Stephenson 2-18 vs Ton 618 vs R136a1

Stephenson 2-18 vs Ton 618 vs R136a1

When it comes to celestial marvels, few things captivate us more than the stars. In the vast cosmic arena, three stellar giants stand out - Stephenson 2-18, Ton 618, and R136a1. Each possesses unique qualities, making them celestial wonders worth exploring. Let's delve into the cosmic depths and compare these astronomical giants.

1. Mass

  • Stephenson 2-18: While the exact mass of Stephenson 2-18 is not specified, red supergiants are known for their massive nature. It is potentially among the largest known stars.
  • Ton 618: Hosts a supermassive black hole with an estimated mass of either 40.7 billion M☉ or 66 billion solar masses, depending on the study.
  • R136a1: Has a mass of 196+34−27 M☉.

2. Luminosity

  • Stephenson 2-18: Exhibits a bolometric luminosity of approximately 630,000 L☉.
  • Ton 618: Shines with a luminosity of 4×10^40 watts, making it one of the brightest objects in the known Universe.
  • R136a1: One of the most luminous stars known, radiating around 4,677,000 L☉.

3. Temperature

  • Stephenson 2-18: An effective temperature of 3,200 K, which is cooler than typical red supergiants.
  • Ton 618: No specific temperature information provided.
  • R136a1: Surface temperature of around 46,000 K, making it one of the hottest stars known.

4. Size

  • Stephenson 2-18: Over forty times the radius of the Sun (42.7 R☉).
  • Ton 618: No specific size information provided.
  • R136a1: Does not have a well-defined visible surface but is over forty times the radius of the Sun.

5. Distance

  • Stephenson 2-18: Around 5.8 kiloparsecs (19,000 light-years) away from Earth.
  • Ton 618: Approximately 18.2 billion light-years from Earth.
  • R136a1: Distance assumed to be around 163,000 light years.

6. Other Notable Features

  • Stephenson 2-18: Classified as a red supergiant, with some indications of extreme red hypergiant characteristics.
  • Ton 618: Acts as a quasar, hosting one of the most massive black holes ever found. It is also associated with an enormous Lyman-alpha nebula.
  • R136a1: A Wolf–Rayet star at the center of the R136 cluster in the Tarantula Nebula, with significant mass loss through a stellar wind.

7. Observational History

  • Stephenson 2-18: Part of the Stephenson 2 cluster discovered by Charles Bruce Stephenson in 1990.
  • Ton 618: Originally noted in a 1957 survey and confirmed as a quasar in 1970.
  • R136a1: Systematically observed since 1960 and later confirmed as a star cluster with the launch of the Hubble Space Telescope.

8. Visibility

  1. Stephenson 2-18:

    1. Limited visibility due to its location, potentially part of an unrelated or foreground group.
  2. Ton 618:

    1. Not visible as it outshines its surrounding galaxy, only detected through its quasar emissions.
  3. R136a1:

    1. Visible as a 10th magnitude object at the core of the NGC 2070 cluster, but requires advanced telescopes for detailed observation.

9. Surroundings

  1. Stephenson 2-18:

    1. Associated with the Stephenson 2 cluster, potentially one of the largest stars in the Milky Way.
  2. Ton 618:

    1. Surrounded by an enormous Lyman-alpha nebula, providing insight into the evolution of massive galaxies.
  3. R136a1:

    1. Core of the R136 cluster, containing over 200 highly luminous stars.

10. Massive Star Characteristics

  1. Stephenson 2-18:

    1. Potentially one of the largest stars known, with an ambiguous evolutionary stage.
  2. Ton 618:

    1. Harbors one of the most massive black holes, contributing to its extreme luminosity.
  3. R136a1:

    1. Wolf–Rayet star with a mass ranging from 215 M☉ to earlier estimates of 315 M☉.

11. Miscellaneous

  1. Stephenson 2-18:
    1. Peculiar spectral energy distribution, raising doubts about its membership in the Stephenson 2 cluster.
  2. Ton 618:
    1. Notable for being a hyperluminous quasar and its association with a colossal Lyman-alpha blob.
  3. R136a1:
    1. Significant contributor to the ionizing flux of the 30 Doradus region, with extreme mass loss through a stellar wind.


Stephenson 2-18 vs Ton 618 vs R136a1 Table


Here is a detailed table comparing Stephenson 2-18, Ton 618, and R136a1:

Property Stephenson 2-18 Ton 618 R136a1
Observation Data
Epoch J2000.0 18h 39m 02.3709s 12h 28m 24.9s 5h 38m 42.39s
Equinox J2000.0 Scutum Canes Venatici Dorado
Right Ascension −06° 05′ 10.5357″ +31° 28′ 38″ −69° 06′ 02.91″
Declination ~M6 Quasar Wolf–Rayet star
Apparent Magnitude (V) 15.2631±0.0092 15.9 12.23
Evolutionary Stage Red Supergiant (possible RHG) Quasar Wolf–Rayet star
Spectral Type ~M6 Not specified WN5h
Distance 18,900 ly (disputed) 18.2 Gly (present comoving distance) 163,000 ly
Absolute Magnitude (MV) N/A N/A −8.18
Mass N/A 40.7 billion M☉ (black hole) 196+34 −27 M☉
Radius N/A N/A 42.7 R☉
Luminosity 630,000 L☉ (bolometric) 4×10^40 watts (quasar) 4,677,000 L☉
Surface Gravity (log g) N/A N/A 3.65 cgs
Temperature 3,200 K (effective) N/A 46,000+1,250 −2,375 K
Rotational Velocity (v sin i) N/A N/A 160 km/s
Age N/A N/A 1.14+0.17 −0.14 Myr
Other Designations
Additional Designations Stephenson 2 DFK 1, St2-18 FBQS J122824.9+312837, QSO 1228+3128 BAT99 108, RMC 136a1, HSH95 3, WO84 1b, NGC 2070 MH 498, CHH92 1, P93 954
Discovery and Visibility
Discovery Discovered in 1990 by C.B. Stephenson First noted in 1957 survey of faint blue stars Discovered in 1960
Visibility ~15,2631±0.0092 15.9 10th magnitude in the Tarantula Nebula
Location Near Stephenson 2 cluster Near the border of Canes Venatici and Coma Berenices In the Large Magellanic Cloud, in the Tarantula Nebula
Distance from Earth ~5.8 kiloparsecs (19,000 ly) 18.2 billion ly 163,000 ly
Binary N/A N/A Possible binary companion
X-ray Emission N/A Detected from R136 Detected from R136
Classification Red Supergiant (possible RHG) Quasar High-luminosity WN5h star

