The Milky Way’s Lost Sister Galaxy has been found
The first galaxies formed long ago, when our nearly 14 billion year old Universe was less than a billion years old. Our own Milky Way Galaxy similarly is extremely ancient–a large starlit pinwheel twirling in space that’s considered to be about 13.6 billion years old–give or take 8 million decades. Indeed, the earliest known star in our Galaxy is 13.7 billion years old. Altogether, the Milky Way is believed to host approximately 300 billion stars. But, though our Galaxy has many galactic neighbors, among its tremendous starlit siblings has gone missing, disappearing mysteriously billions of years back. Alas, the group of scientists have cautioned that our present nearest large galactic neighbor shredded and cannibalized this gigantic sister of our Milky Way two billion years back.
Despite the fact that it was mostly devoured and shredded, this gigantic sister galaxy left behind, as a lingering tattle-tale relic of its former presence, a trail of evidence showing that it was here. This rich trail of proof is made up of an almost invisible halo of stars which is bigger than our Milky Way’s biggest spiral neighbor, the Andromeda galaxy itself. The evidence also is composed of an elusive flow of celebrities, in addition to another mysterious and enigmatic galaxy called M32. Discovering and celebrating this partially devoured doomed galaxy can help astronomers understand how disc galaxies like our Milky Way evolve and can survive big and violent mergers wth other enormous galaxies.
The group of galaxies that includes our Milky Way is appropriately named the Local Group, and it hosts over 54 galaxies, most of which are comparatively compact dwarfs. Astronomers have predicted that sometime between 1 billion and 1 trillion years from now, each the galactic constituents of this Local Group will crash into one another, and these crashes and resulting mergers will produce one enormous galaxy. The gravitational centre of the Local Group now is located between our Milky Way and Andromeda, and the full group sports the remarkable diameter of approximately 3.1 million parsecs. Additionally, it shows a binary (dumbell) distribution. The Local Group itself is a part of the larger Virgo Supercluster that may, in turn, be part of the newly discovered Laniakea Supercluster.
The unfortunate, decimated galaxy, dubbed M32p, was formerly the third-largest member of this Local Group, following our Milky Way and Andromeda. Using supercomputer versions, Dr. Richard D’Souza and Dr. Eric Bell of the University of Michigan’s Department of Astronomy managed to piece together the lingering tattle-tale proof of the galactic crime, showing all that’s left of the cannibalized sister of our own Galaxy.
The bigger duo of those three spiral galaxies each have their own system of satellite galaxies. Both the Milky Way and Andromeda are majestic spirals that show starlit spiral arms which whirl majestically in space. However, this won’t always be true. The constant and merciless pull of strong gravity is tugging Andromeda towards our Galaxy in the breathtaking rate of 250,000 mph.
Indeed, the upcoming collision of our Galaxy with Andromeda will make an entirely new Galaxy, one which will probably exhibit an elliptical shape, rather than the elegant starlit spiral”pinwheel” arms of both badly disrupted galactic parents. This strange new Galaxy has been given the name Milkomeda, though there’ll probably be no human life left on Earth to witness the enormous new Galaxy which will rise from the wreckage of the monumental merger.
Such galactic wrecks might not be quite as violent as once believed. These collisions are observed in distant galaxies through the Cosmos, and even though galaxies are seen smashing into one another, it’s improbable that any two of the constituent stars will match up and combine. The splattered wreckage that would be left behind in the aftermath of a two-star crash could create a enormous stellar mess. The fantastic thing is that the distance between stars inside a host galaxy is generally vast. That is why violent stellar smash-ups rarely happen.
In contrast, the floating clouds of dust and gas that swirl around together in their host galaxies, will likely suffer as a consequence of a smash-up and merger. That type of unlucky and catastrophic event will be violent and create a horrific mess. This is because such a mess will activate star-birth within churning, writhing clouds of dust and gas. These cold dark clouds act as the strange cradles of bright new baby celebrities, which are born in a stunning, brilliant, blaze of newborn glory.
