Is there a particular galaxy cataloged by astronomers which is considered to most closely resemble what the structure of the Milky Way is believed to look like, when viewed from a similar distance?
According to this article on space.com the most similar looking galaxy to our own is NGC 6744. The source of this article comes from a statement by the ESO (European Southern Observatory) which says:
If we had the technology to escape the Milky Way and could look down on it from intergalactic space, this view is close to the one we would see - striking spiral arms wrapping around a dense, elongated nucleus and a dusty disc.
There is even a distorted companion galaxy - NGC 6744A, seen here as a smudge to the lower right of NGC 6744, which is reminiscent of one of the Milky Way's neighboring Magellanic Clouds
Included below is an image of the galaxy (NGC 6744) in question, taken with the Wide Field Imager on the MPG/ESO 2.2-meter telescope.
However it is also noted that while the Milky Way and NGC 6744 are similar in appearance, NGC 6744 is almost twice the diameter of the Milky Way.
Astronomers unveil most detailed map of the Milky Way to date
Astronomers have unveiled the most detailed map to date of the Milky Way, after charting the positions of more than 1bn stars with stunning precision.
The map, based on observations from the European Space Agency’s Gaia probe, still only represents about 1% of the Milky Way’s stars, but is already 20 times more complete than any previous observations of the night sky.
Speaking at a briefing in London on Wednesday, Gerry Gilmore, the mission’s UK principle investigator, said that the mission was already transforming what we know about our home galaxy. “We don’t actually know what the Milky Way looks like,” he said. “It’s astonishingly difficult, when you’re inside something, to find out what it looks like.”
The robotic Gaia spacecraft, which launched in 2013, is fitted with a 1bn pixel camera – the largest ever in space – complete with more than 100 electronic detectors. The precision of the measurements is equivalent to measuring the width of your fingernail – but if you were in London and your finger was in Australia.
The observations have already hinted at scientific discoveries that may lie ahead - including the possibility that the Milky Way may contain more stars than the current estimate of 100bn.
Scientists originally calculated that Gaia would see about 1bn stars by the end of 2017, but this number has now been revised upwards.
A slide show depicting a representation of the ESA Gaia Project. Photograph: Daniel Ochoa de Olza/AP
Floor van Leeuwen, of the University of Cambridge, who manages Gaia’s data processing, said: “It looks very much like we underestimated the number of stars. We think we will see 2-2.5bn stars.”
However, he added that it is not obvious how this relates to the number of stars in the entire galaxy.
The camera has now made observations of the precise position and brightness of more than 1.1bn stars. Astronomers are steadily converting the data into a 3D map of the galaxy - in effect, a cosmic version of Google maps.
“Every mission to come will use this map,” said Gilmore, adding that it would also help direct ground telescopes towards objects of interest in the cosmos.
The Gaia observatory, which has mapped the precise position and brightness of more than a billion stars in the Milky Way Photograph: ESA/ATG medialab background: ES/PA
By scanning each star about 70 times, astronomers have also calculated the sideways motion of 2m stars, showing how they drift and “wobble” in the night sky. This motion information will be crucial to building up a picture of the mass distribution in the galaxy – in particular the nature of the halo of dark matter that scientists believe surrounds the visible disk of the galaxy.
“We don’t know how massive the dark matter halo is and we will know that very much more accurately,” said Gilmore. “Knowing the velocities of objects far out in the galaxy will help determine that. That will be a complete revolution.”
Gaia astronomers will also be able to spot which stars have planets, by observing the characteristic wobble of the star caused by the gravitational pull of its neighbouring planet. Scientists estimate that Gaia could identify around 70,000 new exo-planets – planets outside of our solar system – by the end of the mission, which would be a dramatic increase on the 3,500 already known, most of which were identified by Nasa’s Kepler spacecraft.
“For the first time, we’ll be able to look at the distribution of planets based on the position of parent stars,” said Gilmore. “That will be a huge step forward in understanding planetary formation.”
Alvaro Giménez, ESA’s Director of Science, said: “Today’s release gives us a first impression of the extraordinary data that await us and that will revolutionise our understanding of how stars are distributed and move across our galaxy.”
Earth-like worlds capable of sustaining life may be less common than we thought
Life on other potentially habitable worlds might not receive enough light to sustain a thriving biosphere.
