TON 618 is one of the most extreme objects known to astronomers, a hyperluminous quasar powered by a supermassive black hole of staggering proportions. Discovered during a 1957 survey of faint blue stars, its true nature as a quasar—an intensely bright, distant galactic core—was confirmed in the 1970s. It represents one of the most massive black holes ever observed in the universe. This article explores whether this cosmic titan can be seen from Earth, what its classification means, and how its immense size compares to our own solar system.
Visual Accessibility and Equipment Required
The short answer to whether TON 618 can be seen is that it is impossible to view with the unaided eye, but it is technically possible to capture with advanced amateur equipment under ideal circumstances. This difficulty is due to the object’s apparent magnitude, a measure of how bright an object appears from Earth, which is estimated to be around 15.9. For comparison, the very faintest stars visible to the naked eye under perfect, dark-sky conditions have an apparent magnitude of about 6.5.
Observing TON 618 visually requires an optical instrument, but even small telescopes will not suffice. The object is so faint that it sits outside the visual capability of many backyard telescopes, even those with large apertures. To reliably see it, one would need a telescope with a mirror or lens diameter of 16 inches or more, and even then, it would appear as a tiny, faint, star-like point.
The best way for amateurs to detect TON 618 is through astrophotography, which involves long-exposure imaging using a sensitive CCD camera attached to a medium-to-large aperture telescope. Capturing its light requires gathering photons for hours, sometimes over multiple nights, to accumulate enough light to resolve the faint point against the background. Light pollution is a significant obstacle, meaning successful imaging almost always requires access to exceptionally dark skies far from city lights.
Defining the Hyperluminous Quasar
TON 618 is classified as a quasar, which is a type of Active Galactic Nucleus (AGN). An AGN is the compact region at the center of a galaxy where a supermassive black hole is actively feeding on surrounding gas and dust. The intense gravitational and frictional forces within the surrounding accretion disk heat the material to millions of degrees, causing it to emit enormous amounts of radiation across the electromagnetic spectrum.
The term hyperluminous is used because TON 618 is one of the brightest objects known in the universe. It shines with a luminosity estimated to be 140 trillion times that of our Sun, outshining the entire galaxy in which it resides. This brilliance is a direct result of the immense rate at which its central black hole consumes matter.
This quasar’s immense distance means the light we observe has traveled for approximately 10.8 billion years to reach us. Because of the expansion of the universe, the object’s current distance is calculated to be even greater, around 18.2 billion light-years. Essentially, when we view TON 618, we are looking back in time to an era when the universe was less than a third of its current age, providing a glimpse into the conditions of the early cosmos.
The Immense Scale of the Central Black Hole
The engine powering this hyperluminous quasar is a supermassive black hole estimated to have a mass of approximately 66 billion times the mass of the Sun. This mass is so great that it pushes the object into a proposed classification known as an ultramassive black hole. The total mass of all the stars in our entire Milky Way galaxy combined is less than this single black hole.
To grasp this scale, one must consider the size of its event horizon, the boundary beyond which nothing, not even light, can escape. The Schwarzschild radius of the TON 618 black hole is so large that its event horizon spans a diameter of roughly 390 billion kilometers. This means the black hole’s diameter is about 40 times larger than the distance from the Sun to Neptune, encompassing a volume much greater than the entire orbit of our outermost major planet.
The size difference is stark even when compared to the black hole at the center of our own galaxy, Sagittarius A (Sgr A). TON 618 is over 15,000 times more massive than Sgr A. The intense gravitational pull created by this mass causes the infalling material in the accretion disk to swirl at tremendous speeds, with gas velocities measured at over 10,000 kilometers per second.
Locating the Quasar in the Night Sky
For those attempting to locate TON 618, the object resides in the northern celestial hemisphere near the border of two constellations: Canes Venatici (The Hunting Dogs) and Coma Berenices. These constellations are best observed from the Northern Hemisphere during the spring months, making that the ideal time for viewing attempts.
Pinpointing the exact location requires precise celestial coordinates, which serve as the object’s astronomical address. The quasar is situated at a Right Ascension of 12 hours, 28 minutes, and 24.9 seconds, and a Declination of positive 31 degrees, 28 minutes, and 38 seconds. These coordinates are necessary because the quasar appears visually indistinguishable from any other faint star in the field of view.
Amateur astronomers typically use computerized Go-To telescope mounts or specialized star-charting software to input these coordinates and accurately point their instruments.