Google has unveiled its highly anticipated “Google Phone,” or the Nexus One, an Android-powered smartphone and the first device the company will sell directly from a new online store.

At a Google press event held Tuesday afternoon at the company’s Mountain View, Calif. headquarters, Google vice president Mario Queiroz billed the new Nexus One as a “superphone” and an “exemplar of what’s possible” on mobile phones running Android.

The Nexus One is a slim touch-screen slab handset manufactured by HTC, the company behind the original T-Mobile G1, the myTouch 3G with Google, and the HTC Hero. The Nexus One weighs 4.6 ounces and measures 0.45-inches thick. It features a 3.7-inch, 480-by-800-pixel glass capacitive AMOLED touch screen, a next-generation 1-GHz Qualcomm Snapdragon CPU, and Android 2.1, a brand new version of the company’s open-source mobile OS.

Other hardware features include a 5-megapixel auto-focus camera with an LED flash and geotagging capability, 512MB of internal memory, and a microSD card slot. Two mics provide Bluetooth headset-like active noise cancellation for improved call quality in loud environments. The trackball doubles as a notification tool, Queiroz said, in that it contains a multi-color LED for indicating incoming calls and other notifications. A 3.5-mm headphone jack and stereo Bluetooth support offer music lovers multiple options for listening to tunes.

This weekend, Google posted a message on its Mobile Blog referring to a new mobile phone concept device that Google’s employees had been given to test. This new device, the blog said, “combines innovative hardware from a partner with software that runs on Android to experiment with new mobile features and capabilities.”

According to reports, the device is Nexus One, Google’s first attempt at a cell phone that it will sell directly to consumers, with software designed entirely in-house.

The phone is being manufactured for Google by HTC Corp., reports said. It runs Android, the operating system for mobile phones that Google developed.