The potentially habitable exoplanet Kepler 422-b (left) compared with Earth (right)
Discovering exoplanets, those that lie outside of our solar system, has become fairly routine, thanks to some of the workhorse telescopes NASA and other space agencies have developed in the past two decades. Kepler has found thousands , including hellish lava planets, and TESS, launched in 2018 , continues to tally up its own collection of strange worlds .
But for all the worlds we're finding, very few sit in the "Goldilocks zone" -- a region around a star where the conditions are just right for liquid water to be present on the surface. Get too close to a star and the stuff boils away, too far out and it freezes. That makes it pretty hard for life -- as we know it -- to get a start.
Only a few dozen exoplanets discovered lie within the Goldilocks zone around their host stars, limiting the list of potentially habitable worlds scientists can probe for signs of alien existence. Typically, we look for worlds similar to our own. After all, Earth hosts living, breathing creatures of unfathomable variety, so similar conditions elsewhere should facilitate the same thing.
But some bad news for alien astronomers: Planets capable of sustaining life just like Earth does are likely pretty rare.
From the cosmos to your inbox. Get the latest science stories from CNET every week.
In a new study, published in the journal Monthly Notices of the Royal Astronomical Society, researchers studied 10 Earth-like planets in the Goldilocks zone, with a particular focus on measuring their capacity for oxygen-based photosynthesis, which they call OP.
On Earth, OP is critical. This is the same type of photosynthesis that powers plants. Light is absorbed and eventually converted to chemical energy. Complex life practically depends on the process on Earth, and very few organisms generate energy in other ways. The researchers suggest this process should be quite common in the cosmos because all planets receive light from their host stars.
Determining how much OP might be occurring on an exoplanet is possible by examining how much light is likely to reach the planet -- based on the distance to its host star and how hot and bright that star is. This measure helped the team calculate the "photosynthetically active radiation," or PAR, that a planet might receive.
Looking at 10 Earth analogues, the team found none come close to the amount of PAR Earth receives and thus couldn't sustain a biosphere like our own.
Red dwarf stars like Trappist-1 and Proxima Centauri don't shine as brightly or generate the same amount of heat as our sun does. That reduces the amount of PAR reaching exoplanets in their orbit. Because red dwarfs are the most common star in the Milky Way, the finding signals, perhaps, a second Earth might not be as common as astronomers had hoped.
"This study puts strong constraints on the parameter space for complex life, so unfortunately it appears that the 'sweet spot' for hosting a rich Earth-like biosphere is not so wide," said Giovanni Covone, an astrophysicist at the University of Naples and lead author of the study. Essentially, the Goldilocks zone may not be quite as broad as we thought.
However, the team did identify a slightly more promising target: Kepler-442b, which lies over 1,200 light-years from Earth . Kepler-442b is a little larger than Earth and twice as massive and has previously been earmarked as a potentially habitable exoplanet. It receives the largest amount of PAR in the studied planets and theoretically might be able to sustain the same amount of life as Earth does.
The researchers caution their method does have limitations. They only focused on how much light is reaching these Earth-like planets, but the OP process is much more complex. They also neglected some of the scenarios that reduce the efficiency of the light reaching a particular planet -- for instance, the fact some planetary atmospheres may absorb the light or cloud cover might prevent it from reaching the surface.
Twins! Distant Galaxy Looks Like Our Own Milky Way
Almost like a postcard from across the universe, astronomers have photographed a spiral galaxy that could be a twin of our own Milky Way.
The distant galaxy, called NGC 6744, was imaged by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at the European Southern Observatory's La Silla Observatory in Chile. The pinwheel lies 30 million light-years away in the southern constellation of Pavo (The Peacock).
We are lucky to have a bird's-eye view of the spiral galaxybecause of its orientation, face-on, as seen from Earth. It's a dead ringer for our own home in the cosmos, scientists say. [See the Milky Way's galactic twin NGC 6744]
"If we had the technology to escape the Milky Way and could look down on it from intergalactic space, this view is close to the one we would see &mdash striking spiral arms wrapping around a dense, elongated nucleus and a dusty disc," according to an ESO statement. "There is even a distorted companion galaxy &mdash NGC 6744A, seen here as a smudge to the lower right of NGC 6744, which is reminiscent of one of the Milky Way&rsquos neighboring Magellanic Clouds."
