How Big Is Stephenson 2-18 Compared To The Sun?

Stephenson 2-18’s colossal size is truly mind-boggling, dwarfing our Sun by a factor of 2,150 in radius; explore this comparison further on COMPARE.EDU.VN. To understand the sheer scale, we will delve into detailed comparisons, discuss its unique characteristics, and explore the implications of such a gigantic celestial body, all while using astronomical measurements and stellar comparisons for in-depth understanding; also, we will touch base with luminous red supergiants.

1. What Is Stephenson 2-18 and Where Is It Located?

Stephenson 2-18 (St2-18) is a red supergiant, or perhaps even a red hypergiant star, residing within the Scutum constellation. Also known as Stephenson 2-DFK 1 and RSGC2-18, it currently holds the title of the largest known star, boasting a size approximately 2,150 times that of our Sun. This celestial giant is situated approximately 18,900 light-years away from Earth, appearing in the same region as the open cluster Stephenson 2.

Stephenson 2-18 red supergiant

This placement suggests a possible association with this cluster, although its exact membership remains uncertain. This is the size comparison between our Sun and Stephenson 2-18.

2. What Type of Star Is Stephenson 2-18?

Stephenson 2-18 belongs to the spectral type M6, categorizing it as a red supergiant. Its enormous radius of approximately 2,150 solar radii makes it one of the largest stars ever discovered. It also ranks among the most luminous stars in the Milky Way galaxy and is recognized as one of the most luminous red supergiants known. Its effective temperature is around 3,200 K. St2-18 radiates with an astounding 436,516 times the luminosity of the Sun. A 2012 study, utilizing data from the Australia Telescope Compact Array (ATCA) and the DUSTY model, derived these stellar properties.

3. How Does Stephenson 2-18 Compare in Size to the Sun?

Stephenson 2-18 possesses an estimated radius of 2,150 solar radii. To put this into perspective, if St2-18 were to replace the Sun at the center of our solar system, it would extend beyond the orbit of Saturn. This distance is 2,047 – 2,049.9 R☉. Its volume is roughly 10 billion times greater than that of the Sun. Only a few other stars come close to this magnitude. Those are MY Cephei in the constellation Cepheus (with a radius 1,134 – 2,061 times that of the Sun) and WY Velorum in Vela (with 2,028 solar radii).

Traveling at the speed of light, it would take approximately nine hours to circumnavigate the surface of Stephenson 2-18. This same journey around the Sun would take a mere 14.5 seconds. The estimated radius of Stephenson 2-18 exceeds current theoretical predictions. The theoretical limit of star size in the Milky Way is around 1,500 solar radii.

4. How Does Stephenson 2-18 Compare to Other Large Stars Like UY Scuti?

Stephenson 2-18 took the title of the largest star known from previous record holders. These were the red supergiants WOH G64 in the constellation Dorado and UY Scuti in Scutum. WOH G64 has an estimated radius between 1,540 and 1,730 solar radii, smaller than St2-18.

UY Scuti had an estimated radius of 1,708 solar radii until more accurate measurements of the star’s parallax in the Gaia Data Release 2. These yielded a lower distance and therefore lower values for the star’s luminosity and radius. The estimated radius of UY Scuti is now only 755 solar radii, which is comparable to that of Antares (680 – 800 R☉). But it’s smaller than the radii of Betelgeuse (887 R☉), Mu Cephei (972 – 1,260 R☉), VY Canis Majoris (1,420 R☉), and HR 5171A (1,060 – 1,160 R☉). However, the Gaia data may not be reliable, and the supergiant may indeed be larger.

5. What Is the Significance of the Stephenson 2 Open Cluster?

The open cluster Stephenson 2 ranks among the most massive open clusters in the Milky Way. American astronomer Charles Bruce Stephenson first noticed it. He reported the discovery of “ten faint, dust-reddened stars, several of them probable M supergiants, in a 1.5 x 3 arcmin area of sky” in a study published in The Astronomical Journal in June 1990.

Stephenson discovered the cluster during a space-deep infrared objective-prism survey of the northern Milky Way. This used the Burrell Schmidt Telescope of the Warner and Swasey Observatory. He estimated a distance of 30 kiloparsecs (98,000 light-years) for the cluster. He based this on the assumption that the stars were all red supergiants. Stephenson 2-18 is now believed to lie approximately 18,900 light-years away. This is a similar distance to the cluster. But there are still uncertainties regarding its membership.

