Posted on by Abby Cessna

Tallest Mountains

Olympus Mons. Image credit: NASA/JPL

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There are many tall mountains around the world as well as on other worlds. Mount Everest is the highest mountain in the world at 8,848 meters. Mauna Kea is the tallest mountain in the world. The tallest mountain is measured from base to top while the highest mountain is measured from sea level to the top.  Everest is located in the Himalayan mountain range in Nepal and near Tibet. Mauna Kea is located in Hawaii and is 10,200 meters from base to tip. From sea level though, it is only about 4,205 meters tall.  Mauna Kea is an extinct shield volcano.

These are not the only tall mountains though. K2 is in the Karakoram mountain range on the border of Pakistan and China. It is 8,612 meters tall and is generally considered the second tallest mountain in the world. The Himalayans are home to many tall mountains besides Mount Everest. This includes Mount Kangchenjunga at 8,586 meters and Mount Lhotse I at 8,501 meters.

Most of the world’s tallest mountains are located in Asia; however, there are a number of tall mountains that are located on other continents. The seven tallest mountains in different continents are known as the Seven Summits. Climbing all seven mountains is a mountaineering challenge that was started in the 1980’s.The first of these is Mount Everest. Another summit is Aconcagua, which is a mountain in Argentina in South America. At approximately 6,962 meters, it is the tallest mountain in the Americas. North America’s tallest mountain is Mount McKinley at 6,194 meters. Mount Kilimanjaro can be found in Tanzania in the continent of Africa and is 5,895 meters tall. The large summit of Mount Kilimanjaro is covered with an ice cap that is receding and according to scientists will eventually be gone. Mount Elbrus, the tallest mountain in Europe at 5,642 meters, can be found in Russia. Vinson Massif is Antarctica’s tallest mountain at 4,897 meters. It is also very large being 21 kilometers long and 13 kilometers wide.  Australia-Oceania’s largest mountain can be found in Indonesia. At 4,884 meters, it is Puncak Jaya, which is also known as the Carstensz Pyramid.

The tallest mountain that we know of is not even on Earth. It is located on Mars and is known as Olympus Mon.  A shield volcano, Olympus Mon is 27,000 meters tall. Mars is not the only other planet with tall mountains though. Venus’ Maxwell Montes is 11,000 meters tall. Satellites also have tall mountains including our Moon, which has Mons Huygens at 4,700 meters tall. The moon Io has a mountain, Boösaule Montes, which is approximately 17,000 meters tall.

Universe Today has articles on tallest mountain and tallest mountain in the Solar System.

For more information, you should take a look at what are the world’s tallest mountains and highest mountains.

Astronomy Cast has an episode on Earth you will find interesting.

Sources:
http://en.wikipedia.org/wiki/List_of_highest_mountains

Posted on by Jean Tate

What is Absolute Temperature?

If you measure temperature relative to absolute zero, the temperature is an absolute temperature; absolute zero is 0.

The most widely used absolute temperature scale is the Kelvin, symbolized with a capital K, which uses Celsius-scaled degrees (there’s another one, the Rankine, which is related to the Fahrenheit scale). We write temperatures in kelvins without the degree symbol; absolute zero is 0 K.

Another name for absolute temperature is thermodynamic temperature. Why? Because absolute temperate is directly related to thermodynamics; in fact it is the Zeroth Law of Thermodynamics that leads to a (formal) definition of (thermodynamic) temperature.

Roughly speaking, the temperature of an object (or similar, like the gas in a balloon) measures the kinetic energy of the particles (atoms, molecules, etc) of the matter it’s made up of … in an average sense, and macroscopically. Note that blobs of matter have far more energy than just the kinetic energy of the atoms in the blob – there’s the energy that holds the atoms together in molecules (if there are any), the binding energy of the nuclei (unless the blog is pure hydrogen, with no deuterium), and so on; none of these energies are counted in the blob’s temperature.

You might think that at absolute zero a substance would be in its lowest possible energy state, especially if it is a pure compound (or isotopically pure element). Well, it isn’t quite that simple … leaving aside zero point energy (something quite counter-intuitive, from quantum mechanics), there’s the fact that many solids have several different, stable crystal structures (even at 0 K), but only one with minimal energy. Then there’s helium, which is a liquid at 0 K (the solid phase of a substance has a lower energy than the corresponding liquid phase), unless under pressure.