The main difference between NGC 6744 and the Milky Way is the two galaxies' size. While our galaxy is roughly 100,000 light-years across, our "twin" galaxy extends to almost twice that diameter, researchers said.
The photogenic object is one of the largest and nearest spiral galaxies to Earth. It's about as bright as 60 billion suns, and its light spreads across a large area in the sky &mdash about two-thirds the width of the full moon &mdash making the galaxy visible as a hazy glow through a small telescope.
The reddish spots along the spiral arms in NGC 6744 represent regions where new stars are being born.
The picture was created by combining four exposures taken through different filters that collected blue, yellow-green and red light and the glow coming from hydrogen gas. These are shown in the new picture as blue, green, orange and red, respectively.
Texas A&M-Led Astronomy Research Details Unprecedented Life Story of Milky Way Galaxy Evolution
Picture, if you will, the ultimate universal home movie if not parental keepsake and life story: our Milky Way Galaxy, starting out as but a wee collection of young stars some 12 billion years ago, continuously feeding on the gas of smaller nearby galaxies and undergoing a huge burst of star births to grow increasingly more massive, only to later fade out into the rather tame, large spiral galaxy we’ve come to inhabit today.
Despite many 21st century advances, from technology to social media apps, such a movie cannot be made. However, thanks to one of the most comprehensive multi-observatory galaxy surveys to date led by Texas A&M University’s Casey Papovich, astronomers have come up with the next best thing — the evolution of the Milky Way in pictures, pieced together using data from NASA and European Space Agency space telescopes and ground-based telescopes as well as thousands of snapshots of galaxies similar in mass to the Milky Way.
“As we look at distant galaxies, we see how they looked when their light left for Earth,” said Papovich, lead author on the international team’s science paper, which is published today in the April 10 issue of The Astrophysical Journal. “Because the galaxies are billions of light-years distant, we can see how they looked billions of years in the past.”
Papovich, along with Texas A&M postdoctoral researchers Vithal Tilvi and Ryan Quadri and roughly two dozen astronomers around the world, spent a year studying carefully selected distant galaxies similar in mass to the progenitor of our own Milky Way that were found in two deep-sky program surveys of the universe, the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) and the FourStar Galaxy Evolution Survey (ZFOURGE). First, the group looked at the more than 24,000 galaxies included in the combined catalog to identify representative galaxies that evolved as our Milky Way did. Then, they made a sequence of how those galaxies grew over time to represent how our own galaxy would have evolved, in effect creating a “movie” of the Milky Way’s life from youth to middle age.
“Most stars today exist in galaxies like the Milky Way, so by studying how galaxies like our own formed, we’ve come to understand the most typical locations of stars in the universe,” said Papovich, an associate professor in the Department of Physics and Astronomy and a member of the George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy since 2008. “We now have the best picture of how galaxies like our own formed their stars.”
Papovich says the team’s data clearly illustrates that the Milky Way experienced its most rapid phase of growth between 9.2 and 10 billion years ago, churning out new stars at a spectacular rate that was about 30 times what it is today — one per year, compared to about 30 each year 9.5 billion years ago. Not surprisingly, it also reveals a strong correlation between star formation and growth in galaxy size, suggesting that the Milky Way itself is responsible for its own star-generating, and therefore, staying power.
“When we calculate the star-formation rate of a Milky Way-like galaxy in the past and add up all the stars it would have produced, we find the mass growth we expected,” Papovich said. “We also know that most of these stars formed inside the Milky Way, rather than in other smaller galaxies that later merged with our own. The whole picture hangs together.”
Papovich notes that the Sun is among those more recently formed stars, born roughly 5 billion years ago at a point when star formation within the Milky Way had slowed to a comparatively cosmic crawl that continues today. The Sun’s somewhat fashionably late appearance actually may have been fortuitous, fostering the growth of the planets within our solar system.
The team’s multi-wavelength study, supported by funding from both NASA and the National Science Foundation, spans ultraviolet to far-infrared light, combining observations from NASA’s Hubble and Spitzer Space Telescopes, the European Space Agency’s Herschel Space Observatory, and ground-based telescopes, including the Magellan Baade Telescope at the Las Campanas Observatory in Chile. The Hubble images from the CANDELS survey also provided structural information about galaxy sizes and how they evolved. Far-infrared light observations from Spitzer and Herschel helped the astronomers trace the star-formation rate.