6. What Is Known About the Properties of the Stars in the Stephenson 2 Cluster?

The cluster spans about 6’ of the sky. It contains a core group of 26 red supergiants, the largest known population in the Milky Way. This was first identified in a study published in The Astrophysical Journal in 2007. Study authors estimated a spectral type of M5 or M6 for St2-18. They suggested that the star would soon expel its outer layers and evolve into a luminous blue variable (LBV) or Wolf-Rayet star.

The estimated age of the cluster is 17 ± 3 million years. The study gave the identifier 1 to the brightest star in the K-band that lay in the same line of sight as the cluster (St2-18). The study concluded that the star likely had considerable infrared excess. It may be a red hypergiant like VY Canis Majoris.

7. What Is the Larger Context of Stephenson 2 Within the Milky Way?

A 2012 study reported about 80 red supergiants appearing in the same line of sight as Stephenson 2 (RSGC2). Forty of these had radial velocities indicating that they were members of the cluster. Since these supergiants are spread across a wider area of the sky, they likely form an extended stellar association. The cluster has an estimated mass between 30,000 and 50,000 solar masses. It has a physical radius of about 4 parsecs (13 light-years).

The cluster is believed to be located at the intersection of the northern end of Milky Way’s Long Bar. Also, it’s located at the inner region of the Scutum-Centaurus Arm. This is one of our galaxy’s two major spiral arms (the other being the Perseus Arm).

8. Are There Other Similar Clusters and Stars in the Same Region of the Sky?

Stephenson 2 is one of several massive open clusters containing multiple red supergiants located in the constellation of Scutum. The others include RSGC1, RSGC 3, Alicante 7 (RSGC5), Alicante 8 (RSGC4), and Alicante 10 (RSGC6). These clusters appear in the same area of the sky. RSGC1 hosts the red supergiant RSGC1-F01. This star’s radius (1,530 R☉) would extend past the orbit of Jupiter if placed at the center of the solar system.

The clusters RSGC2 (Stephenson 2) and RSGC1 contain about 20% of all the known red supergiants in the Milky Way. They are frequent targets for observations studying pre-supernova evolution.

9. How Has Stephenson 2-18 Been Identified and Studied Over Time?

In a study published in 2010, the supergiant was given the identifier 18. It was assigned to the Stephenson 2 SW cluster. This is an aggregation of stars 5’ southwest of the core cluster. It is believed to lie at the same distance as Stephenson 2.

A 2013 study of the class M supergiants in the cluster Stephenson 2 detected maser emission from the two brightest members of the cluster. This indicated that the stars have the highest mass loss rates of all the members.

10. Why Does Stephenson 2-18 Have Multiple Names and Designations?

Stephenson 2-18 lacks a proper name. Its designation comes from the name of its discoverer, Charles Bruce Stephenson. The star is also known as RSGC2-18 and Stephenson 2 DFK 1.

RSGC2 stands for Red Supergiant Cluster 2. DFK 1 comes from the initials of Ben Davies, Don F. Figer, and Rolf-Peter Kudritzki. They identified a core group of 26 physically associated red supergiants in Stephenson 2 in 2007. St2-18 was given the identifier 1 as the brightest star appearing in the region. However, it was believed to be an unrelated red supergiant.

11. Where Is Stephenson 2-18 Located Within Its Constellation?

Stephenson 2-18 appears as a member of the open cluster Stephenson 2. This occupies an area of 1.8’ of the sky. However, it is not visible in amateur telescopes. The cluster cannot be detected in visible light at all. It is heavily obscured by dust. But it can be seen in infrared light. It lies in the region of the sky between Alpha and Beta Scuti.

12. What Is the Significance of the Scutum Constellation Where Stephenson 2-18 Is Located?

Stephenson 2-18 is located in the constellation Scutum. Originally known as Scutum Sobiescianum (the Shield of Sobieski), the constellation was named by Polish astronomer Johannes Hevelius. This was in honor of the Polish King John III Sobieski’s victory in the Battle of Vienna in 1684.

Scutum is one of the smallest and faintest constellations in the sky. It is the 84th constellation in size. It stretches across only 109 square degrees of the southern sky. It does not contain any stars brighter than magnitude 3.00. None of its stars make the list of the 300 brightest stars in the sky.

13. What Are Some Notable Celestial Objects Within the Scutum Constellation?

Scutum is best known for being home to the variable white giant star Delta Scuti. This serves as a prototype for its own class of variables. It’s also known for the pulsating variable red supergiant UY Scuti, one of the largest known stars. Notable deep sky objects in Scutum include the open clusters Messier 11. This is better known as the Wild Duck Cluster. Also there’s Messier 26, the massive young clusters RSGC1, RSGC2 (Stephenson 2), RSGC3 and RSGC4 (Alicante 8), the globular cluster NGC 6712, and the planetary nebula IC 1295.

