DWARF PLANETS IN OUR SOLAR SYSTEMS

There are 5 officially recognized dwarf planets in our solar system; they are Ceres, Pluto, Haumea, Makemake and Eris. With exception of Ceres, which is located in the asteroid belt, the other dwarf planets are found in the outer solar system. There are another 6 objects in our solar system that are almost certainly dwarf planets and there are as many as 10000. Of the dwarf planets only 2 have been visited by space probes, in 2015 NASA’s Dawn and New Horizons missions reached Ceres and Pluto respectively.

WHAT IS DWARF PLANET?

A dwarf planet is a planetary-mass object that is neither a planet nor a natural satellite. The International Astronomical Union’s definition of a dwarf planet is:

A “dwarf planet” is a celestial body that

• is in orbit around the Sun,
• has sufficient mass for its self-gravity to overcome rigid body forces, so that it assumes a hydro static equilibrium (nearly round) shape,
• has not cleared, the neighborhood around its orbit, and
• is not a satellite.The key difference is that a planet has cleared other objects in the area of its orbit, while a dwarf planet has not.

The largest dwarf planet in the solar system is Pluto followed by Eris, Makemake, Haumea with the smallest being Ceres. The order of dwarf planet from closest to Sun outwards is Ceres, Pluto, Haumea, Makemake and with the Eris being the farthest from the Sun.

HISTORY

Starting in 1801, astronomers discovered Ceres and the other bodies between the Mars and Jupiter which were for decades considered as a planet. Between then and around 1851, when the numbers of planet had reached 23, astronomers started using the word asteroid for the small bodies. With the discovery of Pluto in 1930, most astronomers considered Solar System to have 9 planets. For almost 50 years Pluto was thought to be larger than Mercury, but with the discovery of Pluto’s moon Charon, it was determined that mass of Pluto was much smaller than initial estimate. It was roughly one-twentieth the mass of Mercury. Furthermore, having some unusual characteristics, such as larger orbital eccentricity and a high orbital inclination, it became evident that Pluto was a different kind of body from any of the other planets.

Eris (then known as 2003UB313) was discovered in January 2005; it was thought to be slightly greater than Pluto, and some reports informally referred to it as the 10th planet. The issue became matter of intense debate during a IAU general assembly in August 2006. The IAU’s initial draft proposal included Pluto, Charon, Eris and Ceres in the list of planets. After all astronomer objected to this proposal, an alternative drawn up by Uruguayan astronomer Julio Angel Fernandez: He proposed an intermediate category for objects large enough to be round, but had not cleared their objects of planetesimals. Dropping Charon from the list, the new proposal also removed Pluto, Ceres and Eris, because they have not cleared their orbits. Thus the IAU resolves that planets and the other bodies except satellites, in our solar system be defined into 3 distinct categories. By this problem regarding to dwarf planet was solved.

EXPLORATION

On March 6, 2015, the ‘Dawn’ Spacecraft began to orbit Ceres, becoming the first Spacecraft to orbit of a dwarf planet. On July 14, 2015 the ‘New Horizons’ space probe flew by Pluto and its 5 moons. Dawn has also explored the former dwarf planet Vesta. This exploration helps in the study of the evolution of dwarf planet.

PLUTO

Pluto was discovered in 1830 by an astronomer from the United States. An astronomer Clyde W. Tombaugh discovered Pluto on February 18th 1930. Pluto was known as the smallest planet in the solar system and the ninth planet from the Sun.

But today Pluto is known as ‘dwarf planet’. A dwarf planet orbits the Sun just like other planets, but it is smaller. A dwarf planet is so small it cannot clear other objects out of its path.

Pluto is in the region called Kuiper (KY-per) Belt. Thousands of small, icy objects like Pluto are in the Kuiper belt. Pluto is only 1400 miles wide. That about half the width of the united states Pluto is slightly smaller than Earth’s moon. It takes Pluto 248 years to go around the Sun. One day on Pluto is about 6.5 days on the earth.

Pluto is called as Plutoid. A Plutoid is a dwarf planet that is farther out in space than the planet Neptune. The three known Plutoids are Pluto, Eris and Makemake. Astronomers used telescope to discover new objects like Plutoids scientists are learning more about the universe and the Earth’s place in it.

Pluto is very cold. The Pluto is far from Earth that scientist known very little temperature. Pluto is probably covered with ice. Pluto has about one-fifteenth the gravity of earth. A person who weighs 400 pounds in earth would weigh only 7 pounds on Pluto.

NASA learns about Pluto from pictures taken with telescopes. Pictures from Hubble space telescope helped scientists to find the four light areas on Pluto. Pluto is so far away that even pictures taken by telescope area little fazzy.

In 2006, NASA launched the first mission to Pluto’ New Horizon’. New Horizon is the space craft that is going to the edge of the solar system. This space craft is about the size of piano. It was 9 years trip. In 2015, New Horizon arrived at Pluto. New Horizon has cameras that will take pictures of Pluto. These pictures and information will help scientists to learn more about dwarf planet.

Pluto having one-third of water. This is in the form of water ice which is more than 3 times as much water as in all the earth’s ocean, the remaining two-third are rock.

Pluto’s location was predicted by Percival Lowell in 1915. When Pluto’s elliptical orbit takes it closer to the Sun, its surface ice melts and forms a thin atmosphere primarily of nitrogen which slowly escapes the planet. It also has methane. The methane is dissociated by sunlight when a Pluto travels away from the Sun. When Pluto travels away from the atmosphere then freezes back to its solid state.

