Makemake

Makemake is one of the four dwarf planets that the International Astronomical Union recognises beyond Neptune, and after Pluto it is the second-brightest icy world in the Kuiper Belt. With a radius of about 715 km it is roughly 60 percent the width of Pluto, orbiting the Sun once every 305 years at an average distance of 45.8 astronomical units — far enough that even in a large telescope it shows only as a faint, slow-moving point among the stars.

It is a world of almost pure frozen methane, tinted reddish-brown by sunlight-baked organic compounds, and for years it was regarded as a quiet, static block of ice. Recent observations have started to overturn that picture, hinting that Makemake may be quietly leaking gas into space.

An Easter discovery

Makemake was first spotted on 31 March 2005 by Michael Brown, Chad Trujillo and David Rabinowitz at Palomar Observatory in California — the same survey team that turned up Eris and Haumea in the same period. Because the find came just after Easter, the team gave it the internal codename "Easterbunny" while they confirmed the orbit of the object then catalogued as 2005 FY9.

When it came time for a formal name, Brown wanted to keep the Easter link. Under the IAU's convention, classical Kuiper Belt objects are named for creation deities, so the team settled on Makemake, the creator god and fertility figure of the Rapa Nui people of Easter Island. Makemake and Haumea were formally recognised as dwarf planets in 2008, joining Pluto and Eris in that then-new category.

A world of frozen methane

Makemake's surface is dominated by frozen methane, with ethane and other hydrocarbons detected alongside it. Unlike Pluto, it has very little nitrogen or carbon monoxide to dilute that methane, so the ice stays remarkably pure and appears to have grown into unusually large grains or thick slabs — the kind of surface that reflects light strongly and gives Makemake one of the highest albedos of any large body in the outer Solar System.

The ice is not pristine white, though. Sunlight and cosmic radiation break down the methane into heavier organic molecules called tholins, which stain the surface a reddish-brown reminiscent of Pluto's darker regions. With no measured axial tilt or reliable atmosphere data to soften it, the surface endures temperatures around 30 to 35 kelvin — roughly minus 240 degrees Celsius — across most of its 22-and-a-half-hour day.

The missing atmosphere

On 23 April 2011 Makemake passed directly in front of a faint background star, and a network of telescopes across South America, including instruments at ESO's La Silla and Paranal observatories, caught the event. Rather than fading gradually as it would behind a hazy atmosphere, the star blinked out and reappeared almost instantly at Makemake's limb.

That sharp cutoff showed that Makemake has no global, Pluto-like atmosphere, with any surface pressure held to a few billionths of Earth's. The same occultation pinned down its size and shape, revealing a slightly flattened body about 1,430 by 1,500 km across — the measurements that anchor the roughly 715 km radius listed here. At its great distance from the Sun, most of Makemake's methane simply stays frozen to the ground rather than puffing up into a persistent envelope of gas.

A dark little moon

For a decade Makemake was thought to be moonless, an oddity among the large Kuiper Belt dwarfs. Then in April 2015 the Hubble Space Telescope's Wide Field Camera 3 caught a faint companion, provisionally designated S/2015 (136472) 1 and nicknamed MK 2, announced in 2016. It is roughly 160 km across and orbits some 21,000 km from Makemake, but it is more than 1,300 times fainter than its parent.

The moon had gone unnoticed because its orbit is seen nearly edge-on, so it usually hides in Makemake's glare. Curiously, MK 2 appears charcoal-black rather than icy — possibly because it is too small to hold onto a bright frost coating. Beyond its own strangeness, the moon is scientifically valuable: tracking its orbit lets astronomers weigh Makemake and pin down its density, much as the discovery of Charon once did for Pluto.

Signs of a restless surface

The old image of Makemake as an inert ice ball is now under pressure. Infrared measurements from Spitzer, Herschel and the James Webb Space Telescope have found a patch of surface far warmer than sunlight alone can explain, near 150 kelvin, hinting at some internal or localised heat source.

In 2025 a team led by the Southwest Research Institute reported the first detection of gas at Makemake, using Webb's near-infrared spectrograph to catch methane vapour above the surface. The signal points to active outgassing from a limited region — possibly sublimating ice or even cryovolcanic plumes — rather than a settled, planet-wide atmosphere. If confirmed, it would make Makemake a far more dynamic world than its frozen exterior suggests.

How to spot Makemake

Makemake is not a naked-eye object. At around 17th magnitude it is far too faint for binoculars, and even a large amateur telescope shows it only as a dim star-like point that shifts position slowly from night to night against the fixed background. It currently sits in the northern constellation Coma Berenices, high above the plane of the planets thanks to its steep 29-degree orbital tilt.

No spacecraft has ever visited Makemake, and none is planned, so everything we know comes from telescopes on and near Earth. For most observers it is best appreciated not through an eyepiece but as a set of coordinates and a slow arc across the sky — a reminder of how much of the Solar System still lies at the faint edge of what we can see.