According to Simulations, the Milky Way is One in a Million

A lonely Milky Way analogue galaxy, too massive for its wall. The background image shows the distribution of dark matter (green and blue) and galaxies (here seen as tiny yellow dots) in a thin slice of the cubic volume in which we expect to find one of such rare massive galaxies. Credit Images: Miguel A. Aragon-Calvo. Simulation data: Illustris TNG project Licence type Attribution (CC BY 4.0)

Humanity is in a back-and-forth relationship with nature. First, we thought we were at the center of everything, with the Sun and the entire cosmos rotating around our little planet. We eventually realized that wasn’t true. Over the centuries, we’ve found that though Earth and life might be rare, our Sun is pretty normal, our Solar System is relatively non-descript, and even our galaxy is one of the billions of spiral galaxies, a type that makes up 60% of the galaxies in the Universe.

But the Illustris TNG simulation shows that the Milky Way is special.

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A New Survey of the Milky Way Reveals Billions of Objects, Helping to Map Our Surroundings in Three Dimensions

This image, which is brimming with stars and dark dust clouds, is a small extract — a mere pinprick — of the full Dark Energy Camera Plane Survey (DECaPS2) of the Milky Way. The new dataset contains a staggering 3.32 billion celestial objects — arguably the largest such catalog so far. DECaPS2/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Image processing: M. Zamani & D. de Martin (NSF’s NOIRLab)

The Dark Energy Camera Plane Survey 2 (DECaPS2) is out. This is the second data release from DECaPS, and the survey contains over 3 billion objects in the Milky Way. As the leading image shows, there are so many stars it appears as if there’s no space between them.

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You’re Looking at a Map of the Milky Way’s Magnetic Field

Colour shows the polarized microwave emission measured by QUIJOTE. The pattern of lines superposed shows the direction of the magnetic field lines. Credit: The QUIJOTE Collaboration.

Using telescopes that study the sky in the microwave part of the electromagnetic spectrum, astronomers have successfully mapped the structure of the magnetic field of the Milky Way galaxy. While magnetic fields are difficult to measure in space, an international team of astronomers used the Teide Observatory on Tenerife in the Canary Islands to conduct 10 years of observations.

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Astronomers use the World's Biggest Radio Telescope to map new Features of the Milky Way

Artist impression of a fast radio burst. Credit: Danielle Futselaar

Despite everything astronomers have learned about the nature and structure of galaxies, there are still mysteries about the Milky Way. The reason for this is simple: since we are embedded in the Milky Way’s disk, we have difficulty mapping it and observing it as a whole. It’s also very challenging to observe the center of the galaxy, what lies beyond it, and features in the disk itself because of all the gas and dust between stars- the Interstellar Medium (ISM). However, by observing the Milky Way in the non-visible spectrum (radio, x-ray, gamma-ray, etc.), astronomers can see more of what’s out there.

There’s also the spectral line that corresponds to the emission frequency (1420 MHz) of cold neutral hydrogen gas (HI), which makes up the majority of the ISM. Using the Five-hundred-meter Aperture Spherical Telescope (FAST) – the most powerful radio telescope in the world near Guizhou, China – a team of scientists located more than 500 new faint pulsars. During the survey, the team simultaneously recorded the spectral line data with high spectral and spatial resolution, making it an extremely valuable resource for studying the structure of the Milky Way Galaxy and the life cycle of its stars.

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Newly Found Stars are Technically in the Milky Way, but They’re Halfway to Andromeda

This illustration shows the Milky Way galaxy's inner and outer halos. A halo is a spherical cloud of stars surrounding a galaxy. (Image Credits: NASA, ESA, and A. Feild [STScI])
This illustration shows the Milky Way galaxy's inner and outer halos. A halo is a spherical cloud of stars surrounding a galaxy. A population of RR Lyrae variables in the halo is giving clues to its distance. (Image Credits: NASA, ESA, and A. Feild [STScI])

We all know our galaxy, the Milky Way, is big. Really big. But, exactly how far out does it extend? Where are the outer limits? Astronomers aren’t exactly sure, precisely. However, a study of galaxies in the Virgo Cluster accidentally turned up a population of stars in the outer part of the Milky Way. They may answer those questions.

