Hot planet

Main article: Rocky Planets (Theoretical Models)

A Vulcanoid type planet is a theoretical model of a planet orbiting close to its parent star. The name is not official and comes from the theoretical planet Vulcan, predicted to orbit the Sun closer then Mercury [1].

The Solar System does not have a Vulcanoid planet, but other stars have, as it's proven by the Kepler Space Telescope.

Relation with parent star Edit

A Vulcanoid should experience surface temperatures between 500 and 1000 C. Below this value, the planet would be a Hermian Type Planet, while above this limit, it would be a Hot Planet, where ground should melt. The Solar Constant for this, should be between 49.5 and 401. Depending on what the host star is, conditions will be very different:

Around M - type stars (modeled for Barnard's Star):

  • Distance: 0.6 to 1.75 million km
  • Visual constant: 2 to 20 (for yellow wavelength)
  • Revolution period: .2 to 1.04 days
  • Stellar gravity: 1500 to 13000
  • Hill sphere (assumed Earth's mass): 10 to 30 thousand km

The planet will rotate very fast around the parent star. There will be huge tidal forces, so that the planet will certainly be tidal locked. Also, the Hill Sphere is close to the surface, meaning that the planet is in risk of tearing apart into a ring system.

Because of the very small distance, the planet will travel through star's flares.

Around K - type stars (modeled after Epsilon Eridani):

  • Distance: 6.5 to 15.5 million km
  • Visual constant: 25 to 220 (for yellow wavelength)
  • Revolution period: 3.6 to 13 days
  • Stellar gravity: 55 to 440
  • Hill sphere (assumed Earth's mass): 60 to 200 thousand km

The planet will experience strong tidal forces and will be tidal locked. The small Hill sphere means satellites are not safe in orbit. The year will be very short.

Around G - type stars (modeled after Sol):

  • Distance: 10.5 to 30 million km
  • Visual constant: 50 to 401 (equal with solar constant)
  • Revolution period: 6.7 to 9.4 days
  • Stellar gravity: 25 to 200
  • Hill sphere (assumed Earth's mass): 0.1 to 0.3 million km

The planet should be tidal locked. Still, there is a small chance of existing satellites.

Around F - type stars (modeled after Procyon):

  • Distance: 30 to 90 million km
  • Visual constant: 25 to 240 (for yellow wavelength)
  • Revolution period: 27 to 139 days
  • Stellar gravity: 4 to 37
  • Hill sphere (assumed Earth's mass): 0.2 to 0.7 million km

The stellar gravity is weaker, so a planet might not be tidal locked. If this is the case, it will rotate slow, at more then 10 days once.

Around A - type stars (modeled after Sirius):

  • Distance: 50 to 150 million km
  • Visual constant: 5 to 57 (for yellow wavelength)
  • Revolution period: 50 to 258 years
  • Stellar gravity: 2 to 18
  • Hill sphere (assumed Earth's mass): 0.4 to 1.2 million km

In these conditions, the planet might not be tidal locked. The year length is significant and the tidal forces are similar to those encountered by Venus. Moons can exist. Days can be shorter and seasons can exist.

Around B - type stars (modeled after Rigel):

  • Distance: 420 to 1200 million km
  • Visual constant: 4 to 32 (for yellow wavelength)
  • Revolution period: 0.98 to 4.7 years
  • Stellar gravity: 0.35 to 3
  • Hill sphere (assumed Earth's mass): 1.5 to 4.2 million km

Compared to the Solar System, the Vulcanoids will orbit between Ceres and Saturn. They will need about one Earth year to complete a rotation and will experience tidal forces similar to Earth. They can host satellites.

Around O - type stars (modeled after R136a1):

  • Distance: 25000 to 75000 million km
  • Visual constant: 0.4 to 3.7 (for yellow wavelength)
  • Revolution period: 122 to 633 years
  • Stellar gravity: 0.01 to 0.001

Hill sphere (assuming Earth's mass): 35 to 110 million km

The planet will be far away from the star. Interesting is the fact that almost all light will be in ultraviolet. The amount of visible light is close to what we see on Venus, Earth or Mars. The amount of red light will be even smaller. It is interesting if such a planet can hold an atmosphere in these conditions.

