Universe's biggest known star discovered by British astronomers
The heaviest known star – with a mass 320 times greater than the Sun's – has been discovered at the edge of our galaxy by British astronomers.
21 Jul 2010
Scientists at the University of Sheffield found the stellar giant – named R136a1 – using the European southern Observatory's Very Large Telescope in Chile and data from the Hubble Space Telescope. The star is located in the Tarantula Nebula in the Large Magellanic Cloud, a small "satellite" galaxy which orbits the Milky Way. Previously, the heaviest known stars were around 150 times the mass of the Sun, and this was believed to be close to the cosmic size limit. As stars get more massive the amount of energy created in their cores grows at a faster rate than the force of gravity which holds them together. The torrents of energy produced eventually become so powerful that the stars are torn apart.
This is known as the "Eddington Limit", after the British physicist Arthur Eddington who, in 1919, proved Einstein's theory of relativity by showing that light is bent by gravity. It was believed that the Eddington Limit was reached at around 150 solar masses. However, R136a1 has been measured at 265 solar masses. Since heavy stars rapidly lose mass as they grow older by converting it into energy, R136a1 has already lost 20 per cent of its mass in its short million-year life. It is believed originally to have been a colossal 320 solar masses. The Sun, by comparison, has been burning for 4.57 billion years, and has converted only 0.03 per cent of its mass into energy.
The chief researcher in the Sheffield team, Professor Paul Crowther, told Astronomy Now: "Because of their proximity to the Eddington Limit they lose mass at a pretty high rate." This means that they are incredibly bright and hot – R136a1 is believed to have a surface temperature of more than 40,000 degrees Celsius, and is 10 million times brighter than the Sun. Among the largest known stars previously known were the Pistol Star, between 80 and 150 solar masses, and Eta Carinae, around 100 solar masses. The Pistol Star radiates as much energy in 20 seconds as our Sun does in a year. However, both are utterly dwarfed by the vast new discovery.
According to Astronomy Now, R136a1 gives off more energy than all the stars in the Orion Nebula, and if it were in our solar system would be as much brighter than the Sun as the Sun is than the Moon. There are four stars in the cluster RCM 136a, where R136a1 sits, with a mass over 150 that of the Sun. Those four stars alone give off half the energy of the entire cluster, which contains 100,000 stars in total. Hyper-stars like R136a1 are believed to be formed from several young stars merging together, and are only found in the very heart of stellar clusters.
Prof Crowther suspects that this is about as big as stars can get. He says: "Owing to the rarity of these monsters, I think it is unlikely that this new record will be broken any time soon." The team's work can be found in the latest issue of Monthly Notices of the Royal Astronomical Society.
Astronomers identify star 10 million times brighter than the Sun
Astronomers have discovered a star that burns 10 million times bright than the Sun.
22 Jul 2010
Hyper-star R136a1, in the background, compared to our own - relatively puny - Sun. Photo: ESO
Experts identified it among a group of "monster" stars – whose size and brightness exceed what many scientists thought was possible. Found within two young star clusters, NGC 3603 and RMC 136a, the stars weigh up to 300 times the mass of the Sun, a figure which doubles the previously accepted limit of solar mass. A researcher at the University of Sheffield discovered the monster stars using the European southern Observatory's (ESO) Very Large Telescope.
The biggest star found, R136a1 within the R136a cluster, has a current mass of 265 solar masses, and it is thought its birthweight was as much as 320 times that of the Sun. It is also the most luminous star ever found, close to 10 million times that of the Sun. If R136a1 replaced the Sun at the centre of our solar system, it would outshine our star by as much as the Sun currently outshines the Moon. The team of international astronomers was led by Paul Crowther, Professor of Astrophysics from the University of Sheffield's Department of Physics and Astronomy.
Professor Crowther said: ''Unlike humans, these stars are born heavy and lose weight as they age. ''Being a little over a million-years-old, the most extreme star R136a1 is already 'middle-aged' and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses. ''Owing to the rarity of these monsters, I think it is unlikely that this new record will be broken any time soon.''
Due to the short lives of these very rare, high mass stars, it remained a challenge for astronomers to identify how they originated, he said. ''Either they were born so big or smaller stars merged together to produce them,'' he speculated. Raphael Hirschi, from Keele University, added: ''Its high mass would reduce the length of the Earth's year to three weeks, and it would bathe the Earth in incredibly intense ultraviolet radiation, rendering life on our planet impossible.''
