Massive stars in metal-poor galaxies have partners too: Study
What's the story
A global team of 70 astronomers has discovered that massive stars in metal-poor galaxies are often part of a binary system. The study was led by scientists from Belgium, the Netherlands, and Israel and published in Nature Astronomy. The researchers used the European Very Large Telescope in Chile to observe the velocity of massive stars in the Small Magellanic Cloud (SMC), a dwarf galaxy near our Milky Way.
Stellar evolution
Binary systems of massive stars
For the past two decades, astronomers have known that many massive stars in our metal-rich Milky Way have partners. These binary systems play a crucial role in the evolution of these stars. However, it was previously unclear if massive stars in metal-poor galaxies were also part of such systems. This new study confirms that they are, just like their counterparts in our galaxy.
Cosmic insights
Using SMC as a time machine
Hugues Sana from KU Leuven (Belgium) explained their approach by saying, "We used the Small Magellanic Cloud as a time machine." He added that the metallicity environment of SMC is representative of distant galaxies when the universe was only a few billion years old. This makes it an ideal location to study massive stars and their potential binary systems.
Observation challenges
Observing distant massive stars
Observing massive stars outside our Milky Way is difficult due to their distance and low light emission. The researchers used the FLAMES spectrograph on the Very Large Telescope of the European Southern Observatory in Chile, one of Earth's largest telescopes. It has 132 fiber optics that can be pointed at different stars for simultaneous observation.
Binary indicators
How many stars had partners?
Over three months, the researchers saw the acceleration and deceleration of 139 massive O-type stars at nine different times. These stars, which are 15 to 60 times as massive as our Sun, are hot and shine brightly before ending their lives in supernova explosions. The results showed that over 70% of these stars accelerate and decelerate, indicating a nearby partner.
Cosmic implications
Implications for early star formation
Study co-author Julia Bodensteiner from the University of Amsterdam said, "The fact that massive stars in the Small Magellanic Cloud have a partner suggests that the first stars in the universe, which we suspect were also massive, had partners too." She added this finding could mean some of those systems may have ended up as two black holes orbiting each other.