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A powerful telescope in Chile has imaged the largest yellow star ever discovered.
The star, called HR 5171 A, shines 12000 ly from Earth in the center of a new image released today (March 12). Known as a "yellow hypergiant,"



The star is more than ..... wait for it ...... 1300 times the diameter of the sun

HR 5171 A is 50% larger than the red supergiant Betelgeuse.

The observations showed that this star has a very close binary partner. The two stars are so close that they touch and the whole system resembles a gigantic peanut.

The star shines ~ 1 million times brighter than the sun. Can be spotted with the naked eye.
 
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it really does hurt my brain sometimes when i think too deep about the size of
these stars in comparison to our own.

why is the star yellow at this size though?

maybe it changes colour later on.
 
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I agree, Stuart. It's mind blowing. And I agree about the color. Maybe it'll get redder in some million years. We'll have to wait and see lol
 
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How can another star be so close to such a massive star and not collide with it due to the gravitational pull? The universe never ceases to amaze me and humble my limited human reasoning :oops:

Thanks for this most interesting post.
 
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Feed it some iron
 
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Feed it some iron
I would think you would need an amount of pure iron equivalent to the sun to make a dent.

it really does hurt my brain sometimes when i think too deep about the size of
these stars in comparison to our own.

why is the star yellow at this size though?

maybe it changes colour later on.
If I recall the color of a star isn't entirely dependant on the size, but more of the chemical composition (so to speak) of it which affects the rate of fusion within the star. There are generally speaking, a lot of outliers when it comes to outer space :p
 
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If I recall the color of a star isn't entirely dependant on the size, but more of the chemical composition (so to speak) of it which affects the rate of fusion within the star. There are generally speaking, a lot of outliers when it comes to outer space :p
Star's colour depends solely on its temperature and nothing else. Basically all stars are made of the same stuff.

 
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Astronomers used ALMA to study the well-known cool, dim red dwarf star TVLM 513-46546, which is located ~ 35 ly from us in the constellation Boötes.

The star is a mere 10% the mass of the Sun and is so small and cool that it's right on the dividing line between stars (which fuse hydrogen) and brown dwarfs (which don't). One of the things that make this small star remarkable is that it spins rapidly, completing a full rotation about every two hours. Our Sun takes about 25 days to rotate once at its equator. What's more, this star exhibits a magnetic field that rivals the Sun's most extreme magnetic regions and is several hundred times stronger than the Sun's average magnetic field.

When the researchers examined the star with ALMA they detected emission at a particularly high frequency (95 GHz or a wavelength of about 3 mm). Such a radio signal is produced by a process known as synchrotron emission, in which electrons zip around powerful magnetic field lines: the more powerful the magnetic field, the higher the frequency.


Radio emission from TVLM 513-46546. The time between each bright pulse corresponds to 1.958 hours, which is the period of rotation of the dwarf.
Astronomers will study similar stars in the future to determine whether this one is an oddball or an example of an entire class of stormy stars.
 
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Gamma Velorum

This system contains two stars (30 and 10 Solar Mass). Their orbital parameters are well-studied and they are separated by about the same distance as Earth and Sun. This binary system is ~ 200 000 times more luminous than the Sun and strong stellar winds have very high mass loss rate: 10^-5 and 2*10^-7 of a solar mass per year. Though these figures seem to be small, actually this amount is huge, particularly comparing to the solar wind which only amounts to 10^-14 solar mass per annum. As the stellar winds in the Gamma Velorum system collide on a speed exceeding 1000 km/s, particles are accelerated in the shock. Though an exact mechanism of this acceleration is still unknown, it definitely leads to a high energy photon radiation.
 
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Star HD 209458 is similar to our Sun and lies 150 ly from us in the constellation of Pegasus. This star harbors a close-in giant planet that transits across the star's disk.

 

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:):):)
Basically all stars are made of the same stuff.
:) Does this include the ones made from Dark Matter if they exist :)

"Oh and its not a piss take "
if Enough Dark Matter exists then its possible for enough to accumulate like Normal matter to form a Dark Matter Sun !!!!!
 
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:):):)


:) Does this include the ones made from Dark Matter if they exist :)

"Oh and its not a piss take "
if Enough Dark Matter exists then its possible for enough to accumulate like Normal matter to form a Dark Matter Sun !!!!!

