Category: Astronomy

[/caption]
Volcanoes can erupt with ash and rocks, but one of the most common images are great rivers of molten lava streaming from the volcano’s vent. This molten lava is made of rock, heated to more than 700 degrees C inside the Earth. Inside the Earth, it’s called magma, but when it reaches the surface, scientists call it molten lava.

You might be surprised to know that there are many different kinds of molten lava, depending on the chemical structure of the rock itself. This structure defines how viscous the lava is; how easily it flows. Think of the difference between water and syrup. Syrup is very viscous. Molten lava can be 100,000 times as viscous as water.

The least viscous lava can flow great distances from a volcano during an eruption, sometimes traveling many kilometers, destroying everything in its path. Volcanoes with this kind of molten lava are called shield volcanoes and they take on a very wide, low appearance, since the lava can flow so far. Other types of lava are thicker, or more viscous. It only travels a short distance in thick, crumbling flows. And some molten lava is so thick that it doesn’t really flow at all. It just piles up around the volcanic vent.

When it first erupts from the volcanic vent, molten lava can be anywhere from 700 to 1200 degrees Celsius. The thickness (or viscosity) defines how the lava behaves as it leaves the vent, and how far it can flow downhill before cooling and solidifying. Even though it looks solid, a lava flow can remain hot for weeks and even years before it finally cools.

As scary as it looks, molten lava really isn’t that dangerous for people. You can easily outrun a lava flow. Of course, buildings and trees aren’t so lucky since they’re attached to the ground.

We have written many articles about volcanoes for Universe Today. Here’s an article about the largest volcano in the Solar System, and here’s an article about the biggest volcano on Earth.

Want more resources on the Earth? Here’s a link to NASA’s Human Spaceflight page, and here’s NASA’s Visible Earth.

We have also recorded an episode of Astronomy Cast about Earth, as part of our tour through the Solar System – Episode 51: Earth.

It may be a while yet before astronomers agree on a standard model for planet formation around stars. Until recently, after all, Earthlings lacked reliable techniques for glimpsing much beyond our own solar system.

Based on our own backyard, one prevailing theory is that rocky planets like Mercury, Earth and Mars form slowly, close to the sun, from collisions of smaller, solid bodies while gas giants form faster, and farther from the star — often within the first two million years of a star’s life — from smaller rocky cores that readily attract gases.

But new data are suggesting that some gas giants form close to their stars — so close that intense stellar winds rob them of those gases, stripping them back to their cores.

An international research team has found that giant exoplanets orbiting very close to their stars — closer than 2 percent of an Astronomical Unit (AU) — could lose a quarter of their mass during their lifetime. An AU is the distance between the Earth and the Sun.

Such planets may lose their atmospheres completely.

The team, led by Helmut Lammer of the Space Research Institute of the Austrian Academy of Sciences, believes that the recently discovered CoRoT-7b “Super Earth,” which has less than twice the mass of the Earth, could be the stripped core of a Neptune-sized planet.

The team used computer models to study the possible atmospheric mass loss over a stellar lifecycle for exoplanets at orbiting distances of less than 0.06 AU, where the planetary and stellar parameters are very well known from observations. 

Mercury is our only neighbor orbiting the Sun in that range; Venus orbits at about .72 AUs.

The 49 planets considered in the study included hot gas giants, planets with masses similar or greater than that of Saturn and Jupiter, and hot ice giants, planets comparable to Uranus or Neptune. All the exoplanets in the sample were discovered using the transit method, where the size and mass of the planet is deduced by observing how much its parent star dims as it the planet passes in front of it.

“If the transit data are accurate, these results have great relevance for planetary formation theories,” said Lammer, who is presenting results at the European Week of Astronomy and Space Science, April 20-23 at the University of Hertfordshire in the UK.

“We found that the Jupiter-type gas giant WASP-12b may have lost around 20-25 percent of its mass over its lifetime, but that other exoplanets in our sample had negligible mass loss. Our model shows also that one major important effect is the balance between the pressure from the electrically charged layer of the planet’s atmosphere and the pressure from the stellar wind and coronal mass ejections (CMEs). At orbits closer than 0.02 AU, the CMEs — violent explosions from the star’s outer layers — overwhelm the exoplanet’s atmospheric pressure causing it to lose maybe several tens of percent of its initial mass during its lifetime.”

