A Visual Introduction to the Dwarf Planets in our Solar System
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A Visual Introduction to the Dwarf Planets in our Solar System



A Visual Introduction to the Dwarf Planets of our Solar SystemA Visual Introduction to the Dwarf Planets of 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:

  1. Orbit the Sun.
  2. Have enough mass to achieve hydrostatic equilibrium and assume a nearly round shape.
  3. 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:

NameRegion of the
Solar System
Orbital period
(in years)
Mean orbital
speed (km/s)
relative to
the Moon
OrcusKuiper belt (plutino)2474.7591026%1
CeresAsteroid belt4.617.994027%0
PlutoKuiper belt (plutino)2484.74237768%5
HaumeaKuiper belt (12:7)2854.531560≈ 45%2
QuaoarKuiper belt (cubewano)2894.51111032%1
MakemakeKuiper belt (cubewano)3064.41143041%1
GonggongScattered disc (10:3)5543.63123035%1
ErisScattered disc5583.62232667%1

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:

Potential Dwarf Planets Under Investigation

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.

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Mapped: Second Primary Languages Around the World

This fascinating map highlights the second most commonly spoken primary language in almost nearly every country.



Second Languages Around the World Shareable

Mapped: Second Primary Languages Around the World

After the primary language, what second languages are used as native tongues in your country?

The answer reveals a lot about history and location. Whether through immigration, colonization, or local culture, a primary language can either spread around the world or remain rooted in place.

This map from MoveHub shows the second most commonly spoken primary language in most countries, using data from the CIA World Factbook and Wikipedia as of February 2021.

The Difference Between Primary and Secondary Languages

First, it’s important to differentiate between primary languages and secondary languages.

A primary language—also known as a first or native language—is the language we use most frequently to communicate. These are languages we are usually born with, have a lot of exposure to, and use at home.

On the other hand, a secondary language is one we learn or pick up after our primary language. In many countries, English is the most commonly learned, with close to 1 billion speakers.

But a map of common second languages can simply show just how many countries prioritize learning English, the de-facto international language in many organizations. Instead, this map highlights the movement of people by showing the second-most common primary language.

The Second Most Common Primary Languages by Country

Even when filtering by primary language use, however, English and other Indo-European languages dominate the world.

With 55 countries speaking it as the second-most common primary language, English came out on top.

Top 10 Most Popular Second Primary LanguagesNumber of Countries

The use of English as a second primary language was primarily concentrated in Western Europe, Northern Africa, and Southeast Asia and Oceania.

Similarly to second-place French with 14 countries and third-place Russian with 13 countries, English was most common in proximity to English-speaking countries or where there was a history of immigration.

Other second-most common primary languages highlighted different cultures within countries, such as China’s second-most common language Cantonese. Alternatively, they showed the primary indigenous language before colonization, such as the Quechua languages in South America.

What other interesting or surprising language patterns can you spot in the map above?

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Mapped: Human Impact on the Earth’s Surface

This detailed map looks at where humans have (and haven’t) modified Earth’s terrestrial environment. See human impact in incredible detail.



human impact on earths surface

Mapped: Human Impact on the Earth’s Surface

With human population on Earth approaching 8 billion (we’ll likely hit that milestone in 2023), our impact on the planet is becoming harder to ignore with each passing year.

Our cities, infrastructure, agriculture, and pollution are all forms of stress we place on the natural world. This map, by David M. Theobald et al., shows just how much of the planet we’ve now modified. The researchers estimate that 14.6% or 18.5 million km² of land area has been modified – an area greater than Russia.

Defining Human Impact

Human impact on the Earth’s surface can take a number of different forms, and researchers took a nuanced approach to classifying the “modifications” we’ve made. In the end, 10 main stressors were used to create this map:

  1. Built-Up Areas: All of our cities and towns
  2. Agriculture: Areas devoted to crops and pastures
  3. Energy and extractive resources: Primarily locations where oil and gas are extracted
  4. Mines and quarries: Other ground-based natural resource extraction, excluding oil and gas
  5. Power plants: Areas where energy is produced – both renewable and non-renewable
  6. Transportation and service corridors: Primarily roads and railways
  7. Logging: This measures commodity-based forest loss (excludes factors like wildfire and urbanization)
  8. Human intrusion: Typically areas adjacent to population centers and roads that humans access
  9. Natural systems modification: Primarily modifications to water flow, including reservoir creation
  10. Pollution: Phenomenon such as acid rain and fog caused by air pollution

The classification descriptions above are simplified. See the methodology for full descriptions and calculations.

A Closer Look at Human Impact on the Earth’s Surface

To help better understand the level of impact humans can have on the planet, we’ll take a closer look three regions, and see how the situation on the ground relates to these maps.

Land Use Contrasts: Egypt

Almost all of Egypt’s population lives along the Nile and its delta, making it an interesting place to examine land use and human impact.

egypt land use impact zone

The towns and high intensity agricultural land following the river stand out clearly on the human modification map, while the nearby desert shows much less impact.

Intensive Modification: Netherlands

The Netherlands has some of the heavily modified landscapes on Earth, so the way it looks on this map will come as no surprise.

netherlands land use impact zone

The area shown above, Rotterdam’s distinctive port and surround area, renders almost entirely in colors at the top of the human modification scale.

Resource Extraction: West Virginia

It isn’t just cities and towns that show up clearly on this map, it’s also the areas we extract our raw materials from as well. This mountainous region of West Virginia, in the United States, offers a very clear visual example.

west virginia land use impact zone

The mountaintop removal method of mining—which involves blasting mountains in order to retrieve seams of bituminous coal—is common in this region, and mine sites show up clearly in the map.

You can explore the interactive version of this map yourself to view any area on the globe. What surprises you about these patterns of human impact?

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