HOW DO GALAXIES LOOK LIKE

In  most of the galaxy , the stars are not uniformly  distributed , but instead  are  arranged  in  certain patterns.  The  most frequent ones are spiral galaxies .The center of such galaxies is thick  with  several old , red  shining stars. A flat  disc stretcher all around  this  centre in wich  the individual arms of  the spiral are present. It has a  thickness  of  just about 100 light years, which is  very thin as compared to the size of a galaxy. The spiral arms contain a lot of young bright blue stars. If a sprial  galaxy . other  types of galaxies are  the egg-shaped  “elliptical galaxies ” and the  irregular  galaxies , which  are  completely disordered.

OTHER  GALAXIES  NEAR MILKY WAY

There are  more  than 30 other  galaxies  near the milky way alone.the largest of them is the Andromeda galaxy. Earlier  it was known as  Andromeda galaxy  cold because only  an unclear  cloudy  pitcher  of it  could be seen.  But now with good  telescope , the  individual  stars can be observed.In 1780 , a french  astronomer, CHARLES MESSIER,prepared a catalogue with 110 such starry clusters and clouds  and   he  called  it  Andromeda M31. In 1888 , a new  catalogue was published  called new  general  catalogue , which  included 8000 objects. It is also included unusual  galaxies like  those  which  were  deformed upon  a collision or had  lost one of  their arms.

THE  DARK MATTER

The physicists  calculated the total mass  available  in the  universe by  different method. The first  method is to measure  the  movement  of the galaxies,which  arises  as result of   the force  of  attraction  between  them. Science  this , in turn , depends  on the mass of  the galaxies, the researchers can  determine the mass of  the  galaxies  from their movement. The second  method  is to  measure  the  luminosity  of the star, and from this determine  the mass of  the  objects in the  universe. Both  the  methods  give  different  result  and  the  missing  mass is  known  as  the  ‘DARK  MATTER ‘. There is  at  least five  times as  much dark matter  as  the  ‘VISIBLE’ matter and no one knows what it is.

Scientists are confronted by the embarrassing fact that they don’t know just how much energy, dark or otherwise, space contains. When quantum theorists try to calculate how much energy resides in, say, a quart of seemingly empty space, they get a big number. But astronomers calculating the same quantity from their dark energy observations get a small number. The difference between the two numbers is staggering: It’s ten to the 121st power, a one followed by 121 zeroes, an amount far exceeding the number of stars in the observable universe or grains of sand on the planet. That’s the largest disparity between theory and observation in the entire history of science. Clearly something fundamentally important about space—and therefore about everything, since galaxies, stars, planets, and people are made mostly of space—remains to be learned.

Yet just such conundrums have opened the doors of discovery before. Einstein’s general relativity theory was invented in part to solve tiny discrepancies between the predicted and the observed orbits of the planet Mercury. Quantum physics sprang in part from little puzzlement about how heat is radiated. How much may be learned, then, by resolving today’s much deeper confusions about dark matter and dark energy? As the physicist Niels Bohr used to say, “No paradox, no progress.”

Thank you

Science Geeks

PRANAV ARSHITH

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