Category: Astronomy

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The European Space Agency has extended operations of three missions: Mars Express, Venus Express and Cluster, until the end of the year, citing “excellent” research returns from all three missions. Each mission has been extended at least once in its history, said Monica Talevi, an ESA spokeswoman — but they’re all worth it.

“The scientific community recognizes and ESA recognizes that these missions have provided excellent results,” she said.

Mars Express

The first European mission to the Red Planet, Mars Express has been orbiting Mars since the end of 2003.  Besides high-resolution color images of the Martian surface, the spacecraft has also beamed back mineralogical evidence for the presence of liquid water throughout Martian history and studied the density of the Martian crust in detail. Mars Express was the first spacecraft to detect methane in the planet’s atmosphere from orbit. Its radar instrument, the first flown to Mars, has returned pioneering sub-surface sounding measurements that show underground deposits of water ice. The mission has also pioneered insights into the Martian atmosphere, including the detection of aurorae at mid-latitudes and new estimates for the rate at which Mars’ atmosphere escapes into space.

The mission has been extended twice in the past, with the most recent lasting until May 2009. This third extension will make it possible to continue with the mission’s study of the Red Planet which includes, among other inquiries: the study of its subsurface, the observation of the upper atmospheric layers under varying solar conditions, observation of methane in the atmosphere and high resolution mapping of its surface.

Venus Express 
 
Since it reached Venus in April 2006, Venus Express has been mapping Venus’s noxious and thick atmosphere globally and in 3D for the first time. With the data, scientists have put together extensive meteorological maps of Venus, providing measurements of wind fields and temperatures and the chemical composition of the atmosphere.

The spacecraft has peered at the planet’s dynamic cloud system, including its striking double-eyed atmospheric vortex that dominates the south pole. It’s found water molecules escaping into space, concrete evidence for lightning in the Venusian atmosphere, and infrared glimpses of the hot surface.

Previously extended once to last until May 2009, the next extended phase will be used to improve scientists’ understanding of how Venus’ climate works, and search for suspected active volcanism on the planet’s surface.

Cluster 

The Cluster constellation was launched in summer 2000 and started operating in early 2001. Since then, the four-satellite mission has been spying on the Earth’s own magnetosphere, the magnetic bubble surrounding our planet. Its work is yeilding new insights into the way solar activity affects the near-Earth environment.

Cluster pioneered measurements of electric currents in space, revealed the nature of black aurorae, and discovered that plasma — a gas of charged particles surrounding Earth — makes ‘waves.’ The mission also provided the first 3D observation of magnetic reconnection in space — a phenomenon that reconfigures the magnetic field and releases high amounts of energy.

The Cluster mission has been extended twice in the past, up to June 2009. The new extension will make it possible to study the auroral regions above Earth’s poles and widen the investigations of the magnetosphere, particularly its inner region.

Source: ESA

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Carbon stars are similar to red giant stars. It’s a late stage in the evolution of a star on its way to death. What makes a carbon star different from a regular red giant star is the fact that there’s more carbon than oxygen in its atmosphere. That’s a carbon star. I’m guessing you’re going to need a more complete explanation.

A star shines because it’s fusing elements in its core; usually hydrogen into helium. When a star runs out of fuel at its core, it stops putting out energy, and starts to collapse down. This collapse increases the pressure and temperature at the core, and allows a shell of hydrogen around the core to ignite. The star bursts to life again with thousands of times the luminosity it had before. This increased energy output bloats the star up until it becomes a red giant. When our Sun becomes a red giant, it will engulf the orbits of the inner planets: Mercury, Venus, and yes, even Earth.

Astronomers think there are a couple of ways that stars can gain larger amounts of carbon in their atmospheres. The first is the classical theory of carbon stars. Stars more massive than our Sun will be fusing helium in their cores when they reach a certain point in their lives. The output of these helium fusion reactions is carbon. Convection currents deep within the star carry the carbon upwards to the surface, where it’s deposited in the star’s outer atmosphere.

The second way carbon stars can appear is through a binary system. One star is a red giant, and the other star is a white dwarf. Millions of years ago, both the red giant and the white dwarf were main sequence stars, and during this period one star siphoned material off the other and collected it on its outer atmosphere. Today we see a red giant with an unusually high amount of carbon in its atmosphere.

We have written many articles about stars here on Universe Today. Here’s an article about pure carbon stars discovered, and here’s a theory that carbon stars might detonate as gamma ray bursts.

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 have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

Reference:
Wikipedia

As you know, everything in the Universe is extremely far away. Even the closest stars take more than 4 years for light alone to reach. Since astronomers can’t actually reach out and sample stars, have you ever wondered how they determine the age of stars, and how long they have to live?

Fortunately, the trusty telescope tells astronomers all they need to know about the age of stars. Essentially, astronomers determine the age of stars by observing their spectrum, luminosity and motion through space. They use this information to get a star’s profile, and then they compare the star to models that show what stars should look like at various points of their evolution. From this, they can determine how old a star is, and how much longer it has to live. This method of determining star age can inaccurate because it relies on the accuracy of the models.

There’s a new technique that was recently developed called gyrochronology, and it’s based on the rotational speed of a star. The speed that a star rotates is steadily changing throughout its life, and it’s dependent on the star’s age and color. If you know a star’s color and rotational speed, you can calculate its age to within an uncertainty of 15%.

Our Sun, for example, has been around for 4.6 billion years, and astronomers think that it should last for another 7 billion years or so before becoming a red giant star.

We have written many articles about stars here on Universe Today. Here’s an article about how older stars seem to lack lithium, and here’s one about how astronomers determined the age of the Milky Way.

