Draco Dwarf
Coordinates: 
17h 20m 12.4s, +57° 54′ 55″
17h 20m 12.4s, +57° 54′ 55″| Draco Dwarf | |
|---|---|
| Apparent magnitude (V) | 10.9[1] |
| Characteristics | |
| Type | E pec[1] |
| Apparent size (V) | 35.5′ × 24.5′[1] |
| Notable features | Highest known dark matter concentrated object |
| Other designations | |
| Draco Dwarf Spheroidal,[1] Draco dSph,[4] UGC 10822,[1] PGC 60095,[1] DDO 208,[1] | |
The Draco Dwarf is a
Palomar Observatory Sky Survey (POSS).[5] It is part of the Local Group and a satellite galaxy of the Milky Way galaxy. The Draco Dwarf is situated in the direction of the Draco Constellation at 34.6°[6] above the galactic plane
.
Characteristics
ellipticity was 0.29 ± 0.04.[6]
Recent studies have indicated that the galaxy may potentially hold large amounts of dark matter.[7] Having an absolute magnitude of -8.6[c] and a total luminosity of only 2×105 L☉, it is one of the faintest companions to our Milky Way.[4]
Draco Dwarf contains many
red giant branch (RGB) stars; five carbon stars have been identified in Draco Dwarf and four likely asymptotic giant branch (AGB) stars have been detected.[4]
The Draco Dwarf is estimated to be 80 ± 10 kpc[2][3] from Earth and span a distance of 830 ± 100 × 570 ± 70 pc.[d]
RR Lyrae
In 1961,
RR Lyrae variables.[8] From this work a RR Lyrae derived distance modulus of 19.55[a] is found which implies a distance of 81 kpc.[b]
Metallicity
The Draco Dwarf contains primarily an
Gaussian distribution with average metallicity of [Fe/H] = −1.74 dex with a standard deviation (sigma/σ) of 0.24 dex and a small tail of metal-rich stars.[4] The central region of Draco Dwarf exhibits a concentration of more metal-rich stars there being more centrally concentrated red horizontal branch stars than blue horizontal branch stars.[4]
Dark matter
Recently, dwarf spheroidal galaxies have become key objects for the study of
isothermal.[7]
At large radii, radial velocity dispersion exhibit strange behavior. One possible explanation for this would be the presence of more than one stellar population. This suggests the need for further study of Draco Dwarf population's metallicity and ages and of dwarf spheroidals in general.[4]
Notes
- ^ Assuming an absolute magnitude of +0.5 V for RR Lyrae the apparent modulus of the Draco Dwarf is 19.58 m - M.[6] Using a reddening value towards Draco Dwarf of 0.03 ± 0.01[4] we get a true distance modulus of 19.55.
- ^ Using the distance modulus formula of 1×10(0.2 * 19.55 + 1) we get an RR Lyrae estimated distance of 81 kpc.
- ^ Apparent Magnitude of 10.9[1] - distance modulus of 19.52 (80 kpc) = −8.6
- ^ distance 80 ± 10 kpc × tan(diameter_angle = 35.5′ × 24.5′[1]) = 830 ± 100 × 570 ± 70 pc diameter
References
- ^ a b c d e f g h i j k l "NASA/IPAC Extragalactic Database". Results for Draco Dwarf. Retrieved 2008-04-08.
- ^ doi:10.1086/382905.
- ^ S2CID 120973010.
- ^ S2CID 55281148
- doi:10.1086/126754
- ^ doi:10.1086/109360
- ^ S2CID 18393976
- doi:10.1086/108431
- S2CID 17088564
- S2CID 18708747
External links
Wikimedia Commons has media related to Draco Dwarf.
- The Draco Dwarf on
| Location | Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each arrow (→) may be read as "within" or "part of". |  | |||||
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