The Kelvin is one of the International System of Units (SI) base units (there are seven of these), and is defined with reference to the triple point of water (“The kelvin, unit of thermodynamic temperature, is the fraction 1/273.16 of the thermodynamic temperature of the triple point of water” is the 1967/8 definition; the current one – adopted in 2005 – expands on this to take account of isotropic variations).

Why is it called the Kelvin? Because William Thompson – Lord Kelvin – was the first to describe an absolute temperature scale, in a paper he wrote in 1848; he also estimated absolute zero was -273o C.

Project Skymath has a nice introduction to absolute temperature.

Some Universe Today material you may find interesting: Absolute Zero, Coldest Temperature Ever Created, and Planck First Light.

Sources: Wikipedia, Hyperphysics

Posted on by Jean Tate

Exobiology

Exobiology (same thing as astrobiology) is about life in space (on other planets, and moons; in other solar systems): where it is, what it is, how it started, and how it evolved (all studied scientifically, of course). Because the origin of life right here on Earth, and its early evolution, is essentially unknown, and because of the distinct possibility of similiarities with the origin (and early evolution) of life elsewhere in the universe, exobiology includes research into abiogenesis (and early, and extreme, life on Earth).

Exobiology is very much a multi-disciplinary field, drawing on biology, chemistry, geology (and planetary science), physics, and astronomy.

Because we have a sample of just one – life on Earth – it is difficult to make anything but the most general decisions on what lines of exobiology research are likely to be productive (keep in mind that null results can, of course, be quite productive). Conservatively, looking for planets like Earth in orbit around stars like the Sun (in age as well as mass, metallicity, etc), and looking for clues for fossil life in planetary environments like those found today on Earth (e.g. early Mars) seem better options than investigating possible silicon-based life (to take just one example).

As the number of exosolar (or extrasolar) planetary systems known continues to grow, quickly, discovering the prevalence of Earth-mass planets, in goldilocks orbital zones, seems like a good idea … so today we have the Kepler mission and COROT.

As the early Mars becomes better understood – and the widespread distribution of liquid water then – so today we have plans for the Mars Science Laboratory and ExoMars (the discovery of methane in the Martian atmosphere certainly spurs such developments).

Less conservatively, the discovery of life around black smokers and sites like Lost City (not to mention entire ecosystems within crustal rocks … several km beneath the surface) sparked interest in the possibility of life in Europa, on Titan, even Enceladus (life – albeit rather simple life – we now know does not need to depend, ultimately, on the Sun’s (or another star’s) radiant energy … think chemolithoautotrophs).

Did you know that NASA has an exobiology branch? Check it out! Duke University’s Chemistry Department has an interesting Introduction to Exobiology you might find interesting too.

Universe Today stories on exobiology? Yep, lots; here’s a random selection: Martian Explorers Should Be Looking for Fossils, Did Life Arrive Before the Solar System Even Formed?, Extremophile Hunt Begins in Antarctica, Implications for Exobiologists , and New Targets to Search for Life on Europa.

Any Astronomy Cast episodes on exobiology? Yep … but it’s called Astrobiology.

Sources: NASA, ESA

Posted on by Fraser Cain

Blood Moon



A blood moon is the first full moon after a harvest moon, which is the full moon closest to the fall equinox. Another name for a blood moon is a hunter’s moon.

Before the advent of electricity, farmers used the light of the full moons to get work done. The harvest moon was a time they could dedicate to bringing in their fall harvest. And so a month later is the blood moon, or the hunter’s moon. This was a good time for hunters to shoot migrating birds in Europe, or track prey at night to stockpile food for Winter.

A full moon occurs every 29.5 days, so a blood moon occurs about a month after the harvest moon. A blood moon is just a regular full moon. It doesn’t appear any brighter or redder than any other full moon. The distance between the Earth and the Moon can change over the course of the month. When the moon is at its closest, a full moon can appear 10% larger and 30% brighter than when it’s further away from the Earth.

A blood moon will actually turn red when it matches up with a lunar eclipse. These occur about twice a year, so blood moons match up with lunar eclipses about every 6 years or so. At the time of this writing, the next blood moon lunar eclipse will be in 2015.

We’ve written many articles about the Moon for Universe Today. Here’s an article about the discovery of water on the Moon, and here’s an article about a lava tube on 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 done several episodes of Astronomy Cast about the Moon. Here’s a good one, Episode 17: Where Does the Moon Come From?

