Procyon: A System in Chaos

Procyon (bright spot) showing it’s white dwarf (Procyon B) and the 40 year orbit they have around each other. 1.7 billion years ago Procyon B was a red giant.

While Thalassa is a fictional planet, the science of the Procyon system in SOT is based on real research and our current understanding of stellar evolution and binary star systems.

Procyon: A Binary Star System

Procyon is the 8th brightest star in the night sky and thus a highly visible star. Together with Sirius (the brightest) and Betelgeuse (11th brightest), it is part of the Winter’s Triangle. Only 12.46 light years away from us, Procyon is in our close stellar neighborhood and is the 15th closest star to earth. It is a double star with a faint but invisible to the eye white dwarf companion, the remains of a bigger star.

Stars are classified by their mass and temperature, which determines their color. Earth’s sun is a yellow G-star while Procyon (Procyon A in the binary system) is a slightly larger yellow-white F-star (1.5 times our sun’s mass) . As such, it is seven times brighter than our sun. The light on Thalassa would be yellow-white, not yellow, as it is on earth, and light-trapping photosynthetic organisms may use different pigments and hence display different colors than plants on earth (Kiang, 2008). This is why the fronds and lichen-like creatures on Thalassa are yellow, orange, and red, not green.

F-stars also emit 2-7 times the amount of cell-damaging ultraviolet light (UV) as our sun, which would likely inhibit the development of life on land. However, seawater is a good shield against UV light, especially in the deep sea, so ocean creatures are protected from UV.

Because bigger stars burn brighter and hotter they die much faster than smaller stars, Procyon A will only last two billion years compared to our sun’s 10 billion year life span. Since it is now 1.9 billion years old it will transition to a red giant in the next 10-100 million years.

The size of Procyon A & B relative to the earth and our sun. Source.

Procyon A’s white dwarf, Procyon B, was once a very bright bluish B-type star 2.6 times the mass of our sun. Because it burned hotter, it turned into a red giant after a billion years before collapsing into a small white dwarf, smaller than Earth. On Thalassa, Procyon B would appear twice as bright as a full moon.

Procyon’s neighbors’ red giant phase

When a star runs out of hydrogen fuel to fuse into helium within its core it begins to collapse while the outer atmospheric envelope expands. After a few million years the red giant ejects its outer layers and then collapses into a white dwarf. Procyon B went through these stages about a billion years prior to the setting for SOT. During the end of Procyon B’s life, it would have ejected a significant amount of ionizing radiation and UV light into the region which would have a disruptive effect on the asteroids and comets around the binary star system.

Rain of Debris

Artist’s illustration of comets raining down on a planet. Source.

During the early life of all solar systems, debris remains from planet formation which includes asteroids and comets. Asteroids are made of metals and rocky material and formed closer to the star, where it is too warm for ice to remain solid. Comets are made up of ice, dust, and rocky material and are formed farther from a star where ice does not melt. As comets approach a star their ice melts and vaporize to form a tail.

Our solar system, and likely similar systems with planets, went through several hundred million years of collisions from asteroids and comets called the late heavy bombardment period. Most of the craters on the moon, and those visible on other planets, satellites, and asteroids, were created during this time period which occurred 4.1-3.8 billion years ago (Gomes et al., 2005). Few of these craters are visible on earth due to erosion and plate tectonics, but there are some.

It is likely other solar systems had similar episodes of intense collisions within 500-800 million years of their formation, such as Procyon. In addition, in SOT, it is postulated that when Procyon B’s red giant blasted off its atmosphere, it disrupted the asteroids in the system, and the comets in its Oort Cloud, causing a second period of intense bombardment. As a result, Procyon is envisioned as displaying numerous comet tails, like spokes in a wheel, and the frequency of asteroid and comet collisions with Thalassa is relatively high.

Artist’s illustration of comets plummeting a solar system as envisioned for Procyon and Thalassa. Source: NASA.

Procyon’s Orbit

As a binary star system, Procyon A and B orbit each other, with a period of 40.8 years. Their orbit is elliptical (not a circle) and the distance between the stars varies between 8.9 AU and 21.0 AU. One AU is the distance from the earth to the sun, about 93 million miles. At their closest, they are about the same as the distance between us and Saturn; at their farthest about the distance between us and Uranus.

The orbit of Procyon’s white dwarf around Procyon A. Source.

Procyon A and B were at periastron (their closest) in 1967, in 2008, in 2050, and will be on May 15, 2090, when Syzygy between the white dwarf and two moons occurs in SOT. This is one reason the book’s setting is during 2089-90 as it corresponds with the actual peristron’s date…

References and Further Reading:

2 responses to “Procyon: A System in Chaos”

  1. […] Another fact to ponder is that Mars was geologically young when there were oceans so you need to imagine a turbulent, more dynamic world, with lots of volcanism, flooding, and frequent bombardment by asteroids. The Procyon system, including Thalassa, is based on an early era in our solar system which is known as the Late Heavy Bombardment period when a disproportionate number of asteroids collided with the inner terrestrial planets, including  Mercury, Venus, Earth, and Mars. Estimates are that serious environmental damage on these planets would occur about every 100 years. Modeling of these impacts has estimated that tsunamis generated in the Martian ocean could have been as high as 400 feet and moved at rates up to 35 miles/hr in coastal areas (Iijima et al., 2014). So if you were surfing on Mars it could get very interesting, as it was on Thalassa. Although Thalassa was set at the age of Procyon A (1.7 billion years) the collapse of the Procyon B red giant 1.2 billion years earlier was theorized to create a bombardment period that lasted to the present time. There’s more on that here. […]


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