Astronomers witness birth of Milky Way's most massive star

a) Mid-infrared Spitzer composite image. 

b) Herschel column density image of SDC335. 

c) ALMA 3.2 mm dust continuum emission of the central region of SDC335 where two cores are identified, MM1 and MM2. 

Credit: A&A 555, A112 (2013)

Scientists have observed in unprecedented detail the birth of a massive star within a dark cloud core about 10,000 light years from Earth.

The team used the new ALMA (Atacama Large Millimetre/submillimetre Array) telescope in Chile – the most powerful radio telescope in the world – to view the stellar womb which, at 500 times the mass of the Sun and many times more luminous, is the largest ever seen in our galaxy.

The researchers say their observations – to be published in the journal Astronomy and Astrophysics – reveal how matter is being dragged into the centre of the huge gaseous cloud by the gravitational pull of the forming star – or stars – along a number of dense threads or filaments.

"The remarkable observations from ALMA allowed us to get the first really in-depth look at what was going on within this cloud," said lead author Dr Nicolas Peretto, from Cardiff University.

"We wanted to see how monster stars form and grow, and we certainly achieved our aim. One of the sources we have found is an absolute giant—the largest protostellar core ever spotted in the Milky Way!

"Even though we already believed that the region was a good candidate for being a massive star-forming cloud, we were not expecting to find such a massive embryonic star at its centre. This cloud is expected to form at least one star 100 times more massive than the Sun and up to a million times brighter. Only about one in 10,000 of all the stars in the Milky Way reach that kind of mass."

Different theories exist as to how these massive stars form but the team's findings lend weight to the idea that the entire cloud core begins to collapse inwards, with material raining in towards the centre to form one or more massive stars.

Co-author Professor Gary Fuller, from The University of Manchester, said: "Not only are these stars rare, but their births are extremely rapid and childhood short, so finding such a massive object so early in its evolution in our Galaxy is a spectacular result.

More information: 'Global collapse of molecular clouds as a formation mechanism for the most massive stars,' Astronomy & Astrophysics, www.aanda.org/articles/aa/pdf/2013/07/aa21318-13.pdf

ESA ESO VLT: Newborn Massive Stars Dwarf Full-Grown Stellar Giants

Artist’s impression illustrating the formation process of massive stars. 

At the end of the formation process, the surrounding accretion disk disappears, revealing the surface of the young star. 

At this phase the young massive star is much larger than when it has reached a stable equilibrium.

CREDIT: Lucas Ellerbroek/Lex Kaper University of Amsterdam

Massive stars generally start out life much bigger than they will be in maturity, a new study seems to confirm.

Astronomers from the University of Amsterdam got a rare look at a massive star in the process of forming and found that the star will contract until it has reached a stable equilibrium.

The researchers studied the young star B275, which lies in the Omega Nebula, also called the Swan Nebula or Messier 17. This hotbed of gas, dust and young stars lies approximately 5,500 light-years from Earth, in the direction of the Sagittarius constellation.

Astronomers typically struggle to obtain clear observations of a massive star as it is forming, since newborn stars are deeply embedded and obscured in their parent clouds of gas and dust.

Peering through the haze
To lift the veil on the process of star formation, the researchers sifted through ultraviolet and infrared data collected from a powerful spectrograph instrument, called the X-shooter, on the European Space Agency's Very Large Telescope at the Paranal Observatory in Chile.

"The large-wavelength coverage of X-shooter provides the opportunity to determine many stellar properties at once, like the surface temperature, size, and the presence of a disk," study lead author Bram Ochsendorf said in a statement.

Ochsendorf analyzed the data as part of his master's research project at the University of Amsterdam.

The results indicate that B275 is about three times larger than stars that are about seven times more massive than our sun and have reached the so-called main sequence phase of their lives.

The main sequence phase represents a specific stage of stellar evolution in which a star burns hydrogen into helium. (Our own sun is currently in its main sequence.)

The team's findings appear to confirm a theory of star formation predicting that a newly formed massive star will contract until it reaches a more stable state.

NASA Chandra: A Pulsar and Its Mysterious Tail

A spinning neutron star is tied to a mysterious tail -- or so it seems. Astronomers using NASA's Chandra X-ray Observatory have found that this pulsar, known as PSR J0357+3205 (or PSR J0357 for short), apparently has a long, X-ray bright tail streaming away from it.

This composite image shows Chandra data in blue and Digitized Sky Survey data in yellow.

The position of the pulsar at the upper right end of the tail is seen by mousing over the image.

The two bright sources lying near the lower left end of the tail are both thought to be unrelated background objects located outside our galaxy.

