Posted on by Fraser Cain

Space Station Pictures

Mir

Here are some space station pictures. We’ve already done photo galleries of the International Space Station, but let’s take a look at some different stations as well:

This is a picture of the Mir Space Station, launched by Russia. This photograph was taken by the crew of STS-89 on the space shuttle Endeavour.

Space Station

Here is a recent image of the International Space Station captured by the crew of STS-129. It shows how much of the construction has now been completed.

Skylab

This is a picture of Skylab, the United States’ first space station. It was in orbit from 1973 to 1979, and was visited by 3 crews of astronauts.

Stanford Torus

And maybe some day we’ll live in a futuristic space station like this. It’s called a Stanford Torus, and rotates to provide the people living inside an artificial gravity.

Bigelow station

This is an artist’s impression of a future space hotel developed by Bigelow Aerospace. The various modules are inflated and connected together. Test versions of the modules have already been sent into orbit.

We’ve written many articles about the International Space Station for Universe Today. Here’s an article about how you can track the International Space Station, and here’s an article about a how a radio operator was able to communicate with the station.

If you’d like more info on the station, check out NASA’s mission page for ISS. And here’s a link to NASA’s human spaceflight page for the station.

We’ve also recorded an episode of Astronomy Cast about the space shuttle. Listen here, Episode 127: The US Space Shuttle.

Posted on by Fraser Cain

Amazing Images

Moon from Earth

Here are some amazing images of space:

This is an amazing image of the Moon taken from the International Space Station orbiting Earth. What a view!

M83. Image credit: Hubble

This is a photograph of the spiral galaxy M83, one of the closest best examples we can see of a spiral galaxy. This image was captured by the Hubble Space Telescope.

Hurricane Ike

Here’s an image of Hurricane Ike captured by astronauts on board the International Space Station.

Apollo 11

Here’s a photo of NASA’s Apollo 11 lunar lander rising from the surface of the Moon to dock with the Command and Service module.

Halley's Comet

Here’s a picture of Halley’s comet taken by the Giotto spacecraft. You can see the nucleus of the comet tumbling in space and the tail trailing behind.

If you’d like to get more outer space pictures for yourself, check out NASA’s Astronomy Picture of the Day, as well as NASA’s Image of the Day.

Many of the best pictures of space come from the Hubble Space Telescope. You can see the latest images from the Hubble Site, and then an archive of old images at the Hubble Heritage site. There are also great pictures from the Chandra X-Ray Observatory and NASA’s Spitzer Space Telescope.

If you’d like pictures of the planets, check out NASA’s Planetary Photojournal, and here are links to missions at the planets in the Solar System. MESSENGER, Venus Express, the Lunar Reconnaissance Orbiter, Mars Reconnaissance Orbiter, Cassini, and New Horizons.

We’ve written many articles about amazing images for Universe Today. Here’s an article about some images from STS-129, and here are some images of the shuttle and Hubble transiting across the Sun.

We’ve recorded many episodes of Astronomy Cast about space. Try this one, Episode 99: The Milky Way.

Posted on by Fraser Cain

Pale Blue Dot

The "pale blue dot" of Earth captured by Voyager 1 in Feb. 1990 (NASA/JPL)



NASA’s Voyager spacecraft pushed further out into space than any other mission before them. Voyager 1 and 2 visited Jupiter and Saturn, and Voyager 2 went on to travel to Uranus and Neptune. In 1990, after Voyager 2 completed its mission of visiting the outer planets, Carl Sagan encouraged NASA to have the Voyager 1 spacecraft to take a final picture of Earth, from a distance of more than 6 billion kilometers from Earth. The resulting image showed Earth as nothing more than a tiny spec, a “pale blue dot“. That was the name given to it by Carl Sagan, and it stuck.

Voyager 1 took this photograph in 1990, when it was approximately 40.5 astronomical units from Earth (6 billion km, or 3.8 billion miles). It was taken at a height of 32° above the plane of the ecliptic, using red, green and blue filters. Earth is the little dot circled in the image. The beams you see in the image are a glare from the Sun seen by Voyager 1’s camera.

Sagan wrote a book with the title “Pale Blue Dot”, and he gave a commencement address in 1996 reflecting on the image:

“Look again at that dot. That’s here, that’s home, that’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.”

We’ve written many articles about Carl Sagan for Universe Today. Here’s an article remembering Carl Sagan, and here’s Sagan’s personal influence on my own life. We also used the Pale Blue Dot image as one of our famous Where in the Universe contests.

If you’d like more info on Earth, check out NASA’s Solar System Exploration Guide on Earth. And here’s a link to NASA’s Earth Observatory.

We’ve also recorded an episode of Astronomy Cast all about planet Earth. Listen here, Episode 51: Earth.

Posted on by Fraser Cain

Distance to the Center of the Earth

The Earths interior (University of Chicago)

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The average distance to the centre of the Earth is 6,371 km or 3,959 miles. In other words, if you could dig a hole 6,371 km, you’d reach the center of the Earth. At this point you’d be in the Earth’s liquid metal core.

I said that this number is an average. That’s because the Earth isn’t a perfect sphere, it’s actually an oblate spheroid – a squished ball. The Earth is rotating on its axis, turning around once a day. Points on the equator are moving in a circle more than 1,600 km/hour. This creates a centrifugal force that pulls regions of the equator outward and flattens the poles.

The distance to the center of the Earth from the equator is 6,378 km or 3,963 miles. And the distance to the center of the Earth from the poles is only 6,356 km or 3,949 miles. That’s a difference of 22 km. In other words, if you’re standing on the equator, you’re 22 km further away from the center of the Earth than someone standing on the North Pole.

So if you did want to dig that hole into the Earth, the shortest distance would be from the North or South Pole. Good luck!

We’ve written several articles about the center of Earth. Here’s an article about the radius of the Earth, and here’s an article about the layers of the Earth.

If you’d like more info about the interior of the Earth, check out this article from the University of Nevada, Reno.

We’ve recorded an entire episode of Astronomy Cast about the Earth. Listen here, Episode 51: Earth.

Posted on by Fraser Cain

Distance to Alpha Centauri

Alpha Centauri is the closest known star system to the Solar System. Also known as Rigil Kentaurus, Alpha Centauri is actually a multiple star system. It’s certainly a binary star, with two sunlike stars orbiting one another. And there’s also a red dwarf star, Proxima Centauri, which astronomers still argue about whether it’s part of the system.

The closest star in the group is Proxima Centauri, located only 4.243 light-years from the Sun. And then the Alpha Centauri AB stars are located 4.37 light-years away.

With the unaided eye, Alpha Centauri looks like a single star. But then under the power of a telescope, it’s possible to split them and see the individual stars separately. Alpha Centauri is only really prominent in the southern skies, and below the horizon to astronomers in the north.

Alpha Centauri A is slightly larger and more luminous than the Sun, while Alpha Centauri B is smaller and cooler than the Sun. But Proxima Centauri is a tiny red dwarf star, with only 1/8th the mass of the Sun.

We’ve written several articles about the Alpha Centauri system. Here’s an article about how we might be able to detect Earthlike planets around Alpha Centauri, and here’s an article about the sounds of Alpha Centauri.

Here’s a cool image of Alpha Centauri at Astronomy Picture of the Day.

We’ve also recorded an episode of Astronomy Cast about what it might take to travel to Alpha Centauri. Listen here, Episode 145: Interstellar Travel.

Posted on by Fraser Cain

How Was Venus Discovered?

Venus captured by Magellan.

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Venus is one of the planets visible with the unaided eye. In fact, Venus is the brightest object in the sky, after the Sun and the Moon. So it’s impossible to know how was Venus discovered. The planet has been known about since prehistoric times. Perhaps a better question is, when did we realize that Venus was a planet?

Thousands of years ago, the Greek astronomers thought that the Earth was the center of the Universe, and everything revolved around us, including the Sun, the Moon, the planets and the stars. But in the in the 1500s, Nicolaus Copernicus developed his theories of a Sun-centered Solar System. Instead of the traditional idea, the Sun was at the center, and the Earth was just another planet like Venus and Mars.

This theory was given a tremendous amount of evidence when Galileo Galilei first turned his rudimentary telescope on Venus, showing that the planet went through phases, like the Moon. This meant that it orbited the Sun, and not the Earth. Galileo also discovered the 4 major moons orbiting Jupiter, demonstrating that not all objects in the Universe orbited the Earth.

So it was in the 16th and 17th centuries that astronomers really came to understand that both Venus and Earth were just planets orbiting the Sun.

We’ve written many articles about the discovery of planets for Universe Today. Here’s an article about how Uranus was discovered, and here’s how Neptune was discovered.

And if you’d like more info on Venus, check out Hubblesite’s News Releases about Venus, and here’s a link to NASA’s Solar System Exploration Guide on Venus.

