Mercury
Mercury's surface temperatures are both extremely hot and cold. Because the planet is so close to the Sun, day temperatures can reach highs of 430°C) Without an atmosphere to retain that heat at night, temperatures can dip as low as -180°C.
Despite its proximity to the Sun, Mercury is not the hottest planet in our solar system – that title belongs to nearby Venus, thanks to its dense atmosphere. But Mercury is the fastest planet, zipping around the Sun every 88 Earth days.
With a radius of 2,440 kilometres, Mercury is a little more than 1/3 the width of Earth. If Earth were the size of a ten cent coin, Mercury would be about as big as a blueberry.
From an average distance of 58 million kilometres, Mercury is 0.4 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 3.2 minutes to travel from the Sun to Mercury.
Mercury's highly eccentric, egg-shaped orbit takes the planet as close as 47 million kilometres and as far as 70 million kilometres from the Sun. It speeds around the Sun every 88 days, traveling through space at nearly 47 kilometres per second, faster than any other planet.
Mercury spins slowly on its axis and completes one rotation every 59 Earth days. But when Mercury is moving fastest in its elliptical orbit around the Sun (and it is closest to the Sun), each rotation is not accompanied by sunrise and sunset like it is on most other planets. The morning Sun appears to rise briefly, set, and rise again from some parts of the planet's surface. The same thing happens in reverse at sunset for other parts of the surface. One Mercury solar day (one full day-night cycle) equals 176 Earth days – just over two years on Mercury.
Mercury's axis of rotation is tilted just 2 degrees with respect to the plane of its orbit around the Sun. That means it spins nearly perfectly upright and so does not experience seasons as many other planets do.
Image courtesy of NASA
Despite its proximity to the Sun, Mercury is not the hottest planet in our solar system – that title belongs to nearby Venus, thanks to its dense atmosphere. But Mercury is the fastest planet, zipping around the Sun every 88 Earth days.
With a radius of 2,440 kilometres, Mercury is a little more than 1/3 the width of Earth. If Earth were the size of a ten cent coin, Mercury would be about as big as a blueberry.
From an average distance of 58 million kilometres, Mercury is 0.4 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 3.2 minutes to travel from the Sun to Mercury.
Mercury's highly eccentric, egg-shaped orbit takes the planet as close as 47 million kilometres and as far as 70 million kilometres from the Sun. It speeds around the Sun every 88 days, traveling through space at nearly 47 kilometres per second, faster than any other planet.
Mercury spins slowly on its axis and completes one rotation every 59 Earth days. But when Mercury is moving fastest in its elliptical orbit around the Sun (and it is closest to the Sun), each rotation is not accompanied by sunrise and sunset like it is on most other planets. The morning Sun appears to rise briefly, set, and rise again from some parts of the planet's surface. The same thing happens in reverse at sunset for other parts of the surface. One Mercury solar day (one full day-night cycle) equals 176 Earth days – just over two years on Mercury.
Mercury's axis of rotation is tilted just 2 degrees with respect to the plane of its orbit around the Sun. That means it spins nearly perfectly upright and so does not experience seasons as many other planets do.
Image courtesy of NASA
Venus
Venus is the second planet from the Sun, and Earth's closest planetary neighbor. Venus is the third brightest object in the sky after the Sun and Moon. Venus spins slowly in the opposite direction from most planets.
Venus is similar in structure and size to Earth, and is sometimes called Earth's evil twin. Its thick atmosphere traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system with surface temperatures hot enough to melt lead. Below the dense, persistent clouds, the surface has volcanoes and deformed mountains. Venus orbits the Sun from an average distance of 108 million kilometres, or 0.72 astronomical units.
One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight about six minutes to travel from the Sun to Venus.
Earth's nearness to Venus is a matter of perspective. The planet is nearly as big around as Earth. Its diameter at its equator is about 12,104 kilometres, versus 12,756 kilometres for Earth. From Earth, Venus is the brightest object in the night sky after our own Moon. The ancients, therefore, gave it great importance in their cultures, even thinking it was two objects: a morning star and an evening star. That’s where the trick of perspective comes in.
