The alleged SOHO UFO explained

This image, according to “expert ufologists”, supposedly shows a UFO clearly taking off from the Sun after refueling, feeding off of its energy and leaving behind a trail of solar plasma, the spaceship fuel


The argument is that the trail is clearly the same color as the solar plasma, while the tip point is white, made of a different material, probably a metallic object. Now, that’s interesting because this image is almost perfectly monochromatic. There are no colors here, this is a black-and-white picture taken in ultraviolet light (invisible to the human eye) that has been colored yellow to make it look nicer. The ufologists are right in that this image was taken by the SOHO satellite at the specified time and date, it’s not a fake. All the SOHO data, including raw data, are publicly available on the web thanks to NASA’s investment in total transparency and public outreach. So yes, it’s very ironic that they have to spend money and effort to make lots of data available so that some folk can look for UFOs in the data and accuse them of lying and hiding information. But I digress, back to the image. It was taken by the EIT (Extreme-ultraviolet Imaging Telescope) instrument at a 28.4 nanometer wavelength. There is nothing magic about this wavelength. It was chosen simply because there is an emission line there that is useful for solar scientists to determine the coronal temperature, in combination with images from the other channels. EIT takes nearly simultaneous images at other similar wavelengths in the ultraviolet, as seen in the picture below. The wavelengths are 17.1 (blue), 19.5 (green) and 30.5 (red) nm, respectively. It’s interesting that there is no UFO in the other channels. I guess the “expert ufologists” forgot to mention this point. Or perhaps they didn’t bother checking the rest of the data.


SOHO is almost obsolete. It was launched in 1995 and its technology is from the 80s (keep in mind that space missions always carry technology that is roughly a decade older than their launch date, due to the strict policies on reliability and past experience). It is maintained with minimal resources for a sake of historic data overlap but all of its technology and functionality have been superseded by a newer satellite, the SDO. SOHO is so old that its successor, the SDO satellite, has already finished its nominal lifetime as well. SDO can be thought of as a SOHO on steroids, with better detectors, higher definition, upgraded technology, etc. So what does SDO have to say about the UFO? It didn’t see absolutely anything. Here is a movie of the Sun, as seen by one of the SDO ultraviolet cameras at that time, at 19.3 nm (I’ve checked the other SDO channels, same result).


Whatever that streak is, it is only seen by SOHO and only by one of the SOHO detectors. Clearly, it is not something near the Sun and it’s certainly not solar plasma expelled by a spaceship. In order to investigate what is going on here, one needs to work with the raw data (also called level-zero data). The images that we have discussed above have been processed by automated algorithms to facilitate scientific studies of the solar features. The processing is done to clean detector defects and imperfections, remove parasitic stray light, eliminate bad pixels and rotate the image so that the North is always up, regardless of the SOHO orientation. A true investigator, one that seeks to find the truth (unlike an “expert ufologist” whose motivation is to find other things), would start by looking at the raw data. Fortunately, NASA makes those publicly available too. Here is what the raw data looks like for the UFO image before processing:


This image is not as nice. We can see a square grid, which is related to how these detectors work, dividing the field of view into smaller blocks. There are also plenty of “hot pixels”, bad detector locations, many of which are caused by two decades of exposure to the hardships of solar radiation and other nasty space conditions. Let’s zoom in on the streak:



Well, this doesn’t really look much like a UFO leaving behind a plasma trail. What could it be then?

SOHO’s EIT/LACO instrument has a webpage that warns us about several issues that might contaminate the images. Particularly important for our discussion here are cosmic rays. Occasionally, a cosmic ray (high-energy charged particles coming from the Universe, the galaxy or even the Sun), will impact the detector, leaving a bright point or streak on the image. An extreme example is this LASCO image below. This is an image taken by LASCO during a solar storm. There are many more impacts here than usual due to the bombardment of charged particles from the Sun.


The central disk in the image is an occulter to block the Sun because LASCO is a coronograph, designed to observe the corona. The corona is so faint compared to the solar disk that we need to cover the disk in order to see it. The shadow running diagonally from the central disk to the bottom-left corner is the arm that holds the occulting disk in place. All the bright points and streaks seen in this image are impacts of charged particles produced by the solar storm as they reach SOHO. The image below shows a blow-up of one of the traces left by the impact of an oblique cosmic ray.


If you think that this trace looks very much like the alleged UFO in the raw image, congratulations! You have solved the mystery of the SOHO UFO.


There is one last outstanding issue here. Isn’t it too much of a coincidence that a cosmic ray would impact so close to the solar limb and run exactly in the radial direction pointing away from the Sun? Well, it would be if this were the only image that you examine. However, remember that SOHO has been observing for 21 years since 1995, taking these images every 12 minutes in 4 different channels. That makes millions of images. The streak analyzed here is about 33 pixels inside the solar limb (the disk edge). The circular stripe defined by the limb with a 33 pixel width makes up 7% of the total number of pixels in the image, which means that there’s a 7% chance that any given cosmic ray will fall in this region. The streak orientation is not exactly radial but close enough to make it look so to the eye, about 2 degrees. The probability that a given streak will depart from the radial less than plus/mins 2 degrees is obviously 4/360. Combining these two numbers, we obtain that approximately 1 out of 1,000 cosmic rays will appear to emerge from near the solar limb and move away radially. Considering that we have long oblique cosmic rays in every 10 to 100 images, we conclude that there should be UFO-looking features in roughly one out of 10,000 to 100,000 images. Remember that SOHO has taken millions of pictures so, not only it is not too much of a coincidence, but in fact one might expect to see more of these in the huge database of SOHO observations.


A final note on NASA conspiracy theories. The notion that NASA conspires to hide a big secret from the public shows a profound lack of understanding of what NASA is or how it works. First of all, one needs to understand that it is a huge organization which currently employs about 20,000 people. And, in the words of Abraham Lincoln, “you can fool all the people some of the time, and some of the people all the time, but you cannot fool all the people all the time”.  Even more important than that, NASA is not really a scientific organization. It is an administration. Its role is basically to get money from the taxpayer and use that money to contract other institutes and organizations to build instruments, analyze the data and do the science. For instance, my institute, the Instituto de Astrofisica de Canarias in Spain, built some parts of two of the instruments onboard SOHO (GOLF and VIRGO). Similarly, other institutes, private companies and universities, have received NASA funding to build parts of the rest of the instrumentation. NASA then gets the satellite and launches it into orbit. That’s their main business. After that, the data are analyzed by each instrument builder. So, essentially, any possible conspiracy would necessarily have to involve not only NASA, but all of the national and international partners who build these instruments both in the US and around the world. This typically means dozens of institutions in a few different countries for a given mission. Since you have different missions observing the Sun, any cover-up operation for a secret solar alien gas station would require about a hundred labs and institutions in many different countries keeping a secret for decades. I know some of these guys who are responsible for the instruments and they are not “men in black” or shady military characters. They are just normal people like you and me. And hey, I’ve seen how some of them talk after having a few beers and, believe me, I wouldn’t trust them with any big secrets :)



Hector Socas-Navarro thanks Joseph B. Gurman, US Project Scientist for SOHO, for helpful discussions