HD 189733
From Wikipedia, the free encyclopedia
| Observation data Equinox J2000.0 |
|
|---|---|
| Constellation | Vulpecula |
| Right ascension | 20h 00m 43.7133s |
| Declination | +22° 42′ 39.070″ |
| Apparent magnitude (V) | 7.67 |
| Absolute magnitude (V) | 6.25 |
| Distance | 62.9 ly (19.3 pc) |
| Spectral type | K1-K2 (Hip. lists G5) |
| Other designations | |
|
GJ 4130, HIP 98505
|
|
HD 189733 (HD 189733 A) is a yellow dwarf star about 63 light-years away in the constellation Vulpecula, and host to at least one extrasolar planet. Given that this star has the same visual magnitude as HD 209458, it promises much for the study of close transiting extrasolar planets. The star can be found with binoculars 0.3 degrees east of the Dumbbell Nebula (M27).
Contents |
[edit] Planet
[edit] HD 189733 Ab
| Orbital elements | ||
|---|---|---|
| Semi-major axis a: | 0.0313 ± 0.0004 AU | |
| Eccentricity e: | 0.00 | |
| Orbital period P: | 2.219 d | |
| Inclination i: | 85.3° ± 0.1° | |
| Longitude of periastron ω: |
° | |
| Time of periastron τ: | JD | |
| Physical characteristics | ||
| Mass: | 1.15 ± 0.04 MJ | |
| Radius: | 1.26 ± 0.03 RJ | |
| Density: | 0.75 ± 0.08 kg/m³ | |
| Temperature: | 1117 ± 42 K | |
| Discovery | ||
| Discovery date: | 2005 | |
| Detection method(s): | ||
| Discoverer(s): | Mayor et al. | |
HD 189733 Ab is an extrasolar gas giant discovered in 2005. This planet exhibits the largest photometric transit depth of any so far observed, of approximately 3%, and clearly exhibits the Rossiter-McLaughlin effect. It also has a very large semi-amplitude (K) of 205 m s⁻¹, as one would expect for such a close hot Jupiter. It was one of the first two planets to be directly spectroscopically observed, along with HD 209458 b.
In 2006, a team led by Drake Deming announced a detection of strong infrared thermal emission from the transiting extrasolar planet HD 189733 b, by measuring the flux decrement during its prominent secondary eclipse.
- "A 6-hour photometric sequence using Spitzer's infrared spectrograph in peak-up imaging mode at 16 [micrometers] shows the secondary eclipse depth to be 0.551 ± 0.030%, with accuracy limited by instrumental baseline uncertainties, but with 32-sigma precision (0.017%) on the detection. The 16-[micrometer] brightness temperature of this planet (1117 ± 42 K) is very similar to the Spitzer detections of TrES-1 and HD 209458 b, but the observed planetary flux (660 [micro-janskies]) is an order of magnitude greater. This large signal will allow a detailed characterization of this planet in the infrared. The photometry has sufficient signal-to-noise (~400 per point) to motivate a search for structure in the ingress/egress portions of the eclipse curve, caused by putative thermal structure on the disk of the planet. We show that by binning our 6-second sampling down to 6-minute resolution, we detect the modulation in the intensity derivative during ingress/egress due to the overall shape of the planet, but our sensitivity is not yet sufficient to distinguish between realistic models of the temperature distribution across the planet's disk. We point out the potential for extending Spitzer secondary eclipse detections down to the regime of transiting hot Neptunes, if such systems are discovered among nearby lower dwarf stars."
[edit] Direct spectral observation
On February 21, 2007, NASA released news that HD 189733 b and HD 209458 b had been directly spectroscopically observed, using the Spitzer Space Telescope. [1] The release came simultaneously with the public release of a new issue of Nature containing the first publication on the spectroscopic observation of the other star, HD 209458 b. The findings on HD 189733 b will appear in an upcoming issue of the Astrophysical Journal Letters. The spectroscopic observations of HD 189733 b were led by Carl Grillmair NASA's Spitzer Science Center.
[edit] HD 189733 B
| Observation data Equinox J2000.0 |
|
|---|---|
| Constellation | Vulpecula |
| Right ascension | 20h 00m 43.7133s |
| Declination | +22° 42′ 39.070″ |
| Apparent magnitude (V) | unknown |
| Distance | 62.9 ly (19.3 pc) |
| Spectral type | M? |
| Other designations | |
|
2MASS J20004297+2242342
|
|
HD 189733 B is a stellar companion of HD 189733 A. At about 216 AU from its primary, this M-dwarf orbits star A every 3,200 years.
[edit] References
- Bouchy et al. (2005). "ELODIE metallicity-biased search for transiting Hot Jupiters II. A very hot Jupiter transiting the bright K star HD 189733". Astronomy and Astrophysics 444: L15-L19. (Preprint)
