Since its discovery in 1930, Pluto has been a little bit of a puzzle.
For starters, not solely is Pluto smaller than another planet within the photo voltaic system, however it’s additionally smaller than Earth’s moon. It additionally has a particularly low gravitational pull at solely 0.07 instances the mass of the objects in its orbit, which is only a fraction of the Moon’s personal power.
At the identical time, Pluto’s floor resembles that of terrestrial planets resembling Mars, Venus or the Earth, but its nearest neighbors are the gaseous Jovian planets resembling Uranus or Neptune. In reality, Pluto’s orbit is so erratic that it led many scientists to initially imagine that it originated elsewhere in area and the Sun’s gravity pulled it in.
These qualities have challenged the scientific view of Pluto’s standing as a planet for years. It wasn’t till the invention of Eris in 2005, certainly one of many more and more recognized trans-Neptunian objects (objects past the planet Neptune), that the International Astronomical Union (IAU) outlined standards for classifying planets.
With Eris and different trans-Neptunian objects sharing related traits with Pluto, the definition for dwarf planets was created, and Pluto bought downgraded in 2006.
So what are dwarf planets, how do they differ from “true” planets and what are their traits?
The History of Dwarf Planets
A dwarf planet is a celestial physique that nearly meets the definition of a “true” planet. According to the IAU, which units definitions for planetary science, a planet should:
- Orbit the Sun.
- Have sufficient mass to attain hydrostatic equilibrium and assume an almost spherical form.
- Dominate its orbit and never share it with different objects.
Dwarf planets, together with not being moons or satellites, fail to clear the neighborhoods round their orbits. This is the first motive why Pluto misplaced its standing: as a result of it shares a part of its orbit with the Kuiper belt, a dense area of icy area our bodies.
Based on this definition, the IAU has acknowledged 5 dwarf planets: Pluto, Eris, Makemake, Haumea, and Ceres. There are 4 extra planetary objects*, specifically Orcus, Sedna, Gonggong and Quaoar, that almost all of the scientific neighborhood acknowledge as dwarf planets.
Six extra may very well be acknowledged within the coming years, and as many as 200 or extra are hypothesized to exist within the Outer Solar System within the aforementioned Kuiper belt.
Ceres is the earliest identified and smallest of the present class of dwarf planets. Previously categorized as an asteroid in 1801, it was confirmed to be a dwarf planet in 2006. Ceres lies between Mars and Jupiter within the asteroid belt, and it’s the solely dwarf planet that orbits closest to Earth.
Here is a quick introduction to essentially the most acknowledged dwarf planets:
|Name||Region of the
|Orcus||Kuiper belt (plutino)||247||4.75||910||26%||1|
|Pluto||Kuiper belt (plutino)||248||4.74||2377||68%||5|
|Haumea||Kuiper belt (12:7)||285||4.53||1560||≈ 45%||2|
|Quaoar||Kuiper belt (cubewano)||289||4.51||1110||32%||1|
|Makemake||Kuiper belt (cubewano)||306||4.41||1430||41%||1|
|Gonggong||Scattered disc (10:3)||554||3.63||1230||35%||1|
Interesting Facts about Dwarf Planets
Here are just a few attention-grabbing details concerning the dwarf planets found in our photo voltaic system:
Ceres loses 6kg of its mass in steam each second
The Herschel Space Telescope noticed plumes of water vapor taking pictures up from Ceres’ floor; this was the primary definitive statement of water vapor within the asteroid belt. This occurs when parts of Ceres’ icy floor heat up and switch into steam.
A day on Haumea lasts 3.9 hours
Haumea has a novel look on account of its rotation, which is so fast that it compresses the planet into an egg-like form. Its rotational velocity and collisional origin additionally make Haumea one of many densest dwarf planets found to this point.
Makemake was named three years after its discovery in 2005
Makemake’s discovery near Easter influenced each its identify and nickname. Before being named after the creator of humanity and god of fertility within the mythos of the Rapa Nui (the native individuals of Easter Island), Makemake was nicknamed “Easter bunny” by its discoverer Mike Brown.
Eris was as soon as thought of for the place of the tenth planet
Eris is essentially the most large dwarf planet within the photo voltaic system, exceeding Pluto’s mass by 28%. As such, it was a severe contender to turn out to be the tenth planet however failed to fulfill the factors set out by the IAU.
Pluto is one-third ice
The planet’s composition makes up two-thirds rock and one-third ice, largely a mix of methane and carbon dioxide. One day on Pluto is 153.6 hours, roughly 6.4 Earth days, making it one of many slowest rotating dwarf planets.
Exploratory Missions and New Planets on the Horizon
With newer know-how quickly out there to the scientific neighborhood and new exploratory missions getting extra information and details about trans-Neptunian objects, our understanding of dwarf planets will improve.
Nestled within the asteroid belt between Mars and Jupiter, the asteroid Hygiea stays an argument. Hygiea is the fourth largest object within the asteroid belt behind Ceres, Vesta, and Pallas and ticks all of the containers essential to be categorized as a dwarf planet.
So what’s holding again Hygiea’s affirmation as a dwarf planet? The criterion for being large sufficient to type a spherical form is in competition; it stays unclear if its roundness outcomes from collision/impression disruption or its mass/gravity.
Along with Hygiea, different thrilling dwarf planets may very well be quickly found. Here is a fast rundown of some severe contenders:
Discovered in 2004, it’s a trans-Neptunian object within the Kuiper belt, roughly 850 kilometers in diameter. As of 2018, it’s positioned about 44.8 astronomical models from the Sun. Salacia’s standing is in competition as a result of its planetary density is controversial. It is unsure if it will probably exist in hydrostatic equilibrium.
(307261) 2002 MS4
With an estimated diameter of 934±47 kilometers, 2002 MS4 is comparable in dimension to Ceres. Researchers want extra information to find out whether or not 2002 MS4 is a dwarf planet or not.
(55565) 2002 AW197
Discovered on the Palomar Observatory in 2002, it has a rotation interval of 8.8 hours, a reasonably pink colour (just like Quaoar) and no obvious planetary geology. Its low albedo has made it troublesome to find out whether or not or not it’s a dwarf planet.
Varda takes its identify after the queen of the Valar, creator of the celebrities, some of the highly effective servants of almighty Eru Iluvatar in J. R. R. Tolkien’s fictional mythology. Varda’s standing as a dwarf planet is unsure as a result of its dimension and albedo recommend it may not be a completely strong physique.
(532037) 2013 FY27
This area object has a floor diameter of about 740 kilometers. It orbits the Sun as soon as each 449 years. Researchers want extra information on the planet’s mass and density to find out if it’s a dwarf planet or not.
(208996) 2003 AZ84
It is roughly 940 kilometers throughout its longest axis, because it has an elongated form. This form is presumably on account of its fast rotation fee of 6.71 hours, just like that of different dwarf planets like Haumea. Like Varda, it stays unknown if this object has compressed into a completely strong physique and thus stays contentious amongst astronomers concerning its planetary standing.
*Note: The IAU formally acknowledges 5 dwarf planets. We embrace 4 extra dwarf planets extensively acknowledged by members of the scientific neighborhood, particularly amongst main planetary researchers like Gonzalo Tancredi, Michael Brown, and William Grundy. There are many extra potential dwarf planets not listed right here that stay underneath investigation.