Stephenson 2–18 Characteristics :-
1. Size and Volume
- Stephenson 2-18 is estimated to have a radius of about 2,150 times that of the Sun.
- If it were placed at the center of our solar system, its outer layers would extend beyond the orbit of Saturn (and possibly even Uranus).
- This means St2-18 is so large that about 10 billion Suns could fit inside it.
2. Mass
- While it is extremely large, its mass is only about 30–40 times the Sun’s mass.
- Most of its volume is made of very low-density gases, making it an extremely extended and “fluffy” star.
3. Temperature and Luminosity
- St2-18 has a surface temperature of around 3,000–3,500 K, which is much cooler than our Sun (~5,778 K).
- Despite its low temperature, it is one of the most luminous stars known, with a luminosity about 440,000 times that of the Sun.
- This extreme brightness is due to its enormous surface area, which allows it to radiate a massive amount of energy.
4. Location
- St2-18 is found in the Stephenson 2 cluster, which is located about 19,570 light-years away from Earth in the constellation Scutum.
- This cluster contains many other red supergiants, but St2-18 is the largest of them all.
5. Lifespan and Fate
- Red supergiants like St2-18 are in the late stages of stellar evolution.
- It is expected to end its life in a supernova explosion, which will leave behind either a neutron star or a black hole.
- Because of its massive size, it may undergo a hypernova, an even more powerful explosion than a standard supernova.
6. Why is it So Big?
- St2-18 has reached such a huge size because it is in the final phase of its life.
- It has exhausted most of its hydrogen fuel and has expanded dramatically as it burns heavier elements in its core.
- UY Scuti vs. Stephenson 2-18: Which is Bigger
- Which One is Bigger?
- Stephenson 2-18 is larger than UY Scuti in terms of radius and volume.
- UY Scuti was once thought to be the biggest, but newer measurements suggest St2-18 surpasses it in size.
- However, UY Scuti is still extremely massive and remains one of the most famous red supergiants.
Why Was UY Scuti Considered the Largest?
- UY Scuti was discovered and measured earlier than St2-18.
- When it was first studied in 2012, astronomers estimated its size at 1,700 times the Sun’s radius, making it the largest at the time.
- Later observations using better instruments found St2-18 to be even bigger, pushing UY Scuti to second place.
Final Answer: Stephenson 2-18 is Bigger
Yes, UY Scuti is massive, but based on current astronomical data, Stephenson 2-18 is the largest star found in the known universe.
Stephenson 2-18 is the largest known star in terms of physical size in the entire universe. It is a dying, extremely luminous red supergiant that will eventually explode in a spectacular supernova. Despite its immense size, it is not the most massive star, but it is one of the most fascinating objects ever discovered in the cosmos.
