Jenuambro @jenuambro - Twitter Profile

27 days ago

The DESI Legacy Imaging Surveys have released their eleventh public data set, DR11, producing the largest two-dimensional color map of the Universe yet assembled. Built from more than 263,000 telescope exposures, the map contains about 5.6 trillion pixels and nearly four billion detected celestial sources, mainly galaxies and stars. It combines observations from several major ground-based surveys, including data obtained with the Dark Energy Camera on the Blanco 4-meter telescope in Chile and telescopes at Kitt Peak in Arizona, together with infrared measurements from NASA’s WISE and NEOWISE missions. The result is an enormous visible and infrared portrait of the extragalactic sky that can be explored publicly and used as a reference data set by professional astronomers. The importance of this map goes beyond its sheer size. The Legacy Surveys were originally designed to provide the imaging needed to select targets for the Dark Energy Spectroscopic Instrument, or DESI. Imaging tells astronomers where an object appears on the sky and how bright it is in different wavelength bands, but it generally doesn’t provide an accurate distance. DESI adds that missing dimension by measuring spectra and determining redshifts. Combining angular position with distance transforms the essentially two-dimensional imaging survey into a three-dimensional reconstruction of the large-scale structure of the Universe, revealing the distribution of galaxies across billions of years of cosmic history. DESI completed its originally planned five-year observing program ahead of schedule in April 2026. By then it had measured more than 47 million galaxies and quasars and about 20 million Milky Way stars, substantially exceeding its original goals. DESI will nevertheless continue observing through 2028, expanding its footprint from about 14,000 to 17,000 square degrees and aiming for roughly 63 million extragalactic redshifts. The complete five-year cosmological analysis is expected in 2027. One of DESI’s central goals is to reconstruct how cosmic expansion has changed over time and determine whether dark energy behaves like Einstein’s cosmological constant or evolves. Measurements from DESI’s first three years have produced intriguing evidence favoring models in which dark energy changes with cosmic time when DESI data are combined with other cosmological observations. However, this shouldn’t yet be interpreted as a discovery that dark energy is definitely “weakening.” In fact, the latest July 2026 analysis of the Lyman-alpha forest produced measurements closer to the standard ΛCDM model, suggesting that the apparent preference for evolving dark energy could diminish as the data improve, or that a more complicated model may eventually be required. The enormous imaging database also has scientific value independent of DESI’s cosmological mission. Researchers can use it to search for gravitational lenses, unusual galaxies and other rare objects, compare observations of transient phenomena with deep reference images, investigate aspects of dark matter and galaxy evolution, and develop machine-learning techniques capable of handling the increasingly large astronomical data sets expected from facilities such as the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope. What I find particularly significant is that the headline number, nearly four billion objects, is actually secondary to the role this data set plays as an astronomical reference frame. A map this deep and homogeneous becomes infrastructure: researchers studying completely different phenomena can start from the same calibrated view of the sky. And in cosmology, the combination of this huge 2D imaging survey with DESI spectroscopy is what makes the project especially powerful, because it converts an extraordinary photograph of the Universe into a measurement of how cosmic structure has evolved with time.

ExploreCosmos_'s tweet photo. The DESI Legacy Imaging Surveys have released their eleventh public data set, DR11, producing the largest two-dimensional color map of the Universe yet assembled. Built from more than 263,000 telescope exposures, the map contains about 5.6 trillion pixels and nearly four billion detected celestial sources, mainly galaxies and stars. It combines observations from several major ground-based surveys, including data obtained with the Dark Energy Camera on the Blanco 4-meter telescope in Chile and telescopes at Kitt Peak in Arizona, together with infrared measurements from NASA’s WISE and NEOWISE missions. The result is an enormous visible and infrared portrait of the extragalactic sky that can be explored publicly and used as a reference data set by professional astronomers.

The importance of this map goes beyond its sheer size. The Legacy Surveys were originally designed to provide the imaging needed to select targets for the Dark Energy Spectroscopic Instrument, or DESI. Imaging tells astronomers where an object appears on the sky and how bright it is in different wavelength bands, but it generally doesn’t provide an accurate distance. DESI adds that missing dimension by measuring spectra and determining redshifts. Combining angular position with distance transforms the essentially two-dimensional imaging survey into a three-dimensional reconstruction of the large-scale structure of the Universe, revealing the distribution of galaxies across billions of years of cosmic history.

DESI completed its originally planned five-year observing program ahead of schedule in April 2026. By then it had measured more than 47 million galaxies and quasars and about 20 million Milky Way stars, substantially exceeding its original goals. DESI will nevertheless continue observing through 2028, expanding its footprint from about 14,000 to 17,000 square degrees and aiming for roughly 63 million extragalactic redshifts. The complete five-year cosmological analysis is expected in 2027.

One of DESI’s central goals is to reconstruct how cosmic expansion has changed over time and determine whether dark energy behaves like Einstein’s cosmological constant or evolves. Measurements from DESI’s first three years have produced intriguing evidence favoring models in which dark energy changes with cosmic time when DESI data are combined with other cosmological observations. However, this shouldn’t yet be interpreted as a discovery that dark energy is definitely “weakening.” In fact, the latest July 2026 analysis of the Lyman-alpha forest produced measurements closer to the standard ΛCDM model, suggesting that the apparent preference for evolving dark energy could diminish as the data improve, or that a more complicated model may eventually be required.

The enormous imaging database also has scientific value independent of DESI’s cosmological mission. Researchers can use it to search for gravitational lenses, unusual galaxies and other rare objects, compare observations of transient phenomena with deep reference images, investigate aspects of dark matter and galaxy evolution, and develop machine-learning techniques capable of handling the increasingly large astronomical data sets expected from facilities such as the Vera C. Rubin Observatory and the Nancy Grace Roman Space Telescope.

What I find particularly significant is that the headline number, nearly four billion objects, is actually secondary to the role this data set plays as an astronomical reference frame. A map this deep and homogeneous becomes infrastructure: researchers studying completely different phenomena can start from the same calibrated view of the sky. And in cosmology, the combination of this huge 2D imaging survey with DESI spectroscopy is what makes the project especially powerful, because it converts an extraordinary photograph of the Universe into a measurement of how cosmic structure has evolved with time.

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Jenuambro @jenuambro

25 days ago

@ExploreCosmos_ ♥️♥️♥️

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jenuambro retweeted

Lokesh Kanagaraj

@Dir_Lokesh

almost 2 years ago

It all started from here! 💥💥 Grateful to @Karthi_Offl sir, @prabhu_sr sir and the ‘universe’ for making this happen 🤗❤️ Dilli will return soon 🔥 #5YearsOfKaithi