Science Result: Surprisingly Young Nebula Hints at Formation of Stars in the Early Universe

Astronomers are still trying to understand how stars and galaxies formed in the early universe. Now, scientists have new clues from a glowing nebula filled with clouds of hot gas and dust, known as RCW 120. Data from NASA’s Stratospheric Observatory for Infrared Astronomy, or SOFIA, suggest that this nebula may be representative of how stars formed in the early universe.

Composite image of the nebula RCW 120
Composite image of the nebula RCW 120. The ring-shaped clouds around the nebula were detected by the Spitzer Space Telescope. SOFIA measured the glowing gas shown in red and blue to study the nebula’s expansion speed and determine its age. The blue gas represents gas expanding in the direction toward Earth and the red away from Earth. The expansion is triggering the birth of stellar neighbors at breakneck speeds – and revealing the nebula is younger than previously believed. Credit: NASA/JPL-Caltech/SOFIA

Scientists using SOFIA, a joint project of NASA and the German Space Agency at DLR, found the stellar wind emanating from the nebula’s central massive star is making the nebula expand rapidly. The expansion is triggering the birth of stellar neighbors at breakneck speeds – and revealing the nebula is younger than previously believed. The results are published in Science Advances.

In the southern Milky Way, about 4,300 light-years from Earth, in clouds near the constellation Scorpius, researchers discovered that the powerful stellar winds are expanding the nebula incredibly fast at 33,000 miles per hour (about 53,000 kilometers per hour). The surrounding gas clouds are getting compressed as the nebula pushes into them – triggering the birth of new stars near the clouds’ edges.

The expansion speed was also used to determine the nebula’s age. It turns out RCW 120 is much younger than previously believed, having formed less than 150,000 years ago. This discovery provided a clue about the universe’s distant past.

“The nebula is giving us a window into what star formation may have been like in the early universe,” said Dr. Matteo Luisi, a postdoctoral fellow at West Virginia University in Morgantown, West Virginia. “We can’t go back to study the early universe, so we depend on observations like these to understand how it transformed from the Big Bang to the universe we see today.”

Astronomers call the effects stars have on their neighbors’ creation “feedback.” But exactly how feedback can help or hinder star formation is still somewhat of a mystery. SOFIA previously found that a stellar wind in the Orion Nebula is clearing a bubble free of material needed to form new stars. Now, in the nebula RCW 120, the energy from the original star is triggering the birth of new generations.

The nebula’s young age suggests that star formation triggered by an existing star’s feedback can happen very quickly and may have been responsible for the high rate of star formation in the universe’s earliest eras.

The observations were made while flying in the skies above Christchurch, New Zealand, in 2019. Using SOFIA’s instrument called the German Receiver for Astronomy at Terahertz Frequencies, or GREAT, researchers studied the chemical fingerprint of ionized carbon gas to measure the nebula’s expansion speed. Unlike infrared images, this fingerprint measures how fast the gas is moving, which can be used to learn how existing stars are affecting future generations. These results are part of an international project to understand the effects of stellar feedback in a variety of star-forming regions.

DLR is NASA’s partner on SOFIA, providing the telescope, scheduled aircraft maintenance, and other support for the mission. NASA’s Ames Research Center in California’s Silicon Valley manages the SOFIA program, science, and mission operations in cooperation with the Universities Space Research Association, headquartered in Columbia, Maryland, and the German SOFIA Institute at the University of Stuttgart. The aircraft is maintained and operated by NASA’s Armstrong Flight Research Center Building 703, in Palmdale, California.