UFO in Space Station Video? Not Quite

A possible "UFO" sighting from the International Space Station actually has a fairly mundane explanation. And it has nothing to do with aliens.

When you see a light in the sky, do you automatically assume it's a plane, satellite, meteor, star, planet or... an alien? If in doubt, would you go so far to say it's a "UFO"? A UFO, by definition, is an "unidentified flying object," not necessarily a vehicle piloted by otherworldly beings. It's unidentified, it's flying, it's an object. It's a UFO!

But really, though you're not saying it's aliens, it's aliens. I know how this works.

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In fairness, in this most recent viral UFO sighting, a Youtube conspiracy theorist points out that a slowly-moving light over the limb of the Earth as seen from the International Space Station could be a meteor. The UK's Mirror.co.uk went one step further to quote another un-credited theorist saying it could also be a Chinese space station. A FOX affiliate reinforced the idea that NASA was covering something up. And as the eerie soundtrack that's been edited over the video suggests, the viewer is left to his or her imagination as to what it could really be.

Though the tabloid press is obviously very impressed with this latest conspiracy, it's fairly obvious what the UFO is. It's not a meteor. Nor is it a Chinese space vehicle (Tiangong-1's orbit is wildly different from the space station's and Tiangong-2 hasn't even been launched yet). And guess what? It's not even a UFO. The blatant obviousness of what the object is makes me wonder why an apparently seasoned ufologist bothered to edit a pixelated zoomed-in video of the orbital oddity.

So what is it?

On July 9, while watching the live feed from the ISS HD Earth Viewing Experiment, Youtube user Streetcap1 saw a bright dot slowly descend toward the Earth's limb apparently just after sunset. As the object appears to touch the top of the atmosphere, it stops and the transmission is cut.

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Firstly, the slow descent quickly told me that this bright object wasn't a meteor.

Sure, meteors have been spotted by astronauts and cosmonauts on the ISS before -- there's even research programs focused on the detection of meteors hitting the Earth's atmosphere from space. But most meteors are no bigger than a grain of sand and burn up in the atmosphere in a fraction of a second. The light they produce is caused when a meteoroid slams into the atmosphere at high speed, generating a shock wave through ram pressure. This creates intense heating in front of the meteor, causing it to burn up on entry. Most meteors burn up harmlessly at high altitude, but larger ones my travel further and break apart as the atmosphere gets thicker, erupting as a fireball or bolide. Any fragments that make it to the ground are called meteorites.

Astronauts have to be crazy lucky to photograph meteors from the space station, but it has been done, as seen here:

So this slowly-moving object isn't a meteor. But could it be a bigger object, perhaps an asteroid?

Well, though bigger, an asteroid moving relative to Earth would still be moving at a fast pace. Check out this table of recent (and future) close encounters with near-Earth objects (NEOs), which are asteroids that buzz our planet regularly. Of particular note is the "Relative Velocity" column. The units are kilometers per second. That's fast. The fastest bullet available commercially travels at a speed of 0.12 km/s. So we have to remember that in space, things move really fast (an issue that quickly becomes apparent when considering the space debris threat to the space station and satellites). And these speeds are just the NEO's motion around the sun; should one get pulled into our planet's gravitational well and hit the atmosphere, it would be accelerating and traveling much, much faster. For this object to be an asteroid, it would have to be very big and far away (well beyond the Earth's atmosphere) to explain its apparently slow motion.

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Next up, why does the object seem to stop before the transmission is cut?

Well, this is easy. If you've ever used Facetime or Skype just as your internet cuts out, you've already experienced this. As the internet drops, the image of who you were talking to freezes and then disappears. If you've watched the space station's live feed for any amount of time, loss of signal is a VERY regular occurrence and the screen freezes before this screen pops up:

This screen is basically the space station's "no internet connection" error. But this isn't due to NASA's cable provider working on underground cables, it's due to signal relay satellites being out of range during the space station's 90 minute orbit. There are, after all, only a handful of satellites that the space station connects with and as they pass beyond the horizon, connection is lost before a new connection can be made.

"The station regularly passes out of range of the Tracking and Data Relay Satellites (TDRS) used to send and receive video, voice and telemetry from the station," NASA spokesperson Daniel Huot told CNET.com. "For video, whenever we lose signal (video comes down on our higher bandwidth, called KU) the cameras will show a blue screen (indicating no signal) or a preset video slate."

So, going back to the UFO video, just before the signal was lost, the object appears to stop its descent. That's just the last frame lagging and freezing before the connection was lost. Also you'll notice that the pixelation caused by compression artifacts in the signal stops shimmering. This means the video froze, not that the object physically stopped in space.

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So we know what it isn't, time to work out what it is.

It just so happens there's an archive of recorded footage (below the live feed) from the space station camera and, after a few minutes of skimming through each video, the same artifact appears at the same time, just after sunset. Yes, a bright dot seems to descend toward the limb of the Earth at the same pace as the setting sun every single day. It's quite beautiful, and well worth your time to watch sunset and twilight from orbit. Don't take my word for it, look at this recording at the 0:28:19 and 2:01:00 timestamps, the time between two sunsets as recorded by the space station's camera.

What you see here is a camera view looking behind the space station's direction of orbit, with the docked Soyuz vehicle to the right. As the Earth rotates below, the sun sets. After the glare of the sun disappears, lighting up the atmosphere on the limb, a dot also drops to the horizon. Look for it here:

So what, apart from the sun, would be dropping toward the horizon, just after sunset?

As any amateur astronomer knows, if you have clear skies shortly after sunset, often the brightest "star" in the twilight sky is Venus. And that's what we're seeing here. It's not a UFO, it's most definitely a very well known object. And we see it set after the sun, every 90 minutes in the space station live feed.

It's a planet.

It's Venus.

When initially seeing the conspiracy video featuring a bright dot, you may have been forgiven in thinking that something was awry. The eerie music and the UFO speculation would have certainly led many on this path, even turning a badly-edited video into something that's deemed "newsworthy" by some news outlets. And this is where a little skeptical thought would have been useful.

There are many weird and wonderful things out there, but sometimes it's worth taking the time to consider when something is truly weird and when it's something that can be easily explained using a little logic.

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