Monster star R136a1 is whopping 265 times bigger than the Sun
July 22, 2010
A graphic from the European Southern Observatory website shows just how big R136a1 is / ESO
- R136a1 may weigh 320 solar masses
- It is 10 million times brighter than the Sun
- Star born heavy and loses weight as it ages
A HUGE ball of brightly burning gas drifting through a neighbouring galaxy may be the heaviest star ever discovered - 265 times bigger than the Sun.
Those behind the find say the star, called R136a1, may once have weighed as much as 320 solar masses. Astrophysicist Paul Crowther said the obese star - twice as heavy as any previously discovered - has already slimmed down considerably over its lifetime. In fact it's burning itself off with such intensity that it shines with nearly 10 million times the luminosity of the Sun. "Unlike humans, these stars are born heavy and lose weight as they age," said Dr Crowther, an astrophysicist at the University of Sheffield in northern England.
"R136a1 is already middle-aged and has undergone an intense weight loss program." Dr Crowther said the giant was identified at the centre of a star cluster in the Tarantula Nebula, a sprawling cloud of gas and dust drifting through one of the Milky Way's neighbouring galaxies. The star was the most massive of several giants identified by Dr Crowther and his team in an article in the Monthly Notices of the Royal Astronomical Society. While other stars can be larger, notably the swollen crimson-coloured ones known as red giants, they weigh far less.
Still, the mass of R136a1 and its ilk means they're tens of times bigger than our sun, and that they're brighter and hotter, too. Surface temperatures can surpass 40,000C, seven times hotter than the Sun. They're also several million times brighter, a product of the fact that the greedy giants tear through their energy reserves far faster than their smaller counterparts. That also means that massive stars live fast and die young, quickly shedding huge amounts of material and burning themselves out in what are thought to be spectacular explosions.
"The biggest live only three million years," Dr Crowther said. "In astronomy that's a very short time." Small lifespans are one of several reasons why these obese stars are so hard to find. Another is that they're extremely rare, forming only in the densest star clusters. Astronomers also have a limited range in which to look: In clusters that are too far away it isn't always possible to tell if a telescope has picked up on one heavyweight star or two smaller ones in close proximity.
In this case, Dr Crowther's team re-examined previously known stars to see if they could find an accurate measurement of their weight. The team reviewed archival data from the Hubble Space Telescope and gathered new readings from the European Southern Observatory's Very Large Telescope at Paranal in Chile. Scientists who weren't involved in the find said the results were impressive, although they cautioned it was still possible, although unlikely, that scientists had confused two very close stars for a bigger, single one.
"What they're characterising as a single massive star could in fact be a binary system too close to be resolved," said Mark Krumholz, an astronomer at the University of California, Santa Cruz. Both he and Phillip Massey, an astronomer with the Lowell Observatory in Arizona, also cautioned that the star's weight had been inferred using scientific models and that those were subject to change.
But both scientists said the authors had made a strong case, arguing for instance that the solar material being thrown off from feuding stars in a binary system would produce much more powerful X-rays than have been detected. Dr Crowther acknowledged that R136a1 could have a partner, but he said it was likely to be a much smaller star, meaning that its birth weight was still considerable - perhaps 300 solar masses instead of 320.
Images of the star can be seen at the website of the European Southern Observatory.
http://www.guardian.co.uk/science/interactive/2010/jul/21/monster-star-r136a1-sun-planets
'Monster star': R136a1 compared with our solar system
See how the newly discovered R136a1 star would dwarf our own sun and planets
• Read more: Biggest star ever found in neighbouring galaxy
• Name that star: can you think of a catchier moniker than R136a1?
http://www.physorg.com/news198924098.html
300 solar masses: Scientists find most massive star ever discovered
July 21, 2010
This montage shows a visible-light image of the Tarantula nebula as seen with the Wide Field Imager on the MPG/ESO 2.2-metre telescope (left) along with a zoomed-in visible-light image from the Very Large Telescope (middle). A new image of the R136 cluster, obtained with the near-infrared MAD adaptive optics instrument on the Very Large Telescope is shown in the right-hand panel, with the cluster itself at the lower right. The MAD image provides unique details on the stellar content of the cluster. Credit: ESO/P. Crowther/C.J. Evans
(PhysOrg.com) -- Using a combination of instruments on ESO's Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the sun, or twice as much as the currently accepted limit of 150 solar masses. The existence of these monsters -- millions of times more luminous than the sun, losing weight through very powerful winds -- may provide an answer to the question, "how massive can stars be?"
