The Planets in our Solar System
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Mercury
Mercury is the closest planet to our Sun, at just 58 million km (36 million miles) or 0.39 Astronomical Unit (AU) out. But despite its reputation for being sun-baked and molten, it is not the hottest planet in our Solar System
Mercury is also the smallest planet in our Solar System, and is also smaller than its largest moon (Ganymede, which orbits Jupiter). And being equivalent in size to 0.38 Earths, it is just slightly larger than the Earth’s own Moon. But this may have something to do with its incredible density, being composed primarily of rock and iron ore.
Diameter Mass Length of Year (Orbit) Length of Day Moons Temperature Weight Mercury Facts4,879 km (3,032 miles) 3.3011 x 10^23 kg (0.055 Earths) 87.97 Earth days 59 Earth days Mercury does not have any moons -173 to 427 degrees Celcius (-279 to 801 degrees Fahrenheit) If you weigh 45 kg (100 pounds) on Earth, you would weigh 17 kg (38 pounds) on Mercury -
Venus
Venus is the second closest planet to our Sun, orbiting at an average distance of 108 million km (67 million miles) or 0.72 AU. Venus is often called Earth’s “sister planet,” as it is just a little smaller than Earth. Venus is 81.5% as massive as Earth, and has 90% of its surface area and 86.6% of its volume. The surface gravity, which is 8.87 m/s², is equivalent to 0.904 g – roughly 90% of the Earth standard.
And due to its thick atmosphere and proximity to the Sun, it is the Solar Systems hottest planet, with temperatures reaching up to a scorching 735 K (462 °C). To put that in perspective, that’s over four and a half times the amount of heat needed to evaporate water, and about twice as much needed to turn tin into molten metal (231.9 °C)!
Diameter Mass Length of Year (Orbit) Length of Day Moons Temperature Weight Venus Facts7,521 miles (12,104 km) 4.867 x 10^24 kg (0.815 Earth mass) 225 days 243 Earth days Venus has no moons 462 degrees C (864 degrees F) If you weigh 45 kg (100 pounds) on Earth, you would weigh 41 kg (91 pounds) on Venus -
Earth
Our home, and the only planet in our Solar System (that we know of) that actively supports life. Our planet is the third from the our Sun, orbiting it at an average distance of 150 million km (93 million miles) from the Sun, or one AU. Given the fact that Earth is where we originated, and has all the necessary prerequisites for supporting life, it should come as no surprise that it is the metric on which all others planets are judged.
Whether it is gravity (g), distance (measured in AUs), diameter, mass, density or volume, the units are either expressed in terms of Earth’s own values (with Earth having a value of 1) or in terms of equivalencies – i.e. 0.89 times the size of Earth.
Diameter Mass Length of Year (Orbit) Length of Day Moons Temperature Atmosphere Earth Facts12,760 km (7,926 miles) 5.97 x 10^24 kg 365 days 24 hours (more precisely, 23 hours, 56 minutes and 4 seconds.) Earth has one moon Average is about 14 C, (57 F), with ranges from -88 to 58 (min/max) C (-126 to 136 F) 78% nitrogen, 21% oxygen, and 1% various other gases -
Mars
Mars is the fourth planet from the sun at a distance of about 228 million km (142 million miles) or 1.52 AU. It is also known as “the Red Planet” because of its reddish hue, which is due to the prevalence of iron oxide on its surface. In many ways, Mars is similar to Earth, which can be seen from its similar rotational period and tilt, which in turn produce seasonal cycles that are comparable to our own.
The same holds true for surface features. Like Earth, Mars has many familiar surface features, which include volcanoes, valleys, deserts, and polar ice caps. But beyond these, Mars and Earth have little in common. The Martian atmosphere is too thin and the planet too far from our Sun to sustain warm temperatures, which average 210 K (-63 ºC) and fluctuate considerably.
Diameter Mass Length of Year (Orbit) Length of Day Moons Temperature Weight Mars Facts6,787 km, (4,217 miles) 6.4171 x 10^23 kg (0.107 Earths) 687 Earth days 24 hours 37 minutes Mars has two small moons, Phobos and Deimos Average is about -55 C (-67 F), with ranges of -153 to +20 °C (-225 to +70 °F) If you weigh 45 kg (100 pounds) on Earth, you would weigh 17 kg (38 pounds) on Mars -
Jupiter
Jupiter is the fifth planet from the Sun, at a distance of about 778 million km (484 million miles) or 5.2 AU. Jupiter is also the most massive planet in our Solar System, being 317 times the mass of Earth, and two and half times larger than all the other planets combined. It is a gas giant, meaning that it is primarily composed of hydrogen and helium, with swirling clouds and other trace gases.
