Makemake is a dwarf planet and perhaps the largest Kuiper belt object in the classical
population, with a diameter that is about 2/3 the size of Pluto. Makemake has no known
satellites, which makes it unique among the largest KBOs and means that its mass can only
be estimated. Its extremely low average temperature, about 30 K, means its surface is covered
with methane, ethane, and possibly nitrogen ices.
Initially known as 2005 FY9 and later given the minor-planet number 136472, it was discovered
on March 31, 2005, by a team led by Michael Brown, and announced on July 29, 2005. Makemake
was recognized as a dwarf planet by the International Astronomical Union in July 2008. Its name
derives from Makemake in the mythology of the Rapanui people of Easter Island.
Discovery Makemake was discovered on March 31, 2005,
by a team at the Palomar Observatory, led by Michael Brown, and was announced to the
public on July 29, 2005. The team had planned to delay announcing their discoveries of the
bright objects Makemake and Eris until further observations and calculations were complete,
but announced them both on July 29 when the discovery of another large object they had
been tracking, Haumea, was controversially announced on July 27 by a different team in
Spain. Despite its relative brightness, Makemake
was not discovered until well after many much fainter Kuiper belt objects. Most searches
for minor planets are conducted relatively close to the ecliptic, due to the greater
likelihood of finding objects there. It probably escaped detection during the earlier surveys
due to its relatively high orbital inclination, and the fact that it was at its farthest distance
from the ecliptic at the time of its discovery, in the northern constellation of Coma Berenices.
Besides Pluto, Makemake is the only other dwarf planet that was bright enough for Clyde
Tombaugh to have possibly detected during his search for trans-Neptunian planets around
1930. At the time of Tombaugh's survey, Makemake was only a few degrees from the ecliptic,
near the border of Taurus and Auriga, at an apparent magnitude of 16.0. This position,
however, was also very near the Milky Way, and Makemake would have been almost impossible
to find against the dense background of stars. Tombaugh continued searching for some years
after the discovery of Pluto, but he failed to find Makemake or any other trans-Neptunian
objects. Name
The provisional designation 2005 FY9 was given to Makemake when the discovery was made public.
Before that, the discovery team used the codename "Easterbunny" for the object, because of its
discovery shortly after Easter. In July 2008, in accordance with IAU rules
for classical Kuiper belt objects, 2005 FY9 was given the name of a creator deity. The
name of Makemake, the creator of humanity and god of fertility in the mythos of the
Rapanui, the native people of Easter Island, was chosen in part to preserve the object's
connection with Easter. Orbit and classification
Makemake is currently 52.3 AU from the Sun, almost as far from the Sun as it ever reaches
on its orbit. Makemake follows an orbit very similar to that of Haumea: highly inclined
at 29° and a moderate eccentricity of about 0.16. Nevertheless, Makemake's orbit is slightly
farther from the Sun in terms of both the semi-major axis and perihelion. Its orbital
period is nearly 310 years, more than Pluto's 248 years and Haumea's 283 years. Both Makemake
and Haumea are currently far from the ecliptic—the angular distance is almost 29°. Makemake
is approaching its 2033 aphelion, while Haumea passed its aphelion in early 1992.
Makemake is a classical Kuiper belt object, which means its orbit lies far enough from
Neptune to remain stable over the age of the Solar System. Unlike plutinos, which can cross
Neptune's orbit due to their 2:3 resonance with the planet, the classical objects have
perihelia further from the Sun, free from Neptune's perturbation. Such objects have
relatively low eccentricities and orbit the Sun in much the same way the planets do. Makemake,
however, is a member of the "dynamically hot" class of classical KBOs, meaning that it has
a high inclination compared to others in its population. Makemake is, probably coincidentally,
near the 11:6 resonance with Neptune. Physical characteristics
Brightness, size, and rotation
Makemake is currently visually the second-brightest Kuiper belt object after Pluto, having a March
opposition apparent magnitude of 16.7 in the constellation Coma Berenices. This is bright
enough to be visible using a high-end amateur telescope. Combining the detection in infrared
by the Spitzer Space Telescope and Herschel Space Telescope with the similarities of spectrum
with Pluto yielded an estimated diameter from 1,360 to 1,480 km. From the 2011 stellar
occultation by Makemake, its diameter has been measured to be × km. This is slightly
larger than Haumea, making Makemake likely the third largest known trans-Neptunian object
after Eris and Pluto. Makemake was the fourth dwarf planet recognized, as it has a bright
V-band absolute magnitude of −0.44 that practically guarantees it is large enough
to achieve hydrostatic equilibrium.