Yes and that's a really interesting question/theory. I remember the articles and I even have original links in my bookmarks:

http://www.nature.com/news/physicists-see-potential-dark-matter-from-the-sun-1.16174
http://physicsworld.com/cws/article/news/2015/feb/23/could-the-sun-be-trapping-asymmetric-dark-matter
https://physics.aps.org/synopsis-for/10.1103/PhysRevLett.114.081302

Unfortunately it's still unknown whether our Sun (and other stars) contain dark matter within their cores.
 
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Cygnus X-1 is ~ 10 000 ly years from Earth and one of the brightest high-energy emitters in the sky. It was discovered in the 1960s and is thought to be a black hole, ripping its companion star to pieces. The companion star, HDE 226868, is a blue supergiant with a surface temperature of ~ 31 000K. It orbits the black hole once every 5.6 days.

 
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Emission-line star IRAS 12196-6300.

Located just under 2300 ly from Earth, this star displays prominent emission lines. Under 10 million years old and not yet burning hydrogen at its core this star is still in its infancy. Further evidence of IRAS 12196-6300's youth is provided by the presence of reflection nebulae. These hazy clouds, pictured floating above and below IRAS 12196-6300, are created when light from a star reflects off a high concentration of nearby dust, such as the dusty material still remaining from IRAS 12196-6300's formation.
 
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Researchers using ALMA have observed late-phase protostar named TMC-1A located 450 ly away from us, in the constellation Taurus. The mass of the baby star is 0.68 times the mass of the Sun.



Dense gas seen around the baby star is shown in red. Outflowing gas is shown in white. The position of the star is indicated with a cross.

Stars form in dense gas clouds. Baby stars grow by taking in the surrounding gas. In this process, gas cannot flow directly into the star. Instead it first accumulates and forms a disk around the star, and then the disk feeds into the star.

Gas motion around TMC-1A. The red color indicates gas is moving away from us while the blue color is coming closer to us.

Gas is infalling to the disk from the envelope further out. Astronomers found that the boundary between the disk and envelope is located 90 AU (3 times longer than the orbit of Neptune) from the central baby star. As the baby star grows, the boundary between the disk and the infall region moves outward.

The gas infall rate to be a millionth of the mass of the Sun per year, with a speed of 1 km/s. Gravity causes gas to fall towards the central baby star, but the measured speed is much less than the free-fall speed. Something must be slowing the gas down. The researchers suspect that a magnetic field around the baby star might be what is slowing the gas.


 
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Nostalgic photos:



Star called CoRoT-2a is blasting a planet in its orbit with an extremely high level of X-rays. This high-energy radiation is eroding the planet at a rate of 5 million tons of material per second. The planet, in turn, may be speeding up the star's rotation, which keeps the star's magnetic fields very active. This system is ~ 880 ly from Earth and it's 100-300 million years old. The separation between the star and the planet is only 3% of the distance between the Earth and the Sun (AU).



The star CoRoT-7 is located towards the constellation of Monoceros at a distance of ~ 500 ly. Slightly smaller and cooler than our Sun, CoRoT-7 is also thought to be younger, with an age ~ 1.5 billion years. It's now known to have two planets, one of them being the first to be found with a density similar to that of Earth. CoRoT-7 is in the center of the image.
 
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The image on the left from NASA's Chandra X-ray Observatory shows the first double-sided X-ray jet ever detected from a young star, named DG Tau. A similar jet may have been launched from the young Sun and could have had a significant impact on the early solar system.

DG Tau is located in the Taurus star-forming region, ~ 450 ly from us. The bright source of X-rays in the middle of the image is DG Tau and the jet runs from the top left to the bottom right, extending to about 70 billion miles away (~ 700 AU) from the star.

DG Tau has about the same mass as the Sun, but is much younger with an age of about one million years. X-ray irradiation of disks may be important in the production of complex molecules in the disk that will later end up on the forming planets.
 
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The Very Large Telescope Interferometer at ESO's Paranal Observatory in Chile has obtained the sharpest view ever of the dusty disc around an aging star.

This is so cool that I almost peed my pants lol :D



Their target was the old double star IRAS 08544-4431, lying ~ 4000 ly from Earth in the southern constellation of Vela. This double star consists of a red giant star, which expelled the material in the surrounding dusty disc, and a less-evolved more normal star orbiting close to it.

The most prominent feature of the image is the clearly resolved ring.

The team finds that discs around old stars are indeed very similar to the planet-forming ones around young stars. Whether a second crop of planets can really form around these old stars is yet to be determined, but it is an intriguing possibility.
 
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VY Canis Majoris in Polarized and Visible light





VY Canis Majoris, also known as VY CMa, HD 58061 or HIP 35793, is a red hypergiant located in the constellation Canis Major.

