A space telescope that observes stars in the Milky Way as they appear today reveals what happened to the galaxy when it was just a couple of billion years old, and an upcoming data release will allow astronomers to peek into an even more distant past.
The European Space Agency’s Gaia mission is not a household name like the Hubble Space Telescope or the James Webb Space Telescope. Yet the mission currently produces the most scientific papers and, as Milky Way researchers would tell you, has enabled unprecedented leaps in our understanding of the galaxy’s history.
Gaia works differently than Webb or Hubble. Instead of observing the universe one fascinating distant object at a time, Gaia scans the whole sky over and over again. The flying-saucer-like telescope, nestled in Lagrange Point 2 some 930,000 miles (1.5 million kilometers) from Earth, observes 2 billion of the brightest stars in the sky, its view free from the distorting effects of Earth’s atmosphere that plague ground-based telescopes’ observations.
Unlike Hubble and Webb, Gaia doesn’t focus on capturing awe-inspiring images that reveal every detail of those distant stars and galaxies. Instead, the probe concentrates on a few basic parameters: the stars’ distance from Earth, the speed at which the stars move through space, and the direction of their motion as it appears on the plane of the sky and in three dimensions.
Because objects in space follow the laws of physics, scientists can model the trajectories of those stars billions of years into the past and future, unpicking the events that shaped the galaxy’s evolution. A discipline known as galactic archaeology has grown immensely since Gaia’s launch in 2013, and the new data release coming Monday (June 13) is set to supercharge the research.
“We are still trying to unravel the details of the Milky Way’s origins,” Anthony Brown, an astronomer at Leiden University in the Netherlands and chair of the Gaia Data Processing and Analysis Consortium, told Space.com. “With the new release, we should be able to do it even better, because we are getting some new data.”
Getting to know the stars
Those new data contain what astronomers call astrophysical parameters. Derived from the light spectra of the observed stars (essentially the fingerprints of how stars absorb light), the astrophysical parameters reveal ages, masses, brightness levels and, in some cases, detailed chemical compositions of the observed stars.
“You really get to know the stars,” Jos de Bruijne, Gaia project scientist at ESA, told Space.com. “It’s like you have an anonymous group of people and now you get to meet every one of them. You get to know their names and how old they are and where they came from.”
The group of stars that astronomers “get to meet” thanks to the June 13 data release consists of half a billion individual objects, one-quarter of the stars Gaia observes. This information will help astronomers refine the order of events that shaped the Milky Way and “really untangle its formation history,” Brown added.
What we already know
Astronomers think the Milky Way started forming only about 800 million years after the Big Bang and went through a 1 billion to 2 billion-year period of intense formation, Brown said. This formation period involved many collisions with other galaxies, which gradually built up the Milky Way into what we see today: a massive spiral galaxy encompassing 200 billion stars. (Gaia sees only about 1% of them.)
In the previously released Gaia data, researchers found imprints of those early collisions in the form of waves that still ripple through the galaxy, affecting the motion of stars. The most significant of these collisions was with a galaxy called Gaia Enceladus. That galaxy was about four times smaller than the Milky Way when the two crashed about 10 billion years ago. The collision, Gaia data revealed, gave rise to the Milky Way’s halo, the sphere of thinly dispersed stars enveloping the galaxy’s much more massive disk.
“At the moment, we think that [the collision with Gaia Enceladus] was the last significant merger that the Milky Way underwent,” Brown said.
Tracing the “smallest building blocks”
Among the astronomers awaiting the June 13 data release is Eduardo Balbinot, a postdoctoral researcher in astrophysics at the University of Groningen in the Netherlands. Balbinot is interested in more modest collisions with what he calls the “smallest building blocks” of the galaxy: globular clusters, ancient groupings of stars devoured by the Milky Way over the eons.
“[The globular clusters] are special, because when they dissolve in these accretion events, they’re torn apart,” Balbinot said. “But they continue living as coherent groups of stars in the sky as what we call stellar streams.”
These stellar streams have been notoriously hard to detect, but Balbinot thinks the new Gaia data will usher in a breakthrough in this endeavor.
“There will be an additional velocity component [in the new data set], the so-called radial velocity — how fast the stars move towards or away from us,” Balbinot said. “Gaia measured some of those before, but the new sample will be 10 times bigger. It’s bigger than anything before.”