A team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, has used ESO's Very Large Telescope (VLT), as well as archival data from the NASA/ESA Hubble Space Telescope, to study two young clusters of stars, NGC 3603 and RMC 136a in detail. NGC 3603 is a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust, located 22 000 light-years away from the Sun. RMC 136a (more often known as R136) is another cluster of young, massive and hot stars, which is located inside the Tarantula Nebula, in one of our neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away.
The team found several stars with surface temperatures over 40,000 degrees, more than seven times hotter than our Sun, and a few tens of times larger and several million times brighter. Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses. The star R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and with a birthweight of as much as 320 times that of the Sun.
In NGC 3603, the astronomers could also directly measure the masses of two stars that belong to a double star system, as a validation of the models used. The stars A1, B and C in this cluster have estimated masses at birth above or close to 150 solar masses. Very massive stars produce very powerful outflows. "Unlike humans, these stars are born heavy and lose weight as they age," says Paul Crowther. "Being a little over a million years old, the most extreme star R136a1 is already 'middle-aged' and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses."
R136 is a cluster of young, massive and hot stars located inside the Tarantula Nebula, in one of the Milky Way's neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away. This video zooms in on the R136 cluster as seen with the MAD adaptive optics instrument on the Very Large Telescope, starting from a wider view obtained with the Wide Field Imager on the MPG/ESO 2.2-metre telescope. Credit: ESO/P. Crowther/C.J. Evans
If R136a1 replaced the Sun in our Solar System, it would outshine the Sun by as much as the Sun currently outshines the full Moon. "Its high mass would reduce the length of the Earth's year to three weeks, and it would bathe the Earth in incredibly intense ultraviolet radiation, rendering life on our planet impossible," says Raphael Hirschi from Keele University, who belongs to the team. These super heavyweight stars are extremely rare, forming solely within the densest star clusters. Distinguishing the individual stars — which has now been achieved for the first time — requires the exquisite resolving power of the VLT's infrared instruments.
The team also estimated the maximum possible mass for the stars within these clusters and the relative number of the most massive ones. "The smallest stars are limited to more than about eighty times more than Jupiter, below which they are 'failed stars' or brown dwarfs," says team member Olivier Schnurr from the Astrophysikalisches Institut Potsdam. "Our new finding supports the previous view that there is also an upper limit to how big stars can get, although it raises the limit by a factor of two, to about 300 solar masses."
Within R136, only four stars weighed more than 150 solar masses at birth, yet they account for nearly half of the wind and radiation power of the entire cluster, comprising approximately 100 000 stars in total. R136a1 alone energises its surroundings by more than a factor of fifty compared to the Orion Nebula cluster, the closest region of massive star formation to Earth.
This artist's impression shows the relative sizes of young stars, from the smallest "red dwarfs", weighing in at about 0.1 solar masses, through low mass "yellow dwarfs" such as the Sun, to massive "blue dwarf" stars weighing eight times more than the Sun, as well as the 300 solar mass star named R136a1. Credit: ESO/M. Kornmesser.
Understanding how high mass stars form is puzzling enough, due to their very short lives and powerful winds, so that the identification of such extreme cases as R136a1 raises the challenge to theorists still further. "Either they were born so big or smaller stars merged together to produce them," explains Crowther.
Stars between about 8 and 150 solar masses explode at the end of their short lives as supernovae, leaving behind exotic remnants, either neutron stars or black holes. Having now established the existence of stars weighing between 150 and 300 solar masses, the astronomers' findings raise the prospect of the existence of exceptionally bright, "pair instability supernovae" that completely blow themselves apart, failing to leave behind any remnant and dispersing up to ten solar masses of iron into their surroundings. A few candidates for such explosions have already been proposed in recent years.
Not only is R136a1 the most massive star ever found, but it also has the highest luminosity too, close to 10 million times greater than the Sun. "Owing to the rarity of these monsters, I think it is unlikely that this new record will be broken any time soon," concludes Crowther.