The international ZFOURGE collaboration is composed of several universities, including Leiden University in Holland, Swinburne and Macquarie in Australia, Carnegie Observatories in Pasadena, Calif. and Texas A&M, which currently hosts the survey’s website and data.
Find additional information on Papovich and his research.
Click here to see the official release and additional information from Hubble’s News Center.
ALMA Finds Young Milky Way-Like Galaxy in Early Universe
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have discovered an extremely distant galaxy that looks surprisingly like our own Milky Way Galaxy. Named SPT-S J041839-4751.9, this galaxy is located 12 billion light-years away and is strongly gravitationally lensed by a foreground galaxy. While SPT-S J041839-4751.9 doesn’t appear to have spiral arms, it has at least two features typical of our Milky Way: a rotating disk and a bulge, the large group of stars packed tightly around the galactic center.
A reconstructed image of SPT-S J041839-4751.9. Image credit: ALMA / ESO / NAOJ / NRAO / Rizzo et al, doi: 10.1038/s41586-020-2572-6.
In the early Universe, young galaxies were still in the process of forming, so astronomers expect them to be chaotic and lacking the distinct structures typical of more mature galaxies like the Milky Way.
“Studying distant galaxies like SPT-S J041839-4751.9 is fundamental to our understanding of how galaxies formed and evolved,” said lead author Francesca Rizzo of the Max Planck Institute for Astrophysics and colleagues.
“This galaxy is so far away we see it when the Universe was just 10% of its current age because its light took 12 billion years to reach Earth.”
“By studying it, we are going back to a time when these baby galaxies were just beginning to develop.”
“Because these galaxies are so far away, detailed observations with even the most powerful telescopes are almost impossible as the galaxies appear small and faint.”
Rizzo and co-authors overcame this obstacle by using a nearby galaxy as a powerful magnifying glass allowing ALMA to see into the distant past in unprecedented detail.
SPT-S J041839-4751.9 is gravitationally lensed by a foreground galaxy, appearing in the sky as a near-perfect ring of light. Image credit: ALMA / ESO / NAOJ / NRAO / Rizzo et al, doi: 10.1038/s41586-020-2572-6.
The gravitationally lensed SPT-S J041839-4751.9 appears as a near-perfect ring of light around the foreground galaxy, thanks to their almost exact alignment.
The astronomers reconstructed the distant galaxy’s true shape and the motion of its gas from the ALMA data using a new computer modeling technique.
“This result represents a breakthrough in the field of galaxy formation, showing that the structures that we observe in nearby spiral galaxies and in our Milky Way were already in place 12 billion years ago,” Rizzo said.
“The big surprise was to find that this galaxy is actually quite similar to nearby galaxies, contrary to all expectations from the models and previous, less detailed, observations,” said co-author Dr. Filippo Fraternali, an astronomer in the Kapteyn Astronomical Institute at the University of Groningen.
“What we found was quite puzzling despite forming stars at a high rate, and therefore being the site of highly energetic processes, SPT-S J041839-4751.9 is the most well-ordered galaxy disk ever observed in the early Universe,” said co-author Dr. Simona Vegetti, an astronomer at the Max Planck Institute for Astrophysics.
“This result is quite unexpected and has important implications for how we think galaxies evolve.”
The discovery, reported in a paper in the journal Nature, suggests the early Universe may not be as chaotic as once believed and raises many questions on how a well-ordered galaxy could have formed so soon after the Big Bang.
F. Rizzo et al. 2020. A dynamically cold disk galaxy in the early Universe. Nature 584, 201-204 doi: 10.1038/s41586-020-2572-6
ALMA sees most distant Milky Way look-alike
Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA), have revealed an extremely distant and therefore very young galaxy that looks surprisingly like our Milky Way. The galaxy is so far away its light has taken more than 12 billion years to reach us: we see it as it was when the Universe was just 1.4 billion years old. It is also surprisingly unchaotic, contradicting theories that all galaxies in the early Universe were turbulent and unstable. This unexpected discovery challenges our understanding of how galaxies form, giving new insights into the past of our Universe.
