Scientists have found that matter accounts for 31% of the universe's entire makeup of matter and energy, leaving dark energy to dominate the rest.
Unveiling the amount of matter present in the vast universe has long been a pressing question for cosmologists. Now, thanks to a team of international scientists, including those from Chiba University, we have another answer. As highlighted in The Astrophysical Journal, the research reveals that matter accounts for 31% of the universe’s entire makeup of matter and energy, leaving dark energy to dominate the rest.
Distinguishing Dark from Baryonic Matter
Dr. Mohamed Abdullah, the lead author from the National Research Institute of Astronomy and Geophysics-Egypt and Chiba University in Japan, notes, “While about 20% of the universe’s total matter is what we term ‘baryonic’ (comprising stars, galaxies, atoms, and even life), a staggering 80% is dark matter.” The intricacies of this dark matter, potentially made up of yet-undiscovered subatomic particles, remain elusive.
Gillian Wilson, co-author and a senior figure at UC Merced, sheds light on the method employed. “We assessed the number and weight of galaxy clusters in a given volume and juxtaposed it with simulations,” she says. The frequency of these clusters in the present-day universe, or “cluster abundance,” reveals a lot about the universe’s material content.
Anatoly Klypin, from the University of Virginia, adds, “A universe richer in matter would naturally have more clusters. However, measuring a galaxy cluster’s mass isn’t straightforward due to the invisible nature of most of its dark matter content.”
Innovative Indicators: From Galaxy Count to Mass Measurement
To bypass the direct mass measurement challenge, the team turned to an innovative approach: counting galaxies within clusters. More galaxies indicate a heavier cluster. Using data from the Sloan Digital Sky Survey, they estimated each cluster’s overall mass, eventually matching their observations with simulation predictions.
The 31% matter composition they pinpointed strikingly aligns with findings from the Planck satellite, which employed an entirely different method.
Tomoaki Ishiyama from Chiba University remarked, “We’ve successfully matched our matter density measurements using the MRR technique with those derived from the CMB method by the Planck team.”
Fine-Tuning Techniques: Spectroscopy’s Role
The team’s breakthrough partly stems from their pioneering use of spectroscopy. This technique distinctly identifies radiation spectrums, enabling precise determination of distances to clusters and identifying true member galaxies bound to them. Past attempts to employ the MRR method were less precise, often relying on basic imaging.
The study underscores not only the MRR method’s efficacy but also details its potential application to forthcoming data from renowned telescopes such as the Subaru Telescope, Dark Energy Survey, Dark Energy Spectroscopic Instrument, Euclid Telescope, eROSITA Telescope, and the James Webb Space Telescope.
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