Makemake, a dwarf planet far beyond Pluto in the Kuiper Belt, has a moon.
Imagery obtained by the Hubble Space Telescope detected the satellite last April, according to a recently published paper.
The moon, which has been temporarily catalogued as S/2015 (136472) 1 and nicknamed MK2, is about 100 miles in diameter. It was observed orbiting Makemake from a distance of about 13,000 miles.
MK2 probably orbits Makemake in an orientation that makes it difficult for astronomers to observe the moon.
“Our preliminary estimates show that the moon’s orbit seems to be edge-on, and that means that often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake,” Dr. Alex H. Parker, a planetary scientist at Southwest Research Institute in Boulder, Colo., said.
Parker led the team that analyzed the Hubble image of MK2.
One implication of the Makemakean moon’s discovery is an increased ability to measure Makemake’s mass and density.
To measure the dwarf planet’s mass, scientists will need to overcome the challenges inherent in observing MK2’s orbit. If they succeed in doing so, and because the distance from Earth to Makemake is already known, it would be possible to use the orbital period and the mean distance of MK2 from Makemake to determine Makemake’s mass.
To determine Makemake’s density, scientists must know its volume, which in turn requires knowledge of the dwarf planet’s diameter. Makemake’s diameter is about 1,500 kilometers.
Once the volume is determined, density can be calculated by dividing Makemake’s mass by its volume.
Astronomers used a camera on the Hubble Space Telescope to find MK2. That instrument, called Widefield Camera 3, is able to capture images across the radiation spectrum.
Widefield Camera 3 has a 16 megapixel capacity and can capture an image as large as 160 arcseconds by 160 arcseconds in size.
Makemake is the second-brightest object, after Pluto, in the Kuiper Belt and is, like Pluto, covered with methane ice.
The dwarf planet, which was discovered in 2005, is named for a deity that is worshiped by native people of Easter Island.
In addition to Makemake, there are four other dwarf planets in the solar system: Pluto, Eris, Haumea, and Ceres.
With the discovery of MK2, astronomers now know that all of the solar system’s dwarf planets have moons.
NASA has chosen three possible small objects in the region of space beyond Neptune that could serve as destinations for the New Horizons probe after it visits the dwarf planet Pluto.
The agency used the Hubble Space Telescope to select three Kuiper Belt objects, each only a tiny fraction the size of Pluto and ranging in size from 25-55 kilometers. All three KBOs are about one billion miles beyond Pluto.
New Horizons will visit the Pluto system next summer. After doing so, the spacecraft will continue to travel deeper into the farthest reaches of the solar system, where objects have remained frozen since the formation of the planets and dwarf planets billions of years ago.
New Horizons was launched on Jan. 19, 2006. By the time it reaches the three potential KBOs found by the Hubble Space Telescope, it will have traveled about four billion miles from the sun.
The New Horizons spacecraft won’t arrive in the vicinity of Pluto until 2015, but it is close enough now to obtain images of some Kuiper Belt objects.
NASA has released images of Charon, Pluto’s largest moon, taken by New Horizons earlier this month. The images of Charon are somewhat fuzzy because the spacecraft is still about 550 million miles (900 million kilometers) away from Pluto, which is farther away from the dwarf planet than Earth is from Jupiter. From the perspective of the spacecraft, Charon’s location is about 0.01 degrees from Pluto.
Nevertheless, the detail they provide about Charon is a significant improvement over that obtained from Earth-based observation.
“The image itself might not look very impressive to the untrained eye, but compared to the discovery images of Charon from Earth, these ‘discovery’ images from New Horizons look great!”, Hal Weaver, a New Horizons project scientist affiliated with The Johns Hopkins University Applied Physics Laboratory said. “We’re very excited to see Pluto and Charon as separate objects for the first time from New Horizons.”
The photographs were obtained by the spacecraft’s Long Range Reconnaissance Imager in less than one second.
Charon is not Pluto’s only satellite. However, the images obtained by LORRI (an acronym for New Horizons’ photographic apparatus) indicate just how tiny the other moons of Pluto are. Pluto is about 2,300 kilometers across and Charon is about half that large (1,200 kilometers). None of the other moons of Pluto exceed about 170 kilometers across. Some may be as small as 10 kilometers (that’s about 6.2 miles) across!
This composite image of Charon is an amalgamation of six images. Pluto is the bright object near the center of the frame, while Charon is the dimmer object to the upper left of Pluto. Image courtesy NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute.
New Horizons is beyond the orbit of Uranus and is traveling at a velocity of about 15 kilometers per second. That’s about 32,000 miles per hour! Despite that amazing speed, the spacecraft won’t arrive at Pluto until July 2015. By the time it gets there it will have been traveling in the cosmos for about nine and one-half years.
If that causes you to wonder just how big the solar system is, it should. Think of it this way: the solar system is so enormous that even the two Voyager spacecraft that were launched 36 years ago, which are still moving as fast as New Horizons is, have not yet left it.