Star birth can be a violent and explosive event, as dramatically illustrated in new ALMA images.Around 500 years ago, a pair of adolescent protostars had a perilously close encounter that blasted their stellar nursery apart. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have examined the widely scattered debris from this explosive event, gaining new insights into the sometimes-fierce relationship among sibling stars.
Shortly after starting to form some 100,000 years ago, several protostars in the Orion Molecular Cloud 1 (OMC-1), a dense and active star factory about 1,500 light-years from Earth just behind the Orion Nebula, latched onto each other gravitationally and gradually drew closer.
Eventually, two of these stars either grazed each other or collided, triggering a powerful eruption that launched other nearby protostars and hundreds of giant streamers of dust and gas into interstellar space at speeds greater than 150 kilometers per second. This cataclysmic interaction released as much energy as our Sun emits over the course of 10 million years. Today, the remains of this spectacular explosion are visible from Earth.
“What we see in this once calm stellar nursery is a cosmic version of a 4th of July fireworks display, with giant streamers rocketing off in all directions,” said John Bally with the University of Colorado and lead author on a paper published in the Astrophysical Journal.
Groups of stars such as those in OMC-1 are born when a cloud of gas hundreds of times more massive than our Sun begins to collapse under its own gravity. In the densest regions, protostars form and begin to drift about randomly. Over time, this random motion can dampen, which allows some of the stars to fall toward a common center of gravity, usually dominated by a particularly large protostar.
If these stars draw too close to each other before they drift away into the galaxy, violent interactions can occur.
According to the researchers, such explosions are expected to be relatively short lived, with the remnants like those seen by ALMA lasting only centuries.
“Though fleeting, protostellar explosions may be relatively common,” said Bally. “By destroying their parent cloud, as we see in OMC-1, such explosions may also help to regulate the pace of star formation in these giant molecular clouds.”
Bally and his team observed this feature previously with the Gemini-South telescope in Chile. These earlier images, taken in the near infrared, reveal the remarkable structure of the streamers, which extend nearly a light-year from end to end.
Hints of the explosive nature of this outflow were first uncovered in 2009 with the Submillimeter Array in Hawaii. The new ALMA data, however, provide much greater clarity, unveiling important details about the distribution and high-velocity motion of the carbon monoxide (CO) gas inside the streamers. This helps astronomers understand the underlying force of the blast and the impact such events could have on star formation across the galaxy.
“People most often associate stellar explosions with ancient stars, like a nova eruption on the surface of a decaying star or the even more spectacular supernova death of an extremely massive star,” Bally says. “ALMA has given us new insights into explosions on the other end of the stellar life cycle, star birth.”
The Orion Nebula, also known as M42, is one of the brightest and most famous nebulae in the sky. The star forming region’s glowing gas clouds and hot young stars are on the right in this sharp and colorful two frame mosaic that includes the smaller nebula M43 near center and dusty, bluish reflection nebulae NGC 1977 on the left. Located at the edge of an otherwise invisible giant molecular cloud complex, astronomers have also identified what appear to be numerous infant solar systems.
Orion is a cosmic zoo, with protoplanetary disks, brown dwarfs, intense and turbulent motions of the gas, and the photo-ionizing effects of massive nearby stars as well as supersonic “bullets” — each ten times the diameter of Pluto’s orbit and tipped with iron atoms glowing bright blue, believed to have been formed one thousand years ago from an unknown violent event.
Over 13 billion years ago at least one of the domains of life may have begun in nebular clouds. If restricted to the Milky Way, which is 13.6 billion years old, the first chemical combinations would have had billions of years to become a self-replicating organism with a DNA genome long before the existence of Earth.
Nebular clouds are thought to be most likely environment for synthesizing and promoting the evolution of molecules needed for the origin of life. Giant gas nebulae such as Orion are storehouses of sugars that form ribose — the backbone of RNA. With a universe full of sugar, it’s possible that early RNA worlds were generated and are evolving in their own unique ways throughout the observable universe. RNA coding is what gave primitive cell structures the catalyst they needed to become life.
The building blocks for DNA could have been generated or combined within interstellar clouds and DNA would become part of the molecular-protein-amino acid complex. Hydrogen, oxygen, carbon, calcium, sulfur, nitrogen and phosphorus for example are continually irradiated by ions, which can generate small organic molecules which evolve into larger complex organic molecules that result in the formation of amino acids and other compounds.
Phosphorus, for example, is rare in our solar system and may have been non-existent on the early Earth; phosphorus is essential for the manufacture of DNA.
Polarized radiation in the nebula cloud leads to the formation of proteins, nucleobases and then DNA. The combination of hydrogen, carbon, oxygen, nitrogen, cyanide and several other elements, could create adenine, which is a DNA base, whereas oxygen and phosphorus could ladder DNA base pairs. Glycine has also been identified in the interstellar clouds.
In 2009, the Herschel Space Observatory using the telescope’s heterodyne instrument for the far infrared revealed the chemical fingerprints of potentially life-enabling organic molecules in the Orion nebula, one of the most prolific chemical factories in space, although the full extent of its chemistry and the pathways for molecule formation are not well understood.
The Daily Galaxy via NRAO
ALMA (ESO/NAOJ/NRAO), J. Bally; B. Saxton (NRAO/AUI/NSF); Gemini Observatory/AURA