This past weekend we wrote that social group startup Fridge was shutting down the product. We assumed that meant it was being acquired.

We assumed right. Austin Chang, Fridge's founder, just told us that the company is being acquired by Google+ for an undisclosed amount. The deal closed late last night.

Starting next week, his four-person team will be working on Google+ from New York. Come August, most of them will relocate to Google's Mountain View office.

Fridge currently has 40,000 monthly uniques. More than 20,000 groups have been formed, where users can share videos, instant messages, pictures, polls and events with close friends.

"Right now, Google+ is asymmetric," says Chang. "We're going to help them create shared spaces."

Chang notes that a few different parties were interested in acquiring Fridge, but he never considered selling to any other company. "Fridge fits perfectly into Google+'s plan," he says.

Fridge is a Y-Combinator startup that raised $800,000. Investors put Chang in touch with Google+, and the two companies have been talking about the acquisition for 2-3 months.

This isn't Chang's first exit. In 2005 he sold a social game, Popularity High, to MTV/Viacom for an undisclosed amount.

Click here to learn more about Fridge's business model >>

Here's the letter Fridge just sent out to its users:

fridge google+