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A Visual Introduction to the Dwarf Planets in our Solar System

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

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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)
Diameter
(km)
Diameter
relative to
the Moon
Moons
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
SednaDetached~11,400~1.399529%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:

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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Personal Finance

Mapped: The Income a Family Needs to Live Comfortably in Every U.S. State

Families in expensive states require over $270,000 annually to live comfortably.

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A map showing the income that two working adults with two children need to live comfortably in each U.S. state.

The Income a Family Needs to Live Comfortably in Every U.S. State

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.

Families in the top five most expensive U.S. states require an annual income exceeding $270,000 to live comfortably.

This visualization illustrates the income necessary for two working adults with two children to maintain a comfortable lifestyle in each state.

“Comfortable” is defined as the income needed to cover a 50/30/20 budget, with 50% allocated to necessities like housing and utilities, 30% to discretionary spending, and 20% to savings or investments.

The calculations for family income needed in each state were done by SmartAsset, using the cost of necessities sourced from the MIT Living Wage Calculator, last updated on Feb. 14, 2024.

Massachusetts Tops the List

Massachusetts is the most expensive state to live comfortably in, requiring a total family income of about $301,184. Hawaii ($294,611) comes in second, followed by Connecticut ($279,885).

Housing is one main reason Massachusetts is an expensive state to live in, particularly in the Boston area. In addition, the state also has a high cost of living, including expenses such as healthcare and utilities.

RankStateIncome for 2 working adults raising 2 children
1Massachusetts$301,184
2Hawaii$294,611
3Connecticut$279,885
4New York$278,970
5California$276,723
6Colorado$264,992
7Washington$257,421
8Oregon$257,338
9New Jersey$251,181
10Rhode Island$249,267
11Vermont$248,352
12Minnesota$244,774
13New Hampshire$244,109
14Alaska$242,611
15Maryland$239,450
16Nevada$237,286
17Virginia$235,206
18Illinois$231,962
19Arizona$230,630
20Pennsylvania$230,464
21Maine$229,549
22Delaware$228,966
23Wisconsin$225,056
24Utah$218,483
25Michigan$214,490
26Nebraska$213,075
27Georgia$212,826
28Montana$211,411
28Iowa$211,411
30Idaho$211,245
31North Carolina$209,331
31Ohio$209,331
33Florida$209,082
34Indiana$206,003
35New Mexico$203,923
36Wyoming$203,424
37Missouri$202,259
38North Dakota$202,176
39Texas$201,344
40South Carolina$200,762
41Kansas$196,768
42Tennessee$195,770
43Oklahoma$194,106
44Alabama$193,606
45South Dakota$192,608
46Kentucky$190,112
47Louisiana$189,613
48West Virginia$189,363
49Arkansas$180,794
50Mississippi$177,798

Meanwhile, Mississippi is the least expensive state for a family to live comfortably, requiring $177,798 per year. Arkansas ($180,794) comes in second, followed by West Virginia ($189,363). In common, all these states share low prices of housing.

Learn More About Cost of Living From Visual Capitalist

If you enjoyed this post, be sure to check out this graphic, which ranks the median down payment for a house by U.S. state.

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