More information: This work is presented in an article published in the Monthly Notices of the Royal Astronomical Society ("The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit", by P. Crowther et al.).
http://www.eso.org/public/archives/releases/sciencepapers/eso1030/eso1030.pdf
http://www.guardian.co.uk/science/2010/jul/22/most-massive-star-r136a1
What a scorcher – hotter, heavier and millions of times brighter than the sun
Colossal stars discovered by British astronomers give an insight into the early universe
22 July 2010
Source: ESO Link to this video
R136a1 was found among a clutch of monster stars in the Tarantula Nebula. They are the most colossal stars ever seen and live short, bright, lives in faraway reaches of space before exploding in a blaze of glory. One of the stars, now tagged R136a1, is estimated to weigh 265 times more than the sun and to shine millions of times more brightly. Were it to replace our own star, the intensity of its rays would sterilise the Earth leaving it lifeless. British astronomers spotted the stars, more massive than any others on record, using the Very Large Telescope, an aptly named observatory on a mountain top in the Atacama desert of northern Chile.
The discovery of the stellar giants has prompted astronomers to scrap the upper limits they set on star formation which suggested it was almost impossible for a star to grow to more than 150 times the mass of the sun. The team, led by Paul Crowther, an astrophysicist at Sheffield University, searched two regions of space for massive stars. The first region, known as NGC 3603, is a stellar nursery 22,000 light-years away in a region of the Milky Way called the Carina spiral arm.
The second target, RMC 136a, is a cloud of gas and dust, 165,000 light-years away in the Tarantula nebula of our neighbouring galaxy, the Large Magellanic Cloud. The astronomers were able to distinguish individual stars using exquisitely sensitive infra-red instruments on the telescope, and take measurements of their brightness and mass. At least three stars examined in the first region of space weighed in at about 150 times the mass of the sun. The record-breaking star, R136a1, was found in the second region. When born, the star could have been a staggering 320 times more massive than the sun.
Several of the stars were found to have surface temperatures above 40,000C, which is more than seven times hotter than the sun. "These stars are born heavy and lose weight as they age," said Crowther. "Being a little over a million years old, the most extreme star R136a1 is already middle-aged and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time. Owing to the rarity of these monsters I think it unlikely this new record will be broken any time soon."
If R136a1 were in our own solar system it would outshine the sun as much as the sun outshines the full moon, the scientists said. The mass of the star is so great that it would reduce the length of an Earth year - the time it takes to circle the star - to just three weeks. "It would [also] bathe Earth in incredibly intense ultraviolet radiation, rendering life on our planet impossible," said Raphael Hirschi, a member of the team at Keele University.
While the latest crop of stars are the most massive and heaviest ever spotted, they are not the largest. The biggest star in the group, R136a1, is roughly 30 times as wide as the sun. Another kind of star, known as a super red giant, can grow to many hundreds of times that size - though is considerably lighter, at only 10 times the mass of the sun. It is unlikely that any "alien" planets circle the massive stars that Crowther's team has studied. Radiation from the stars would obliterate any nearby cosmic material that could become compact enough to be a planet. Even if some remained, planets would take longer to form than the entire lifespan of a massive star.
Crowther said: "We don't really know what happens when these massive stars reach the end of their lives. When some big stars die, their cores implode and they become neutron stars or black holes, but these might be different. They might blow up in a spectacular supernova and leave no remnants behind at all." The explosions could fling the weight of 10 suns worth of iron into space. The team's observations reveal what the early universe might have looked like, when many of the first stars to be born might have been cosmic monsters like R136a1.
Before the latest discovery, the most massive star known was the peony nebula star, which, at about 175 times the mass of the sun, could still hold the record for our own galaxy. Details of the discovery are reported in the monthly notices of the Royal Astronomical Society.
http://www.eso.org/public/news/eso1030/
Stars Just Got Bigger
A 300 Solar Mass Star Uncovered
21 July 2010
Using a combination of instruments on ESO's Very Large Telescope, astronomers have discovered the most massive stars to date, one weighing at birth more than 300 times the mass of the Sun, or twice as much as the currently accepted limit of 150 solar masses. The existence of these monsters — millions of times more luminous than the Sun, losing weight through very powerful winds — may provide an answer to the question "how massive can stars be?"
