Astronomy Archives

July 1, 2009December 24, 2015 by Tammy Plotner

Fly Me To The Moon…

“Fly me to the Moon and let me play among the stars… Let me see what life is like on…” Oh, hi there! I’ll just bet you know what’s up with the double image, don’t you? That’s right. A little “stereo magic” by Jukka Metsavainio. But this time you’re in for something really different. Step inside for a magic carpet ride you’ll never forget…

This time our visualization moves! That’s right. You’re going to take a virtual 3D journey along the lunar surface… Just like you were flying along in your own personal lunar lander. While Jukka has instructed that this video was prepared in parallel vision only, I had no trouble slightly crossing my eyes and getting it to work for me that way. I hope you’ll find this as exciting as I did! (And I hope you’re able to see it. Remember, not everyone can…)

As you watch the scenery unfold, see how many craters you can identify as we tour from the lunar south to north. I see Maurolycus and Stofler drift by… Then you can see the huge central peak in Arzachel sticking up out of the shadows! Next thing you know, there’s Albategnius with its vacant looking floor and central peak. Ptolmaeus, Hipparchus, Mare Vaporum… Then look out! Vrrrrrrrrooooooom…. Here come the Apennine Mountains with the deep wells of Aristillus and Autolycus on one side and the smooth plains of Mare Serenitatis on the other. Next thing you know? We’re flying over the Caucasus Mountains and you can see the Alpine Valley like the lunar Grand Canyon… and over there! Over there is Atlas and Hercules! And all the way up at the top? Ah… Goldschmidt! Now, if you’ll pardon me. I’ve got a carpet to catch.

Again!

Many thanks to Northern Galactic member, Jukka Metsavainio for sharing his incredible visions with us. We understand how many hours upon hours it takes to do this, and we cannot thank you enough.

July 1, 2009December 24, 2015 by Fraser Cain

Mercury and Jupiter

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Let’s compare and contrast the two most different planets in the Solar System, Mercury and Jupiter. Of course, you probably know that Mercury is the smallest planet in the Solar System while Jupiter is the largest planet in the Solar System.

First, let’s just take a look at the physical measurements of Jupiter and Mercury. The diameter of Mercury is 4,879.4 km, while the diameter of Jupiter is 142,984 km. In other words, Jupiter is 29.3 times bigger across than Mercury. In terms of volume, you could fit 24,462 Mercurys inside Jupiter. Jupiter even has 5,750 times more mass than Mercury.

Now let’s take a look at their composition. Mercury is a rocky terrestrial planet, with a high density. In fact, the liquid iron core of Mercury accounts for 42% of the planet, and this is surrounded by a mantle and crust of silica. Jupiter in comparison is a relatively less dense gas giant planet; it’s made up almost entirely of hydrogen and helium, with a few other trace elements.

Mercury orbits very close to the Sun, with an average orbital distance of 57.9 million kilometers. Because it orbits so close, Mercury completes an orbit around the Sun every 88 days. Jupiter, on the other hand, is located 778.5 million km from the Sun and takes 11.86 years to complete a single year.

Mercury has no moons or rings, while Jupiter has a faint set of rings and 63 named natural satellites so far.

It sounds like Jupiter and Mercury are different in every way, but there’s one big similarity. You can see them both with your own eyes. Jupiter is very bright and often very high in the sky. In fact, if you see a really bright star in the sky in the middle of the night, you’re probably seeing Jupiter, and not a star at all. Mercury is also possible to see with your own eyes. But since Mercury orbits so close to the Sun, you’ll only see it shortly after sunset or before sunrise until the Sun washes out the night sky.

We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed.

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 a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Mercurio y Júpiter

Reference:
NASA

June 30, 2009December 24, 2015 by Fraser Cain

Water on Mercury

Radar image of Mercury that shows water deposits.

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There’s water on Earth, obviously. And large quantities of water ice on Mars and in the outer Solar System. But astronomers have wondered, is there water on Mercury? There obviously aren’t any lakes and oceans of water on Mercury. We would have detected them from Earth, and definitely would have seen them when the various missions to Mercury skimmed past the planet, taking close up photographs. But does Mercury have water in any form?

The conditions on Mercury sure rule it out. As Mercury slowly rotates, the side facing the Sun experiences extremely high temperatures. At noon on the equator, the temperature rises to 700 Kelvin. And then dips down to just 100 Kelvin at night, since there’s no atmosphere to hold in the temperature. Any water on the surface of Mercury would boil away quickly and escape into space because of Mercury’s low gravity, and the constantly blowing solar wind.

But you might be surprised to know that astronomers have discovered water on Mercury. Not liquid water, but deposits of water ice at the planet’s poles. This is because there are craters at the north and south poles of Mercury which are eternally in shadow. The ice in these craters is never warmed by the Sun, and so it always remains frozen at the bottom of these craters.

When NASA’s MESSENGER spacecraft flew past Mercury in 2008, it also discovered the presence of water vapor in the thin atmosphere that surrounds Mercury. This atmosphere, or more precisely “exosphere”, is created when particles from the Sun’s solar wind bombard Mercury and kick up atoms into its atmosphere. It’s possible that the solar wind is kicking up water from the ice deposits at Mercury’s poles, or maybe it’s coming from cometary fragments. Or maybe the solar wind is depositing the oxygen and hydrogen atoms on Mercury’s surface in the first place.

So there is water on Mercury, just not very much.

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 a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

De agua sobre el mercurio

References:
NASA: Ice on Mercury
NASA Space Math: Is there Ice on Mercury?

June 30, 2009December 24, 2015 by Fraser Cain

Interior of Mercury

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The interior of Mercury is remarkably similar to the interior of our own planet Earth. Like Earth, Mercury has a crust, mantle and core. But there are many differences between our two planets as well.

But when you look at Mercury, it appears very similar to our own Moon. It has the same rugged terrain and numerous impact craters. But Mercury has a very different interior from the Moon. When NASA’s Mariner 10 spacecraft made its flyby of Mercury in 1974, it helped astronomers calculate that Mercury is the second densest planet in the Solar System after Earth. In fact, if Mercury were the size of Earth and had our mass and gravity, it would be even more dense.

At the heart of Mercury is it’s core. This is a ball of liquid iron and other metals that measures approximately 3,600 km across. Considering the fact that Mercury itself is only 4,879.4 km across, the planet’s core accounts for 42% of its volume. Compare this to the Earth’s core, which only accounts for 17% of our planet’s volume.

Astronomers only learned recently that Mercury’s core is liquid, and not solid as originally theorized. They did this by studying how radio signals bounce off the surface of Mercury. They found that wobbles in the planet’s rotation matched predictions only if Mercury’s core was liquid.

Surrounding the core of Mercury is the mantle. Similar to Earth, this mantle consists of silicates, but it only measures 500-700 km thick. Compared this to the Earth’s mantle, which accounts for most of the volume of the planet.

And surrounding Mercury’s mantle is its crust. A region of the planet the measures between 100-300 km thick. Unlike the Earth’s crust, Mercury’s crust has no plate tectonics, so it doesn’t have plates that float above the interior of Mercury. Without these plate tectonics, even impact craters billions of years old are preserved on the planet’s surface.

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’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.

Interior de Mercurio

June 30, 2009December 24, 2015 by Fraser Cain

How Old is Mercury?

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Just how old is Mercury? Is it the oldest planet, or the youngest? Actually, you might be surprised to know that there is no oldest or youngest planet. Mercury is exactly the same age as all the rest of the planets in the Solar System: approximately 4.6 billion years old.

Astronomers think that our entire Solar System started out as a giant cloud of cold molecular hydrogen gas, left over from the Big Bang 13.7 billion years ago. Some event, like a nearby supernova explosion disturbed the cloud and caused it to begin collapsing. As it collapsed, various pieces broke off, each of which would eventually form a star like our own Sun.

Because of conservation of momentum from all the particles of hydrogen, the cloud began to spin as it collapsed, becoming a flattened disk. The newly forming Sun was at the center of this disk, with dust surrounding it. These dust particles collided together, forming larger and larger chunks of dust, rocks, boulders, asteroids, planetesimals, and eventually the planets we see today. All of the planets formed together at the same time.

How do we know how old Mercury is? Astronomers have found meteorites on Earth, that fell from space at some point in the past. They use a technique called radiocarbon dating to determine how old the meteorites are. No matter where the meteorites come from; the Moon, Mars, or the asteroid belt, they’re always the same age: 4.6 billion years.

And so, how old is Mercury? The same as everything in the Solar System: 4.6 billion years old.

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 a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Cuántos años tiene Mercurio

June 30, 2009April 26, 2016 by Stephanie Bender

Continental Crust

The crust is the top layer of the Earth’s Surface. Did you know that there are 2 types, though? One is called the Oceanic Crust, and the other, the Continental Crust. As its name suggests, the Oceanic Crust is the top layer of Earth that forms the ocean floor. The Continental Crust, however, will be our focus.

