Earth, Solar System, Milky Way. Are they Getting More or Less Massive Over Time?

According to the most widely-accepted cosmological models, the first galaxies began to form between 13 and 14 billion years ago. Over the course of the next billion years, the cosmic structures we’ve all come to know emerged. These include things like galaxy clusters, superclusters, and filaments, but also galactic features like globular clusters, galactic bulges, and Supermassive Black Holes (SMBHs).

However, like living organisms, galaxies have continued to evolve ever since. In fact, over the course of their lifetimes, galaxies accrete and eject mass all the time. In a recent study, an international team of astronomers calculated the rate of inflow and outflow of material for the Milky Way. Then the good folks at astrobites gave it a good breakdown and showed just how relevant it is to our understanding of galactic formation and evolution.

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Gaia Mission is Mapping Out the Bar at the Center of the Milky Way

Despite the many advancements made in the field of astronomy, astronomers still struggle to get an accurate assessment of the Milky Way Galaxy. Because we are embedded in its disk, it is much more difficult to assess its size, structure, and extent – unlike galaxies located millions (or billions) of light-years away. Luckily, thanks to improved instruments and tireless efforts, progress is being made all the time.

For instance, a team of astronomers recently combined the latest data obtained by the ESA’s Gaia observatory with the infrared and optical observations of other telescopes to start mapping the bar-shaped collection of stars at the center of our Milky Way. This constitutes the first time in history that astronomers have been able to make direct measurements of this barred structure.

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The Most Efficient Way to Explore the Entire Milky Way, Star by Star

It seems like the stuff of dreams, the idea that humanity will one day venture beyond the Solar System and become an interstellar species. Who knows? Given enough time and the right technology (and assuming there’s not some serious competition), we might even be able to colonize the entire Milky Way galaxy someday. And while this seems like a far-off prospect at best, it makes sense to contemplate what a process like this would entail.

That’s what a think tank from the ESA’s Advanced Concepts Team (ACT) managed to do recently. As part of the tenth annual Global Trajectory Optimization Competition (GOTC X), they created a simulation that showed how humanity could optimally colonize the Milky Way. This was in keeping with the competition’s theme of “Settlers of the Galaxy“, which challenged teams to find the most energy-efficient way of settling as many star systems as possible.

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Perfect Example of a Barred Spiral Galaxy, Seen Face On. This is What Our Milky Way Might Look Like

The Hubble Space Telescope has given us a beautiful image of the barred spiral galaxy NGC 7773. This is a classic galaxy of this type, and highlights the bright bar of concentrated stars that anchors the galaxy’s stately spiral arms. It was captured with the Hubble’s workhorse Wide Field Camera 3 (WFC3.)

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Voyager and Pioneer’s Grand Tour of the Milky Way

During the early 1990s, NASA’s Pioneer 10 and 11 probes became the first robotic missions to venture beyond Neptune. In 2012 and 2018, the Voyager 1 and 2 missions went even farther by crossing the heliopause and entering interstellar space. Eventually, these probes may reach another star system, where their special cargo (the Pioneer Plaques and the Golden Records) could find their way into the hands of another species.

Which raises an important question: where might these spacecraft eventually wander? To address this, Coryn Bailer-Jones of the Max Planck Institute for Astronomy and Davide Farnocchia of NASA’s Jet Propulsion Laboratory recently conducted a study that examined which star systems the Voyager and Pioneer probes will likely encounter as they drift through the Milky Way over the next few million years…

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Thanks to Gaia, We Now Know Exactly When We’ll be Colliding with Andromeda

The trajectories of the Milky Way, Andromeda, and the Triangulam galaxies. Image Credit: E. Patel, G. Besla (University of Arizona), R. van der Marel (STScI)

Astronomers have known for some time that the Milky Way and the Andromeda galaxies will collide on some future date. The best guess for that rendezvous has been about 3.75 billion years from now. But now a new study based on Data Release 2 from the ESA’s Gaia mission is bringing some clarity to this future collision.

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The Milky Way is Actually Warped

For centuries, astronomers have been studying the Milky Way in order to get a better understanding of its size and structure. And while modern instruments have yielded invaluable observations of our galaxy and others (which have allowed astronomers to gain a general picture of what it looks like), a truly accurate model of our galaxy has been elusive.

For example, a recent study by a team of astronomers from National Astronomical Observatories of Chinese Academy of Sciences (NAOC) has shown that the Milky Way’s disk is not flat (as previously thought). Based on their findings, it appears that the Milky Way becomes increasingly warped and twisted the farther away one ventures from the core.

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One of Our Best Views of the Supermassive Black Hole at the Heart of the Milky Way

Top left: simulation of Sgr A* at 86 GHz without interstellar scattering. Top right: simulation with interstellar scattering. Bottom right: observed image of Sgr A*. Bottom left: observed image of Sgr A* after removing the effects of interstellar scattering. Credit: S. Issaoun, M. Mo?cibrodzka, Radboud University/ M. D. Johnson, CfA

An almost unimaginably enormous black hole is situated at the heart of the Milky Way. It’s called a Supermassive Black Hole (SMBH), and astronomers think that almost all massive galaxies have one at their center. But of course, nobody’s ever seen one (sort of, more on that later): It’s all based on evidence other than direct observation.

The Milky Way’s SMBH is called Sagittarius A* (Sgr. A*) and it’s about 4 million times more massive than the Sun. Scientists know it’s there because we can observe the effect it has on matter that gets too close to it. Now, we have one of our best views yet of Sgr. A*, thanks to a team of scientists using a technique called interferometry.

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The Milky Way Could Be Spreading Life From Star to Star

For almost two centuries, scientists have theorized that life may be distributed throughout the Universe by meteoroids, asteroids, planetoids, and other astronomical objects. This theory, known as Panspermia, is based on the idea that microorganisms and the chemical precursors of life are able to survive being transported from one star system to the next.

Expanding on this theory, a team of researchers from the Harvard Smithsonian Center for Astrophysics (CfA) conducted a study that considered whether panspermia could be possible on a galactic scale. According to the model they created, they determined that the entire Milky Way (and even other galaxies) could be exchanging the components necessary for life.

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Narrowing Down the Mass of the Milky Way

Since the birth of modern astronomy, scientists have sought to determine the full extent of the Milky Way galaxy and learn more about its structure, formation and evolution. At present, astronomers estimate that it is 100,000 to 180,000 light-years in diameter and consists of 100 to 400 billion stars – though some estimates say there could be as many as 1 trillion.

And yet, even after decades of research and observations, there is still much about our galaxy astronomers do not know. For example, they are still trying to determine how massive the Milky Way is, and estimates vary widely. In a new study, a team of international scientists presents a new method for weighing the galaxy based the dynamics of the Milky Way’s satellites galaxies.

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