw a lucky alignment of Earth, Pluto and the dense stellar fields of the distant centre of the Milky Way.
This coincidence means Pluto passes relatively often between us and a background star. When this happens, its shadow falls on Earth, an event astronomers refer to as an occultation.
Occultation - Observatory - Path - Shadow - Star
During an occultation, any observatory that happens to lie within the path of the shadow can watch the star seem to disappear as Pluto passes in front of it, and then to reappear as the planetary alignments shift. For any given place on Earth's surface, a Pluto occultation lasts a couple of minutes at most.
The technique of occultations has been widely used to study the orbits, rings, moons, shapes and atmospheres of the worlds of the outer Solar System, including asteroids, comets, planets and dwarf planets.
Observers - Locations - Earth - Size - Shape
By comparing what observers see at different locations on Earth, the size and shape of the occulting world can be worked out. If the object has an atmosphere, then for a few brief seconds as the starlight...
Wake Up To Breaking News!