Galactic head-long collisions happen over long stretches of time–they could last as long as countless billions of years, and they aren’t quickly over for the parties that are suffering. But, our Milky Way has been blessed because a violent collision with a similarly large galaxy hasn’t happened throughout its whole 13.6 billion year history–at least, not yet.
About 3.75 billion years from now, the skies over our world will be filled with Andromeda, as it makes its deadly approach towards our Galaxy. For the next few billion years, as a consequence of Andromeda’s strategy, there’ll be brilliant blasts of fiery stellar birth light up Earth’s night sky.
In about 7 billion years, the skies above our planet will get even more strange and alien. The glaring core of the newborn Milkomeda Galaxy–now our very own host Galaxy–will take over the full sky. However, the possibility of human beings being around to see this sight is distant. This is because our Sun will probably evolve into a huge, swollen, perishing red giant star roughly 5 billion years from now, and will have already incinerated its inner planets–Mercury, Venus, and Earth–long before the head-long smash-up between the two galaxies has happened.
Our Milky Way and Andromeda are roughly the same age. Although both sister galaxies are thought of as almost identical twins, it’s a bit hard to predict that one of the doomed duo will endure the most when the end comes. However, as Andromeda is a little larger than our own Galaxy, technically it will be Andromeda that will feast on our Milky Way.
Astronomers have known for a long time that almost invisible large halos of celebrities encircle galaxies, and that these halos include the sad relics of smaller cannibalized galaxies. Indeed, a huge galaxy like Andromeda is considered to have devoured literally tens of thousands of its smaller companies in this galaxy-eat-galaxy Universe. Because of this, many astronomers thought it would be a tricky job to learn about the history of any particular one of those unfortunate little galaxies.
However, the group of astronomers using new supercomputer simulations could come to a different understanding. The scientists found that although a high number of companion galaxies were devoured by Andromeda, the majority of the leading inhabitants of the galaxy’s outer dim halo were the unfortunate children of a shredded single big galaxy.
We realized we can use this advice of Andromeda’s outer stellar halo to infer the properties of the biggest of these shredded galaxies,” commented study lead author Dr. D’Souza at a July 23, 2018 University of Michigan Press Release.
It was shocking to realize that the Milky Way had a huge sibling, and we never knew about it,” said co-author Dr. Bell at the exact same Press Release.
This unfortunate sister galaxy of our Milky Way, M32p, that was shredded mercilessly from the voracious Andromeda galaxy, was 20 times larger than any galaxy that merged with the Milky Way over the course of its more than 13 billion year existence. M32p could have been quite massive, and probably would have become the third largest galaxy in the Local Group, after Andromeda and our Milky Way, had it not been shredded and swallowed by Andromeda.
This new analysis might also address an intriguing puzzle: the creation of Andromeda’s perplexing M32 satellite galaxy. The astronomers now suggest that the compact and compact M32 is truly the living central hub of the Milky Way’s long-lost sister. The team of astronomers compare M32 into the pit of a plum.
While it resembles a compact case of an old, elliptical galaxy, it really has plenty of young stars. It’s among the most compact galaxies in the Universe.
The astronomers recognized that Andromeda’s disk had managed to endure a smash-up using a enormous galaxy. This effect would challenge the conventional viewpoint that such big interactions would invariably ruin the orderly disks of spirals, thus creating only elliptical galaxies.
The timing of this effect may also shed new light on the thickening of Andromeda’s disk, in addition to on a mysterious burst of brilliant star-birth that happened about two billion years back.
“The Andromeda Galaxy, with a spectacular burst of star formation, would have appeared so different 2 billion years back.
The fantastic thing is that this study may also be used for other galaxies. This would allow astronomers to quantify their massive past galaxy mergers. Armed with this new knowledge, scientists can go to untangle the complex and complex tapestry of cause and effect which triggers galaxy development, in addition to find out about what mergers do into the galaxies that have to suffer through them.