When astrophysicists map the most extreme gravitational anomalies in the cosmos, two titans dominate the conversation: the central black hole in the Phoenix Cluster (often referred to as Phoenix A) and the hyperluminous quasar TON 618. Comparing these two behemoths reveals the absolute upper limits of mass and scale for objects in our universe. While TON 618 spent years dominating public imagination as the undisputed heavyweight champion, newer cluster models and observational data place Phoenix A even higher on the cosmic scale. Understanding how they stack up against each other requires looking closely at their mass, physical dimensions, and how they challenge current models of galactic evolution.
Mass and Scale: The Numbers Behind the Giants
To grasp the scale of these objects, standard stellar-mass black holes—which typically range from 5 to 100 times the mass of our Sun—look like microscopic dust specks. Both Phoenix A and TON 618 belong to an ultra-rare class known as ultramassive black holes (UMBHs), possessing tens of billions of solar masses.
TON 618 is a hyperluminous quasar powered by a massive black hole clocked at roughly 66 billion solar masses. To visualize that, imagine taking 66 billion stars the size of our Sun and crushing them into a single gravitational singularity. Its sheer mass equals that of a small galaxy, shining with the brilliance of trillions of suns as matter spirals frantically into its event horizon.
On the other side of the cosmic ledger sits Phoenix A, residing in the center of the Phoenix Galaxy Cluster. Recent astrophysical models and cluster X-ray data estimate Phoenix A's mass at an astonishing 100 billion solar masses. If these estimates hold true, Phoenix A outweighs TON 618 by a wide margin, making it one of the most massive single objects ever calculated by astronomers. For additional details on the matter, in-depth analysis can be read on The New York Times.
Event Horizon Dimensions and Physical Reach
Mass dictates size when it comes to black holes. The radius of a black hole's event horizon—the threshold beyond which nothing, not even light, can escape—grows in direct proportion to its mass.
Because TON 618 weighs in at 66 billion solar masses, its Schwarzschild radius stretches across an immense distance. Its event horizon spans roughly 1,300 astronomical units (AU) in radius, meaning its diameter is about 2,600 AU. For context, one AU is the distance from the Earth to the Sun. Pluto sits roughly 40 AU from the Sun. TON 618's event horizon is so large that light takes days to travel from one side of the shadow to the other.
Phoenix A dwarfs even this scale. With an estimated 100 billion solar masses, its event horizon is calculated to be roughly 4,000 AU across (about 2,000 AU in radius). If you dropped Phoenix A into the center of our solar system, its event horizon would swallow the orbits of all the inner planets, the asteroid belt, the gas giants, and stretch far out past Pluto, engulfing the distant Oort cloud in the process.
Formation and Cosmic Environment
A major question in modern astrophysics is how these monsters grew so large so quickly, especially in the early universe. Both objects exist at immense cosmological distances, meaning we see them as they were billions of years ago.
TON 618 is located roughly 10.4 billion light-years away, shining as a quasar powered by a colossal accretion disk of gas and dust. It formed at a time when the universe was densely packed with primordial matter, allowing its central engine to feed at staggering rates.
Phoenix A is located in the Phoenix Cluster, roughly 5.7 to 8.5 billion light-years away. Unlike quiescent clusters, the Phoenix Cluster features a ferocious starburst region where stars are born at thousands of times the rate of our Milky Way. The central black hole interacts dynamically with this cooling intracluster gas, maintaining a violent cycle of feeding and feedback that has fueled its unprecedented growth since shortly after the Big Bang. According to NASA astrophysics data, understanding these feedback loops is essential for explaining how host galaxies and their central black holes evolve in tandem.
Common Misconceptions About Ultramassive Black Holes
When exploring objects like TON 618 and Phoenix A, several common myths often circulate in popular science discussions.
- They are not cosmic vacuum cleaners: A black hole only pulls in matter that crosses its event horizon or strays too close. If our Sun were magically swapped with TON 618, Earth wouldn't get sucked in; it would continue orbiting the exact same gravitational path, though it would plunge into eternal darkness.
- Density varies by scale: While the singularity at the core is infinitely dense, the average density of an ultramassive black hole drops dramatically as it grows. In fact, a black hole the size of Phoenix A has an average density lower than water, simply because its volume inside the event horizon is so gargantuan.
- They do not live forever: Through a process known as Hawking radiation, theorized by physicist Stephen Hawking, black holes slowly lose mass over deep time. However, for giants like TON 618 and Phoenix A, that evaporation process will take timescales trillions of times longer than the current age of the universe.
Frequently Asked Questions
Is Phoenix A larger than TON 618?
Yes. Current estimates suggest Phoenix A possesses roughly 100 billion solar masses compared to TON 618's 66 billion, giving Phoenix A a larger event horizon and making it the heavier of the two.
Could these black holes fit inside the Milky Way?
If placed where our galactic center resides, both would easily fit inside the inner halo of our galaxy, but their physical event horizons would consume vast stretches of space. TON 618's horizon spans hundreds of billions of kilometers, dwarfing entire solar systems. You can read more about galactic structures via the European Space Agency.
How do black holes get this big?
They grow through the continuous accretion of gas, dust, and cosmic material over billions of years, as well as through violent mergers with other massive black holes during galactic collisions.
Will TON 618 or Phoenix A ever swallow their host galaxies?
No. Even ultramassive black holes only occupy a tiny fraction of their host galaxy's total volume. While they heavily influence star formation through energetic winds and radiation, they don't consume everything in their host systems.
