A Second Sun?

What would happen if a second sun appeared where Pluto currently is?

The core principle involved here is the theory of gravitation. We will be using the Newtonian theory, first formulated by Isaac Newton in the 17th century. The gravitational force is predicated on the mass of each object and the distance between them. This version of gravitation has since been replaced by General Relativity, described first by Albert Einstein, but still serves fine for large-scale approximations, which we will do here.

The Situation

Imagine it's any other day, like a Tuesday, you're going about your day when suddenly Pluto suddenly becomes a G-type main sequence star (the same type of star as the sun). This star is exactly identical to the Sun.

Assumptions

In order to make this problem more tractable, we make a few assumptions about the situation. First, the planets are basically aligned and at their furthest distance. This is important as the planets, and particularly Pluto, do not have perfectly circular orbits. Also this helps as the gravitational effect on the planets is more uniform. We will also only be looking at the effects in the short term. The long term effects on orbits is a complex problem that would likely take a fair amount of simulation, so I'll ignore it, for now.

As a notation note, I'll be using Sol1 to refer to the Sun we have now and Sol2 to refer to the star where Pluto is now. ^[i.n.]

Effects on Earth

Gravitation, as stated above, is predicated on three variables, the mass of object one, the mass of object 2, and the inverse square of the distance between them. The distance between Earth and the Sun (Sol1) is defined as one astronomical unit (AU), which is about 150 kilometers (93 million miles). The distance between Pluto (Sol2) and Earth is 48 times that distance. We'll first tackle the effects this change would have on us, since we're so self centered. The good news, sort of, is that Earth will remain in orbit mainly around Sol1. Since Sol2 is so very, very far away, its gravitational effect is very, very small compared to Sol1's (around 23 hundred times smaller). The overall effect is, essentially Sol1's gravity becomes slightly weaker and we move slightly further away from the Sol1.

The net effect? Earth gets a little colder and slowly drifts outwards, towards an equilibrium point between Sol1 and Sol2. This may sound bad, and it is. Net gravitational force from Sol1 is decreased, we drift outwards, and most likely slowly freeze to death. This outcome is predicted even without taking into account other effects of having a second sun.

Effects on Other Planets

What I'll be doing here is comparing the gravitational force exerted by Sol1 with the gravitational force exerted by Sol2 (on each planet). If the force exerted by Sol2 is the larger value, then it "captures" the planet. This is a fairly simplistic way of looking at this, and would only really apply in the short term. Using the mass of each planet along with each planet's distance we can gain an early estimate of what the new solar system will look like. We'll start from the outer solar system and work our way in. Starting, for some reason, with Pluto (not actually a planet). Pluto is gone, completely, vaporized; no gravitational effect from either star. Neptune is captured, just barely, by Sol2 whose gravitational effect is around two and a half times larger than that of Sol1. It is, in fact, the only planet captured outright by Sol2. All the other planets, while feeling some gravitational effect from Sol2, are still chiefly affected by Sol1. Neptune is the only planet remotely close enough to Sol2 to be more affected by its gravity than that of Sol1. The effects on Earth will be similar to effects on the solar system as a whole, with the added downside of the fact that we live here. The general effect on the planets is that at first they will spread out, moving towards Sol2 as it negates some of the gravitational force of Sol1. In a longer time frame, the orbits of the planets will become more and more perturbed and complicated. In fact, at a certain point, some planets may be ejected from the solar system or collide with Sol1 or Sol2.

^[i.n.]The general takeaway here is that in this situation, the solar system will change drastically. A side effect of this change: human extinction comes much sooner than most people currently expect. Luckily this situation has effectively zero percent chance of happening, so we can sleep easy at night knowing that Pluto will not become a star.

Wikipedia was a great help in finding the masses and orbital radii of planets. Solar System Article

Peer review

This edutainment science blog post explores the gravitational effects on the solar system if Pluto suddenly became a second Sun.

This blog post does a good job of answering a hypothetical situation in a way that I could easily understand. My main critique, in terms of content, is that there could be more information regarding what happens to the solar system. A good point of elaboration would be where you mention a decrease in the temperature on Earth. It would be interesting to know how significant this change would be, and you could also answer a possible misconception I had which is the distance of the Earth from the Sun is not extremely important with regards to temperature. Something like this might also make the post seem less repetitive, which is a valid point you had, though I think that simply may be due to the nature of the answer.

In terms of how scientific the writing is, I think you do a good job of not making it too complicated for the reader. However, I think it might make sense to add some more numerical answers to quantify your explanations. This could include just how far the Earth displaces after a year, or how fast it accelerates immediately after getting hit by the gravitational waves. I would also be interested to know how long it takes for the gravitational waves to reach Earth after Sol2 appears. Another small suggestion I would like to make in terms of scientific writing is that it might be worthwhile to explain what a "G-type main sequence star" since that might not be common knowledge.

In terms of your third point, I agree analogies are difficult to think of for this topic. One possible place for an analogy could be where you describe the distance from the Earth to the Sun. Personally, that is a number too large for me to comprehend, so it might make sense to compare it to something more common. Other than that, I think there is good potential for analogies for sections you can add. One idea could be looking into how many times bigger the Sun is compared to Pluto, and how many Plutos could fit inside of the Sun. This could then be compared to something like bouncy balls fitting inside of a jar. Something like this could help the reader grasp why Sol2 has such a large effect on the Earth even though it is so far away.

Instructor Note

There is a lot going well here. I was interested to see that you decided not to use any anologies, since they seem to integral to the style of the genre. I might also suggest adding a bit more information, perhaps on the effects on other planets, since your post is a bit short. Or choose a topic with more imlpications than this.