Dwarf planet Makemake lacks atmosphere
Frigid Makemake’s passage in front of a distant star revealed its secrets for the first time.
November 21, 2012
Astronomers used three telescopes at the European Southern Observatory (ESO) in Chile to observe the dwarf planet Makemake as it drifted in front of a distant star and blocked its light. The new view allowed them to determine whether Makemake is surrounded by an atmosphere. The scientists also gained information about Makemake’s density, shape, and reflection properties for the first time.
This artist’s impression shows the surface of the distant dwarf planet Makemake. This dwarf planet is about two-thirds of the size of Pluto and travels around the Sun in a distant path that lies beyond that of Pluto, but closer to the Sun than Eris, the most massive known dwarf planet in the solar system. Scientists expected Makemake to have an atmosphere like Pluto, but this has now been shown to not be the case. // Credit: ESO/L. Calçada/Nick Risinger
The dwarf planet Makemake is about two-thirds the size of Pluto. It travels in a distant orbit that is farther from the Sun than Pluto’s but closer than that of Eris, the most massive known dwarf planet in the solar system. Previous observations of chilly Makemake have shown it to be similar to its fellow dwarf planets, leading some astronomers to expect its atmosphere, if present, to be similar to that of Pluto. However, the new study shows that, like Eris, Makemake is not surrounded by a significant atmosphere.
The team, led by Jose Luis Ortiz of the Instituto de Astrofisica de Andalucia in Spain, combined multiple observations using three telescopes at ESO's La Silla and Paranal observing sites in Chile — the Very Large Telescope (VLT), New Technology Telescope (NTT), and TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST) — with data from other small telescopes in South America to look 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,” said Ortiz. “This means that the little dwarf planet has no significant 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."
Makemake's lack of moons and its great distance from us make it difficult to study. The team's new observations add detail to astronomers’ view of Makemake: They know that it is shaped like a flattened sphere, that it is about as dense as mud, and that it reflects about as much sunlight as dirty snow.
It was only possible to observe Makemake in such detail because it passed in front of a star — an event that is known as a stellar occultation. Occultations are particularly uncommon in the case of Makemake because this solar system object moves through an area of the sky with relatively few stars. Accurately predicting and detecting these rare events is extremely difficult, and the successful observation by a coordinated observing team, scattered at many sites across South America, ranks as a major achievement.
"Pluto, Eris, and Makemake are among the larger examples of the numerous icy bodies orbiting far away from our Sun," said Ortiz. "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."