A star 10 times as hot and 40 times the size of our sun but no more than 2,000 years old has been observed in the Orion Nebula by astronomers at the Kitt Peak National Observatory in Arizona.
"This may be the youngest star ever found," said Kitt Peak's Dr. Donald N. B. Hall, who with three other astronomers identified it with the 158-inch telescope on top of Kitt Peak. "The star is surely in its earliest stages of evolution."
So freshly formed is the star that its tremendous heat is blowing gas and dust away from it at speeds of 60,000 m.p.h. The far edge of this gas-and-dust cloud lies almost one-fifth of a light year away from the star, meaning the cloud is now as far as 1 million miles from the star.
The speed at which the cloud is moving away from the star is the most precise measurement of the age of the star, Hall said. Infrared instruments attached to the telescope did this by measuring the rate of expansion of the cloud's carbon monoxide, an important constituent of any interstellar dust cloud, and then computing how long ago the cloud began moving.
"This is how we know the object is a star and not what is called a 'protostar,' one still in the process of formation," Hall said. "A protostar is one that is still in the process of collapse and is still accreting matter onto itself.This one is blowing matter away."
The star in question lies beyond the constellation Orion in the middle of the Orion Nebula, which is surrounded by thick gas and dust clouds believed to be the breeding grounds of many new stars. The star is near four protostars known as the Trapezium at the center of the Orion Nebula.
Known as the Becklin-Neugebauer star for the two astronomers who discovered it in 1966, the 2,000-year-old star is almost completely hidden by the dust clouds around it. Only infrared instruments that pierce the clouds can see it, and only the infrared instruments used by Hall's team on the Kitt Peak telescope have been able to get detailed measurements of it.
A star is born when swirling interstellar dust clouds collapse under their own weight, shrinking down in a ball that gets hotter and smaller all the time. The collapsing cloud reaches a "critical mass" that triggers a nuclear fusion reaction where the hydrogen gas in the cloud is ignited and burns until the hydrogen fuel is exhausted.
Once the cloud is ignited into a star, it rapidly evolves to a stable state astronomers call the "main sequence." The Becklin-Neugebauer star is now about 2,000 years into its main sequence, a state it will sustain for at least 1 million years.
Before the Kitt Peak observations, the youngest stars identified anywhere in the universe were estimated to be between 50,000 and 100,000 years old. Many of these young stars have been identified inside the Orion Nebula, which has often been called a stellar nursery.
Kitt Peak's Dr. Hall estimates that the Becklin-Neugebauer star sometime in the next 10,000 years will drift out of the interstellar cloud obscuring it from sight.
One reason it will do so is that the force of its own formation gave it enough velocity that the star is now moving at enough speed through space to carry it away from the cloud eventually.