Milky Way’s Black Hole Just Flared, Growing 75 Times as Bright for a Few Hours

Illustration of the supermassive black hole at the center of the Milky Way. Credit: NRAO/AUI/NSF

Even though the black hole at the center of the Milky Way is a monster, it’s still rather quiet. Called Sagittarius A*, it’s about 4.6 million times more massive than our Sun. Usually, it’s a brooding behemoth. But scientists observing Sgr. A* with the Keck Telescope just watched as its brightness bloomed to over 75 times normal for a few hours.

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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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This is What It’ll Look Like When the Milky Way and Andromeda Galaxies Collide Billions of Years from Now

Located in the constellation of Hercules, about 230 million light-years away, NGC 6052 is a pair of colliding galaxies. Image Credit: ESA/Hubble & NASA, A. Adamo et al.

What happens when two galaxies collide? The Milky Way and the Andromeda Galaxy are on a collision course, and in about 4.5 billion years, they will meet. Now astronomers using the Hubble have provided some visual insight into what that collision might look like.

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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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Gas and Dust Seen Swirling Around our Galaxy’s Supermassive Black Hole

ALMA images show gas and dust swirling around the supermassive black hole at the center of the Milky Way. Image Credit: ALMA (ESO/NAOJ/NRAO)/ J. R. Goicoechea (Instituto de FĂ­sica Fundamental, CSIC, Spain)

At the heart of the Milky Way Galaxy lurks a Supermassive Black Hole (SMBH) named Sagittarius A* (Sag. A-star). Sag. A* is an object of intense study, even though you can’t actually see it. But new images from the Atacama Large Millimetre/sub-millimetre Array (ALMA) reveal swirling high-speed clouds of gas and dust orbiting the black hole, the next best thing to seeing the hole itself.

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The Milky Way is Still Rippling from a Galactic Collision Millions of Years Ago

The ESA's Gaia mission has discovered evidence of a primordial galactic collision between our Milky Way galaxy and the nearby Sagittarius dwarf galaxy. Image: ESA/Gaia

Between 300 million and 900 million years ago, our Milky Way galaxy nearly collided with the Sagittarius dwarf galaxy. Data from the ESA’s Gaia mission shows the ongoing effect of this event, with stars moving like ripples on the surface of a pond. The galactic collision is part of an ongoing cannibalization of the dwarf galaxy by the much-larger Milky Way.

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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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