In those motions of stars, astronomers will be able to distinguish groups of stars that move through the galaxy in sync. By combining this information with data about the chemical compositions of stars (stars that arrived from other galaxies have distinct chemical profiles), astronomers will be able to peek into the galaxy’s past like never before.
“That’s one of the exciting things that you can do with Gaia data,” Balbinot said. “You can find these groups of stars that move similarly and basically reconstruct from where they came from and which building block brought them into the Milky Way. Then, you can ultimately answer the question of how the Milky Way formed.”
What happens on the galaxy’s edge
Balbinot hopes the new data will enable astronomers to look for remnants of globular clusters much farther away from Earth than was possible before, in the very outskirts of the galaxy, where the galactic halo meets intergalactic space.
“The new data set will contain a small subset of data on variable stars, which are very bright, and because they are so bright, we can see them all the way to the edge of the Milky Way,” Balbinot said. “They are basically the most distant stars that we will ever be able to detect within our Milky Way galaxy. And that is really exciting, because it really is an uncharted territory.”
Balbinot said the variable stars might reveal leftovers from ancient collisions with globular clusters scattered across the galactic halo, in the form of spherical “shells.” Analysis of these shells can reveal a lot about the anatomy of the events that gave rise to them billions of years ago.
“There are many things you can infer if you measure the distance of these shells,” Balbinot said. “You can reconstruct how these accretion events happened in detail, what was the orbit of the satellite [galaxy] that fell into the Milky Way and so on.”
Looking into the future
The past few billions of years have been quite peaceful for the Milky Way. The galaxy has been churning out stars and seeing them die at a steady rate while still absorbing the aftershocks of the earlier shake-ups.
But things will get rough again in the future. In fact, astronomers already observe the approach of the next galactic collision: the smash-up with two dwarf galaxies in the Milky Way’s orbit called the Large Magellanic Cloud and the Small Magellanic Cloud.
“The Magellanic Clouds entered into orbit around the Milky Way fairly recently, in the past few billion years,” Brown said. “We already see them having an influence on the Milky Way’s gravitational force field, and if we reconstruct the past really well, we might be able to run the whole thing forward and see when the clouds will merge with the Milky Way.”
Despite the Milky Way’s violent childhood, the most cataclysmic event still lies ahead: the collision with the Andromeda galaxy, the nearest large galactic neighbor.
Andromeda, currently over 2.5 million light-years from Earth, is among the celestial objects Gaia observes. The new data release will provide new insight into the encounter that will rattle the two galaxies some 4.5 billion years from now.
With Gaia, “you can actually measure quite well the motion of the Andromeda galaxy across the line of sight,” Brown said. “That gives you more constraints on the long-term future of the two galaxies.”
The sun will be near the end of its life when its mother galaxy encounters Andromeda, so humankind is unlikely to still be around to witness the galactic smash. Earth, for certain, will have long been uninhabitable, scorched by the increasingly hotter sun.
Still, untangling the galaxy’s past and future is a fascinating project, one that is set to continue for quite a few years as Gaia produces more and more data.
The telescope will retire in 2025, when it runs out of fuel. But it certainly is not past its peak, De Bruijne said. The consortium of 400 researchers that processes Gaia data is still refining the algorithms used to analyze the vast quantities of measurements that the telescope produces. These algorithms enable astronomers to find finer and finer details and new types of information in the vast data set. The June 13 release will, for example, contain the largest-ever catalog of chemical compositions of asteroids in the solar system and the largest-ever data set of binary star systems. Gaia’s next data release is already set to reveal thousands of new exoplanets, De Bruijne said.
Rare ‘big fuzzy green ball’ comet visible in B.C. skies, a 50000-year sight
In the night sky, a comet is flying by Earth for the first time in 50,000 years.
Steve Coleopy, of the South Cariboo Astronomy Club, is offering some tips on how to see it before it disappears.
The green-coloured comet, named C/2022 E3 (ZTF), is not readily visible to the naked eye, although someone with good eyesight in really dark skies might be able to see it, he said. The only problem is it’s getting less visible by the day.
“Right now the comet is the closest to earth and is travelling rapidly away,” Coleopy said, noting it is easily seen through binoculars and small telescopes. “I have not been very successful in taking a picture of it yet, because it’s so faint, but will keep trying, weather permitting.”
