Buzz
The Atacama Large Millimeter/submillimeter Array (ALMA), the world’s most formidable radio telescope network, is located on the Chajnantor plateau in northern Chile. Positioned 5,000 meters (16,500 ft) above sea level, it rises higher than the densest layers of Earth’s atmosphere.
These telescopes unlock the ability to interpret wavelengths beyond visible light, uncovering colors and light beyond the reach of the human eye. But ALMA, which translates to 'soul', also acts as a time machine. It peers back into the universe’s past, validating scientific theories of its formation over 13 billion years ago. At the same time, it thrusts us into the future as we explore new worlds and search for alien life that inhabits them.
10. The Molecule of Life
In the massive gas cloud Sagittarius B2, located near the heart of our galaxy, ALMA has made a groundbreaking discovery. For the first time in interstellar space, a hydrogen-rich, carbon-containing molecule, essential to life on Earth, has been identified. This finding suggests that molecules like these could have arrived on Earth in the distant past, possibly sparking the origins of life. It also raises the possibility that carbon-based alien life might exist elsewhere in the cosmos.
Molecular clouds like Sagittarius B2 are often referred to as 'stellar nurseries' because their dense concentrations of gas and dust are ideal for star formation. Until now, all organic molecules discovered in interstellar space have consisted of a simple chain of carbon atoms. But ALMA has found something new in Sagittarius B2: iso-propyl cyanide, a molecule with a branched carbon structure similar to that found in amino acids. These amino acids are crucial for building proteins, the essential components of life on Earth.
This discovery suggests that the fundamental building blocks for life as we know it are formed during star creation, long before planets like Earth come into being. Iso-propyl cyanide was abundant in Sagittarius B2, meaning that branched molecules may be widespread throughout interstellar space. Astronomers are now hopeful that amino acids will also be found there.
9. The Colliding Galaxies
Galactic collisions are surprisingly common. However, the stars and solar systems within these galaxies don’t actually crash into each other. Instead, the galaxies pass through one another like specters, as their stars are simply too far apart to physically collide.
While these mergers trigger a rapid creation of new stars and intense gravitational turmoil, it was once thought that the resulting chaos would obliterate the original structure of the galaxies, replacing them with a single massive elliptical galaxy, shaped like an American football. This outcome was expected even if both galaxies started as disk-shaped, like our own Milky Way, with their flattened, circular regions of gas and dust.
This idea has been the accepted theory since the 1970s, when computer simulations were first conducted. However, more recent simulations have challenged this view, suggesting that some galactic mergers might instead produce disk galaxies. Yet, there was no concrete evidence to confirm either theory.
Now, ALMA and other radio telescopes have provided the definitive evidence, observing 24 galaxies that have merged to form disk galaxies. This represents 65 percent of the 37 galaxies studied by an international team led by Junko Ueda from the Japan Society for the Promotion of Science.
As Ueda mentioned, 'We know that most galaxies in the distant universe also possess disk shapes. However, we’re still unsure whether these galaxy mergers are responsible for their formation, or if they form from cold gas gradually accumulating within the galaxy. Perhaps we’ve discovered a universal process that applies across the history of the universe.'
8. The Unusual Orbits of Exoplanets: Eccentric and Inclined
Some exoplanets, planets located outside our solar system, have orbits that are either highly stretched into an oval shape (an 'eccentric' orbit) or tilted at a sharp angle compared to their star’s equator (an 'inclined' orbit). To understand why this occurs in binary star systems, where two stars orbit each other, scientists used ALMA to study HK Tauri, a young binary system found in the Taurus constellation.
To grasp what ALMA does, it's helpful to understand the process of star and planet formation. When a cloud of interstellar gas collapses under the force of its own gravity, it spins faster and flattens into a disk. At the center of this disk, a protostar forms, much like an embryo in the womb. Once the temperature in the protostar’s core rises high enough to trigger nuclear reactions, a new star is born. About 90 percent of the time, the leftover gas and dust rotate around the newborn star in a protoplanetary disk. This material may eventually clump together to form planets, moons, and other celestial objects.
In a binary system, if the two stars and their protoplanetary disks do not orbit on the same plane (meaning they’re ‘misaligned‘), new planets can form with highly eccentric or inclined orbits. One theory, known as the Kozai mechanism, suggests that the gravitational pull from a second star can cause the planets of the first star to have these unusual orbits.
ALMA confirmed this theory using HK Tauri. The dimmer star, HK Tauri B, has a protoplanetary disk that blocks the star’s light, making the disk visible in optical light. However, the protoplanetary disk of HK Tauri A is tilted in such a way that the intense light from its star obscures the disk from view in visible light. ALMA detected both disks with ease in millimeter-wavelength light, revealing that they are misaligned by at least 60 degrees. This shows that at least one of the disks does not lie on the same plane as the stars’ orbits.
