A US observatory has reopened weeks after it was abruptly and mysteriously closed by the FBI.
The Sunspot Solar Observatory in New Mexico was closed on 6 September for reasons reported to be security-related.
A nearby post office was also closed and both buildings were evacuated.
The FBI would not say why the buildings were closed, nor would the Association of Universities for Research in Astronomy (AURA), the group that runs the observatory.
Even the sheriff did not know what was going on but he reported seeing a Blackhawk helicopter, people around antennas and work crews on towers at the site during the closure.
The closure of the site, also called the National Solar Observatory, attracted the interest of conspiracy theorists, perhaps due to its location.
Created in 1947, it overlooks the Tularosa Basin, a desert that includes Holloman Air Force Base, White Sands Missile Range and the site of the world’s first atomic bomb test.
The telescope was built by the US Air Force and reportedly produces some of the sharpest images available of the Sun.
On Reddit, people offered theories for the closure, ranging from the FBI having uncovered an illegal operation, being the front group for a secret taskforce to “maybe they saw something in the sky”.
Other ideas given by armchair experts include mercury contamination, anthrax in the mail or China spying, the latter two described by their author as “the simplest answers”.
Announcing on Sunday night that the observatory would reopen the next day, AURA said it had been “cooperating with an on-going law enforcement investigation of criminal activity”.
It added: “During this time, we became concerned that a suspect in the investigation potentially posed a threat to the safety of local staff and residents.
“For this reason, AURA temporarily vacated the facility and ceased science activities at this location.
“The decision to vacate was based on the logistical challenges associated with protecting personnel at such a remote location, and the need for expeditious response to the potential threat.”
It has now been decided that there is “no risk to staff”, the organisation said.
“We recognise that the lack of communications while the facility was vacated was concerning and frustrating for some.
“However, our desire to provide additional information had to be balanced against the risk that, if spread at the time, the news would alert the suspect and impede the law enforcement investigation. That was a risk we could not take.”
The association has also hired a security team to patrol the observatory, due to the “significant amount of publicity the temporary closure has generated, and the consequent expectation of an unusual number of visitors to the site”.