Peekaboo Galaxy

Peekaboo Galaxy[1]
Observation data (J2000 epoch)
Constellation	Hydra[2]
Right ascension	11^h 31^m 34.6^s[1] 11^h 31^m 35.2^s[3]
Declination	−31° 40′ 28″[1] −31° 40′ 20″[3]
Distance	22.2 ± 2.3 Mly (6.8 ± 0.7 Mpc)[1][3]
Characteristics
Type	Irregular compact blue dwarf galaxy
Apparent size (V)	11 arcsec[1] 1,200 ly (370 pc)[1]
Other designations
HIPASS J1131-31; PGC 5060432

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.^[2] The galaxy is relatively small, at about 1,200 light-years (0.00037 Mpc) across. It is also relatively nearby, at a distance of around 22 million light-years (6.7 Mpc) from Earth.^[1] The Peekaboo Galaxy is considered one of the most metal-poor ("extremely metal-poor" (XMP)), least chemically enriched, and seemingly primordial, galaxies known.^{[1][4][5][6][7][8]}

Discovery

History of observation

The Peekaboo Galaxy was hidden behind a relatively fast-moving foreground star, named TYC 7215-199-1, but during the second half of the 20th century, the star moved aside, clearing the view to the obscured galaxy, which gave the galaxy its name.^[4]

Detailed studies of the galaxy were reported in November 2022, and were based on work using the Hubble Space Telescope.^[4][7] 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.^[6] In the words of Bärbel Koribalski, astronomer at CSIRO in Australia, original discoverer of the galaxy in 2001,^[1][6][8] and coauthor of the 2022 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 (SALT), and others, we know that the Peekaboo Galaxy is one of the most metal-poor galaxies ever detected."^[5]

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 and helium. Later, these very early stars fused their hydrogen and helium into heavier elements, up to, and including, iron. Heavier elements, beyond iron, were later produced as a result of violent supernova explosions, scattering these newly formed heavier elements throughout the Universe, where they would be incorporated into the formation of newer stars.^[8] The detection of the relatively close extremely metal-poor Peekaboo Galaxy may help astronomers better understand the formation of the very earliest stars and galaxies.

Future studies

Karachentsev et al. write that the age of the Peekaboo Galaxy is "decidedly ambiguous".^[6]

Future further studies of the galaxy with the Hubble Space Telescope and the James Webb Space Telescope are being considered.^[2][4]

See also

• Galaxy formation and evolution
• I Zwicky 18
• List of galaxies
• Metallicity distribution function
• Metallicity § Galaxies
• Stellar classification
• Stellar evolution
• Stellar population

References

1. Karachentsev, J.D.; et al. (12 November 2022). "Peekaboo: the extremely metal poor dwarf galaxy HIPASS J1131-31". Monthly Notices of the Royal Astronomical Society. 518 (4): 5893–5903. arXiv:2212.03478. doi:10.1093/mnras/stac3284. Retrieved 18 December 2022.
2. Lea, Robert (7 December 2022). "Peekaboo! Strange tiny galaxy provides a glimpse into the universe's early history - The local 'metal-poor' dwarf galaxy was hidden in the glare of a foreground star earning the nickname Peekaboo". Space.com. Retrieved 18 December 2022.
3. Staff (6 December 2022). ""Peekaboo" Dwarf Galaxy HIPASS J1131–31". Hubble Space Telescope. Retrieved 18 December 2022.
4. "Peekaboo! A Tiny, Hidden Galaxy Provides A Peek Into The Past - Tucked Away In A Local Pocket Of Dark Matter, A Late-Blooming Dwarf Galaxy Looks Like iI Belongs In The Early Universe". NASA. 6 December 2022. Retrieved 18 December 2022.
5. Parks, Jake (16 December 2022). "Hubble spots a nearby galaxy that looks like it belongs in the early universe - The extremely metal-poor galaxy, nicknamed Peekaboo, relatively recently emerged from behind a fast-moving star". Astronomy. Retrieved 18 December 2022.
6. Gough, Evan (7 December 2022). "A Star was Blocking a Galaxy, but Now it's Moved Enough That Astronomers can Finally Examine What it Was Hiding". Universe Today. Retrieved 18 December 2022.
7. Nowakowski, Tomasz (15 December 2022). "'Peekabo' dwarf galaxy is extremely metal-poor, study find". Phys.org. Retrieved 18 December 2022.
8. Starr, Michelle (9 December 2022). "'Peekaboo' Galaxy Emerges From Hiding, And It's A Time Capsule of The Universe". ScienceAlert. Retrieved 18 December 2022.

External links

• Peekaboo Galaxy (video; 2:51) (NASA Space News; 12 December 2022)