Makemake: The planet with no atmosphere

An artists impression of the surface of the distant dwarf planet Makemake. Photo / AP

Astronomers say Pluto's icy more distant sister seems even more alien than originally thought because it doesn't have an atmosphere.

Scientists gained that bit of new knowledge about the dwarf planet Makemake by measuring light from data gathered by European Organisation for Astronomical Research's three large telescopes in Chile and other smaller telescopes across South America.

Makemake is one of four dwarf planets in our solar system beyond Neptune, and is about two-thirds the size of Pluto.

It was previously thought Makemake would have an atmosphere similar to Pluto, however a new study, published in Nature, has found Makemake is not surrounded by a significant atmosphere, as is the case with dwarf planet Eris.

The small planet may simply have some pockets of atmosphere from methane ice turning into gas.

The research team, led by Jose Luis Ortiz from the Instituto de Astrofisica de Andalucia in Spain, looked at Makemake as it passed in front of a distant star.

"As Makemake passed in front of the star and blocked it out, the star disappeared and reappeared very abruptly, rather than fading and brightening gradually. This means that the little dwarf planet has no significant atmosphere," Ortiz said. "It was thought that Makemake had a good chance of having developed an atmosphere - that it has no sign of one at all shows just how much we have yet to learn about these mysterious bodies. Finding out about Makemake's properties for the first time is a big step forward in our study of the select club of icy dwarf planets."

The researchers said Makemake's lack of moons and its great distance from Earth make it difficult to study, meaning what is known about the dwarf planet is only approximate.

In fact, it was only possible to observe Makemake in such detail because it passed in front of a star - an event known as a stellar occultation. Occultations are particularly uncommon in the case of Makemake, because it moves in an area of the sky with relatively few stars.

"Pluto, Eris and Makemake are among the larger examples of the numerous icy bodies orbiting far away from our Sun," Ortiz said. "Our new observations have greatly improved our knowledge of one of the biggest, Makemake - we will be able to use this information as we explore the intriguing objects in this region of space further."

Makemake is so far from the sun its temperature is about -240 Celsius. Scientists compare it to getting warmth from a 100-watt light bulb 10 meters away. It was discovered in 2005.

- www.nzherald.co.nz, AP