List of largest known stars facts for kids

The largest stars known are truly enormous, much bigger than our own Sun! Imagine stars so big that if our Sun were a tiny pebble, these giants would be like huge boulders or even mountains. Scientists measure their size by comparing them to the Sun's radius. One solar radius is about 695,700 kilometers (432,280 miles).

The sizes of planets in our Solar System compared to some well-known stars. You can see how tiny Earth is next to Jupiter, and how even Jupiter is small compared to the Sun and other stars!

What Makes a Star Big?

Stars get their huge size from different things. The biggest stars are often called red supergiants. These are old stars that have used up most of their fuel. When this happens, they swell up to incredible sizes, becoming much cooler and redder.

Sometimes, stars can suddenly grow even bigger for a short time! This happens during events like "luminous red novae" or "LBV eruptions." During these events, a star can expand super fast, reaching thousands of times the Sun's radius in just a few months. That's even bigger than the largest red supergiants!

Scientists also think that some of the very first stars in the universe, called "Population III" stars, might have been super-duper massive. These early stars might have grown into "red supergiant protostars" that were tens of thousands of times bigger than our Sun! They would have been as big as some of the largest black holes we know today.

How Do We Measure Stars?

It's tricky to measure the exact size of a star, especially when they are so far away! One way is to measure their "angular diameter." This is how big a star looks from Earth. It's like holding a coin far away – it looks small, but it's still the same size. Scientists use special telescopes that combine light from different places, called stellar interferometers, to get a clearer view.

Another way to measure stars is when they pass in front of the Moon (called a lunar occultation) or when they are part of a binary star system where one star passes in front of another.

However, even with these methods, it's hard to be perfectly accurate. Stars have thin outer layers, and their edges can look different depending on the type of light we use to observe them. Also, many giant stars change their size over time, like a beating heart, which makes it even harder to get one exact measurement. So, the sizes you see in these lists are often averages or within a range of possible values.

Things to Remember About Star Sizes

Measuring the exact size of the biggest stars is really tough, and there can be some errors. Here are a few reasons why:

• Most star sizes are estimated using math formulas that connect a star's brightness and its surface temperature.
• Knowing the exact distance to a star is hard, and any mistake in distance affects the size calculation.
• Many supergiant stars have huge, cloudy atmospheres or are hidden by dust, which makes it hard to see their true surface.
• These giant stars often change their size over months or years, like variable stars. This means their brightness changes too, making it tricky to pin down their exact size.
• It's much easier to measure stars that are part of star clusters or binary systems because their distances are better known.
• Stars in other galaxies might behave a bit differently than those in our Milky Way. For example, some red supergiants in the Magellanic Clouds might have slightly different temperatures or brightness limits.

All the sizes in these lists have some uncertainty, and scientists are always working to get more accurate numbers!

Lists of the Largest Stars

Here are some of the biggest stars we know, grouped by the galaxy they are in. The sizes are given in "solar radii," meaning how many times bigger they are than our Sun.

Milky Way Galaxy

This list shows some of the largest known stars in our home galaxy, the Milky Way.

Magellanic Clouds

The Magellanic Clouds are two small galaxies close to our Milky Way.

Andromeda (M31) and Triangulum (M33) Galaxies

These are two other large galaxies in our Local Group of galaxies.

Other Galaxies (within the Local Group)

These are other galaxies that are part of our Local Group, a cluster of galaxies that includes the Milky Way.

Outside the Local Group

These stars are in galaxies much farther away from us.

Transient Events

Sometimes, stars can temporarily become much larger during special events like red novae (a type of star explosion) or LBV eruptions (when a very bright star suddenly gets even brighter).

Images for kids

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  Four well-defined large red supergiants and their respective sizes, including S Persei, AH Scorpii, VY Canis Majoris, and WOH G64.

See also