The Largest Star in the Universe – Size Comparison

Summary

This script delves into the cosmic scale of stars, from the smallest gas giants to the largest hypergiants. It explains the progression from brown dwarfs to main sequence stars, highlighting the differences in size, brightness, and lifespan based on mass. The script introduces the most massive known star, R136a1, and the largest, Stephenson 2-18, illustrating the rarity and short lives of such celestial behemoths. It concludes with the cyclical nature of star birth, death, and the formation of new stars, emphasizing the universe's vastness and the ongoing cosmic dance.

Takeaways

• 🌌 The universe contains the largest star known as R136a1, which has 315 solar masses and is 9 million times brighter than the Sun.
• 🔥 Stars are massive celestial bodies that undergo nuclear fusion in their cores, converting hydrogen into helium and releasing energy.
• 🌑 Sub-brown dwarfs, like Jupiter, are the smallest objects with star-like properties but lack the mass to ignite nuclear fusion.
• 🌟 Brown dwarfs are sometimes called 'failed stars' and have a mass between 13 and 90 times that of Jupiter, capable of slow nuclear fusion.
• ✨ Main sequence stars are the most common type of star, including our Sun, and they fuse hydrogen into helium in their cores.
• 🌕 Red dwarfs are the smallest and most abundant main sequence stars, with a long lifespan due to their slow fuel consumption.
• 🌞 The Sun is a G-type main sequence star, larger and brighter than red dwarfs, with a lifespan of about 10 billion years.
• 🌌 Sirius, the brightest star in the night sky, is twice as massive as the Sun and shines 25 times brighter, with a shorter lifespan.
• 🌀 Stars with around 10 solar masses have surface temperatures near 25,000°C and are extremely luminous but short-lived.
• 💥 The most massive stars, like R136a1, are rare and lose a significant amount of material through stellar winds due to their extreme properties.
• 🌀 Red giants are a phase in a star's life when it exhausts hydrogen in its core, leading to a significant increase in size.
• 🌀 Hypergiants are the largest and rarest type of stars, with immense surface areas and powerful stellar winds that can blow themselves apart.
• 🌌 The largest known star, Stephenson 2-18, is estimated to be around 2150 times the size of the Sun and shines with almost half a million times the power of the Sun.

Q & A

What is the largest star in the universe currently known?

The largest star currently thought to be among the largest we've found is Stephenson 2-18, which is estimated to be around 2150 times the size of the Sun.

Why are stars like R136a1 rare and short-lived?

Stars like R136a1 are rare because they form through the merger of several high mass stars in dense star-forming regions. They are short-lived because they burn their core hydrogen in only a few million years.

What is the difference between a brown dwarf and a main sequence star?

A brown dwarf is a failed star that has between 13 and 90 times the mass of Jupiter and can undergo slow nuclear fusion reactions, but it doesn't ignite like a main sequence star. Main sequence stars have enough mass to ignite hydrogen into helium in their cores, releasing tremendous amounts of energy.

What happens to a star when it exhausts hydrogen in its core?

When a main sequence star exhausts the hydrogen in its core, it contracts, making it hotter and denser, leading to a faster fusion process that pushes back against gravity and causes the outer layers to swell, entering a giant phase.

How do hypergiants differ from other types of stars?

Hypergiants are the giant phase of the most massive stars in the universe. They have an enormous surface area that can radiate an insane amount of light and are so large that they are essentially blowing themselves apart due to the weak gravity at the surface.

What is the role of the stellar wind in supermassive stars?

The stellar wind in supermassive stars is responsible for losing a significant amount of material from the star every second. For example, R136a1 loses 321 thousand billion tons of material through its stellar wind every second.

Why are red dwarfs the most abundant type of star in the universe?

Red dwarfs are the most abundant type of star in the universe because they burn their fuel very slowly, which allows them to last up to ten trillion years, a thousand times the current age of the universe.

How does the mass of a star affect its brightness and lifespan?

The more massive a main sequence star is, the hotter and brighter it burns, but the shorter its life is. For instance, Sirius, with 2 solar masses, shines 25 times brighter than the Sun but has a lifespan reduced to 2.5 billion years.

What is the significance of the Sun's mass in the solar system?

The Sun is significant in the solar system as it makes up 99.86% of all its mass, dominating and influencing the dynamics and environment of the entire system.

How does the size of a star relate to its life cycle?

The size of a star is directly related to its life cycle. Larger stars burn hotter and brighter, leading to shorter lifespans. Conversely, smaller stars like red dwarfs have longer lifespans due to their slower fuel consumption.

What is the Universe In A Nutshell app, and how does it relate to the script?

The Universe In A Nutshell app is a tool created by Kurzgesagt in collaboration with Tim Urban, which allows users to explore the scale of the universe, from the smallest particles to the largest stars and galaxies, inspired by the concepts discussed in the script.