The Peekaboo Galaxy (officially known as HIPASS J1131-31 and PGC 5060432) is an irregular compact blue (suggesting hot young stars) dwarf galaxy in the

constellation Hydra Hydra is the largest of the 88 modern constellations, measuring 1303 square degrees, and also the longest at over 100 degrees. Its southern end borders Libra and Centaurus and its northern end borders Cancer. It was included among the 48 conste ...

. The galaxy is relatively small, at about 1,200 light-years (0.37 Mpc) across; and nearby, at a distance of about 22 million light-years (6.8 Mpc) from Earth. The Peekaboo Galaxy is considered one of the most metal-poor ( "extremely metal-poor" (XMP)), least chemically enriched, and seemingly primordial, galaxies known.

Discovery

Discovery of the Peekaboo Galaxy, hiding behind a relatively fast-moving foreground star, named TYC 7215-199-1, became apparent when, in the past 50 to 100 years, the star moved aside, clearing the view to the obscured galaxy. Hence, the related "Peekaboo" naming of the galaxy. Detailed studies of the galaxy were reported in November 2022, and were based on work using the

Hubble Space Telescope The Hubble Space Telescope (often referred to as HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the first space telescope, but it is one of the largest and most versa ...

. The astronomers were able to closely examine about 60 of the individual stars in the galaxy, all appearing relatively young, a few billion years old or younger. In the words of

Bärbel Koribalski Dr. Bärbel Silvia Koribalski is a research scientist working on galaxy formation at CSIRO's Australia Telescope National Facility (ATNF), part of CSIRO's Astronomy & Space Science (CASS). She obtained her PhD at the University of Bonn in Germa ...

, astronomer at

CSIRO The Commonwealth Scientific and Industrial Research Organisation (CSIRO) is an Australian Government The Australian Government, also known as the Commonwealth Government, is the national government of Australia, a federal parliamentar ...

in Australia, original discoverer of the galaxy over 20 years ago in 2001, and coauthor of the recent study of the galaxy, "At first we did not realize how special this little galaxy is ... Now with combined data from the Hubble Space Telescope, the

Southern African Large Telescope The Southern African Large Telescope (SALT) is a 10-metre class optical telescope designed mainly for spectroscopy. It consists of 91 hexagonal mirror segments each with a 1-metre inscribed diameter, resulting in a total hexagonal mirror of 11.1 ...

(SALT), and others, we know that the Peekaboo Galaxy is one of the most metal-poor galaxies ever detected." According to current thinking, early in the formation of the universe, 13.8 billion years ago, the earliest first stars were made, and were mostly composed of

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic, an ...

and

helium Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic table. ...

. Later, these very early stars fused their hydrogen and helium into heavier elements, up to, and including,

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...

. Heavier elements, beyond iron, were later produced as a result of violent

supernova A supernova is a powerful and luminous explosion of a star. It has the plural form supernovae or supernovas, and is abbreviated SN or SNe. This transient astronomical event occurs during the last evolutionary stages of a massive star or when ...

explosions, scattering these newly formed heavier elements throughout the Universe, where they would be incorporated into the formation of newer stars. The detection of the relatively close extremely metal-poor Peekaboo Galaxy ("extreme properties of a young system") may help astronomers better understand the formation of the very earliest stars and galaxies. According to astronomer Gagandeep Anand of the

Space Telescope Science Institute The Space Telescope Science Institute (STScI) is the science operations center for the Hubble Space Telescope (HST), science operations and mission operations center for the James Webb Space Telescope (JWST), and science operations center for th ...

, and coauthor of the recently published studies, "Uncovering the Peekaboo Galaxy is like discovering a direct window into the past, allowing us to study its extreme environment and stars at a level of detail that is inaccessible in the distant, early universe ... Due to Peekaboo’s proximity to us, we can conduct detailed observations, opening up possibilities of seeing an environment resembling the

early universe The chronology of the universe describes the history and future of the universe according to Big Bang cosmology. Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, wit ...

in unprecedented detail.”

Future studies

The astronomers also posed a concern that may have to await further studies of the Peekaboo Galaxy for clarification: “The situation with Peekaboo is decidedly ambiguous ... How can it have such low

metallicity In astronomy, metallicity is the abundance of elements present in an object that are heavier than hydrogen and helium. Most of the normal physical matter in the Universe is either hydrogen or helium, and astronomers use the word ''"metals"'' as a ...

when 13 billion years have passed in the

Local Universe The universe is all of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy. The Big Bang theory is the prevailing cosmological description of the development of the universe. Acco ...

?" Future further studies of the galaxy with the

and the James Webb Space Telescope are being considered.

References

External links

Peekaboo Galaxy (video; 2:51)
(NASA Space News; 12 December 2022) {{DEFAULTSORT:Galaxy, Peekaboo ? Dwarf galaxies Local Group Milky Way Subgroup

Discovery

Future studies

See also

References

External links