A.I. Has Helped Humans Know the Family Tree of the Milky Way
Understanding the history of the Milky Way is part of understanding our own existence.
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I’m a big believer in A.I.’s ability to enable human civilization to become a multi-planetary species. I think artificial intelligence will be critical in enabling us to make this jump in the brief window afforded to us by time and history since the risks of human extinction will become greater in the decades and centuries ahead.
I’m always searching and on the hunt for big stories in how A.I. is shaping our understanding of the world and in terms of business innovation.
Sometimes however you have to look up. A.I. is taking on an increasingly larger role in space exploration, cosmology, astronomy and Earth-like planet discovery. I’m about to launch a Newsletter on Space, I’m so passionate about these topics.
My story goes back to November, 2020. So this is that research breakthrough enabled with the help of artificial intelligence:
Prepare to be inspired, because I know I am by this. I’m a huge fan of space science articles and I’m noticing A.I. is mentioned increasingly in our breakthroughs in understanding our place in the world as a species.
There is something majestic about the macro scale of human life, where even our personal troubles and suffering fade away feeling inconsequential compared to the fate of our species and all sentient and non-sentient life that exists. Could A.I.’s advancements continue in that direction?
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Establishing a Family Tree in the Cosmos
Scientists have known for some time that galaxies can grow by the merging of smaller galaxies, but the ancestry of our own Milky Way galaxy has been a long-standing mystery.
In late 2020, an international team of astrophysicists succeeded in reconstructing the first complete family tree of our home galaxy by analyzing the properties of globular clusters orbiting the Milky Way with artificial intelligence. The work is published in Monthly Notices of the Royal Astronomical Society.
It turns out, we come together quite literally to form our home among the stars.
Over the course of its history, the Milky Way cannibalised about five galaxies with more than 100 million stars, and about fifteen with at least 10 million stars.
This is beautiful and incredible and thanks to A.I. we understand it all better.
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The Families in Space
Globular clusters are dense groups of up to a million stars that are almost as old as the Universe itself.
The Milky Way hosts over 150 such clusters, many of which formed in the smaller galaxies that merged to form the galaxy that we live in today. Astronomers have suspected for decades that the old ages of globular clusters would mean that they could be used as “fossils” to reconstruct the early assembly histories of galaxies. However it is only with the latest models and observations that it has become possible to realize this promise.
Ultimate questions like “who we are” and “why we are here” can increasingly be understood in a scientific lens with the help of A.I. For me personally, advances in astronomy open up new questions and existential hopes for our species to continue among the stars. (I don’t know if this will be possible, but this hope must keep driving us forwards in technology, business and even space-technology).
In my Newsletter, Quantum Foundry where I currently focus on Quantum computing, I hope to cover A.I’s advances in things like space technology, 3-D printing and disruptive elements of technology and their impact on our future.
You’d be most welcome to check out that Newsletter here:
So let’s get into it:
Researchers use AI to create the Milky Way’s family tree
For those of us who pay special attention to history and the future as I do (where I call myself an amateur futurist, which is a catalyst for my writing), I find cosmology and our hunger for the stars among the most motivating things in life.
An international team of researchers led by Dr Diederik Kruijssen at the Center for Astronomy at the University of Heidelberg (ZAH) and Dr Joel Pfeffer at Liverpool John Moores University has now managed to infer the Milky Way’s merger history and reconstruct its family tree, using only its globular clusters.
If we are heroes in our own creation, the Milk Way is home, our center-point and understanding it also gives our own lives meaning.
To achieve this, they developed a suite of advanced computer simulations of the formation of Milky Way-like galaxies. Their simulations, called E-MOSAICS, are unique because they include a complete model for the formation, evolution, and destruction of globular clusters.
These are the first simulations to self-consistently model the formation and evolution of the entire star cluster population and their host galaxy through cosmic history in fully cosmological, hydrodynamical simulations of galaxy formation.
