Astrophile: Evaporating planet shows how worlds vanish


Object: Evaporating exoplanet
Distance: 1500 light years

1. Preheat star to 2000 kelvin.
2. Take one Mercury-sized rocky world and place in a 16-hour-long orbit.
3. Bake for 10 billion years or until obliterated.

It’s a recipe that won’t win any culinary awards, but when turned into a computer model, it could explain the strange sighting last year of a rapidly disappearing exoplanet around the small sunlike star KIC 12557548. The model hints that this world is now about the size of Earth’s moon and may even be down to its naked iron core, which would make it the smallest known exoplanet. If true, the tiny remnant could help us better understand what’s inside our home world.

Dubbed KIC 12557548b, the planet was discovered using NASA’s Kepler space telescope. Kepler spots exoplanets by looking for the regular dimming of stars caused by orbiting planets that transit them – pass in front of their star – as seen from Earth. The more light is blocked, the larger the planet.

KIC 12557548b is small and so close to its star that its year lasts just 16 hours. But the dimming caused by the planet varies wildly, suggesting it is surrounded by a gigantic, ever-changing cloud of material.

“It basically looks like a comet that’s very erratic, with a long trailing tail of dust,” says Eugene Chiang of the University of California, Berkeley, who was part of a team that found the planet last year. The team thinks the rocky surface is being evaporated away by the intense heat of its star.

Written By: Jacob Aron
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  1. But if the star’s radiation is ‘burning away’ the material, how did the planet form in the first place?

  2. In reply to #2 by hairybreeks:

    But if the star’s radiation is ‘burning away’ the material, how did the planet form in the first place?

    Surely the planet formed further from its sun and its orbit has since decayed?

  3. In reply to #2 by hairybreeks:

    But if the star’s radiation is ‘burning away’ the material, how did the planet form in the first place?

    The gravity of planets interacts with other planets to stabilise them into resonant orbits. This can move the orbits of planets / moons nearer to, or further from, the parent body.

    Planets heat up and volatile materials are “boiled off and atmospheres are swept away by the solar wind.

    Which elements are lost, depends on the temperature and atmospheric pressure. Many gasses have been swept from the planets of the inner Solar System into the outer parts where they (water etc) have frozen solid.

    The planet surface of the planet Mercury, is being boiled away by the Sun (including elements which are rocks on Earth) on its daylight side. Mercury has a a comet-like tail of vapour streaming off it in the Solar Wind, as these vapours are being swept away in its tenuous atmosphere which only exists because of the resupply of gasses from the heated surface.

    Atmosphere of Mercury

    Mercury has a very tenuous and highly variable atmosphere (surface-bound exosphere) containing hydrogen, helium, oxygen, sodium, calcium, potassium and water vapor, with a combined pressure level of about 10−14 bar (1 nPa).[2] The exospheric species originate either from the Solar wind or from the planetary crust. Solar light pushes the atmospheric gases away from the Sun, creating a comet-like tail behind the planet.

    The lighter elements are the first to go.

  4. Its orbit must of changed to cause it to be so close to its sun, otherwise how could its sun of allowed the formation of the exoplanet in the first place?, or else its sun has expanded since the planet formed and is now in the process of evaporating this exoplanet. I love astronomy everytime we discover some thing the discovery is accompanied with new batch of questions.

  5. Something to look forward too. We had better get busy inhabiting other solar systems before Earth begins it’s final decay into oblivion. We only have a window of opportunity to find a new home. Then again, time is subject to relativity.

  6. In reply to #2 by hairybreeks:

    But if the star’s radiation is ‘burning away’ the material, how did the planet form in the first place?

    Besides the other good comments there is also the tendency of stars to become hotter throughout their lifetime. Earth will eventually move outside the habitable zone without changing its orbit because the sun will become hotter. The earth has remained in the habitable zone up till now by gradually locking in most of the CO2 in rocks. If it hadn’t, Earth would have resembled Venus by now.

  7. I recently had a similar experience on the Cambridge ring road, although it felt like more than 16 hours.

  8. I see there is a new discovery of a new smaller exoplanet than earlier discoveries. Once again near to its star where they are hot, but easiest to find.

    Astronomers have smashed the record for the smallest planet beyond our Solar System – finding one only slightly larger than our Moon.

    To spot the tiny, probably rocky planet, they first needed to precisely measure the size of its host star.

    They did so using “astroseismology” – effectively, turning tiny variations in the star’s light into sounds.

    A report in Nature describes the blistering, probably rocky planet, which orbits its star in just 13 days.

    It is joined in this far-flung solar system by two other planets, one three-quarters Earth’s size and one twice as large as Earth – all circling their star too closely to harbour liquid water or life.

    Kepler 37b has a radius not much larger than that of the Moon; Kepler 37d is about twice Earth’s radius . . . . .. Alt Text – (Right click and select “view image”)

    The record for smallest “exoplanet” is routinely being broken, as astronomers get better and better at finding them.

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