Could there be an invisible planet lurking on the edge of our planet? 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 led people to study the stars thousands of years ago. But as astronomers look deeper and deeper into the dusty reaches of the cosmos, extraordinary discoveries have forced them to grapple with increasingly strange questions about the nature of our universe and the limits of what might lurk beyond it.
From our own cosmic backyard to the distant 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 the orbit of Neptune, a mysterious, massive entity may be moving through the ring of icy objects that surround our solar system. Scientists studying this region have found that the orbits of more than a dozen rocky objects are subtly altered, as if pulled by the gravity of a huge, invisible planet – a theoretical object known as Planet Nine.
This hidden world is estimated to be five to ten times as massive as Earth and will take as long as 10,000 years to complete a single orbit around the Sun. But apart from the strange ‘twists’ in the orbits of nearby objects, there is still no concrete evidence of Planet Nine’s existence. If it’s out there, slowly orbiting more than 500 times further from the sun than Earth, then the mysterious world is far too dim to detect with today’s telescopes.
However, the upcoming Vera C. Rubin Observatorywhich is currently under construction in Chile and will eventually record a decade-long time-lapse video of the night sky, should allow more evidence of the elusive world to be discovered – which could prove its existence once and for all confirmed or denied.
The ‘runaway black hole’
In April 2023, astronomers reported the detection of something never seen before: a ‘runaway’ black holedetached from any galaxy and hurtling through space at 4,500 times the speed of sound, with a vast trail of stars behind it.
The black hole is estimated to have 20 million times the mass of the Sun on Earth, while its bright tail could be more than 200,000 light-years long (about twice the diameter of the Sun). Milky Way). Observations with the Keck telescope in Hawaii have shown that one end of this stellar trail appears to be connected to a distant dwarf galaxy, from which the free-spinning black hole could have formed astronomically.
Black holes form the hearts of large galaxies such as our Milky Way and anchor the surrounding gas, dust and star systems in place. So how does one of these cosmic behemoths simply vamoose? According to the study authors, it is possible that the black hole once orbited a second black hole in a rare binary arrangement. When a third black hole was introduced into the system during a galaxy merger, the chaotic gravitational interaction caused one black hole to fly. in the wild black yonder. If confirmed by follow-up studiesthis will be the first evidence that black holes can escape from their galaxies.
The JUMBOs of the James Webb telescope
Black holes aren’t the only cosmic runaways; Planets have also been seen in flight, and in much greater numbers. In 2023, the James Webb Space Telescope (JWST) was detected more than 500 free-floating “rogue” planets racing through the Orion Nebula. About 80 of these were spotted in binary pairs orbiting each other – a phenomenon with no clear explanation. Because these rogue worlds are about the size of Jupiter, scientists called them Jupiter-mass binaries – or JUMBOs.
NASA estimates this may be the case trillions of rogue planets that roam our Milky Way, many of which were thrown out of orbit during the chaotic early days of galaxy formation. However, current models cannot explain the existence of JUMBOs. One theory suggests that these bizarre 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 a passing star could have pushed the objects out of orbit, but models have shown that this explanation is very unlikely. For now, JUMBOs pose a gigantic puzzle for astronomers.
The Fermi bubbles
The black hole at the center of our galaxy won’t (hopefully) be going anywhere anytime soon, but has manifested itself in unexpected ways in the not-too-distant past. Astronomers can see evidence of huge, energetic outbursts from our black hole in the form of two sets of giant bubbles – known as the Fermi bubbles And eROSITA bubbles – which towers above our galaxy. These overlapping lobes of energy sit like a huge hourglass across the center of the Milky Way, stretching about 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 spotted 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 suggested they are the result of a giant explosion of a black hole that lasted more than 100,000 years, which began about 2.6 million years ago, when enormous amounts of matter flowed into the maw of our black hole. If confirmed, this hypothesis would suggest that our black hole was active much more recently than once thought.
The big question
While studying a peculiar spot of starlight known as Herbig-Haro 46/47, JWST discovered something even more mysterious in the distant background of his image: a deep space burst of hot gas perfectly shaped like a question mark.
It’s unclear what exactly the object is or how far away it is, but the reddish color in JWST images suggests the object is exceptionally old, its light stretching into increasingly redder wavelengths as it travels vast cosmic distances to reach us . It could be a galaxy, or perhaps multiple galaxies tearing each other apart during a chaotic merger, researchers told LiveScience’s sister site Space.com in 2023.
Whatever it may be, the cosmic question mark is just one of many puzzles introduced by JWST’s groundbreaking observations. Uncovering its identity may have to take a back seat to more pressing questions – such as: are we? completely wrong about our understanding of the universe?