A few technical notes on an exoplanet—HR 8799c


Exoplanet HR 8799c
Constellation Pegasus

Right ascension 23h 07m 28.7150s
Declination +21degrees 08minutes 03.302seconds
Apparent magnitude 5.964

Determination of an exoplanet’s atmosphere is just one way to determine whether an exoplanet may harbor life.  One major stumbling block for life determination is the distance to the exoplanet. (Bearing in mind that a spectral image of an exoplanet’s atmosphere is the desired result–then the task seems nearly impossible.)  An exoplanet that is only 130 light years away from our Sun may take multiple lifetimes to reach given current technological advances. However, the advances of science in the far future hinge upon current levels of ignorance being turned away. As the current technology stands, we can (at best) attain spectral images of the largest of exoplanets, or Jupiter-sized exoplanets. One current case in point is the study of HR 8799c.

Fig. 1 via Wikipedia  (Source URL: http://en.wikipedia.org/wiki/HR_8799 ) This image shows the light from three planets orbiting a star 130 light-years away. The planet’s star, named HR8799, is located at the spot marked with an "X." This picture was taken using a small, 1.5-meter (4.9-foot) portion of the Palomar Observatory's Hale Telescope, near San Diego, Calif. This is the first time a picture of planets beyond our solar system has been captured using a telescope with a modest-sized mirror -- previous images were taken using larger telescopes. The three planets, called HR8799b, c and d, are thought to be gas giants like Jupiter, but more massive. They orbit their host star at roughly 24, 38 and 68 times the distance between our Earth and sun, respectively (Jupiter resides at about 5 times the Earth-sun distance). Source: http://www.nasa.gov/topics/universe/features/exoplanet20100414-a.html AuthorNASA/JPL-Caltech/Palomar Observatory

Fig. 1 via Wikipedia (Source URL: http://en.wikipedia.org/wiki/HR_8799 )
This image shows the light from three planets orbiting a star 130 light-years away. The planet’s star, named HR8799, is located at the spot marked with an “X.”
This picture was taken using a small, 1.5-meter (4.9-foot) portion of the Palomar Observatory’s Hale Telescope.
Source: http://www.nasa.gov/topics/universe/features/exoplanet20100414-a.html
Author NASA/JPL-Caltech/Palomar Observatory

This exoplanet system has a sun that is approximately 60 million years old and possesses 4 Jovian-sized planets, as well. The Jovian planets are said to be approximately 20-40 AU from their sun. The young sun may be similar to our Sun–and we have a front-row seat to witness the evolution of a solar system similar to our own.

 Fig. 2 via Wikipedia (Source URL: http://en.wikipedia.org/wiki/HR_8799_c ) Jupiter as compared to HR 8799c

Fig. 2 via Wikipedia (Source URL: http://en.wikipedia.org/wiki/HR_8799_c )
Jupiter as compared to HR 8799c

What of HR 8799c?

HR 8799 is located in the constellation Pegasus. The mass of HR 8799 is approximately 1 1/2 times the mass of the Sun. The exoplanet HR 8799c was discovered through telescopic imaging. The apparent magnitude of the exo-solar system is 5.96–so it may be imaged with an Earth-based scope.  The exoplanet HR 8799c takes about 190 (earth) years to orbit its sun.

Intensive studies of the system:

Recent research reports from the journal Science indicate that the exoplanet HR 8799c has atmospheric water and carbon monoxide, as well. Given the distance of the HR 8799 system from Earth—I wondered how the evidence for carbon monoxide and water was obtained. The evidence for the atmospheric constituents came from “ground-based studies” by the Keck II telescope in Hawaii. The team of workers performed and found the following for HR 8799c.

  • Obtained Infrared spectra of the HR 8799c  using 10-meter Keck II scope over a period of 2 years (33 exposures were obtained for 5.5 hours total)
  • Images of HR 8799c were processed by removing scattered, stray light
  • Once noise all noise was removed—a full, low resolution infrared spectrum was obtained
  • No methane signatures were identified—methane is generally exhibits a strong spectral signature
  • An effective exoplanetary temperature of approximately 1100 K (900 degrees Celsius or 1600 degrees Fahrenheit)
  • The mass of HR 8799c is estimated to be at least greater 10 times than Jupiter’s

Of course, studies of Jovian-sized planets are of interest to Astronomers because we can begin to draw a systematic study of planets. When astronomers draw-up systematic studies and reduce data, then patterns become clear. Perhaps, we may (one day) possess the ability to give all exo-solar systems and their “birth environments” a kind-of “periodic-table-characterization” (if you can pardon my expression).   The notion may seem far-fetched to experimentalists, but it may put comparative planetology in a realm that may make it conducive to informal studies and high school age students, as well.

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References and Notation—

NASA's Spitzer Space Telescope captured this infrared image of a giant halo of very fine dust around the young star HR 8799, located 129 light-years away in the constellation Pegasus.

Via Wikipedia— Source URL http://en.wikipedia.org/wiki/File:HR_8799_Debris_Disk.jpg

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For a superior description of prior work related to the Science article see the Blog from Scientific American–First Reconnaissance Of An Exoplanetary System

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Citation of Science article—Konopacky, Barman, Macintosh, and Marois, Detection of Carbon Monoxide and Water Absorption Lines in an Exoplanet Atmosphere Published Online March 14 2013
Science 22 March 2013:
Vol. 339 no. 6126 pp. 1398-1401
DOI: 10.1126/science.1232003

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