At its nearest to Earth, Venus is about 38 million kilometres away. But most of the time the two planets are farther apart. The maximum distance between Venus and Earth is about 261 million kilometres. Mercury, the innermost planet, actually spends more time in Earth’s proximity than Venus.
Image courtesy of NASA
Venus is similar in structure and size to Earth, and is sometimes called Earth's evil twin. Its thick atmosphere traps heat in a runaway greenhouse effect, making it the hottest planet in our solar system with surface temperatures hot enough to melt lead. Below the dense, persistent clouds, the surface has volcanoes and deformed mountains. Venus orbits the Sun from an average distance of 108 million kilometres, or 0.72 astronomical units.
One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight about six minutes to travel from the Sun to Venus.
Earth's nearness to Venus is a matter of perspective. The planet is nearly as big around as Earth. Its diameter at its equator is about 12,104 kilometres, versus 12,756 kilometres for Earth. From Earth, Venus is the brightest object in the night sky after our own Moon. The ancients, therefore, gave it great importance in their cultures, even thinking it was two objects: a morning star and an evening star. That’s where the trick of perspective comes in.
At its nearest to Earth, Venus is about 38 million kilometres away. But most of the time the two planets are farther apart. The maximum distance between Venus and Earth is about 261 million kilometres. Mercury, the innermost planet, actually spends more time in Earth’s proximity than Venus.
Image courtesy of NASA
Earth
With an equatorial diameter of 12,760 kilometres, Earth is the biggest of the terrestrial planets and the fifth largest planet in our solar system.
From an average distance of 150 million kilometres, Earth is exactly one astronomical unit away from the Sun because one astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. This unit provides an easy way to quickly compare planets' distances from the Sun. It takes about eight minutes for light from the Sun to reach our planet. As Earth orbits the Sun, it completes one rotation every 23.9 hours.
It takes 365.25 days to complete one trip around the Sun. That extra quarter of a day presents a challenge to our calendar system, which counts one year as 365 days. To keep our yearly calendars consistent with our orbit around the Sun, every four years we add one day. That day is called a leap day, and the year it's added to is called a leap year.
Earth's axis of rotation is tilted 23.4 degrees with respect to the plane of Earth's orbit around the Sun. This tilt causes our yearly cycle of seasons. During part of the year, the northern hemisphere is tilted toward the Sun, and the southern hemisphere is tilted away. With the Sun higher in the sky, solar heating is greater in the north producing summer there. Less direct solar heating produces winter in the south. Six months later, the situation is reversed. When spring and autumn begin, both hemispheres receive roughly equal amounts of heat from the Sun.
Image courtesy of NASA
From an average distance of 150 million kilometres, Earth is exactly one astronomical unit away from the Sun because one astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. This unit provides an easy way to quickly compare planets' distances from the Sun. It takes about eight minutes for light from the Sun to reach our planet. As Earth orbits the Sun, it completes one rotation every 23.9 hours.
It takes 365.25 days to complete one trip around the Sun. That extra quarter of a day presents a challenge to our calendar system, which counts one year as 365 days. To keep our yearly calendars consistent with our orbit around the Sun, every four years we add one day. That day is called a leap day, and the year it's added to is called a leap year.
Earth's axis of rotation is tilted 23.4 degrees with respect to the plane of Earth's orbit around the Sun. This tilt causes our yearly cycle of seasons. During part of the year, the northern hemisphere is tilted toward the Sun, and the southern hemisphere is tilted away. With the Sun higher in the sky, solar heating is greater in the north producing summer there. Less direct solar heating produces winter in the south. Six months later, the situation is reversed. When spring and autumn begin, both hemispheres receive roughly equal amounts of heat from the Sun.
Image courtesy of NASA
Mars
Mars is one of the most explored bodies in our solar system, and it's the only planet where we've sent rovers to roam the alien landscape. These missions have found lots of evidence that Mars was much wetter and warmer, with a thicker atmosphere, billions of years ago. It's frequently called the "Red Planet" because iron minerals in the Martian dirt oxidize, or rust, causing the surface to look red. With a radius of 3,390 kilometres, Mars is about half the size of Earth. If Earth were the size of a tencent coin, Mars would be about as big as a raspberry. From an average distance of 228 million kilometres, Mars is 1.5 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the
distance from the Sun to Earth.
