After being shut down for two years, the Large Hadron Collider (LHC) is back online, CERN announced Sunday.

"Today at 10:41am [local time], a proton beam was back in the 27-kilometer ring, followed at 12:27pm by a second beam rotating in the opposite direction," the European Organization for Nuclear Research reported in a statement.

"These beams circulated at their injection energy of 450 GeV. Over the coming days, operators will check all systems before increasing energy of the beams."

The LHC is set to ramp up its energy capacity over the coming months, reaching 6.5 Tera-electron Volts (TeV) per beam.

Ars Science Editor John Timmer toured the facility, which straddles the French-Swiss border, while it was under repairs: