Posted on by Fraser Cain

How Far is Saturn from the Sun?

Saturn. Image credit: Hubble

Saturn’s distance from the Sun is 1.4 billion km. The exact number for Saturn’s average distance from the Sun is 1,433,449,370 km.

Need that number in miles? Saturn’s average distance from the Sun is 891 million miles.

Noticed that I said that these numbers are Saturn’s average distance from the Sun. That’s because Saturn is actually following an elliptical orbit around the Sun. Some times it gets closer, and other times it gets more distant from the Sun. When it’s at the closest point of its orbit, astronomers call this perihelion. At this point, Saturn is only 1.35 billion km from the Sun. Its most distant point in orbit is called aphelion. At this point, it gets out to 1.51 billion km from the Sun.

Astronomers use another measurement tool for calculating distance in the Solar System called “astronomical units”. 1 astronomical unit is the average distance from the Earth to the Sun; approximately 150 million km. At its closest point, Saturn is 9 AU, and then at its most distant point, it’s 10.1 AU. Saturn’s average distance from the Sun is 9.6 AU.

We have written many articles about Saturn for Universe Today. Here’s an article about how NASA’s Spitzer space telescope discovered a huge ring around Saturn, and here’s a cool movie of an aurora around Saturn.

If you want more information on Saturn, check out Hubblesite’s News Releases about Saturn. And here’s a link to the homepage of NASA’s Cassini spacecraft, which is orbiting Saturn.

We have also recorded an entire episode of Astronomy Cast just about Saturn. Listen here, Episode 59: Saturn.

Posted on by Fraser Cain

How Long Does it Take Uranus to Orbit the Sun?

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

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Uranus orbits the Sun much further than the Earth, and so it takes much longer to orbit the Sun. How much longer? Uranus takes 84.3 years to complete its orbit around the Sun. Uranus was only discovered in 1781 by Sir William Herschel. Since a year takes just over 83 Earth years, it completed its first orbit since discovery in 1865, and then its second in 1949. It’ll only complete its 3rd orbit around the Sun since its discovery in 2033.

Unlike most of the planets, which have slightly tilted orbits, Uranus is completely tilted over on its side. It kind of looks like it’s rolling its way around as it orbits the Sun. What this means is that one of Uranus’ hemispheres is completely in sunlight for half of its orbit, and then its other hemisphere is in sunlight for the rest of its orbit. Each pole gets 42 years of continual sunlight, followed by 42 years of continual darkness.

The orbit of Uranus is about the same length as the average life expectancy for a human being. In other words, if you were born on Uranus, you would only experience a single birthday, if you were lucky, after living for more than 84 Earth years. And nobody would experience two birthdays.

We have written many articles about Uranus for Universe Today. Here’s an article about how many rings Uranus has, and here’s an article about the atmosphere of Uranus.

If you’d like more information on Uranus, check out Hubblesite’s News Releases about Uranus. And here’s a link to the NASA’s Solar System Exploration Guide to Uranus.

We have also recorded an entire episode of Astronomy Cast just about Uranus. Listen here, Episode 62: Uranus.

Posted on by Fraser Cain

How Long Does it Take Mercury to Orbit the Sun?

Mosaic of Mercury. Credit: NASA / JHUAPL / CIW / mosaic by Jason Perry

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Mercury is the closest planet to the Sun, and so it’s the fastest to orbit the Sun. In fact, Mercury only takes 88 days to orbit the Sun. In other words, Mercury’s orbit only takes 24% as long as Earth’s orbit.

If you were born on Mercury, you would have celebrated 4 times as many birthdays as you do on Earth. In other words, if you’re 10 here on Earth, you’d be 40 in Mercury years. Now that’s a possible way to grow up more quickly.

Mercury orbits the Sun at an average distance of only 57.9 million km. Compare this with Earth’s average orbital distance of 150 million km.

