PARIS: A rare dalliance with a star in a remote part of our Solar System has allowed scientists to glean data on a distant, icy dwarf planet about which we knew very little before, astronomers said.
They had expected to find an atmosphere similar to that of Pluto on the planet named Makemake, but instead saw “no sign of one at all”, the group wrote in the journal Nature.
They also discovered that Makemake, one of five dwarf planets known to exist on the edge of our Solar System, reflected more light from the Sun than its near neighbour Pluto.
Reflection of dirty snow
Makemake reflected 77% of the Sun’s light compared to Pluto’s 52% – akin to the reflective power of dirty snow, the team reported.
Makemake is about two-thirds the size of Pluto and orbits at a distance of about 7.8 billion kilometres from the sun – somewhere between Pluto and Eris, the biggest and most distant of the known dwarf planets.
Previous observations had shown Makemake to be similar to its fellow dwarfs in many ways, leading some to expect that its atmosphere would resemble Pluto’s, said a statement issued by the team led by Jose Luis Ortiz of the Instituto de Astrofisica de Andalucia in Spain.
Star disappeared and reappeared abruptly
To make its observations, the team had to wait until Makemake passed in front of a distant star, which happened on April 23, 2011, and then trained seven telescopes in Brazil and Chile on the mysterious body.
“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,” said Ortiz.
“This means that the little dwarf planet has no significant atmosphere.”
Makemake’s lack of moons and its great distance from us make it difficult to study.
But with their new observations, the team was able to glean new data about the planet’s size and density.
The concluded it is a sphere slightly flattened at the poles – its polar equatorial axis about 1,430 kilometres.
“Makemake was the poorest-known dwarf planet and thanks to our study we have revealed several important properties of this body,” Ortiz said.
The opportunity was a rare one, as Makemake moves in an area of the sky with relatively few stars, said the statement.
The planet was initially nicknamed Easterbunny, having been discovered a few days after Easter in March 2005.
It was officially christened in July 2008 – named for the creator of humanity and god of fertility in the myths of Easter Island.
Abstract of the paper, “Albedo and atmospheric constraints of dwarf planet Makemake from a stellar occultation”, published in Nature