The Milky Way Is Gaining New Stars From A Collision That Hasn’t Even Occurred Yet
“This is the first direct evidence of new stars forming from any galactic stream associated with the Magellanic Clouds, and it appears to have occurred from a stream of gas that’s already passed through the galactic plane. It’s eminently conceivable that it was that very event – when this gas ejected from the Magellanic Clouds passed through the Milky Way’s disk – was what triggered the formation of the new stars we’re seeing today.
When you take all of this information together, it leads to a remarkable conclusion that changes the way we think our local galactic neighborhood is evolving. New gas is already being funneled into the Milky way from satellite galaxies that are still nearly 200,000 light-years away. This gas, low in heavy element abundance but cool in temperature, provides about 95% of the cold gas suitable for the formation of new Milky Way stars. These nearby galaxies haven’t even encountered us yet, and we’re already forming new stars because of them.”
In another few hundred million years, the two Magellanic Clouds, located a little less than 200,000 light-years away, will collide with and begin merging with our Milky Way. But already, over 100 million years ago, a fraction of the gas from these clouds came into our galaxy and formed stars! 94,000 light-years away, in the halo of the Milky Way, these stars are unlike anything else seen in our galaxy before.
Here’s how the Milky Way has gained stars from a collision that hasn’t even occurred yet, and what it means for our galaxy’s future!
This Is What The Milky Way’s Magnetic Field Looks Like
“The Milky Way’s gas, dust, stars and more create fascinating, measurable structures. Subtracting out all the foregrounds yields the cosmic background signal, which possesses tiny temperature imperfections. But the galactic foreground isn’t useless; it’s a map unto itself. All background light gets polarized by these foregrounds, enabling the reconstruction of our galaxy’s magnetic field.”
Have you ever wondered what our galaxy’s magnetic field looks like? As long as we restrict ourselves to looking in the type of light that human eyes can see, the optical portion of the spectrum, we’re extremely limited as far as what we can infer. However, if we move on to data from the microwave portion of the spectrum, and in particular we look at the data that comes from the polarization of background light (and the foreground light directly), we should be able to reconstruct our galaxy’s magnetic fields to the best precision ever. The Planck satellite, in addition to mapping the CMB to better precision than ever before, has enabled us to do exactly that.
Even though there are still some small questions and uncertainties, you won’t want to miss these incredible pictures that showcase just how far we’ve come!
General Relativity Rules: Einstein Victorious In Unprecedented Gravitational Redshift Test
“The most interesting part of this result is that it clearly demonstrates the purely General Relativistic effect of gravitational redshift. The observations of S0-2 showcase an exact agreement with Einstein’s predictions, within the measurement uncertainties. When Einstein first conceived of General Relativity, he did so conceptually: with the idea that acceleration and gravitation were indistinguishable to an observer.
With the validation of Einstein’s predictions for the orbit of this star around the galactic center’s black hole, scientists have affirmed the equivalence principle, thereby ruling out or constraining alternative theories of gravity that violate this cornerstone of Einsteinian gravity. Gravitational redshifts have never been measured in environments where gravity is this strong, marking another first and another victory for Einstein. Even in the strongest environment ever probed, the predictions of General Relativity have yet to lead us astray.”
If you want to test Einstein’s General Relativity, you’ll want to look for an effect that it predicts that’s unique, and you’ll want to look for it in the strongest-field regime possible. Well, there’s a black hole at the center of our galaxy with 4 million times the mass of the Sun, and there’s a star (S0-2) that passes closer to it, during closest approach, than any other. In May of 2018, it made this closest approach, coming within 18 billion km (about twice the diameter of Neptune’s orbit) of the black hole, and zipping around at 2.7% the speed of light.
Did Einstein’s predictions for gravitational redshift come out right? You bet they did: 5-sigma, baby! Come get the full, amazing story here!
What Would The Milky Way Look Like If You Could See All Of Its Light?
“When you look at the Milky Way in visible light, you might see billions of stars, but you miss so much more. The human eye is only sensitive to a tiny fraction of the entire electromagnetic (light) spectrum. Each wavelength range showcases a novel view of all that’s out there.”
