Ultra-Faint Dwarf Galaxy Pegasus V

Unusual fossil galaxy discovered on the outskirts of Andromeda – could reveal the history of the universe

The Gemini North telescope reveals a remnant of the earliest galaxies.

A unique ultra faint dwarf galaxy has been discovered at the outer edges of the Andromeda Galaxy thanks to the discerning eyes of an amateur astronomer examining archival data processed by NSF’s NOIRLab’s Community Science and Data Center. The dwarf galaxy – Pegasus V – was found to contain very few heavier elements and is probably a fossil of the first galaxies in follow-up observations by professional astronomers using the International Gemini Observatory, a program of NSF’s NOIRLab.

Using several facilities from NSF’s NOIRLab, an unusual ultra faint dwarf galaxy has been discovered at the edge of the Andromeda Galaxy. The galaxy, called Pegasus V, was first discovered as part of a systematic search for Andromeda dwarfs coordinated by David Martinez-Delgado of the Instituto de Astrofísica de Andalucía, Spain, when amateur astronomer Giuseppe Donatiello discovered a curious “spot” in data in a[{” attribute=””>DESI Legacy Imaging Surveys-afbeelding.” width=”777″ height=”396″ data-ezsrcset=”https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-777×396.jpg 777w,https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-400×204.jpg 400w,https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-768×391.jpg 768w,https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-1536×783.jpg 1536w,https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled.jpg 1992w” sizes=”(max-width: 777px) 100vw, 777px” ezimgfmt=”rs rscb1 src ng ngcb1 srcset” data-ezsrc=”https://scitechdaily.com/images/Ultra-Faint-Dwarf-Galaxy-Pegasus-V-Circled-777×396.jpg”/>

De opname is gemaakt met de door het Amerikaanse Department of Energy vervaardigde Dark Energy Camera op de Víctor M. Blanco 4-metertelescoop van Cerro Tololo Inter-American Observatory (CTIO). De gegevens zijn verwerkt via de Community Pipeline die wordt beheerd door NOIRLab’s Community Science and Data Center (CSDC).

Faint stars in Pegasus V were revealed in deeper follow-up observations by astronomers using the larger, 8.1-meter Gemini North telescope with the GMOS instrument, confirming that it is an ultra faint dwarf galaxy on the edge of the Andromeda Galaxy. Gemini North in Hawaii is half of the International Gemini Observatory.

The Gemini observations showed that the galaxy appears to be extremely deficient in heavier elements compared to similar dwarf galaxies, meaning it is very old and likely a fossil of the first galaxies in the Universe.

“We have found an extremely faint galaxy whose stars formed very early in the history of the Universe,” said Michelle Collins, an astronomer at the University of Surrey, UK, and lead author of the paper announcing the discovery. “This discovery is the first time a galaxy this dim has been found around the Andromeda galaxy using an astronomical survey not specifically designed for the task.”

Ultra-nebulous dwarf galaxy Pegasus V

A unique ultra faint dwarf galaxy has been discovered in the outer edges of the Andromeda Galaxy thanks to the keen eyes of an amateur astronomer who studied archival data from the U.S. Department of Energy-manufactured Dark Energy Camera on the 4-meter Víctor M. Blanco Telescope at Cerro Tololo Inter-American Observatory (CTIO) and processed by the Community Science and Data Center (CSDC). Follow-up by professional astronomers using the International Gemini Observatory revealed that the dwarf galaxy – Pegasus V – contains very few heavier elements and is likely a fossil of the first galaxies. All three facilities involved are programs of NSF’s NOIRLab. Credit: International Gemini Observatory/NOIRLab/NSF/AURA, Recognition: Image Processing: TA Rector (University of Alaska Anchorage/NSF’s NOIRLab), M. Zamani (NSF’s NOIRLab) & D. de Martin (NSF’s NOIRLab)

The faintest galaxies are considered fossils of the very first galaxies to form, and these galactic relics hold clues to the formation of the earliest stars. While astronomers expect the Universe to be teeming with faint galaxies like Pegasus V,[2] they haven’t discovered nearly as many as their theories predict. If there really are fewer faint galaxies than predicted, it would pose a serious problem for astronomers’ understanding of cosmology and dark matter

Discovering examples of these faint galaxies is therefore an important, but also difficult undertaking. Part of the challenge is that these faint galaxies are extremely difficult to see, appearing as just a few thin stars hidden in expansive images of the sky.