Unlike the other planets in the Solar System, Mercury doesn’t really experience any seasons. This is because Mercury has no atmosphere to trap heat from the Sun. Whichever side of Mercury is currently facing the Sun experience temperatures of up to 700 Kelvin. And then the side of the planet that’s in the shade dips down to only 100 Kelvin; that’s well below freezing. Even though Mercury is close, you would experience incredibly cold temperatures if you lived on the surface.

The orbit of Mercury was actually a great puzzle to astronomers until the 20th century. They couldn’t explain why the point of Mercury’s furthest orbit of the Sun was slowly drifting at a rate of 43 arcseconds per century. But this strange motion was finally explained perfectly by predictions made by Albert Einstein with his Theory of Relativity.

We have written many articles about Mercury for Universe Today. Here’s an article about Mercury giving up more secrets to the MESSENGER spacecraft, and here’s a massive mosaic image of Mercury.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We have also recorded an entire episode of Astronomy Cast just about Mercury. Listen here, Episode 49: Mercury.

Posted on by Fraser Cain

How Long Does it Take Pluto to Orbit the Sun?

Hubble image of Pluto and some of its moons, Charon, Nix and Hydra. Image Credit: NASA, ESA, H. Weaver (JHU/APL), A. Stern (SwRI), and the HST Pluto Companion Search Team

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Because Pluto orbits much further from the Sun than Earth, it takes much longer to orbit the Sun. In fact, Pluto takes 248 years to orbit the Sun. That’s because Pluto orbits at an average distance of 5.9 billion km from the Sun, while Earth only orbits at 150 million km. In fact, it takes so long for Pluto to orbit that Sun, that the dwarf planet hasn’t even completed a third of an orbit from when it was discovered back in February 18th, 1930.

Pluto has a highly elliptical orbit. Its distance from the Sun varies from 4.4 billion km to 7.4 billion km. And during this orbital period, Pluto goes through a few interesting changes. You might be surprised to learn that Pluto has an atmosphere. When it’s at its closest point to the Sun, Pluto’s atmosphere evaporates from the surface and surrounding the dwarf planet. And then when it gets further away, the atmosphere freezes again, coating the surface in a thin layer.

Pluto was only discovered in 1930 by Clyde W. Tombaugh. Because it takes 248 years to orbit the Sun, Pluto won’t have completed a full orbit until the year 2178.

We have written many articles about Pluto for Universe Today. Here’s an article about why Pluto isn’t a planet any more, and here’s an article about methane discovered in Pluto’s atmosphere.

If you’d like more information on Pluto, check out Hubblesite’s News Releases about Pluto, and here’s a link to NASA’s Solar System Exploration Guide to Pluto.

We’ve also recorded several episodes of Astronomy Cast just about Pluto. Listen here, Episode 64: Pluto and the Icy Outer Solar System.

Posted on by Fraser Cain

How Long Does it Take Neptune to Orbit the Sun

Neptune

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Neptune orbits much further away from the Sun than the Earth, so its orbit takes much longer. In fact, Neptune takes 164.79 years to orbit around the Sun. That’s almost 165 times longer than Earth takes to orbit the Sun.

Here’s an interesting fact. Neptune was only discovered on September 23, 1846. At the time this article was written (2009), that was only 163 years ago. In other words, since its discovery, Neptune has not even made a single orbit around the Sun.

On July 11, 2011, Neptune will have completed one full orbit around the Sun. Finally, Neptune will be 1 year old.

Just like Earth, Neptune’s axis is tilted away from the Sun’s axis. This means that it experiences seasons as it orbits the Sun. For half of its orbit, Neptune’s northern hemisphere is tilted towards the Sun, and then for the second half of its orbit, its southern hemisphere is tilted towards the Sun. This differential heating creates very powerful winds on Neptune. In fact, Neptune has the strongest sustained winds on the Solar System, with winds measured at 2100 km/hour.