A team of astronomers led by Paul Crowther, Professor of Astrophysics at the University of Sheffield, has used ESO's Very Large Telescope (VLT), as well as archival data from the NASA/ESA Hubble Space Telescope, to study two young clusters of stars, NGC 3603 and RMC 136a in detail. NGC 3603 is a cosmic factory where stars form frantically from the nebula's extended clouds of gas and dust, located 22 000 light-years away from the Sun (eso1005). RMC 136a (more often known as R136) is another cluster of young, massive and hot stars, which is located inside the Tarantula Nebula, in one of our neighbouring galaxies, the Large Magellanic Cloud, 165 000 light-years away (eso0613).
The team found several stars with surface temperatures over 40 000 degrees, more than seven times hotter than our Sun, and a few tens of times larger and several million times brighter. Comparisons with models imply that several of these stars were born with masses in excess of 150 solar masses. The star R136a1, found in the R136 cluster, is the most massive star ever found, with a current mass of about 265 solar masses and with a birthweight of as much as 320 times that of the Sun.
In NGC 3603, the astronomers could also directly measure the masses of two stars that belong to a double star system [1], as a validation of the models used. The stars A1, B and C in this cluster have estimated masses at birth above or close to 150 solar masses.
Very massive stars produce very powerful outflows. "Unlike humans, these stars are born heavy and lose weight as they age," says Paul Crowther. "Being a little over a million years old, the most extreme star R136a1 is already 'middle-aged' and has undergone an intense weight loss programme, shedding a fifth of its initial mass over that time, or more than fifty solar masses."
If R136a1 replaced the Sun in our Solar System, it would outshine the Sun by as much as the Sun currently outshines the full Moon. "Its high mass would reduce the length of the Earth's year to three weeks, and it would bathe the Earth in incredibly intense ultraviolet radiation, rendering life on our planet impossible," says Raphael Hirschi from Keele University, who belongs to the team.
These super heavyweight stars are extremely rare, forming solely within the densest star clusters. Distinguishing the individual stars — which has now been achieved for the first time — requires the exquisite resolving power of the VLT's infrared instruments [2].
The team also estimated the maximum possible mass for the stars within these clusters and the relative number of the most massive ones. "The smallest stars are limited to more than about eighty times more than Jupiter, below which they are 'failed stars' or brown dwarfs," says team member Olivier Schnurr from the Astrophysikalisches Institut Potsdam. "Our new finding supports the previous view that there is also an upper limit to how big stars can get, although it raises the limit by a factor of two, to about 300 solar masses."
Within R136, only four stars weighed more than 150 solar masses at birth, yet they account for nearly half of the wind and radiation power of the entire cluster, comprising approximately 100 000 stars in total. R136a1 alone energises its surroundings by more than a factor of fifty compared to the Orion Nebula cluster, the closest region of massive star formation to Earth.
Understanding how high mass stars form is puzzling enough, due to their very short lives and powerful winds, so that the identification of such extreme cases as R136a1 raises the challenge to theorists still further. "Either they were born so big or smaller stars merged together to produce them," explains Crowther.
Stars between about 8 and 150 solar masses explode at the end of their short lives as supernovae, leaving behind exotic remnants, either neutron stars or black holes. Having now established the existence of stars weighing between 150 and 300 solar masses, the astronomers' findings raise the prospect of the existence of exceptionally bright, "pair instability supernovae" that completely blow themselves apart, failing to leave behind any remnant and dispersing up to ten solar masses of iron into their surroundings. A few candidates for such explosions have already been proposed in recent years.
Not only is R136a1 the most massive star ever found, but it also has the highest luminosity too, close to 10 million times greater than the Sun. "Owing to the rarity of these monsters, I think it is unlikely that this new record will be broken any time soon," concludes Crowther.
Notes
[1] The star A1 in NGC 3603 is a double star, with an orbital period of 3.77 days. The two stars in the system have, respectively, 120 and 92 times the mass of the Sun, which means that they have formed as stars weighing, respectively, 148 and 106 solar masses.
[2] The team used the SINFONI, ISAAC and MAD instruments, all attached to ESO's Very Large Telescope at Paranal, Chile.
More information
This work is presented in an article published in the Monthly Notices of the Royal Astronomical Society ("The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 Msun stellar mass limit", by P. Crowther et al.).
The team is composed of Paul A. Crowther, Richard J. Parker, and Simon P. Goodwin (University of Sheffield, UK), Olivier Schnurr (University of Sheffield and Astrophysikalisches Institut Potsdam, Germany), Raphael Hirschi (Keele University, UK), and Norhasliza Yusof and Hasan Abu Kassim (University of Malaya, Malaysia).
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries.
ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".
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