[getsmart-l] The importance of the David Dunlap Observatory & the discovery of a black hole

[Gloria Boxen]

On Friday Dec 14, 8:00 p.m.The Royal Astronomical Society of Canada, Mississauga Centre, presents Ian Shelton, the discoverer of the largest supernova  visible to the naked eye in over 200  years.  He will talk  about the Dunlap  Observaatory.  Go to bottom of message for details.   The location is  U of T at Mississauga.

http://astro-canada.ca/_en/a2214.html

Charles Thomas Bolton (1943- )    He was the first to discover a black hole             Charles Thomas Bolton....
>From 1970 to 1972, he was a postdoctoral researcher at the David Dunlap Observatory of the University of Toronto astronomy department. He also taught at the David Dunlap Observatory from 1970 to 1972, ... He became a professor in the astronomy department at the University of Toronto in 1973, and has remained there ever since.


    In 1970, Bolton was the first to develop a computer model for stellar atmospheres that was able to generate large regions of the modeled spectrum with enough precision to allow comparison with the spectra from real stars.


    In 1972, Bolton made a discovery in astronomy that was so important it guaranteed him a place in the history books: he was the first astronomer to present irrefutable evidence of the existence of a black hole. The black hole in question was Cygnus X-1, which lies at the centre of our own galaxy, the Milky Way. Bolton detected its presence by observing star HDE 226868 wobble as if it was orbiting around an invisible but massive companion. His calculations demonstrated that the companion could be nothing less than a black hole.

http://www.magazine.utoronto.ca/02autumn/blackhole.asp
    The history of the discovery of the first black hole   

       Bolton didn’t set out to find a black hole in the summer of                       1971.Then          a 28-year-old post-doctoral fellow and part-time faculty       member at the          University of Toronto, he simply had access to    plenty  of telescope time          at the university’s David Dunlap Observatory in  Richmond Hill, Ont., and          spent several nights a week peering at the  heavens through the 1.88-metre          telescope inside the domed observatory. His first love was binary star          systems (two stars that orbit each other, similar to the earth-moon orbit).

            That summer, he grew interested in a possible binary system involving  a giant blue star called HDE226868 and something else that was emitting          powerful X-ray signals. He thought this invisible X-ray source, dubbed          Cygnus X-1 (because it was in the constellation of Cygnus, the Swan),          was likely a neutron star. 

 
           In September, he started observing HDE226868. Heading to the  observatory          that night, Bolton met a grad student who remarked that this binary system          might contain a black hole. “No way,” Bolton told him. But the next day,          looking at photographic plates of the star’s spectrum, he saw some puzzling          emission lines – bright marks in unusual places. “That tweaked my          interest,” he says. He decided to continue observing HDE226868.

 
            By November, Bolton had enough data to estimate that HDE226868 was moving          around its invisible partner at more than 70 kilometres per second –          far, far faster than anticipated. Such tremendous speed meant that whatever          body was emitting the X-rays was far too dense, and its gravitational          pull was much too strong, to be a neutron star.

 
           The only feasible option was a black hole. “At this point my excitement          reached a fever pitch, and I could hardly eat or sleep,” Bolton recalls.          A stream of gas seemed to be flowing from the star to Cygnus X-1, swirling          around it at incredible speeds before vanishing. As a result, the gas          became super-heated and produced the X-rays that had drawn astronomers’          attention.

 
            They were heady findings, and Bolton admits he was naive not to consider          that others might be racing to publish the same results. Sure enough,          in December a colleague handed him a preprint of a paper by two English          astronomers about Cygnus X-1 and HDE226868. But their observations were          cautiously worded, and Bolton believed he had better data. He decided          to submit his own results for publication. “If I was wrong, it could be          my career,” he says. “On the other hand, if I was right, it could be my          career!”

 
             In December, an American colleague supplied some last-minute findings          that erased any remaining doubts in Bolton’s mind. He wrote his paper;          it appeared in Nature in February 1972, shortly after the English astronomers          published their data. But Bolton had staked his claim: the high energies          of the X-rays and the large mass of the star’s unseen companion raised          “the distinct possibility that [Cygnus X-1] is a black hole.”

