Measuring cosmic distances is a major challenge thanks to the fact that we live in a relativistic Universe. When astronomers observe distant objects, they are not just looking through space but also back in time. In addition, the cosmos has been expanding ever since it was born in the Big Bang, and that expansion is accelerating. Astronomers typically rely on one of two methods to measure cosmic distances (known as the Cosmic Distance Ladder). On the one hand, astronomers rely on redshift measurements of the Cosmic Microwave Background (CMB) to determine cosmological distances.
Conversely, they will rely on local observations using parallax measurements, variable stars, and supernovae. Unfortunately, there is a discrepancy between redshift measurements of the CMB and local measurements, leading to what is known as the Hubble Tension. To address this, a team of astronomers from several Chinese universities and the University of Cordoba conducted a two-year statistical analysis of one million galaxies. From this, they’ve developed a new technique that relies on Baryon Acoustic Oscillations (BAO) to determine distances with a greater degree of precision.
Astronomers know that galaxies grow over time through mergers with other galaxies. We can see it happening in our galaxy. The Milky Way is slowly absorbing the Large and Small Magellanic Clouds and the Sagittarius Dwarf Spheroidal Galaxy.
For the first time, astronomers have found evidence of an ancient mass migration of stars into another galaxy. They spotted over 7,000 stars in Andromeda (M31), our nearest neighbour, that merged into the galaxy about two billion years ago.
Back in 2015, construction began on a new telescope called the Dark Energy Spectroscopic Instrument (DESI). Later this year, it will begin its five-year mission. Its goal? To create a 3D map of the Universe with unprecedented detail, showing the distribution of matter.
That detailed map will allow astronomers to investigate important aspects of cosmology, including dark energy and its role in the expansion of the Universe.
Since the 1990s, scientists have been aware that for the past several billion years, the Universe has been expanding at an accelerated rate. They have further hypothesized that some form of invisible energy must be responsible for this, one which makes up 68.3% of the mass-energy of the observable Universe. While there is no direct evidence that this “Dark Energy” exists, plenty of indirect evidence has been obtained by observing the large-scale mass density of the Universe and the rate at which is expanding.
But in the coming years, scientists hope to develop technologies and methods that will allow them to see exactly how Dark Energy has influenced the development of the Universe. One such effort comes from the U.S. Department of Energy’s Lawrence Berkeley National Lab, where scientists are working to develop an instrument that will create a comprehensive 3D map of a third of the Universe so that its growth history can be tracked.