“This result represents a breakthrough in the field of galaxy formation, showing that the structures that we observe in nearby spiral galaxies and in our Milky Way were already in place 12 billion years ago,” says Francesca Rizzo, PhD student from the Max Planck Institute for Astrophysics in Germany, who led the research published today in Nature. While the galaxy the astronomers studied, called SPT0418-47, doesn’t appear to have spiral arms, it has at least two features typical of our Milky Way: a rotating disc and a bulge, the large group of stars packed tightly around the galactic centre. This is the first time a bulge has been seen this early in the history of the Universe, making SPT0418-47 the most distant Milky Way look-alike.
“The big surprise was to find that this galaxy is actually quite similar to nearby galaxies, contrary to all expectations from the models and previous, less detailed, observations,” says co-author Filippo Fraternali, from the Kapteyn Astronomical Institute, University of Groningen in the Netherlands. In the early Universe, young galaxies were still in the process of forming, so researchers expected them to be chaotic and lacking the distinct structures typical of more mature galaxies like the Milky Way.
Studying distant galaxies like SPT0418-47 is fundamental to our understanding of how galaxies formed and evolved. This galaxy is so far away we see it when the Universe was just 10% of its current age because its light took 12 billion years to reach Earth. By studying it, we are going back to a time when these baby galaxies were just beginning to develop.
Because these galaxies are so far away, detailed observations with even the most powerful telescopes are almost impossible as the galaxies appear small and faint. The team overcame this obstacle by using a nearby galaxy as a powerful magnifying glass — an effect known as gravitational lensing — allowing ALMA to see into the distant past in unprecedented detail. In this effect, the gravitational pull from the nearby galaxy distorts and bends the light from the distant galaxy, causing it to appear misshapen and magnified.
The gravitationally lensed, distant galaxy appears as a near-perfect ring of light around the nearby galaxy, thanks to their almost exact alignment. The research team reconstructed the distant galaxy’s true shape and the motion of its gas from the ALMA data using a new computer modelling technique. “When I first saw the reconstructed image of SPT0418-47 I could not believe it: a treasure chest was opening,” says Rizzo.
“What we found was quite puzzling despite forming stars at a high rate, and therefore being the site of highly energetic processes, SPT0418-47 is the most well-ordered galaxy disc ever observed in the early Universe,” stated co-author Simona Vegetti, also from the Max Planck Institute for Astrophysics. “This result is quite unexpected and has important implications for how we think galaxies evolve.” The astronomers note, however, that even though SPT0418-47 has a disc and other features similar to those of spiral galaxies we see today, they expect it to evolve into a galaxy very different from the Milky Way, and join the class of elliptical galaxies, another type of galaxies that, alongside the spirals, inhabit the Universe today.
This unexpected discovery suggests the early Universe may not be as chaotic as once believed and raises many questions on how a well-ordered galaxy could have formed so soon after the Big Bang. This ALMA finding follows the earlier discovery announced in May of a massive rotating disc seen at a similar distance. SPT0418-47 is seen in finer detail, thanks to the lensing effect, and has a bulge in addition to a disc, making it even more similar to our present-day Milky Way than the one studied previously.
Future studies will seek to uncover how typical these ‘baby’ disc galaxies really are and whether they are commonly less chaotic than predicted, opening up new avenues for astronomers to discover how galaxies evolved.
This research was presented in the paper “A dynamically cold disk galaxy in the early Universe” to appear in Nature (doi: 10.1038/s41586-020-2572-6).
The team is composed of F. Rizzo (Max Planck Institute for Astrophysics, Garching, Germany [MPA]), S. Vegetti (MPA), D. Powell (MPA), F. Fraternali (Kapteyn Astronomical Institute, University of Groningen, the Netherlands), J. P. McKean (Kapteyn Astronomical Institute and ASTRON, Netherlands Institute for Radio Astronomy), H. R. Stacey (MPA, Kapteyn Astronomical Institute and ASTRON, Netherlands Institute for Radio Astronomy) and S. D. M. White (MPA).
The original press release was published by the European Southern Observatory (ESO) an ALMA partner on behalf of Europe.
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), the U.S. National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the Ministry of Science and Technology (MOST) and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).
