Helix Nebula

A dying star unleashes its last breath captured by this fantastic image.

Found around 650 light years away in the constellation of Aquarius, the Helix Nebula (also known as NGC 7293) is a stunning example of a planetary nebula. Don’t be fooled by the name, though; planetary nebulas are actually the remains of stars that were once similar to our Sun.

When stars like these run out of hydrogen and helium fuel for their fusion reaction, just as the Sun radiates light and heat into the Solar System, the outer layers of the star are thrown off and all that is left is an extremely hot and dense core known as a white dwarf. These stars are about the size of Earth but have almost the same mass as the original star. Intense ultraviolet radiation from the white dwarf heats up the expelled gas, shining brightly in infrared wavelengths. The odd shape of the Helix Nebula, with two sides of the structure apparently flattened, is due to the gas colliding with the interstellar medium.

If the original star had any planets, comets or otherwise, these would also have been thrown about by the resultant expansion of the star’s layers, similar to what will happen to our Solar System when our Sun runs out of fuel in around 5 billion years. The inner planets would have been destroyed, while the outer gas planets and icy bodies may have collided and added to the cosmic dust storm.

The Helix Nebula, which is believed to be about 11,000 years old and 2.5 light years across, also contains something called ‘cometary knots’, which are areas of nebulosity (relatively concentrated dust and gas) in the main ring. They are described as cometary because they radiate tails away from the centre of the nebula, however, their size is anything but cometary; each knot is thought to be about the size of our Solar System, excluding their tails. More than 20,000 of these knots are estimated to be in the Helix Nebula.

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