Universe Today

Here are some great Solar System Photos

The first in our group of Solar System photos is this montage of all the planets in the Solar System.

Here's another montage of all the planets in the Solar System.

And here's another picture of the Solar System.

This image shows the current number of planets in the Solar System. Pluto, Ceres and Eris have been designated as dwarf planets , so there are only 8 planets in the Solar System.

If you'd like to find more Solar System photos, check out NASA's Planetary Photojournal. And here's a link to the various missions currently visiting the planets: MESSENGER at Mercury, Venus Express, the Lunar Reconnaissance Orbiter, the Mars Reconnaissance Orbiter, Cassini at Saturn, and New Horizons which is headed to Pluto.

We've also written many articles about the Solar System. Here's an article about the planets in the Solar System, and here's an article about how many moons there are in the Solar System.

We've also recorded many episodes of Astronomy Cast about the planets in the Solar System. Try this one, Episode 49: Mercury.

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Here's a handy planets fact sheet.

Mercury
Mass: 0.3302 x 10²⁴ kg
Volume: 6.083 x 10¹⁰ km³
Average radius: 2439.7 km
Average diameter: 4879.4 km
Mean density: 5.427 g/cm³
Escape velocity: 4.3 km/s
Surface gravity: 3.7 m/s²
Visual magnitude: -0.42
Natural satellites: 0
Rings? – No
Semimajor axis: 57,910,000 km
Orbit period: 87.969 days
Perihelion: 46,000,000 km
Aphelion: 69,820,000 km
Mean orbital velocity: 47.87 km/s
Maximum orbital velocity: 58.98 km/s
Minimum orbital velocity: 38.86 km/s
Orbit inclination: 7.00°
Orbit eccentricity: 0.2056
Sidereal rotation period: 1407.6 hours
Length of day: 4222.6 hours
Discovery: Known since prehistoric times
Minimum distance from Earth: 77,300,000 km
Maximum distance from Earth: 221,900,000 km
Maximum apparent diameter from Earth: 13 arc seconds
Minimum apparent diameter from Earth: 4.5 arc seconds
Maximum visual magnitude: -1.9

Venus
Mass: 4.8685 x 10²⁴ kg
Volume: 92.843 x 10¹⁰ km³
Average radius: 6051.8 km
Average diameter: 12103.6 km
Mean density: 5.243 g/cm³
Escape velocity: 10.36 km/s
Surface gravity: 8.87 m/s²
Visual magnitude: -4.40
Natural satellites: 0
Rings? – No
Semimajor axis: 108,210,000 km
Orbit period: 224.701 days
Perihelion: 107,480,000 km
Aphelion: 108,940,000 km
Mean orbital velocity: 35.02 km/s
Maximum orbital velocity: 35.26 km/s
Minimum orbital velocity: 34.79 km/s
Orbit inclination: 3.39°
Orbit eccentricity: 0.0067
Sidereal rotation period: 5832.5 hours
Length of day: 2802.0 hours
Discovery: Known since prehistoric times
Minimum distance from Earth: 38,200,000 km
Maximum distance from Earth: 261,000,000 km
Maximum apparent diameter from Earth: 66.0 arc seconds
Minimum apparent diameter from Earth: 9.7 arc seconds
Maximum visual magnitude: -4.6

Earth
Mass: 5.9736 x 10²⁴ kg
Volume: 108.321 x 10¹⁰ km³
Average radius: 6,371.0 km
Average diameter: 12,742 km
Mean density: 5.515 g/cm³
Escape velocity: 11.186 km/s
Surface gravity: 9.798 m/s²
Visual magnitude: -3.86
Natural satellites: 1
Rings? – No
Semimajor axis: 149,600,000 km
Orbit period: 365.256 days
Perihelion: 147,090,000 km
Aphelion: 152,100,000 km
Mean orbital velocity: 29.78 km/s
Maximum orbital velocity: 30.29 km/s
Minimum orbital velocity: 29.29 km/s
Orbit inclination: 0.00°
Orbit eccentricity: 0.0167
Sidereal rotation period: 23.9345 hours
Length of day: 24.0000 hours
Axial tilt: 23.45°

Mars
Mass: 0.64185 x 10²⁴ kg
Volume: 16.318 x 10¹⁰ km³
Average radius: 3,389.5 km
Average diameter: 6,779 km
Mean density: 3.933 g/cm³
Escape velocity: 5.03 km/s
Surface gravity: 3.71 m/s²
Visual magnitude: -1.52
Natural satellites: 2
Rings? – No
Semimajor axis: 227,920,000 km
Orbit period: 686.980 days
Perihelion: 206,620,000 km
Aphelion: 249,230,000 km
Mean orbital velocity: 24.13 km/s
Orbit inclination: 1.850°
Orbit eccentricity: 0.0935
Sidereal rotation period: 24.6229 hours
Length of day: 24.6597 hours
Axial tilt: 25.19 °
Discovery: Known since prehistoric times
Minimum distance from Earth: 55,700,000 km
Maximum distance from Earth: 401,300,000 km
Maximum apparent diameter from Earth: 25.1 arc seconds
Minimum apparent diameter from Earth: 3.5 arc seconds
Maximum visual magnitude: -2.91