Jupiter’s atmosphere is the most intense in the Solar System. In fact, the combination of incredibly high pressure and coriolis forces produces the most violent storms ever witnessed. Wind speeds of 100 m/s (360 km/h) are common and can reach as high as 620 km/h (385 mph). In addition, Jupiter experiences auroras that are both more intense than Earth’s, and which never stop.
Diameter Mass Length of Year (Orbit) Length of Day Moons Temperature Weight Jupiter Facts428,400 km (88,730 miles) 1.8986 × 10^27 kg (317.8 Earths) 11.9 Earth years 9.8 Earth hours Jupiter now has a total of 79 identified moons -148 C, (-234 F) If you weigh 45 kg (100 pounds) on Earth, you would weigh 115 kg (253) pounds on Jupiter -
Saturn
Saturn is the sixth planet from the Sun at a distance of about 1.4 billion km (886 million miles) or 9.5 AU. Like Jupiter, it is a gas giant, with layers of gaseous material surrounding a solid core. Saturn is most famous and most easily recognized for its spectacular ring system, which is made of seven rings with several gaps and divisions between them.
Diameter Mass Length of Year (Orbit) Length of Day Moons Temperature Weight Saturn Facts120,500 km (74,900 miles) 5.6836 x 10^26 kg (95.159 Earths) 29.5 Earth years 10.7 Earth hours Saturn has 53 known moons with an additional 9 moons awaiting confirmation -178 C (-288 F) If you weigh 45 kg (100 pounds) on Earth, you would weigh about 48 kg (107 pounds) on Saturn -
Uranus
Uranus is the seventh planet from the sun at a distance of about 2.9 billion km (1.8 billion miles) or 19.19 AU. Though it is classified as a “gas giant”, it is often referred to as an “ice giant” as well, owing to the presence of ammonia, methane, water and hydrocarbons in ice form. The presence of methane ice is also what gives it its bluish appearance.
Uranus is also the coldest planet in our Solar System, making the term “ice” seem very appropriate! What’s more, its system of moons experience a very odd seasonal cycle, owing to the fact that they orbit Neptune’s equator, and Neptune orbits with its north pole facing directly towards the Sun. This causes all of its moons to experience 42 year periods of day and night.
Diameter Mass Length of Year (Orbit) Length of Day Moons Temperature Weight Uranus Facts51,120 km (31,763 miles) 8.681 × 10^25 kg (14.5 times that of Earth) 84 Earth years 18 Earth hours Uranus has 27 moons -216 C (-357 F) If you weigh 45 kg (100 pounds) on Earth, you would weigh 41 kg (91 pounds) on Uranus -
Neptune
Neptune is the eighth and farthest planet from the Sun, at a distance of about 4.5 billion km (2.8 billion miles) or 30.07 AU. Like Jupiter, Saturn and Uranus, it is technically a gas giant, though it is more properly classified as an “ice giant” with Uranus.
Due to its extreme distance from our Sun, Neptune cannot be seen with the naked eye, and only one mission has ever flown close enough to get detailed images of it. Nevertheless, what we know about it indicates that it is similar in many respects to Uranus, consisting of gases, ices, methane ice (which gives its color), and has a series of moons and faint rings.
Diameter Mass Length of Year (Orbit) Length of Day Moons Temperature Weight Neptune Facts49,530 km (30,775 miles) 1.0243 x 10^26 kg (17 Earths) 165 Earth years 16 Earth hours Neptune has 13 confirmed moons and 1 more awaiting official confirmation -214 C (-353 F) If you weigh 45 kg (100 pounds) on Earth, you would weigh 52 kg (114 pounds) on Neptune
Having covered the basics of definition and classification, let’s get talking about those celestial bodies in our Solar System that are still classified as planets (sorry Pluto!). Here is a brief look at the eight planets in our Solar System. Included are quick facts and links so you can find out more about each planet.