Astronomer

70 kg. Mass is a measure of the particles that makes up an object and the composition of the object does not change on the moon. However, the object's weight will change on the moon, just as it appears to change in an elevator.
The acceleration due to gravity on the earth is approximately 9.8 m/s^2, depending upon where an object is located. On the moon, the acceleration due to the moon's gravity is 1.6 m/s^2, which is approximately 1/6 that on the earth. Since an object's weight is dependent upon the pull of gravity, the object's weight will change with the pull of gravity. Since the moon does not strong gravity pull as earth, the object would weigh approximately 6 times more on the earth than on the moon. But the mass doesn't change. Thus a 70-kg object on the moon is still a 70-kg object on the earth.

Step 1: Obtain a Bachelors degree in science subject:
This is the first step required to get in to the field of astronomy. After higher secondary, candidate should obtain a Bachelors degree in science subjects such as physics / chemistry/ mathematics. Apart from these, some universities offer under graduation course in astronomy.
Step 2: Obtain a post graduate degree:
Those who have completed their graduation in science subjects such as astronomy or physics or chemistry or mathematics can look for master level courses like M.Sc astronomy, M.Sc astronomy and space physics, etc.
Step 3: Search for a career in astronomy:
After completing educational programs related to astronomy, candidate can search for a lucrative career in the field. At entry level one can get in to the role of junior research fellow, research trainee, etc. Job positions exists in firms like NASA, Association of Bangalore Amateur Astronomers (ABAA), Bhabha Atomic Research Centre (BARC), and Indian Space Research Organization (ISRO). Department of Science and Technology, Government of India also offer enough career openings. Inter-University Centre for Astronomy and Astrophysics (IUCAA), Technology Information, Forecasting and Assessment Council (TIFAC), etc. are some other firms offering rewarding jobs in this field.

The Indian Institute of Astrophysics is a premier institute devoted to research in astronomy, astrophysics and related physics. This is a full-time research program where in the students' work towards their PhD degree under the supervision of an IIA faculty. Students may join the program in either the first semester beginning in August or the second semester beginning in January.
Entrance examination is held in December followed by interview in January. Students passing the JEST exam are interviewed in May / June. The eligibility criteria for PhD at IIA is M.Sc. in mathematics / applied physics / applied mathematics / optics and photonics / instrumentation / electronics, etc. All around excellent academic performance from 12th to PG will help you fulfill your dream.
You are advised to opt for PCM at 10+2 stage. You are advised to do B.Sc. Physics or mathematics. You may then opt for M.Sc. in mathematics / applied physics.

The standard route to this is not as such reading any specific books at this stage (I'm not discouraging you from reading popular books on cosmology, which you should whenever you can). What you need is a strong background in Physics which translates to a strong undergraduate and graduate (Ph.D) training in Physics.
You can start specialising to Cosmology during 3rd or 4th year of undergraduate by taking courses on General Relativity, Astrophysics and possibly even Cosmology if the course is offered. There's also a question about experimental or theoretical Cosmology (which is not clear from your question) and as such the approaches very different. I'm not familiar with the courses focused on experimental aspects. So, I'll leave it at that.