In 1980, scientists Keith Taylor and Mike Scarrot were looking through the Siding Spring Observatory in Coonabarabran, New South Wales when they found an oddly shaped nebula. They named it the “Boomerang Nebula”, a fitting name because it sort of looks like a Boomerang, and because it was first observed in Australia.
Over time, scientists studying this object discovered something else: the Boomerang Nebula is actually the coldest place in the universe.
What is “Cold”?
To understand what we mean when we say, ‘the coldest place in the universe’, let’s talk about the concept of ‘cold’ in the first place. Despite the internet giving us free access to information and, thus, the basics of thermodynamics, many people are still unaware that ‘cold’ is not a form of energy.
In fact, what scientists mean when they say ‘cold’ is not the presence of “cold energy”, but rather, the absence of energy in and of itself. When we say ‘cold’ and ‘hot’, we really are just trying to communicate that a location or an object has a certain level of thermal energy, manifested as heat.
To put it simply: all things have thermal energy. When something has more thermal energy, whether latently or because it absorbed more thermal energy from an external source, that thing is considered to be hot. When something has less thermal energy, whether latently or because it managed to transfer its latent energy to an external source or place because of thermodynamic processes, natural or otherwise, then we can consider that thing to be cold.
These perceptions of hot and cold are still relatively subjective; however, we understand the concept of it as temperature. Temperature is the scientific way of putting objectivity into an otherwise natural phenomenon, and is integral in pretty much every scientific process, from creating superfoods to figuring out renewable energy sources.
Temperature as we understand it is measured in 3 different ways: Fahrenheit, Celsius (or Centigrade), and Kelvin. Fahrenheit was one of the very first temperature scales to be widely used around the world and was based on observations by physicist Daniel Gabriel Fahrenheit back in 1724.
However, world scientists wanted something a little simpler than Fahrenheit’s scale, which had seemingly arbitrary points of reference (32-degrees for the freezing point of water, 212-degrees for its boiling point), and so most of the world (except for the United States), developed the Centigrade scale, which worked on a 100-point system, with the freezing point of pure ice water at 0-degrees and its boiling point set at 100-degrees. The Centigrade scale was eventually renamed the Celsius scale in 1948 to honor physicist Anders Celsius.
But there was a problem: despite the accuracy of both the Fahrenheit scale and Centigrade scale in providing some sort of objectivity into what-could-be a subjectively perceived phenomenon, they were still based on an arbitrary point of reference. Both scales relied on the freezing and boiling points of water as their primary reference points because, at the time of the creation of these scales, it was the easiest matter to measure scientifically.
For the Fahrenheit scale, 0-degrees Fahrenheit was set as the boiling point of a brine solution using water, ice, and ammonium chloride, while the upper limit was set using Fahrenheit’s estimate of the human body temperature. The Centigrade scale, on the other hand, relied on the boiling and freezing points of pure water at sea level conditions.
For scientific purposes, however, scientists rely on the Kelvin scale, named after physicist William Thomson, 1st Baron of Kelvin. The Kelvin Scale is preferred by scientists because it takes away as much arbitrariness (like basing temperature on the properties of water) as possible and relies entirely on the Boltzmann Constant. A unit of Kelvin is defined as a change in thermodynamic temperature that results in a change in thermal energy. Using the Kelvin scale allows scientists to measure the temperature of objects and places without the lens of human subjectivity.
In short, the Kelvin scale represents the true temperature of things, a measurement of their thermal energy and an expression of the change of that thermal energy when it transfers from one thing or place to another.
The most important part of the Kelvin Scale, however, is its concept of Absolute Zero.
What Is Absolute Zero?
In physics, Absolute Zero is the lowest possible limit of thermodynamic temperature, a point in a matter or location wherein no more thermal energy can be derived from it. When something has reached Absolute Zero, solid matter is at its ground state, wherein it has its lowest possible internal energy. To date, scientists have been unable to actually bring anything or any place to Absolute Zero because it is impossible to completely remove latent kinetic energy.
That being said, scientists have been able to approach as close to Absolute Zero as possible, with the most recent man-made attempt at the Cold Atom Laboratory in the International Space Station back in 2017 creating extremely cold conditions to the tune of 10 picokelvin, or 0.0000000000010 K.
This wasn’t the coldest man-man attempt at getting close to Absolute Zero, however: the current world record, which was set in 1999 using nuclear adiabatic demagnetization, cryocoolers, dilution refrigerators, laser cooling, and other high-tech equipment and processes, is 100 picokelvins, or 0.0000000001 of a kelvin, or 1/10th Billion of a degree of a Kelvin. For reference, 1 Kelvin is equal to -272.15-degrees Celsius or -457.87-degrees Fahrenheit.
