Could an invisible planet be lurking on the edge of ours? solar system? Can black holes ricochet through space like intergalactic billiard balls? Did our own galaxy’s black hole “wake up” with a bang millions of years ago – and could it do so again?
These may not be the questions that first drove people to study the stars thousands of years ago. But as astronomers peer ever deeper into the dusty corners of space, strange discoveries force them to wrestle with ever stranger questions about the nature of our universe and the limits of what might lie there.
From our own cosmic backyard to the far depths of the early universe, here are five of the most mysterious objects scientists have discovered in space—and the best explanations for what they are.
Planet Nine
Far beyond Neptune’s orbit, a mysterious, massive entity may be moving through the ring of icy objects that surrounds our solar system. Scientists studying this region have found that the orbits of more than a dozen rocky objects have been slightly altered, as if they were being pulled by the gravity of a huge, unseen planet – a theoretical object known as Planet Nine.
This hidden world is believed to be five to 10 times more massive than Earth and would take up to 10,000 years to complete one orbit around the sun. But apart from the strange “bends” in the orbits of nearby objects, there is still no concrete evidence for the existence of Planet Nine. If it is there, slowly orbiting more than 500 times farther from the sun than Earth, the mysterious world is too dark to detect with current telescopes.
However, the upcoming Vera C. Rubin Observatorywhich is currently under construction in Chile and will eventually record a 10-year time-lapse video of the night sky, should be able to spot more evidence of the elusive world — potentially confirming or denying its existence once and for all.
“The Runaway Black Hole”
In April 2023, astronomers announced the discovery of something never seen before: an “escaped” black holeunbound by any galaxy and blazing through space at 4,500 times the speed of sound with a vast trail of stars trailing behind it.
The black hole is estimated to be 20 million times the mass of Earth’s sun, while its bright tail may be more than 200,000 light-years long (about twice the diameter of Milky Way). Observations by the Keck Telescope in Hawaii found that one end of this star trail appears to be associated with a distant dwarf galaxy from which the freely rotating black hole may have been astronomically detected.
Black holes form the hearts of large galaxies like our Milky Way, anchoring the surrounding gas, dust, and star systems in place. So how can one of these space monsters just fly away? According to the study’s authors, it’s possible that the black hole once orbited a second black hole in a rare binary arrangement — then, when a third black hole was introduced into the system during a galaxy merger, chaotic gravitational interactions sent one black hole flying in the wild black there. If confirmed by subsequent studiesthis would be the first evidence that black holes can escape from their galaxies.
JUMBO at the James Webb Telescope
Black holes aren’t the only cosmic escapees; planets are also seen on Lam and in much greater numbers. In 2023, the James Webb Space Telescope (JWST) detected more than 500 free-floating “rogue” planets. passing through the Orion Nebula. Approximately 80 of them were observed orbiting each other in binary pairs, a phenomenon with no clear explanation. Because these rogue worlds are roughly the size of Jupiter, scientists have dubbed them Jupiter-mass binaries — or JUMBOs.
NASA thinks there might be trillions of rogue planets wandering our galaxy, many of which were knocked out of orbit during the chaotic early days of the star system’s formation. However, current models fail to explain the existence of JUMBOs. One theory suggests that these strange objects formed directly from collapsing clouds of gas and dust in interstellar space, in a scaled-down version of how stars form. Another theory says that a passing star may have pushed the objects out of orbit, but the models show that this explanation is highly unlikely. For now, JUMBOs represent a large-scale puzzle for astronomers.
Fermi bubbles
The black hole at the center of our galaxy isn’t (hopefully) going anywhere anytime soon, but it has acted in unexpected ways in the not-so-distant past. Astronomers can see the evidence of massive, energetic eruptions from our black hole in the form of two sets of huge bubbles – known as Fermi bubbles and eROSITA bubbles — that tower above our galaxy. These overlapping swaths of energy extend across the center of the Milky Way like a giant hourglass, stretching approximately 25,000 light-years above and below our central black hole. Measured together, the bubbles span about half the width of the galaxy itself.
Despite their extraordinary size, you cannot see them in the sky; the Fermi bubbles, filled with fast-moving particles called cosmic rays, can only be seen by telescopes that detect gamma rays, while the eROSITA bubbles—filled with extremely hot gas—are only visible as X-rays.
Astronomers don’t know exactly how the bubbles formed, but a 2022 study suggests they are the result of a huge a black hole explosion lasting more than 100,000 years, beginning approximately 2.6 million years ago, when vast amounts of matter poured into the mouth of our black hole. If confirmed, this hypothesis suggests that our black hole was active much earlier than previously thought.
The big question
While studying a strange patch of starlight known as Herbig-Haro 46/47, JWST spotted something even more mysterious in the far background of the image – a deep-space outflow of hot gas perfectly shaped like a question mark.
It’s not clear exactly what the object is or how far away it is, but its reddish color in the JWST images suggests the object is extremely ancient, with its light stretching into increasingly redder wavelengths as it traverses vast cosmic distances to reach us. It could be a galaxy, or perhaps several galaxies, tearing apart each other during a chaotic merger, researchers told sister site Live Science Space.com in 2023
Whatever it is, the cosmic question mark is just one of many puzzles introduced by JWST’s groundbreaking observations. Revealing his identity may have to be put on the back burner in the face of more pressing questions – like whether we completely wrong for our understanding of the universe?