PSR J0357 was originally discovered by the Fermi Gamma Ray Space Telescope in 2009. Astronomers calculate that the pulsar lies about 1,600 light years from Earth and is about half a million years old, which makes it roughly middle-aged for this type of object.

If the tail is at the same distance as the pulsar then it stretches for 4.2 light years in length. This would make it one of the the longest X-ray tails ever associated with a so-called "rotation-powered" pulsar, a class of pulsar that get its power from the energy lost as the rotation of the pulsar slows down. (Other types of pulsars include those driven by strong magnetic fields and still others that are powered by material falling onto the neutron star.)

The Chandra data indicate that the X-ray tail may be produced by emission from energetic particles in a pulsar wind, with the particles produced by the pulsar spiraling around magnetic field lines.

Other X-ray tails around pulsars have been interpreted as bow-shocks generated by the supersonic motion of pulsars through space, with the wind trailing behind as its particles are swept back by the pulsar's interaction with the interstellar gas it encounters.

However, this bow-shock interpretation may or may not be correct for PSR J0357, with several issues that need to be explained. For example, the Fermi data show that PSR J0357 is losing a very small amount of energy as its spin slows down with time. This energy loss is important, because it is converted into radiation and powering a particle wind from the pulsar. This places limits on the amount of energy that particles in the wind can attain, and so might not account for the quantity of X-rays seen by Chandra in the tail.

NASA - A Green Ring Fit for a Superhero

This glowing emerald nebula seen by NASA's Spitzer Space Telescope is reminiscent of the glowing ring wielded by the superhero Green Lantern.

In the comic books, the diminutive Guardians of the Planet "Oa" forged his power ring, but astronomers believe rings like this are actually sculpted by the powerful light of giant "O" stars, the most massive type of star known to exist.

Named RCW 120, this region of hot gas and glowing dust can be found in the murky clouds encircled by the tail of the constellation Scorpius.

The ring of dust actually is glowing in infrared colours that our eyes cannot see, but show up brightly when viewed by Spitzer's infrared detectors.

At the centre of this ring are a couple of giant stars whose intense ultraviolet light has carved out the bubble, though they blend in with other stars when viewed in infrared.

This bubble is far from unique. Just as the Guardians of Oa have selected many beings to serve as Green Lanterns and patrol different sectors of space, Spitzer has found that such bubbles are common and an can be found around O stars throughout our Milky Way galaxy.

The small objects at the lower right area of the image may themselves be similar regions seen at much greater distances across the galaxy.

Rings like this are so common in Spitzer's observations that astronomers have even enlisted the help of the public to help them find and catalogue them all.

Anyone interested in joining the search as a citizen scientist can visit "The Milky Way Project," part of the "Zooniverse" of public astronomy projects, at http://www.milkywayproject.org/.

Image Credit: NASA/JPL-Caltech

NASA WISE: Jumbo Jellyfish Or Massive Star

Jumbo Jellyfish Or Massive Star

Some might see a blood-red jellyfish in a forest of seaweed, while others might see a big, red eye or a pair of lips.

In fact, the red-colored object in this new infrared image from NASA's Wide-field Infrared Survey Explorer (WISE) is a sphere of stellar innards, blown out from a humongous star.

The star (white dot in center of red ring) is one of the most massive stellar residents of our Milky Way galaxy. Objects like this are called Wolf-Rayet stars, after the astronomers who found the first few, and they make our sun look puny by comparison.

Called V385 Carinae, this star is 35 times as massive as our sun, with a diameter nearly 18 times as large. It's hotter, too, and shines with more than one million times the amount of light.

Fiery candles like this burn out quickly, leading short lives of only a few million years. As they age, they blow out more and more of the heavier atoms cooking inside them - atoms such as oxygen that are needed for life as we know it.

The material is puffed out into clouds like the one that glows brightly in this WISE image. In this case, the hollow sphere showed up prominently only at the longest of four infrared wavelengths detected by WISE.

Astronomers speculate this infrared light comes from oxygen atoms, which have been stripped of some of their electrons by ultraviolet radiation from the star.

When the electrons join up again with the oxygen atoms, light is produced that WISE can detect with its 22-micron infrared light detector. The process is similar to what happens in fluorescent light bulbs.

Infrared light detected by WISE at 12 microns is colored green, while 3.4- and 4.6-micron light is blue. The green, kelp-looking material is warm dust, and the blue dots are stars in our Milky Way galaxy.

This image mosaic is made up of about 300 overlapping frames, taken as WISE continues its survey of the entire sky - an expansive search, sure to turn up more fascinating creatures swimming in our cosmic ocean.

V385 Carinae is located in the Carina constellation, about 16,000 light-years from Earth.

JPL manages the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA.