Astronomy Picture of the Day . ... Apollo 12 Visits Surveyor 3 . ... Fliers Around the Blue Snowball Nebula . ... Planetary nebulae are strange. ... Next, although hundreds of planetary nebulae have been catalogued and thousands surely exist in our Galaxy, aspects of the formation process are still debated. The Blue Snowball Planetary Nebula . ... The Blue Snowball is a planetary nebula - and in 5 billion years the Sun will throw off its outer layers and go through a planetary nebula phase. ...