While this doesn’t account for every odd exoplanet orbit out there, it does suggest that the conditions for skewed orbits may arise when a planet forms within a binary system.
7. The Pathways to Planet Formation
In the multi-star system GG Tau-A, located in the Taurus constellation, ALMA has observed a flow of gas and dust moving like a stream. This stream travels from a vast outer disk encircling the entire star system to a smaller inner disk surrounding just the central star. It resembles a wheel within a wheel.
Before ALMA’s discovery, scientists had known about the inner disk but couldn’t explain its survival. The central star was draining material from the disk so quickly that it should have vanished long ago. ALMA, however, revealed a never-before-seen phenomenon: clumps of gas between the two disks acting as a lifeline, transferring material from the outer disk to sustain the inner one. This process allows the inner disk to persist much longer, providing a better opportunity for the formation of planets that could orbit the central star.
If other multi-star systems also possess these lifeline structures that nourish protoplanetary disks, we may have more locations to search for exoplanets—and possibly alien life—in the future.
6. The Boomerang Nebula
Located 5,000 light-years from Earth, the Boomerang Nebula in the Centaurus constellation holds the record for the coldest known object in the universe. With a temperature of just 1 Kelvin, it’s the equivalent of –272 degrees Celsius (–458 °F). This is even colder than the cosmic microwave background, which, at 2.8 Kelvin, represents the natural temperature of space.
Scientists used ALMA to study the Boomerang Nebula’s extreme cold and, in doing so, uncovered its true shape. Earlier optical images showed the nebula as a bowtie with two overlapping boomerangs. But ALMA, capable of detecting wavelengths of light obscured by a thick dust cloud surrounding the nebula’s star, revealed a much wider and rapidly expanding nebula.
The reason for the Boomerang Nebula’s chilling temperatures was also uncovered. Its central star is dying, causing a rapid expulsion of gas that cools the nebula much like the process that cools a refrigerator. As the gas begins to slow its expansion, the nebula’s outer shell is gradually warming. 'This discovery is vital for understanding how stars die and transform into planetary nebulae,' says Raghvendra Sahai from NASA’s Jet Propulsion Laboratory. 'With ALMA, we were able to shed new light—both literally and figuratively—on the final stages of a Sun-like star’s life.'
5. The Space Blob
This discovery from ALMA is thrilling not only because of what the telescopes didn’t capture, but also for what they did observe.
In 2009, astronomers identified a glowing, hot gas bubble extending more than 55,000 light-years across. They named it 'Himiko', after a legendary Japanese queen. Positioned nearly 13 billion light-years from Earth, and accounting for the time it takes for light to travel, scientists were observing Himiko as it appeared when the universe was just 6 percent of its current size. It seemed far too enormous and powerful for its time period.
By using both the Hubble Space Telescope and ALMA, astronomers have started to piece together part of the mystery. Hubble revealed that Himiko consists of three distinct stellar clumps, each comparable in size to a typical luminous galaxy from that era. These clumps are forming stars at a staggering rate of about 100 solar masses per year. As Richard Ellis from the California Institute of Technology explains, 'This incredibly rare triple system, observed when the universe was just 800 million years old, provides valuable insights into the early stages of galaxy formation during a period known as Cosmic Dawn, when the universe was first illuminated by starlight. Even more fascinating, these galaxies seem on the brink of merging into one massive galaxy, which could eventually evolve into something like our Milky Way.'
However, this is where the mystery deepens. In regions with such intense star formation, we would expect the creation of dust clouds containing heavy elements like carbon, oxygen, and silicon. These elements, when heated by starlight, emit radio wavelengths that ALMA is capable of detecting. Yet, ALMA found no significant radio emissions. It also failed to detect gaseous carbon, which is usually tied to vigorous star formation.
Instead, astronomers suspect that the interstellar gas within Himiko is primarily composed of hydrogen and helium. This suggests that we are witnessing the formation of a primordial galaxy, likely just after the big bang.
4. The Supernova Dust Factory
Dust is essential for our very existence. It plays a pivotal role in the formation of stars and planets. While it's known that the universe is filled with dust, scientists have long been uncertain about how this dust originated in the early universe.
Today, most of the dust in the universe originates from stars of all sizes as they die. However, in the early universe, only the most massive stars had exploded as supernovae. While this contributed some dust, it seemed insufficient to explain the vast amounts of dust seen in distant, young galaxies. The answer to this puzzle came when astronomers examined the remnants of Supernova 1987A using ALMA, uncovering the mystery behind the missing early dust.