We have written many articles about Neptune for Universe Today. Here’s an article about the atmosphere of Neptune. And here’s an article about who discovered Neptune.

If you’d like more information on Neptune, take a look at Hubblesite’s News Releases about Neptune, and here’s a link to NASA’s Solar System Exploration Guide to Neptune.

We have also recorded an entire episode of Astronomy Cast just about Neptune. Listen here, Episode 63: Neptune.

Posted on by Fraser Cain

My Dad’s Treehouse

I know this has nothing to do with space exploration, but my Dad posted a video of his trip up and down the spiral staircase he built around the outside of a tree on his property (I grew on up Hornby Island, BC). The staircase has 99 stairs and goes up for about 75 feet (25 meters). He’s built a platform at the top where you can sit and see mountains and the ocean. And I spend my summer visits pulling the kids off the thing. Here’s a link to Dad’s blog (he’s a photographer, by trade, so I have a well documented childhood).

P.S. Oh, and Dad made it clear that the bird’s nest was old and empty.

Posted on by Fraser Cain

Satellite Finder

Globalstar satellite

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There are some amazing resources on the Internet that will let you track and find satellites in the sky. Did you know that the International Space Station is the brightest manmade object in the sky? It’s easy to see if you know when and were to look. So, this article should give you some good satellite finder resources, so you can track down and bag sightings of satellites.

The first place to start is NASA’s tracking page for the International Space Station, space shuttle and Hubble Space Telescope. This tells you where the spacecraft currently are, and also give you a way to find out when the spacecraft are going to be flying over your part of the world. They have a quick list of common locations, but you can also enter your latitude and longitude, and the system will give you some sighting opportunities.

Next, check out the Real Time Satellite Tracking page. This shows you the current position of thousands of satellites, and lets you see what’s overhead right now. You can set up satellite finders to watch the position of certain satellites. It’s an amazing resource.

Another great tool is Heaven’s Above. It lets you put in your local address, and then get predictions for satellites that will be overhead in the next few days. You can see the current position of the International Space Station, and much more.

If you have an iPhone, here’s a cool app that lets you find out the current location of the International Space Station and the space shuttle (if it’s in orbit right now).

If you have a satellite dish, and you need a satellite finder to maximize the strength of the signal, here’s a link to a Satellite finding kit from Amazon.com. It lets you finely tune the direction of your satellite dish to get the best signal from the satellite.

We have written many articles about satellites for Universe Today. Here’s an article about how you can watch satellites gather data in real time, and here’s a service that lets you launch your own satellite for only $8000.

We have done many episodes of Astronomy Cast about satellites. Listen to Episode 84: Getting Around the Solar System.

Posted on by Fraser Cain

Satellite Map

NASA satellite map of the Earth

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There are thousands of satellites overhead in space right now, and many of them are being used to map every single square meter of planet Earth. And many of these images are being freely distributed on the Internet so you can access them through any browser. If you’re looking for a satellite map, there are many services out there that can help you out.

Probably the easiest and best place to start is with the Google Maps service from Google. This allows you to see a satellite map of the entire Earth. You can drag around the map to browse around the planet, and you can zoom out and in right down to the highest resolution images they have in their server. In many cases this means you can see your house, your yard, and even your car parked out in the street. You can also type in a specific address location and go straight there. There are street maps you can overlay or remove, you can get driving directions, and much more. And the Google Maps API has been made available by Google to other websites, so people are developing mashups that let you track running routes and find the nearest bathroom.

An even cooler satellite mapping service is Google Earth. Unlike Google Maps, you have to download Google Earth to your local PC, Mac or Linux machine (there’s even an iPhone version). Then you get this cool spinning 3-D version of the Earth. You can zoom out and in, type in a specific location address or geocode to find any spot on Earth. They also have a big library of additional layers that you can put over top, to see additional information mapped on the Earth. It’s well worth the download.

Another good service is TerraServer; they let you buy satellite maps if you want a nice printed version for your wall. If you don’t want to use Google, there are similar mapping tools from Microsoft and Yahoo.

