Two of our galaxy’s most famous stars were recently photobombed by what appears to be a celestial question mark.
The symbol was spotted in a new image from the James Webb Space Telescope (JWST) of the forming stars Herbig-Haro 46/47, which are well-known and have been frequently observed by astronomers. These two stars can provide clues about how our own sun may have formed. They’re relatively close to Earth, about 1,400 light-years, and relatively young, only a few thousand years old. In fact, they’re still in gestation and have not technically been “born” yet, which is marked when the stars start shining from their own nuclear fusion.
The image is the first of the twin protostars from the NIRCam instrument on JWST. It was captured using infrared light, which penetrates space dust more easily than visual light, and it is the highest resolution image of the objects ever seen at these wavelengths.
The telescope’s astonishing sensitivity allowed the glowing red question mark to be captured in the lower center of the image. The object is far outside our galactic neighborhood, possibly billions of light-years away, says Christopher Britt, an education and outreach scientist at the Space Telescope Science Institute who helped plan these observations.
His best guess is that the question mark is actually two galaxies merging.
“That's something that's seen fairly frequently, and it happens to galaxies many times over the course of their lives,” he says. “That includes our own galaxy, the Milky Way … [it] will merge with Andromeda in about four billion years or so.”
The hints pointing to two galaxies are found in the question mark’s strange shape. There are two brighter spots, one in the curve and the other in the dot, which could be the galactic nuclei, or the centers of the galaxies, Britt says. The curve of the question mark might be the “tails” being stripped off as the two galaxies spiral toward each other.
“It's very cute. It's a question mark … But you can find the colons and semicolons, and any other punctuation mark, because you have 10,000 little smudges of light in each image taken every half hour,” says David Helfand, an astronomer at Columbia University. The sheer number of shining objects we find are bound to create some serendipitous images, and our brains have evolved to find those patterns, he says.
Astronomers have seen similar objects closer to home. Two merging galaxies captured by the Hubble Space Telescope in 2008 also look like a question mark, just turned 90 degrees.
Helfand says the question mark seems to be two objects, the curve and the dot, but could be more that just happened to line up. They could also be completely unrelated objects, he says, if one is much closer to Earth than the other.
Britt warns that estimating distance based only on colors in the image can be tricky. The red of the question mark could mean it’s very far away (light waves stretch as they travel through the expanding universe, shifting to redder wavelengths) or that it’s closer and obscured by dust near the object.
It would take more investigation to identify exactly how far away the question mark is. This could be done by measuring photometric redshifts, determined by the brightness observed through different filters, but this would only provide an estimate for the distance, Britt says. Spectroscopy, which analyzes light from the source to determine its elemental makeup, could provide a more exact distance but requires a separate instrument to measure.
Given the number of intriguing targets spotted by JWST, the question mark may never receive this treatment. For now the source of this symbol in the sky remains a cosmic mystery.