History of globulettes in the Milky Way

Abstract

Globulettes are small (radii < 10 kAU) dark dust clouds, seen against the background of bright nebulae. A majority of the objects have planetary mass. These objects may be a source of brown dwarfs and free floating planetary mass objects in the galaxy. In this paper we investigate how many globulettes could have formed in the Milky Way and how they could contribute to the total population of free floating planets. In order to do that we examine H-alpha images of 27 H II regions. In these images, we find 778 globulettes. We find that a conservative value of the number of globulettes formed is 5.7 × 10 10. If 10% of the globulettes form free floating planets then they have contributed with 5.7 × 10 9 free floating planets in the Milky Way. A less conservative number of globulettes would mean that the globulettes could contribute 2.0 × 10 10 free floating planets. Thus the globulettes could represent a non-negligible source of free floating planets in the Milky Way.