Terzan 5

Source: Wikipedia, the free encyclopedia.
Terzan 5
Distance
18.8 ± 1.6 kly[note 1] (5.9 ± 0.5 kpc[4])
Apparent magnitude (V)12.8[1]
Apparent dimensions (V)1′02″ (half-mass diameter)[4]
Physical characteristics
Mass~2×106[4] M☉ (4 × 1036 kg)
Radius2.7 ly[note 2]
VHB22.5[3]
Metallicity = −0.21
12 Gyr[6]
Notable featuresPossibly the core of a disrupted dwarf galaxy
Other designationsTer 5, IRC–20385
See also: Globular cluster, List of globular clusters

Terzan 5 is a heavily obscured

Sagittarius constellation in the direction of the Milky Way's center. Terzan 5 probably follows an unknown complicated orbit around the center of the galaxy, but currently it is moving towards the Sun with a speed of around 90 km/s.[6]

Physical properties

The

bolometric luminosity is about 800,000 times that of the Sun, while its mass is about 2 million solar masses.[4] The small core of Terzan 5—about 0.5 pc in size[4]—has one of the highest star densities in the galaxy. Its volume mass density exceeds 106 M☉/pc3,[10] while its volume luminosity density exceeds 105.5 L☉/pc3, where M☉ and L☉ are the Sun's mass and luminosity, respectively. The cluster also has one of the highest metallicities among the Milky Way's globular clusters—[Fe/H]=−0.21.[5]

In 2009 it was discovered that Terzan 5 consists of at least two generations of stars with ages of 12 and 4.5 billion years and slightly different metallicities, possibly indicating that it is the core of a disrupted dwarf galaxy, not a true globular cluster.[6] There are only a few other globular clusters in the Milky Way that contain stars with different ages. Among them are M54, Omega Centauri and Liller 1. The latter, like Terzan 5, is thought to be a fossil fragment from the assembly of the galactic bulge.[11] The cluster also contains around 1300 core helium burning horizontal branch (HB) stars,[6] including at least one RR Lyrae variable star.[10]

Pulsars and X-ray sources

Terzan 5 is known to contain 49

PSR J1748–2446ad, the fastest known millisecond pulsar, which is spinning at 716 Hz (the rotation period is 1.40 ms).[14]

Terzan 5 also contains an

cataclysmic variables.[16]

The large number of

binaries, including binary systems which contain a neutron star.[16]

In addition to discrete X-ray sources Terzan 5 produces a diffuse non-thermal X-ray emission and high (a few GeV) and ultra-high (0.5–24 TeV) energy

inverse Compton scattering by the relativistic electron emitted by the pulsars off the cosmic microwave background radiation.[13]

Gallery

  • Hubble image of the ancient globular cluster Terzan 5
    Hubble image of the ancient globular cluster Terzan 5
  • Terzan 5 is one of the bulge's primordial building blocks, most likely the relic of the very early days of the Milky Way.[17]
    Terzan 5 is one of the bulge's primordial building blocks, most likely the relic of the very early days of the Milky Way.[17]

Notes

  1. ^ The distance estimates have historically varied from as close as 2.3 kpc[1] to as far as 14.6 kpc.[3] The recent estimates generally range from 5.5 to 8.7 kpc.[4][5]
  2. ^ Based on the half-mass radius of 31″[4] and the known distance of 5.9 kpc. The dense core of the cluster has the radius of 9.0″.[4]

References

  1. ^
    doi:10.1086/111835
    .
  2. ^ a b "Cl Terzan 5". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2009-12-04.
  3. ^
    Bibcode:1996A&A...308..733O
    .
  4. ^
    S2CID 118665166
    .
  5. ^
    S2CID 18360940
    .
  6. ^
    S2CID 35131
    .
  7. ISSN 0037-6604
    .
  8. Bibcode:1968CRASB.267.1245T
    .
  9. Bibcode:1972A&A....19..166K
    .
  10. ^
    S2CID 18698604
    .
  11. S2CID 227054148
    .
  12. ^ "Pulsars in Globular Clusters". www3.mpifr-bonn.mpg.de. Retrieved 2023-12-20.
  13. ^
    S2CID 59036124
    .
  14. S2CID 14945340
    .
  15. doi:10.1086/183581
    .
  16. ^
    S2CID 15975974
    .
  17. ^ "The unusual cluster Terzan 5". www.eso.org. Retrieved 9 September 2016.
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