Jupiter
Mass: 1,898.6 x 10²⁴ kg
Volume: 143,128 x 10¹⁰ km³
Average radius: 69,911 km
Average diameter: 139,822 km
Mean density: 1.326 g/cm³
Escape velocity: 59.5 km/s
Surface gravity: 24.79 m/s²
Natural satellites: 63
Rings? – Yes
Semimajor axis: 778,570,000 km
Orbit period: 4,332.589 days
Perihelion: 740,520,000 km
Aphelion: 816,620,000 km
Mean orbital velocity: 13.07 km/s
Orbit inclination: 1.304°
Orbit eccentricity: 0.0489
Sidereal rotation period: 9.9250 hours
Length of day: 9.9259 hours
Axial tilt: 3.13°
Discovery: Known since prehistoric times
Minimum distance from Earth: 588,500,000 km
Maximum distance from Earth: 968,100,000 km
Maximum apparent diameter from Earth: 50.1 arc seconds
Minimum apparent diameter from Earth: 29.8 arc seconds
Maximum visual magnitude: -2.94

Saturn
Mass: 568.46 x 10²⁴ kg
Volume: 82,713 x 10¹⁰ km³
Average radius: 58,232 km
Average diameter: 116,464 km
Mean density: 0.687 g/cm³
Escape velocity: 35.5 km/s
Surface gravity: 10.44 m/s²
Natural satellites: 60
Rings? – Yes
Semimajor axis: 1,433,530,000 km
Orbit period: 10,759.22 days
Perihelion: 1,352,550,000 km
Aphelion: 1,514,500,000 km
Mean orbital velocity: 9.69 km/s
Orbit inclination: 2.485°
Orbit eccentricity: 0.0565
Sidereal rotation period: 10.656 hours
Length of day: 10.656 hours
Axial tilt: 26.73°
Discovery: Known since prehistoric times
Minimum distance from Earth: 1,195,500,000 km
Maximum distance from Earth: 1,658,500,000 km
Maximum apparent diameter from Earth: 20.1 arc seconds
Minimum apparent diameter from Earth: 14.5 arc seconds
Maximum visual magnitude: 0.43

Uranus
Mass: 86.832 x 10²⁴ kg
Volume: 6,833 x 10¹⁰ km³
Average radius: 25,362 km
Average diameter: 50,724 km
Mean density: 1.270 g/cm³
Escape velocity: 21.3 km/s
Surface gravity: 8.87 m/s²
Natural satellites: 27
Rings? – Yes
Semimajor axis: 2,872,460,000 km
Orbit period: 30,685.4 days
Perihelion: 2,741,300,000 km
Aphelion: 3,003,620,000 km
Mean orbital velocity: 6.81 km/s
Orbit inclination: 0.772°
Orbit eccentricity: 0.0457
Sidereal rotation period: 17.24 hours
Length of day: 17.24 hours
Axial tilt: 97.77°
Discovery: 13 March 1781
Minimum distance from Earth: 2,581,900,000 km
Maximum distance from Earth: 3,157,300,000 km
Maximum apparent diameter from Earth: 4.1 arc seconds
Minimum apparent diameter from Earth: 3.3 arc seconds
Maximum visual magnitude: 5.32

Neptune
Mass: 102.43 x 10²⁴ kg
Volume: 6,254 x 10¹⁰ km³
Average radius: 24,622 km
Average diameter: 49,244 km
Mean density: 1.638 g/cm³
Escape velocity: 23.5 km/s
Surface gravity: 11.15 m/s²
Natural satellites: 13
Rings? – Yes
Semimajor axis: 4,495,060,000 km
Orbit period: 60,189 days
Perihelion: 4,444,450,000 km
Aphelion: 4,545,670,000 km
Mean orbital velocity: 5.43 km/s
Orbit inclination: 1.769°
Orbit eccentricity: 0.0113
Sidereal rotation period: 16.11 hours
Length of day: 16.11 hours
Axial tilt: 28.32°
Discovery: 23 September 1846
Minimum distance from Earth: 4,305,900,000 km
Maximum distance from Earth: 4,687,300,000 km
Maximum apparent diameter from Earth: 2.4 arc seconds
Minimum apparent diameter from Earth: 2.2 arc seconds
Maximum visual magnitude: 7.78

We've written many articles about the Solar System. Here's an article about how many moons there are in the Solar System, and here's an article about the formation of the Solar System.