We’ve also recorded an episode of Astronomy Cast all about Venus. Listen here, Episode 50: Venus.

Posted on by Fraser Cain

Largest Moon of Saturn

The largest moon of Saturn is Titan, measuring 5,150 km across. In fact, Titan is the second largest moon in the Solar System, after Jupiter’s Ganymede. Titan is so big that it’s even larger than planet Mercury, which is only 4,879 km across. And it’s much bigger than the Earth’s moon at 3,474 km.

Astronomers used to think that Titan was actually the largest moon in the Solar System, but when NASA’s Voyager spacecraft first arrived at the moon in the 1980s, they were able to make detailed observations of the moon at its atmosphere. They proved that Titan’s atmosphere extended out for dozens of kilometers, and so the physical moon itself was actually smaller than previously thought, making it smaller than Ganymede.

Titan orbits Saturn at an average distance of 1,221,870 km, completing an orbit every 15.945 days. It’s tidally locked to Saturn, so it always presents the same face to Saturn. So a day on Saturn is also the same amount of time it takes to orbit Saturn.

Titan is the only moon in the Solar System known to have a thick atmosphere. In fact, the pressure of the atmosphere on the surface of Saturn is 1.5 times greater than the atmospheric pressure here on Earth. Of course, the atmosphere of Titan is almost entirely nitrogen, and the temperature is -179° C. So it wouldn’t be a comfortable place to visit without a spacesuit.

We’ve written many articles about Titan for Universe Today. Here’s an article about seasonal changes on Titan, and here’s an article about how Titan’s haze acts like an ozone layer.

If you’d like more info on Titan, 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’ve also recorded an episode of Astronomy Cast just about Saturn’s moons. Listen here, Episode 61: Saturn’s Moons.

Posted on by Fraser Cain

Moon Rotation

Moon Rotation

The rotation of the Moon is a strange situation. It takes the same amount of time for the Moon to complete a full orbit around the Earth as it takes for it to complete one rotation on its axis. In other words, the Moon rotation time is 27.3 days, just the same as its orbital time: 27.3 days.

What this means to us here on Earth is that the Moon always presents the same face to the Earth. We only see one side of the Moon, and not the other. And if you could stand on the surface of the Moon, the Earth would appear to just hang in the sky, not moving anywhere.

Astronomers say that the Moon is tidally locked to the Earth. At some point in the past, it did have a different rotation rate from its orbital period. But slight differences in the shape of the Moon caused the Moon to experience different amounts of gravity depending on its position. These differences acted as a brake, slowing the Moon rotation speed down until it matched its orbital period. There are other tidally locked moons in the Solar System. Pluto and its moon Charon are tidally locked to each other, so they always present the same face to one another.

We’ve written many articles about rotation for Universe Today. Here’s an article about the rotation of the Earth, and here’s an article about the rotation of Saturn.

If you’d like more info on the Moon, check out NASA’s Solar System Exploration Guide on the Moon, and here’s a link to NASA’s Lunar and Planetary Science page.

We’ve also recorded an episode of Astronomy Cast all about the Moon. Listen here, Episode 113: The Moon, Part 1.

Posted on by Fraser Cain

How Big is the Moon?

Earth Moon Comparison. Image credit: NASA

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The Moon is one of the most significant objects in the night sky, second only in brightness to the Sun. So, how big is the Moon?

The diameter of the Moon is only 3,474 km across. Just for comparison, the diameter of the Earth at the equator is 12,756 km. That’s only 27% the diameter of the Earth. The Moon is also the 5th largest moon in the Solar System, after Ganymede, Titan, Callisto and Io.

In terms of volume, the Moon only contains 2.195 x 1010 km3. That sounds like a lot of cubic kilometers of Moon, but again, that’s only 2% the volume of Earth.

The surface area of the Moon is 3.793 x 107 km2. That’s about the same size as Russia, Canada and the United States combined.

The circumference of the Moon is 10,921 km. Again, that’s only a little over a quarter the circumference of the Earth.

We’ve written many articles about the Moon for Universe Today. Here’s an article about the Moon compared to Earth, and here’s an article about the mass of the Moon.

If you’d like more info on the Moon, check out NASA’s Solar System Exploration Guide on the Moon, and here’s a link to NASA’s Lunar and Planetary Science page.

We’ve also recorded several episodes of Astronomy Cast about the Moon. Listen here, Episode 113: The Moon, Part 1.