14. When Is the Best Time to Observe the Scutum Constellation?

The best time of the year to observe the stars and deep sky objects in Scutum is during the month of August. This is when the constellation rises high above the horizon in the evening. The entire constellation is visible from locations between the latitudes 80° N and -90° S. Thus, it’s visible from all inhabited places on Earth.

15. What Are the Key Properties of Stephenson 2-18 That Define Its Size and Luminosity?

Stephenson 2-18 has several key properties that contribute to its immense size and luminosity. These include its spectral class of M6. It also includes its apparent magnitudes, distance, luminosity, radius, and temperature. All of these factors combine to make it one of the most remarkable stars known to astronomers.

Stephenson 2-18: Key Properties

Spectral class	M6
Apparent magnitude (G)	15.2631 ± 0.0092
Apparent magnitude (J)	7.150
Apparent magnitude (H)	4.698
Apparent magnitude (K)	2.9
Distance	18,900 light years (5,800 parsecs)
Parallax	−0.1524 ± 0.2330 mas
Proper motion	RA: −1.697 ± 0.266 mas/yr
	Dec.: -4.637 ± 0.221 mas/yr
Luminosity	436,516 L☉ (90,000 – 630,000 L☉)
Radius	2,150 R☉
Temperature	3,200 K
Constellation	Scutum
Right ascension	18h 39m 02.3694806915s
Declination	−06° 05′ 10.556738789″
Names and designations	Stephenson 2-18, St2-18, Stephenson 2 DFK 1, Gaia DR2 4253084565963481856, Gaia DR3 4253084565963481856, MSX6C G026.1044-00.0283, IRAS 18363-0607, 2MASS J18390238-0605106

16. What Does It Mean for a Star to Be Classified as a Red Supergiant or Red Hypergiant?

Red supergiants and red hypergiants are stars in the later stages of their lives. They have expanded significantly and cooled down. As a result, they appear redder in color. These stars are among the largest and most luminous in the universe. They are characterized by their extreme size and high energy output. Their classification helps astronomers understand stellar evolution and the life cycles of stars.

17. How Do Astronomers Measure the Size and Distance of Stars Like Stephenson 2-18?

Astronomers use several methods to measure the size and distance of stars. These include parallax measurements, spectroscopic analysis, and photometric studies. Parallax measures the apparent shift in a star’s position. This is due to the Earth’s orbit around the Sun. Spectroscopic analysis examines the light emitted by a star to determine its properties. Photometric studies measure the brightness of a star to estimate its distance and size. These techniques provide critical data for understanding stellar characteristics and locations.

18. What Are the Implications of Stephenson 2-18’s Size for Stellar Evolution Theories?

Stephenson 2-18’s massive size challenges current stellar evolution theories. Its radius exceeds the theoretical limit for star size in the Milky Way, which is around 1,500 solar radii. This suggests that our understanding of how stars form and evolve may be incomplete. Further research is needed to explain how such enormous stars can exist. What are the processes that allow them to reach such extreme sizes.

19. What Could Happen to Stephenson 2-18 in the Future?

In the future, Stephenson 2-18 is likely to undergo significant changes. As a red supergiant, it may expel its outer layers and evolve into a luminous blue variable (LBV) or Wolf-Rayet star. Eventually, it will likely end its life in a supernova. This would result in a dramatic explosion that scatters its material into space. This event will mark the end of its stellar life cycle.

20. How Does the Discovery of Stars Like Stephenson 2-18 Contribute to Our Understanding of the Universe?

The discovery of stars like Stephenson 2-18 contributes significantly to our understanding of the universe. It challenges existing theories. It prompts astronomers to develop new models to explain the extreme phenomena observed in these stars. Studying these celestial giants provides insights into stellar evolution, galactic structure, and the fundamental processes that shape the cosmos. It broadens our knowledge of the universe.

21. What Are the Challenges in Studying Stars Like Stephenson 2-18?

Studying stars like Stephenson 2-18 presents several challenges. Its great distance and the obscuration by dust make it difficult to observe in detail. The uncertainties in measuring its exact parameters, such as luminosity and radius, add to the complexity. Developing accurate models to explain its existence and behavior requires overcoming these observational and theoretical hurdles.