Makemake's high geometrical albedo of 77 percent suggests an average surface temperature of
about 32–36 K. Spectra and surface
In a letter written to the journal Astronomy and Astrophysics in 2006, Licandro et al.
reported the measurements of the visible and near-infrared spectrum of Makemake. They used
the William Herschel Telescope and Telescopio Nazionale Galileo and showed that the surface
of Makemake resembles that of Pluto. Like Pluto, Makemake appears red in the visible
spectrum, and significantly redder than the surface of Eris. The near-infrared spectrum
is marked by the presence of the broad methane absorption bands. Methane is observed also
on Pluto and Eris, but its spectral signature is much weaker.
Spectral analysis of Makemake's surface revealed that methane must be present in the form of
large grains at least one centimetre in size. In addition, large amounts of ethane and tholins
may be present as well, most likely created by photolysis of methane by solar radiation.
The tholins are probably responsible for the red color of the visible spectrum. Although
evidence exists for the presence of nitrogen ice on its surface, at least mixed with other
ices, there is nowhere near the same level of nitrogen as on Pluto and Triton, where
it composes more than 98 percent of the crust. The relative lack of nitrogen ice suggests
that its supply of nitrogen has somehow been depleted over the age of the Solar System.
The far-infrared and submillimeter photometry performed by Spitzer and Herschel telescopes
revealed that the surface of Makemake is not homogeneous. While the majority of it is covered
by nitrogen and methane ices, where the albedo ranges from 78 to 90%, there are small patches
of dark terrain whose albedo is only 2 to 12%, and which make up 3–7% of the surface.
Atmosphere Makemake was expected to have an atmosphere
similar to that of Pluto but with a lower surface pressure. However, on 23 April 2011
astronomers had an opportunity to analyze its atmosphere as it passed in front of an
18th-magnitude star and abruptly blocked its light. The results showed that Makemake presently
lacks a substantial atmosphere and placed an upper limit of 4–12 nanobar for the pressure
at its surface. The presence of methane and possibly nitrogen
suggests that Makemake could have a transient atmosphere similar to that of Pluto near its
perihelion. Nitrogen, if present, will be the dominant component of it. The existence
of an atmosphere also provides a natural explanation for the nitrogen depletion: because the gravity
of Makemake is weaker than that of Pluto, Eris and Triton, a large amount of nitrogen
was probably lost via atmospheric escape; methane is lighter than nitrogen, but has
significantly lower vapor pressure at temperatures prevalent at the surface of Makemake, which
hinders its escape; the result of this process is a higher relative abundance of methane.
Lack of satellites
No satellites have been detected around Makemake so far. A satellite having a brightness 1%
of that of the primary would have been detected if it had been at the distance 0.4 arcseconds
or further from Makemake. This contrasts with other large trans-Neptunian objects, most
of which have at least one satellite: Eris has one, Haumea has two and Pluto has five,
though 2007 OR10 also has no known satellites. 10% to 20% of all trans-Neptunian objects
are expected to have one or more satellites. Because satellites offer a simple method to
measure an object's mass, the lack of a satellite makes obtaining an accurate figure for Makemake's
mass more difficult. See also
Astronomical naming conventions Clearing the neighbourhood
Planets beyond Neptune International Astronomical Union
Notes
References
External links MPEC listing for Makemake
AstDys orbital elements Orbital simulation from JPL / Ephemeris
Press release from WHT and TNG on Makemake's similarity to Pluto.
Makemake chart and Orbit Viewer Precovery image with the 1.06 m Kleť Observatory
telescope on April 20, 2003 Makemake as seen on 2010-02-18 UT with the
Keck 1 Makemake of the Outer Solar System APOD July
15, 2008 Simulation of Makemake's orbit
Dwarf Planet Makemake Lacks Atmosphere