ALMA construction and operations are led by ESO on behalf of its Member States by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.
ImagesAstronomers using ALMA have revealed an extremely distant galaxy that looks surprisingly like our Milky Way. The galaxy, SPT0418-47, is gravitationally lensed by a nearby galaxy, appearing in the sky as a near-perfect ring of light. Credit: ALMA (ESO/NAOJ/NRAO), Rizzo et al. Astronomers using ALMA have revealed an extremely distant galaxy that looks surprisingly like our Milky Way. The galaxy, SPT0418-47, is gravitationally lensed by a nearby galaxy, appearing in the sky as a near-perfect ring of light. The research team reconstructed the distant galaxy’s true shape, shown here, and the motion of its gas from the ALMA data using a new computer modelling technique. Credit: ALMA (ESO/NAOJ/NRAO), Rizzo et al. Astronomers using ALMA have revealed an extremely distant galaxy that looks surprisingly like our Milky Way. The galaxy, SPT0418-47, is gravitationally lensed by a nearby galaxy, appearing in the sky as a near-perfect ring of light (left). The research team reconstructed the distant galaxy’s true shape and the motion of its gas (right) from the ALMA data using a new computer modelling technique. The observations indicate that SPT0418-47 is a disc galaxy with a central bulge and the material in it rotates around the centre. Gas moving away from us is shown in red, while gas moving in the direction of the observer is shown in blue. Credit: ALMA (ESO/NAOJ/NRAO), Rizzo et al.
Astronomers spy distant galaxy - and it looks 'surprisingly like our Milky Way'
NASA: Lucy mission set to study Asteroids through Space
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The astronomers added the cosmic neighbourhood resembles a near-perfect ring of light in space. Max Planck Institute astronomers used Chile&rsquos Atacama Large Millimeter / submillimeter Array (ALMA) telescope to find the galaxy 12 billion light years away from our planet.
Sure to its extreme distance, astronomers are viewing the galaxy when the universe was only 1.4 billion years old.
&ldquoWhen I first saw the reconstructed image of SPT0418-47 I could not believe it
And galaxy SPT0418-47 is surprisingly un-chaotic, contradicting theories all galaxies in the early universe were turbulent and unstable.
The discovery shows structures in our Milky Way and other spiral galaxies when the universe was young, authors say.
Although the galaxy studied by astronomers does not appear to have spiral arms, it boasts at least two features typical of our Milky Way - a bulge and rotating disc.
Astronomers have spotted a distant galaxy resembling ours (Image: ALMA)
SPT0418-47 is a disc galaxy with a central bulge (Image: ALMA)
A bulge is the large group of stars packed tightly around the galactic centre of spiral galaxies - seen as a white blob in the Milky Way.
This is the first time a bulge has been spotted so early in the Universe&rsquos history, making SPT0418-47 the most distant Milky Way doppelganger.
The study&rsquos co-author Filippo Fraternali said: &ldquoThe big surprise was to find that this galaxy is actually quite similar to nearby galaxies, contrary to all expectations from the models and previous, less detailed, observations.&rdquo
The University of Groningen astronomer added the young galaxies in the early universe were still in the process of forming.
Astronomers have revealed an extremely distant galaxy that looks surprisingly like our Milky Way (Image: ALMA)
This led researchers to expect them to be chaotic and lacking the distinct structures typical of more mature galaxies like the Milky Way.
Studying distant galaxies like SPT0418-47 is considered key to understanding how galaxies evolved.
This galaxy is so distant the Universe was a mere 10 percent of its current age because its light took 12 billion years to reach our planet.
By studying the galaxy, astronomers are going back to a time when these nascent galaxies were only beginning to form.
Because these galaxies are so distant from Earth, detailed observations with even the most powerful telescopes are almost impossible as the galaxies appear so faint.
The researchers overcame this obstacle by using a nearby galaxy as a powerful magnifying glass - a technique called &lsquogravitational lensing&rsquo.
This harnesses the gravitational pull from a nearby galaxy, which distorts the light from the distant galaxy, causing it to appear misshapen and magnified.
This allowed Earth-based ALMA to see into the distant past in unprecedented detail.
The gravitationally lensed, distant galaxy appears as a near-perfect ring of light around the nearby galaxy, thanks to their almost exact alignment.