Scientists agree, though, that reaching Absolute Zero, or as close as possible to it, is impossible without the use of equipment, which begs the question:
Where is the Coldest Place in the Universe?
The coldest place in the universe is the Boomerang Nebula, an amalgamation of cosmic gases lying somewhere around 5,000 light-years away from Earth. The Boomerang Nebula is recorded to have a temperature of a brisk 1 Kelvin, or –457.87 degrees Fahrenheit / –272.15 degrees Celsius. It is the coldest, naturally-occurring location or object in the universe that we know of so far, and it is so cold that it is even colder than the background temperature of space itself, the latter hovering around a brisk 2.7 Kelvin, or –454.81 degrees Fahrenheit / –270.7 degrees Celsius.
In fact, scientists predict that the background glow from the Big Bang (i.e. the leftover energy from the beginning of the universe) is actually warmer than the nebula itself.
The Boomerang Nebula is around 3 trillion kilometers from end to end, which is around 21,000 times more than the distance between the Earth and the Sun. It derives its name from the fact that it looked lop-sided when it was first observed in 1980. However, in 2013, scientists using the highly advanced Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, were able to determine that the Boomerang Nebula is actually bow-tie shaped.
This bow-tie shape is important because it has helped scientists figure out why the Boomerang Nebula is so cold: the red giant star at the center of the nebula is dying, which means it is shedding off its outer layers as its inner core collapses, making the Boomerang Nebula a prime example of a Planetary Nebula.
The Bowtie or Hour-glass shape is being created by the central star, with the visible nebula, i.e. the grains of stardust being illuminated by the star itself, being shot out from opposing ends of the star as jets of matter. A large portion of this expelled matter is able to mask the middle portion of the star, like the infamous ‘black image’ of Blackhole-M87, which means that the only visible light that reaches Earth is coming from its polar ends, thus creating the bowtie or hour-glass shape. The expelled material travels through space at around 93 miles a second, with the farthest material reflecting light 3 trillion kilometers away forming the edges of the nebula, a journey that takes them around 3,500 earth years.
But scientists have been able to observe this before, and yet, the Boomerang Nebula was losing star mass 100 times faster than stars of its size, and about 100 billion times faster than our own Sun. So, what gives? In a 2017 article in The Astrophysics Journal, scientists led by NASA’s Jet Propulsion Lab Researcher Dr. Raghvendra Sahai proposed a fairly exciting theory: the Boomerang Nebula might be a binary star system.
Dr. Sahai’s team formulated this idea because of how fast the star is expelling matter, arguing that the extreme speeds, which have never been observed in stars of similar sizes and locales, are impossible without the gravitational interaction of a second, separate star.
The Boomerang Nebula, being the coldest place in the universe, makes the coldest places in our solar system seem balmy in comparison.
For example, the seventh planet from the Sun and one of our Solar System’s gas giants, Uranus is one of the coldest neighbors we have in our star system. Along with Neptune, Uranus falls under a planetary category called “Ice Giants”. Ice Giants are like Gas Giants except their temperatures are extremely low, with Uranus displaying the coldest temperature of any planet in the Solar System at –371-degrees Fahrenheit or –224-degrees Celsius, or a balmy 49 Kelvin. Scientists believe that Uranus’ unique atmosphere –made up of hydrogen, helium, and ice crystals made of water, ammonia, and methane –all contribute to the planet’s chilly atmosphere.
Meanwhile, the coldest moon in the Solar System is Triton, one of Neptune’s 13 moons. NASA’s Voyager 2 mission was able to observe Triton in 1989, with the craft recording a surface temperature of –391-degrees Fahrenheit, or –235-degrees Celsius, or a breezy 38 Kelvin. While Mars has clouds and is a prime location for terraforming, it, too, is too cold for human habitation, although it’s balmy compared to these other locales. In fact, Mars has more in common temperature-wise to the coldest places on Earth.
The title the coldest place on Earth, however, belongs to the Eastern Antarctic Plateau, which recorded an average temperature of –137-degrees Fahrenheit, –94-degrees Celsius, or a balmy 179 Kelvin. However, scientists believe that the Eastern Antarctic Plateau, which is an area of the Antarctic continent roughly the size of Australia, can actually see even colder temperatures because of climate change.
But Why is Finding the Coldest Place in the Universe Important?
Finding the coldest place in the universe is pretty important because it advances two, very important topics in astrophysics and thermodynamics: our understanding of planetary nebulas, and our understanding of the quantum effects when approaching Absolute Zero.
Similar to a star nursery, a planetary nebula is a cosmic object that consists of a bright, glowing shell made up of hot gases and plasma. This outer shell is usually formed when a particular type of star approaches the end of its natural lifetime. Despite the name, planetary nebulae actually have nothing to do with planets themselves; planetary nebulae get their name from the fact that they sort of look like giant, gaseous planets.
