2023-06-15 13:45:46
The universe is big, and it is getting bigger all the time, since it is expanding. Furthermore, that expansion is accelerating. The cause of that acceleration is unknown. The mysterious force that causes it is called “dark energy.” In order to trace dark energy as far as possible, scientists are using an instrument called DESI (Dark Energy Spectroscopic Instrument) to map more than 40 million galaxies, quasars, and stars.
Now, the DESI team of scientists has publicly presented its first batch of data, with almost 2 million observed astronomical objects.
The 80 terabyte data set comes from 2,480 exposures taken over six months during the validation phase of the experiment.
The fact that DESI works so well, and that the amount of science-grade data it collected during survey validation is comparable to previous completed sky surveys, is a monumental achievement, as Nathalie Palanque-Delabrouille underscores, of the Lawrence Berkeley National Laboratory (Berkeley Lab) under the US Department of Energy, and a member of the DESI team.
DESI uses 5,000 robotic positioners to move optical fibers that collect light from objects millions or billions of light-years away. It is the most powerful multi-object spectrograph in the world, capable of measuring the light of more than 100,000 galaxies in a single night. That light tells researchers how far away an object is, building a 3D cosmic map.
In one of the series of test observations, the DESI team took detailed images in 20 different directions of the sky, creating a three-dimensional map of 700,000 astronomical objects and covering about 1 percent of the total volume that DESI will survey. With the instrument and work plan successfully tested, DESI’s main survey now begins to fill in the gaps between those observations. (Image: David Kirkby/DESI collaboration)
As the universe expands, the wavelength of the emitted light increases, making it redder, a feature known as redshift. The further away a galaxy is, the greater the redshift of the light that reaches us from it. DESI collects redshifts that can then be used to track the action of dark energy and try to gain clues about its nature. (Fountain: NCYT de Amazings)
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