Black holes are some of the most mysterious and powerful objects in the universe. They are formed when massive stars collapse at the end of their lives, and their gravitational pull is so strong that nothing can escape from them – not even light. Black holes warp spacetime around them and can literally swallow stars whole. But not all black holes are created equal – some are much larger and more massive than others. So which black hole is the current record holder for the largest ever observed? Let’s take a deep dive into the mysterious world of these dark giants.
What is a Black Hole?
A black hole is a region of spacetime where gravity is so strong that nothing can escape from it, including light. The boundary at which light and matter can escape is called the event horizon. Anything that crosses this threshold is pulled into the black hole and cannot get out. The immense gravitational field of a black hole is created by matter that has collapsed into an extremely dense state.
For a black hole to form, the core of a very massive star (at least 20-25 times more massive than our sun) must collapse. This collapse happens when the star runs out of fuel for nuclear fusion and can no longer withstand its own gravitational force. As the star’s core implodes, it forms a singularity – a point where density and spacetime curvature become infinite. Around this singularity, a black hole’s event horizon forms. Anything that enters this horizon is destined to fall into the singularity and be crushed into infinite density. Even light cannot escape, which is why black holes are invisible.
Properties of Black Holes
Black holes can be completely characterized by only three properties:
- Mass – The total mass contained within the event horizon
- Charge – The total electric charge contained within the event horizon
- Angular Momentum – The rotation of the black hole
These three properties are known as the no-hair theorem proposed by physicist John Archibald Wheeler in the 1960s. Based on these three traits, it is not possible to distinguish between two black holes. According to general relativity, no other characteristics are needed to describe a black hole.
How Do Black Holes Form?
There are a few key pathways that can lead to the formation of a black hole:
Gravitational Collapse of a Massive Star
As mentioned earlier, this is the most common way black holes form. At the end of a massive star’s life, it runs out of fuel for nuclear fusion and can no longer produce energy to counteract gravity. When this happens, the star’s core rapidly collapses under its own immense weight and forms a black hole. These are known as stellar black holes.
Collapse of Dense Clusters
In extremely dense regions of space like globular clusters or galactic centers, black holes can form from the merger and collapse of stars and gas clouds. As these tightly packed regions continue to densify, stellar collisions can trigger the formation of an intermediate mass black hole.
Supernovae
When a star over 20-25 solar masses explodes in a supernova, it may leave behind a black hole remnant containing the core of the progenitor star. This happens when the energy of the explosion is not enough to completely overcome the gravitational collapse.
Primordial Black Holes
These are hypothetical black holes that may have formed in the early universe shortly after the Big Bang, from the collapse of extremely dense regions. However, primordial black holes have not been observed, though some candidates have been proposed.
Types of Black Holes
Black holes can be classified into three main categories based on their mass:
Stellar Black Holes
These are the smallest black holes with masses ranging from about 5 to several tens of solar masses. They form from the collapse of individual stars at the end of their life cycles. There are likely hundreds of millions of stellar black holes in the Milky Way galaxy alone.
Intermediate Black Holes
Ranging from hundreds to hundreds of thousands of solar masses, these black holes occupy the mass range between stellar and supermassive black holes. They may form from the collapse of dense stellar clusters or the merger of many smaller black holes. However, definitive evidence for intermediate mass black holes is still lacking.
Supermassive Black Holes
These monstrous black holes have masses equal to millions to billions of Suns. Supermassive black holes lie at the center of almost every large galaxy, including our own Milky Way. It is believed galaxies and supermassive black holes at their cores evolve and grow together through cosmic time.
The Largest Known Black Holes
Now that we have reviewed some black hole basics, let’s discuss some record breakers when it comes to mass. Here are some of the largest known black holes found to date:
TON 618
This black hole sits at the heart of a very bright quasar called TON 618 located 10.4 billion light-years from Earth. Initial measurements based on the quasar’s incredible luminosity indicated TON 618 could be one of the most massive black holes ever found, with an estimated mass of 66 billion Suns. However, more recent calculations in 2021 estimate the black hole has a mass closer to 150 billion solar masses, over 1,000 times more massive than the supermassive black hole in our Milky Way. If confirmed, TON 618 would be the largest known black hole in the observable universe.
S5 0014+81
Located 12.1 billion light-years from Earth, this supermassive black hole weighs in at 40 billion solar masses, based on near-infrared observations of its quasar host galaxy. Before TON 618, S5 0014+81 was regarded as potentially the most massive known black hole for many years after its initial discovery in 2008.
Sagittarius A*
This supermassive black hole sits at the heart of our very own Milky Way galaxy, coming in with a mass of 4 million solar masses. Sagittarius A* was first detected through observations of the motion of stars near the galactic center in 2002. In 2022, astronomers were able to image Sagittarius A* directly for the first time.
Holm 15A
Located at the center of the Holmberg 15A galaxy 700 million light-years away, this black hole weighs an estimated 40 billion solar masses. It was discovered in 2014 when astronomers found a large reservoir of ionized gas surrounding it, fueling its growth. Holm 15A highlights that extremely massive black holes were already in place less than 1 billion years after the Big Bang.
| Black Hole Name | Estimated Mass (Solar Masses) | Distance from Earth |
|---|---|---|
| TON 618 | 66 billion – 150 billion | 10.4 billion light-years |
| S5 0014+81 | 40 billion | 12.1 billion light-years |
| Holm 15A | 40 billion | 700 million light-years |
| Sagittarius A* | 4 million | 27,000 light-years |
Finding Black Holes
Since black holes themselves emit no light, how do astronomers find these invisible giants? There are a few key methods:
Accretion Disks
As surrounding material gets accelerated into the black hole, it heats up and emits intense X-ray radiation before crossing the event horizon. This infalling material forms a swirling accretion disk which can be detected.
Gravitational Lensing
According to general relativity, black holes warp spacetime. This means they can gravitationally lens and distort light from objects behind them, allowing black holes to be detected from their lensing effects.
Stellar Orbits
By tracking the orbits of stars near the centers of galaxies, astronomers can detect the gravitational tug of black holes and estimate their masses. This method confirmed the presence of the Milky Way’s central black hole.
Gravitational Waves
When black holes merge, they release ripples in spacetime called gravitational waves. Detectors like LIGO can trace these waves back to their sources. The first black hole merger was detected through gravitational waves in 2015.
Conclusion
The current record holder for the largest known black hole appears to be TON 618, with an estimated mass of 150 billion Suns – over 1,000 times more massive than Sagittarius A*, the black hole at our galaxy’s center. However, giant black holes like TON 618 and S5 0014+81 are extremely distant and there are still uncertainties around their exact sizes. Additional observations and improved measurement techniques will help shed more light on just how massive the biggest black holes in our universe can grow. Theoretical predictions suggest there is no limit to black hole growth – they can literally swallow stars and other black holes to become as large as billions of solar masses or more. The hunt continues to find more black hole behemoths that push the limits of our cosmological models.