Posted on by John Carl Villanueva

How Big is Mars?

Mars

[/caption]Planet Mars’ Olympus Mons holds the record for the tallest known peak in the entire Solar System. Having a height three times taller than Mount Everest’s and a base wide enough to prevent an observer at the base from seeing the top, you would have expected Mars to be on a relatively big planet. But did you know that Mars is much smaller than Earth? So how big is Mars?

The radius of Mars is only about half that of the Earth’s radius; roughly 3,396 km at the equator and 3,376 km at the poles. For comparison, the earth’s equatorial radius is 6,378 km, while its polar radius is 6,357 km.

These radii give Mars a surface area roughly only 28.4% of Earth’s or 144,798,500 km2. The Pacific Ocean is even larger, with an area of roughly 169,200,000 km2.

The dimensions of Mars also gives it a volume approximately equal to 1.6318×1011 km2 and a mass approximately equal to 6.4185×1023 kg. That’s only about 15.1% and 10.7% that of the Earth’s, respectively.

Despite its noticeably smaller size than the Earth, Mars has more majestic geographical features.

For instance, there’s Valles Marineris, a 4,000 km-long and 7 km-deep canyon that spans about one-fifth of the entire planet’s circumference. It is so long that it’s even longer than the length of Europe. If you compare the Grand Canyon to it, Colorado’s pride and joy won’t look so grand anymore.

Want to know how long the Grand Canyon is? 446 km. That’s very long, yes. But that’s only a little over 10% the length of Valles Marineris.

That’s not the only large geographical feature on Mars. Ma’adim Vallis, is another canyon on Mars that’s larger then the Grand Canyon, with a length of 700 km. Then there’s an impact crater that’s been found to be larger than the combined surface area of the continents of Asia, Europe, and Australia.

Now that you know about these extremely majestic geographical features on Mars, the next time someone asks you, “How big is Mars?” you can tell them how it is much smaller than the Earth … but you can also add the salient features that make the Red Planet much more interesting when it comes to a discussion on sizes.

We’ve got more articles about the Planet Mars here on Universe Today. Click on that link or read about interesting facts about the Planet Mars.

There’s more from NASA: “Unmasking the Face on Mars” and “Mars Shoreline Tests: Massifs in the Cydonia Region”

Here are two episodes at Astronomy Cast that you might want to check out as well:
Stellar Roche Limits, Seeing Black Holes, and Water on Mars
The Search for Extraterrestrial Intelligence

Reference:
NASA

Posted on by Jean Tate

Dwarf Star

A comparison of the Sun in its yellow dwarf phase and red giant phase

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A dwarf star is a star that is not a giant or supergiant … in other words, a dwarf star is a normal star! Of course, some dwarf stars are much smaller (less massive, have a smaller radius, etc) than normal (or main sequence, not really massive) stars … and these have names, like white dwarf, red dwarf, brown dwarf, and black dwarf. Our very own Sol (the Sun) is a dwarf star … a yellow dwarf.

Looking more closely at this rather confusing class of objects: a dwarf star has a mass of up to about 20 sols, and a luminosity (a.k.a. intrinsic brightness) of up to about 20,000 sols (‘sol’ is a neat unit; it can mean ‘the mass of the Sun’, or ‘the luminosity of the Sun’, or …!). So just about every star is a dwarf star! Why? Because most stars are on the main sequence (which means almost all have luminosities below 20,000 sols), and only a tiny handful of main sequence stars are more massive than 20 sols. In addition, once a star has burned through all its fuel, it becomes a white dwarf (and, one day, a black dwarf), all of which are dwarf stars by this definition.

The most interesting class of dwarf star is, perhaps, the black dwarf star; it’s hardly a star at all (it doesn’t burn any fuel, except, perhaps, deuterium, for a few million years or so).

So why do astronomers have this classification at all? Hitting the history books gives us a clue … back when spectroscopy was getting started, among astronomers – and well before there was any kind of astronomy except that in the optical (or visual) waveband; think the second half of the 19th century – a curious fact about stars was discovered: the spectra of stars with the same colors could still be very different (and when their distances were estimated, these spectral differences were found to track luminosity). So while dwarf stars overwhelmingly dominate, in terms of numbers, the giants (and sub-giants, and supergiants) pretty much rule in terms of what you can see with your unaided vision.

