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Elements of the Universe

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The Universe is vast, perhaps 60 billion light years across, if not infinite. Surely somewhere out in the vastness of Space there must be some strange exotic elements? Perhaps Kryptonite or Dilithium. Yet after more than a century of searching we have not discovered evidence of any elements out there that are not found here on Earth.

The processes that created the elements we now find on Earth are the same as those all across the Universe. A few were formed in the Big Bang. Others were created in the heart of stars or during the catastrophic explosions of supernovae. Still others form when larger atoms split into smaller ones.

You can find out more in Elements of the Universe, in the Elements exhibition at the Ulster Museum.

Elements of the Universe

Elements of the Universe

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Elements from a distance

Elements from a distance

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Mostly hydrogen

Mostly hydrogen

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Stony meteorite: Solid sunshine

Stony meteorite: Solid sunshine

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Silicon carbide: The stuff of stardust

Silicon carbide: The stuff of stardust

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The Stellar Furnace

The Stellar Furnace

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Elements from dying stars

Elements from dying stars

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Precious metals: the Alchemists’ dream

Precious metals: the Alchemists’ dream

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The densest element

The densest element

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Even denser elements

Even denser elements

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The youngest elements

The youngest elements

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Image: Elements of the Universe on display in the Elements exhibition, Ulster Museum
Elements of the Universe on display in the Elements exhibition, Ulster Museum

Elements from a distance

Spectral lines for the first 6 elements. Image courtesy of Julie Gagnon
Spectral lines for the first 6 elements. Image courtesy of Julie Gagnon
Rosette Nebula. The red light indicates hydrogen.
Credit: T.A.Rector, B.Wolpa, M.Hanna (AURA/NOAO/NSF)
Rosette Nebula. The red light indicates hydrogen. Credit: T.A.Rector, B.Wolpa, M.Hanna (AURA/NOAO/NSF)

How can we know what elements are in the Sun, or in distant stars far across the Universe? This information is brought to us in the light emitted by these stars. When heated each element gives off light in a unique series of coloured bands – rather like an element barcode. When passed through an instrument called a spectroscope the light is split into its unique colour bands. From this astronomers can work out which elements are there even if the star is billions of light years away!

The unique spectrum of helium was first detected in the Sun more than a decade before the element was discovered on Earth. Its name comes from ‘Helios’, the Greek for Sun.

In Elements of Light you can see the full periodic table of element spectra.

Mostly hydrogen

Image: Bar graph of element abundance in the Universe
Bar graph of element abundance in the Universe

The first elements were created in the Big Bang, more than 13 billion years ago, but nearly all of this was hydrogen (H) and helium (He), with just tiny amounts of lithium (Li) and beryllium (Be).

Helium, second element of the Periodic Table, forms 8% of the atoms in the Universe.     (helium balloon)
Helium, second element of the Periodic Table, forms 8% of the atoms in the Universe. (helium balloon)
Tantalum cylinder, 55 mm tall.
Tantalum cylinder, 55 mm tall.

There are ten times as many hydrogen atoms in the Universe as all of the other atoms put together, and hydrogen and helium together make up 99.9% of the atoms. Less than a thousandth (0.1%) is left for all of the other elements! For every phosphorus (P) atom there are more than a million hydrogen (H) atoms, and for each tantalum (Ta) atom, the rarest stable element in the Universe, there are more than one trillion (one million million) hydrogen atoms.

Stony meteorite: Solid sunshine

Image: Ordinary Chondrite stony meteorite, 30 cm across, from Algeria (NWA 869)
Ordinary Chondrite stony meteorite, 30 cm across, from Algeria (NWA 869)

Meteorites are pieces of stone or metal that fall to Earth from Space. They come from within our own Solar System, and not from a galaxy far away.

Some types of stony meteorite have barely changed since the Solar System formed. The relative abundance of iron, silicon, magnesium, oxygen and many other elements that they contain are remarkably similar to the composition of the Sun (if you disregard the hydrogen and helium which make up most of the Sun). This similarity in composition of the Sun and these meteorites is evidence that the entire Solar System formed from the same cloud of dust and gas more than 4.5 billion years ago.

Silicon carbide: The stuff of stardust

Image: Silicon carbide crystals, 30 cm across, grown in an industrial furnace. The silicon carbide grains found in some meteorites are smaller than this.
Silicon carbide crystals, 30 cm across, grown in an industrial furnace. The silicon carbide grains found in some meteorites are smaller than this.

Silicon carbide is formed of just two elements. You can probably guess which ones. It is immensely hard and is manufactured on Earth as an industrial abrasive, but microscopic grains of this same compound are found in some meteorites. How did they get there?

Silicon and carbon are among the most common solid elements in the Universe. Tiny grains of silicon carbide are formed in red giant stars and then blasted out from the star into Space, by what is called the ‘stellar wind’, to become grains of interstellar dust. Some of this may become the building blocks of new planets and solar systems.

