has seen a falling star, also known as a shooting star.
I confess, I sincerely believed such was the case
that these were, in fact, stars -
much like I believed in Santa Claus.
But then I heard the shocking truth:
these are not, in fact, stars.
When peering into the sparkling
emptiness of the night sky,
I watched as another meteoric body,
for the umpteen-billionth time,
tried to ram through the earth's atmosphere.
This happens constantly, day in and day out.
Millions of cosmic bodies hurl themselves
towards the surface of our planet every day.
Really, there is nothing very special going on here.
So, despite the apparent absurdity of the phrase:
It turns out that real falling stars
do exist in our universe.
Fasten your seatbelts, ladies and gentlemen.
Once again, we set off into deep space.
Meet Mira, or as it is also called,
Omacron Ceti.
A sizeable star, it is 700 times larger than
the diameter of our sun.
It is an even stranger and more surprising star
than Betelgeuse, the heroine from our last installment.
The first mention of this beauty is found in Hipparchus
in 134 B.C., as well as
in the testimonies of Chinese astronomers
later in the year 1070.
But its almost supernatural properties
were discovered only recently.
Pastor/astronomer David Fabricius
quite by chance, and without realizing it,
discovered a new type of star
on the morning of August 13, 1596.
At that time, he was just watching Mercury.
Or rather, he was going to measure the angular distance
from the planet to the star glittering nearby
at an apparent magnitude of 3
in the constellation of Saetus.
Interestingly, he had never come across it before,
and it was also notably absent from
all the stellar maps and globes.
Though, of course, maps and globes were not as
accurate in ye olden days,
and the disregard for some not very bright star
was commonplace.
Fabricius began to keep an eye on the stranger,
and lo and behold, its brilliance grew
right up to a magnitude of 2.
And it became the brightest star in its constellation
by the end of that August.
But then in September, the star faded.
And by mid-October, it had disappeared completely.
In full confidence that this was a different, new star,
Fabricius stopped observing.
But to his great surprise, he came across
this great mysterious travelor
13 years later on February 15th, 1609.
But, to be fair, astronomer Johann Bayer
managed to notice it about 6 years before this in 1603.
He entered the data into his famous star atlas
but had not yet suspected the super properties
of his find.
By the way, by that time, the star had already reached
a stellar magnitude of 4.
Various astronomers from around the world
began to closely moniter
Omicron Seti for the next several decades.
So, for example, the Polish astronomer Jan Hevelius
who observed the stellar body from 1659-1682,
called it Mira, which is from Latin,
and translates as "amazing."
And he was absolutely right.
This star is amazing.
Usually it is so dim that it is quite difficult to see
with even a small, amateur telescope.
But due to its peculiarity,
it becomes the brightest star in the constellation Saetus
at certain times.
The so-called "peaks."
Then it fades again and becomes almost invisible.
And then again, and again, and again
everything repeats.
Scientists finally, by the middle of the 17th century,
established that this miracle represented
a new type of variable star,
with a very long period of brightness
and a very large amplitude.
To put it simply, Mira is a star
that constantly changes its brightness,
but it happens with a fair bit of irregularity.
The glitter of a star, for those who do not know,
is its apparent stellar magnitude.
The same as luminosity or even simpler, brightness.
Using the astronomical scale,
smaller numbers are brighter.
The brightness of Mira increases
three and a half times in just 332 days.
From a brightness of magnitude 10,
when it is almost invisible in a telescope,
up to a magnitude of 2,
when it becomes the brightest in its constellation.
As I said, there is no pattern
to her behavior.
As a matter of fact, the period and range of brightness
changes and is completely unstable.
One time Omicron Seti went from
the relatively dark 9th magnitude
and then increased to the 5th, and then back again.
Another time, she faded to the 10th magnitude,
but then shot up to her maximum
brightest magnitude of 2.
As you can see, the fluctuations in luminosity
are simply immense.