If you looked out at our galaxy with your eyes and the wavelengths they’re sensitive to alone, there’s an incredible amount of information you’d miss no matter how powerful you became at gathering light or resolving individual objects. That’s because visible light only occupies a narrow range of electromagnetic wavelengths, meaning that what you can see is limited to what emits visible light (stars and some reflective clouds) and constrained by dust, which can absorb all the visible light behind it.
But there are other wavelengths than these, and they reveal a series of fascinating details. What do they all look like? Come get a fuller picture today!
Could The Milky Way Be More Massive Than Andromeda?
“The Milky Way is home to the Sun, our Solar System, and hundreds of billions of stars beyond that. Yet unlike all the other galaxies out there — in our Local Group and in the Universe beyond — we have no good way to view our own galaxy from our position within it. As a result, the full extent of our galaxy, including its total size, mass, matter content, and number of stars, remains mysterious to modern astronomers.
We’ve long looked at the galaxies surrounding our local neighborhood in space and compared ourselves to them. Although there may be more than 60 galaxies present within the Local Group, two of them dominate in every way imaginable: ourselves and Andromeda. We are the two largest, most massive galaxies around, with more stars than all the others combined. But which one is bigger? Long thought to be Andromeda, we’re now finding out the Milky Way might have a chance at being number one.”
It’s 2019, and we still don’t know how massive the Milky Way is, or even whether we’re the most massive galaxy in the Local Group or not. It’s a lot like measuring your eye color: looking out at everyone else, it’s easy to see what color their eyes are. But if you didn’t have a reflection, photograph, or the observations of others, how would you know your own eye color? Well, being trapped within the Milky Way makes measurements notoriously difficult, and we’re only now figuring out how to overcome that obstacle.
It’s not only possible, but even likely that the Milky Way, despite having fewer stars occupying less volume than Andromeda’s, is the most massive galaxy in the Local Group. Come get the full story.
What Was It Like When The Milky Way Took Shape?
“The cosmic story that led to the Milky Way is one of constant evolution. We likely formed from hundreds or even thousands of smaller, early-stage galaxies that merged together. The spiral arms likely formed and were destroyed many times by interactions, only to re-form from the rotating, gas-rich nature of an evolving galaxy. Star formation occurred inside in waves, often triggered by minor mergers or gravitational interactions. And these waves of star-formation brought along increases in supernova rates and heavy metal enrichment. (Which sounds like everyone’s favorite after-school activity.)
These continuous changes are still occurring, and will come to a conclusion billions of years in the future, when all the galaxies of the Local Group have merged together. Every single galaxy has its own unique cosmic story, and the Milky Way is just one typical example. As grown up as we are, we’re still evolving.”
We normally think of events in the past of having occurred at a specific time. Star formation began in the Universe when it was 50-to-100 million years old. The first galaxies formed some ~200 million years after that. The Universe became transparent to visible light 550 million years after the Big Bang, and star formation reached its maximum between 2 and 3 billion years after the Big Bang.
But when did the Milky Way form?
That’s a silly question, as it turns out, because what we know as the Milky Way has been constantly evolving and growing over time. Had we come along billions of years ago, or were we to come along billions of years in the future, our galaxy would be unrecognizable to us.
Here’s the story of how the Milky Way took shape, and what it was like along every step of the way. You might be surprised!
Hubble: Andromeda Is Big, Massive, And Full Of The Stars Our Milky Way Is Missing
“The low-density, outer halo contains stars just as ancient as the Milky Way’s oldest: 13+ billion years of age. Andromeda has stellar streams populating that halo, with a third of those stars just 6-8 billion years old.
This means a major act of galactic cannibalism recently occurred.”
Every few years, a new study comes out claiming that the Milky Way may rival the Andromeda galaxy for the status of largest within our local group. Nonsense! Andromeda is practically double the diameter, contains anywhere from 2.5 to 5 times as many stars, and now there’s evidence that it gobbled up a number of massive galaxies relatively recently. Not only does it have stars just as old as the oldest we’ve ever found in the Milky Way, but we now have evidence that, 6-8 billion years ago, it devoured a large member of our local group entirely, with about a third of Andromeda’s halo stars having formed at around that time. When the Milky Way-Andromeda merger finally comes, there can be no doubt that the remnants of Andromeda will dominate whatever’s left.