Neatly linking one kind of dwarf (the Sun, as a yellow dwarf) to another (white dwarf) is Universe Today’s The Sun as a White Dwarf. Other Universe Today articles on dwarf stars (not only white dwarfs!) include Astronomers Discover Youngest and Lowest Mass Dwarfs, Brown Dwarfs Form Like Stars, and Observing an Evaporating Extrasolar Planet.

Astronomy Cast’s episode Dwarf Stars has more on this topic.

Posted on by John Carl Villanueva

How Are Rocks Formed?

A'a lava

As a terrestrial planet, Earth is divided into layers based on their chemical and rheological properties. And whereas its interior region – the inner and outer core – are mostly made up of iron and nickel, the mantle and crust are largely composed of silicate rock. The crust and upper mantle are collectively known as the lithosphere, from which the tectonic plates are composed.

It in the lithosphere that rocks are formed and reformed. And depending on the type of rock, the process through which they are created varies. In all, there are three types of rocks: igneous, sedimentary, and metamorphic. Each type of rock has a different origin. Therefore, the question, “How are rocks formed?” begs three distinct answers.

Continue reading “How Are Rocks Formed?”

Posted on by Fraser Cain

Artificial Satellites

It's getting crowded out there: active and inactive satellites are tracked (Google/Analytical Graphics)

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Artificial satellites are human-built objects orbiting the Earth and other planets in the Solar System. This is different from the natural satellites, or moons, that orbit planets, dwarf planets and even asteroids. Artificial satellites are used to study the Earth, other planets, to help us communicate, and even to observe the distant Universe. Satellites can even have people in them, like the International Space Station and the Space Shuttle.

The first artificial satellite was the Soviet Sputnik 1 mission, launched in 1957. Since then, dozens of countries have launched satellites, with more than 3,000 currently operating spacecraft going around the Earth. There are estimated to be more than 8,000 pieces of space junk; dead satellites or pieces of debris going around the Earth as well.

Satellites are launched into different orbits depending on their mission. One of the most common ones is geosynchronous orbit. This is where a satellite takes 24 hours to orbit the Earth; the same amount of time it takes the Earth to rotate once on its axis. This keeps the satellite in the same spot over the Earth, allowing for communications and television broadcasts.

Another orbit is low-Earth orbit, where a satellite might only be a few hundred kilometers above the planet. This puts the satellite outside the Earth’s atmosphere, but still close enough that it can image the planet’s surface from space or facilitate communications. This is the altitude that the space shuttle flies at, as well as the Hubble Space Telescope.

Artificial satellites can have a range of missions, including scientific research, weather observation, military support, navigation, Earth imaging, and communications. Some satellites fulfill a single purpose, while others are designed to perform several functions at the same time. Equipment on a satellite is hardened to survive in the radiation and vacuum of space.

Satellites are built by various aerospace companies, like Boeing or Lockheed, and then delivered to a launch facility, such as Cape Canaveral. Launch facilities are located as close as possible to the Earth’s equator, to give an extra velocity kick into space. This allows rockets to use less fuel or launch heavier payloads.

The altitude of a satellite’s orbit defines how long it will stay in orbit. Low orbiting satellites are mostly above the Earth’s atmosphere, but they’re still buffeted by the atmosphere and their orbit eventually decays and they crash back into the atmosphere. Other satellites orbiting in high orbits will likely be there for millions of years.

We’ve written many articles about artificial satellites for Universe Today. Here’s an article about geosynchronous orbit, and here’s an article about orbital speed.

You can get more information about satellites from NASA. Here’s a cool realtime satellite tracking system, and here’s Hubblesite.

We’ve also recorded several episodes of Astronomy Cast about satellites. Here’s a good one, Episode 82: Space Junk.

Source: NASA

Posted on by Fraser Cain

Life of a Star

Artist’s impression of a baby star still surrounded by a protoplanetary disc in which planets are forming. Credit: ESO

Stars are kind of like people. They’re born, they live their lives, and then they die. Let’s take a look at the life of a star.

All stars start out a giant clouds of neutral hydrogen, which has been left over since the Big Bang. Some event, such as a nearby supernova explosion causes the cloud to collapse inward, and then gravity takes over. As the cloud collapses, it breaks up into different knots of material, each of which will go on to form a star.

