Astronomy Picture of the Day . ... Each of the numerous granules is the size of an Earth continent, but much shorter lived. ... Some of these particles strike the Earth and cause aurora. ... The Sun is a bubbling ball of extremely hot gas. ... On the left is a normal star field containing the constellation Orion. ... A Wolf-Rayet Star Blows Bubbles . ... Wolf-Rayet stars can blow bubbles. ... Wolf-Rayet stars generate bubbles because they continually eject their outer atmosphere as a stellar wind. ...