Brown Dwarfs are too cool to support a Vulcanoid planet outside of the Roche limit.

Physical and chemical composition Edit

At temperatures above 500 C, there is a very small chance to find water. If the planet has no atmosphere and is tidal locked, there should be ice on the dark side. If the planet is not tidal locked but has a small axial tilt, there can be ice at the poles inside craters.

Since the planet is hot, its core will need more time to cool. That means that the nucleus can be hot and liquid and volcanism can exist. Being close to the parent star, the planet will be exposed to strong tidal forces and there is a high chance we would see volcanism.

The surface is exposed to high temperatures and strong solar winds. Because of this, many solids will sublimate, even in tenuous amounts, forming a strange atmosphere, composed of sodium, potassium, maybe also heavy metals and incomings from the solar wind. Over time, this process will change the chemical structure of the planet. Minerals that don't sublimate fast enough will remain on the ground. For mining, a Vulcanoid would be a perfect target.

On the other hand, strong ultraviolet light, together with solar winds, will alter the chemical structure of many rocks. It is possible that in time this will remove oxygen from metal oxides, so there might be amounts of much purer ores then on other planets.

Atmosphere Edit

Before terraforming, the atmosphere would be tenuous, composed of what sublimates from the surface and on what the solar wind brings in.

Atmospheres will be blown away by solar winds. But if we want to terraform these planets, we have to make our own atmospheres. Will they resist?

Simulations show Atmosphere Parameters are interesting around these planets. On an Earth-sized planet, the atmosphere will not be safe, but it will be on Super - Earths. Still, a breathable atmosphere could be maintained around a Mars - sized object for centuries.

Terraforming Edit

It is hard to terraform such a planet. The first step should be to find a way to block the excess heat from the sun. One way is to create a cosmic shield. This can be done with the help of orbiting mirrors or atmospheric mirrors. The first solution has the disadvantage that blocks access for spaceships and after a while the mirrors will form a ring. The second method is also risky, because the mirrors, probably held in place by balloons, will collide and will break. Another idea is to use anti-greenhouse gasses, but as far, not many are known.

Basically, the first step in terraforming is to increase the planet's albedo (to make it reflect as much light and heat as possible). This process also might create a greenhouse effect. Venus has a very high albedo, that in fact is not cooling the planet, it is reflecting all the heat back in. So, we must use something that during day will reflect light and heat and during night it will allow infrared wavelength to exit into space. Yet, we don't have the technology to do that.

The second step in terraforming is to bring to the planet all we need. We have to divert comets to bring in water and gasses for the atmosphere.

The third step is to bring life to the planet. In the first part, we will need genetically modified plants and bacteria, to transform carbon dioxide into carbon and oxygen, to neutralize natural toxins and to prepare the land. Finally, when the air becomes breathable, we can insert Earth life forms. Also, during this step, we will have to ameliorate chemical composition of rocks and seas.

Climate simulation Edit

We don't know exactly how a terraformed Vulcanoid would look like.

Latitude T(C)
90       -185
75       -15
60        15
45        35
30        51
15        63
0         74

This temperature model is for a spinning Vulcanoid, with no axial tilt.

Assuming a day length of 24 hours, day-night temperature changes should be over 30 degrees.

The shield will do its best to reflect light and heat. But, there is a chance that space mirrors or anti-greenhouse gasses will at some point not be exactly where they were supposed to be. This will create tiny holes into the shield. Through the holes, deadly amounts of light will reach the ground, scourging the surface and heating the area. Given the small apparent radius of a B - type star, a tiny hole of less then one degree is enough to do this damage.

If the planet is tidal locked, huge temperatures will reach on the illuminated hemisphere. On the night side, the shield will become heat permeable and will allow the planet to cool down. Temperatures will decrease dramatically, to values maybe below -200 C. If we keep a higher temperature on the dark side, the planet will not be able to cool.

Still, we don't know if there will ever be a cosmic shield able to deflect such high amounts of heat.

There is a high chance Vulcanoids will mot be chosen for terraforming and will be used for Industrial colonization.

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