NGC 5466
Globular cluster in the constellation Boötes
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NGC 5466 is a globular cluster of stars in the constellation Boötes. It was discovered by German-British astronomer William Herschel on May 17, 1784, and catalogued as H VI.9.[8] This large, dim cluster has an apparent visual magnitude of 9.2 and spans an angular size of 9.0′.[4] It is relatively distant from the Sun,[3] about 52 thousand light-years (16.0 kpc) away,[3][9] and 53 thousand light-years (16.3 kpc) from the Galactic Center.[10]
| NGC 5466 | |
|---|---|
NGC 5466 by Hubble Space Telescope; 3.5′ view | |
| Observation data (J2000 epoch) | |
| Class | XII[1] |
| Constellation | Boötes |
| Right ascension | 14h 05m 27.29s[2] |
| Declination | +28° 32′ 04.0″[2] |
| Distance | 52.2 ± 1.3 kly (16.0 ± 0.4 kpc)[3] |
| Apparent magnitude (V) | 9.2[4] |
| Apparent dimensions (V) | 9.0′[4] |
| Physical characteristics | |
| Absolute magnitude | −6.98[3] |
| Mass | 1.79×105[5] M☉ |
| Tidal radius | 238.0 ly (72.98 pc)[3] |
| VHB | 16.47 |
| Metallicity | [Fe/H] = –1.95±0.02[6] dex |
| Estimated age | 12.15±0.11 Gyr[6] |
| Notable features | Tidal stream |
| Other designations | NGC 5466, C 1403+287, GCl 27, GC 3776, h 1746, H 6[7] |
Observations
The Shapley–Sawyer Concentration Class of NGC 5466 is XII.[1] This is a loose cluster with an unusually low central density compared to other globulars with similar luminosity.[11] It is located at a high galactic latitude and thus displays negligible reddening from interstellar dust.[11] The cluster has a core radius of 1.43′±0.10′ and a half-light radius of 2.3′±0.07′. The King tidal radius is 238.0 ly (72.98 pc).[3]
Observation of the distribution of stars in the cluster shows the impact of mass segregation, with heavier objects sinking toward the center. This is a dynamically young cluster that is just starting to evolve.[12] An isochrone fit to the cluster yields an age estimate of 12.15±0.11 billion years.[6] Other age estimates range from 12.2±0.9 to 13.57 Gyr, depending on the method.[9][13] It has an extremely low metallicity.[6]
In 2006, a long tidal stream was detected stretching from this cluster,[14] perhaps reaching as far as 45° to 60° across the sky.[15][16] It has a combined mass estimated as 4.0×103 M☉.[3] The width dispersion of the stream is 1.31°±0.24°, corresponding to a physical width of 1,200 ± 220 ly (367 ± 67 pc) at the distance of the cluster.[3] The presence of a tidal tail suggests the cluster has been strongly disrupted due to gravitational interactions with the Milky Way galaxy.[11] At some point, this stream may have been tidally disrupted by the Large Magellanic Cloud.[16]
A total of 97 blue straggler stars have been identified in this cluster, which show a mild central peak in distribution.[17] In 2019, it was reported that a candidate hot white dwarf had been discovered orbiting a blue straggler star in the outskirts of NGC 5466. This was the second such pair discovered in a globular cluster.[18] Three short period eclipsing binaries have been found along with six SX Phoenicis variables.[19][20] This was the first globular where a blue straggler eclipsing variable was found.[12] The cluster is host to the brightest-known anomalous Cepheid variable, designated V19.[21][22]
Gallery
The location of NGC 5466 (circled in red)
NGC 5466 imaged with a 32-inch telescope
