from the musical, the 10th sailor senshi? on the other side of the sun? I've been searching and searching and there are no fanfictions about her nor is there any sites with any infomation besides this one http://artsandstuff.tripod.com/sailorastarte/
I'm sorry my friend...sailor astarte is made up. I'm not very sure about the musicals (I haven't seen all of em yet) But that website's anime pics, are fake. You'd be amazed how many people on the internet make up their own sailor senshi and use some of the actual senshi pics and make them someone else....
Many days I wonder if my blue seas will follow me to my ocean
From wikipedia: "Other Senshi appear in the manga, such as Usagi's non-canonical second daughter, Kousagi, who appears as "Parallel Sailor Moon" in a humorous short story of the same name. Another short story, The Story of the Hammer Price Shrine, centers around two girls named Naruru and Ruruna who imitate Senshi, along with a man who calls himself Tubby Mask. The Sailor Moon musicals also introduce new Senshi, including Sailor Astarte, Sailor Buttress and others."
She only existed in the musicals according to wikipedia, I don't know if that information is correct or not regarding. I also found a source that states that she appeared in the summer of 2000's musical, so it is possible she wasn't made up.
The anime pictures are fake, though, and at some points it is very clear that they are of the other senshi just edited at some points.
What Wink568 said its absolute true. She was only made up for the musicals. As for the pictures its pretty obvious that they are fake. it's just editing of Hotaru(Sailor Saturn).