The team found that gas giants could evaporate down to their core size if they orbit closer than 0.015 AU. Lower-density ice giants could completely lose their hydrogen envelope at 0.045 AU. Gas giants orbiting at more than 0.02 AU lost about 5-7 percent of their mass. Other exoplanets lost less than 2 percent. Results suggest that CoRoT-7b could be an evaporated Neptune-like planet but not the core of a larger gas giant. Model simulations indicate that larger mass gas giants could not have been evaporated to the mass range determined for CoRoT-7b.

For more information:

The European Week of Astronomy and Space Science
The Royal Astronomical Society

Is your mouth watering? It should be. That molecule at left is called ethyl formate  (C2H5OCHO), and it’s partly responsible for the flavors in brandy, butter, raspberries and rum.

 

 

As for this one, it’s a solvent called n-Propyl cyanide (C3H7CN); not so tasty. 

They’re both highly complex organics, and they’ve both been detected in space, according to new research — adding mouth-watering evidence to the search for extra-terrestrial life.

The research team hails from Cornell University in Ithaca, New York and the University of Cologne and the Max Planck Institute for Radio Astronomy (MPIfR), both in Germany. Their discoveries represent two of the most complex molecules yet discovered in interstellar space. 

To make the observations, the team used the Institut de RadioAstronomie Millimétrique (IRAM) 30m Telescope at Pico Veleta in southern Spain. 

Their computational models of interstellar chemistry also indicate that yet larger organic molecules may be present — including the so-far elusive amino acids, believed to be essential for life. The simplest amino acid, glycine (NH2CH2COOH), has been looked for in the past, but has not been successfully detected. However, the size and complexity of this molecule is matched by the two new molecules discovered by the team.

The results are being presented this week at the European Week of Astronomy and Space Science at the University of Hertfordshire, in the UK.

The IRAM was focused on the star-forming region Sagittarius B2, close to the centre of our galaxy. The two new molecules were detected in a hot, dense cloud of gas known as the “Large Molecule Heimat,” which contains a luminous newly-formed star. Large, organic molecules of many different sorts have been detected in this cloud in the past, including alcohols, aldehydes, and acids. The new molecules ethyl formate n-propyl cyanide  represent two different classes of molecule — esters and alkyl cyanides — and they are the most complex of their kind yet detected in interstellar space.

Atoms and molecules emit radiation at very specific frequencies, which appear as characteristic “lines” in the electromagnetic spectrum of an astronomical source. Recognizing the signature of a molecule in that spectrum is akin to identifying a human fingerprint.

“The difficulty in searching for complex molecules is that the best astronomical sources contain so many different molecules that their “fingerprints” overlap, and are difficult to disentangle,” says Arnaud Belloche, scientist at the Max Planck Institute and first author of the research paper.

“Larger molecules are even more difficult to identify because their “fingerprints” are barely visible: their radiation is distributed over many more lines that are much weaker,” added Holger Mueller, researcher at the University of Cologne. Out of 3,700 spectral lines detected with the IRAM telescope, the team identified 36 lines belonging to the two new molecules.

The researchers then used a computational model to understand the chemical processes that allow these and other molecules to form in space. Chemical reactions can take place as the result of collisions between gaseous particles; but there are also small grains of dust suspended in the interstellar gas, and these grains can be used as landing sites for atoms to meet and react, producing molecules. As a result, the grains build up thick layers of ice, composed mainly of
water, but also containing a number of basic organic molecules like methanol, the simplest alcohol. 

“But,” says Robin Garrod, an astrochemist at Cornell University, “the really large molecules don’t seem to build up this way, atom by atom.” Rather, the computational models suggest that the more complex molecules form section by section, using pre-formed building blocks that are provided by molecules, such as methanol, that are already present on the dust grains. The computational models show that these sections, or “functional groups,” can add together efficiently, building up a molecular “chain” in a series of short steps. The two newly-discovered molecules seem to be produced in this way.