We have written many articles about how satellites are being used to map the Earth. Here’s an article about how scientists use satellite photos to track penguin poop from space, and how Google’s maps had a satellite view of Obama’s inauguration.

We have also recorded an episode of Astronomy Cast all about Earth. Listen here, Episode 51: Planet Earth.

Posted on by Fraser Cain

What is the Most Remote Place on Earth?

Remotest Island

Have you had enough of kids, car alarms and the obnoxious laugh of your neighbor down the hall? You may find yourself wanting to get away from it all. If you aren’t lucky enough to have the magical nose of Sam Stephens to zap you into another dimension, you can visit Bouvet Island; an uninhabited, glacier clad island located between the southern tip of Africa and Antarctica. By all accounts, this is the remotest place on Earth, but if you don’t like the cold or have something against Norway, the county to which it belongs, take heart, you can always move to the comparatively burgeoning metropolis of Tristan da Cunha, a group of British, volcanic islands half way between South America and Africa. One of the islands in this group is actually called Inaccessible Island; and that’s saying something given its neighbors!

The most remote place on Earth can be defined as the landmass furthest from any other landmass and either inhabited or uninhabited. Since Tristan da Cunha is a group of islands, they can’t be defined as being furthest from another land mass, but taken as a whole, they tie with Bouvet Island as the most remote. The Tristan da Cunha group includes Ascension, Saint Helena and Tristan da Cunha itself which has a total population of 284. The islands are 2,816 km away from the nearest landmass.

What is Tristan da Cunha famous for, other than being hard to get to? Wideawake Airfield on Ascension Island was jointly owned by the US and British governments and used extensively during WWII, but then fell into disuse. In 1982, the British used Ascension Island as a staging base for the Falklands War. It’s famous also, for housing one of the 5 worldwide GPS ground antennae which you would no doubt, need to even get there!

Want more Earth extremes? Here’s an article about the hottest place on Earth, and here’s an article about the coldest place on Earth.

Here’s the guide to visiting Tristan da Cunha.

We have recorded an episode of Astronomy Cast all about Earth. Listen here, Episode 51: Earth.

Posted on by Fraser Cain

Why is the Sun Hot?

Plasma on the surface of the Sun. Image credit: Hinode

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The Sun is the hottest place in the Solar System. The surface of the Sun is a mere 5,800 Kelvin, but down at the core of the Sun, the temperatures reach 15 million Kelvin. What’s going on, why is the Sun hot?

The Sun is just a big plasma ball of hydrogen, held together by the mutual gravity of all its mass. This enormous mass pulls inward, trying to compress the Sun down. It’s the same reason why the Earth and the rest of the planets are spheres. As the pull of gravity compresses the gas inside the Sun together, it increases the temperature and pressure in the core.

If you could travel down into the Sun, you’d reach a point where the pressure and temperature are enough that nuclear fusion is able to take place. This is the process where protons are merged together into atoms of helium. It can only happen in hot temperatures, and under incredible pressures. But the process of fusion gives off more energy than it uses. So once it gets going, each fusion reaction gives off gamma radiation. It’s the radiation pressure of this light created in the core of the Sun that actually stops it from compressing any more.

The Sun is actually in perfect balance. Gravity is trying to squeeze it together into a little ball, but this creates the right conditions for fusion. The fusion releases radiation, and it’s this radiation that pushes back against the gravity, keeping the Sun as a sphere.

We have written many articles about the Sun for Universe Today. Here’s an article about how hot the surface of the Sun is, and here’s an article about the parts of the Sun.

If you’d like more information on the Sun, check out NASA’s Solar System Exploration Guide on the Sun, and here’s a link to the SOHO mission homepage, which has the latest images from the Sun.

We have also recorded an episode of Astronomy Cast about the Sun. Check it out, Episode 30: The Sun, Spots and All.