Top of the list has to be the X-ray pulsar PSR J0537–6910. This object formed when a massive star exploded about 5,000 years ago (as seen from Earth), leaving behind a rapidly spinning neutron star. Not only is this pulsar the most energetic one known, but it is also the fastest rotating young pulsar. It spins once on its axis every 16 milliseconds, more than twice as fast as the pulsar at the center of the Milky Way’s Crab Nebula. The supernova remnant associated with the stellar explosion, N157B, also can be seen in NGC 2060.
The cluster likewise harbors the fastest rotating normal star, VFTS 102. The VLT-FLAMES survey found this star’s equatorial regions spinning at a rate of 1.4 million mph (2.2 million km/h), or some 300 times faster than the Sun. The rapid rotation means VFTS 102’s shape more closely resembles an M&M than a sphere.
These three regions tell only part of the Tarantula’s story. Massive stars are spread across the entire region, with some of them apparently flung from their birthplaces. VFTS 016, for example, is a massive runaway star located well to the northwest of NGC 2060. Discovered as a fast mover during the initial stages of the VLT-FLAMES survey, the team only managed to measure its line-of-sight velocity. Eight years later, the researchers used data from the European Space Agency’s Gaia spacecraft to pin down its speed: 225,000 mph (360,000 km/h)! Its position and motion indicate it was ejected from R136 about 1.5 million years ago and has since traversed 375 light-years. The scientists suspect the star once belonged to a binary system that suffered a rogue encounter with a third star, launching it on its epic journey.
Probe of the distant universe
Studying massive binary systems in the Tarantula was one of the motivating forces behind the VLT-FLAMES survey. The results are startling: “We estimate that at least 50 percent of our targets are in binary systems,” says Evans. “Alongside complementary studies in our own Milky Way, this result has significantly changed our perspective on stellar evolution.”
Close binaries can interact in many ways, he adds. Mass and angular momentum can be transferred from one star to the other, and eventually the two stars can merge. “This results in very different evolutionary paths than if [they were] born as single stars.” Some of these systems may develop into binary black holes and ultimately merge, producing a torrent of gravitational waves like those from similar systems that astronomers began detecting in 2015. Not surprisingly, the current record holder for a massive binary system, Melnick 34, resides in the Tarantula. Each of its two components weighs in at about 120 solar masses.
The biggest opportunity to arise from the HTTP has been to study the lifecycle of a starburst from up close. “The Tarantula Nebula has been forming stars for the past 30 million years,” says Sabbi. “The epicenter of star formation during this time has moved considerably, and we can see how powerful stellar winds and violent supernova explosions have shut down star formation in one region of the Tarantula, just to start it again a few hundred light-years away.”
What has happened just recently in the Tarantula may be a window into the universe’s early history. Casting their gaze outward, astronomers detect what seem to be similar starbursts in galaxies so distant that universal expansion has shifted their light far toward the red end of the spectrum. “The Tarantula’s properties appear to be comparable to knots of intense star formation in young galaxies at high redshift, so it gives us a local clue to galaxy assembly in the early universe,” says Crowther.
Using the Tarantula as a model for these systems offers one more advantage over any potential Milky Way counterparts: The Tarantula and the surrounding LMC have far fewer heavy elements than star-forming regions in our own galaxy. The amount of metals — astro-speak for elements heavier than helium that stars have cooked up over the eons — in the LMC is only half that of the Milky Way, making it much more similar to the more pristine material present in the distant, early cosmos. With the Tarantula, it’s almost as if astronomers have stumbled on their own Rosetta Stone, and have started using it as a key to understanding the mysteries of star and galaxy formation.
Scientists have been fortunate to have front-row seats to the Tarantula’s display. “We’re lucky to be witnessing these fireworks when the Large Magellanic Cloud is on its closest approach to the Milky Way in the last billion years or so,” says Crowther. Alas, the performance may not run that much longer. “Much of the gas from the original molecular cloud has now turned into stars, so we expect the rate of star formation to decline in the next few million years.”
When the show eventually ends, every astronomer in the house will say it had a great run.