Misc
A Visual Introduction to the Dwarf Planets in our Solar System
Pluto and the Introduction of Dwarf Planets
Since its discovery in 1930, Pluto has been a bit of a puzzle.
For starters, not only is Pluto smaller than any other planet in the solar system, but it’s also smaller than Earth’s moon. It also has an extremely low gravitational pull at only 0.07 times the mass of the objects in its orbit, which is just a fraction of the Moon’s own strength.
At the same time, Pluto’s surface resembles that of terrestrial planets such as Mars, Venus or the Earth, yet its nearest neighbors are the gaseous Jovian planets such as Uranus or Neptune. In fact, Pluto’s orbit is so erratic that it led many scientists to initially believe that it originated elsewhere in space and the Sun’s gravity pulled it in.
These qualities have challenged the scientific view of Pluto’s status as a planet for years. It wasn’t until the discovery of Eris in 2005, one of many increasingly identified trans-Neptunian objects (objects beyond the planet Neptune), that the International Astronomical Union (IAU) defined criteria for classifying planets.
With Eris and other trans-Neptunian objects sharing similar characteristics with Pluto, the definition for dwarf planets was created, and Pluto got downgraded in 2006.
So what are dwarf planets, how do they differ from “true” planets and what are their characteristics?
The History of Dwarf Planets
A dwarf planet is a celestial body that almost meets the definition of a “true” planet. According to the IAU, which sets definitions for planetary science, a planet must:
- Orbit the Sun.
- Have enough mass to achieve hydrostatic equilibrium and assume a nearly round shape.
- Dominate its orbit and not share it with other objects.
Dwarf planets, along with not being moons or satellites, fail to clear the neighborhoods around their orbits. This is the primary reason why Pluto lost its status: because it shares part of its orbit with the Kuiper belt, a dense region of icy space bodies.
Based on this definition, the IAU has recognized five dwarf planets: Pluto, Eris, Makemake, Haumea, and Ceres. There are four more planetary objects*, namely Orcus, Sedna, Gonggong and Quaoar, that the majority of the scientific community recognize as dwarf planets.
Six more could be recognized in the coming years, and as many as 200 or more are hypothesized to exist in the Outer Solar System in the aforementioned Kuiper belt.
Ceres is the earliest known and smallest of the current category of dwarf planets. Previously classified as an asteroid in 1801, it was confirmed to be a dwarf planet in 2006. Ceres lies between Mars and Jupiter in the asteroid belt, and it is the only dwarf planet that orbits closest to Earth.
Here is a brief introduction to the most recognized dwarf planets:
Name | Region of the Solar System | Orbital period (in years) | Mean orbital speed (km/s) | Diameter (km) | Diameter relative to the Moon | Moons |
---|---|---|---|---|---|---|
Orcus | Kuiper belt (plutino) | 247 | 4.75 | 910 | 26% | 1 |
Ceres | Asteroid belt | 4.6 | 17.9 | 940 | 27% | 0 |
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 |
Eris | Scattered disc | 558 | 3.62 | 2326 | 67% | 1 |
Sedna | Detached | ~11,400 | ~1.3 | 995 | 29% | N/A |
Interesting Facts about Dwarf Planets
Here are a few interesting facts about the dwarf planets discovered in our solar system:
Ceres loses 6kg of its mass in steam every second
The Herschel Space Telescope observed plumes of water vapor shooting up from Ceres’ surface; this was the first definitive observation of water vapor in the asteroid belt. This happens when portions of Ceres’ icy surface warm up and turn into steam.
A day on Haumea lasts 3.9 hours
Haumea has a unique appearance due to its rotation, which is so rapid that it compresses the planet into an egg-like shape. Its rotational speed and collisional origin also make Haumea one of the densest dwarf planets discovered to date.
Makemake was named three years after its discovery in 2005
Makemake’s discovery close to Easter influenced both its name and nickname. Before being named after the creator of humanity and god of fertility in the mythos of the Rapa Nui (the native people of Easter Island), Makemake was nicknamed “Easter bunny” by its discoverer Mike Brown.
Eris was once considered for the position of the 10th planet
Eris is the most massive dwarf planet in the solar system, exceeding Pluto’s mass by 28%. As such, it was a serious contender to become the tenth planet but failed to meet the criteria set out by the IAU.
Pluto is one-third ice
The planet’s composition makes up two-thirds rock and one-third ice, mostly a mixture of methane and carbon dioxide. One day on Pluto is 153.6 hours, approximately 6.4 Earth days, making it one of the slowest rotating dwarf planets.
Exploratory Missions and New Planets on the Horizon
With newer technology rapidly available to the scientific community and new exploratory missions getting more data and information about trans-Neptunian objects, our understanding of dwarf planets will increase.
Nestled in the asteroid belt between Mars and Jupiter, the asteroid Hygiea remains a controversy. Hygiea is the fourth largest object in the asteroid belt behind Ceres, Vesta, and Pallas and ticks all the boxes necessary to be classified as a dwarf planet.
