Somewhere in the galaxy, we have a long-lost family. At this very minute, there are hundreds to thousands of stars that began to form and shine in the same dust cloud as our Sun, whose current locations are unknown in the sea of other stars. But what if it were possible to test stars to find our stellar siblings, like a DNA test can reveal unknown family members for humans on Earth? Astronomers think its doable and, whats more, we may have already done it.Although the Sun was born billions of years ago, we know roughly how the process happened by studying stellar nurseries we see today, called nebulae. Nebula means cloud in Latin, and each consists of interstellar gas, primarily hydrogen and helium with trace amounts of other elements. Many nebulae are inert, with no star formation happening in them, their presence betrayed only by the dark regions they form as they block light from more distant stars. In fact, if these dark nebulae did not exist, the Milky Way in our night sky would be much brighter. On the other hand, nebulae that are home to star formation are positively glowing, and several are so bright you can spot them with the naked eye.

Millions of years before the Sun formed, something disturbed the dark nebula containing the gas that would become our solar system. Astronomers believe they know what caused it: a massive explosion from a dying star, called a supernova.

A blast wave from a supernova can trigger star formation in the shock front [the leading edge of the explosion] if the material is dense enough, explains Anna Rosen, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics. The key to this origin is locked in a surprising location: meteorites.

Meteoroids as meteorites are known when still in space are small chunks primarily made of iron, nickel, and trace amounts of other materials. The composition of most has not changed since the solar system formed; whats more, because they are the only part of outer space that can be physically carried into a laboratory on Earth, they are well studied. In examining them, scientists have discovered elements in amounts only possible if a supernova occurred just tens of thousands of years before the meteorites formed.

We see further evidence all around us. The elements in our world (except hydrogen and helium) formed in stars that died before our Sun was born, from the carbon in your cells to the oxygen in your lungs to the iron in your veins. These elements were then part of the material in our parent nebula that ended up forming Earth. As Carl Sagan said, We are made of starstuff.

After the supernovas shock wave passed through the cloud that would become the solar system, the dust and gas began to collapse in on itself due to gravity. More and more material fell onto it, forming a dense core, known as a protostar, that would become the Sun, and a protoplanetary disk of gas that would eventually become the rest of the solar system.

The Sun was not yet shining at this point. A protostar is not yet fusing hydrogen, so no ancient aliens would see our developing Sun, at least in wavelengths of visible light. There would be a lot of heat from all the collapsing gas, however, so the system would emit infrared radiation. Altogether, the Sun probably spent half a million years as a protostar, although accreting gas in the earlier stages could have taken many times longer.

Go here to read the rest:

Astronomers think they can find the Sun's lost siblings - Astronomy Magazine