Astronomers have unveiled intricate details of the star-forming region 30 Doradus, also known as the Tarantula Nebula, using new observations from the Atacama Large Millimeter/submillimeter Array (ALMA). In a high-resolution image released by the European Southern Observatory (ESO) and including ALMA data, we see the nebula in a new light, with wispy gas clouds that provide insight into how massive stars shape this region.
Astronomers have peered into a teeming stellar nursery in the Tarantula Nebula – a colossal cloud of gas and dust next door to our galaxy – gaining new understanding of the dynamics of star formation while obtaining a dazzling image of the cosmos.
Researchers on Wednesday said their observations offered insight into the interplay between the irresistible force of gravity that drives star formation and the huge amounts of energy that massive young stars inject into their nearby environments that could inhibit stellar birth.
The Tarantula Nebula, residing in a satellite galaxy of the Milky Way called the Large Magellanic Cloud, is a web of stars, gas and dust with a diameter around 600 light-years. A light year is the distance light travels in a year – 5.9 trillion miles (9.5 trillion km).
Located about 170,000 light years from Earth, the Tarantula Nebula is formally named 30 Doradus, referring to a catalog number for objects in the direction of the constellation Dorado.
It is called the Tarantula Nebula because some of its architecture appears as glowing filaments of gas, dust and stars reminiscent of spider legs. The nebula’s gas composition is similar to the universe’s earlier in its history, mostly just hydrogen and helium.
Tarantula Nebula is one of the brightest and most active star-forming regions in our galactic neighbourhood. At its heart are some of the most massive stars known, a few with more than 150 times the mass of our Sun, making the region perfect for studying how gas clouds collapse under gravity to form new stars.
The European Southern Observatory released a Tarantula Nebula image showing wispy gas clouds that may be remnants of larger ones ripped apart by energy unleashed by massive young 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,” says Tony Wong, who led the research on 30 Doradus presented at the American Astronomical Society (AAS) meeting and published in The Astrophysical Journal.
“We see stars forming where there is a lot of gas and dust available, and there is definitely a lot of it in the Tarantula Nebula,” said astrophysicist Guido De Marchi of the European Space Agency’s European Space Research and Technology Centre in the Netherlands, co-author of the research published in the Astrophysical Journal and presented at an American Astronomical Society meeting.
The findings were aided by observations using the Chile-based ALMA telescope.
“Stars form when gas clouds collapse under their own gravity and the gas gets denser and denser. These clouds contract and warm up until the core is hot enough to start the stellar engine, an immense nuclear reactor,” De Marchi said.
“But we always thought that when massive stars – over 100 times more massive than the sun – begin to form they release so much energy that it prevents the infall of more gas, shutting off the fuel for more stars to form. The beautiful observations of the Tarantula Nebula obtained with ALMA now show that where the gas is dense enough it continues to fall unabated and new stars can keep forming. This is interesting and new,” he said.
De Marchi was referring to a phenomenon called feedback, with massive young stars emitting large amounts of energy into their local environments in the form of photons and high-speed particles. The nebula’s primordial composition has fostered the formation of particularly large stars, some 200 times as massive as our sun.
“The Tarantula Nebula is the most extreme feedback environment that we can observe in detail because it hosts the nearest example of a massive young star cluster,” University of Illinois astrophysicist and study lead author Tony Wong said.
“One of the big mysteries in astronomy is why we are still able to witness stars forming today. Why didn’t all of the available gas collapse in a huge burst of star formation that came and went long ago? Observations with ALMA can shine a light on what is happening deep within clouds and help us understand how gravity and feedback compete for influence to keep the rate of star formation under control,” Wong added.
The nebula’s sheer beauty was not lost on the researchers.
“I personally love the Tarantula Nebula, both scientifically and aesthetically,” De Marchi said. “It is just an iconic scene in the sky. I have often wondered what the night would look like if we were on a planet around one of its stars, with colorful bright clouds and strings of gas crisscrossing the sky.”
“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,” said Guido De Marchi. “Thanks to 30 Doradus, we can study how stars used to form 10 billion years ago when most stars were born.”
Astronomers originally thought the gas in these areas would be too sparse and too overwhelmed by this turbulent feedback for gravity to pull it together to form new stars. But the new data also reveal much denser filaments where gravity’s role is still significant. “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,” adds Wong, who is a professor at the University of Illinois at Urbana-Champaign, USA.
In the image released by ESO, we see the new ALMA data overlaid on a previous infrared image of the same region that shows bright stars and light pinkish clouds of hot gas, taken with ESO’s Very Large Telescope (VLT) and ESO’s Visible and Infrared Survey Telescope for Astronomy (VISTA). The composition shows the distinct, web-like shape of the Tarantula Nebula’s gas clouds that gave rise to its spidery name. The new ALMA data comprise the bright red-yellow streaks in the image: very cold and dense gas that could one day collapse and form stars.
The new research contains detailed clues about how gravity behaves in the Tarantula Nebula’s star-forming regions, but the work is far from finished. “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 concludes. (ESO/Reuters)
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