But what does all this mean?
The luminosity of Omicron Seti,
aka Mira, at the minimum of its brightness
almost corresponds, or is even slightly less than,
the luminosity of our sun.
That means then, that at the maximum,
the brightness of Mira will surpass that
of our sun by 700 times,
and sometimes by as much as
1,500 times the brightness of our sun.
The whole point of this is this:
when red giants pulsate,
the temperature of their surface
also changes, which immediately affects
the optical properties of the stellar atmosphere.
As the temperature rises, the chemical compounds
decompose, and the atmosphere
becomes more transparent.
Also, a considerable role is taken by
hot hydrogen masses, which erupt into the atmosphere
during the periods of maximum brightness and
further increase the brightness of the star.
At least, this is the most plausible explanation
which I have managed to unearth
of the amazing changes that regularly
occur with Mira Seti.
And still there is something more.
Scientists noticed in 1919 that
a second spectrum was superimposed
over the Mira spectrum.
And it belongs to a very, very hot white star.
A satellite was discovered very close to Mira
4 years later.
This hot little star is a white dwarf called Mira B.
which, by the way, literally feeds
on its much larger neighbor.
Little Mira B orbits the giant Mira A
only once every 400 years.
And therefore, the satellite has made just one complete
revolution around Mira A since the time of Fabricius.
The average distance from the main star
to the orbit of the white dwarf
is about 70 astronomical units.
That is to say, 70 times the average distance
from the earth to the sun.
And the most interesting thing is that
this little dwarf star has similar properties
to her much more voluptuous friend.
The white dwarf also changes its brightness regularly.
But this happens for several other reasons.
Mira B has an accretion disk through which
the white dwarf interacts with the main star,
sucking away stellar matter from her much larger sister.
Because of the unevenness of the supply of this
substance, the luminosity of the satellite also changes.
On average, the brightness value of the dwarf
ranges from magnitude 12 to 9.5.
It should be noted that the measurement of changes
in brightness in stars of this type
is a monumental amount of astronomical work.
Just imagine in order to obtain the amplitude
of oscillations of the luminosity of a star
for a period of 13 years,
scientists need to take into account
and superimpose all the fluctuations
in the brightness of the star during this period.
And their duration, by the way,
is measured in minutes.
And finally we come to our last
couple of delicious tidbits.
The Galaxy Evolution Explorer Satellite,
also known as the Galex,
is an orbiting ultraviolet space telescope
launched in 2003.
The Galex discovered a tail of matter
stripped from the outer sphere of Mira A,
like that from a comet.
A gigantic tail of material,
the length of which is about 13 light years.
So that you understand how long this really is,
the distance from our sun to the closest star
is about 4 light years.
That's a mighty long tail.
Most of the stars in our galaxy
slowly rotate around its center,
moving about the same speed and in the same direction
as the interstellar gas.
In contrast to this,
Mira is shooting through the galactic gas cloud
at a speed of 130 kilometers a second.
As a result, the matter thrown out by Mira
is simply blown back, forming a bow wave
tail of compressed gas.
As calculations show, every 10 years,
the star drops a mass equivalent
to that of the entire earth.
To form such a tail, the star has taken at least
30,000 years.
Oh, how I would like to see something like this up close.
It is a pity that I would need
to be a god to make it happen.
A gigantic swelling located in front of this star
is clearly visible in these pictures
from the Galex telescope.
This is the region of the shock wave.
Something like this is formed in front of a boat's nose
when cutting through water at high speed.
Or, for example, in front of a bullet
moving at supersonic speed.
This is matter thrown out by the star
experiencing a head on collision
with particles of interstellar gas.
And here my story comes to an end for today.
In conclusion, I should like to add that
currently, we have discovered more
than 46,000 such variable stars in the Milky Way,
and about 10,000 in other galaxies.
And this is only the beginning
as more are being discovered every year.
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Until next time.