The project currently includes zoom-in simulations of Milky Way-like galaxies, and will soon be extended to galaxy groups and massive galaxy clusters. The primary goal of the project is to test whether models based on the formation and evolution of young stellar clusters can describe the populations of globular clusters observed around galaxies today.
In the simulations, the researchers were able to relate the ages, chemical compositions, and orbital motions of globular clusters to the properties of the progenitor galaxies in which they formed, more than 10 billion years ago. By applying these insights to groups of globular clusters in the Milky Way, they could not only determine how many stars these progenitor galaxies contained, but also when they merged into the Milky Way.
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“The main challenge of connecting the properties of globular clusters to the merger history of their host galaxy has always been that galaxy assembly is an extremely messy process, during which the orbits of the globular clusters are completely reshuffled,” Kruijssen explains.
Mapping the Milky Way with A.I.
“To make sense of the complex system that is left today, we therefore decided to use artificial intelligence. We trained an artificial neural network on the E-MOSAICS simulations to relate the globular cluster properties to the host galaxy merger history. We tested the algorithm tens of thousands of times on the simulations and were amazed at how accurately it was able to reconstruct the merger histories of the simulated galaxies, using only their globular cluster populations.”
I believe Quantum computing enabled simulations will vastly improve our knowledge of the history of the Big Bang and everything that came after it with the help of the James Webb Space Telescope in the coming years and decades.
Establishing the Merger History of the Milky Way
Inspired by this success, the researchers set out to decipher the merger history of the Milky Way. To achieve this, they used groups of globular clusters that are each thought to have formed in the same progenitor galaxy based on their orbital motion.
By applying the neural network to these groups of globular clusters, the researchers could not only predict the stellar masses and merger times of the progenitor galaxies to high precision, but it also revealed a previously unknown collision between the Milky Way and an enigmatic galaxy, which the researchers named “Kraken”.
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Milky Way and “Kraken”
Incredibly they discovered something big. Just as people split into three groups way earlier than we once believed, history informs our future.
“The collision with Kraken must have been the most significant merger the Milky Way ever experienced,” Kruijssen adds. “Before, it was thought that a collision with the Gaia-Enceladus-Sausage galaxy, which took place some 9 billion years ago, was the biggest collision event.
Charting Marriages in the Stars with A.I.
However, the merger with Kraken took place 11 billion years ago, when the Milky Way was four times less massive. As a result, the collision with Kraken must have truly transformed what the Milky Way looked like at the time.”
Taken together, these findings allowed the team of researchers to reconstruct the first complete merger tree of our Galaxy. Over the course of its history, the Milky Way cannibalized about five galaxies with more than 100 million stars, and about fifteen with at least 10 million stars. The most massive progenitor galaxies collided with the Milky Way between 6 and 11 billion years ago.
The Milky Way grew in time, merging with multiple other Galaxies
The researchers expect their predictions to stimulate future studies to search for the remains of these progenitor galaxies. “The debris of more than five progenitor galaxies has now been identified. With current and upcoming telescopes, it should be possible to find them all,” Kruijssen concludes.
Diederik Kruijssen’s current research interests include the formation of planets, stars, globular clusters, and galaxies, from high redshift until the present day, as well as galactic archaeology, using a combination of observational, theoretical, and numerical techniques.
It’s hard to say without A.I. if his research would have ever unlocked some of the mysteries of how the Milky Way came to become so massive.
The story of A.I. isn’t just about smart machines or business algorithms, but an extension of our humanity itself and our knowledge of sciences and the universe. Besides A.I.’s impact on healthcare, I consider A.I’s impact on space and space-technologies to be the ultimate A.I. for good story.
Astronomers at Heidelberg University in Germany – led by Diederik Kruijssen – announced in late November 2020 that they’ve been able to piece together more of the history of our galaxy, to the point of constructing a Milky Way family tree. This may be one of the most important discoveries with A.I. ever that most people know nothing about.
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