Take up maths and physics subjects.
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Astonomer is a scientist who studies the space, Earth, Moon, Planets, Sun, Stars, Nebula, Comets, Back holes, White dwarfs, Cosmic radiation, our galaxy etc.
Astonomer usually learns the scientific principles of the evolution of the universe, the laws of nature, physical laws governing various physical bodies. Astronomer also studies different aspects of space science, rockets, flights, satellites, meteors etc.
Astronomers build and deal with many instruments for observations of the above celestial bodies. They are usually highly educated in mathematics, physics and chemistry, astrophysics and astronomy subjects. They work in research institutes and Universities. They teach, do consulting work and attend conferences round the globe.
Most of their work is in physics. So after the 10th take up maths, physics subjects. After 12th class, you have degrees like Bachelor of science, with physics main, B.S. in astronomy, B.S. in Physics etc. You may also do M.Sc. and Ph. D. either in Indian universities or abroad in the subject of astronomy or astrophysics. There are scholarships offered by universities abroad. You have to pass certain qualifying exams like GRE, TOEFL etc. Even if you do engineering in bachelors, you may be eligible for post graduation in astrophysics. Osmania university at Hyderabad in south of India offers this course at post graduation level.
There are some amateur astronomer clubs who do observations in space and do star gazing activities. During eclipses, they are active in public. You can also find them related to planetariums or observatories. You can establish contact with them to be at an advantage.