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HR 8799 System

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Exoplanetary Scratchpad

[SysBP Img]

Hot young star system 300 ly away which is the only imaged and wide multiplanetary system. The 30 MY old star is the only known Gamma Doradus variable that is also a Vega-like star. The innermost is e (14.5 AU, 10 MJ), followed by d (24 AU, 10 MJ), c (38 AU, 10 MJ), and b (68 AU, 7 MJ). Inside the inner planet's orbit is an asteroid belt, while outside of the outer planet is a cometary belt (including a clump at 1:2 resonance with the outermost planet), while further yet is a huge halo extending to 2000 AU. The outer three are planets are 2-2.5 times as far as Saturn, Uranus, and Neptune are respectively, but receive similar radiation. The large planets would likely pull the system apart, leading scientists to believe the inner three planets are probably locked in a 1:2:4 orbital resonance in order to maintain stability. An inner planet is at Saturn-to-Uranus-like distances and challenges planetary formation models. Fomalhaut is the only other system where interaction between planets and dust belts can be observed. They are near the upper limits of mass to be classified as planets and could be Brown Dwarves. Upper mass limits are determined by system stability models. All three planets were later found in archived Hubble images. The middle planet became the first to have its spectrum directly measured. The spectrum confused scientists and didn't fit current formation theories. They contain carbon monoxide and are depleted in methane, which suggests they were formed in part by absorbing comets in the system. The outermost planet b has unusually thick dust clouds. There is possibly a fifth undetected planet in an inner resonant orbit.

My ThoughtsEdit

It's neat that this system kind of resembles a scaled up version of our solar system. We have several scaled down analogs, it's nice to see an up-scaled one too. Plus their thermal environments are similar to our own.

I was rather annoyed when they announced results from the LEECH survey, but they didn't really explain any new science results for the system. Maybe just more precise measurements of what they already had? Well, I guess it might have been a proof of concept set of observations.

I wonder where the evidence for this fifth planet that I saw comes from?

Does this system have a Jupiter/Saturn analog pair in it? When thinking about those planets role in the solar system's formation, could planets like Earth have formed? I guess this system's planets are so much more massive that it's hard to know if things would turn out the same way. The asteroid belt/comet belt are similar to our own solar system for one thing, presumably at an earlier age.

HR 8799 System Web PagesEdit

HR 8799 System ArtworkEdit

Template:HR 8799 Gallery

HR 8799 System In the NewsEdit

Three Planets Imaged (2008)Edit

Outermost Planet Found in Hubble Archive Photos (2009)Edit

Asteroid and Kuiper Belt Found (2009)Edit

Link Between Planets and Halo (2009)Edit

Are Planets Brown Dwarves Instead? (2009)Edit

First Direct Planetary Spectrum Obtained (2010)Edit

Extrasolar Visions Thread

Detected With Smaller Ground Telescopes (2010)Edit

Planet b Has Unusually Thick Clouds of Dust (2010)Edit

Mentioned when 500th Planet Discovered (Nov 2010)Edit

Planet d Discovered, Challenges Both Formation Models (Dec 2010)Edit

Clump in Resonance Detected (Apr 2011)Edit

Feature Article on Imaged Planets (2011)Edit

See Imaged Exoplanets for more systems

Outer Two Planets Found in Old Hubble Photos (Oct 2011)Edit

First Chemical Fingerprints Obtained (Mar 2013)Edit

System's Atmospheres Probed in Detail (Mar 2013)Edit

Adaptive Optics Hasten Images (Mar 2015)Edit

Targeted by LEECH Survey (Apr 2015)Edit

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