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IT is easy to feel like we know nothing about our universe, and unexplained stellar objects are the most puzzling feature of all.
It is easy to blame advanced alien civilizations for causing stars to fade and galaxies to bend, but do these arguments hold any weight?
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As it turns out, anything is possible – and despite technological advancements, some mysteries remain unsolved today.
A ninth planet
Researchers have uncovered evidence of a hefty planet tracing a bizarre orbit through the outer solar system.
The object, dubbed Planet Nine or Planet X, is around 10 times more massive than Earth and orbits 20 times farther from the Sun than Neptune.
In fact, it would take the planet between 10,000 and 20,000 to complete one full trip around the Sun.
But it is worth noting that Planet Nine’s existence was determined existence through mathematical modeling.
A proposal appeared in a 2016 edition of the Astronomical Journal, but the distant object has yet to be observed directly.
However, the two Caltech astronomers who authored the paper believe Planet Nine’s presence could explain the behavior of several small objects beyond Neptune.
They looked to the Kuiper Belt, a ring-shaped region of icy objects including Pluto and most of the dwarf planets.
One of them, Sedna, was discovered in 2003 and immediately caught scientists’ attention due to its unique orbit.
Unlike most Kuiper Belt objects, which get gravitationally expelled by Neptune before returning, Sedna never draws very close to Neptune. The same goes for a second object called 2012 VP113.
Researchers say Planet Nine would produce Sedna-like objects by pulling them away into an orbit less connected to Neptune.
“The possibility of a new planet is certainly an exciting one for me as a planetary scientist and for all of us,” said Jim Green, director of Nasa’s Planetary Science Division.
However, Green held off on declaring the finding a discovery.
“What we’re seeing is an early prediction based on modeling from limited observations,” he explained. “It’s the start of a process that could lead to an exciting result.”
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An interstellar cigar
ʻOumuamua – or “a messenger from afar arriving first” – was the first interstellar object observed passing through the solar system.
Formally deemed 1I/2017 U1, it was observed through Hawaii’s Pan-STARRS telescope in October 2017, a little over a month after it passed its closest point to the Sun.
When it was first spotted, ʻOumuamua was about 21 million miles from Earth – that’s 85 times as far away as the Moon.
The mysterious object evaded detection by the Spitzer Space Telescope in November, more than two months after its closest pass to Earth.
A 2018 paper proposed that a process known as outgassing was responsible for changes in ‘Oumuamua’s speed and direction.
The authors determined that the object expelled gas, which gingerly pushed it through space. This conclusion also suggested that ‘Oumuamua was composed of frozen vapors, like a comet.
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Observations through ground-based telescopes and Nasa’s Hubble Space Telescope detected the reflection of sunlight off ‘Oumuamua’s surface.
Notable variations in its brightness suggested that the cigar-shaped object was elongated and likely less than half a mile in its longest dimension.
Spitzer tracks asteroids and comets using the infrared energy that they radiate. This kind of data can provide more specific information about an object’s size than optical observations of reflected light.
Researchers believe ‘Oumuamua had been traveling through interstellar space for millions of years before passing by the Sun and “refreshing” its surface in the process.
In addition to clearing away grime, some of the released gas may have covered the object’s surface with a shiny coat of ice.
However, most of what we know about ‘Oumuamua is theory, and it will likely remain that way.
The mysterious visitor is rapidly departing our solar system and is well beyond the watchful gaze of any telescopes.
“Usually, if we get a measurement from a comet that’s kind of weird, we go back and measure it again until we understand what we’re seeing,” said Davide Farnocchia, a navigation engineer at Nasa‘s Jet Propulsion Laboratory.
“But this one is gone forever; we probably know as much about it as we’re ever going to know.”
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A rectangular nebula
Gas clouds can take on unconventional shapes throughout the galaxy, but rarely geometric
Nasa‘s Hubble Telescope captured striking images of a red rectangular cloud in 2016, aptly dubbed the Red Rectangle Nebula.
However, this was not the first time the structure became known to scientists. It was first discovered during a rocket flight in the 1970s as astronomers searched for strong sources of infrared radiation.
The Red Rectangle is located 2,300 light years away in the constellation Monoceros. At its heart sits a dying star formally designated HD 44179.
This star was once similar to our own Sun, but it began shedding its outer layers more than 14,000 years ago, creating a visible nebula.
Over the course of a few thousand years, the star will grow smaller and hotter, eventually becoming a white dwarf.
At the end of its life, HD 44179 will release a flood of ultraviolet light into the nebula, causing the gas to glow and producing a so-called planetary nebula.
Images from Hubble demonstrated that the Red Rectangle was X-shaped, rather than rectangular – the product of gas and dust flowing from the central star.
Astronomers believe these outflows are ejected in opposing directions, producing a shape that mimics two cones touching at their tips.
They also detected rung-like features that make the Red Rectangle look like a spider web, unlike any other known nebula.
These rungs may have arisen every few hundred years, in episodes of mass ejection from the star.
HD 44179 is still so cool that atoms in the surrounding gas do not glow. The particles can only be seen because they reflect the star’s light.
