Whether you are taking an advanced course in stellar astrophysics or an introductory course in astronomy, you learn that one of the fundamental tenets of stellar evolution is that main sequence stars with masses above 25 solar masses will become a black hole. However, new results from ESO's Very Large Telescope indicate that this is not necessarily the case.
The nearest super star cluster to Earth, Westerlund 1, located roughly 16,000 light-years away, contains some of the most massive main-sequence stars in the Universe. Some of these giants have radii that would reach to Saturn's orbit, while others are as luminous as a million Suns.
Needless to say, the stars in this cluster are quite extraordinary. With all of them having masses in excess of 30 - 40 times the mass of the Sun, it also makes the cluster quite young. (More massive stars age more quickly.) But this also implies that stars that have already left the main sequence contained at least 35 solar masses. This in of itself is not a startling discovery, however the ensuing detection of a magnetar in the midst of Westerlund 1 sent tremors through the world of astronomy.
A magnetar is a highly magnetized neutron star, and there are few of them known to exist in the Milky Way. Conventionally, neutron stars form when a 10 - 25 solar mass star leaves the main sequence and dies in a massive supernova. However, with all the stars in Weserlund 1 having formed at nearly the same time (and considering mass is the key factor in the aging rate) the magnetar must have had an initial mass in excess of 40 solar masses.
What scientists must now answer is why the star didn't collapse into a black hole? One theory is that a companion star interacted with the evolving star and caused it to expend much of its energy prematurely. The result is that much of the mass escaped through this exchange of energy, leaving too little mass behind to fully evolve into a black hole. However, there is no companion detected. Of course the companion star could have been destroyed during the energetic interactions with the magnetar's progenitor. But this itself isn't clear.
Ultimately, we are faced with a question that we can not readily answer. Should we question our understanding of black hole formation? Or is there another solution to the problem that, as yet, goes unseen. The solution lies in collecting more data. If we can find another occurrence of this phenomenon, then perhaps we can shed some light on the true nature of stellar evolution.
Comments
I really hope they image this as they have the Crab Nebula’s inner dynamo.
btw, it’s tenet.
John was right, it is plural – Tenets
“you learn that one of the fundamental tenets of stellar evolution is….”
to be correctly with no plural, he would have to have written
“you learn that the fundamental tenet of stellar evolution is….”
Good post John, sure points up the need for a swath of mega telescopic Satellites in GEO; if the House doesn’t scuttle the Senate Bill for NASA, then the work NASA is doing as we speak, in preparation, should give us the HLV we need to put them in Orbit by the end of the Decade
one other note: I am more into History than Science, having traced our family back to the 16/7th century, and I compare those centuries to the 19th/20th centuries, in that a lot of the changes that came about in the 18th century was spring loaded in the 150 to 200 years before; the 21st century is going to see a Science/Social Revolution on par with the Industrial Revolution of the 18/19th centuries; we are only nibbling around the edge of that enormous mountain of knowledge; if your under 45 hold onto your seats your in for a ride to rival any super fairground roller coaster
sir, I am an amateur astronomer in India, i have been saying that there is no black hole at the centre of galaxies,in spite there is a vacum like a whirlpool.I may be wrong.but we should think
Hmmm… thinking about black holes why isnt there an Anti-black hole?We got anti-matter right & black hole sucks in all matter!So if anti matter really exists there must be an anti-black hole i dont know but this is my humble opinion.
Good point, though sometimes it’s hard to arrive to definite conclusions
friends i have a doubt…..
We all know that gravitation is directly proportional to mass….black hole is a remaining mass of large star….during there life cycle there stars loosing their mass by fusion reaction and there energy oppose the own gravitational pull…. k i’m clear about this but after loosing huge mass how these stars get’s infinite gravity by converting into black holes……if u anyone know that send the ans to my mail
Vinod130389@yahoo.co.in