Come see an astounding collection of images of our Local Group’s biggest, most massive galaxy, and get a window into what #1 in the Local Group looks like!
Our Local Group Is Being Eaten, And We Just Found The Galactic Leftovers
“Two of the Milky Way’s larger satellites — the Magellanic Clouds — are interacting, forming stars, and on track to be devoured. But one of Andromeda’s satellites is even more interesting. M32 is the smallest galaxy in the Messier catalog: just 6,500 light years across, with ~3 billion solar masses of material. Its dense core houses a multi-million solar mass black hole, extremely unusual for a small galaxy. It suggests that M32 was once much larger, and has been partially cannibalized.”
Here in the local group, we have Andromeda, the Milky Way, and about 60 galaxies that are much smaller. Four of the top 10 galaxies are actually satellites of either the Milky Way or Andromeda. The Large and Small Magellanic Clouds are less than 200,000 light years from the Milky Way, with M32 and M110 in tight orbit around Andromeda. But M32 is no ordinary satellite! In a brand new study published today in Nature Astronomy, scientists took several pieces of evidence and combined them, concluding that M32 is actually a remnant of the third largest galaxy in the Local Group: M32p, which was mostly devoured 2 billion years ago by Andromeda.
In the Universe, all we have left are the survivors, but thanks to some fascinating galactic archaeology, we can reconstruct exactly where it all came from!
This Is Why The Event Horizon Telescope Still Doesn’t Have An Image Of A Black Hole
“Of all the black holes visible from Earth, the largest is at the galactic center: 37 μas.
With a theoretical resolution of 15 μas, the EHT should resolve it.
Despite the incredible news that they’ve detected the black hole’s structure at the galactic center, however, there’s still no direct image.”
Last year, data from the South Pole Telescope, a 10-meter radio telescope located at the South Pole, was added to the Event Horizon Telescope team’s overall set of information. Here we are, though, half a year later, and we still don’t have a direct image of the event horizon for the galactic center’s black hole. There aren’t any problems; the issue is that we have to successfully calibrate and error-correct the data, and that takes time and care to get it right. Science isn’t about getting the answer in the time you have to get it; it’s about getting the right answer in the time it takes to get things right. From that point of view, there’s every reason this is worth waiting for.
The Event Horizon Telescope team is on the right track; here’s where we are right now in our quest to create the first image of a black hole’s event horizon!
The Milky Way Is Hiding Tens Of Thousands Of Black Holes
“This study is of tremendous importance, since it provides us with the first real evidence of what LISA will be looking for, further motivating us to look for these events that, as we now know, must exist. Unlike LIGO’s black holes, these inspiraling events will give us weeks, months, or even years of lead-up time, allowing us to pinpoint exactly where and when we’ll need to look to see these mergers coming. This is the first confirmation of the theory that tens of thousands of black holes ought to exist around supermassive ones at the centers of galaxies, and allows us to better predict how many gravitational wave events we’re likely to see coming from them.“
At the center of our Milky Way, our galaxy houses a supermassive black hole: Sagittarius A*. At four million solar masses, it’s the most massive object in our entire galaxy, while orbiting around it are stars, gas, dust, and many other astrophysical objects. This is a region where new star formation is rampant, and so, in theory, there ought to be many thousands of black holes within just a few light years of Sagittarius A*, some of which ought to be detectable through their emission of X-rays from binary companions. For nearly 20 years, such a detection was elusive, since the flares that occur when black holes absorb large amounts of matter are too rare. But now, using the full suite of archival data from the Chandra X-ray observatory, scientists have found the steady, low-level X-ray emission these systems give off, revealing a population of approximately 10,000 black holes within 3 light years of Sagittarius A*.
The Milky Way is hiding tens of thousands of black holes near the galactic center, and for the first time, we’ve just revealed the surefire signs that they exist.