R136a1: The Wolf–Rayet Star in the Cosmic Heart

Location: Constellation Dorado
Distance: 163,000 light-years
Mass: 196 M☉
Radius: 42.7 R☉
Luminosity: 4,677,000 L☉
Temperature: 46,000 K

R136a1 reigns in the Tarantula Nebula, part of the Large Magellanic Cloud. A colossal Wolf–Rayet star, it boasts a mass of 196 solar masses, radiating brilliance at 4,677,000 times that of our Sun. This stellar monarch, only resolved by advanced techniques, continues to mystify astronomers since its discovery in 1960.

The Discovery Journey

In 1960, Radcliffe Observatory astronomers cataloged RMC 136, believing it to be a star system. Later, Hubble's keen eye revealed it as a cluster of over 200 luminous stars. R136a1, its brightest jewel, shines in the far southern celestial hemisphere, visible with telescopes due to its immense distance.

R136a1's Stellar Symphony

This Wolf–Rayet star dazzles with a spectral type of WN5h, signifying a powerful stellar wind. At 46,000 K, it emits extreme ultraviolet radiation, contributing 7% of the ionizing flux to the 30 Doradus region. A possible binary companion and intense mass loss make R136a1 a captivating celestial entity.

Celestial Dimensions

Over forty times the radius of the Sun, R136a1 defies the norms of stellar dimensions. Its immense luminosity, 70% of the Eddington limit, challenges our understanding of stellar evolution.

Ton 618: The Quasar Titan

Location: Constellation Canes Venatici
Redshift: 2.219
Distance: 18.2 Gly
Type: Hyperluminous Quasar
Black Hole Mass: 40.7 billion M☉
Luminosity: 4×10^40 watts

Ton 618 emerges from the cosmic tapestry as a hyperluminous quasar, dwelling near the constellations Canes Venatici and Coma Berenices. Its central supermassive black hole, a cosmic behemoth at 40.7 billion solar masses, fuels its brilliance, outshining its host galaxy.

Unveiling Ton 618's Mysteries

Discovered in 1957, Ton 618's true nature emerged in 1970 through radio emissions. With an absolute magnitude of -30.7, it radiates as brilliantly as 140 trillion suns, placing it among the brightest celestial objects known.

The Quasar's Powerhouse

Ton 618's spectrum reveals broad-absorption lines, indicating intense speeds of infalling material. Its black hole, surpassing 66 billion solar masses in earlier estimates, challenges our notions of supermassive black hole limits.

Lyman-alpha Nebula: A Cosmic Artistry

Ton 618's luminous Lyman-alpha nebula, spanning 100 kiloparsecs, unravels the mysteries of Lyman-alpha emitters. ALMA's observations expose an enormous cloud of gas surrounding the quasar, providing insights into the evolution of massive galaxies.

Stephenson 2-18: The Red Supergiant in Scutum

Location: Constellation Scutum
Distance: 18,900 ly (disputed)
Evolutionary Stage: Red Supergiant
Apparent Magnitude (G): 15.26
Luminosity: 630,000 L☉
Temperature: 3,200 K

Stephenson 2-18 graces the constellation Scutum, standing as a red supergiant or a potential extreme red hypergiant. With disputed distance estimates and peculiar spectral characteristics, this stellar entity challenges our comprehension of stellar evolution.

Stephenson 2-18's Discovery

Discovered in 1990 near the open cluster Stephenson 2, this star's journey has been marked by evolving understanding. Initially deemed unrelated, Stephenson 2-18's place in the cluster remains a subject of debate.

A Luminous Enigma

Stephenson 2-18's luminosity, calculated at 630,000 L☉, perplexes astronomers. Its peculiar Spectral Energy Distribution raises questions about its true nature, hinting at possible higher luminosity and casting doubt on its cluster membership.

A Stellar Crossroads

With an effective temperature of 3,200 K, Stephenson 2-18 diverges from typical red supergiants. If confirmed as an extreme red hypergiant, its existence challenges current evolutionary models. The ongoing debate surrounding its classification adds to the intrigue of this stellar enigma.

Final Thoughts

In this stellar showdown, R136a1, Ton 618, and Stephenson 2-18 each present a cosmic spectacle. R136a1, a Wolf–Rayet star, reigns in the Tarantula Nebula, pushing the boundaries of stellar dimensions. Ton 618, a hyperluminous quasar, captivates with its supermassive black hole and cosmic artistry. Stephenson 2-18, a disputed red supergiant, stands at a stellar crossroads, challenging our understanding of stellar evolution.

As we gaze into the cosmic tapestry, these celestial giants remind us of the vastness and diversity of the universe. With each discovery, we inch closer to unraveling the cosmic mysteries that shroud these stellar wonders, unveiling the secrets that lie within the heart of the cosmos.

Back to blog