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.”
Trajectories of stars in the Milky Way galaxy over the next 400,000 years based on measurements by the European Gaia mission. (Image credit: ESA/Gaia/DPAC)
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.
The Milky Way is devouring small galaxies in its orbit. (Image credit: ESA/Gaia/DPAC)
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.
(Image credit: ESA)
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.
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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.
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