22. What Instruments and Observatories Are Used to Study Distant Stars Like Stephenson 2-18?

Astronomers use a variety of instruments and observatories to study distant stars like Stephenson 2-18. These include ground-based telescopes such as the Australia Telescope Compact Array (ATCA). They also include space-based observatories like the Spitzer Space Telescope and the Gaia satellite. These tools enable astronomers to gather data across different wavelengths. Thus, providing a comprehensive view of these distant celestial objects.

23. How Can Amateur Astronomers Observe the Region of the Sky Where Stephenson 2-18 Is Located?

Amateur astronomers can observe the region of the sky where Stephenson 2-18 is located. The constellation Scutum can be seen with binoculars or small telescopes. Stephenson 2-18 itself is not visible in amateur telescopes due to its faintness and obscuration by dust. But the surrounding star field and nearby deep sky objects can be rewarding targets for observation.

24. What Role Do Computer Models Play in Understanding the Properties of Stars Like Stephenson 2-18?

Computer models play a crucial role in understanding the properties of stars like Stephenson 2-18. These models simulate the physical processes occurring within stars. They help astronomers predict their behavior. Models like the DUSTY model are used to derive stellar properties from observational data. They provide insights into the internal structure, energy transport, and evolutionary paths of these celestial objects.

25. How Does the Study of Red Supergiants Help Us Learn About Supernova Events?

The study of red supergiants helps us learn about supernova events. Red supergiants are the progenitors of Type II supernovae. Studying their properties and behavior before they explode provides valuable information about the conditions that lead to these cataclysmic events. Understanding red supergiants helps astronomers predict and interpret supernova observations. It advances our knowledge of stellar death and the distribution of elements in the universe.

26. What Is the Relationship Between a Star’s Mass and Its Eventual Fate?

A star’s mass is a primary factor determining its eventual fate. Low-mass stars like our Sun will eventually become red giants. After that, they will turn into white dwarfs. High-mass stars, on the other hand, will evolve into red supergiants. Then, they will end their lives as supernovae. This process leaves behind neutron stars or black holes. The mass of a star dictates its internal processes and evolutionary pathway. It shapes its destiny.

27. How Does the Luminosity of Stephenson 2-18 Compare to Other Stars in Our Galaxy?

The luminosity of Stephenson 2-18 is exceptionally high. It radiates with approximately 436,516 times the luminosity of the Sun. This makes it one of the most luminous stars in our galaxy. Its high luminosity is a result of its large size and high energy output. It distinguishes it from most other stars in the Milky Way.

28. What Are Maser Emissions, and What Do They Tell Us About Stars Like Stephenson 2-18?

Maser emissions are microwave amplification by stimulated emission of radiation. They are a type of radiation emitted by certain molecules in space. The detection of maser emissions from stars like Stephenson 2-18 indicates that they have high mass loss rates. It means they are expelling large amounts of material into space. These emissions provide valuable insights into the conditions and processes occurring in the outer layers of these stars.

29. How Does the Location of Stephenson 2-18 in the Scutum-Centaurus Arm Affect Its Properties?

The location of Stephenson 2-18 in the Scutum-Centaurus Arm influences its properties. This region is known for its high concentration of massive stars and active star formation. The surrounding environment can affect the star’s composition, evolution, and interaction with other celestial objects. The Scutum-Centaurus Arm provides a unique setting for the study of massive stars like Stephenson 2-18.

30. What New Discoveries Are Expected in the Future About Stars Like Stephenson 2-18?

Future studies and observations are expected to reveal new discoveries about stars like Stephenson 2-18. Improved observational techniques and instruments may provide more accurate measurements of its parameters. It may unveil previously unknown details about its structure and behavior. Theoretical advances will refine our understanding of stellar evolution. This will help us explain the existence and properties of these extreme celestial objects.

31. Is Stephenson 2-18 Visible to the Naked Eye?

No, Stephenson 2-18 is not visible to the naked eye. It is too faint and distant to be seen without the aid of telescopes. The star’s apparent magnitude is around 15.26, which is well below the limit of what human eyes can detect. Even with amateur telescopes, it remains challenging to observe due to its location behind dense dust clouds.

32. How Does the Temperature of Stephenson 2-18 Affect Its Color?

The temperature of Stephenson 2-18 significantly affects its color. With an effective temperature of around 3,200 K, it is classified as a red supergiant. The relatively low temperature causes it to emit more light in the red part of the spectrum, giving it a reddish appearance. Hotter stars, in contrast, emit more blue light and appear bluish.

33. What Are the Typical Lifespan Stages of a Star Like Stephenson 2-18?

The typical lifespan of a star like Stephenson 2-18 includes several stages. It begins as a massive star formed in a molecular cloud. As it ages, it becomes a red supergiant. Then, it expels its outer layers. Eventually, it ends its life in a supernova explosion. This leaves behind a neutron star or black hole. This lifecycle is characterized by high luminosity and significant mass loss.

