Dear friend, thank you for your question. Your question shows that what you wish to become in future. Here you have not mentioned your educational qualifications and what you are doing at present. Let me tell you that for any job the interpersonal skills or soft skills or peoples skills or communication skills or personal skills are very important for everyone, whether in private sector or governmental organization.
It has been said that person with strong interpersonal skills are very successful in personal, professional and social life. The persons with good interpersonal skills are are very calm, cool, confidant, optimistic and charismatic in personalities.

Since you wish to become an astronomer, therefore, you have to be in regular contacts with colleagues, superiors and clients. Therefore, you have to be very good at your interpersonal skills. Using your interpersonal skills you can covey your opinions and views to other effectively.
Let me tell you something about types of interpersonal skills;
Communication skills; how to say and what to say
Non verbal communication skills; here we do not say anything, our body language conveys the message
Listening skills; how do we interpret the verbal and non verbal messages sent by others
Negotiation; working with others to come to a common conclusion
Problem solving; working with others to identify, find and solve problems
Decision making; Exploring and analyzing options to make sound and working decisions
Assertiveness; Communicating our ideas, beliefs, and notion, needs and wants freely
Anger management; one should be able to control anger, one should express anger at right time and tight place. This should be used rarely and for solving some problems.

Interpersonal skills are so common and every one is borne with it, but we never take it seriously. we never care how we communicate with others and how other feels with our behavior. Now a days companies are recruiting personals with strong interpersonal skills. People learn Interpersonal skills by interacting with others in family, in schools and socializing with your peers.
Healthy interpersonal skills reduces stress, resolve conflict, improve communication, enhance intimacy, increase understanding and promote joy.
In nutshell, the interpersonal skills are very important part of personality of an astronomer, since he or she has to spend long time in space with many colleagues during the process of exploration. But in office also the person or astronomer has to be very cooperative and supportive, which can be achieved by having strong interpersonal skills.

Good Luck...