Universe Guide

G Type Stars - Yellow Dwarf and Giant Stars

Yellow Star Facts

As mentioned earlier, our own star is a yellow dwarf star and it is the star by which other stars are measured by. For example, when talking about Luminosity, the Sun has a Luminosity of 1 and the other star's Luminosity is a multiple of the Sun. Other yellow dwarfs have been known to have planets orbiting them.

Whilst we may call them Yellow Dwarfs, the star classification can also include stars that are white. In fact, our star, the Sun is white in colour, its just that the atmosphere makes our star appear yellow.

Our star should really be green in colour due to the spectrum wavelength. The reason why we don't see green is because the green is drowned out by other colours in the spectrum. In fact there are no green stars although there is debate as to whether Zubeneschamali in the constellation of Libra is a green star or not. Astronomy Trek

Unlike Red Dwarf Stars, Yellow Dwarf stars are not efficient with their fuel. A red dwarf star could live for trillions of years whereas a yellow dwarf Star will typically live for only about ten billion years. Our star is a relatively middle age star, there's another billion years left on it before the Earth becomes inhospitable.

The Sun, a Yellow G Star

The Sun is at the centre of our solar system which all the planets orbit round. 70% of its mass is hydrogen, 28% Helium and all the other materials make up just 2%. The Sun consumes and uses mass of a rate of 4 million tonnes a second, this might seem a lot but its nothing to worry about. The Sun has plenty of hydrogen still to go through and will be here long after we've gone.

The core of the Sun is about 400,000 kilometers in diameter. To put that in context, the Earth's diameter is 12,742 km according to Google. The Sun's diameter is 1,392,000 kilometers so the core makes up just under a third of the star.

The Sun emits more than 30 billion times the energy that all the nuclear power plants on the planet produce. We capture that energy using solar panels to provide clean energy. Cronodon

The Sun weighs in at a massive 1,989,100,000,000,000,000,000,000,000,000 kilograms and is more than 332,900 times heavier. Planet Facts


We've known since life existed that life could exist on a planet that orbits a Yellow Dwarf Star, our planet is one. Other Yellow Dwarf stars have been found to have planets in orbit.

The first exoplanet to be discovered was found orbiting a pulsar now called Lich. The first exoplanet to found round a hospitable star was a yellow star called 51 Pegasi, now known as Helvetios. It turned out that the star was boiling away its planet but it was enough to show that stars other than our own Sun could have orbiting planets.

Evolution of a Yellow Dwarf Star

A Yellow Dwarf star will be created in the same way as other stars from a dust cloud. An event in nearby space would have caused the cloud to collapse, first creating a Protostar, a T-Tauri star then eventually a Yellow Dwarf star. Not all stars become T-Tauri stars, only those less than 3 solar masses were T-Tauri stars. T-Tauri stars are named after the prototype star which is T-Tauri.

When the star becomes a main sequence star, it will fuse hydrogen into helium. Once it has finished fusing into helium, it leaves the main sequence and onto the next stage in its evolutionary path. It will eventually end up as a White Dwarf Star.

A Yellow Dwarf star will grow in size because gravity will not longer be able to contain the outward pressure. Don't worry, we have at least a billion years before that stage. When the stage does begin, the inner planet will be consumed by the star. The star will turn to a cooler red. Planets that were once able to support life will no longer as the Goldilocks Zone will have moved out further from its currently location. If we are still alive then, we'd have had to move to the outer planets or to another star system.

List of Yellow Dwarf Stars Examples

Related Pages of Interest :-

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