Astronomers are viewing the galaxy when the Universe was only 1.4 billion years old (Image: Express)
The research team reconstructed the distant galaxy's true shape and the motion of its gas from the ALMA telescope data using updated models.
Dr Rizzo said: &ldquoWhen I first saw the reconstructed image of SPT0418-47 I could not believe it: a treasure chest was opening.
Co-author Simona Vegetti from the Max Planck Institute, said it is the most well-ordered galaxy disc observed from the early universe.
He said: &ldquoIt was puzzling. This result is quite unexpected and has important implications for how we think galaxies evolve.&rdquo
However, even though SPT0418-47 has a disc and other features similar to those of spiral galaxies we see today, they expect it to evolve into a galaxy quite distinct from ours.
Astronomers Find ‘Fossil Galaxy’ Hidden in Depths of Milky Way
A small satellite galaxy, named Heracles, collided with our Milky Way Galaxy about 10 billion years ago and its remnants account for about one third of the Milky Way’s spherical halo, according to an analysis of data gathered by Sloan Digital Sky Surveys’ Apache Point Observatory Galactic Evolution Experiment (APOGEE).
An artist’s impression of what the Milky Way might look like seen from above. The colored rings show the rough extent of the Heracles galaxy. The yellow dot shows the position of the Sun. Image credit: Danny Horta-Darrington, Liverpool John Moores University / NASA / JPL-Caltech / SDSS.
“To find a fossil galaxy like this one, we had to look at the detailed chemical makeup and motions of tens of thousands of stars,” said Dr. Ricardo Schiavon, an astronomer at Liverpool John Moores University.
“That is especially hard to do for stars in the center of the Milky Way, because they are hidden from view by clouds of interstellar dust.”
“APOGEE lets us pierce through that dust and see deeper into the heart of the Milky Way than ever before.”
“APOGEE does this by taking spectra of stars in near-infrared light, instead of visible light, which gets obscured by dust.”
Over its ten-year observational life, APOGEE has measured spectra for more than half a million stars all across the Milky Way, including its previously dust-obscured core.
“Examining such a large number of stars is necessary to find unusual stars in the densely-populated heart of the Milky Way, which is like finding needles in a haystack,” said Danny Horta, a graduate student at Liverpool John Moores University.
To separate stars belonging to Heracles from those of the original Milky Way, the astronomers made use of both chemical compositions and velocities of stars measured by the APOGEE instrument.
“Of the tens of thousands of stars we looked at, a few hundred had strikingly different chemical compositions and velocities,” Horta said.
“These stars are so different that they could only have come from another galaxy. By studying them in detail, we could trace out the precise location and history of this fossil galaxy.”
The team found that Heracles’ stars account for roughly one third of the mass of the entire Milky Way halo today, meaning that this newly-discovered ancient collision must have been a major event in the history of our Galaxy.
That suggests that the Milky Way may be unusual, since most similar massive spiral galaxies had much calmer early lives.
“As our cosmic home, the Milky Way is already special to us, but this ancient galaxy buried within makes it even more special,” Dr. Schiavon said.
The findings are published in the Monthly Notices of the Royal Astronomical Society.
Danny Horta et al. 2020. Evidence from APOGEE for the presence of a major building block of the halo buried in the inner Galaxy. MNRAS 500 (1): 1385-1403 doi: 10.1093/mnras/staa2987
What Does Our Galaxy Look Like?
Studying the shape of our own galaxy is a bit of a tricky endeavor for astronomers. We are on the inside of the galaxy, so it is practically impossible for us to get a look at the “big-picture” view of our Milky Way and see its structure directly. However, there are some methods that can be used to infer the shape and size of the galaxy by studying other variables. As was explained in the video lecture, in the sky there is a relatively thin, flat band that stretches across the sky. With the help of telescopes we have been able to find that this band contains tons of stars. By studying this band, astronomers have found that it looks like the formation of our galaxy looks in a way similar to how our star system formed in a fairly flat plane. They then began to measure distances between all the different stars and have determined that in addition to the galaxy being disk-like in shape, it also contains many spiral arms with large clusters of stars. Additionally, by looking out at stars from the furthest ends of the galaxy, astronomers have determined that the Milky Way is about 100,000 light years across.