The sun had already set and twilight was setting in at southern Colorado's San Luis Valley.

Researchers were in the Hooper, Colorado's UFO watchtower, when they saw a bright light move across the Sangre De Cristos mountains.

“When it got over the sand dunes, it had steadily faded out,” said Alejandro Rojas, a renowned UFO researcher and the director of public education for the Mutual UFO Network (MUFON). “That was pretty dang strange to think of what that might have been.”

Colorado-based MUFON is hosting its 40th International UFO Symposium at the Marriott Denver Tech Center from Thursday to Sunday. Speakers will present evidence and research concerning new UFO sightings.

“It's a chance for UFO researchers and investigators to get together and compare notes and research findings,” said James Carrion, international director with MUFON.

“It's also a chance to educate the public, in general, of what's happening.”

The symposium is open to the public and participants can buy a ticket for the whole weekend, for one day, or for one particular speaker.

Colorado averages around a dozen sightings a year, placing the state in the country's top 10 for UFO reports, said Rojas.

“All pictures submitted are very similar to one another,” said Rojas. “It is a large, circular, saucer-shaped object hovering by itself in the sky.”

Rojas said although researchers aren't sure if the UFOs are of extraterrestrial origin, they are of advanced technology.

“Witnesses say it stays in the area for a moment before it takes off at extraordinary speed,” said Rojas.

Researchers are constantly running into skeptics, but Rojas said various scientists, doctors and physicists have been investigating UFOs for decades.

Carrion said many of the skeptics don't take the time to investigate the data, quickly dismissing research “because it isn't something in their world view.”

“They just diffuse it at once rather than take more of a debunking tactic,” said Carrion. “This is really unfair because we spend the time, we look at it and produce data. I think if someone is going to try to exceed our data, they should actually take a look at it.”

University of Colorado philosophy professor Carol Cleland believes it is highly improbable that intelligent extraterrestrial life and UFOs exist.

“I think that intelligent life is rare,” said Cleland, who is also affiliated with the NASA Astrobiology Institute. “And I think that technologically sophisticated intelligent life that is capable of traveling among stars is probably exceedingly rare.”

Cleland said given the large number of solar systems, stars and galaxies in the universe, life could exist elsewhere.

“Whether it's close enough to visit us and whether it's technologically sophisticated enough is another question,” she said.

Cleland said there is a possibility the physics of today could be wrong, therefore making short travel among the other worlds possible.

“But the prospects of intelligent life visiting us — with what we know about the current laws of physics — I think is extremely low,” she said.

Rojas cited popular theoretical physicist Michio Kaku as one of many who believes it is possible to go vast distances in a short amount of time.

Four speakers with Ph.D.s, who have each been studying UFOs for 30 years, will speak at the symposium.

“There are just these unexplained instances,” said Rojas. “Maybe only one out of 10 of these sightings are truly something of note. ... Even in that case, that means there are some truly anomalous things that should be investigated.”

One of the speakers at the symposium will be nuclear physicist Stanton Friedman, the original civilian investigator of the 1947 Roswell UFO incident in New Mexico.

“We certainly have an increase in sightings on a regular basis,” said Rojas. “So it seems that more and more people are becoming more comfortable with the idea (of UFOs).”

IF YOU GO
What: The 40th annual International UFO Symposium
When: Thursday through Sunday
Where: Denver Marriott Tech Center Hotel, 4900 S. Syracuse St.
Cost: $29-$249
www.mufon.com