NGC 90
Interacting grand-design spiral galaxy in Andromeda.
NGC 90 is a grand-design spiral galaxy located approximately 333 million light-years away in the constellation Andromeda. It is notable for its ongoing interaction with the neighboring spiral galaxy NGC 93, together forming the interacting galaxy pair Arp 65 in the Atlas of Peculiar Galaxies. The interaction has produced highly elongated and distorted spiral arms, bright blue star clusters indicative of star formation, and features similar to those of jellyfish galaxies, including tidal tails and escaping clouds of gas.
Quick Facts
- Epoch
- J2000
- Constellation Name
- Andromeda
- Ra
- 00 · 21 · 51.4
- Dec
- +22 · 24 · 00
- Z
- 0.017856
- H Radial V
- 5353 ± 10 km/s
- Dist Ly
- 333.8 ± 146 Mly / (102.35 ± 44.76 Mpc)
- Appmag V
- 13.7
- Notes
- Interaction with NGC 93, tidal tails and large H I cloud
- Names
- UGC 208, MCG+04-02-011, PGC 1405, Arp 65
- Mass
- ~4.9 × 10^10 M⊙
Facts from the source article.
Lore & Background
NGC 90 was discovered by R. J. Mitchell in 1854. It is a grand-design spiral galaxy whose two spiral arms have become highly elongated and distorted due to an interaction with NGC 93, a spiral galaxy located 64 kiloparsecs away. The interaction, which occurred roughly 100–250 million years ago, displaced a large amount of gas far beyond the main disk, creating two tidal tails: one thin and long aimed toward the northwest, and a smoother, shorter one pointing in the opposite direction. These tails straighten out toward the periphery. Along the western tidal tail and east of the disk, several regions of star formation are visible as bright blue regions, indicating populations of young stars. The central regions of the galaxy are affected by photoionization, creating shocks.
Reader's Guide
NGC 90 is significant as a clear example of galaxy interaction and its effects on structure and star formation. Its distorted spiral arms and tidal tails illustrate the gravitational forces at play during a close encounter with a companion galaxy. The galaxy is also notable for a large H I cloud located southeast of it, with a mass of 6.8 × 10⁹ solar masses—about half the galaxy's total gas content. This cloud is being displaced outward at a velocity of around 340 km/s, fast enough that it is not gravitationally bound to NGC 90. The cloud's motion is likely due to ram pressure stripping as NGC 90 travels through the hot gas of its galaxy group, suggesting NGC 90 may be a potential jellyfish galaxy. The interaction with the more gas-rich companion NGC 93 also contributes to the loss of gas. H I clouds were only marginally detected in the main galaxy, and those detected have an asymmetric morphology. NGC 90 and NGC 93 together form Arp 65, a pair cataloged in the Atlas of Peculiar Galaxies.
Did You Know?
- NGC 90 and NGC 93 form the interacting galaxy pair Arp 65.
- The galaxy has a large H I cloud southeast of it with a mass of 6.8 × 10⁹ solar masses.
- The H I cloud is moving away from NGC 90 at about 340 km/s and is not gravitationally bound.
- The interaction with NGC 93 occurred roughly 100–250 million years ago.
Frequently Asked Questions
What is NGC 90?
NGC 90 is a grand-design spiral galaxy sitting in the constellation Andromeda, roughly 333 million light-years from Earth. It is best known for its ongoing gravitational interaction with the neighboring spiral NGC 93, a pairing cataloged as the Arp 65 system.
What makes NGC 90 visually distinctive?
The mutual tug-of-war with NGC 93 has stretched its spiral arms into long, distorted shapes and triggered bright blue star clusters where new stars are forming. Tidal tails and escaping gas clouds also give the system a look reminiscent of jellyfish galaxies.
How far away is NGC 90 and how hard is it to see?
It sits about 333 million light-years (102 megaparsecs) from us, placing it firmly in the deep-sky regime. With an apparent magnitude of 13.7, even a modest telescope will only reveal a faint smudge under truly dark skies.
Who discovered NGC 90 and when?
R. J. Mitchell first recorded the galaxy in 1854 during the survey work that fed into the New General Catalogue. It was later singled out as a peculiar interacting system and entered the Arp catalogue as part of the Arp 65 pair.
Which constellation does NGC 90 belong to?
It lies within the boundaries of Andromeda, the same constellation that hosts the famous M31. That shared region makes NGC 90 a natural companion target for observers already pointing at that rich stretch of sky.
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