34. Can Stephenson 2-18 Influence the Formation of New Stars in Its Vicinity?

Yes, Stephenson 2-18 can influence the formation of new stars in its vicinity. As a massive star, it emits strong radiation and stellar winds. These can compress surrounding gas and dust clouds, triggering the collapse and formation of new stars. The star’s presence can both promote and disrupt star formation in its local environment.

35. What Kind of Elements Are Likely to Be Found in the Atmosphere of Stephenson 2-18?

The atmosphere of Stephenson 2-18 is likely to contain a variety of elements. Hydrogen, helium, carbon, oxygen, and heavier elements created through nuclear fusion are all present. As a red supergiant, it has undergone significant nuclear processing, enriching its atmosphere with these elements. These elements are expelled into space through stellar winds and supernova events.

36. How Does Stephenson 2-18’s Distance Affect the Accuracy of Its Measured Properties?

Stephenson 2-18’s great distance affects the accuracy of its measured properties. The farther a star is, the more challenging it is to measure its parallax. Because of that, it is harder to determine its exact distance, luminosity, and radius. Uncertainties in distance measurements propagate into uncertainties in other derived properties. This makes it difficult to precisely characterize the star.

37. What Other Names or Designations Are Used to Refer to Stephenson 2-18?

Stephenson 2-18 is also known by other names and designations, including:

• St2-18
• Stephenson 2 DFK 1
• RSGC2-18
• Gaia DR2 4253084565963481856
• Gaia DR3 4253084565963481856
• MSX6C G026.1044-00.0283
• IRAS 18363-0607
• 2MASS J18390238-0605106

These designations reflect different catalogs and studies that have identified and characterized the star.

38. How Do Binary Star Systems Compare in Size to Stars Like Stephenson 2-18?

Binary star systems typically do not reach the same extreme sizes as stars like Stephenson 2-18. While binary systems can consist of massive stars, the interactions between the stars often limit their individual growth. Stars like Stephenson 2-18 are single, evolved supergiants that have expanded to enormous proportions. This is less common in binary systems.

39. What Advances in Telescope Technology Could Improve Our Understanding of Stars Like Stephenson 2-18?

Advances in telescope technology could greatly improve our understanding of stars like Stephenson 2-18. Larger telescopes with higher resolution and sensitivity would allow for more accurate measurements of their properties. Space-based telescopes, free from atmospheric distortion, could provide clearer images and spectroscopic data. Advanced adaptive optics systems could also enhance the resolution of ground-based telescopes.

40. What Is the Significance of Studying Star Clusters Like Stephenson 2 in Understanding Stellar Populations?

Studying star clusters like Stephenson 2 is crucial for understanding stellar populations. Star clusters contain groups of stars that formed at the same time and from the same material. This provides a unique opportunity to study the evolution of stars with similar ages and compositions. By analyzing the properties of stars in clusters, astronomers can refine their models of stellar evolution and understand how different types of stars form and evolve.

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Frequently Asked Questions About Stephenson 2-18

1. What is Stephenson 2-18?

   Stephenson 2-18 is a red supergiant star located in the constellation Scutum. It is one of the largest known stars.

2. How Big Is Stephenson 2-18 Compared To The Sun?

   Stephenson 2-18 has a radius approximately 2,150 times that of the Sun.

3. Where is Stephenson 2-18 located?

   Stephenson 2-18 is located in the constellation Scutum, about 18,900 light-years from Earth.

4. What type of star is Stephenson 2-18?

   Stephenson 2-18 is a red supergiant star of spectral type M6.

5. How luminous is Stephenson 2-18?

   Stephenson 2-18 shines with 436,516 times the luminosity of the Sun.

6. What is the Stephenson 2 open cluster?

   The Stephenson 2 open cluster is one of the most massive open clusters in the Milky Way.

7. How was Stephenson 2-18 discovered?

   Stephenson 2-18 was discovered by Charles Bruce Stephenson as part of the Stephenson 2 open cluster.

8. What are the other names for Stephenson 2-18?

   Stephenson 2-18 is also known as St2-18, Stephenson 2 DFK 1, and RSGC2-18.

9. What constellation is Stephenson 2-18 located in?

   Stephenson 2-18 is located in the constellation Scutum.

10. What are the key properties of Stephenson 2-18?

    Key properties of Stephenson 2-18 include its large radius, high luminosity, and cool surface temperature.