Astronomers -- the men and women who study the stars, galaxies and beyond -- have an almost universal agreement that there's nothing of scientific interest when it comes to the subject of UFOs.

In fact, many professionals who gaze into the heavens actually speak about UFO sightings with disdain -- even though countless military officials, heads of state, newsmakers and commercial pilots have said they've seen unidentified flying objects.

"No serious astronomer gives any credence to any of these stories," said Lord Martin Rees, the official U.K. astronomer royal.

lord martin rees pic

(Courtesy of Lucinda Douglas-Martin)

Rees, author of the new book, "From Here To Infinity: A Vision For The Future Of Science," told The Huffington Post that, while "everyone's fascinated by aliens," he's in favor of the ongoing SETI Institute program -- the search for extraterrestrial intelligence.

"We should look by all possible techniques," Rees said. "We've no idea what's out there, and so we should look for anything that might seem to be some sort of artifact rather than something natural."

While Rees said he hopes real extraterrestrials will be detected within the next 40 years, he's completely and "utterly unconvinced" that any ETs have been visiting Earth.

"I think most astronomers would dismiss these," Rees said. "I dismiss them because if aliens had made the great effort to traverse interstellar distances to come here, they wouldn't just meet a few well-known cranks, make a few circles in corn fields and go away again."

Nevertheless, in a recent HuffPost blog, SETI Institute senior astronomer Seth Shostak wrote about the daily emails he receives from people describing "alien sightings, extraterrestrial plans for Earth, and agitated screeds about the reluctance of scientists to take the whole subject seriously."

seth shostak

(Courtesy of Seth Shostak)

Shostak said very few of those emails "are penned by hoaxers. The correspondents are sincere, and many simply wish to help us in our search for evidence of extraterrestrial intelligence."

While Shostak may at first appear sympathetic to folks claiming that aliens are already here, he said he sees no real evidence.

"It's hard to believe that the aliens have cleverly arranged things so that only governments can find convincing evidence of their presence. ... The fact is, if you're certain that our planet is hosting alien visitors, the way to gain acceptance for your point of view is to prove it."

Are We Alone In The Universe? Lord Martin Rees And Seth Shostak Explore The Possibilities:

Another astronomer, James McGaha, said he agrees with Rees' contention that UFO reports should be dismissed.

"I totally agree with that. Rees is making what I call an elegant argument," McGaha, a retired Air Force pilot and director of the Grasslands Observatory in Tucson, Ariz., told HuffPost.

McGaha held a top secret security clearance during his career and was directly involved with classified projects at the now-legendary Area 51 military facility in Nevada. He's a fellow of the Royal Astronomical Society and has discovered numerous asteroids and comets.

McGaha is also a UFO debunker.

james mcgaha pic

(Courtesy of James McGaha)

"I've got over 40,000 hours looking at the night sky, and I've never seen -- not once in 50 years -- something that I didn't know what it was. I've seen many strange things, but never anything I couldn't identify," McGaha said.

"Most professional astronomers don't look at the sky. Most of them sit in a room with computers and image the sky, so they don't ever go outside and look, and many of them don't know how to actually identify the constellations in the sky -- it's unfortunate, but that's the way it is."

McGaha gives no credence to any of the tens of thousands of UFO sightings or encounters that reliable people have reported.

"I don't think there's a single observation or report that I'm aware of that indicates an alien spacecraft -- not one," he said. "And I've looked at all of the important cases.

"Scientists are very sensitive to evidence and data. What physical evidence is there that an alien spacecraft has actually ever visited Earth? There is none, zero. And until there is -- an artifact, a piece, an alien -- scientists will not even think about investigating this," he said.

McGaha concedes -- just a little -- that UFOs, or alien ships, "are not impossible. If there's an intelligent race out there, they could build a spacecraft and get here. It would be very difficult, would require enormous resources and motivation to do it. It's not impossible, but highly unlikely."

Others disagree about the rift between scientists and the UFO "community."

"I'm dismayed by the lack of understanding between the two groups," said journalist Nick Pope, who used to investigate UFOs for the U.K. Ministry of Defense.

nick pope pic

(Courtesy of Nick Pope)

"Unless they've studied the phenomenon, astronomers are no more qualified to talk about UFOs than ufologists are to talk about, say, titanium oxide production in K-type stars. It's like marine biologists and oil company executives saying they understand each other's fields because they're both looking for something in the sea. The sea is about the only thing they have in common. So it is with astronomers, ufologists and the sky," Pope wrote in an email to HuffPost.

Initially a skeptic, Pope's years at the Ministry of Defense led him to believe that, at the very least, the UFO subject was "worthy of proper, scientific research. Especially where one has, for example, photos, videos or radar data, because such things can be studied in a proper, scientific manner. It's unscientific to ignore data simply because it doesn't fit your worldview."

Pope is one of several speakers -- including retired Air Force and Army colonels -- who are taking part in a special lecture on Sept. 22, titled "Military UFOs: Secrets Revealed," to be held at the National Atomic Testing Museum in Las Vegas.

Are these real UFOs ... or something else?

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  • Lanterns

    These candle-lit Chinese lanterns can rise high into the sky and are often mistaken for UFOs.

  • Melbourne, Australia, Feb. 2013

    This is a composite image of how three alleged UFOs maneuvered about in the sky over Melbourne, Australia, in early February, 2013. The final verdict isn't in yet on whether they're birds, aircraft, balloons, bugs or something truly unidentified.

