Thanks to MagellanTV for sponsoring today’s video.
Thanks to MagellanTV for sponsoring today’s video.

The Solar and Heliospheric Observatory, also know as SOHO, recently celebrated its 25th
The Solar and Heliospheric Observatory, also know as SOHO, recently celebrated its 25th

anniversary in space.
anniversary in space.

During these 25 years, it has observed the solar wind, watched out for dangerous coronal
During these 25 years, it has observed the solar wind, watched out for dangerous coronal

mass ejections, and observed the atmosphere of the Sun.
mass ejections, and observed the atmosphere of the Sun.

An unintended consequence of its observations around this region were the discoveries of
An unintended consequence of its observations around this region were the discoveries of

over 4000 Sun grazing comets, most of which we had no idea existed until they came into
over 4000 Sun grazing comets, most of which we had no idea existed until they came into

SOHO’s view.
SOHO’s view.

And SOHO isn’t the only solar observatory, the STEREO spacecraft, and the Solar Dynamics
And SOHO isn’t the only solar observatory, the STEREO spacecraft, and the Solar Dynamics

observatory, have all seen new comets.
observatory, have all seen new comets.

And what’s so cool about that is that they weren’t designed with that in mind at all.
And what’s so cool about that is that they weren’t designed with that in mind at all.

I’m Alex McColgan, and you’re watching Astrum, and in this video I wanted to look
I’m Alex McColgan, and you’re watching Astrum, and in this video I wanted to look

at some of the most impressive of these comets, try to understand how they interact with the
at some of the most impressive of these comets, try to understand how they interact with the

Sun, and how the Sun interacts with them.
Sun, and how the Sun interacts with them.

Sun grazers are comets that do just that, they graze the Sun as they pass, with the
Sun grazers are comets that do just that, they graze the Sun as they pass, with the

closest parts of their orbits taking them within a hair’s breadth of the Sun’s surface.
closest parts of their orbits taking them within a hair’s breadth of the Sun’s surface.

Often, they will pass through the Sun’s huge atmosphere, called its corona.
Often, they will pass through the Sun’s huge atmosphere, called its corona.

These comets are mainly long period comets, comets whose orbits take hundreds to thousands
These comets are mainly long period comets, comets whose orbits take hundreds to thousands

of years to complete.
of years to complete.

Because of their orbit’s extreme elliptical nature, they build up tremendous speed as
Because of their orbit’s extreme elliptical nature, they build up tremendous speed as

they approach the Sun, sometimes accelerating to 0.2% of the speed of light, an absolutely
they approach the Sun, sometimes accelerating to 0.2% of the speed of light, an absolutely

incredible speed for a particle, let alone a house sized object.
incredible speed for a particle, let alone a house sized object.

The majority of Sun Grazer comets actually all originate from one, large comet that was
The majority of Sun Grazer comets actually all originate from one, large comet that was

ripped apart several hundred years ago.
ripped apart several hundred years ago.

This group of Sun Grazers, shown in red in this video, is known as the Kreutz Sun Grazers.
This group of Sun Grazers, shown in red in this video, is known as the Kreutz Sun Grazers.

What tends to happen over time is that the fragments from the larger comet spread out,
What tends to happen over time is that the fragments from the larger comet spread out,

meaning that there is a reasonably steady flow of them.
meaning that there is a reasonably steady flow of them.

As the largest of these fragments also pass by the Sun, they too may break apart into
As the largest of these fragments also pass by the Sun, they too may break apart into

even smaller comets.
even smaller comets.

And the reason we believe most Sun Grazers originated from the same comet?
And the reason we believe most Sun Grazers originated from the same comet?

Well, they all tend to follow to same orbital path.
Well, they all tend to follow to same orbital path.

The brightest comet in the last millennium, known as Comet Ikeya-Seki, was probably a
The brightest comet in the last millennium, known as Comet Ikeya-Seki, was probably a

fragment.
fragment.

It was so bright as it approached the Sun that it could even be seen during the day.
It was so bright as it approached the Sun that it could even be seen during the day.

You may have heard of another famous fragment of this comet that dimly illuminated the sky
You may have heard of another famous fragment of this comet that dimly illuminated the sky

in the southern hemisphere in 2011, called Comet Lovejoy.
in the southern hemisphere in 2011, called Comet Lovejoy.