From this distance, it takes sunlight 13 minutes to travel from the Sun to Mars.
As Mars orbits the Sun, it completes one rotation every 24.6 hours, which is very similar to one day on Earth (23.9 hours). Martian days are called sols – short for "solar day." A year on Mars lasts 669.6 sols, which is the same as 687 Earth days.
Mars' axis of rotation is tilted 25 degrees with respect to the plane of its orbit around the Sun. This is another similarity with Earth, which has an axial tilt of 23.4 degrees. Like Earth, Mars has distinct seasons, but they last longer than seasons here on Earth since Mars takes longer to orbit the Sun (because it's farther away). And while here on Earth the seasons are evenly spread over the year, lasting 3 months (or one quarter of a year), on Mars the seasons vary in length because of Mars' elliptical, egg-shaped orbit around the Sun.
Spring in the northern hemisphere (autumn in the southern) is the longest season at 194 sols. Autumn in the northern hemisphere (spring in the southern) is the shortest at 142 days. Northern winter/southern summer is 154 sols, and northern summer/southern winter is 178 sols.
Image courtesy of NASA
distance from the Sun to Earth.
From this distance, it takes sunlight 13 minutes to travel from the Sun to Mars.
As Mars orbits the Sun, it completes one rotation every 24.6 hours, which is very similar to one day on Earth (23.9 hours). Martian days are called sols – short for "solar day." A year on Mars lasts 669.6 sols, which is the same as 687 Earth days.
Mars' axis of rotation is tilted 25 degrees with respect to the plane of its orbit around the Sun. This is another similarity with Earth, which has an axial tilt of 23.4 degrees. Like Earth, Mars has distinct seasons, but they last longer than seasons here on Earth since Mars takes longer to orbit the Sun (because it's farther away). And while here on Earth the seasons are evenly spread over the year, lasting 3 months (or one quarter of a year), on Mars the seasons vary in length because of Mars' elliptical, egg-shaped orbit around the Sun.
Spring in the northern hemisphere (autumn in the southern) is the longest season at 194 sols. Autumn in the northern hemisphere (spring in the southern) is the shortest at 142 days. Northern winter/southern summer is 154 sols, and northern summer/southern winter is 178 sols.
Image courtesy of NASA
Jupiter
Jupiter is a world of extremes. It's the largest planet in our solar system – if it were a hollow shell, 1,000 Earths could fit inside. It's also the oldest planet, forming from the dust and gases left over from the Sun's formation 4.6 billion years ago. But it has the shortest day in the solar system, taking only 10.5 hours to spin around once on its axis. Jupiter's signature stripes and swirls are actually cold, windy clouds of ammonia and water, floating in an atmosphere of hydrogen and helium. The dark orange stripes are called belts, while the lighter bands are called zones, and they flow east and west in opposite directions. Jupiter’s iconic Great Red Spot is a giant storm bigger than Earth that has raged for hundreds of years.
With a radius of 69,911 kilometres, Jupiter is 11 times wider than Earth. If Earth were the size of a grape, Jupiter would be about as big as a basketball. From an average distance of 778 million kilometres, Jupiter is 5.2 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 43 minutes to travel from the Sun to Jupiter.
Image courtesy of NASA
With a radius of 69,911 kilometres, Jupiter is 11 times wider than Earth. If Earth were the size of a grape, Jupiter would be about as big as a basketball. From an average distance of 778 million kilometres, Jupiter is 5.2 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 43 minutes to travel from the Sun to Jupiter.
Image courtesy of NASA
Saturn
Like fellow gas giant Jupiter, Saturn is a massive ball made mostly of hydrogen and helium. Saturn is not the only planet to have rings, but none are as spectacular or as complex as Saturn's. Saturn also has dozens of moons. From the jets of water that spray from Saturn's moon Enceladus to the methane lakes on smoggy Titan, the Saturn system is a rich source of scientific discovery and still holds many mysteries. With an equatorial diameter of about 120,500 kilometres, Saturn is 9 times wider than Earth.
If Earth were the size of a 20cent coin, Saturn would be about as big as a volleyball.
From an average distance of 1.4 billion kilometres, Saturn is 9.5 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 80 minutes to travel from the Sun to Saturn.