“The problem with these extremely faint galaxies is that they have very few of the bright stars we usually use to identify them and measure their distances,” explains Emily Charles, a PhD student at the University of Surrey who was also involved. during the investigation. † “Gemini’s 8.1-meter mirror allowed us to find faint, old stars, allowing us to both measure the distance to Pegasus V and determine that the stellar population is extremely old.”

The strong concentration of ancient stars the team found in Pegasus V suggests the object is likely a fossil of the earliest galaxies. Compared to the other faint galaxies around Andromeda, Pegasus V appears uniquely old and metal-poor, indicating that its star formation did indeed stop very early.

“We hope that further study of the chemical properties of Pegasus V will provide clues about the earliest periods of star formation in the Universe,” Collins concluded. “This small fossil galaxy from the early Universe may help us understand how galaxies form and whether our understanding of dark matter is correct.”

“The publicly accessible Gemini North telescope offers community astronomers a range of possibilities,” said Martin Still, Gemini Program Officer at the National Science Foundation. “In this case, Gemini supported this international team to confirm the presence of the dwarf galaxy, associate it physically with the Andromeda galaxy and determine the metal-deficient character of its evolved stellar population.”

Upcoming astronomical facilities will shed more light on faint galaxies. Pegasus V witnessed a time in the history of the Universe known as reionization, and other objects dating back to this time will soon be observed with NASA’s James Webb Space Telescope† Astronomers hope to discover other such faint galaxies in the future using Vera C. Rubin Observatory, a program from NSF’s NOIRLab. Rubin Observatory will conduct an unprecedented decade-long survey of the optical sky called the Legacy Survey of Space and Time (LSST).


  1. The DESI Legacy Imaging Surveys were conducted to identify targets for the operations of the Dark Energy Spectroscopic Instrument (DESI). These surveys include a unique mix of three projects that have observed a third of the night sky: the Dark Energy Camera Legacy Survey (DECaLS), observed by the DOE-built Dark Energy Camera (DECam) on the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO) in Chile; the Mayall z-band Legacy Survey (MzLS), by the Mosaic3 camera on the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory (KPNO); and the Beijing-Arizona Sky Survey (BASS) by the 90Prime camera on the Bok 2.3-meter telescope, which is owned and operated by the University of Arizona and located at KPNO. CTIO and KPNO are programs of NOIRLab of NSF.
  2. Pegasus V is so named because it is the fifth dwarf galaxy discovered in the constellation Pegasus. The on-sky separation between Pegasus V and the Andromeda Galaxy is about 18.5 degrees.

More information

This research was presented in a paper entitled “Pegasus V – a newly discovered ultra-blurred dwarf galaxy on the outskirts of Andromeda” to appear in Monthly Notices from the Royal Astronomical Society

Reference: “Pegasus V – A Newly Discovered Ultraweak Dwarf Galaxy on the Edge of Andromeda” by Michelle LM Collins, Emily JE Charles, David Martínez-Delgado, Matteo Monelli, Noushin Karim, Giuseppe Donatiello, Erik J. Tollerud and Walter Boschin , Accepted, Monthly Notices from the Royal Astronomical Society

The team consists of Michelle LM Collins (Department of Physics, University of Surrey, UK), Emily JE Charles (Department of Physics, University of Surrey, UK), David Martínez-Delgado (Instituto de Astrofísica de Andalucía, Spain), Matteo Monelli (Instituto de Astrofísica de Canarias (IAC) and Universidad de La Laguna, Spain), Noushin Karim (Department of Physics, University of Surrey, UK), Giuseppe Donatiello (UAI – Unione Astrofili Italiani, Italy), Erik J. Tollerud (Space Telescope Science Institute , USA), Walter Boschin (Instituto de Astrofísica de Canarias (IAC), Universidad de La Laguna and Fundación G. Galilei – INAF (Telescopio Nazionale Galileo), Spain).

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