While Comet Lovejoy wasn’t as bright to the naked eye, it did make for some very impressive
While Comet Lovejoy wasn’t as bright to the naked eye, it did make for some very impressive

long exposure images, and was seen by all the Sun observing satellites.
long exposure images, and was seen by all the Sun observing satellites.

Comet Lovejoy was not expected to survive this close encounter, as it would have been
Comet Lovejoy was not expected to survive this close encounter, as it would have been

in the Sun’s one-million-degree Celsius corona for more than one hour.
in the Sun’s one-million-degree Celsius corona for more than one hour.

However, astonishingly, it fizzed away from the other side of the disk, mainly intact,
However, astonishingly, it fizzed away from the other side of the disk, mainly intact,

although probably severely impacted from the experience.
although probably severely impacted from the experience.

The same thing happened to another comet, Comet ISON.
The same thing happened to another comet, Comet ISON.

You may remember that comet ISON was expected to be a bright comet, potentially visible
You may remember that comet ISON was expected to be a bright comet, potentially visible

to the naked eye when it passed by the Sun in 2013, alas that wasn’t to be.
to the naked eye when it passed by the Sun in 2013, alas that wasn’t to be.

However, it still made for good viewing for the Sun observing satellites.
However, it still made for good viewing for the Sun observing satellites.

ISON’s approach was bright and impressive, and upon reaching the other side of the Sun,
ISON’s approach was bright and impressive, and upon reaching the other side of the Sun,

it faded out.
it faded out.

Scientists can’t be sure if the nucleus survived or not, but if it did, there are
Scientists can’t be sure if the nucleus survived or not, but if it did, there are

certainly no volatile substances on it anymore, all that’s left is probably dust.
certainly no volatile substances on it anymore, all that’s left is probably dust.

However, these are some of the biggest Kreutz Sun Grazers we’ve ever observed, their nucleus’
However, these are some of the biggest Kreutz Sun Grazers we’ve ever observed, their nucleus’

maybe being a few hundred metres in diameter.
maybe being a few hundred metres in diameter.

Most of the smaller comets were not known about until they actually came into the view
Most of the smaller comets were not known about until they actually came into the view

of a sun observing satellite.
of a sun observing satellite.

Due to their small size, being only 10s of metres across, many of the smaller comets
Due to their small size, being only 10s of metres across, many of the smaller comets

are completely snuffed out by the Sun immediately after passing by too closely.
are completely snuffed out by the Sun immediately after passing by too closely.

Which means unfortunately, they were vapourised pretty much immediately after they got discovered.
Which means unfortunately, they were vapourised pretty much immediately after they got discovered.

Sometimes they will pass around the back of the disk of the Sun, never to re-emerge from
Sometimes they will pass around the back of the disk of the Sun, never to re-emerge from

the other side.
the other side.

Although at other times, the angle of the comets orbit means we can witness this vaporisation
Although at other times, the angle of the comets orbit means we can witness this vaporisation

as it happens.
as it happens.

At this distance from the Sun, the heat is incredible, and the gravity is overwhelming.
At this distance from the Sun, the heat is incredible, and the gravity is overwhelming.

The icy comets not only evaporate quickly but the rocky elements of them are also ripped
The icy comets not only evaporate quickly but the rocky elements of them are also ripped

apart from tidal forces.
apart from tidal forces.

Our own close encounters with comets show that they tend to be structurally weak and
Our own close encounters with comets show that they tend to be structurally weak and

very porous, sometimes nothing more than a pile of rubble held together by its own gravity.
very porous, sometimes nothing more than a pile of rubble held together by its own gravity.

So, combine that with the influence on the Sun, and even the largest sun grazer comets
So, combine that with the influence on the Sun, and even the largest sun grazer comets

will come away heavily scarred.
will come away heavily scarred.

Now there’s an interesting phenomenon that sometimes happens when a Sun Grazer passes
Now there’s an interesting phenomenon that sometimes happens when a Sun Grazer passes

by the Sun, and that is that a CME will go off at the exact moment the comet passes by.
by the Sun, and that is that a CME will go off at the exact moment the comet passes by.

There are numerous examples of this.
There are numerous examples of this.

