Posts Tagged ‘Star’

Brown Dwarf

April 29, 2014

Astronomers have recently discovered a previously unknown star only 7.2 light years away. You might wonder how they could miss a star that close to us. Well, Wise J085510.83-071442.5 is not a regular star. It is a brown dwarf, a star that doesn’t actually shine. Here is the story according to the Daily Mail

A brown dwarf star that appears to be the coldest of its kind – as frosty as Earth’s North Pole – has been spotted by an American astronomer.

The discovery was made using Nasa’s Wide-field Infrared Survey Explorer (Wise) and the Spitzer Space Telescope.

Images from the space telescopes also pinpointed the object’s distance at 7.2 light years away, making it the fourth closest system to our sun.

‘It is very exciting to discover a new neighbour of our solar system that is so close,’ said Kevin Luhman, an associate professor of astronomy and astrophysics at Penn State and a researcher in the Penn State Center for Exoplanets and Habitable Worlds.

‘In addition, its extreme temperature should tell us a lot about the atmospheres of planets, which often have similarly cold temperatures.’

Brown dwarfs start their lives like stars, as collapsing balls of gas, but they lack the mass to burn nuclear fuel and radiate starlight.

The newly-found brown dwarf, named Wise J085510.83-071442.5, is thought to have a chilly temperature between -48°C to -13°C (-54°F to 9°F).

Previous record holders for coldest brown dwarfs, also found by Wise and Spitzer, were about room temperature.

To understand what a brown dwarf actually is, you must realize that like people, stars are born, they live, and eventually they die. A star’s lifespan is measured in eons rather than years and they take little notice of such microscopic mayflies such as we are. A star is born when a massive cloud of gas collapses in on itself. If you recall your high school physics class, you may remember that when a gas is compressed, in this case by the protostar’s gravity, it will heat up. The energy used in compressing the gas is converted into heat. If the protostar’s mass is greater than about .08 solar masses (8% of our Sun), the center of the cloud will become dense enough and hot enough to begin fusing hydrogen into helium. A new star is born. If the mass is less than .08 solar masses than fusion will never begin and the star is stillborn. It becomes a brown dwarf.

Some of the more massive brown dwarves, around 13 to 65 Jupiter masses may fuse deuterium and lithium. They emit mostly infrared radiation. Interestingly, brown dwarves are about the same volume as Jupiter, regardless of their masses. Gravity compresses them to about the same volume. In a way, Jupiter, Saturn, and Neptune could be considered to be very low mass brown dwarves. They emit more energy than they receive from the sun. Perhaps the precise line between a massive planet and a very low mass star is not so easy to define.

General size comparison between a low mass sta...

 (Photo credit: Wikipedia)

A brown dwarf should not be confused with a red dwarf or a white dwarf. A red dwarf is a real star with a mass from about .08 to .5 solar masses. They are small and dim but they do fuse hydrogen in their core and they emit visible light. A white dwarf is a dead star. It has run out of fuel and has collapsed under its own mass until only electron degeneracy, the pressure of electrons crammed together, prevents it from collapsing any further.

But stellar corpses are another topic which I will have to write about another time.

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Star Birth

August 22, 2013

Everybody in Britain was excited about the birth of the new prince. That’s understandable, considering the importance of continuing the royal line, but astronomers have been recording a somewhat more significant birth, the birth of a new star. Here is the story and pictures from Yahoo News.

A huge radio telescope in Chile has captured dazzling new views of a baby star lighting up an interstellar cloud with jets of gas streaking through deep space at record-breaking speeds.

The ALMA radio telescope, a joint project between North America, Europe and Asia, recorded the star birth images. They show the nascent star about 1,400 light-years from Earth unleashing material at nearly 84,477 mph (144,000 km/h), which then crashes into surrounding gas, causing it to glow.

The glowing object spawned by the newborn star is what scientists call a Herbig-Haro object. European Southern Observatory officials used the new views to create a video tour of new star birth images.

These new, detailed images showed that the material is streaking out of the star at about 40 kilometers per second (nearly 25 miles per second), which is about four times faster than any previous observation of carbon monoxide jets, scientists said. The discovery may help researchers understand the complex processes stars undergo during their birth.

The sun is a star, so if we want to understand how our solar system was created, we need to understand how stars are formed,” Héctor Arce, the lead author of the study appearing in the Astrophysical Journal on Aug. 20, said in a statement.

 The new image of Herbig-Haro 46/47 (HH 46/47) produced by the ALMA telescope, its name is short for Atacama Large Millimeter/submillimeter Array, reveals two jets of material streaming away from the newborn star, one of which was never detected before.

 One jet appears on the left side of the photo in pink and purple streaming partially toward Earth, while the orange and green jet on the right-hand-side show a jet pointed away from Earth.

 “This system is similar to most isolated low mass stars during their formation and birth,” Diego Mardones, a co-author of the study detailing the stellar findings said in a statement. “But it is also unusual because the outflow impacts the cloud directly on one side of the young star and escapes out of the cloud on the other. This makes it an excellent system for studying the impact of the stellar winds on the parent cloud from which the young star is formed.”

ALMA’s sensitive instruments took five hours to get these results. Earlier photos taken with other telescopes did not catch the second (orange and green) jet stream because dust surrounding the star obscured their views.

“ALMA’s exquisite sensitivity allows the detection of previously unseen features in this source, like this very fast outflow,” Arce said. “It also seems to be a textbook example of a simple model where the molecular outflow is generated by a wide-angle wind from the young star.”

 The $1.3 billion ALMA radio telescope is an array of 66 of individual radio telescopes that create one of the most powerful telescopes ever built. Each dish is up to 40 feet wide (12 meters) and can weigh 115 tons. The combined effort of the telescopes allows scientists to see celestial sights invisible in optical light because they are masked by gas and dust.

Here are some baby pictures.

Isn’t he the cutest thing. I think we should name him George.





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