Sagittarius A* (pronounced Sagittarius A-star or Sagittarius A-sub-star) was first discovered using radio telescope data in 1974 and has been measured to be 25,000 light years away from earth, making it the center of the Milky Way galaxy and one of the largest black holes known to exist. Because of its large mass, Sagittarius A* was originally thought to be a supermassive star but was later determined to be a supermassive black hole because of its intense gravitational field.
Things to Know About Sagittarius A*
It’s just a black hole with a lot of matter around it. At its center is Sagittarius A*, an energetic, dense object that possesses a mass equivalent to four million Suns. It measures about 15 billion kilometers (9.3 billion miles) across—about 70 times larger than Earth’s orbit around our Sun—and has roughly four million times as much mass as our parent star. And while we can’t see it directly, we know it’s there because of all the gas and dust orbiting around it. If you were floating in empty space near Sagittarius A*, you would feel gravity pulling you toward it—but not nearly as strongly as if you were standing on Earth or any other planet in our solar system. That’s because it doesn’t have enough gravitational pull for us to notice from such a great distance away. In fact, if you could somehow stand on top of Sagittarius A*, your feet wouldn’t be touching anything! But, again: You couldn’t actually do that; even light takes thousands of years to travel from one side of Sagittarius A* to another. So we don’t actually know what’s going on inside! There are some ideas, though. We think it might be made up of two stars that collided billions of years ago. Or maybe it was born when a massive star ran out of fuel and collapsed under its own weight millions or billions of years ago. There are some other possibilities, too. We’ll probably never know for sure until we send something out there to check things out…which might happen someday soon!
Mythology Behind Sagittarius A*
Sagittarius A* is a supermassive black hole (black hole mass = 4.3 million times that of our sun, or 10^8 solar masses) at our galaxy’s core. Sagittarius A* was one of two new black holes discovered in 2010 using data from NASA’s orbiting Chandra X-ray observatory and ESA’s XMM-Newton satellite. The other black hole is located near the center of M87, another large spiral galaxy. These discoveries were made possible by studying glitches—temporary changes in brightness—in x-rays coming from these galaxies. Glitches occur when gas falls toward a central black hole but does not fall directly into it because there are other stars nearby. Instead, some of that gas forms an accretion disk around the black hole. As more and more matter accumulates on top of that disk, it heats up to millions of degrees Celsius, emitting x-rays as observed by Chandra. When enough gas has piled up on top of an accretion disk, it can create enough pressure to push away other surrounding gas. This pushes outwards on the inner edge of the accretion disk closest to the black hole, causing it to brighten temporarily before plunging back down onto itself and creating a glitch. By studying how long these glitches lasted, astronomers could estimate how much material was present in each system’s accretion disks.
What Is a Supermassive Black Hole?
Sagittarius A* is a supermassive black hole that’s located in an area at our galaxy’s center called Sagittarius A. This black hole has an estimated mass equal to 4 million Suns, and its diameter—determined by measuring the strength of its gravitational pull on nearby stars—is about 25 million kilometers (15.5 million miles). It makes up about 0.1 percent of our galaxy’s total mass, but it contains as much matter as 4 million Suns! That means it’s incredibly dense: one teaspoon of Sagittarius A* would weigh more than 1 billion tons. For comparison, Earth weighs in at around 6 sextillion tons. And don’t worry; we won’t fall into it anytime soon. At its closest point, which happens every 16 years or so, Sagittarius A* is still 26,000 light-years away from us—or about 80 times farther away than Pluto. But even though it’s not particularly close, Sagittarius A* does have an impact on our lives. In fact, it influences everything from star formation to galactic evolution. So what exactly is a supermassive black hole? How did scientists discover Sagittarius A*, and why is it important? Let’s take a look at some facts and figures about our galaxy’s central hub.
How Big is Sagittarius A*?
Sagittarius A* is 4.3 million times heavier than our Sun and 26,000 light years away. It’s a supermassive black hole that has an estimated mass of 4 million solar masses, or roughly three-quarters of a billion times heavier than Earth and seven times more massive than our Milky Way galaxy. In other words: it’s really big. And it’s right in our galactic backyard! Astronomers can study it with relative ease because it doesn’t lie behind any gas or dust clouds; we can see right into its center. This makes it easier to understand how supermassive black holes form and what they do to galaxies—information that will help us better understand how galaxies form and evolve over time. So next time you’re stuck in traffic (in LA), just remember: you’re not far from one of the biggest things in existence. No wonder everyone else is on their phone. We’re all starstruck by Sagittarius A*.
How did something so big get to be so massive? Well, it took some help. As I mentioned before, supermassive black holes are usually found near the centers of galaxies. However, Sagittarius A* is different. Sometimes multiple supermassive black holes interact within a single galaxy cluster and start orbiting each other; after millions or billions of years these pairs merge together to create even bigger systems like these ones . Why does that happen?
Where Is Sagittarius A* Located?
