This is apparently a rocket test by U.S. Navy off the coast of Southern California. The Pentagon issued a statement that the Navy Strategic Systems Programs conducted a scheduled test of a Trident II (D5) missile from USS Kentucky, an Ohio class submarine.
The missile was not armed, according to the statement, and tests are conducted on a frequent, recurring basis to ensure reliability of the system.
“Navy Strategic Systems Programs conducted scheduled Trident II (D5) missile test flight at sea from USS Kentucky, an Ohio Class SSBN, in the Pacific Test Range off the coast of Southern California,” Navy Cmdr. Ryan Perry said in a statement.
“The tests were part of a scheduled, on-going system evaluation test,” he said. The Trident II is a submarine-launched ballistic missile.
The Navy said it does not typically announce missile tests, and information about tests of Trident II missiles is classified prior to launch.