Saturday, June 2, 2012

Magnesium in the stars and in us

SNR N49B in the Large Magellanic Cloud.
Chandra image.

Magnesium, the eighth most abundant material in the Earth's crust, is a mineral needed by every cell of our bodies. It helps maintain normal muscle and nerve function, keeps heart rhythm steady, and bones strong. It is also involved in energy metabolism and protein synthesis. Fortunately for us, and thanks to stars such as the one that produced N49B, there is an abundant supply of magnesium in the Universe.

The Chandra image of N49B, above, the remains of an exploded star, shows a cloud of multimillion-degree gas that has been expanding for about 10,000 years. A specially processed version of this image, right, reveals unexpectedly large concentrations of the element magnesium, shown in blue.

Magnesium, created deep inside the star and ejected in the supernova explosion, is usually associated with correspondingly high concentrations of oxygen. However, the Chandra data indicate that the amount of oxygen in N49B is not exceptional. This poses a puzzle as to how the excess magnesium was created, or, alternatively, how the excess oxygen has escaped detection.

The amount of magnesium in N49B is estimated to be about equal to the total mass of the Sun. Since the Sun contains only about 0.1 percent of magnesium by mass, the total mass of magnesium N49B is about a thousand times that in the Sun and its planets.
NASA Chandra news March 24 2004

See also the nice video about stars producing stuff citing Carl Sagan "We are made of star stuff" Chandra X-ray study of Cassiopeia A supernova NASA Science  youTube

Magnesium on Earth and in the cosmos
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2.

It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole.

Magnesium is the fourth most common element in the Earth as a whole (behind iron, oxygen and silicon), making up 13% of the planet's mass and a large fraction of the planet's mantle.

Due to magnesium ion's high solubility in water, it is the third most abundant element dissolved in seawater.

The relative abundance of magnesium is related to the fact that it is easily built up in supernova stars from a sequential addition of three helium nuclei to carbon (which in turn is made from three helium nuclei).

Magnesium is produced in stars larger than 3 solar masses by fusing helium and neon in the alpha process at temperatures above 600 megakelvins.

Magnesium in living organisms
In human biology, magnesium is the eleventh most abundant element by mass in the human body;

its ions are essential to all living cells, where they play a major role in manipulating important biological polyphosphate compounds like ATP, DNA, and RNA. Hundreds of enzymes thus require magnesium ions to function.

Magnesium compounds are used medicinally as common laxatives, antacids (e.g., milk of magnesia), and in a number of situations where stabilization of abnormal nerve excitation and blood vessel spasm is required (e.g., to treat eclampsia).

Magnesium ions are sour to the taste, and in low concentrations they help to impart a natural tartness to fresh mineral waters.

In vegetation magnesium is the metallic ion at the center of chlorophyll, and is thus a common additive to fertilizers.

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