However, scientists are still of the opinion that there is no mechanism for a Sun Grazer
However, scientists are still of the opinion that there is no mechanism for a Sun Grazer

to cause a CME, these comets simply aren’t big enough to have any consequential impact
to cause a CME, these comets simply aren’t big enough to have any consequential impact

on the Sun, so it is currently believed that these examples you see here are purely coincidental.
on the Sun, so it is currently believed that these examples you see here are purely coincidental.

What scientists enjoy about Sun Grazers though is that while we can’t send probes deep
What scientists enjoy about Sun Grazers though is that while we can’t send probes deep

into the Sun’s corona, it’s simply too hot for that, we do have these thousands of
into the Sun’s corona, it’s simply too hot for that, we do have these thousands of

comets that are willing to take the plunge for us.
comets that are willing to take the plunge for us.

And comets are perfect for us to observe what we are looking for, which is to better understand
And comets are perfect for us to observe what we are looking for, which is to better understand

the magnetic fields within the corona, so that we can better predict CMEs and space
the magnetic fields within the corona, so that we can better predict CMEs and space

weather generally.
weather generally.

Look how as a comet passes by its tail wiggles.
Look how as a comet passes by its tail wiggles.

The particles in the tail get heated so much, they turn into a plasma which can be seen
The particles in the tail get heated so much, they turn into a plasma which can be seen

easily by the UV cameras of the satellites.
easily by the UV cameras of the satellites.

Plasma reacts strongly to magnetic fields, so the wiggle you see in the tail is believed
Plasma reacts strongly to magnetic fields, so the wiggle you see in the tail is believed

to be due to the way in which the tail interacts with the magnetic field lines in the corona.
to be due to the way in which the tail interacts with the magnetic field lines in the corona.

Currently, space weather is something we don’t have a complete understanding of, so as more
Currently, space weather is something we don’t have a complete understanding of, so as more

comets pass through, the more we will begin to understand that environment.
comets pass through, the more we will begin to understand that environment.

So, there we have it, some of the most impressive looking Sun Grazer comets caught on camera
So, there we have it, some of the most impressive looking Sun Grazer comets caught on camera

by satellites that weren’t even designed for them.
by satellites that weren’t even designed for them.

Have you ever been fortunate enough to see a comet?
Have you ever been fortunate enough to see a comet?

What was your experience like?
What was your experience like?

I’d be interested to hear your stories in the comments below.
I’d be interested to hear your stories in the comments below.

As I mentioned, understanding the Sun’s Corona has very real implications for us here
As I mentioned, understanding the Sun’s Corona has very real implications for us here

on Earth.
on Earth.

That’s because the Sun’s Corona is the source of space weather and solar wind.
That’s because the Sun’s Corona is the source of space weather and solar wind.

You see, on Earth our electronics are actually quite vulnerable to the particles ejected
You see, on Earth our electronics are actually quite vulnerable to the particles ejected

from the Sun.
from the Sun.

If a sudden burst of particles heads our way in what is known as a coronal mass ejection,
If a sudden burst of particles heads our way in what is known as a coronal mass ejection,

they can damage our satellites and in extreme cases, knock out our power grid and internet.
they can damage our satellites and in extreme cases, knock out our power grid and internet.

There’s a documentary on MagellanTV that discusses this in detail, called Solar Superstorms,
There’s a documentary on MagellanTV that discusses this in detail, called Solar Superstorms,

which looks at some of the largest solar storms on record, and how we are preparing for the
which looks at some of the largest solar storms on record, and how we are preparing for the

next big one.
next big one.

You can watch this documentary and gain access to MagellanTV’s library of thousands more
You can watch this documentary and gain access to MagellanTV’s library of thousands more

by using my link in the description, which will give you a month free trial.
by using my link in the description, which will give you a month free trial.

This was a really high-quality documentary, plus it is in 4K, so I highly recommend checking
This was a really high-quality documentary, plus it is in 4K, so I highly recommend checking

it out.
it out.

Thanks for watching!
Thanks for watching!

And thanks as always to my patrons and members for supporting the channel.
And thanks as always to my patrons and members for supporting the channel.

If you want to support too, check the links in the description, but also liking, sharing,
If you want to support too, check the links in the description, but also liking, sharing,

commenting and subscribing really help get my videos recommended to others too, so please
commenting and subscribing really help get my videos recommended to others too, so please

consider that if you found value in this video.
consider that if you found value in this video.

All the best, and see you next time.
All the best, and see you next time.