Pune – Astronomers at the Inter-University Centre for Astronomy and Astrophysics (IUCAA) in Pune have achieved one of the most precise measurements yet of the universe’s expansion rate, using a special type of star known as a Mira variable.
The research team, led by Professor Anupam Bhardwaj, studied 40 oxygen-rich Mira stars across 18 star clusters in the Milky Way. With accurate distance data from the European Space Agency’s Gaia mission, they established a highly precise link between a Mira star’s brightness and the period of its brightness cycle.
This breakthrough allowed the team to measure the Hubble constant – the rate at which the universe is expanding – with a remarkable 3.7% precision. Their findings have been published in the Astrophysical Journal.
What Makes Mira Stars Special?
Mira stars, also known as Omicron Ceti, are giant stars in the final stages of their life. They pulsate regularly, changing in brightness over a fixed cycle. Because their intrinsic brightness can be determined from this cycle, they can act as “standard candles” – objects in space whose actual brightness is known, enabling scientists to calculate their distance from Earth.
Professor Bhardwaj explained:
“We used Mira stars in our galaxy as anchors for the first time to calculate the cosmic expansion rate. These stars are less affected by metal content than Cepheids, which makes them a very reliable tool.”
Implications for the Hubble Tension
The study adds fresh weight to the ongoing debate known as the Hubble tension – the discrepancy between different methods of measuring the universe’s expansion.
Nobel laureate Adam Riess, a co-author from Johns Hopkins University, said:
“This work shows that the Hubble tension is real and not due to mistakes in measurement, possibly hinting at new physics.”
Dr Marina Rejkuba of the European Southern Observatory added:
“This research proves Mira stars can serve as a new and strong anchor in measuring the Hubble constant, with long-term impact for cosmology.”
A Step Toward Unlocking Cosmic Mysteries
By adding Mira stars to the toolkit of distance markers, scientists now have another reliable method to probe the scale and fate of the universe. The findings could help refine cosmological models and shed light on the fundamental physics driving cosmic expansion.
Source: Reported by Dheeraj Bengrut
Image Source: Google | Image Credit: Respective Owner
