VV Cephei Star vs Vy Canis Majoris

VV Cephei Star vs Vy Canis Majoris

VV Cephei vs Vy Canis Majoris

Is VV Cephei Star Bigger than Vy Canis Majoris?

When it comes to sheer cosmic size, VV Cephei and Vy Canis Majoris are both stellar giants, but which one takes the crown? Let's dive into their dimensions to find out.

VV Cephei Star

VV Cephei, residing in the constellation Cepheus, is an eclipsing binary system approximately 5,000 light years away from Earth. It consists of a red supergiant, VV Cephei A, and a blue companion. The estimated diameter of VV Cephei A is a staggering 1,050 times that of our Sun, rivaling the orbit of Jupiter. However, the exact size is still debated due to complexities introduced by its binary nature and the obscuring effects of its surrounding disk.

Vy Canis Majoris Star

Vy Canis Majoris, situated in the Canis Major constellation, is an extreme oxygen-rich red hypergiant. Its estimated radius is approximately 1,420 times that of the Sun, reaching the theoretical Hayashi limit. To put it in perspective, if Vy Canis Majoris replaced our Sun, its surface would extend beyond the orbit of Jupiter. The vast circumstellar envelope contributes to the uncertainty in measuring its true size.

VV Cephei Star vs Vy Canis Majoris Size Comparison

Comparing these colossal stars is no small feat due to their intricate natures. VV Cephei A boasts an estimated angular diameter of 0.00638 arcseconds, allowing for a direct calculation of its size. Vy Canis Majoris, on the other hand, has an angular diameter measured at 11.3±0.3 mas. These measurements result in a radius of 1,420±120 R☉. While both stars are giants, Vy Canis Majoris appears to have a larger measured radius.

VV Cephei vs Vy Canis Majoris

VV Cephei Star vs Vy Canis Majoris Temperature

VV Cephei Star

VV Cephei, a remarkable eclipsing binary star system, exhibits complex temperature characteristics. The primary star, VV Cephei A, is identified as an M2 supergiant with an effective temperature of approximately 3,800 K. On the other hand, the secondary star, which is a blue companion obscured by a disk, has a less clearly defined temperature due to the presence of the obscuring material. Ultraviolet absorption lines suggest an early B spectral type for the secondary. The intricate nature of this binary system makes pinning down a single temperature challenging.

Vy Canis Majoris

Vy Canis Majoris, an extreme red hypergiant, presents challenges in precisely determining its effective temperature. Early estimates placed it below 3,000 K, assuming a spectral class of M5. However, more recent calculations propose a temperature as high as 3,650 K, corresponding to a spectral class of M2.5. The inherent variability and pulsations of VY CMa add complexity to accurately defining its temperature. Generally categorized between M3 and M5, it occupies the upper-right hand corner of the HR diagram.

VV Cephei Star vs Vy Canis Majoris Brightness Luminosity

VV Cephei Star

VV Cephei A, the primary star in the binary system, is considered one of the largest stars in the galaxy, with an estimated radius of 1,050 R☉. Its luminosity is approximately 72,881 L☉. The eclipsing nature of the binary system and the presence of a circumstellar disk contribute to variations in brightness. The emission lines from the disk and the complex interplay of the two stars during eclipses result in a dynamic and intriguing brightness profile.

Vy Canis Majoris

Vy Canis Majoris stands out as one of the most luminous stars in the Milky Way. Its bolometric luminosity, calculated from spectral energy distribution, ranges from 200,000 to 560,000 times that of the Sun. The luminosity estimates, although variable, consistently place VY CMa among the most luminous stars. Its extensive circumstellar envelope and complex mass loss contribute to the overall luminosity, making it a captivating object for astronomers.

VV Cephei Star vs Vy Canis Majoris vs Sun

VV Cephei Star vs Vy Canis Majoris vs Sun

VV Cephei Star

VV Cephei A, the primary star, has a mass around 2.5 M☉ or potentially higher, depending on the model. With a radius of 1,050 R☉, it dwarfs the size of our Sun. The secondary, a hot B-type star, adds further complexity to the system. VV Cephei, in comparison to the Sun, showcases the extremes of stellar characteristics, from its massive size to its intricate binary nature.

Vy Canis Majoris

Vy Canis Majoris is a behemoth, with a mass around 17 M☉ and a radius of approximately 1,420 R☉. Compared to the Sun, it is a colossal entity, emphasizing the extreme nature of some stellar objects. The mass loss, strong stellar wind, and pulsations contribute to its unique evolutionary path, distinct from typical stars like our Sun.

VV Cephei Star vs Vy Canis Majoris Compared to Earth

VV Cephei Star

VV Cephei A, with its enormous size and mass, is incomparable to Earth. The binary system's complex interactions, large disk, and significant variations in brightness make it a fascinating but vastly different entity. Its location, approximately 5,000 light years away in the constellation Cepheus, places it well beyond our cosmic neighborhood.

