It is estimated to contain at least 200 billion stars and possibly up to 400 billion stars . The figure depends on the number of very low-mass , or dwarf stars , which are hard to detect , especially more than 300 light years from our sun . It is estimated to contain at least 100 billion stars and possibly up to 400 billion stars , the exact figure depending on the number of very low-mass , or dwarf stars , which are hard to detect , especially more than 300 l from our sun , and so current estimates of the total number remain highly uncertain .