Runaway star ‘may have spawned the solar system’

An artist rendition released by the European Space Agency on Wednesday, Nov. 28, 2007 shows the main bodies of the solar system, the Sun, Mercury, Venus, the Earth, from left in foreground, Uranus, Neptune, Saturn, Jupiter and Mars, from left in background. The Moon, the Earth's natural satellite, is seen at right in foreground, as the relative size of the orbits of the planets is not respected. Nearby planet Venus is looking a bit more Earth-like with frequent bursts of lightning confirmed by a new European space probe. For nearly three decades, astronomers have said Venus probably had lightning, ever since a 1978 NASA probe showed signs of electrical activity in its atmosphere. But experts were not sure because of signal interference. (AP Photo/ESA/HO) ** MAGAZINES OUT - NO SALES **

A single runaway star that escaped its family, not the usual close-knit stellar clan, may have spawned solar system, say planetary scientists.

Meteorites that contain bits of rock called calcium -aluminium-rich inclusions suggest that the solar system may have formed very quickly from the ashes of other stars.

That’s because the inclusions formed with the radioactive isotope aluminium-26, which is forged inside stars tens of times as massive as the sun and decays with a half-life of only 720,000 years.

But, a team, led by Vincent Tatischeff of the National Centre for Scientific Research in France, claim that a massive star cluster would have been so hot that most of the Al-26 would have decayed before planets could congeal.

Instead, the scientists say that the solar system sprang from a solitary star’s ashes, which could have cooled more quickly, the ‘New Scientist’ reported.

And, to account for the amount of Al-26 observed in meteorites, the star would still have had to be massive, meaning it probably formed in a clutch of other stars, say the planetary scientist.

At some point, it may have been flung out of its birth cluster by gravitational tussles with its siblings or the explosion of a companion. “The scenario may look complicated, but we think it is the most likely origin of the aluminium-26 in the solar system,” Tatischeff said.

As it zipped through interstellar space, the star would have released Al-26 in winds, forming a shell of material around it. When the star later exploded, its remains would have slammed into this shell, creating a turbulent region with areas dense enough for the sun to form.

Tatischeff has said most of the galaxy’s planetary systems may not have formed as quickly as ours, since many probably arose from clusters. This makes them likely to have lower levels of Al-26, which generates heat as it decays.

The cooler temperatures may have led rocky planets to take a different evolutionary path to Earth, perhaps becoming ocean worlds, according to the findings to be published in the ’Astrophysical Journal Letters’ journal.