There are other molecules mixed in with the dust that emit light in the red portion of the spectrum.
Astronomers are not yet certain which types of molecules are producing the nebula’s signature red color, but suspect they are hydrocarbons formed in the outflow.
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An invisible galaxy
Astronomers have historically discovered new objects by detecting their effects on neighboring celestial bodies.
In 2015, a team at the Rochester Institute of Technology presented observational evidence of a dark dwarf galaxy orbiting the Milky Way.
The galaxy was first implicated in 2009 when scientists spotted odd ripples in the Milky Way’s atomic hydrogen disk.
Like Planet Nine, scientists have yet to observe it directly, meaning Galaxy X – as it is dubbed in popular media – is less fact than fiction.
Galaxy X’s existence is based on the discovery of four Cepheid variable stars, whose brightness changes notably over time.
Their periods of variation are closely related to the stars’ energy output, which makes them valuable benchmarks while measuring distances in space.
According to the researchers, the Cepeid variables’ “highly clustered nature” suggests that they may be associated with a dwarf galaxy.
Beyond these findings, we know very little.
The galaxy would be composed almost entirely of dark matter, a hypothetical form of matter that emits no light or energy.
Its mass was calculated to be one-hundredth the mass of the Milky Way, making it the third-heaviest satellite in the galaxy.
If Galaxy X does exist, it would have interacted with the Milky Way some 600 million years ago and is now crawling away from us.
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A fading star
There is no shortage of speculation about alien technology, and otherworldly neighbors have been implicated in the mysterious dimming of a distant star.
Tabby’s Star, located around 1,500 light years from Earth in the constellation Cygnus, is named for the astronomer Tabetha Boyajian.
Boyajian spearheaded a 2015 study that showed reductions in the star’s brightness, or radiative flux, by up to 22%.
The star’s overall brightness has also seemed to fade over several decades.
The short-term variation was detected by the Kepler Space Telescope, and scientists have been left scratching their heads.
They quickly ruled out planets passing in front of the star, seeing as no planet would be large enough to block that much light.
Even an enormous planet like a super-Saturn would cause predictable, periodic dips in brightness.
One theory suggests that trails of comets are plunging into the inner regions of the star’s solar system, kicking up dust.
The uneven distribution dust that might be occluding some of the star’s light, causing the rapid dimming.
However, this theory doesn’t explain the other pattern of long-term dimming over decades, seeing as comet dust dissipates over the span of months.
More outlandish theories suggest the dimming is caused by megastructures built by advanced alien civilizations to harvest the star’s energy.
However, this is also unlikely, as the technology would be completely opaque and block light from passing through.
Over the years, a new theory emerged, this one also implicating dust.
Observations have shown more light is blocked at the blue end of the spectrum than the red end.
Blue light has a shorter wavelength, so this is to be expected if the light was scattered by small dust grains. However, analysis of the longer-term dimming implicates bigger dust grains.
Scientists believe the culprit could be a cloud of different-sized dust particles blocking varying amounts of light as its orientation changes over time.
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A galaxy within a galaxy
Galaxies can take many forms, from spirals to ellipticals, but one is unparalleled.
Hoag’s Object lies around 600 million light years away, toward the Snake constellation.
The nearly perfect ring of blue stars girds a glowing yellow ball, with the whole thing stretching about 100,000 light years.
But its strangest attribute is a small object that can be observed in the gap at the one o’clock position – a tiny clone of Hoag’s Object itself.
The strange object was first spotted in 1950 by astronomer Arthur Hoag, who was unsure if he was looking at one galaxy or two.
While our understanding has progressed, to this day, scientists can’t say for sure what causes its unusual shape.
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The trademark blue ring is filled with clusters of huge, young stars that contrast sharply with the yellow nucleus, mostly composed of older stars.
While a gap appears to separate the two stellar populations, astronomers say this seemingly empty space may contain star clusters that are too faint to detect.
Nasa says this smaller mirror image is likely another ring galaxy that lies far in the distance, dubbed a background ring galaxy.
Circular galaxies like Hoag’s Object can form in several different ways, including through a run-in with another galaxy.
The blue stars may be the mangled remains of a galaxy that passed nearby some 2 to 3 billion years ago.
However, while this theory seems feasible, it leaves us with even more questions.
Such a collision would have sped up the core of Hoag’s Object – but observations show that it rotates slowly.
What is the Hubble Space Telescope?
Here’s what you need to know…
- The Hubble Space Telescope is a telescope that captures images while in space
- It was launched into a low-Earth orbit in 1990 and is still fully operational
- The advantage of Hubble is that it takes photos from outside of Earth’s atmosphere
- This means distortion from the atmosphere is removed, allowing for more accurate image capture
- Nasa’s Hubble has captured some of most detailed images of space ever recorded
- The Hubble telescope was also able to accurately determine the rate at which the universe was expanding
- Hubble is also the only telescope that was designed to be serviced by astronauts in space
- Five different missions have been launched to repair, upgrade or replace parts of the Hubble telescope
- It’s believed that the Hubble telescope could continue working until 2040
- But its successor – the James Webb Space Telescope – already launched in December 2021