At the moment, the comet is located between the bowl of the Big Dipper and the North Star but will be moving toward the Planet Mars – a steady orange-coloured point of light- in the night sky over the next couple of weeks, according to Coleopy.
“I have found it best to view the comet after 3:30 in the morning, after the moon sets,” he said. “It is still visible in binoculars even with the moon still up, but the view is more washed out because of the moonlight.”
He noted the comet looks like a “big fuzzy green ball,” as opposed to the bright pinpoint light of the stars.
“There’s not much of a tail, but if you can look through the binoculars for a short period of time, enough for your eyes to acclimatize to the image, it’s quite spectacular.”
To know its more precise location on a particular evening, an internet search will produce drawings and pictures of the comet with dates of where and when the comet will be in each daily location.
Coleopy notes the comet will only be visible for a few more weeks, and then it won’t return for about 50,000 years.
Extreme species deficit of nitrogen-converting microbes in European lakes
Sampling of Lake Constance water from 85 m depth, in which ammonia-oxidizing archaea make up as much as 40% of all microorganisms
An international team of researchers led by microbiologists from the Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH in Braunschweig, Germany, shows that in the depths of European lakes, the detoxification of ammonium is ensured by an extremely low biodiversity of archaea. The researchers recently published their findings in the prestigious international journal Science Advances. The team led by environmental microbiologists from the Leibniz Institute DSMZ has now shown that the species diversity of these archaea in lakes around the world ranges from 1 to 15 species. This is of particularly concern in the context of global biodiversity loss and the UN Biodiversity Conference held in Montreal, Canada, in December 2022. Lakes play an important role in providing freshwater for drinking, inland fisheries, and recreation. These ecosystem services would be at danger from ammonium enrichment. Ammonium is an essential component of agricultural fertilizers and contributes to its remarkable increase in environmental concentrations and the overall im-balance of the global nitrogen cycle. Nutrient-poor lakes with large water masses (such as Lake Constance and many other pre-alpine lakes) harbor enormously large populations of archaea, a unique class of microorganisms. In sediments and other low-oxygen environments, these archaea convert ammonium to nitrate, which is then converted to inert dinitrogen gas, an essential component of the air. In this way, they contribute to the detoxification of ammonium in the aquatic environment. In fact, the species predominant in European lakes is even clonal and shows low genetic microdiversity between different lakes. This low species diversity contrasts with marine ecosystems where this group of microorganisms predominates with much greater species richness, making the stability of ecosystem function provided by these nitrogen-converting archaea potentially vulnerable to environmental change.
Maintenance of drinking water quality
Although there is a lot of water on our planet, only 2.5% of it is fresh water. Since much of this fresh water is stored in glaciers and polar ice caps, only about 80% of it is even accessible to us humans. About 36% of drinking water in the European Union is obtained from surface waters. It is therefore crucial to understand how environmental processes such as microbial nitrification maintain this ecosystem service. The rate-determining phase of nitrification is the oxidation of ammonia, which prevents the accumulation of ammonium and converts it to nitrate via nitrite. In this way, ammonium is prevented from contaminating water sources and is necessary for its final conversion to the harmless dinitrogen gas. In this study, deep lakes on five different continents were investigated to assess the richness and evolutionary history of ammonia-oxidizing archaea. Organisms from marine habitats have traditionally colonized freshwater ecosystems. However, these archaea have had to make significant changes in their cell composition, possible only a few times during evolution, when they moved from marine habitats to freshwaters with much lower salt concentrations. The researchers identified this selection pressure as the major barrier to greater diversity of ammonia-oxidizing archaea colonizing freshwaters. The researchers were also able to determine when the few freshwater archaea first appeared. Ac-cording to the study, the dominant archaeal species in European lakes emerged only about 13 million years ago, which is quite consistent with the evolutionary history of the European lakes studied.
