When you’re learning about astronomy, you quickly get used to the idea that on a human timescale everything is static and nothing really changes. The Earth is going to be swallowed up by the sun,* but it won’t be for a few billion years yet. When you look up at the sky the light you see from other stars has been travelling for hundreds, thousands or millions of years. In general this is all part of the Copernican principle: on a universal scale there’s nothing special about where we are or when we are, other than that we could only be living at a time and place where planets are commonplace. Therefore, there’s not a very high chance of anything special happening whilst we’re looking.
However, that doesn’t mean that interesting things can’t happen. Before the end of the century, there will briefly be a new brightest star in the sky.
The star in question is V Sagittae (or V Sge to its friends). Sagitta—not to be confused with Sagittarius— is a small constellation adjoining Cygnus. Unless you’re an astronomy fan it’s the sort of constellation you might not even have noticed, as it’s small and it doesn’t have any very bright stars in it. Living where we do, I’d struggle most nights to see even its brightest star with the naked eye. V Sge is in theory just about visible in The Child Who Likes Animals’ telescope; it’s around magnitude 10, although it varies quite a bit and over quite short timescales.
Since it was first discovered it’s been realised that it was a bit unusual. It’s a binary system, with an “ordinary” sun-like star orbiting around a smaller white dwarf. More recently, astronomers realised that the pair of stars were getting noticeably brighter over time as their orbit shrinks and they get closer to each other. Last week, it was announced that at some time in the last three decades of the current century, they will finally spiral into each other and temporarily become the brightest star in the sky. If you want to know full details, this is the press release of the announcement from Louisiana State University, and here are links to the full data.
At present the time range is a bit on the vague side, but it will almost certainly happen in a 32-year span centred on 2083. No doubt, now that more astronomers know about this, we’ll get more data over the next few years to narrow down the time range. And even before then, V Sge will probably get a bit brighter over time, as it’s doubled in brightness in the past 90 years. I might even see if we can see it ourselves now if we get good conditions: its part of the sky is well-positioned for early evening viewing from here at this time of year. I’m not likely to see it go nova myself, but The Children might do.
* Assuming nothing else catastrophic happens to it first, such as being kicked out of the Solar System completely. It’s unlikely but it’s not impossible.