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A new 3D map of the Milky Way Uses close to 66,000 Stars and Reveals New Details About the Shape of our Galaxy

The warping of the Milky Way disk. Credit: University of Warsaw

In the 17th century, Galileo Galilee aimed his telescope at the stars and demonstrated (for the first time) that the Milky Way was not a nebulous band but a collection of distant stars. This led to the discovery that our Sun was merely one of the countless stars in a much larger structure: the Milky Way Galaxy. By the 18th century, William Herschel became the first astronomer to create a map that attempted to capture the shape of the Milky Way. Even after all that time and discovery, astronomers are still plagued by the problem of perspective.

While we have been able to characterize galaxies we see across the cosmos with relative ease, it is difficult for astronomers to study the size, shape, and population of the Milky Way because of how our Solar System is embedded in its disk. Luckily, there are methods to circumvent this problem of perspective, which have provided astronomers with clues to these questions. In a recent paper, a team from the Astronomical Observatory at the University of Warsaw (AstroUW) used a large collection of Mira variable stars to trace the shape of the Milky Way, which yielded some interesting results!

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The Milky Way’s Stellar Halo Isn’t a Sphere After All

stellar halo around the milky way
The Milky Way's anatomy includes a rounded stellar halo That view is changing with new data. Image courtesy ESA.

Our galaxy’s stellar halo is giving astronomers some new food for thought. It turns out everyone thought the halo was spherical. But, it’s not. That’s news to everyone who said it was spherical. According to a new measurement done by a team at Harvard-Smithsonian Center for Astrophysics, it has a tilted, oblong football shape. This all tells astronomers an interesting tale about our galaxy’s ancient history.

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A Dwarf Galaxy Passed Close to the Milky Way and Left Ripples in its Wake

Artist's view of ripples on the edge of the Milky Way. Credit: NASA JPL-Caltech R. Hurt (SSC Caltech)

When you imagine the collision of galaxies, you probably think of something violent and transformational. Spiral arms ripped apart, stars colliding, cats and dogs living together, mass hysteria. The reality is much less dramatic. As a recent study shows, our galaxy is in a collision right now.

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Star Formation in the Center of the Milky Way Started at the Core and Then Worked its way out

False-color image of the region Sagittarius B1, as seen by the GALACTICNUCLEUS survey. Credit & ©: F. Nogueras-Lara et al. / MPIA

One of the biggest questions facing astronomers today concerns star formation and its role in the evolution of galaxies. In particular, astronomers are curious whether the process began in the central regions of galaxies, where stars are more tightly bound. Previous observations have shown that numerous galaxies experienced intense periods of star formation in their centers roughly one billion years after the Big Bang. For some time, astronomers have wanted to conduct similar observations of the Milky Way’s Galactic Center to study rapid star formation more closely.

Unfortunately, it has been very difficult for astronomers to study the center of the Milky Way because of how bright and densely packed the region is, which makes it difficult to discern individual stars and clusters. Thanks to a new analysis of a high-resolution infrared survey, a team of astronomers has created the first reconstruction of the star formation history in the Galactic Center. According to their findings, most young stars in this region formed in loose stellar associations that dispersed outwards to fill the Galactic Disk over the course of many eons (as opposed to tightly-knit massive clusters).

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Is This the Future of the Milky Way?

The central region of the giant elliptical galaxy NGC 474. It's set against a backdrop of more distant galaxies. Will the Milky Way resemble this galaxy in the distant future? This image was taken using the Hubble Advanced Camera for Surveys, and includes data from the Wide Field and Planetary Camera 3. (Courtesy NASA/STScI.)
The central region of the giant elliptical galaxy NGC 474. It’s set against a backdrop of more distant galaxies. Will the Milky Way resemble this galaxy in the distant future? This image was taken using the Hubble Advanced Camera for Surveys, and includes data from the Wide Field and Planetary Camera 3. (Courtesy NASA/STScI.)

Take a good look at the latest image provided by the Hubble Space Telescope. It shows a huge elliptical galaxy called NGC 474 that lies about 100 million light-years away from us. At about two and a half times larger than our Milky Way Galaxy, it’s really a behemoth. Notice its strange structure—mostly featureless and nearly round, but with layered shells wrapped around the central core. Astronomers want to know what caused these shells. The answer might be in what this galaxy represents: a vision of the future Milky Way and the Andromeda Galaxy.

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