If you'd like more info on the Solar System, check out NASA's Planetary Fact Sheet.

We've recorded several episodes of Astronomy Cast about the Solar System. Start here, Episode 49: Mercury.

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The mysterious Eris and moons (NASA)

Eris, originally named 2003 UB₃₁₃ was discovered by Palomar observatory researcher Mike Brown; Mike has been behind many of the trans-Neptunian discoveries in the last decade. Mike and his team discovered Eris by systematically scanning the sky for objects moving at the right speed in the right object to be in the outer Solar System.

Further observations of Eris showed that it was actually larger than Pluto by a significant amount; it measured 2,500 km across, compared to Pluto's 2,300 km diameter. And it orbited at a distance of 67 astronomical units, compared to Pluto's 39 AU (1 AU is the average distance from the Earth to the Sun).

Because there was now a larger object than Pluto found orbiting the Sun, astronomers needed to decide whether this would be come the tenth planet. At a meeting of the International Astronomical Union in 2006, astronomers decided to redefine their classification of a planet. And these new rules excluded Eris. Instead of becoming the tenth planet, Eris became a dwarf planet; the same fate as Pluto.

We've written many articles about Eris for Universe Today. Here's an article about how Eris is changing, and here's an article about how Xena was renamed to Eris.

If you'd like more info on Eris, check out NASA's page on Eris.

We've also recorded an episode of Astronomy Cast that explains why Pluto isn't a planet any more. Listen here, Episode 1: Pluto's Planetary Identity Crisis.

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Here are pictures of all the planets.

Montage of the planets Credit: NASA

A different side of Mercury. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

And a picture of Venus.

Blue marble Earth. Image credit: NASA

A picture of Earth.

Photo of Mars

Next, planet Mars.

Hubble Jupiter

And now Jupiter.

Saturn. Image credit: Hubble

Here's a picture of Saturn.

Uranus, seen by Voyager 2. Image credit: NASA/JPL

A picture of Uranus.

Neptune

And finally, a picture of Neptune.

We have written many articles about all the planets for Universe Today. Here are some interesting facts about the planets, and here's an article discussing how far the planets are from the Sun.

If you want more pictures of all the planets, check out NASA's Planetary Photojournal.

We have recorded a series of episodes of Astronomy Cast that take you through the Solar System. Start here with Episode 49: Mercury.

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Planets in the Solar System. Image credit: NASA/JPL/IAU

Mercury is the closest planet to the Sun, orbiting at a distance of only 57.9 million km. It completes one orbit around the Sun every 87.9 days.

Venus is the second planet from the Sun. It's a twin of Earth in terms of size and mass, but Venus' thick carbon dioxide atmosphere traps heat and makes its surface temperature hellish; hot enough to melt lead.

Earth is the 3rd planet from the Sun. It's the only place in the Solar System with the right temperature for liquid water. And the only place we know of with life.

Mars is next. It's a small, dry red planet with a very thin atmosphere. Scientists think that Mars had liquid water on its surface billions of years ago, but it all dried away or got locked into ice deposits under the surface.

Jupiter is the 5th planet in the Solar System. It's also the largest planet in the Solar System. It's so big that you could fit 1321 Earths inside Jupiter.

Saturn is the 6th planet from the Sun. It's best known for its beautiful and delicate ring system. Saturn actually has such a low density that it would float in water if you could find a tub big enough.

Uranus is next, it's considered an ice giant planet. It was also the first planet discovered in the modern age. All the other planets are visible with the unaided eye, and have been known about for thousands of years.

Neptune is the last planet in the Solar System. It's another ice giant, and orbits about 30 time further from the Sun than the Earth. It takes almost 165 years to complete one orbit around the Sun.

We have written many articles about the Solar System. Here's an article about all the planets in the Solar System, and here's an article about the biggest planet in the Solar System.

You can get more information about the Solar System from NASA's Solar System Exploration page.

We have done a whole series of episodes of Astronomy Cast about the Solar System. You can start here on Episode 49: Mercury.

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Here are some planet pictures.

True color image of Mercury (MESSENGER)

This is a true color picture of Mercury captured by NASA's MESSENGER spacecraft.

This is a picture of planet Venus, taken by NASA's Magellan spacecraft.

Blue marble Earth. Image credit: NASA

This is the famous blue marble picture of planet Earth.

Photo of Mars

This is a picture of planet Mars stitched together out of photographs taken by NASA's Viking spacecraft.

Hubble Jupiter

Here's a picture of planet Jupiter taken by the Hubble Space Telescope.

Saturn image. Credit: NASA/JPL/SSI

A picture of planet Saturn taken by NASA's Cassini spacecraft as it was approaching Saturn.