The silicon carbide grains found in meteorites are known as Pre-Solar grains because they were created in stars that existed hundreds of millions of years before our own Solar System formed 4567 million years ago.

The Stellar Furnace

Image: Graphite, 8 cm across, a pure carbon mineral and a key component of pencils.
Graphite, 8 cm across, a pure carbon mineral and a key component of pencils.

In the incredible heat and pressure of a star hydrogen atoms are fused together into helium. These helium atoms are then fused together to make heavier elements. Sun-sized stars make abundant carbon by fusing together three atoms of helium. Without these stellar furnaces there would be no carbon in the Universe, probably no life, and definitely no pencils.

Much larger and denser stars are needed to make other common elements, such as silicon and magnesium, but to make iron and heavier elements requires something even more extreme.

Elements from dying stars

Iron meteorite, 30 cm across, from Argentina (Campo del Cielo).
Iron meteorite, 30 cm across, from Argentina (Campo del Cielo).
Crystal structure of the interior of an iron-nickel meteorite, from Namibia
Crystal structure of the interior of an iron-nickel meteorite, from Namibia

Iron is the most abundant metal in the Universe. It forms at the heart of large dying stars and in supernovae, the most powerful explosions in the Universe, that scatter iron atoms through the vast emptiness of Space.

Planets are built from the dust of dead stars. Many planets melt soon after they form and gravity pulls the dense liquid iron downwards to form a core. The iron takes with it many other elements, such as nickel, gold and platinum, which is why precious metals are so rare in the Earth’s crust today.

Iron meteorites are fragments from the cores of planets. They are proof that some planets that once existed in our Solar System were destroyed by planetary collisions, but the iron atoms themselves have their origin in even more extreme events in the Universe.

Precious metals: the Alchemists’ dream

Image: A gold nugget weighing 30g found near Clay Lake, in County Armagh.
A gold nugget weighing 30g found near Clay Lake, in County Armagh.

For centuries alchemists strived to turn base metals, such as lead, into gold. But they never succeeded. What they needed was a neutron star, or preferably two.

To make really heavy elements, such as gold and platinum, requires lighter elements to be bombarded with vast numbers of neutrons. This only really happens when neutron stars collide. Even a supernova, an exploding star, is not enough. Think about that next time you wear a gold ring or bracelet.

The densest element

Image: These osmium pellets have a bluish tinge caused by a thin coasting of osmium tetroxide. Being so dense osmium might make a great paperweight – except that the tetroxide is very poisonous.
These osmium pellets have a bluish tinge caused by a thin coasting of osmium tetroxide. Being so dense osmium might make a great paperweight – except that the tetroxide is very poisonous.

Hydrogen is the least dense of all elements. 100 litres of hydrogen weighs just 9 grams, about the same weight as a pound coin. By comparison, 100 litres of water weighs 100,000 grams (100 kg).

The densest of the stable (non-radioactive) elements is the metal osmium, which is twice as dense as lead and weighs almost 22.6 times as much as water. 100 litres of osmium would weigh more than two and a quarter tonnes, a lot more than the average car!

Osmium, like its close neighbours iridium, platinum and gold, is formed during collisions between neutron stars.

Even denser elements

Image: Osmium and iridium are the densest known elements, but some of those in the row below may be even denser. They just don’t last long enough for us to check.
Osmium and iridium are the densest known elements, but some of those in the row below may be even denser. They just don’t last long enough for us to check.

Some elements that have been created in laboratories may be even denser than osmium. The density of hassium (element 108) is estimated at more than 40 times that of water, and almost twice as much as osmium, and several other elements (106 to 110) are more than 30 times as dense. But only tiny amounts of these elements have ever been made and they all decay too quickly to be sure how dense they are.

Even hassium is lightweight compared with the material found at the centre of a neutron star. Made entirely of tightly-packed neutrons, 100 litres of ‘neutronium’ would weigh 1000 billion tons!

The youngest elements

Image: Petalite block 30 cm across, a lithium aluminium silicate mineral.
Petalite block 30 cm across, a lithium aluminium silicate mineral.

Some elements are formed when other elements split into two. This may happen either through spontaneous radioactive fission or when an atom’s nucleus is hit by high-energy cosmic rays.

Beryllium-copper alloy non-sparking tools from Safety Tools Ltd.
Beryllium-copper alloy non-sparking tools from Safety Tools Ltd.
Boracic powder, a compound of boron, hydrogen and oxygen.
Boracic powder, a compound of boron, hydrogen and oxygen.

All of the helium on Earth comes from the radioactive fission of other elements. Three other very light elements - lithium, beryllium and boron, are formed when cosmic rays split heavier elements. The source of those cosmic rays is the supernovae (exploding stars) that create iron and many of the heavier elements.