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SCIENCE-TELESCOPE

A   TELESCOPE    is  a  type  of   a  light  bucket.it   collects   light   from   the  objects  in    space  ,  using  either  a   lens   or  mirror.The  main  mirror   reflects the light   to  a  smaller  one,which   brings  the   light  to  a  focus    where  an  image  of  the  object is formed
The   Italian   scientist  Galileo  Galilei   made  the  first   telescope   out  of   a  couple  of  spectacle  lenses    in  1609.After   Galileo,   an  English  scientist   ,Sir    Isaac  Newton  invents  a   reflecting  telescope  that  uses    two  mirrors  instead  of  lenses   in  1668.
Now  a  days    many  types  of  telescope   are  working.Some   are  -
  • Refracting  telescope-It  uses  a  large  lens  to  refract  or  bend  the  light  to  form  an  image   of  a  distant  object.
  • Reflecting  telescope-It  uses  a  large  curved  mirror  to  pick  up  the faint  light  from  distant  stars.
  • Radio  telescope- It  captures  invisible   radio  waves   given  out  by  stars  and  other  objects  in  space.
  • Space  telescope-It   orbits  the  Earth  and  work   24  hours  a  day  .It   is  controlled  from  ground.
  • THE  HUBBLE   SPACE TELESCOPE .
The   Hubble    space   Telescope  was  launched   into   space   on  24  April  1990.it  costs  U.S 1.5 billion  dollar.It  is  13.2-m  (43.5-f  -)  long .It orbits  the  Earth every  97  minutes ,at  an  altitude  of   569  km(356)miles.travelling  at  8km/sec.
Its  main  mirror  collects  light ,which  is  directed  to  cameras   and   instruments.The  data  they  record   is  sent  to Earth  about  twice  a   day.
OBSERVATORY.- The  observatory   is  a dome  shaped   structure  ,where   telescopes  are  placed to  protect  them  .It is from  here  that  astronomers  observe  stars   at  night.
The  best  observatory   sites  are   high  altitude ,desert  region    close  to  the   equator.The  are  usually   70  km  ,from  a  town  ,far  enough  away   from  light  pollution.They  are   in  mountain  place ,so  clouds  won't  obscure  the view  .Telescopes  are placed   high  above  the  observatory  building  ,so  they  are  not  affected  by  the  Earth's heat.
Some   telescopes  work  together   to  produce a   more  detailed  image.The   very  large  Array  in   New  Mexico  ,USA,  consists  of   27  radio  dishes each   25  m(82ft)  across.
INTERESTING  FACTS.
  • The   largest  single radio  telescope   is  the  305 m (1,000ft)  dish   at  Arecibo,Puerto   Rico, built  in a  hollow  in  the island 's  hills, it  faces    different  parts   of  the  sky as  the  Earth  turns.
  • Light  travels   at  300,000 km(186000miles)per  second.so  light  from  a very  distant  object  takes  long  time to  reach  us.
  • Light  from  Sun  takes   8.3   minutes  to  reach  us.
  • Light  from  the  nearest  star  ,Proxima  Centauri   takes   4.28  years  to  reach  us .So  it  is  4.28 light  years  away   from  us.





























  • The   Andromeda  Galaxy   is  2.5  million  light years   away from  us .This  means  we  see the galaxy   as  it   was   2.5   million  years  ago. we  are  looking  back  in  time.

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