We walk on top of and dig down through the Continental Crust when we plant or drill. Even if there is an unstable surface at the very top, like sand, the deeper parts of the Crust are made of harder rocks. The large land masses, continents, have bases made from sedimentary, igneous, or metamorphic rocks, as well as any combination thereof. This shield rock is the oldest known; it’s been tested, dated, and found to have been here for 3,960,000,000 years!

Geologists, scientists who study the Earth, believe that shield rock was created when hot molten iron, known as magma cooled. If their math’s correct, it happened around the time these rocks formed, almost 4 billion years ago, right? Some of those rocks were so big it took a long time for them to cool. So, even if the rocks were formed 3.9 billion years ago, they might not have cooled for quite some time. Many estimate that the Continental Crust wasn’t completely hard for another 60,000,000 to 160,000,000 years.

The top portion of this rock has another name, platform rock. The oldest-known platform rocks are approximately 600,000,000 years old, and can be found in central North America. The sedimentary rock ranges from 1,000 to 2,000 meters thick; that is equivalent to more than a half mile to 1.25 miles. When we put the top and bottom portions of the Continental Crust together, we get what scientists call, a craton. Most cratons are stable and haven’t been damaged by earthquakes or volcanoes for hundreds of millions of years.

Around the edges are the continental margins, mostly created by sedimentary rock originally found in the oceans. How is that possible, you ask? Well, it’s due to earthquake and volcanic activity. In this case, it’s mainly due to a phenomenon called, subduction. You see, the Earth fits together like a puzzle; and, if you try to place the wrong piece into a spot where it fits, but isn’t quite right, what happens? Another piece might pop out of place. Sometimes, a continental margin works its way under the oceanic crust. When that occurs, the oceanic layer ends up on top of the continental margin. This is subduction. The most well-known place for this is along The Ring of Fire, an area that covers the edges along the Pacific Ocean. This is why so many and such violent earthquakes, volcanic eruptions, and tsunamis occur in that part of the world.

Universe Today has a wealth of information on this and other related topics. Here are just 2 of those available. The first is entitled,
Earth, Barely Habitable?.

The second is called, Interesting Facts About Planet Earth.

Universe Today also hosts Astronomy Cast, a science program that covers a variety of subjects. Episode 51: Earth, explains this subject in greater detail.

The Encyclopedia of Earth , by Michael Pidwirny has some excellent information, too.

Sources:
USGS
Science Daily

June 29, 2009December 24, 2015 by Fraser Cain

How Long Does it Take to Get to Mercury?

The MESSENGER spacecraft at Mercury (NASA)

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Have you ever wondered how long it might take to travel to Mercury? At its closest point, Mercury gets to within 77.3 million km away from the Earth. Let’s see how long it takes for various spacecraft to get to Mercury.

For starters, let’s look at how long light itself takes to make the journey. Light takes only 4.3 minutes to travel from the Earth to Mercury when they’re at their closest point.

The fastest spacecraft ever launched from Earth is NASA’s New Horizons mission, currently on its way to visit Pluto and the outer Solar System. New Horizons is traveling at about 80,000 kilometers per hour. It would take about 40 days to get from the Earth to Mercury when they’re closest.

Of course, spacecraft don’t travel a straight route between planets, they follow a path that uses the least amount of energy, and so it takes them longer… a lot longer. The first spacecraft to actually make the journey to Mercury was NASA’s Mariner 10, which launched on November 3, 1973. It made its first Mercury flyby on March 29, 1974. Mariner 10 took 147 days to get from Earth to Mercury.

More recently, NASA’s MESSENGER spacecraft launched on August 3, 2004 to study Mercury in orbit. It made its first flyby on January 14th, 2008. That’s a total of 1,260 days to get from Earth to Mercury. So why did MESSENGER take so long? Engineers want the spacecraft to go into orbit around Mercury, and so it needs to be traveling at a slow enough velocity to be able to get into orbit without just flying past. It will finally enter orbit around Mercury in March, 2011.

We have written many stories about Mercury here on Universe Today. Here’s an article about a side of Mercury never before seen by spacecraft, and how Mercury is actually less like the Moon than previously believed.

