Astronomers have made an exciting discovery about one of the heaviest pairs of stars designated as NGC 3603-A1. Led by Dr. Phil Massey of Lowell Observatory, a team of researchers used data from the Hubble Telescope and new observations to study this massive binary star system in unprecedented detail. Their findings, set to be published in The Astrophysical Journal, shed light on how some of the universe’s biggest stars live, evolve, and die.
Located 25,000 light-years away in a vibrant star-forming region called NGC 3603, the NGC 3603-A1 system consists of two enormous stars locked in a rapid orbit.
These stellar giants circle each other about every four days, meaning that in the time it takes Earth to orbit the Sun once, these stars complete nearly 100 orbits around each other. One star is about 93 times the mass of our Sun, while the other is roughly 70 times as massive, making them among the heaviest binary stars ever directly measured in the Milky Way.
What makes these stars stand out is not just their size but their intense brightness and power. They release strong winds and radiation, giving them the appearance of Wolf-Rayet stars, which are typically older stars nearing the end of their lives. However, the stars in NGC 3603-A1 are surprisingly young, showing how extreme conditions can make massive stars seem more evolved than they are.
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The discovery was a team effort that began with a key insight from Sarah Bodansky, who was an undergraduate student at Carleton College during the summer of 2020. While working remotely at Lowell Observatory, she noticed something in older Hubble data that others had missed: the stars’ spectral features doubled when they moved toward and away from Earth, revealing their binary nature.
By carefully studying both new and archived Hubble data, the team measured the stars’ sizes, temperatures, and interactions. They found that the smaller star appears to have taken mass from its larger companion, causing it to spin faster. This mass transfer is a crucial clue to how massive stars change over time and what happens when they eventually die, often in dramatic supernova explosions or by collapsing into black holes.
The NGC 3603-A1 system is also significant because massive binary stars like these are thought to be the ancestors of binary black holes. When these stars die, they can form pairs of black holes that eventually merge, creating gravitational waves — ripples in space-time first detected in 2015. By studying systems like NGC 3603-A1, scientists gain insights into these cosmic events.
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