Space · STEREO and SOHO (NASA/ESA).STEREO and SOHO · the “UFOs” beside the Sun

SOHO, the solar observatory of ESA and NASA, posts its images online, and NASA's twin STEREO spacecraft, Ahead and Behind, do the same. Their coronagraphs and wide-field cameras block the Sun's disc to see what surrounds it, and that view, full of stars, planets, comets and sensor defects, has been a steady source of supposed UFOs. In January 2003 the SOHO team devoted a page to explaining it: ever since launch, it wrote, a number of people had claimed to see flying saucers in its images, and they had always turned out to have an ordinary cause when examined by experienced scientists. The page showed step by step how a single cosmic-ray hit in an image from the EIT telescope of 18 January 2001, enlarged and interpolated and given a different colour table, became a craft with a glow and exhaust fumes, and noted that this same image, after a strikingly similar enhancement, had appeared as proof in the Perth Sunday Times.

At the end of December 2011 came the STEREO episode. Around the 26th, a triangular or diamond shape entered the field of view of the HI2 camera on STEREO Behind, moving from right to left just above the occulter on the right-hand side. The STEREO Science Center published the explanation together with the original movies: at the same moment the very bright planet Venus was entering from the lower left corner, and the shape and the planet moved in step, always in nearly opposite positions across the centre of the detector. It was an internal reflection of Venus in the telescope optics, an effect the team had seen many times before; the same sequence showed the Earth, dimmer, and the tail of Comet Lovejoy.

On 24 April 2012, SOHO's LASCO C2 coronagraph recorded beside the Sun what a blogger described as a metallic, jointed ship with a gigantic extension, and a YouTube video spread it. Nathan Rich, lead ground systems engineer in the solar physics branch of the US Naval Research Laboratory, which analyzes LASCO data, explained that the streaks were consistent with energetic particle (proton) impacts on the camera's sensor, and that such artifacts do not persist from image to image. According to the article that carried his explanation, a particle crossing the sensor at a shallow angle lights up a line of pixels, and the ship's supposed arm was one of those lines.

In July 2020, Scott Waring, who has posted sightings on his website for years, showed a black cube in images from SOHO's EIT telescope that the Daily Express said was ten times bigger than the Earth. Alex Young, a NASA solar astrophysicist who worked on SOHO, told the fact-checking agency Lead Stories that it was a simple data dropout: the images are assembled from blocks, and a block that does not arrive shows up black and square. Lead Stories documented similar cubes that Waring had attributed to SOHO in 2011, 2013, 2016 and 2017.

In February 2020, STEREO Ahead repeated the 2011 phenomenon: a cross inside a circle, and later a cone, entered its HI2 camera at the same time as Venus did on the opposite side, and the team explained it the same way. The last episode, on 20 December 2022, was different. Zesheng Yang, a Sungrazer project volunteer who has discovered many comets in SOHO data, reported an object that appeared in both cameras, LASCO C2 and C3, and that over about two hours swerved sharply away from the Sun. The team acknowledged that in 27 years SOHO had never seen anything quite like it. Wavy particle trajectories are common within a single exposure of about 25 seconds; what was new was that this one showed up for hours, in many images and in both cameras.

None of these images had a witness looking at the sky: the object exists only on the detector, so the question is not what someone saw but what the instrument recorded and why. What sets them apart is that the data are public and that the people who operate the telescopes answered with those same data. Each explanation comes with a test anyone can repeat. The Venus reflection gives itself away because it moves as a mirror image of the planet on the other side of the detector's centre. A cosmic ray appears in a single image and not in the next one, although in the web images it can repeat if a lost block was filled in from the previous image; the raw data settle it. A lost block of data shows up as a black square, because the image arrives in blocks. The 2003 page summed up the rule that applies to all of them: a claim without the date and time of the image is close to worthless, because nobody can check how it was processed.

The 2022 case also shows the limits of that method. The SOHO team did not see the speck of dust; it inferred it. If the object were near the Sun, it would have to be planet-sized to shine like that, amateur astronomers would have seen it long before, and no body at that distance can bend its path so quickly. If it were halfway, even at the size of the Space Station, it would saturate the images. Only something very small and very close fits, a few metres from the spacecraft, and the previous image showed exactly a shower of debris thrown up by a micrometeorite, with a bright streak aligned with the object's first appearance. It attributed the curve to the Lorentz force, effectively static electricity: the spacecraft carries a net charge, and the speck moved away repelled by it. It is a deduction, not a direct observation, although the team considered it quite conclusive and the debris shower was indeed recorded.

Taken together, the episodes show how a UFO is born in a scientific image. The first step is almost always a real defect of the instrument; the second, an enlargement or a change of colours that makes it look solid; the third, a size figure calculated as if the object were beside the Sun, which is not checked. The SOHO team wrote in 2003 that when it explained, it was accused of covering up, and when it stopped answering someone who would not accept the explanation, of clamming up. The answer of the teams of both missions was transparency: STEREO's published the movies and marked on the image where Venus, the Earth and the artifact are, and SOHO's explained step by step how a “UFO” is made. That material, with its institutional provenance and first-hand analysis, is what gives this set its evidential strength, even though what it documents is an instrument defect and not an object.

The explanation of the 2020 cube is the weakest in the set, not because of its content, which matches what the 2003 page already described, but because it comes through the reply Alex Young gave to a fact-checking agency rather than from a mission page.