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 a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Cuánto tiempo toma llegar a Mercurio

References:
NASA: Mariner 10
NASA Messenger Mission Page

June 29, 2009December 24, 2015 by Fraser Cain

Closest Planet to Mercury

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

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What is the closest planet to Mercury? As you probably know, Mercury is the closest planet to the Sun, orbiting at an average distance of 57.9 million km. So then, what planet gets closest to Mercury in orbit.

The answer, of course is Venus, the 2nd closest planet to the Sun. Venus orbits at an average distance of 108.2 million km. So, how close can Mercury and Venus get? Well when I said that Mercury orbits at 57.9 million km, that’s actually an average. Mercury follows an elliptical orbit around the Sun. At its closest point, Mercury gets to within 46 million km, and then at its most distant point, it gets to be 69.8 million km.

And Venus also travels in an elliptical orbit, varying between 107.4 million km and 108.9 million km. So, when the two planets are closest to one another in orbit, the distance between them is about 37.6 million km. And at their most distant point, they can get to be 178.7 million km.

Can Earth ever be closer to Mercury than Venus? Earth’s orbit ranges between 147.1 and 152.1 million km. So when Earth and Mercury are at their closest point, they’re only separated by 77.3 million km. What this means is that there are times when Earth is actually closer to Mercury than Venus; although, most of the time, Venus is the closest planet.

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 a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Más cercano al planeta Mercurio

June 29, 2009December 24, 2015 by Abby Cessna

The Brightest Planet

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When you look up into the sky, if you are lucky, you see shining stars on a field of blue-black. Not all of these objects are stars though. Venus, which can be seen with the unaided eye from Earth, is the brightest planet in our Solar System. Venus was given the nickname evening star and morning star because of its bright, consistent presence. It is often called Earth’s twin because it is similar in shape and size to our own planet. The only objects brighter than Venus are the Moon and the Sun. Sirius, the brightest star that can be seen in the sky, is much dimmer than Venus is. People have known that Venus existed for centuries. The planet was named after the Roman goddess of love and this shining planet has long been associated with femininity.

A planet’s brightness is determined by how much light is reflected by the planet. The term albedo refers to the balance between how much light is absorbed and how much light is reflected by the planet. As the brightest planet, Venus has a very high albedo. Seventy percent of the light that hits Venus is reflected back into space. Why does Venus have such a high albedo though? There are droplets of sulfuric acid and acidic crystals in the atmosphere of Venus. The smooth surfaces of these droplets of sulfuric acid and crystals reflect light very well, which is one reason why Venus is so bright. There is a lot more to this planet than its shimmering appearance though.

The same atmosphere that causes Venus to shine like a beacon also prevents us from getting a look at the planet’s surface. Astronomers did not know what the planet looked like until probes checked out the surface in the last few decades. Because the surface of Venus could not be seen, scientists and writers imagined that it was a tropical, lush landscape. That was not the case though. In addition to hiding the surface and reflecting light, Venus’ atmosphere traps heat from the Sun, turning the planet into a raging furnace. Reaching temperatures of over 460°C, Venus is the hottest planet in the Solar System. Its landscape is similar to that of Mercury and the Moon – rocky, barren terrain with no sign of life. Venus has long enchanted viewers with its beauty and shining presence. Try looking for this planet in the sky; you may find yourself captivated by this shining beauty like many before you.

Universe Today has many articles on Venus including the atmosphere of Venus and how to find Venus in the sky.

For more information check out these articles from NASA on an overview of Venus and from Nine Planets on the brightest planet.

Astronomy Cast has an episode on Venus you should take a look at.

June 29, 2009December 24, 2015 by Fraser Cain

Physics

Physics is such a comprehensive topic that no one could possible hope to include every aspect of it in one place. Entire libraries are dedicated to trying to do just that and they find something new to add every year. What Universe Today has done is compile a list of links to a wide variety of the physics topics that can be found on this site. To sort of intrigue you before you dive into the links, here are a few physics facts:

Absolute zero is -273.15º C. No lab has ever been able to produce it. Close, but no cigar.

Scientist know that nuclear fusion could produce enough energy to sustain our world throughout the remainder of its existence, but no one has ever been able to produce controlled nuclear fusion. The key to fusions success is in control.

John Dalton is known for creating the basis for the current atomic model, but did you know the first atomic model predates his by over 1,000 years?

According to the second law of thermodynamics, our universe will end in a horrible heat death.

Did you know that there is a large number of people who think that the Large Hadron Collider will actually create a black hole that will engulf the Earth from the surface? A little too much science fiction, don’t you think?

These are just a few of the interesting facts that you can find in the links below. Enjoy your hunting!