What is a circumpolar star?
A circumpolar star is a star that has never been seen because the gravitational pull of another star pulls it into its orbit. The term was coined by Dutch astronomer Jan Oort. A good example is our Sun. We are not only the largest (main) star in our galaxy, but we are also one of the smallest: a little over 100 times more massive than Earth, but we’re about 5 times smaller than our Moon.
The Circumpolar Stars
Let’s start with a simple question: What is a circumpolar star? I’ll give you an example from astronomy to illustrate it:
A circumpolar star is a star that is never located in any one direction but rather has a constant position relative to the center of the Milky Way galaxy (which is the same as being located at the center of the galaxy). This means that every star — including our own sun — can be defined as belonging to this category.
Okay, so now we have some knowledge of what a circumpolar star is, but what exactly are they? Well firstly, they are stars that have no discernible motion across the sky (i.e. not moving very fast in any direction).
I’m sure you can come up with lots of examples here (including Kepler-27, which has been found to be rotating at an extremely fast rate), but this is just one example. The point is that these stars are not moving in any way whatsoever — and thus do not affect our ability to define them as stars. There are some other ones, such as pulsars which are affected by their spinning and thus become visible when they go dark.
However, there are other stars that move around: there have been instances where two stars have been observed to reach such speeds (one being 93 million km/h [56 million miles/hour] while the other was at a mere 45 million km/h [28 million miles/hour]). The reason for this speed difference between them lies partially in their mass: while they do move around they do so in different directions (currently at least) and also in different ways (moving more quickly than others).
If you look at these objects carefully you will see something else interesting: their shape. While your eyes might not be able to pick it up immediately at first glance, when you look closer you will notice small oval-shaped features within the object itself. These features are generally associated with “circular” motions – where each layer within an object revolves around another layer within it – or “elliptical” motions – where each layer orbits about another layer within it. These can be seen coming from NASA’s WISE space telescope which discovered many of these objects.
Here’s an image from NASA’s WISE telescope showing many of these objects and how their shape changes over time:
These features aren’t only associated with circular or elliptical motions but also with
How to Recognize a Circumpolar Star
There are approximately 100 billion stars in the Milky Way galaxy. Some of them are very bright, like the Sun. Others, like the circumpolar stars, aren’t as bright and barely visible to the human eye. But they are there and they represent a new class of variables: “circumpolar” variables.
The idea came from trying to think through what makes a star dip into darkness when it has started to become a circumpolar variable. It turns out that there are only two things that can really make this happen:
1) an obvious change in temperature (like our Sun); or
2) a change in luminosity (like a supernova). The reason is that if you have a constant luminosity, you cannot dim your light — because if you dim your light, you’re going to end up with less light than before — which means that the star will not be able to dip into darkness.
If we could figure out how to make stars without changing their luminosity, we would have made it so that circumpolar variables would not be detectable. This is because stars don’t appear dimmer than before because they haven’t changed their luminosity at all; rather, their brightness is constant for any given time interval.
In this section, I want to explore another way of thinking about the role of circumpolar stars in the world: what is a circumpolar star?
What is a circumpolar star? It sounds like a strange thing to say. It’s not really something that exists; it’s more of an idea. But it can be if you will give it that word. A circumpolar star has two main characteristics:
1) It doesn’t have an axis nor does it have an inclination as measured on Earth’s axis (it has neither pole nor equator). They are just objects that happen to be orbiting around the same spot in space, whether they are called “stars” or not. But there are plenty of examples where the two characteristics do overlap — e.g., binary systems with one “star” and one “planet.”
2) A circumpolar star is defined as something whose orbit crosses both equator and pole regularly (although sometimes this doesn’t happen). If you look on Mapquest for any particular place on Earth you can find information about how much latitude/longitude each point lies along with its distance from the poles (the latitudinal and longitudinal axes), which can help us narrow down our search (there are some places which don’t fall into either category).
The most common form of such an object is the Sun, but there are many other examples that fall into either category; e.g., comets (which tend to be long-period comets but which also occasionally show themselves close enough to Earth for us to see them); exoplanets (which come from planets outside our solar system); even asteroids or other objects like meteors or Kuiper Belt Objects which may cross the poles but don’t fit into either category either…
If we ask what makes these things set off alarm bells in us — assuming we haven’t already done so — then we should first ask why they shouldn’t exist as normal celestial bodies within our solar system… They do exist! There are thousands upon thousands of them around our galaxy – far enough away