- The star in the Southern Cross constellation is 14.5 times heavier than Earth’s Sun
- Researchers find that Beta Crucis, also known as Mimosa, is just 11 million years old
- It is the heaviest of the thousands of stars that determine their age.
- By comparison, our Sun is 4.5 billion years old and has a mass of 330,000 Earths.
It is one of the most famous constellations in the sky of the Southern Hemisphere and has served as a compass for explorers for centuries.
But now the Southern Cross has got another claim to fame.
It turns out to be the second-brightest object within the constellation, a bright blue giant called Beta Crucis, 14.5 times heavier than Earth’s Sun and just 11 million years old.
It is the heaviest of the thousands of stars whose ages are determined by asteroseismology.
By comparison, our Sun is thought to be around 4.5 billion years old and has a mass of over 330,000 Earths.
The discovery was made by a team of scientists led by Dr Daniel Cotton from the Australian National University and the Monterey Institute for Research in Astronomy in the US.
The second-brightest object within the Southern Cross constellation (pictured), a bright blue giant called Beta Crucis, is 14.5 times heavier than Earth’s Sun and just 11 million years old.
What is Asteroseismology?
Asteroseismology is the study of how stars pulsate or oscillate.
This is a relatively new technique that involves measuring the oscillations caused by trapped sound waves inside a star, which allows scientists to gather information about the size and internal structure of the star.
It also enables astronomers to accurately estimate the age of the star.
At only 11 million years old and with a mass 14.5 times that of Earth’s Sun, Beta Crucis is the heaviest of the thousands of stars whose ages have been determined by astronomy.
The researchers figured out the age and mass of Beta crucis, also known as the mimosa, by combining asteroseismology and polarimetry.
The first is the study of a star’s regular movements and relies on seismic waves bouncing around inside it and producing measurable changes in its light.
Polarimetry, on the other hand, measures the orientation of light waves.
However, probing the interiors of massive stars that would later explode as supernovae has traditionally been difficult.
‘I wanted to examine an old idea,’ said Cotton.
‘In 1979 it was predicted that polarimetry has the ability to measure the interiors of massive stars, but this has not been possible until now.’
Study co-author Professor Jeremy Bailey from the University of New South Wales (UNSW) said: ‘The effect size is quite small.
‘For the project to be a success we needed the world’s best accuracy of polarimeters designed and manufactured at UNSW.’
The Southern Cross is an important symbol of nationality for many countries, with the flags of Australia, New Zealand, Australia, Samoa, Brazil and Papua New Guinea.
The study of Beta Crucis, 280 light-years from Earth, combines three different types of measurements of its light.
The Southern Cross (pictured) is an important symbol of nationality for many countries, with the flags of Australia, New Zealand, Australia, Samoa and Papua New Guinea.
First, the researchers used space-based measurements of light intensity from two NASA satellites, TESS and WIRE.
They also used 13 years of ground-based high-resolution spectroscopy, a study of the absorption and emission of light and other radiation, from the European Southern Observatory.
Finally, the team used ground-based polarimetry collected from Siding Spring Observatory and Western Sydney University’s Penrith Observatory.
‘It was a fortunate circumstance that we were able to use the world’s most accurate astronomical polarimeter to make so many observations of mimosa in the Anglo-Australian Telescope,’ said fellow study author Professor Derek Bujasi from the Florida Gulf Coast, while also observing the TES star. was looking at University.
‘Analyzing the three types of long-term data together allowed us to identify the major mode geometry of the mimosa.
‘This opened the way for star weighing and age-dating using seismic methods.’
Professor Connie Aerts from KU Leuven said: ‘This polar study of Mimosa has opened a new avenue for asteroid science of bright massive stars.
‘Although these stars are our galaxy’s most productive chemical factories, they are by far the least analyzed, given the degree of difficulty of such studies.’
The researchers hope their findings will provide new insights into how stars live and die, and how they affect the chemical evolution of the Milky Way.
The study has been published in the journal nature astronomy,
Milky Way’s oldest star
A newly discovered star is believed to be one of the oldest in the Milky Way.
Scientists at the Instituto de Astrofísica de Canarias (IAC) in Spain believe that it may have formed about 300 million years after the ‘Big Bang’.
IAC researcher Joanne González Hernández said: ‘The theory predicts that these stars may have formed immediately after and using material from the first supernova, whose ancestors were the first massive stars in the Milky Way.’
The researchers hope that the star known as J0815+4729, which corresponds to the Lynx constellation, will help them learn more about the Big Bang, the popular theory about galaxy evolution.
IAC Director Rafael Rebolo said: ‘The detection of lithium gives us important information related to Big Bang nucleosynthesis. We are working on high resolution and wide spectral range spectrographs to be able to measure the detailed chemical composition (among other things) of stars with unique properties like J0815+4729.’