As the cloud continues to collapse inward, the conservation of angular momentum from all the particles sets the cloud spinning. As gravity pulls it further inward, it begins spinning faster and faster and flattens out into a disk. The star forms from the concentration of material in the center of the protostellar disk, and the planets form out in the disk.

In the beginning, a star shines because of the heat of compression through gravity. But eventually the core of the star heats up to the point that nuclear fusion reactions can occur. At this point, the star blasts away the remaining dust and gas with its solar winds and enters the main sequence phase of life.

A star like our Sun will continue as a main sequence star for billions of years; slowly converting hydrogen into helium in its core. But it will eventually run out of easily usable hydrogen in its core. When this happens, the star collapses down a little and then starts to convert a shell of hydrogen into helium around the core. This additional heat puffs out the star into a red giant, causing it to become much larger.

A typical star will go through several phases of expansion and contraction as it burns through shells of hydrogen around its core. Larger stars will also switch to helium fusion in the core, and even go up the periodic table of elements, fusing heavier and heavier elements. Eventually they’ll reach the limits of gravity, running out of fuel to burn. The star will then slough off its outer layers, creating the beautiful planetary nebulae we see from Earth.

And then the star will collapse inward, becoming a white dwarf star. This is a highly compressed object that can have the mass of the Sun, but only be as small as the Moon. It’s still hot because of the residual energy it had when it was a true star, but it slowly cools down, eventually becoming a black dwarf; the same temperature as the background of the Universe.

Stars much larger than our own Sun can have a more dramatic finish. The largest stars will detonate as supernovae when they reach the end of their lives. Some will then collapse down to become neutron stars or black holes, while others explode with such energy that the entire star just blows itself apart.

We’ve written many articles about stars for Universe Today. Here’s an article about the death of stars, and here’s an article about the life cycle of stars.

If you’d like more information on stars, check out Hubblesite’s News Releases about Stars, and here’s the stars and galaxies homepage.

We’ve also recorded several episodes of Astronomy Cast about stars. Here’s a good one, Episode 12: Where Do Baby Stars Come From?

Source: NASA

Posted on by John Carl Villanueva

How are Clouds Formed?

Atmospheric Pollution
Particulates from pollution mixing with clouds above the US (NASA)

[/caption]I bet some of you are fascinated with certain cloud formations. My eldest son once pointed to the sky, excited upon seeing a bunch of clouds taking shape of a menacing dragon. He was however disappointed after a few minutes when the dragon cloud slowly began to deform and fuse with the rest. So how are clouds formed?

First, water evaporates, rises, and fills up the atmosphere. The evaporated water, a.k.a. water vapor then clings to other numerous particles or dust found in the atmosphere. This dust comes from automobiles, fires, volcanoes, bacteria, and sea spray.

As water vapor rises, it cools. Now, the lower the temperature of air, its capacity to hold water vapor (also known as the saturation point of air) also drops.

Eventually, the rising water vapor condenses and forms the structure of the cloud. You can’t however see this structure unless it has its own color. Well, we know that clouds are either white or dark, and that’s why we’re able to see them.

Most clouds are white. That’s because water and ice particles that make up a cloud have just the right amount and sizes to scatter light in all possible wavelengths. When light of practically all wavelengths combine, the result is white light.

However, when too many water and ice particles build up, just like in a storm cloud, much of the scattered light is simply re-scattered into the cloud. In other words, too much particles prevent some of the light from escaping. Hence is the reason why storm clouds are dark.

Try slowly adding milk in water and notice how its color slowly shifts from white to dark as more milk is added.

I’m sure you’ve noticed that clouds easily form on mountains. How are clouds formed on mountains? When a wall of air and water vapor encounters a mountain side, it has nowhere else to go but up the slopes. Well, if you recall, rising water vapor cools and eventually condenses to form clouds.

Thus, mountains don’t have special particles that enhance cloud formation. Rather, it is the barriers that they so form that forces the water vapor to rise and hence develop into cloud structures. A cloud formed due to topographical features is called an orographic cloud.

We’ve got lots of articles about clouds here in Universe Today. For starters, here are two:
Cloud Types
Cirrus Clouds

Here are the links of two more articles from National Oceanic and Atmospheric Administration (NOAA):
Cloud Classifications and Characteristics
Western Region Technical Attachment
Here are two episodes at Astronomy Cast that you might want to check out as well:
Orbit of the Planets, Green Stars, and Oort Cloud Contamination
Sky Surveys