The Largest Star in the Universe Is 1,700x Bigger Than Our Sun

By: Clarissa Mitton  | 
Pictured here is Betelgeuse, a red supergiant 700 times the size of Earth's sun. The largest known star in the universe is more than twice that size, 1,700 times larger than our sun. Javier Zayas Photography / Getty Images

In the vast night sky, where countless stars vie for attention, one colossus reigns supreme as the largest star in the universe. Situated thousands of light-years from Earth, this celestial giant's sheer magnitude challenges our understanding of stellar physics.

Most stars in our galaxy might appear as mere specks of light, and even the most massive star isn't as bright as distant stars like Betelgeuse or Sirius. Read on to learn more about UY Scuti, the largest star we know of, and other such stars.


Is the Sun the Largest Star?

If you don't know much about space, your first guess might be that the sun is the biggest star in the universe. Despite its central role in our solar system and its undeniable brightness that bathes the Earth in light, the sun, when compared to the vast tapestry of stars in space, is far from holding the title of the largest star.

Through the lens of science, the sun is classified as an average, medium-sized star, neither exceptionally large nor particularly small compared to the colossal stars scattered throughout the cosmos. Its prominence in our sky owes more to its proximity to Earth than to its physical stature.


So, if the sun isn't the biggest star, who holds the title?

Unveiling UY Scuti: The Biggest Star

UY Scuti holds the prestigious title of the largest known star, a red supergiant star that dwarfs even the most luminous stars in our night sky. As a hypergiant star, UY Scuti's immense size is almost incomprehensible, with a radius about 1,700 times larger than that of our Sun.

This means if UY Scuti were placed at the center of our solar system, it would engulf the orbits of Mercury, Venus, Earth, Mars and potentially even Jupiter, illustrating the colossal scale of this celestial behemoth.


The sheer magnitude of UY Scuti places it in a league of its own, far surpassing other notable stars such as Alpha Orionis, better known as Betelgeuse, in sheer size. While Betelgeuse is often celebrated for its enormity and brightness, UY Scuti's dimensions make it a giant among giants in the cosmic landscape.

This red supergiant star's vast expanse not only challenges our understanding of stellar evolution but also captivates the imagination, offering a stark perspective on the enormity of the universe and our place within it.


Who Discovered UY Scuti?

The discovery of UY Scuti, the universe's largest known star, is credited to astronomers at the Bonn Observatory in Germany. In 1860, through meticulous observations using the observatory's powerful telescopes, these astronomers first cataloged UY Scuti as part of their sweeping survey of the night sky.

Situated in the constellation Scutum, the star's initial identification did not immediately reveal its extraordinary size. It was only with subsequent observations and advancements in astrophysical techniques that the true scale of UY Scuti began to emerge.


The breakthrough in understanding UY Scuti's immense dimensions came much later, with the advent of more sophisticated astronomical instruments and methods. By analyzing the star's light and movements through space, astronomers were able to deduce its size, classifying it as a red supergiant and eventually recognizing it as the largest star in terms of physical size.

This discovery was a testament to the evolution of observational astronomy and the relentless pursuit of knowledge about the cosmos.


How Do Scientists Measure the Size of a Star?

Scientists use a variety of sophisticated methods to measure the size of a star, blending the art of observation with the precision of modern science. This process involves collecting data from telescopes equipped to peer deeply into the cosmos, beyond the dust and gas that scatter throughout the Milky Way.


One primary technique used is interferometry, which combines the light received from multiple telescopes to create a more detailed image of a star. This method allows scientists to resolve the star's apparent size with remarkable accuracy, even when it lies thousands of light years away.


Additionally, the measurement of a star's brightness, or luminosity, provides crucial clues about its size. By understanding the intrinsic brightness of a star and comparing it to its observed brightness from Earth, scientists can infer its distance and size. This calculation takes into account the light absorbed and scattered by interstellar dust, ensuring the data reflects the star's true characteristics.

Advances in technology and the science of spectroscopy, which analyzes how light interacts with matter, further refine these measurements by offering insights into the star's temperature, composition, and motion, all of which are integral to determining its size.

Specialized Telescopes

Furthermore, the Hubble Space Telescope played a pivotal role in this endeavor, offering previously unparalleled clarity and depth in observing distant stars. (The James Webb Space Telescope is now the latest and greatest in this field.)

The Hubble's ability to capture high-resolution images was crucial in refining measurements of star sizes, including those of very massive stars, by penetrating the dust and gas of the Milky Way to reveal the cosmos beyond.