Slowed evolution of freshwater archaea
The major freshwater species in Europe changed relatively little over the 13 million years and spread almost clonally across Europe and Asia, which puzzled the researchers. Currently, there are not many examples of such an evolutionary break over such long time periods and over large intercontinental ranges. The authors suggest that the main factor slowing the rapid growth rates and associated evolutionary changes is the low temperatures (4 °C) at the bottom of the lakes studied. As a result, these archaea are restricted to a state of low genetic diversity. It is unclear how the extremely species-poor and evolutionarily static freshwater archaea will respond to changes induced by global climate warming and eutrophication of nearby agricultur-al lands, as the effects of climate change are more pronounced in freshwater than in marine habitats, which is associated with a loss of biodiversity.
Publication: Ngugi DK, Salcher MM, Andre A-S, Ghai R., Klotz F, Chiriac M-C, Ionescu D, Büsing P, Grossart H-S, Xing P, Priscu JC, Alymkulov S, Pester M. 2022. Postglacial adaptations enabled coloniza-tion and quasi-clonal dispersal of ammonia oxidizing archaea in modern European large lakes. Science Advances: https://www.science.org/doi/10.1126/sciadv.adc9392
PhDr. Sven-David Müller, Head of Public Relations, Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures GmbH
Phone: ++49 (0)531/2616-300
About the Leibniz Institute DSMZ
The Leibniz Institute DSMZ-German Collection of Microorganisms and Cell Cultures is the world’s most diverse collection of biological resources (bacteria, archaea, protists, yeasts, fungi, bacteriophages, plant viruses, genomic bacterial DNA as well as human and animal cell lines). Microorganisms and cell cultures are collected, investigated and archived at the DSMZ. As an institution of the Leibniz Association, the DSMZ with its extensive scientific services and biological resources has been a global partner for research, science and industry since 1969. The DSMZ was the first registered collection in Europe (Regulation (EU) No. 511/2014) and is certified according to the quality standard ISO 9001:2015. As a patent depository, it offers the only possibility in Germany to deposit biological material in accordance with the requirements of the Budapest Treaty. In addition to scientific services, research is the second pillar of the DSMZ. The institute, located on the Science Campus Braunschweig-Süd, accommodates more than 82,000 cultures and biomaterials and has around 200 employees. www.dsmz.de
Scientists are closing in on why the universe exists
Particle astrophysicist Benjamin Tam hopes his work will help us understand a question. A very big one.
“The big question that we are trying to answer with this research is how the universe was formed,” said Tam, who is finishing his PhD at Queen’s University.
“What is the origin of the universe?”
And to answer that question, he and dozens of fellow scientists and engineers are conducting a multi-million dollar experiment two kilometres below the surface of the Canadian Shield in a repurposed mine near Sudbury, Ontario.
The Sudbury Neutrino Observatory (SNOLAB) is already famous for an earlier experiment that revealed how neutrinos ‘oscillate’ between different versions of themselves as they travel here from the sun.
This finding proved a vital point: the mass of a neutrino cannot be zero. The experiment’s lead scientist, Arthur McDonald, shared the Nobel Prize in 2015 for this discovery.
The neutrino is commonly known as the ‘ghost particle.’ Trillions upon trillions of them emanate from the sun every second. To humans, they are imperceptible except through highly specialized detection technology that alerts us to their presence.
Neutrinos were first hypothesized in the early 20th century to explain why certain important physics equations consistently produced what looked like the wrong answers. In 1956, they were proven to exist.
Tam and his fellow researchers are now homing in on the biggest remaining mystery about these tiny particles.
Nobody knows what happens when two neutrinos collide. If it can be shown that they sometimes zap each other out of existence, scientists could conclude that a neutrino acts as its own ‘antiparticle’.
Such a conclusion would explain how an imbalance arose between matter and anti-matter, thus clarifying the current existence of all the matter in the universe.
It would also offer some relief to those hoping to describe the physical world using a model that does not imply none of us should be here.
Guests in this episode (in order of appearance):
Benjamin Tam is a PhD student in Particle Astrophysics at Queen’s University.
Eve Vavagiakis is a National Science Foundation Astronomy and Astrophysics Postdoctoral Fellow in the Physics Department at Cornell University. She’s the author of a children’s book, I’m A Neutrino: Tiny Particles in a Big Universe.
Erica Caden is a research scientist at SNOLAB. Among her duties she is the detector manager for SNO+, responsible for keeping things running day to day.
*This episode was produced by Nicola Luksic and Tom Howell. It is part of an on-going series, IDEAS from the Trenches, some stories are below.
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