Diameter - 2372 km

Mass - 1.31*1022 kg (0.17 moons)

Orbit Distance - 39.2 AU

Orbit Period - 248 years

Surface Temperature - 229 degree C

CERES

Ceres is the closest dwarf planet to the sun and is located in asteroid belt, between Mars and Jupiter, making it the only dwarf planet in the inner solar system. Ceres is the smallest of the bodies current classified as dwarf planets with a diameter of 950km. Ceres was the first asteroid to be discovered by Giuseppe Pazzi at Palermo on 1st January 1801. It was originally considered as planet, but was reclassified as an asteroid in the1850’s after many other objects in the similar orbits was discovered.

Dawn is a space probe launched by NASA in September 2007 with the mission of studying dwarf planet Ceres with the other protoplanets of the asteroid belt and Vesta.

Ceres is the largest known asteroid in the asteroid belt until 2006. In 2006, the IAU formed a new class of solar system objects known as dwarf planets. By the definition a dwarf planet is spherical and travels in an orbit around the Sun. Ceres fit the definition perfectly. Hence it is considered as a dwarf planet.

The surface is probably a mixture of water-ice and various hydrated minerals such as carbonates and clay. Ceres appears to be differentiated in to a rocky core and an icy mantle, and may have a remnant internal ocean of liquid water under the layer of ice. Ceres has a tenuous water vapor atmosphere out-gassing from water-ice on the surface.

Ceres was the first object considered to be an asteroid. The first visit to Ceres is due in 2015. NASA’s Dawn spacecraft has been making its way to Ceres from the asteroid Vesta since September 2012. There is a high interest in this mission and is one possible destination for human colonization gives its abundance of ice, water and minerals.

Ceres has a mysterious white spot. This can be seen in both the old Hubble images and the more recent photos taken by Dawn spacecraft on its approach.

Every second Ceres loses 6 kg of its mass in steam. Plums of water vapor shooting up from Ceres surface were observed by the Herschel Space Telescope. This was the first definitive observation of water vapor in the asteroid belt.

Ceres accounts for one-third of the mass in the asteroid belt. For roughly the first 50 years after this discovery Ceres was frequently referred as a Planet. Ceres is the only dwarf planet with no moons. The other planets Pluto, Haumea, Makemake and Eris all have at least one moon.

HAUMEA

Haumea is the third closest dwarf planet from the Sun and is unique in its elongated shape making it the least spherical of the dwarf planets. It is spinning so quickly that it has been stretched in to the shape of an ellipsoid.

It was discovered in 28th December 2004 by a team headed by Mike Brown of Caltech and independently in 2005 by a team headed by Jose Luis Ortiz Moreno. On September 17, 2008 it was recognized as a dwarf planet by International Astronomical Union (IAU) and named after Haumea, the Hawaiian goddess of childbirth.

Haumea is a plutoid, a dwarf planet beyond Neptune’s orbit. It is classified as a dwarf planet because it is presumed to be massive enough to have been rounded by its own gravity into a shape in hydrostatic equilibrium, but not massive enough to have cleared its neighborhood of similarly sized objects.

A day in Haumea lasts 3.9 hours. Its rotational speed as well as its collision origin also makes Haumea one of the densest dwarf planets discovered to date. Haumea has a red spot, which stands for surrounding crystalline ice. Haumea is roughly one third of mass of Pluto.

Equatorial diameter - 1960 km to 1518 km

Polar diameter - 996 km

Mass - 4.01*1021 kg (0.05 moons)

Orbit distance - 6452000000 (43.13 AU)

Orbit period - 283.3years

Surface temperature - -241 degree C

Moons - 2 ( Hi’iaka and Namaka )

ERIS

Eris is the most distant dwarf planet from the Sun and has the greatest mass. Eris is the second largest dwarf planet and at one point was considered for the position of the 10th planet. Eris discovery promoted discussion that eventually leads to the classification of “Dwarf planets”.

Eris was discovered in 5th January 2005 by M. E. Brown, C.A. Trujillo and D.J. Babinowitz from images taken on October 21, 2003. The discovery was announced on July 29, 2005 the same day Makemake and two day after Haumea is declared.

Eris is unquestionably the most massive of the known dwarf planets (the largest object that is not a planet that orbits the Sun) and was once thought to be the largest due to its relative brightness. After a stellar occultation in 2010 its diameter was calculated to be smaller than previously thought and more recent measurement suggested Pluto was larger than thought making it the largest. All the objects in the Asteroid Belt could fit inside Eris. Eris is still smaller than Earth’s moon, having about two third of the moon’s diameter and one third of its volume. Eris is not always the most distant dwarf planet. At its closest point it is closer than Pluto’s most distant point.

Diameter - 2,326 km

Mass - 1.66*102 2 kg (0.23 moons)

Orbit distance - 68.01 AU

Orbit period - 560.9 years

Surface temperature - -231 degree C

Moons - 1 (Dysnomia)

MAKEMAKE

Makemake is the second farthest dwarf planet from the Sun and is the third largest dwarf planet in the solar system. Makemake was discovered on March 31st 2005 and was recognized as a dwarf planet by the International Astronomical Union (IAU) in July 2008. Until April 2016 Makemake was thought to be the only one of the four outer dwarf planets to not have any moons.

Makemake is the second brightest Kuiper Belt object after Pluto. Makemake and its moon MK2, which was spotted about 20000 km from Makemake is viewed by Hubble Space Telescope. Makemake was expected to have an atmosphere similar to that of Pluto, but in 2011 it was revealed that it mostly lacks a gas envelop. Makemake is a Kuiper Belt object; hence it remains stable over the age of the solar system since, it is not affected by the Neptune’s gravity.

Equatorial diameter - 1434 km

Polar diameter - 1422 km

Mass - 2.5*1021 kg

Orbit distance - 6850000000 km

Orbit period - 309.9 years

Surface temperature - -239 degree C

Moons - 1( MK2-5/2015(136472)1)

Collected By:

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Source: Internet