Retired astronaut enters race for US senate seat in Arizona

Retired U.S. astronaut Mark Kelly, whose wife former Congresswoman Gabby Giffords was wounded in a 2011 mass shooting, plans to run for a U.S. Senate seat in Arizona, he said in a video posted to Twitter on Tuesday. Giffords stepped down from Congress after sustaining a serious head injury in the attack but has emerged as one of the leading voices of the U.S. gun-control movement.