This star is 3840 ly distant from Earth and is one of the largest known stars.

According to astronomers, VY Canis Majoris has a radius of approximately 1420 solar radii. It is about 35 times the mass of our Sun and 300 000 times more luminous.

VY Canis Majoris sees 30 times the mass of Earth expelled from its surface in the form of dust and gas every year. Analysis of the polarization results revealed these particles to be comparatively large particles, 0.5 micrometers across, which may seem small, but grains of this size are about 50 times larger than the dust normally found in interstellar space. These are big enough to be pushed away by the star's intense radiation pressure, which explains the star's rapid mass loss.
 

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The top image of CMa looks so awesome on my phone. I desperately want a high res version for my desktop.
 
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I really hope that nextgen telescopes will provide sharper images of VY Cma and Kappa Ceti. BTW forgot to add this old article:

Detection of two titanium oxides around the giant star VY Canis Majoris

The observations of TiO and TiO2 show that the two molecules are easily formed around VY CMa at a location that is more or less as predicted by theory. It seems, however, that some portion of those molecules avoid forming dust and are observable as gas phase species. Another possibility is that the dust is destroyed in the nebula and releases fresh TiO molecules back to the gas. The latter scenario is quite likely as parts of the wind in VY CMa seem to collide with each other.

Another interesting star:

Kappa Ceti



Kappa Ceti located 30 ly away in the constellation Cetus, is remarkably similar to our Sun but younger. It's only 400-600 million years old.

Like other stars its age, Kappa Ceti is very magnetically active. Its surface is blotched with many giant starspots. It also propels a steady stream of plasma out into space. This stellar wind is 50 times stronger than our Sun's solar wind.

Kappa Ceti also shows evidence of "superflares" that release 10 to 100 million times more energy than the largest flares ever observed on our Sun. Flares that energetic can strip a planet's atmosphere.
 
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Astronomers used the VLA to see unprecedented detail of the inner portion of a dusty disk surrounding the star, called HL Tau, some 450 ly from us.

HL Tau is only about a million years old - very young by stellar standards.

The ALMA image showed details of the system in the outer portions of the disk, but in the inner portions of the disk, nearest to the young star, the thicker dust is opaque to the short radio wavelengths received by ALMA. To study this region, astronomers turned to the VLA, which receives longer wavelengths. Their VLA images show that region better than any previous studies.

The new VLA images revealed a distinct clump of dust in the inner region of the disk. The clump contains roughly 3-8 times the mass of the Earth.

Analysis of the VLA data indicates that the inner region of the disk contains grains as large as 1cm in diameter. This region is presumably where Earth-like planets would form, as clumps of dust grow by pulling in material from their surroundings. Eventually, the clumps would gather enough mass to form solid bodies that would continue to grow into planets.
 
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Astronomers using the unique UV capabilities of Hubble Space Telescope have identified 'monster' stars in the star cluster R136.

R136 is only a few ly across and is located in the Tarantula Nebula within the Large Magellanic Cloud, ~ 170 000 ly away. The young cluster hosts many extremely massive, hot and luminous stars whose energy is mostly radiated in the UV.


This new study was able to reveal 9 very massive stars in the cluster, all > 100 times more massive as the Sun. The detected stars are not only extremely massive, but also extremely bright. Together these 9 stars outshine the Sun by a factor of 30 million.

The scientists were also able to investigate outflows from these behemoths. They eject up to an Earth mass of material per month at a speed approaching 1% of the speed of light, resulting in extreme weight loss throughout their brief lives.

 
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This false-color near-infrared image has been processed to remove most of the scattered light from the star Kappa Andromedae (masked out at center). The "super-Jupiter" companion, Kappa Andromedae b (upper left), lies at a projected distance of about 55 AU or about 1.8 times farther than Neptune, whose orbit is shown for comparison (dashed circle). The white region marking the companion indicates a signal present in all near-infrared wavelengths, while colored blobs represent residual noise.



Scientists focused on the star Kappa Andromedae because of its relative youth - estimated at the tender age of 30 million years, or just 0.7% the age of our Sun, based on its likely membership in a stellar group known as the Columba Association. The B9-type star is located 170 ly away in the direction of the constellation Andromeda and is visible to the unaided eye.

Exoplanet Kappa Andromedae b has a mass ~ 12.8 times greater than Jupiter's. It has a temperature of ~ 1400 Celsius and would appear bright red if seen up close by the human eye.
 
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