  • Exploding Weather Balloons, Not UFOs

    On Dec. 20, 2012, a bright, circular object (pictured at the top of this composite image) was videotaped exploding in the skies above Sacramento, Calif. It wasn't immediately identified, resulting in speculation that it was either an alien spacecraft, military top secret weapon, runaway planet, North Korean satellite, among others. Within a short period of time, it became apparent that this was a weather balloon. The bottom part of this image shows such a balloon as it ascended over Tampa Bay, Fla., on July 2, 2012, and exploded in an identical manner as the Sacramento object, probably much to the dismay of all true ET believers out there.

  • Boomerang UFO composite images -- 10-5-12

    This is a composite of images shot by two eyewitnesses of a boomerang-shaped UFO they reported seeing over their Burbank, Calif., home on Oct. 5, 2012. Mutual UFO Network photo/video analyst Marc Dantonio concluded the object was likely "a balloon, floating on the wind that has collapsed in half."

  • Changing UFO Pattern -- Warren, Mich. 1-10-13

    This four-image series of lights in the sky was recorded over Warren, Mich., on Jan. 10, 2013. The lights were seen changing into several patterns. The most logical explanation for these types of UFOs is a series of balloons or lanterns.

  • UFOs Over Earth

    This composite image shows four different times that alleged UFO were photographed above Earth by either space shuttles or the International Space Station. The big question is whether or not they are truly unidentified objects or if they are more likely reflections from spacecraft windows, meteors or fast-moving spacecraft-generated debris.

  • Pink UFOs Or Lens Flares?

    What appear to be pink-red UFOs are actually lens flares from the Google Earth street view camera as it snapped images in Texas (left) and New Mexico (right).

  • Lens flares Arizona

    These two flying saucer-shaped, pink-colored lens flares were created by the Google Maps camera as it drove through locations in Sedona, Ariz. (left) and Flagstaff, Ariz. (right). The images were snapped in April 2009. Submitted to HuffPost by trenna.

  • Lens flare Whiteriver, Ariz.

    This skybound lens flare was created by a Google Maps camera in June 2008 over Whiteriver, Ariz. Submitted to Huffington Post by Cheryl Weeks.

  • Lens flare Gulfport, Miss.

    This very Earthbound lens flare was created by a Google Maps camera in November 2007 at Gulfport, Miss. Submitted to Huffington Post by Jenni Parker.

  • Lens flare Eureka Springs, Ark.

    This seemingly grounded lens flare was created by a Google Maps camera in January 2008 at Eureka Springs, Ark. Submitted to Huffington Post by SE.

  • Lens flare Escanaba, Mich.

    This lens flare appears to be following a car. The Google Maps image was created in October 2008 at Escanaba, Mich. Submitted to Huffington Post by Mary Robinson.

  • Cincinnati Skydivers NOT UFOs Sept. 28, 2012

    On the night of Sept. 28, 2012, a group of strange-looking lights appeared in the sky near Cincinnati, Ohio. First there was one, then, two, then three lights, slowly descending. It turns out, however, that these lights were originating from a group of skydivers performing a pyrotechnics jump at the La Salle High School homecoming event.

  • Weather Phenomenon

    Some UFO sightings may be due to a natural phenomenon known as sprites, like this one shown from 2006. "Lightning from [a] thunderstorm excites the electric field above, producing a flash of light called a sprite," said geophysicist Colin Price.

  • Clouds

    Clouds: Saucer-shaped or "lenticular" clouds that form at high altitudes have been confused with UFOs.

  • Blimps or Advertising Balloons

    Blimps or advertising balloons: These can look like flying saucers from some angles, especially at night.

  • Sunken Ship in the Baltic Sea

    On June 19th the Swedish-based diving company Ocean Explorer discovered something they've never quite seen before. They were exploring in the Baltic Sea between Sweden and Finland looking for sunken treasures when a very unusual image suddenly appeared on the sonar. A 197 feet diameter cylinder shaped object was discovered at the depth of approximately 275 feet which resembles the Millennium Falcon from the movie Star Wars.

  • Baltic Sea UFO 1

    An image released on June 15, 2012, shows a close-up view of the unidentified object sitting on the bottom of the Baltic Sea.

  • Baltic Sea UFO 2

    Close-up of rock bed that forms the Baltic Sea UFO, which still mystifies researchers.

  • Baltic Sea UFO 3

    One of several odd stone circle formations, sitting on top of the unidentified object at the bottom of the Baltic Sea.

  • Antarctic UFO -- Aug. 10, 2012

    A circular UFO hovers above the Neumayer-Station III research facility in Antarctica on Aug. 10, 2012. Theories ranging from a simple weather balloon to a more elaborate ship from another planet have run the Internet gamut. The next slide shows a closeup of the object.

  • Antarctic UFO Closeup -- Aug. 10, 2012

    This is a closeup of the UFO from the previous slide. No official explanation has been offered about the object.

  • Manufactured UFO -- 2011

    Pictured is a quad copter -- a deliberately manufactured UFO created by special effects wizard Marc Dantonio for a National Geographic special, "The Truth Behind: UFOs," which aired in December 2011. On the left is what the small device looks like resting on the ground, measuring 4 feet in circumference. At right, is how it appeared behind a tree in the night sky.

  • Police Dashboard Camera In Texas

    In February of 2012, this fireball was captured by a Texas police chief's A dashboard camera. F.A.A. say this was probably a meteor, falling to Earth. .

  • Meteors

    Meteors: Space debris can create a spectacular light show when it burns through the Earth's atmosphere, and sometimes reported as UFOs.

  • Civilian or Military Aircraft

    Civilian or military aircraft: Planes can look mysterious at night or in certain light conditions, thus confusing an observer.