Adds Garrod, “There is no apparent limit to the size of molecules that can be formed by this process — so there’s good reason to expect even more complex organic molecules to be there, if we can detect them.”

The team believes this will happen in the near future, particularly with future instruments like the Atacama Large Millimeter Array (ALMA) in Chile.

Sources: Royal Astronomical Society. The original paper is in press in the journal Astronomy & Astrophysics.

European Week of Astronomy and Space Science
Max Planck Institute for Radio Astronomy 
Cologne Database for Molecular Spectroscopy
Reference list of all 150 molecules presently known in space
Cornell University
Institut fuer Radioastronomie im Millimeterbereich (IRAM)
Atacama Large Millimeter Array (ALMA)

An international team, led by astronomers at the University of Hertfordshire in the UK, has discovered one of the coolest sub-stellar bodies ever found outside our own solar system.

The new object — dubbed Wolf 940B — orbits the red dwarf star Wolf 940, 40 light years from Earth. It’s thought to have formed like a star, but has ended up looking more like Jupiter. It is roughly the same size, despite being between 20 and 30 times as heavy, and when the infrared spectral “fingerprints” of the two objects are compared, their resemblance is striking, say Wolf 940B’s discoverers.

Wolf 940B was initially discovered as part of a major infrared sky survey – the UKIRT Infrared Deep Sky Survey (UKIDSS) which is being carried out using the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea in Hawaii. The telescope’s wide field camera is the long black tube in the image at left.

The object was found as part of a wider effort to find the coolest and least luminous bodies in our local Galactic neighborhood, but it was then found to be a companion to the nearby red dwarf Wolf 940 through its common motion across the sky. The data used to confirm the discovery were obtained using telescopes in Chile, the Canary Islands and Hawaii.

Its temperature was then confirmed using data from the Gemini-North telescope on Mauna Kea. The findings are being reported at the European Week of Astronomy and Space Science (NAM 2009) at the University of Hertfordshire, and will soon be published in the Monthly Notices of the Royal Astronomical Society.

The new object orbits its star at about 440 times the distance at which the Earth orbits the sun. At such a wide distance, it takes about 18,000 years to complete a single orbit.

Too small to be stars, so-called “brown dwarfs” have masses lower than stars but larger than gas giant planets like Jupiter. Due to their low temperatures, these objects are very faint in visible light, and are detected by their glow at infrared wavelengths.

“Although it has a temperature of 300 degrees Celsius [572 degrees F], which is almost hot enough to melt lead, temperature is relative when you study this sort of thing, and this object is very cool by stellar standards,” said Ben Burningham, of the University of Hertfordshire. “In fact, this is the first time we’ve been able to study an object as cool as this in such detail. The fact that it is orbiting a star makes it extra special.”

Modeling the atmospheres of cool brown dwarfs is a complex task, but it is key to understanding planets that orbit other stars. Models of emitted light from such objects, which are dominated by absorption due to water and methane gas, are sensitive to assumptions about their age and chemical make-up.

In most cases, astronomers don’t initially know much about the age and composition of brown dwarfs — and this can make it hard to tell where the models are right, and where they are going wrong.

“What’s so exciting in this case, is that we can use what we know about the primary star to find out about the properties of the brown dwarf, and that makes it an extremely useful find,” Burningham said. “You can think of it as a Rosetta Stone for decrypting what the light from such cool objects is telling us.”

Wolf 940A, the red dwarf star that is Wolf 940B’s namesake, was first catalogued by the pioneering German astronomer Max Wolf 90 years ago.

“Red dwarfs are the most populous stars in the Galaxy, and systems like this may be more common than we know” said David Pinfield, also of the University of Hertfordshire. “As the generation of ongoing large scale surveys continues, we may discover a pack of Wolf-940B-like objects in our solar back yard.”

Source: Joint Astronomy Centre. For more information, visit: 

The UK Infrared Telescope
NAM 2009
Gemini Observatory