Mira, the Wonderful

Although it's probably considered more of an autumn target, variable star Mira, "The Wonderful," in the constellation Cetus, is an object that veteran backyard astronomers the world over will seek out whenever it's above the horizon. Mira is what's known as a "long-period" variable. It waxes and wanes over a period of about 332 days. And its brightness varies from, at best, 2nd magnitude (like the North Star), to as faint as 9th or 10th magnitude. That means that when it's at maximum brightness, you can see it without any optical aid, but when it's at minimum brightness, you'll need either binoculars or a telescope to see it. In my blinking animated GIF, above, Mira was neither at minimum brightness nor at maximum brightness in the two images. Maximum brightness is expected in February of 2026. And that means I probably should have shot Mira back in October of 2025 to get minimum brightness, and then wait till February to get maximum brightness. 

I have to admit that variable star observing is not my cup of tea! For one thing, I'm not very good at guessing stellar magnitudes. And for another, I have a difficult time trying to remember when to go out and look at a certain star that's at maximum or minimum brightness. It doesn't matter if it's a long-period variable like Mira, or a short-period variable like Algol (in Perseus), I will almost always miss the minima/maxima events due to clouds or forgetfulness.

It's weird. Amateur backyard supernova hunting is nothing if not a lesson in patience. I spend weeks or months looking at thousands of galaxies before finding one supernova. So, you would think with that kind of background I'd be a natural at monitoring long-period variable stars. But variable star observing is different somehow from supernova hunting.

I think what it boils down to is that variable stars have established periods, and you need to be out there at the predicted date and time in order to see them at maximum and minimum brightness. Essentially, monitoring variable stars requires that you follow a schedule or routine. By contrast, supernovae are unpredictable. You can't know when a supernova is going to appear in a given galaxy. So, although I can exercise great patience in going from galaxy to galaxy each night without spotting a new supernova for months, that kind of patience doesn't help me when it comes to following the light-curve of a variable star. 

What I mean to say here is that observing variable stars isn't as much about patience as it is about punctuality. I got plenty of patience, but I am a proven failure at punctuality!

Of course, the type of backyard astronomy we settle on for our hobby comes down to a matter of choice. I have chosen supernova hunting because it fits my personality. If I had chosen variable star observing, I probably could plan my observing sessions accordingly, so that I would know when and which targets to observe. I could set reminders so that I'd make an attempt to be punctual. But the difficulty of estimating stellar magnitudes supersedes my ineptitude at punctuality. In other words, marking the maximum and minimum brightness predictions for a given variable star on a calendar might help me to observe them on time, but estimating their night-to-night differences in magnitude would be, for me, an exercise in futility.

Supernova hunting doesn't require any estimation of magnitudes. Well, if you wanted to, you could estimate the magnitude of a supernova, just like you'd estimate the magnitude of a variable star. But supernova discovery is more of a binary experience. It's either on or off. There's no wringing of hands. You either spot a "new star" in a galaxy or you don't.

But I digress....

This post isn't about supernova hunting. Nor is it about variable star observing. It's about Mira, the Wonderful. You needn't be a variable star observer to appreciate Mira's beauty. Because, like supernova hunting, when you look up at Cetus in the night sky, Mira is either visible or invisible! That's what makes it so wonderful!

And Mira is especially wonderful right now because it's nearly at maximum brightness! Yes, if you go out in the evening during the next month and look up at Cetus, you will be able to spot Mira! That is, if you know where Mira is, and if you have a dark enough sky.

Like I said, I'm not very good at estimating magnitudes, but I'd guess right now it looks to be about magnitude 3. In very dark skies, a 3rd magnitude star is fairly bright. But in the suburbs of Tucson, a 3rd magnitude star isn't very impressive or obvious. I should say that, at least for me, it's not impressive. My old eyes don't dark-adapt as well as they did when I was a young man. As I stand in my back yard and look at the "head" of Cetus, comprised of Menkar (α Ceti, at magnitude 2.5), Gamma (γ, at 3.5 magnitude), Xi (ξ, at magnitude 4.3), Mu (μ, at magnitude 4.3), and Lambda (λ, at magnitude 4.7), I can barely make them out. When I step outside in the darkness, before my eyes adapt, the triangle of Menkar, Gamma, and Delta (δ, at magnitude 4.0) is the easiest thing for me to see, but if I wait several minutes for my eyes to adjust to the dark, I can eventually see all five stars. Tonight, I could see that Mira was dimmer than Menkar, but slightly brighter than Delta.

Through the telescope eyepiece, Mira doesn't look all that wonderful! A moderately bright yellow star. It looks redder when it dims, but at maximum brightness, it's a yellowish star. It'll take a while to reach minimum brightness. In its roughly 332-day cycle, it takes 100 days to reach maximum brightness, and then 200 days to reach minimum again. If maximum brightness occurs in February, we'll have to wait until September for it to be at minimum brightness. 

September? That's a long way off! Are you gonna remember to go out in September to see what Cetus looks like in the absence of Mira? Better mark that calendar!

Below is a picture I took the other night showing the position of Mira in Cetus, which was in the western sky. Mira was given the designation Omicron (o) Ceti, so I annotated the image with "Mira" on one side, and "o" on the other. Afterward, I realized that the "o" might be misleading, in that it might be mistaken for a location (variable stars are often denoted with a circle indicating their position because they may or may not be seen). So, I'll just tell you now that Mira is the star between the word "Mira" and the Greek letter "o." Also note that the Pleiades star cluster, in Taurus, lies outside the field at upper right. As a guide to finding Mira, start by locating the Pleiades and then follow the dim line of stars to the southwest. To fine-tune your search, you can start at the Pleiades, but then star-hop over to Aldebaran. Draw an imaginary line from Aldebaran down to Menkar, in Cetus, and then continue on that imaginary line to Mira.