Saturn has the second-shortest day in the solar system. One day on Saturn takes only 10.7 hours (the time it takes for Saturn to rotate or spin around once), and Saturn makes a complete orbit around the Sun (a year in Saturnian time) in about 29.4 Earth years (10,756 Earth days).
Its axis is tilted by 26.73 degrees with respect to its orbit around the Sun, which is similar to Earth's 23.5-degree tilt. This means that, like Earth, Saturn experiences seasons.
Image courtesy of NASA
If Earth were the size of a 20cent coin, Saturn would be about as big as a volleyball.
From an average distance of 1.4 billion kilometres, Saturn is 9.5 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 80 minutes to travel from the Sun to Saturn.
Saturn has the second-shortest day in the solar system. One day on Saturn takes only 10.7 hours (the time it takes for Saturn to rotate or spin around once), and Saturn makes a complete orbit around the Sun (a year in Saturnian time) in about 29.4 Earth years (10,756 Earth days).
Its axis is tilted by 26.73 degrees with respect to its orbit around the Sun, which is similar to Earth's 23.5-degree tilt. This means that, like Earth, Saturn experiences seasons.
Image courtesy of NASA
Uranus
Uranus is a very cold and windy world. The ice giant is surrounded by 13 faint rings and 28 small moons. Uranus rotates at a nearly 90-degree angle from the plane of its orbit. This unique tilt makes Uranus appear to spin sideways, orbiting the Sun like a rolling ball.
With an equatorial diameter of 31,763 miles (51,118 kilometers), Uranus is four times wider than Earth. If Earth was the size of a nickel, Uranus would be about as big as a softball. From an average distance of 2.9 billion kilometres, Uranus is about 19 astronomical units away from the Sun.
One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 2 hours and 40 minutes to travel from the Sun to Uranus. Uranus was the first planet found with the aid of a telescope.
It was discovered in 1781 by astronomer William Herschel, although he originally thought it was either a comet or a star.
It was two years later that the object was universally accepted as a new planet, in part because of observations by astronomer Johann Elert Bode.
Image courtesy of NASA
With an equatorial diameter of 31,763 miles (51,118 kilometers), Uranus is four times wider than Earth. If Earth was the size of a nickel, Uranus would be about as big as a softball. From an average distance of 2.9 billion kilometres, Uranus is about 19 astronomical units away from the Sun.
One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 2 hours and 40 minutes to travel from the Sun to Uranus. Uranus was the first planet found with the aid of a telescope.
It was discovered in 1781 by astronomer William Herschel, although he originally thought it was either a comet or a star.
It was two years later that the object was universally accepted as a new planet, in part because of observations by astronomer Johann Elert Bode.
Image courtesy of NASA
Neptune
Dark, cold, and whipped by supersonic winds, ice giant Neptune is more than 30 times as far from the Sun as Earth. Neptune is the only planet in our solar system not visible to the naked eye. It was the first planet located through mathematical calculations. Using predictions made by Urbain Le Verrier, Johann Galle discovered the planet in 1846 and in 2011 Neptune completed its first 165-year orbit since its discovery.
With an equatorial diameter of 49,528 kilometres Neptune is about four times wider than Earth. If Earth were the size of a 20 cent peice, Neptune would be about as big as a softball.
From an average distance of 4.5 billion kilometres, Neptune is 30 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 4 hours to travel from the Sun to Neptune.
Image courtesy of NASA
With an equatorial diameter of 49,528 kilometres Neptune is about four times wider than Earth. If Earth were the size of a 20 cent peice, Neptune would be about as big as a softball.
From an average distance of 4.5 billion kilometres, Neptune is 30 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 4 hours to travel from the Sun to Neptune.
Image courtesy of NASA
Dwarf Planets
Beyond Neptune, a newer class of smaller worlds called dwarf planets reign, including longtime favorite Pluto. The other dwarf planets are Ceres, Makemake, Haumea, and Eris. Ceres is the only dwarf planet in the inner solar system. It's located in the main asteroid belt between Mars and Jupiter.
Ceres
Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter, and it's the only dwarf planet located in the inner solar system. It was the first member of the asteroid belt to be discovered when Giuseppe Piazzi spotted it in 1801. When NASA's Dawn arrived in 2015, Ceres became the first dwarf planet to receive a visit from a spacecraft.