Supernova 1987A, or SN 1987A, exploded in 1987, located about 168,000 light-years from Earth. Scientists had expected to observe substantial dust formation as carbon, oxygen, and silicon atoms bonded into molecules within the cooling gas from the explosion. Earlier telescopes detected only small amounts of hot dust. But with ALMA's capabilities, astronomers were able to detect a massive dust cloud with a mass equivalent to 25 percent of our sun. ALMA’s sensitivity to millimeter and submillimeter wavelengths allowed it to reveal the abundant cold dust, solving the puzzle.
"The earliest galaxies were incredibly dusty, and this dust played a major role in their evolution," says Mikako Matsuuro from University College London. "Today, we understand that dust can form in various ways, but in the early universe, much of it must have been produced by supernovae. We now have direct evidence that supports this theory."
3. The Birth Of A Solar System
In early November 2014, ALMA captured the first detailed images of planets forming within a protoplanetary disk around a young Sun-like star, HL Tau, located in the Taurus constellation about 450 light-years from Earth. This remarkable image not only reveals the birth of a new solar system but also offers insight into the possible origins of our own solar system more than four billion years ago.
HL Tau is obscured by a massive cloud of gas and dust in visible light. However, ALMA's ability to observe at much longer wavelengths allowed it to peer through the dust and examine the core of the cloud, where planet formation is actively occurring. This new image provided significant confirmation of several scientific theories regarding how planets form.
ALMA also provided astronomers with an unexpected finding. HL Tau was believed to be too young for large planetary bodies to be forming around it. However, ALMA’s observations revealed distinct concentric rings within the protoplanetary disk. These rings form as planets grow larger, creating gaps where the planets orbit their young star, pushing debris aside.
At least eight planets seem to be forming, with each planet corresponding to one of the concentric rings. ALMA scientist Catherine Vlahakis put it succinctly: “This one image alone will revolutionize theories of planet formation.”
2. The Event Horizon Telescope
In mid-2014, scientists set up an exceptionally precise atomic clock at ALMA’s Array Operations Site to synchronize it with a global network of radio telescopes. This was a key part of building the Event Horizon Telescope (EHT), a singular Earth-sized instrument. “By uniting the most advanced millimeter and submillimeter wavelength radio dishes worldwide, the Event Horizon Telescope creates an entirely new instrument with the most powerful magnification ever achieved,” explained Shep Doeleman of the MIT Haystack Observatory. “Supported by ALMA, the EHT will offer a fresh perspective on black hole research and focus on one of the universe’s only places where Einstein’s theories may break down: the event horizon.”
The event horizon is a theoretical boundary encircling a black hole, marking the point of no return, where nothing—light included—can escape the hole’s intense gravitational pull. Scientists are aiming to use the EHT to determine if an event horizon truly exists around the supermassive black hole at the heart of our Milky Way galaxy. This black hole, known as Sagittarius A*, is thought to contain the mass of about four million suns in an incredibly compact region.
To further examine Einstein’s general theory of relativity, the EHT will also focus on Sagittarius A* for any signs of a shadow— a darkened zone where the black hole has absorbed light. The shape and size of this shadow, influenced by Sagittarius A*’s spin and mass, could provide crucial insights into how space and time warp in the vicinity of such a powerful gravitational force.
Astronomers are also keen to observe the interaction between Sagittarius A* and G2, a colossal cloud of gas and dust, to understand the effect of this collision on both the black hole and our galaxy. This event will span over a year.
1. The Orion Death Star
Within the bustling stellar nursery of the Orion Nebula, planet-destroyers are hiding in plain sight.
As discussed earlier, vast molecular clouds composed of gas and dust, like those found in the nebula, create ideal conditions for stars and eventually planets to form. However, there are also older O-type stars in the Orion Nebula that are significantly larger than our sun and possess surface temperatures exceeding 50,000 Kelvin. These O-stars have the power to both nurture and obliterate planetary systems nearby. When these massive, short-lived stars reach the end of their life cycle and explode as supernovae, they generate clouds of gas and dust that may lead to the birth of new stars and planets. But during their lifetimes, these O-stars can destroy protoplanetary disks if young, forming solar systems come too close.
Thanks to ALMA’s capability to peer through dust, astronomers have doubled the number of known protoplanetary disks in the Orion Nebula. The data reveals that when young stars approach within one-tenth of a light-year of an O-star, the intense ultraviolet radiation emitted by these stars will strip away the young star’s protoplanetary disk, preventing planets from forming. This powerful radiation often deforms the affected young stars, giving them the shape of teardrops.
