Category: Astronomy

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Astronomers have found three brown dwarfs with estimated masses of less than 10 times that of Jupiter, making them among the youngest and lowest mass sub-stellar objects detected in the solar neighborhood to date. “There has been some controversy about identifying young, low mass brown dwarfs in this region,” said Andrew Burgess, one of the astronomers who used the Canada-France-Hawaii Telescope (CFHT) to find the objects. “The fact that we have detected three candidate low-mass dwarfs towards IC 348 supports the finding that these really are very young objects.”

A team of astronomers from the Laboratoire d’Astrophysique de l’Observatoire de Grenoble (LAOG), France made the discovery, and Burgess presented their findings at the European Week of Astronomy and Space Science at the University of Hertfordshire.

The dwarfs were found in a star forming region named IC 348, which lies almost 1000 light years away, towards the constellation of Perseus. This cluster is approximately 3 million years old – extremely young compared to our 4.5 billion year old Sun – which makes it a good location in order to search for the lowest mass brown dwarfs. The dwarfs are isolated in space, which means that they are not orbiting a star, although they are gravitationally bound to IC 348. Their atmospheres all show evidence of methane absorption which was used to select and identify these young objects.

An object of a similar mass was discovered in 2002, but some groups have argued that it is an older, cooler brown dwarf in the foreground coinciding with the line of sight.

”Finding three candidate low-mass dwarfs towards IC 348 backs up predictions for how many low-mass objects develop in a new population of stars. Brown dwarfs cool with age and current models estimate that their surfaces are approximately 900-1000 degrees Kelvin (about 600-700 degrees Celsius). That’s extremely cool for objects that have just formed, which implies that they have the lowest masses of any of this type of object that we’ve seen to date,” said Burgess.

Source: RAS

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The Earth’s mantle, just a few dozen kilometers beneath your feet is incredibly hot. The high temperatures cause rocks to melt and form magma that collects in vast chambers beneath the Earth’s surface. Since it’s lighter than the surrounding rock, this magma makes its way up through weaknesses in the rock until it reaches the Earth’s surface erupting as a volcano. The spot where it erupts is known as a volcanic vent.

A volcanic vent is that spot in the Earth’s crust where gases, molten rock, lava and rocks erupt.

Volcanic vents can be at the top of some of the largest volcanoes on Earth, like Hawaii’s Mauna Kea, or they can be openings in the Earth’s crust down at the bottom of the ocean. The shape of the volcanic vent can sometimes define whether the volcano is explosive or not. A fissure vent can be a few meters wide and many kilometers long. Lava pours out of fissure vents, creating lava channels, but they don’t usually explode.

The tall familiar cone shaped stratovolcano (like Mount Fuji) can have one volcanic vent at the top of the mountain, but also have many smaller volcanic vents across the flanks of the volcano where smaller eruptions occur. These large volcanoes can erupt explosively, posing a great danger to people living nearby.

In the case of very viscous (or thick) lava, you can get a slow buildup of material into a lava dome. The lava is so thick that it doesn’t move very far from the volcanic vent. Instead it just plugs it up, forming a bulging dome of material. These can also explode violently.

We have written many articles about volcanoes for Universe Today. Here’s an article about different types of volcanoes. And here’s an article about underwater volcanoes.

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.

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Here on the surface of the Earth, the ground is relatively cool. But as you descend into the Earth, things get hotter and hotter, eventually reaching hundreds or even thousands of degrees C. The hot temperatures inside the Earth’s mantle can melt rock; this is magma.

Magma collects in large pools underneath the surface of the Earth in vast magma chambers. Because it’s lighter than the surrounding rock, it makes its way upwards through weaknesses in the Earth’s crust until it reaches the surface. When the magma reaches the surface, it can extrude as lava, or even erupt violently throwing up ash and even rocks.

The temperature of magma can range between 700 and 1300 degrees Celsius depending on the chemical composition of the rocks. You might be surprised to know that the interior of the Earth is a solid, not liquid. The magma only forms in regions where the temperatures are high and the pressures are low; typically within a few kilometers of the surface of the Earth.

The melted magma comes from rocks under huge temperatures and pressures. Most rocks are a collection of different minerals, which can have different melting points. When one part of the rock starts to melt, the rest remains solid. This causes the melted material to squeeze out in small globules. These globules collect together to fill up the magma chamber underneath a volcano.

All igneous rock found on the Earth was originally formed as magma.

We have written many articles about the Earth for Universe Today. Here’s an article about the difference between magma and lava.

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.

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All lava isn’t the same. There can be tremendous differences in the viscosity (thickness), temperature and chemical composition of lava. The least viscous (least syrupy) lava is known as pahoehoe, and it can flow for many kilometers away from the source of a volcanic eruption. One of the longest flows ever recorded was an eruption from Mauna Loa that was 47 km long.

In fact, when you think of an erupting volcano, with vast rivers of lava flowing out, that’s pahoehoe – it’s a Hawaiian term. It’s a basaltic lava that once hardened has a smooth, ropy surface. In fact, it can have such beautiful shapes that people call it lava sculptures. The strange shapes happen because the front of the lava flow forms a thin shell, and then blobs continually break out from the crust. These cool and then more lava breaks out from that.

Once the pahoehoe lava flows finally cool, the resulting rock is incredibly smooth; they’re smooth down to a scale of just a few millimeters. This is very different to aa lava flows, which feel like jagged glass once they harden. Pahoehoe is smooth and nice to walk across, while a’a lava will ravage your shoes and give you a nasty cut if you happen to fall on it.

We have written many articles about the Earth for Universe Today. Here’s an article about all the different types of lava, and here’s an article about a’a lava.

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.

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If you’ve ever visited the Big Island of Hawaii, you’ll get a chance to see one of nature’s most amazing formations: a lava tube. Lava tubes are natural tunnels where lava flows underneath the ground, sometimes for many kilometers. After the eruption is over, you can be left with a long empty tunnel that seems almost man made.

A lava tube happens when low viscosity lava forms a continuous hard crust that gets thicker and thicker, while lava is flowing inside it. Eventually the lava forms a thick hard crust above, but low viscosity lava continues to flow inside. In fact, the thick sides act like insulation to keep the inner lava hot and molten. When the eruption finally ends, the lava flows out of the tube, emptying it out.

Lava tubes can be many meters wide, and typically run several meters below the surface. One tube on Mauna Loa starts at the eruption point and then flows about 50 km to the ocean. Inside the tube there can be various formations, like lava stalactites known as lavacicles (named after icicles). You can also get pillars that stretch from the top to the bottom of the lava tube.

Some of the most well known lava tubes are Thurston Lava Tube in Hawaii Volcanoes National Park, and Lava Beds National Monument in Northern California.

We have written many articles about the Earth for Universe Today. Here’s an article about different types of lava. And here’s an article about lava flows in general.

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.

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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