HR 8799 e
Extrasolar planet List of extrasolar planets
Parent star

<tr> <td colspan="2">Star</td> <td>HR 8799</td></tr><tr> <td colspan="2">Constellation</td> <td>Pegasus</td></tr><tr> <td>Right ascension</td> <td style="text-align: center">(α)</td> <td>23h 07m 28.7150s[1]</td></tr><tr> <td>Declination</td> <td style="text-align: center">(δ)</td> <td>+21° 08′ 03.302″[1]</td></tr><tr> <td>Apparent magnitude</td> <td style="text-align: center">(mV)</td> <td>5.964[1]</td></tr><tr><td colspan="2">Distance</td><td>129 ± 4[2][note 1] ly
(39 ± 1[2][note 1] pc)</td></tr><tr><td colspan="2">Spectral type</td> <td>kA5 hF0 mA5 V; λ Boo[3][4]</td></tr> <tr style="background-color: #A0B0FF;"><td colspan="3" align=center>Observed separation</td></tr><tr> <td>Angular separation</td> <td style="text-align: center">(ρ)</td> <td>368 ± 9[5] mas</td></tr><tr> <td>Projected separation</td> <td style="text-align: center">(d)</td> <td>14.5 ± 0.5, 14.8 ± 0.5 [5][6] AU</td></tr>

Orbital elements

<tr><td>Semimajor axis</td><td style="text-align: center">(a)</td> <td>~ 14.5 ± 0.5[5][note 2] AU
(~ 2175 Gm)</td></tr><tr><td>Orbital period</td><td style="text-align: center">(P)</td> <td>~ 50[5][note 2] y</td></tr>

Physical characteristics

<tr><td>Mass</td><td style="text-align: center">(m)</td><td>7-9 [6] MJ</td></tr><tr><td>Radius</td><td style="text-align: center">(r)</td><td>1.2 Template:Jupiter radius</td></tr><tr> <td>Temperature</td> <td style="text-align: center">(T)</td> <td>1,000 [7] K</td></tr>

Discovery information

<tr> <td colspan="2">Discovery date</td> <td>November 1, 2010 (announced)
November 22, 2010 (published)</td></tr><tr> <td colspan="2">Discoverer(s)</td> <td>Marois et al.</td></tr><tr> <td colspan="2">Discovery method</td> <td>Direct imaging</td></tr><tr> <td colspan="2">Discovery site</td> <td>Keck and Gemini
in Hawaii</td></tr><tr> <td colspan="2">Discovery status</td> <td>Published[5]</td></tr>

Other designations
HD 218396 e[8]

<tr style="background-color: #A0B0FF;"><td align=center colspan=3>Database references</td></tr><tr valign=baseline><td colspan=2>Extrasolar Planets
</td><td>data</td></tr><tr><td colspan=2>SIMBAD</td><td>data</td></tr>

HR 8799 e is a large exoplanet, orbiting the star HR 8799, which lies 128 lightyears from Earth. This gas giant is between 5 and 10 times the mass of Jupiter,[5] the largest planet in our solar system. Due to their young age and high temperature all four discovered planets in the HR 8799 system are large, compared to all gas giants in the Solar System.


HR 8799 e is the fourth planet orbiting HR 8799 in order of discovery. It is a young, hot and massive gas giant, and is fairly close to its star, lying just between the orbits of Saturn and Uranus in our solar system. The planet is still glowing red hot.[5]

HR 8799 e is the innermost known planet as it orbits closer to its star than the other three known planets in this planetary system. This planet orbits at an estimated distance of 14.5 AU based on the relationship between angular separation measured by direct imaging observations and the star's distance from Earth. The estimated period of this planet if the orbit is face-on is about 50 years.[5]


A team of researchers lead by Christian Marois at the National Research Council's Herzberg Institute of Astrophysics identified the planet from data taken in 2009 and 2010 using the W.M. Keck Observatory in the K and L spectral bands.[5] They announced their findings on November 22, 2010. A separate work reporting the detection of HR 8799 e, led by Thayne Currie and using the Very Large Telescope, was made public six weeks later.[6] Observations obtained since then with the Large Binocular Telescope show that HR 8799 e has a spectrum and temperature similar to HR 8799 c and d.[7]


Near infrared spectroscopy from 995 to 1769 nanometers made with the Palomar Obervatory show evidence of Methane and Acetylene but no Ammonia or Carbon Dioxide. There is currently no explanation why this planet shows strong methane absorption, but the other 3 planets in this system do not, despite all 4 planets having similar atmospheric temperatures.[9]


  1. 1.0 1.1 Computed from parallax: \scriptstyle \mathrm{distance\ in\ parsecs}=\frac{1000}{\mathrm{parallax\ in\ milliarcseconds}}
  2. 2.0 2.1 Value given assuming the planet's orbit is circular and is being observed face-on.


  1. 1.0 1.1 1.2 V* V342 Peg -- Variable Star of gamma Dor type, entry, SIMBAD. Accessed on line November 14, 2008.
  2. 2.0 2.1 van Leeuwen, F. (2007). HIP 114189. Hipparcos, the New Reduction. Retrieved 2008-10-13.
  3. Gray, R.O. and Kaye, A.B. (1999). HR 8799: A Link between γ Doradus Variables and λ Bootis Stars. The Astronomical Journal 118 (6): 2993–2996.
  4. Kaye, A.B. et al. (1999). Gamma Doradus Stars: Defining a New Class of Pulsating Variables. PASP 111 (761): 840–844.
  5. 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 Template:Cite doi
  6. 6.0 6.1 6.2 Currie, Thayne (March 2011). A Combined Subaru/VLT/MMT 1--5 Micron Study of Planets Orbiting HR 8799: Implications for Atmospheric Properties, Masses, and Formation. ApJ 729 (2): 128.
  7. 7.0 7.1 Skemer, Andrew (July 2012). First Light LBT AO Images of HR 8799 bcde at 1.6 and 3.3 μm: New Discrepancies between Young Planets and Old Brown Dwarfs. ApJ 753 (1): 14.
  8. HD 218396e – Extra-solar Planet Candidate, entry, SIMBAD. Accessed on line December 11, 2010.
  9. Reconnaissance of the HR 8799 Exosolar System I: Near IR Spectroscopy. Cornell University. Retrieved 12 March 2013.

External linksEdit

Template:HR 8799 Coordinates: Sky map 23h 07m 28.7150s, +21° 08′ 03.302″

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