Mira: The Only Real Shooting Star
Our amazing universe is huge. It's dark, but beautiful, and it's full of amazing things. Each planet is different from another, and each star is more interesting than other. Here's another awesome star, called Mira, which has been popular among scientists from quite some time now. And there's a very good reason for it.
A Shooting Star? Isn't That Something We've All Seen?
I know what you're thinking. The only shooting star? How is that possible? Most of us have seen a "shooting star". It's not that unusual phenomenon, then why am I calling it as "the only shooting star"? Well to answer to your question, let's see what a regular "shooting star" is.
What is a regular shooting star?
Okay, so if you don't already know this, then this is going to break your heart! Here we go. The "shooting stars" we normally see in the night sky are actually meteorites. They glow because they move really fast and as they enter our atmosphere they start burning up, hence creating that bright sharp beam of light, making it possible for us to see.
There you go! What you once thought was a star, is actually dust and small pieces of rock. Reality sucks sometimes, doesn't it?
Science is heartless, but true.
So, Does This Mean That We Never Had Any "Shooting Stars"?
Nope. That's not true. You can guess by the title of this article, there is a "shooting star", which is actually a star. And did you know that it's the only real shooting star. Well, there must be many more considering how big the universe is, but this is the only one known to human kind!
This real shooting star is a red giant which was discovered 400 years ago, and have been studied thoroughly ever since. Still, it managed to astound the astronomers in 2007, when something which was never before seen ever was discovered.
The name of the only real shooting star is Mira; pronounced as My-rah, which means wonderful in Latin. And trust me you will agree with the name once you get to know it, which I'm going to help you with in a minute.
But First, Fun Poll!
Did You Knew That Shooting Stars Are Actually Not Stars?
Getting To Know The Star: Mira, The Wonderful
Located 200-400 light years from our sun, this pretty old red giant was the first ever variable star to be discovered by mankind. A variable star is one whose brightness varies with time. It lies in the Constellation of Cetus, also known as Whale. It's also known as Omicron Ceti.
Mira, along with its white dwarf companion, officially known as Mira A and Mira B, together forms a binary system. Mira is a star, whereas it's fellow component used to be a star. A white dwarf is basically stellar core remnant, meaning, it was a star which is now burnt down to core. They orbit around each other every 500 years.
But What's So Interesting About This Star?
It's a pulsating variable star, which means that its surface pulsates in such a way that it brightness increases and decreases with time. This means that every once in a while the star disappears from the sky! Not literally, but we can't detect this star during this period; we can't see it, nor can we get any pulses/waves from the star. It's like the star occasionally takes a break.
Mira follows a cycle of 322 days, and becomes one of the brightest stars in its constellation every 11 months, stays that way for some time and then disappears again.
It's orb swells and contracts by around 20%, and when it's the largest and the brightest, Mira is more than 300 times larger than Sun.
Apart from being a variable, what makes this star interesting is the fact that it travels at a super-sonic speed of 291000 miles/hour! That's a very unusual speed for a star. We still don't know the physics behind how it managed to get that high speed, but it's possibly due to gravitational boosts from other passing by stars over times.
According to NASA, since it's an old, slowly dying star it's undergoing mass loss, and as it moves that fast it sheds material in our galaxy that will act as the raw material for new stars, planets and possibly, life! As per NASA, it has already released enough material to give rise to 3000 Earth sized and 9 Jupiter sized planets over the last 30,000 years!
Mira has given our scientists a chance to study how things work in space; how planets and stars are formed.
But this is not it.
The Incredibly Long Tail Of Mira!
This is what grabbed the attention of scientists towards Mira again. In 2007, the Galaxy Evolution Explorer (GALEX) discovered during its routine night sky survey in UV light, that this star had one feature that no other star had ever exhibited. GALEX captured a trail behind the star, which was a whooping 13 light years long!
Even though it's been studied thoroughly ever since its discovery 400 years ago, it was not until 2007 that the trail was seen, and that too by pure accident.