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 have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

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Astronomers classify stars into groups according to their color and the presence of elements in the stars’ spectral signatures. This star classification system goes like this: O, B, A, F, G, K, M (here’s a way to remember them: “Oh be a fine girl, kiss me”.) M stars are coolest and most common stars in the Universe.

M stars range in temperature from 2,500 Kelvin and go all the way up to 3,500 Kelvin. They look red to our eyes. M stars account for 75% of the stars in our stellar neighborhood, so they’re the most common by far! Most M stars are tiny red dwarfs, with less than 50% of the mass of the Sun, but some are actually giants and supergiants, like the red giant Betelgeuse.

Some familiar M stars include Betalgeuse (red giant), and the red dwarfs Proxima Centauri, Barnard’s star, and Gliese 581

We have written many articles about stars here on Universe Today. Here’s an article about how red dwarf stars have small habitable zones.

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 have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

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To organize all the stars in the Universe, Astronomers use a classification system that collects the stars into groups based on their color and the presence of various elements in the star’s outer atmosphere. So, here are the classifications: O, B, A, F, G, K, M (if you need to remember then, just keep this in mind: “Oh be a fine girl, kiss me”.) K stars are cooler than the Sun.

K stars start at about 3,500 Kelvin, and can get as hot as 5,000 Kelvin. This makes them look orange-red to our eyes. K stars can actually vary in size from main sequence stars with less mass than the Sun to red giants and supergiants with many times the mass of the Sun. It’s all because of the temperature. They have weak hydrogen lines and mostly neutral metals, like Manganese, Iron and Silicon. About 13% of stars in the stellar neighborhood are K stars.

Some familiar K stars include Alpha Centauri B, Epsilon Eridani, Arcturus, Aldebaran

We have written many articles about stars here on Universe Today. Here’s an article about the closest known star with extrasolar planets, Epsilon Eridani.

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 have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

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Astronomers collect the stars in the Universe into a classification system that organized them by color and spectral signature (the presence of various metals in the star’s outer atmosphere). Here are the classifications: O, B, A, F, G, K, M (if you need to remember then, just keep this in mind: “Oh be a fine girl, kiss me”.) G stars are perhaps the best known stars out there. That’s because our own Sun is a G star.

G stars range in temperature from 5,000 Kelvin to 6,000 Kelvin, and they appear white or yellow-white to our eyes. You can also recognize a G star by the presence of Calcium in their spectral signature, but with weaker hydrogen lines than F type stars. G stars represent 7.7% of all the stars in our stellar neighbourhood.

Some familiar G stars include The Sun, Alpha Centauri A, Capella, Tau Ceti

We have written many articles about stars here on Universe Today. Here’s an article about the search for planets around Alpha Centauri.

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 have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

Astronomers classify the stars out there into groups based on the color of the star and the presence of certain elements in the star’s atmosphere. The classifications are: O, B, A, F, G, K, M (just remember this handy mnemonic , “Oh be a fine girl, kiss me”.) F stars are still hotter than the Sun, appearing white to our eyes.

F stars have a surface temperature of 6,000 Kelvin to 7,200 Kelvin. You can also recognize an F star by the presence of Calcium in their spectral signature, as well as neutral metals like Iron and Chromium. F stars represent 3.1% of all stars.

Some familiar F stars include Arrakis, Canopus, Procyon.

We have written many articles about stars here on Universe Today. Here’s an article about some strange observations of Procyon.

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 have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

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Astronomers have developed a star classification system to organize all the stars we can see in the Universe; it’s based on color and the spectral signature of certain elements in the star’s atmosphere. The classifications are: O, B, A, F, G, K, M (here’s a handy mnemonic , “Oh be a fine girl, kiss me”.) A stars are some of the more common stars seen with the unaided eye: they appear white or bluish-white.

The surface temperatures of A stars range from 7,400 Kelvin to 10,000 Kelvin; that’s about twice the temperature of the Sun, so these stars are really hot. Astronomers also recognize them by the strong hydrogen lines, as well as lines of ionized metals, like Iron, Magnesium and Silicon. A stars are more massive than the Sun, but don’t lead lives that are too much different than the life of our own Sun.

Some familiar A stars include Vega, Sirius, and Deneb.

We have written many articles about stars here on Universe Today. Here’s an article about how Vega has a cool, dark equator, and it might even have planets.

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 have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?

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Astronomers have developed a method of classifying stars based on their color and some other characteristics. The star classifications are O, B, A, F, G, K, M (you can remember that with the handy mnemonic, “Oh be a fine girl, kiss me”.) O stars are the most extreme group of all. They have the highest temperatures, the most luminosity, and the most mass (oh, and the shortest lives).

An O star appears blue to the eye, and can have a surface temperature of more than 41,000 Kelvin; its color would be better described as ultraviolet, but we can’t see that color with our eyes. The surface temperature of an O star is so great that hydrogen on the surface of the star is completely ionized, but other elements are more visible, like Helium, Oxygen, Nitrogen, and Silicon.

O stars are very massive and evolve very rapidly. Shortly after they form as a protostar, they already have the pressure and temperatures in their cores to begin hydrogen burning. The O stars light up their stellar nurseries with ultraviolet light and cause the clouds of nebula to glow. You can thank O stars for illuminating the beautiful nebula photographs captured by Hubble. O stars burn through their fuel quickly, and can detonate as supernovae in just a few million years.

Some O stars include Zeta Orionis, Zeta Puppis, Lambda Orionis, Delta Orionis.

We have written many articles about stars here on Universe Today. Here’s an article about an O star.

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 have recorded several episodes of Astronomy Cast about stars. Here are two that you might find helpful: Episode 12: Where Do Baby Stars Come From, and Episode 13: Where Do Stars Go When they Die?