Did you know that Sirius Black, Harry Potter's [Images] godfather, takes his name from a star in the dog-shaped constellation Canis Major?

In J K Rowling's [Images] blockbuster Harry Potter series, Sirius is an Animagus, a wizard who can turn himself into an animal, and Sirius' Animagus form is a big black dog.

Two dyed-in-the-wool Harry Potter fans, sisters Chitra and Nikita Agarwal researched connections such as these and more for their book Friends and Foes of Harry Potter, Names Decoded, which has been released by Taylor Publishing in the United States.

Chitra, a sophomore at the Lutheran High School, Dallas, Texas, loves Harry Potter and the Prisoner of Azkaban and Harry Potter and the Goblet of Fire. Ten-year-old Nikita's favourite is also Goblet of Fire.

They spoke to Monika Joshi from Dallas, where they live.

How did you get the idea for the book?

Chitra: We were in Cozumel, Mexico. We were on the beach, and my dad was talking to us about what Sirius Black's name means. My sister told him that Sirius is a constellation star for Canis Major. Dad was like: 'Well you know so much. Why don't you put it all down on paper, and maybe write a book about it?'

What were your sources for research?

Chitra: Our main source of information was this site called The Harry Potter Lexicon. It's this great site for all people who are Harry Potter fans, who really want to find more about the characters.

We typed in 'Harry Potter' on Google and found wonderful sites.

Nikita: We also referred to The Unofficial Guide to Harry Potter; we used J K Rowling's official web site, and some others like Mugglenet.

When did it start? And how long did it take?

Nikita: We started last summer.

Chitra: It took a couple of months because we had to research all the information about each character. Publishing took about a month.

How did you share the job? Who did what?

Nikita: We both kind of did the same thing. She would do all the houses, like Gryffindor, Ravenclaw, and I would do characters, like Dumbledore.

Who is this book meant for?

Nikita: It's a book for anybody who likes to read Harry Potter or has never read it before. Anybody, really.

Who is your favourite character?

Nikita: My favourite character is Dumbledore. (The book is also a tribute to Dumbledore and all men and women fighting evil around the globe.)

Chitra: I like Ron Weasley. Even though he is kind of not smart and acts stupid, he makes me laugh, not just in the movie but also the book. The way he acts and relates and talks with other people, he just makes me laugh. I wish I had a friend like that.

And whom do you dislike?

Chitra: I would have to say I dislike Draco Malfoy. He just needs to grow up. He complains about everything.

How close are these characters to real people?

Nikita: If I were to relate myself to other characters, I would probably have to say (I am like) maybe Ginny Weasley or Harry Potter himself. One of my best friends is a fighter, so she's probably be Hermione. All my friends kind of relate to Harry's friends.

Who else was involved in bringing out the book?

Chitra: My parents, our creative writing teacher Judy Pryor, Taylor Publishing, Florence McLure -- who designed the book and formatted it -- and Benjamin Vincent, the artist.

The book has a foreword by your creative writing teacher. How did your teachers help?

Chitra: My teachers helped me with grammar, making my sentences more complex, developing the words, using the vocabulary.

What other things do you write?

Chitra: We write essays, we do a lot of projects that involve creative writing. That helped us during the book.

How did Harry Potter come in?

Nikita: We just had some creative writing classes with one of our tutors. Whenever my sister and I had to write an essay for school, a story or a journal entry, it would always be about Harry Potter. And my dad was like, 'You guys are really into this. Why don't you publish all this stuff?'

What other books do you enjoy?

Nikita: I like fantasy, a little bit of mystery, and I read a little bit of romance. My favourite book is The Secret Life of Bees. My sister reads fantasy, anything that has to do with Harry Potter. She just picks up any book and starts reading it.

How did you get introduced to Harry Potter?

Nikita: In the library. I picked up a Harry Potter book and started reading it. I couldn't keep my eyes off it. Then I checked out all the books from the library.

Which book did you pick up first?

Nikita: It was the second book, Harry Potter and the Chamber of Secrets. I ended up reading the first book last.

Why did you choose to write about Harry Potter?

Chitra: It's just Harry's character, and the way J K Rowling has formed him through the years. In the first book, he was kind of thinking about how he is so famous; in the sixth book he is fighting Voldemort. It is how he progresses and how all the characters go up to be who they really area.

All the characters remain who they are, as they grow and develop.

For example Hermione -- she's stayed the same throughout the book, she has never really changed. She really cares about Harry and Harry's her best friend and she helps him out in times of misery. Each character has a part in the book, and throughout the books, one through six, they just progress in their characters.

You have dedicated the book to your grandparents.

Chitra: They are a great inspiration, and kind of developed us too. When we were little, they were there by our side, and were our mentors. They were wise and we just appreciate us for making us the beautiful women that we are.

Do they live with you?

Nikita: My dad's parents passed away. My mom's parents live in California.

What are your other interests?

Chitra: Other than writing, hanging out with my friends, reading, snorkelling, skiing, swimming, and basketball.

Also see
J K Rowling on finishing Harry Potter
A spell called Harry Potter!
Goblet of Fire: Not for Muggles
Harry Potter and post-7/7 England
The Harry Potter Quiz