1 Light Year= 5.88 trillion miles (9.5 trillion km).
The nearest star to our sun is located 4 light years away. So, you can imagine how big that trail is.
This amazingly long trail formed over tens of thousands of years. However, we don't exactly know how it got so big, and why Mira happens to be the only star that has it.
What Forms Its 13 Light Years Long Tail And Why It's Only Visible Under UV light Spectrum?
So, we know that Mira moves at an incredibly high speed. Now, as it moves, gas builds ahead of the star. This is known as bow shock. The gas in bow shock, which is hot, mixes with the cool hydrogen in the wind blowing off Mira. The now heated up hydrogen flows around and behind the star forming a turbulent wave.
The reason that this trail can only be seen in UV light is because when hydrogen is heated, it transitions into higher energy state, and since high energy states are unstable stars, it then loses energy by emitting UV light. This process is known as fluorescence.
This is the reason why GALEX could identity this trail, since it is very sensitive to UV lights.
The Evolution Of The Trail, As Per NASA
The picture below shows the 13 light year long trail of Mira. The oldest material lies at the very end of the picture, i.e. far left. The material being released from Mira is oxygen, carbon and some other important elements require for the birth of new planets and stars.
It also shows few historical events that happened as the trail of Mira developed over the time. One example being, when material near the end of Mira's tail was just being released, Neanderthals had just recently died out.
It just blows your mind when you think about how long and old it is, doesn't it?
A Little About Red Giants
Red giants are very old stars. They are the largest of all kinds of star. The red giant indicates the last stage of a star. That means, a red giant is a dying star. Don't be sad, though. Stars have a pretty long life. A star usually becomes a red giant after around 11 billion years of its existence! Red giant is the ultimate phase of a stellar life.
Mira was once just like our sun. But with time it used up all of its energy and now have got swollen up, increasing a size. It's currently using its remnant fuel, and once the fuel is exhausted, it will ultimately turn into a planetary nebula.
A planetary nebula is the cloud of expanding glowing ionized gases, which is ejected from a red giant as it dies out. This cloud or nebula, will then fade away with time leaving behind the burnt core of the star, which will now be called as the white dwarf. This is the fate of all stars.
Our sun is expected to become a red giant in about 5 billion years. So, long story short, one day our own sun will consume our planet, as it will expand to be one giant red star. Brutal, right? But that how things work in space.
Today, we have many stars that belong to the Mira-type star category, named after Mira of course, exhibiting similar variability like Mira, but no other star has ever shown any kind of trail, let alone one which is 13 light years long.
Here Are Some Upcoming Mira Maxima
Following are the expected dates when Mira will shine the brightest in coming days. You can see the star with bare eyes (but not the trail of course, remember)!
- 2018: Nov 26, 20:38
- 2019: Oct 24, 19:40
- 2020: Sep 20, 18:43
- 2021: Aug 18, 17:45
- 2022: Jul 16, 16:47
- 2023: Jun 13, 15:50
Bonus Facts For The Nerds Out There!
- The white dwarf is actually very dense. According to National Geographic, 1 teaspoon of its matter would be equal to about 5.5 tons in Earth, i.e, equal to the weight of an elephant!
- The word 'planetary' in planetary nebula has actually nothing to do with planets. It's a misnomer, as when it was discovered first it resembled the round shape of a planet.
- Speaking of variable stars, our own Sun is a variable star. However, its behaviour is not as bizarre as variables like Mira. Over an 11 year solar cycle, Sun's energy output varies by around 0.1 %.
- Wondering why a star pulsates? When a star is dying out, there comes a phase where the pull of gravity and the unsteady burning of the fuel of the star, kind of, fight each other. Each one of them dominates for a few months before the other takes over.
- According to the pictures from the Hubble telescope, Mira is not spherical in shape. It's rather asymmetrical, possibly due to mass loss as it ages and burns down to death.
An Artist's Illustration of Mira, The Wonderful and It's Mind-Boggling Long Trail!
Before You Leave..
Did you find Mira, The Wonderful interesting?
I like the night. Without the dark, we'd never see the stars.
© 2018 Sneha Sunny