Sagittarius A* (pronounced A-star) is a supermassive black hole. It’s located in the center of our Milky Way galaxy and is approximately 25,000 light years from Earth. To give you a sense of how big that distance is: Light takes 8 minutes to travel one light year. So, if you looked at something 25,000 light years away with your naked eye it would appear as it did 25,000 years ago. If you wanted to see what something looked like 100,000 years ago all you would need to do is point your telescope toward Sagittarius A*. How Do We Know It’s There?: Since its discovery in 1974 scientists have been studying Sagittarius A* and trying to determine just how massive it really is. In 2012 astronomers used data gathered by NASA’s Chandra X-ray Observatory to determine that it has an estimated mass of 4 million times that of our Sun. In other words, if you placed Sagittarius A* in our Solar System it would extend out past Jupiter and Saturn. That is an incredibly large amount of mass packed into a very small space. Is It Really a Black Hole?: Yes! By definition, a black hole is an object whose gravity is so strong that nothing can escape—not even light. This means that once anything crosses the event horizon—the invisible boundary surrounding a black hole beyond which nothing can escape—it will never be seen again. Because we can’t observe anything inside of Sagittarius A*, we don’t know exactly what goes on there but we do know it meets all criteria for being called a black hole.
How Did We Discover It?
Sagittarius A* (pronounced A-star and known colloquially as Sgr A*) was first observed in 1994 by an astronomer using NASA’s orbiting Chandra X-ray Observatory. Astronomers have made many observations of Sgr A* since then, but most came from Earth-based telescopes until 2015. In that year, astronomers launched a new space telescope: NuStar, short for Nuclear Spectroscopic Telescope Array. Unlike previous telescopes, NuStar could observe high-energy X-rays—those energetic enough to penetrate through gas and dust clouds surrounding Sgr A*. It found that these clouds were not centered on one object, but rather two—and one of them is likely to be our galaxy’s supermassive black hole. What Does it Look Like?: We can see black holes by how they affect their surroundings, rather than by direct observation. So far, we’ve seen that Sgr A* has a mass about 4 million times greater than our sun. That means its gravitational pull is so strong that light itself cannot escape its surface; therefore, we cannot directly observe it. But based on what we know about other black holes, we can make some educated guesses about what it might look like. For example, we think Sgr A* is smaller than a few dozen solar masses because otherwise it would have already collapsed into a singularity. If you’re interested in learning more about black holes and how they work, check out our post on How Black Holes Work .
Does it have an Event Horizon?
Sagittarius A* is a black hole that marks the center of our galaxy. Although we cannot see it, astronomers know it exists because they can measure its effects on nearby stars and clouds of gas. When a star gets too close to a black hole, tidal forces rip it apart in what’s known as a tidal disruption event. This causes an increase in brightness that allows scientists to detect these events using telescopes like NASA’s Swift satellite. Tidal disruption events are thought to be responsible for creating some of the heaviest elements in our universe—including gold and platinum! In order to observe Sagittarius A*, scientists must use different methods, including watching stars orbit around it or detecting gamma-ray bursts coming from within its boundaries. We can also calculate how much mass is contained within a certain radius of Sgr A*. This tells us how massive Sagittarius A* must be: approximately 4 million times more massive than our sun. If you were located near Sgr A*, you would feel about 3 times heavier than normal due to the stronger gravitational pull caused by its immense mass. But don’t worry; there is no chance that you will ever find yourself so close to such a powerful object. It is 26,000 light years away from Earth, which means it takes light 26,000 years to travel between Earth and Sgr A*. Light emitted from Sgr A* today won’t reach us until 2043!
Did Astronomers Predict its Existence?
Although people have known for centuries about black holes, one of the most elusive concepts in astrophysics is that a supermassive black hole lies at our galaxy’s center. Astronomers can’t observe it directly because it swallows light and everything around it. However, they did predict its existence based on Einstein’s theory of general relativity: when two stars orbit each other so closely that their gravitational pull causes them to merge into one star, what happens to all that mass? It has to go somewhere. And if it doesn’t go anywhere else, then it must collapse into a singularity—an object with infinite density where gravity becomes infinitely strong. We now know that singularities are one type of black hole, but there are several types. Sagittarius A* is thought to be an intermediate-mass black hole (IMBH), which means it weighs between 100,000 and 10 million times more than our Sun. That’s still pretty small compared to supermassive black holes like Sagittarius A*, though. These weigh as much as 50 billion Suns!
Why It’s Important to Study
Astronomers have long been interested in Sagittarius A*, also known as SgrA*, because it’s believed to be a supermassive black hole with a mass equivalent to 4 million suns. But why is that interesting? Well, understanding how black holes form, grow, and interact with other celestial objects can help us better understand how galaxies evolve and change over time. Without further ado, here’s everything you ever wanted to know about one of our Milky Way’s most intriguing objects. (Spoiler: It’s not just a big, empty space.) [content block] Why It’s Important to Study: As far as we know, every galaxy has a central black hole—it’s even theorized that these objects play an important role in shaping galactic structure by feeding on surrounding stars and gas. So what makes Sagittarius A* special? For starters, it’s huge! In fact, astronomers estimate its mass to be roughly 3.7 million times greater than that of our Sun. But where does all that matter come from? In short, material falling into a black hole heats up and radiates light before disappearing forever. This process generates large amounts of energy—so much so that SgrA* is actually bright enough for us to see without optical aid!
