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Exoplanetary Scratchpad

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The star called 51 Pegasus is now known as Helvetios. Contains the first exo-planet around a normal star discovered and the first "Hot Jupiter" found, which is nicknamed "Bellerophon", and now called Dimidium. Star is about 50 ly located in the square of Pegasus, a G5 star somewhat larger and more massive than the Sun. The planet's discovery was incompatible with planetary system formation models, so they were tweaked to allow for planetary migration. It was also initially thought to be an anomaly or the stripped down core of a brown dwarf. Found to have supersonic winds that caused the eternal night-side hemisphere to be as hot as the day-side one. During its 20th anniversary, this planet became the first one's whose reflected visible light was detected. The technique involved looking at a star's visible spectrum, and then detecting a faint reflection of this spectra. Its actual mass (0.46 MJ) and inclination (9deg) were obtained as a result. The planet seems to have a larger radius and bright surface, rather typical for hot jupiters. One of the first 20 exoplanet systems allowed to be given common names by the IAU. The star's name is Latin for a Celtic tribe that lived in Switzerland (the place where its planet was discovered) during the middle ages. The planet's name is Latin for "half" due to the fact its minimum mass is half as massive as Jupiter's.

My Thoughts[]

I remember reading that usually, star systems with a hot jupiter in them don't tend to contain other planets. As if its migration forced them into the Sun. Well, there have been multiplanet systems with hot jupiters found before, but I wonder if they'll ever find another planet in this system, showing it to be a rather typical system like this.

This system just seems so lonely and I don't feel that enough studying has been done of it. Nice to see it gain some more recognition through this visible reflected light detection proof of concept. Some of these earlier detected planets without transits can now be studied in more detail. Wonder if they'll be able to discover new planets with this technique?

The planet is up to be named soon. I wish it could just be officially recognized as Bellerophon, but I don't think the public naming system in place would allow for that possibility. If I was allowed to vote for a name for a particular planet, I would definitely vote for Bellerophon. This nickname being associated with the constellation is what made me think that all planets should be given names associated with their constellations somehow. The IAU has certain naming conventions for planetary features on a given body. Why can't they come up with similar naming conventions for planets within a constellation, instead of this free-for-all naming system similar to asteroids.


Arg, Bellerophon isn't one of the suggested names.

Jiguang - a legendary chinese horse

51 Pegasi System Web Pages[]

51 Pegasi System In the News[]

Discovered (1995)[]

Supersonic Wind Causes Uniform Temperature (2007)[]

Exoplanet's Reflected Light Detected For First Time (2015)[]

One of the Top 20 Exoplanetary Systems First Up For Naming (May 2015)[]

Fun Links[]

There's a song called 51 Pegasus by Total Eclipse.

See Also[]