 
             “Theorists have been postulating black holes, but this could be observational          evidence for one,” commented University of Toronto astronomer Helen Hogg          in her popular Toronto Star astronomy column. 



     A black hole is a celestial body that is so massive and dense that nothing can escape its gravitational pull (its attractive force), not even light. The name arises from the fact that it cannot emit light and thus appears black, and it traps all that falls into it, like a hole in space. 
    In 1978, Bolton demonstrated that the nitrogen anomalies observed in the spectra of OBN stars are due to the transfer of material to a nearby neighbouring star. OB stars are very hot blue stars with thick atmospheres. OBN stars are a subclass of OB stars that are characterized by nitrogen anomalies in their spectra.


     In 1981, he suggested that the ejections of material from Be-type stars – a subclass of B stars – are caused by non-radial pulsations (vibrations that shake Be stars in an irregular manner). B stars have similar properties to O stars (that is, they are very hot blue stars with thick atmospheres) but have lower surface temperatures. O and B stars frequently occur together in loose groupings, and are often collectively referred to as OB stars.


    In 1985, Bolton and his colleague Douglas R. Gies demonstrated that not all “ejected” OB stars (runaway stars that travel at very high speeds through open space) are the result of the supernova explosion of a companion star. Instead, many are produced by gravitational interactions that occur within OB star clusters.

 
    Bolton established a Canadian first in the 1990’s when he wrote a bylaw to regulate light pollution that was adopted by the town of Richmond Hill, Ontario, in 1994.


    Bolton has received many awards for his work, including being elected as a member of the Royal Society of Canada.
    


What will happen to Tom Bolton's research if the DDO is closed?  He depends on continuous observations, not available at the remote observatories where a few weeks of observation time is available?
http://www.astro.utoronto.ca/staff.html#Bn

http://www.cascaeducation.ca/files/canadianContributions.html
Canadian Contributions to Astronomy

Ian Shelton (University of Toronto) discovered the            brightest supernova in 400 years, on February 23, 1987.


http://www.theglobeandmail.com/servlet/ArticleNews/freeheadlines/LAC/20071016/DUNLAP16/national/National
The U of Toronto has used lies to justify the closing of the Observatory.
 Finally, this article, which repeats one of them, light pollution has made the observatory useless, explains the limit of the usefulness of the Observatory (deep space cannot be studied).

http://www.mississaugaastronomicalsociety.ca/meetings.htm

Royal     Astronomical Society of Canada        
Mississauga Centre
                Friday   December 14, 2007            Speaker:         Professor Ian Shelton, Department of Astronomy, University of Toronto
     
    Topic:       Uncertain   Future
     
      The David Dunlap Observatory houses the largest   optical telescope east of the Mississippi River.
       Join Ian Shelton as he takes us on a tour of the   DDO       and its role in astronomy and explore the   uncertain future
       of these inspiring buildings.
     
    Dr. Ian Shelton was raised in Winnipeg, Canada. In 1987, while he was working at an observatory in Las Companas, Chile, he developed a photograph of the Tarantula Nebula and saw something unusual in the picture. He and several others went outside to check, and they saw a shining light in the Large Magellanic Cloud (the galaxy that encompasses the Tarantula Nebula) that wasn't there before. It was a supernova-a giant star that blew itself apart at the end of its life. 
  
 Dr Shelton's discovery was the first supernova visible to the naked eye in almost 200 years. It was called "SuperNova 1987A Shelton," and for the several months that it lasted, it was among the most studied phenomena in the night sky. 

The location for our meetings is the University of Toronto at Mississauga.  Meetings will be held in the room SE2082 located in the South Building.  Parking is $5 - tickets are available from machines which accept credit cards or cash.  Meeting start time: 8:00 pm


                 Map to the meeting location:  http://www.utm.utoronto.ca/108.0.html
     
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