The Orion Nebula looks peaceful from Earth, but deep within this stellar birthplace, young stars are attacked by bright, older "death stars."
Within a vast cloud of gas, hundreds of young stars are collapsing, triggering thermonuclear reactions. These bodies collect some of the gas around them to fuel growth, while pushing some away through stellar winds. Some of the material will remain, and form into planets, asteroids and comets.
Danger lies nearby, however, for these young star systems in the form of ultra-bright O-class stars. Ultra-violet light coming from these bodies pushes at the gas and dust surrounding the protostars. Some of the youngest of these stars are known as proplyds.
Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, astronomers from Canada and the United States were able to investigate the effect.
They measured how UV radiation from the massive stars affected protoplanetary disks in the nebula. Observations revealed any young star within one-tenth of a light year (600 billion miles) of an O-class star would be stripped of its disk in less than 100 million years. This would not leave enough time for planet formation.
Photographs taken by the Hubble Space Telescope show many of the stars within the nebula are pushed into the shape of teardrops by the powerful electromagnetic radiation.
"O-type stars, which are really monsters compared to our Sun, emit tremendous amounts of ultraviolet radiation and this can play havoc during the development of young planetary systems," Rita Mann, astronomer with the National Research Council of Canada, said.
Observations from ALMA were combined with data obtained by the Submillimeter Array (SMA) in Hawaii. This study was able to double the number of proto-planetary systems known in that region of space, more than 1,300 light years from Earth.
Most stars, like our own Sun, are born within giant clouds of gas and dust similar to the Orion Nebula. After stars and planetary systems form, they drift off into space.
Ironically, these large stars that hinder or prevent planet formation may help give birth to new systems. Massive stars live much shorter lives than smaller bodies and can explode violently when they die. Shockwaves from these traumatic deaths can trigger new star formation within the gas cloud.
"Taken together, our investigations with ALMA suggest that extreme UV regions are not just inhospitable, but they're downright hazardous for planet formation. With enough distance, however, it's possible to find a much more congenial environment," Mann said.
This stellar nursery can easily be viewed from anywhere in the northern hemisphere as the fuzzy middle "star" in the sword of Orion.
Details of the study were reported in the Astrophysical Journal.
