Taylor Swift is surprise releasing another new album. The country-turned-pop superstar turned to social media on Thursday morning (Dec. 10) to reveal that she's dropping her ninth studio album, Evermore, on Thursday night at midnight ET.

The new project is a "sister record" to Swift's eighth studio album, Folklore, she writes. Swift dropped Folklore by surprise in July.

"To put it plainly, we just couldn’t stop writing songs," Swift writes on Instagram. "To try and put it more poetically, it feels like we were standing on the edge of the folklorian woods and had a choice: to turn and go back or to travel further into the forest of this music. We chose to wander deeper in."

The new music arrives just days before Swift's 31st birthday on Sunday (Dec. 13).

"Ever since I was 13, I’ve been excited about turning 31 because it’s my lucky number backwards, which is why I wanted to surprise you with this now," Swift writes in a subsequent post. "You’ve all been so caring, supportive and thoughtful on my birthdays and so this time I thought I would give you something! I also know this holiday season will be a lonely one for most of us and if there are any of you out there who turn to music to cope with missing loved ones the way I do, this is for you."

The standard edition of Evermore consists of 15 tracks, while a deluxe physical edition features two bonus tracks, "Right Where You Left Me" and "It's Time to Go." All digital downloads of the album will include an exclusive digital booklet featuring 16 photos.

The album is rife with celebrity collaborations. Haim appear on a track titled "No Body, No Crime," "Coney Island" features the National, and Bon Iver collaborates with Swift on the album's title track.

Swift also revealed that she'll release a music video for one of the new tracks, "Willow," at midnight ET on Thursday evening. She'll take questions in the YouTube premiere page chat beforehand.

Taylor Swift, Evermore Tracklist:

1. "Willow"
2. "Champagne Problem"
3. "Gold Rush"
4. "'Tis the Damn Season"
5. "Tolerate It"
6. "No Body, No Crime" (feat. Haim)
7. "Happiness"
8. "Dorothea"
9. "Coney Island" (feat. the National)
10. "Ivy"
11. "Cowboy Like Me"
12. "Long Story Short"
13. Marjorie"
14. "Closure"
15. "Evermore" (feat. Bon Iver)
16. "Right Where You Left Me" (Bonus Track)
17. "It's Time to Go" (Bonus Track)

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See Pictures of the Inside of Taylor Swift's Childhood Home: