A research team have used both archival Hubble Space Telescope data and new observations to precisely measure the binary star systems NGC3603-A1. One star weighs about 93 times the mass of our Sun, while its companion tips the scales at roughly 70 solar masses. Together, they represent one of the most massive binary systems ever discovered in our Galaxy.
What makes this system truly extraordinary is the speed of their orbital movement. The two giants orbit each other once every 3.8 days, meaning that in the time Earth completes one year around the Sun, these stellar titans will have circled each other nearly 100 times. Their proximity and incredible masses create a dynamic relationship that’s reshaping both stars.
The core of the star cluster in NGC 3603 is shown in great detail in an image from the Wide Field Planetary Camera 2 (WFPC2) camera on the NASA/ESA Hubble Space Telescope. NGC3603-A1 is the brightest (and top right) of the three barely resolved stars at the centre (Credit : NASA, ESA and Wolfgang Brandner)
The discovery required detective work that spanned years and relied on a crucial insight from an unlikely source. Sarah Bodansky, then an undergraduate student at Carleton College, was working remotely at Lowell Observatory during the pandemic summer of 2020 when she noticed something everyone had missed in the older Hubble data.
“Sarah’s work made it possible to move this project forward. She noticed something that everyone had missed: some of the spectral features doubled when the stars had their greatest motions towards and away from us. Without this discovery, the project would have languished” – Dr. Phil Massey of Lowell Observatory
This observation was key because it revealed the binary nature of what had appeared to be a single, fuzzy star. Located in the densely packed star cluster NGC 3603 which is one of the most active star forming regions in our Galaxy, the system could only be resolved using Hubble’s exceptional clarity.
Both stars are so massive and energetic that they mimic Wolf-Rayet stars, which are typically older, dying giants that blast away their outer layers with intense stellar winds. However, the stars in NGC 3603-A1 are actually still young, demonstrating the extreme conditions that can make massive stars appear far more evolved than they actually are.
The interaction between the two stars tells a fascinating story of stellar evolution. The smaller of the pair appears to have stolen mass from its larger companion, causing it to spin faster as a result. This kind of mass transfer is crucial for understanding how massive stars change over time and provides insights into their ultimate fate.
“For the most massive stars, astronomers usually have to rely on models that aren’t very well-constrained to ‘weigh’ the star. But this study focused on a special type of binary system where we can get a more fundamental measurement of its mass.” – Sarah Bodansky from Carleton College
Massive binary systems like NGC 3603-A1 are the progenitors of binary black holes, which can eventually merge and create gravitational waves that scientists have been detecting since 2015. Understanding these stellar relationships helps astronomers predict where and when such collisions might occur.
Source : Astronomers Reveal Massive Binary Star System in Milky Way
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