Vy Canis Majoris

Vy Canis Majoris, with a radius of 1,420 R☉, illustrates the extremes that massive stars can reach. If placed at the center of our solar system, its surface would extend beyond the orbit of Jupiter. The scale of VY CMa is beyond terrestrial comprehension, emphasizing the diversity and awe-inspiring nature of celestial objects in our galaxy.

VV Cephei Star Star Diameter Compared to Vy Canis Majoris

The diameter of a star is a crucial factor in understanding its structure and evolution. VV Cephei A's estimated diameter of 1,050 R☉ is remarkable, but Vy Canis Majoris, with a radius exceeding 1,400 R☉, seems to outshine its rival in this celestial showdown.

VV Cephei Star Star Mass Compared to Vy Canis Majoris

Determining the mass of these colossal stars is a challenging task with varying estimates. VV Cephei's traditional model suggests masses around 20 M☉ for both stars, while an alternative model proposes much lower values. For Vy Canis Majoris, its mass is estimated to be around 17±8 M☉. Both stars exhibit significant mass loss, contributing to the complexities in accurate mass determination.

Vy Canis Majoris Star vs VV Cephei

Here's an informative table summarizing key characteristics of VV Cephei and VY Canis Majoris:

Property VV Cephei VY Canis Majoris
Common Name VV Cephei VY Canis Majoris
Designation HD 208816 HD 58061
Type Eclipsing Binary, B[e] Star, Shell Star Red Hypergiant
Distance from Earth Approximately 5,000 light years Approximately 1.2 kiloparsecs
Constellation Cepheus Canis Major
Apparent Magnitude (V) 4.91 Variable, estimated range: 6.5 - 9.6
Orbital Period 20.3 years N/A (Solitary star, no evidence of binary system)
Radius 779.27+77.24−96.32 R☉ (VV Cephei A) Estimated to exceed 2,000 R☉ (variable)
Mass 2.5 or 18.2 M☉ (VV Cephei A), 8 or 18.6 M☉ (VV Cephei B) Not precisely determined, likely over 20 M☉
Luminosity 72,881±16,307 L☉ (VV Cephei A) Estimated to be over 100,000 L☉
Temperature 3,396±35 K (VV Cephei A) Around 3.5 K (surface temperature)
Metallicity −0.06 dex (VV Cephei A) Not specified
Coordinates (J2000) RA: 21h 56m 39.14385s, Dec: +63° 37′ 32.0174″ RA: 07h 22m 58.32877s, Dec: −25° 46′ 03.2357″
Variability Yes (Eclipsing binary, semiregular variations) Yes (Variable, pulsations, eruptions)
Astronomical Implications Valuable for observational studies, complex spectral features Insights into late stages of massive stellar evolution, extreme mass loss

This table provides a concise overview of various properties of both VV Cephei and VY Canis Majoris, showcasing their differences and highlighting their significance in astronomical research.

VV Cephei Star vs Vy Canis Majoris Star

VV Cephei Star

Eclipsing Binary Marvel

VV Cephei, also known as HD 208816, is a captivating eclipsing binary star system nestled in the constellation Cepheus, approximately 5,000 light years from Earth. This celestial wonder is not only an eclipsing binary but also a B[e] star and shell star, making it a multifaceted astronomical phenomenon.

The Dance of Giants

VV Cephei is an eclipsing binary with the third-longest known period, featuring a red supergiant (VV Cephei A) and a companion blue star. During its 20.3-year orbit, primary eclipses totally obscure the hot secondary star for nearly 18 months, showcasing a mesmerizing celestial dance. Only a few binary systems boast longer periods, such as ε Aurigae and AS Leonis Minoris.

Spectral Symphony

This celestial duo exhibits semiregular variations in magnitude, with distinct patterns at various wavelengths. The spectrum of VV Cep can be resolved into two main components, revealing a cool supergiant and a hot small star encircled by a disk. The system's spectral lines, including [FeII] forbidden lines, create a dazzling celestial symphony that changes dramatically during primary eclipses.

Size Conundrum

Estimating the size of VV Cephei A proves challenging due to contradictory data. With an angular diameter of 0.00638 arcseconds, its calculated diameter aligns with the 1,050 R☉ derived from orbital solutions. However, earlier measurements suggested larger values, leading to uncertainty. The secondary's size is even more elusive, hidden behind a substantial disk several hundred R☉ across.

Mass Mystery

Calculating the masses of the binary stars presents a conundrum, influenced by factors like mass loss, orbital changes, and disk obscuration. Traditional models propose both stars having masses around 20 M☉, fitting a luminous red supergiant and an early A main sequence star. However, an alternative model, driven by the 1997 eclipse, suggests drastically lower mass values, challenging conventional wisdom.