Uranus, seen by Voyager 2. Image credit: NASA/JPL

This is a picture of planet Uranus, taken by NASA's Voyager 2 spacecraft.

Neptune

And last but not least, here's a picture of planet Neptune, taken by NASA's Voyager 2 spacecraft.

We have written many stories about the planets. Here's an article about all the planets in the Solar System, and here's an article about the discovery of the planets.

If you want more information about the planets, check out NASA's World Book.

We have recorded several episodes of Astronomy Cast about all the planets. Start here with our show, Episode 49: Mercury.

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Ring of Fire Volcanoes

Volcanoes are destructive forces of nature that occur not only on our planet, but also on other planets in our Solar System. If you are looking for information on volcanoes for kids, then check out the following links. All of them are geared for children and have great information.

FEMA explains to kids what volcanoes are and has facts about a number of different volcanoes. The site is very kid-friendly.

Weather Wiz Kids discusses what a volcano is and how volcanoes form. They also list the different categories of volcanoes. Additionally, the website has safety tips on what to do if a volcano occurs near you and a glossary of terms associated with volcanoes. They also have a lesson plan on volcanoes and ideas for activities.

Volcano World 4 Kids has games for kids. They also have basic facts about volcanoes as well as listing where volcanoes are around the world and more resources for kids. The website has a section for educators with a number of materials including handouts.

Fun School has a recipe for the classic baking soda and vinegar  volcano. If you want to make a very fun experiment – and a great science fair project – bake a volcano out of homemade clay dough. Then paint the island and create the baking soda and vinegar volcano inside the clay volcano.

Kids Astronomy talks about the surface of the planets and how there are volcanoes on different planets.

National Geographic Kids has a video on volcanoes you can view. They also have a quiz and photos of different volcanoes.

Discovery Kids has interactive features about volcanoes. They also have an activity where you can create your own virtual volcano on the website and information on different types of volcanoes. You can also learn more about Pompeii on their website.

ESA Kids gives general information about volcanoes.

Universe Today also has articles on the Solar System for kids and the Sun for kids.

If you are looking for more information, try volcanoes and the volcanoes of deep space.

Astronomy Cast has an episode about  volcanoes hot and cold.

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Gigapan from Apollo 17. Credit: Gigapan

Including the first two astronauts 12 men have walked on the moon. Looking at the development of the Apollo program it is not surprising. The entire Apollo program was a study in the gradual progression of technology until a successful moon landing and return. The first Apollo missions dealt with actually getting to the moon and coming back. Up until the Apollo 11 mission, no astronauts landed on the moon. They simply flew to it, did a flyby and returned. After the successful Apollo 11 mission of course the feat was repeated several times.

NASA launched 6 successful mission in all to the moon. The last was in 1972. There is very interesting information concerning these twelve astronauts. First off they are among only 24 people to actually see the far side of the moon. Second there were other famous astronauts other than Armstrong and Aldrin. Alan Shepard the commander of the Apollo 14 mission was the second man and first American in space. His mission was also the first to be broadcast in color television.

Apollo 17 was the last mission to the moon. The three astronauts on this mission were Eugene Cernan, Ronald Evans and Harrison Schmitt. Their mission was also the first night launch occurring at midnight. Cernan and Schmitt became the very last astronauts to walk on the moon.

Another question that would probably be raised is if the lunar landings were so successful why didn't NASA or other nations plan more missions? The simple answer is lack of resources. The Apollo program at its peak cost 24 billion dollars. Even now the current NASA budget is only half of that amount. On top of that, the United States was going through a major recession in the latter half of the seventies so NASA had a curtailed budget and limited political will to launch any more missions. The Soviet Union was the only other government capable of a similar feat but they had already decided against the expenditure. The eventual collapse of the Soviet Union put a permanent end to any possibility of an attempt by a foreign government at the time.

If you enjoyed this article there are others on Universe Today that you will like. There is a great article on the Space Race. There is also a great article on Russian Cosmonauts.

There are also great resources on the web. The NASA website has extensive information on the Apollo program. The Smithsonian website also has a page with detailed information on each of the missions.

You can also check out Astronomy Cast. Episode 114, The Moon, Part 2 is about the history lunar exploration.

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This has got to be be one of the most heartbreaking questions I get asked, "Why Isn't Pluto a Planet". And I get it a lot. I was expecting that a few years after the International Astronomical Union's controversial decision, the debate would have settled down and people would finally accept it. But no, it's still a sore point for many people – Pluto is not a planet (let that sink in). In this article, I'll explain the events that led up to the decision, the current state of planetary definition, and any hope Pluto has for the future. Let's find out why Pluto is no longer considered a planet.
Read more…

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