While this is an oversimplified explanation, this gives you a brief glimpse at how astronomers catalog the stars in the universe with astonishing precision.


Other Massive Stars

Exploring the cosmos reveals a roster of very massive stars, each with unique characteristics and contributions to our understanding of stellar phenomena. Here's a look at some of the most massive stars:

  • WOH G64: Located in the Large Magellanic Cloud, WOH G64 is a red supergiant star enveloped in a thick cloud of dust, making it one of the largest known stars by volume.
  • WOH 5170: Another luminary of the Large Magellanic Cloud, WOH 5170 stands out for its sheer size and is considered among the largest stars discovered in this satellite galaxy of the Milky Way.
  • RSGC1-F01: A member of the RSGC1 star cluster, this red supergiant is one of the most massive stars in our galaxy, showcasing the diversity of stellar evolution within dense stellar families.
  • HD 269551: This star is a notable member of the Large Magellanic Cloud, distinguished by its significant mass and brightness, offering insights into the lifecycle of massive stars.
  • VY Canis Majoris: Often cited among the largest stars known, VY Canis Majoris is a red hypergiant in the constellation Canis Major, renowned for its size and the complex nebula that surrounds it.
  • HD 12463: Situated in the Milky Way, HD 12463 is a massive star that contributes to the rich tapestry of our galaxy's stellar population, exemplifying the characteristics of significant stellar mass and luminosity.
  • CM Velorum: A notable star in the constellation Vela, CM Velorum exhibits characteristics typical of very massive stars, including a high rate of mass loss and a vast luminous output.
  • AH Scorpii: A red supergiant located in the constellation Scorpius, AH Scorpii stands out for its size and the variability of its brightness, making it a subject of interest among astronomers.
  • HV 888: This star, found in the Large Magellanic Cloud, adds to the collection of massive stars studied by astronomers, offering more data on the physical properties and evolution of significant stellar bodies.

Each of these stars provides a unique window into the life cycle of the universe's most massive stars, from their formation to their eventual demise, enriching our understanding of the cosmos.


How Monster Stars Form

The formation of monster stars is a process that begins within the cold, dense cores of giant molecular clouds scattered throughout galaxies, including our own Milky Way and the nearby Large Magellanic Cloud. These clouds of gas and dust become the nurseries for star formation when regions within them collapse under their own gravity.

For a massive star to form, a significantly larger amount of material is required than for average stars. As these regions collapse, they heat up and eventually ignite nuclear fusion in their cores.


The process is more complex for supermassive stars, as their formation likely involves the merging of smaller stars in dense stellar environments or through the accretion of exceptionally large amounts of material from their surroundings.

These processes result in the birth of massive star formation, creating the luminous, big stars that dominate their cosmic neighborhoods with their intense brightness and powerful winds, shaping the structure of their host galaxies.


What Is the Brightest Star In the Universe?

The title of the brightest star in the universe, in terms of intrinsic luminosity, belongs to the luminous blue variable star Eta Carinae. Situated approximately 7,500 light-years from Earth, in the constellation Carina, Eta Carinae outshines our own sun millions of times over.

This stellar behemoth is undergoing a highly volatile phase in its life, characterized by dramatic fluctuations in brightness and massive eruptions. Eta Carinae's brilliance is not just a product of its size, but also of its tumultuous nature, which sees it expelling significant amounts of its mass into space in spectacular outbursts.


These events have made Eta Carinae a subject of intense study, as scientists seek to understand the mechanisms driving its instability and immense energy output, making it a beacon of stellar extremity in the cosmos.

What Is the Heaviest Star In the Universe?

While the UY Scuti is the largest star, R136a1 is currently the heaviest star in the universe. Located in the Large Magellanic Cloud, approximately 165,000 light years from Earth, R136a1 is a member of the rare class of hyper-massive stars, weighing in at more than 170 to 230 times the mass of our sun.

The existence of such a star challenges previous theories on the limits of stellar mass and highlights the extreme conditions under which stars can form and exist.


R136a1's extraordinary mass results in an intense gravitational pull, influencing its surroundings and showcasing the incredible diversity of stellar phenomena in the universe.

The study of such heavy stars provides invaluable insights into the processes of star formation, evolution and the ultimate fate of the most massive stars in the cosmos.

This article was updated in conjunction with AI technology, then fact-checked and edited by a HowStuffWorks editor.