O-Type Stars Act as 'Death Stars,' Sucking Away Planet-Forming Matter

The enormous cloud of gas and dust known as the Orion Nebula is a birthing ground for stars, and some of these stars are formed under conditions that could lead to them eventually forming into planets. But new research reveals that a class of highly luminous stars known as O-type stars can essentially function as "death stars," destroying all the material necessary for planet formation.

A class of young protostars known as proplyds have been observed falling victim to the planet-draining forces of O-type stars, as documented in a new paper published in in The Astrophysical Journal.

Using the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile to document the relationship between proplyds and O-type stars, a team of American and Canadian astronomers found that protostars within 0.1 light years of an O-type star are doomed to have their shells of planet-building gas and dust stripped away in just a few million years, much quicker than planets are able to form.

"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," said lead study author Rita Mann, an astronomer with the National Research Council of Canada in Victoria. "Using ALMA, we looked at dozens of embryonic stars with planet-forming potential and, for the first time, found clear indications where protoplanetary disks simply vanished under the intense glow of a neighboring massive star."

Due to their high temperature and high luminosity, O-type stars end their lives rather quickly. But the ongoing process of star formation relies upon short-lived O-type stars stationed within large, interstellar clouds of gas and dust, the researchers contend.

At the end of these O-type stars' lives, they turn into supernovas, which explode with such force that the surrounding area is blanketed with dust and heavy elements that will get taken up by the next generation of stars.

But these O-type stars are deadly for nascent planetary systems that stray too close.

"Massive stars are hot and hundreds of times more luminous than our Sun," said James Di Francesco, also with the National Research Council of Canada. "Their energetic photons can quickly deplete a nearby protoplanetary disk by heating up its gas, breaking it up, and sweeping it away."

The researchers found that any protostar within the extreme-UV field of a massive star would lose most of its planet-building material in no time. However, if the protostars are beyond the 0.1 light year UV threshold, they are capable of retaining much of their planet-building material

"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," said Mann. "This work is really the tip of the iceberg of what will come out of ALMA; we hope to eventually learn how common solar systems like our own are."