A newly released image of 30 Doradus, also known as the Tarantula Nebula, reveals thin spider-web-like strands of gas revealing a dramatic battle between gravity and stellar energy that could give astronomers an idea of how massive stars have shaped this star-forming region and why they continue to be birthed within this molecular cloud.
The high-resolution image of the Tarantula Nebula, located 170,000 light-years from Earth is made up of data collected by Atacama Large Millimeter/submillimeter Array (ALMA). Located in the Large Magellanic Cloud, a satellite galaxy of the Milky Way, the Tarantula Nebula is one of the most luminous star-forming regions in our galactic backyard. It is also one of the most active in terms of birthing new stars, — some of which have masses more than 150 times that of the sun. At theits heart of the Large Magellanic Cloud lies a stellar nursery that has given rise to 800,000 stars , — half a million of which are hot, young, and massive stars.
This makes the nebula a prime target for researchers who want to study star formation, and it has another unique property that makes it an exciting prospect for research study.
"What makes 30 Doradus unique is that it is close enough for us to study in detail how stars are forming, and yet its properties are similar to those found in very distant galaxies when the Universe was young,"” European Space Agency (ESA) scientist Guido De Marchi, a European Space Agency scientist and co-author of a paper describing the work, said in the statement. "Thanks to 30 Doradus, we can study how stars used to form 10 billion years ago, when most stars were born."
The battle to birth more massive stars
The "push and pull" researchers observed is created by the energy provided by its huge population of stars and gravity, with the former ripping gas clouds into strand-like fragments thus slowing star formation, and the latter attempting to bring gas clouds together to form stars.
“These fragments may be the remains of once-larger clouds that have been shredded by the enormous energy being released by young and massive stars, a process dubbed feedback,” Tony Wong, a professor from the Astronomy Department at the University of Illinois at Urbana-Champaign said in a European Southern Observatory (ESO) press release.
The findings also showed that despite intense stellar feedback, gravity is still shaping the nebula — which is located 170,000 light-years away from Earth and next to the Milky Way — and driving the continued formation of massive stars.
This contradicts the previous consensus on such star-forming regions which has suggested that thin strands of gas as seen in the Tarantula Nebula should be too disrupted by this feedback to allow gravity to pull it together and form new stars.
"Our results imply that even in the presence of very strong feedback, gravity can exert a strong influence and lead to a continuation of star formation," Wong continued.
Observing the Tarantula's Web clump by clump
Given its properties, it's unsurprising that the Tarantula Nebula has been well-studied. What makes this new research different is while previous studies have mostly focused on its center — the site of the densest gas and thus the most rapid star formation — astronomers are aware that stars are also being formed in other regions of the nebula this team collected high-resolution observations of a large region of the Tarantula Nebula rather than focusing on its heart. With this global approach to the nebula in mind they then dived it into clumps which revealed a surprising pattern.
"We used to think of interstellar gas clouds as puffy or roundish structures, but it’s increasingly clear that they are string-like or filamentary," Wong said in a National Radio Astronomy Observatory (NRAO) press release. "When we divided the cloud into clumps to measure differences in density we observed that the densest clumps are not randomly placed but are highly organized onto these filaments."
Focusing on the light emitted by carbon monoxide gas allowed the researchers to map the large, cold gas clouds in the Tarantula Nebula that collapse to form infant stars. They also observed how these gas clouds change as those young stars release a tremendous amount of energy.
"We were expecting to find that parts of the cloud closest to the young massive stars would show the clearest signs of gravity being overwhelmed by feedback," Wong said. "We found instead that gravity is still important in these feedback-exposed regions — at least for parts of the cloud that are sufficiently dense."
Overlaying the data collected by ALMA and an infrared image of the Tarantula Nebula showing bright stars and glowing hot gas from the Very Large Telescope and from the Infrared Survey Telescope for Astronomy (VISTA) creates a composite image that shows the extent of its gas clouds and their distinct web-like shape.
While the team’s findings give an indication of how gravity affects star-forming regions, the research is a work in progress. "There is still much more to do with this fantastic data set, and we are releasing it publicly to encourage other researchers to conduct new investigations," Wong concluded.
Future studies will also focus on the differences between the Milky Way and the Tarantula Nebula including star-formation rates — while our galaxy steadily forms stars, the Tarantula Nebula does so in “boom and bust” cycles.
The research on the Tarantula Nebula was presented at the 240th meeting of the American Astronomical Society (AAS) in Pasadena, California, on June 15. The findings are also presented in a paper in The Astrophysical Journal.
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