At a cosmic level, a planetary nebula is a short-lived phenomenon, with most planetary nebulae lasting for less than a hundred thousand years, a blink of an eye in the larger timespan of the universe. In the Milky Way galaxy alone, there are about 1,500 different planetary nebulae floating about, with more spotted in other, distant galaxies.
Other than being the coldest place in the Universe, the Boomerang Nebula has also been confirmed as a planetary nebula in the making, a proto-planetary nebula. Studying the Boomerang Nebula, both for its extreme temperature and for the process it’s undergoing are important in advancing our understanding of planetary nebulae.
But why are planetary nebulae so important? Well, scientists believe that planetary nebulae play a central part in the chemical evolution and composition of galaxies. Planetary nebulae act as interstellar mediums for various types of cosmic material, most of them enriched heavy elements and by-products of nucleosynthesis.
In fact, within a planetary nebula, scientists can observe not just exotic, cosmic matter, but more familiar elements like carbon, oxygen, calcium, and other elements we might find down here on Earth. This is crucial in helping us understand other galaxies, as the planetary nebula present in them are usually very good indicators of the type of matter and chemicals present in that particular galaxy. In short, Carl Sagan was right: we really are made of stardust.
Aside from being a sort-of cosmic indicator of what a galaxy is made up of, studying planetary nebulae, and in this case, studying the Boomerang Nebula, in particular, helps us advance another, very important, and very enigmatic scientific discipline: quantum physics.
All the branches of physics talk about the various aspects of nature at the macroscopic level. Our understanding of physics allows us to bring order into what might seem like a chaotic universe: physicists have created laws governing our understanding of thermodynamics, chemical reactions, gravitational waves, etc.
But that’s at the normal, macroscopic level. Once we enter the quantum realm, i.e. the atomic and subatomic levels, almost none of our general rules of physics apply. At the quantum level, particles appear and disappear without an explanation, waves travel backwards in time, and basically, atoms start behaving in new, exciting, and often unpredictable ways. If Physics tries to give order to a chaotic universe, quantum physics confirms that chaos.
So what’s the Boomerang Nebula have to do with it? Well, as it turns out, matter starts behaving oddly when it starts approaching Absolute Zero. In fact, it’s one of the few times that we can actually start seeing quantum effects at an almost macroscopic level.
Although it is 5,000 lightyears away and beyond our manipulation, the coldest place in the universe is where we can directly observe quantum effects above the microscopic level. Of these quantum effects, the Bose-Einstein Condensate is what piques the interest of scientists because it is what gives us a macroscopic, observable look into what happens when the laws of quantum physics are applied to the natural world.
A Bose-Einstein Condensate isn’t actually a thing, but rather, a state of matter (like solid, liquid, gas, and plasma) that can only be achieved when low-density boson gas is supercooled to near-Absolute Zero. First predicted by Satyendra Nath Bose and Albert Einstein in 1924, the Bose-Einstein Condensate wasn’t confirmed until much later in 1995, when scientists Eric Cornell and Carl Wieman were able to produce the first known instance of the Bose-Einstein Condensate in the University of Colorado at Boulder’s NIST-JILA Laboratory.
Matter that achieves the state of becoming a Bose-Einstein Condensate doesn’t behave in the same way as other types of matter do, which is what makes it so interesting to scientists. One of the ways a Bose-Einstein Condensate is special is its function in making Superconductivity and Superfluidity possible, two other functions of physics that can only be observed in extremely cold temperatures, like the ones achieved in a lab or in the coldest place in the universe, the Boomerang Nebula.
At its most basic, Superconductivity is a physical phenomenon wherein certain materials start to lose all of their electrical resistance as well as all magnetic flux fields, turning it into a superconductor. First observed in 1911 by Dutch scientist Heike Onnes, superconductivity’s properties are practically unexplainable by regular physics, which is why it’s one of the best experiments to perform when seeking to understand the basics of quantum mechanics.
Superfluidity, on the other hand, is another strange set of properties that are observed only under extremely cold conditions. Fluids that are exhibiting signs of superfluidity are able to move with zero viscosity, which means the fluid loses zero kinetic energy when flowing from one point to another. Superfluidity was first observed in 1937 by scientists Pyotr Kapitsa, John Allen, and Don Misener using a then-newly discovered Superfluid form of Helium-4.
The sum total of our knowledge about the universe and how it operates is so infinitesimally small that, despite high-tech equipment, billions of dollars of funding, and the brightest minds of human civilization working tirelessly for centuries, it can barely explain anything at all. But perhaps, by studying the coldest place in the Universe, we can unlock some of the Universe’s knowledge for future generations to study.