Stellar Thermometer

Determining the temperatures of VV Cephei stars adds complexity due to their non-spherical nature. VV Cephei A, identified as an M2 supergiant, boasts an effective temperature around 3,800 K. The secondary star, obscured by the primary's disk, exhibits ultraviolet absorption lines, narrowing its spectral type to early B. Despite its massive size and high mass loss, VV Cephei A isn't classified as a hypergiant.

Celestial Coordinates

Situated in the constellation Cepheus, VV Cephei coordinates (J2000) are approximately 21h 56m 39.14385s (Right Ascension) and +63° 37′ 32.0174″ (Declination). With an apparent magnitude (V) of 4.91, this variable star showcases U−B and B−V color indices reflecting its dynamic nature.

Orbital Insight

VV Cephei's orbit spans 7,430.5 days, with a semi-major axis of 16.2 ± 3.7", eccentricity of 0.346 ± 0.01, and an inclination of 84°. The primary and secondary stars exhibit semi-amplitudes of 19.43 ± 0.33 km/s and 19.14 ± 0.68 km/s, respectively.

Stellar Details

  • VV Cephei A:
    • Mass: 2.5 or 18.2 M☉
    • Radius: 779.27+77.24−96.32 R☉
    • Luminosity: 72,881±16,307 L☉
    • Temperature: 3,396±35 K
    • Metallicity [Fe/H]: −0.06 dex
  • VV Cephei B:
    • Mass: 8 or 18.6 M☉
    • Radius: 13-25 R☉
    • Metallicity: −0.14

Observational Delight

VV Cephei, with its intriguing eclipses, varying spectra, and enigmatic properties, continues to captivate astronomers, offering a celestial playground for observational studies.

Vy Canis Majoris Star

The Colossal Red Hypergiant

VY Canis Majoris (VY CMa), an extreme oxygen-rich red hypergiant located 1.2 kiloparsecs away in Canis Major, stands as one of the largest and most luminous stars in the Milky Way. This massive red supergiant boasts a fascinating array of characteristics and challenges our understanding of stellar evolution.

Stellar Isolation

VY CMa appears to be a solitary star with no evidence of being part of a multiple star system. Its prominent infrared excess makes it a standout object in the galaxy, hinting at a substantial dust shell or heated disk. The star's isolation raises questions about its evolutionary history and the mechanisms governing such immense solitary stars.

Gigantic Stature

Size is one of VY CMa's defining features. Estimates of its radius vary, with some suggesting values surpassing 2,000 times that of the Sun. The star's immense size is particularly challenging to measure accurately due to its complex and dynamic environment, which includes an expansive circumstellar envelope and the effects of mass loss.

Mass Loss Marvel

VY CMa experiences extraordinary mass loss, shedding a significant fraction of its mass into space through powerful stellar winds. This intense mass loss, coupled with its colossal size, contributes to the creation of a dense and intricate circumstellar envelope. The exact mechanisms driving this vigorous mass loss are still under investigation.

Luminosity Labyrinth

Pinpointing VY CMa's luminosity is no straightforward task. Its variability, caused by pulsations and eruptions, leads to challenges in determining a precise luminosity value. Estimates place it among the most luminous stars known, with values exceeding 100,000 times that of the Sun. However, the dynamic nature of the star adds an element of uncertainty to these calculations.

Radiant Temperature

Despite its colossal size, VY CMa does not possess an exceptionally high effective temperature. With a surface temperature much lower than that of the Sun, around 3.5 K, this red hypergiant illuminates the cosmic landscape with its sheer size and radiant energy output. The star's spectral type varies, reflecting the dynamic processes occurring in its extended atmosphere.

Enigmatic Evolution

VY CMa's evolutionary path is shrouded in mystery. While it is commonly accepted that massive stars like VY CMa culminate in explosive supernova events, the specific details of this red hypergiant's fate remain uncertain. Whether it will eventually explode as a supernova or experience a different fate, such as a massive ejection of its outer layers, is a topic of ongoing research and speculation.

Celestial Coordinates

Positioned in the constellation Canis Major, VY CMa's coordinates (J2000) are approximately 07h 22m 58.32877s (Right Ascension) and −25° 46′ 03.2357″ (Declination). Its apparent magnitude varies, underscoring the challenges in precisely determining the brightness of this enigmatic star.

Astronomical Implications

Studying VY Canis Majoris provides valuable insights into the late stages of massive stellar evolution, the impact of massive stars on their galactic environments, and the mechanisms governing extreme mass loss in red hypergiant stars.


Both VV Cephei and VY Canis Majoris stand out as celestial marvels, each offering unique insights and challenges to astronomers. VV Cephei's eclipsing binary nature, intricate spectral features, and enigmatic properties make it a captivating target for observation and study. On the other hand, VY Canis Majoris, with its colossal size, intense mass loss, and uncertain evolutionary fate, pushes the boundaries of our understanding of massive stellar phenomena. Together, these stars contribute to the rich tapestry of celestial objects that fuel scientific curiosity and exploration.

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