So what’s holding back Hygiea’s confirmation as a dwarf planet? The criterion for being massive enough to form a spherical shape is in contention; it remains unclear if its roundness results from collision/impact disruption or its mass/gravity.
Along with Hygiea, other exciting dwarf planets could be soon discovered. Here is a quick rundown of some serious contenders:
120347 Salacia
Discovered in 2004, it is a trans-Neptunian object in the Kuiper belt, approximately 850 kilometers in diameter. As of 2018, it is located about 44.8 astronomical units from the Sun. Salacia’s status is in contention because its planetary density is arguable. It is uncertain if it can exist in hydrostatic equilibrium.
(307261) 2002 MS4
With an estimated diameter of 934±47 kilometers, 2002 MS4 is comparable in size to Ceres. Researchers need more data to determine whether 2002 MS4 is a dwarf planet or not.
(55565) 2002 AW197
Discovered at the Palomar Observatory in 2002, it has a rotation period of 8.8 hours, a moderately red color (similar to Quaoar) and no apparent planetary geology. Its low albedo has made it difficult to determine whether or not it is a dwarf planet.
174567 Varda
Varda takes its name after the queen of the Valar, creator of the stars, one of the most powerful servants of almighty Eru Iluvatar in J. R. R. Tolkien’s fictional mythology. Varda’s status as a dwarf planet is uncertain because its size and albedo suggest it might not be a fully solid body.
(532037) 2013 FY27
This space object has a surface diameter of about 740 kilometers. It orbits the Sun once every 449 years. Researchers need more data on the planet’s mass and density to determine if it is a dwarf planet or not.
(208996) 2003 AZ84
It is approximately 940 kilometers across its longest axis, as it has an elongated shape. This shape is presumably due to its rapid rotation rate of 6.71 hours, similar to that of other dwarf planets like Haumea. Like Varda, it remains unknown if this object has compressed into a fully solid body and thus remains contentious amongst astronomers regarding its planetary status.
*Note: The IAU officially recognizes five dwarf planets. We include four additional dwarf planets widely acknowledged by members of the scientific community, especially amongst leading planetary researchers like Gonzalo Tancredi, Michael Brown, and William Grundy. There are many more potential dwarf planets not listed here that remain under investigation.
Demographics
Mapped: Population Growth by Region (1900-2050F)
In this visualization, we map the populations of major regions at three different points in time: 1900, 2000, and 2050 (forecasted).
Mapping Population Growth by Region
This was originally posted on our Voronoi app. Download the app for free on iOS or Android and discover incredible data-driven charts from a variety of trusted sources.
In fewer than 50 years, the world population has doubled in size, jumping from 4 to 8 billion.
In this visualization, we map the populations of major regions at three different points in time: 1900, 2000, and 2050 (forecasted). Figures come from Our World in Data as of March 2023, using the United Nations medium-fertility scenario.
Population by Continent (1900-2050F)
Asia was the biggest driver of global population growth over the course of the 20th century. In fact, the continent’s population grew by 2.8 billion people from 1900 to 2000, compared to just 680 million from the second on our list, Africa.
Region | 1900 | 2000 | 2050F |
---|---|---|---|
Asia | 931,021,418 | 3,735,089,775 | 5,291,555,919 |
Africa | 138,752,199 | 818,952,374 | 2,485,135,689 |
Europe | 406,610,221 | 727,917,165 | 704,398,730 |
North America | 104,231,973 | 486,364,446 | 679,488,449 |
South America | 41,330,704 | 349,634,344 | 491,078,697 |
Oceania | 5,936,615 | 31,223,133 | 57,834,753 |
World 🌐 | 1,627,883,130 | 6,149,181,237 | 9,709,492,237 |
China was the main source of Asia’s population expansion, though its population growth has slowed in recent years. That’s why in 2023, India surpassed China to become the world’s most populous country.
Southeast Asian countries like the Philippines and Indonesia have also been big drivers of Asia’s population boom to this point.
The Future: Africa to Hit 2.5 Billion by 2050
Under the UN’s medium-fertility scenario (all countries converge at a birthrate of 1.85 children per woman by 2050), Africa will solidify its place as the world’s second most populous region.
Three countries—Nigeria, Ethiopia, and Egypt—will account for roughly 30% of that 2.5 billion population figure.
Meanwhile, both North America and South America are expected to see a slowdown in population growth, while Europe is the only region that will shrink by 2050.
A century ago, Europe’s population was close to 30% of the world total. Today, that figure stands at less than 10%.
-
Money6 days ago
Visualizing All of the U.S. Currency in Circulation
-
Money2 weeks ago
Wealth Needed to Join the Top 1%, by Country
-
Stocks2 weeks ago
Ranked: South Korea’s Largest Companies by Market Capitalization
-
VC+2 weeks ago
What’s New on VC+ in March?
-
Markets2 weeks ago
Confidence in the Global Economy, by Country
-
Wealth1 week ago
Mapped: Where Do the Wealthiest People in the World Live?
-
Misc1 week ago
Ranked: Global Airlines with the Most Plane Crashes
-
Technology1 week ago
Visualizing iPhone 15 Production by Manufacturer in 2023