KELT-9b, A Planet Hotter than Some Stars

Discussion in 'Astronomy, Exobiology, & Cosmology' started by danshawen, Jun 6, 2017.

  1. danshawen Valued Senior Member

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    http://www.bbc.com/news/science-environment-40171936

    It takes just two (Earth) days for this tidally locked large planet, three times the mass and twice as big as Jupiter, to complete a polar orbit about the hot, UV emitting blue star more than twice as massive as our Sun, which is so rapidly spinning that it would appear to be flat to our eyes.

    The tidally locked surface on the day side of KELT-9b is over 4,300 degrees Celsius (7800 degrees F), which is hotter than Red Dwarf type stars, and only about 2000 degrees F cooler than our Sun. By means of comparison, the day side of our own planet Mercury is a cool 430 degrees Celsius (800 degrees F). Which is to say, Mercury isn't even luke warm compared to this.

    The planet was identified in 2014 as something of interest by a small robotic "Kilodegree Extremely Little Telescope" facility that uses standard camera telephoto lenses searching for exoplanets, but it has taken this long to confirm the odd behavior and characteristics of this system.
    Stars of this type rapidly burn and expend their nuclear fuel for millions (but not billions) of years, so when the host star begins to expand near the end of its lifecycle, this large exoplanet could provide a large pre-heated, ready-to-eat snack, if the surface of the planet hasn't sublimated and gotten completely blown away by solar wind, that is.
     
    Last edited: Jun 6, 2017
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  3. The God Valued Senior Member

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    So the planet is no longer there.

    Now the point is which substance could sustain 4300 deg C. The temperature of a planet is mainly due to trapping of heat of its star. By what means can it trap so much heat that its temperature gets so high?
     
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  5. Janus58 Valued Senior Member

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    ?? The planet was estimated at a mass of 3 times that of Jupiter, and even using the 10 trillion gram per sec rate of material loss given in the article, in the 650 years it took for the light from it to reach us, it would only lost ~1/30,000,000 of its mass.
     
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  7. The God Valued Senior Member

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    You are fine with your linear maths.

    The bigger question is the origin of this planet, captured? Or through normal planetary disc formation process? And the question still remains unanswered that is how it can acquire 4300 Deg C from its star even during day time? Secondly the disintegration must be faster as it cannot be anything but gaseous lump.

    Or is it excluded that it has no known fusion process of its own? I mean can 3 times Jupiter mass gravity not sufficient to create mini fusion reactor, under any circumstances?

    Are we able to directly capture it's transmitted daytime light? Or it is just inferred from its star rotation like any other exoplanet? What is the process of measuring the temperature of a planet 650 ly away?
     
  8. danshawen Valued Senior Member

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  9. Yazata Valued Senior Member

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    Bring your shades wear plenty of your strongest sunblock.
     
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  10. Yazata Valued Senior Member

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    It sounds like it's effectively a little sub-brown-dwarf star, kind of on the cusp between being a planet and being a star (albeit one too small for fusion reactions to occur).

    https://en.wikipedia.org/wiki/Sub-brown_dwarf

    I'm assuming that this 'planet' is gaseous.

    It's interesting to speculate about what would happen to a tidally locked rocky super-Earth that got that hot. 4,300 degrees F is hot enough to vaporize pretty much any material the planet might be made of. So the planet would be boiling away on the sunward side.

    A gas giant with one side that hot and the other side much cooler must have some ungodly weather. Do winds distribute heat to the cooler side?

    I wonder whether a gas giant would be reduced to plasma and be boiling away on the sunward side too, leaving a ring of gas or energized plasma around the hot blue star. If so, it might be detectible spectrographically. Though our own Sun is a hugely hot ball of plasma, whose gravitation holds it together. Would this 'planet' have enough gravity to hold it together and keep it from evaporating?

    If it ever had a surface. A planet that big would probably be a Jupiter-style gas-ball. I'm not convinced that a solid surface could even exist in that heat, which is why I was speculating about rocky super-Earths.

    I suspect that conditions like these would destroy a planet in a blink of an eye, in astrophysical/geological time. So everything may be kind of speeded-up in this stellar system.
     
    Last edited: Jun 7, 2017
  11. danshawen Valued Senior Member

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    https://en.wikipedia.org/wiki/Hot_Jupiter

    "They are likely to have extreme and exotic atmospheres due to their short periods, relatively long days, and tidal locking. Atmospheric dynamics models predict strong vertical stratification with intense winds and super-rotating equatorial jets driven by radiative forcing and the transfer of heat and momentum.[14][15]"
     

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