Called an asteroid for many years, Ceres is so much bigger and so different from its rocky neighbors that scientists classified it as a dwarf planet in 2006.Even though Ceres comprises 25% of the asteroid belt's total mass, Pluto is still 14 times more massive.
Image courtesy of NASA
Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter, and it's the only dwarf planet located in the inner solar system. It was the first member of the asteroid belt to be discovered when Giuseppe Piazzi spotted it in 1801. When NASA's Dawn arrived in 2015, Ceres became the first dwarf planet to receive a visit from a spacecraft.
Called an asteroid for many years, Ceres is so much bigger and so different from its rocky neighbors that scientists classified it as a dwarf planet in 2006.Even though Ceres comprises 25% of the asteroid belt's total mass, Pluto is still 14 times more massive.
Image courtesy of NASA
Pluto
Pluto is a complex and mysterious world with mountains, valleys, plains, craters, and glaciers. It is located in the distant Kuiper Belt.
Discovered in 1930, Pluto was long considered our solar system's ninth planet. But after the discovery of similar worlds deeper in the Kuiper Belt, Pluto was reclassified as a dwarf planet in 2006 by the International Astronomical Union.
Pluto is only about 2,253 kilometres wide. At that small size, Pluto is only about half the width of the United States. It's about 5.8 billin kilometres away from the
Image courtesy of NASA Sun, and it has a thin atmosphere composed mostly of nitrogen, methane, and carbon monoxide. On average, Pluto’s temperature is -387°F (-232°C), making it too cold to sustain life. Pluto is orbited by five known moons, the largest of which is Charon. Charon is about half the size of Pluto itself, making it the largest satellite relative to the planet it orbits in our solar system. Pluto and Charon are often referred to as a "double planet."The only spacecraft to explore Pluto up close was NASA's New Horizons. It flew by the dwarf planet and its moons in 2015.
Pluto is a complex and mysterious world with mountains, valleys, plains, craters, and glaciers. It is located in the distant Kuiper Belt.
Discovered in 1930, Pluto was long considered our solar system's ninth planet. But after the discovery of similar worlds deeper in the Kuiper Belt, Pluto was reclassified as a dwarf planet in 2006 by the International Astronomical Union.
Pluto is only about 2,253 kilometres wide. At that small size, Pluto is only about half the width of the United States. It's about 5.8 billin kilometres away from the
Image courtesy of NASA Sun, and it has a thin atmosphere composed mostly of nitrogen, methane, and carbon monoxide. On average, Pluto’s temperature is -387°F (-232°C), making it too cold to sustain life. Pluto is orbited by five known moons, the largest of which is Charon. Charon is about half the size of Pluto itself, making it the largest satellite relative to the planet it orbits in our solar system. Pluto and Charon are often referred to as a "double planet."The only spacecraft to explore Pluto up close was NASA's New Horizons. It flew by the dwarf planet and its moons in 2015.
Makemake
With a radius of approximately 715 kilometres, Makemake is 1/9 the radius of Earth. If Earth were the size of a ten cent coin, Makemake would be about as big as a mustard seed.
Makemake – along with Pluto, Haumea, and Eris – is located in the Kuiper Belt, a donut-shaped region of icy bodies beyond the orbit of Neptune. Makemake is slightly smaller than Pluto, and is the second-brightest object in the Kuiper Belt as seen from Earth while Pluto is the brightest. It takes about 305 Earth years for this dwarf planet to make one trip around the Sun.
Makemake holds an important place in the history of solar system studies because it was one of the objects – along with Eris – whose discovery prompted the International Astronomical Union to reconsider the definition of a planet, and to create the new group of dwarf planets.
From an average distance of 6.8 billion kilometres, Makemake is 45.8 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 6 hours and 20 minutes to travel from the Sun to Makemake.
Image courtesy of NASA
With a radius of approximately 715 kilometres, Makemake is 1/9 the radius of Earth. If Earth were the size of a ten cent coin, Makemake would be about as big as a mustard seed.
Makemake – along with Pluto, Haumea, and Eris – is located in the Kuiper Belt, a donut-shaped region of icy bodies beyond the orbit of Neptune. Makemake is slightly smaller than Pluto, and is the second-brightest object in the Kuiper Belt as seen from Earth while Pluto is the brightest. It takes about 305 Earth years for this dwarf planet to make one trip around the Sun.
Makemake holds an important place in the history of solar system studies because it was one of the objects – along with Eris – whose discovery prompted the International Astronomical Union to reconsider the definition of a planet, and to create the new group of dwarf planets.
From an average distance of 6.8 billion kilometres, Makemake is 45.8 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 6 hours and 20 minutes to travel from the Sun to Makemake.
Image courtesy of NASA
Humea
Haumea is an oval-shaped dwarf planet that is one of the fastest rotating large objects in our solar system. The fast spin distorts Haumea's shape, making this dwarf planet look like a football.
With an equatorial diameter of about 1,740 kilometres, Haumea is about 1/7 the width of Earth. If Earth were the size of a ten cent coin, Haumea would be about as big as a sesame seed. From an average distance of 6.5 billion kilometres, Haumea is 43 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 6 hours to travel from the Sun to Haumea.
Haumea takes 285 Earth years to make one trip around the Sun. As Haumea orbits the Sun, it completes one rotation every 4 hours, making it one of the fastest rotating large objects in our solar system. It is possible that a large object impacted Haumea billions of years ago and set off Haumea's spin and created its moons.
Image courtesy of NASA
Haumea is an oval-shaped dwarf planet that is one of the fastest rotating large objects in our solar system. The fast spin distorts Haumea's shape, making this dwarf planet look like a football.
With an equatorial diameter of about 1,740 kilometres, Haumea is about 1/7 the width of Earth. If Earth were the size of a ten cent coin, Haumea would be about as big as a sesame seed. From an average distance of 6.5 billion kilometres, Haumea is 43 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight 6 hours to travel from the Sun to Haumea.
Haumea takes 285 Earth years to make one trip around the Sun. As Haumea orbits the Sun, it completes one rotation every 4 hours, making it one of the fastest rotating large objects in our solar system. It is possible that a large object impacted Haumea billions of years ago and set off Haumea's spin and created its moons.
Image courtesy of NASA
Eris
The discovery of Eris help trigger a debate in the scientific community that led to the International Astronomical Union's decision in 2006 to clarify the definition of a planet. Pluto, Eris, and other similar objects are now classified as dwarf planets.
Eris was discovered on Jan. 5, 2005, from data obtained on Oct. 21, 2003, during a Palomar Observatory survey of the outer solar system by Mike Brown, a professor of planetary astronomy at the California Institute of Technology; Chad Trujillo of the Gemini Observatory; and David Rabinowitz of Yale University.
With an equatorial diameter of about 2,400 kilometres, Eris is about 1/5 the width of Earth. Eris, like Pluto, is a little smaller than Earth's Moon. If the Earth were the size of a ten cent coin, Eris would be about as big as a popcorn kernel.
From an average distance of 10 billion kilometres, Eris is about 68 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight more than nine hours to travel from the Sun to the surface of Eris.
Image artists impression courtesy of NASA
The discovery of Eris help trigger a debate in the scientific community that led to the International Astronomical Union's decision in 2006 to clarify the definition of a planet. Pluto, Eris, and other similar objects are now classified as dwarf planets.
Eris was discovered on Jan. 5, 2005, from data obtained on Oct. 21, 2003, during a Palomar Observatory survey of the outer solar system by Mike Brown, a professor of planetary astronomy at the California Institute of Technology; Chad Trujillo of the Gemini Observatory; and David Rabinowitz of Yale University.
With an equatorial diameter of about 2,400 kilometres, Eris is about 1/5 the width of Earth. Eris, like Pluto, is a little smaller than Earth's Moon. If the Earth were the size of a ten cent coin, Eris would be about as big as a popcorn kernel.
From an average distance of 10 billion kilometres, Eris is about 68 astronomical units away from the Sun. One astronomical unit (abbreviated as AU), is the distance from the Sun to Earth. From this distance, it takes sunlight more than nine hours to travel from the Sun to the surface of Eris.
Image artists impression courtesy of NASA
