Items Featured In TGP NOMINAL Xtra - August Skies 2018
If you are a regular listener to the show, you may recall that we have spoken have spoken about the main event in August before, in fact it was the subject of my first ever talk back in 2015…
The Perseid meteor shower, one of the years best!
Now I am going to start off with talking about a comet that is visible most of this month called 21P/Giacobini-Zinner (Named after Michel Giacobini and Ernest Zinner, the scientists that discovered it)
which should be within binocular sights.
It will brighten over the month, passing over the constellation Cassiopeia,
the vain queen and mother of Andromeda.
which should be within binocular sights.
It will brighten over the month, passing over the constellation Cassiopeia,
the vain queen and mother of Andromeda.
From 11th – 16th 21P/Gacobini-Zinner will flyby the star Epsilon Cassiopeiae and can be seen between this star and the constellation Perseus (The hero who saved Andromeda)
This is also where the Perseid Meteor Shower radiates from, but well come to this later.
This comet actually causes the later Draconid meteor shower later in the year around October as the Earth passes through the debris or path of the comet.
Nicely bringing us onto how meteor showers are created.
This is also where the Perseid Meteor Shower radiates from, but well come to this later.
This comet actually causes the later Draconid meteor shower later in the year around October as the Earth passes through the debris or path of the comet.
Nicely bringing us onto how meteor showers are created.
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A comet is a relatively small solar system body but plays a large part in this month's shower Although meteorites look pretty spectacular as they streak across the skies, they are pretty much just dust particles that come from the decaying surfaces of comets. . |
As a comet gets closer to our Sun its surface starts to heat up and snow yes pretty much snow just below the surface turns into a gas which then escapes, breaking up the surface of the dusty nucleus of the comet blowing these particles away from it. These particles form a stream all around the original path or orbit of the comet, which increases with each pass of the comet again and again, the larger the comet or more volatile the denser the stream is |
Our inner solar system is full of these comet streams and as the Earth orbits the Sun it often passes in and out of theses streams of decayed comets colliding with some of these meteoroids creating shooting stars.
Like this months Perseids, names have been given over time to these fixed events.
The Perseids are associated with the comet called 109P/Swift-Tuttle,
and once again it was named after the people who discovered them.
Lewis Swift and Horace Parnell Tuttle in 1862 discovered comet 109P/Swift-Tuttle.
109P Swift-Tuttle has an orbital period of around 133 years and was last seen in 1992,
but wont be seen again until 2126 which means most of us won't be seeing it.
Now, to have created such a splendid amount of dust to cause the Perseid meteor shower,
the comet must have been on the same path a few hundred times times 133 years.
As you have probably guessed, it's called the Perseid meteor shower,
because of where they radiate or seem to come from, that being the constellation Perseus.
The Perseid Meteor Shower technically officially started last month, which you might recall,
if you listened to July's Podcast.
we are currently passing through a cloud of dust particles left by a decaying comet hundreds if not thousands if not millions of years old orbiting our Sun.
As you are sat listening in your car, on your computer our out looking at the skies,
you are travelling at around 30km per sec through this stream.
So if it takes around two weeks to properly pass through the densest part of the Perseid stream…
I calculate that it must be, ….
PRETTY DAMN BIG!
But why do these tiny bits of dust create such amazingly spectacular displays in our skies?
When a meteor enters our atmosphere it goes from travelling through the vacuum of space with no friction, to travelling through air which as we know does create friction, quite a lot of friction.
They generally travel at tens of thousands of km’s per hour but when they hit earth,
the air in front of it compresses incredibly quickly, and when a gas is compressed its temperature heats up, causing the meteor to as well.
It starts to glow, the air will continue to burn the meteor until nothing is left,
which is the streak you see across the sky.
These re-entry temperatures can reach 1650 degrees Celsius, and larger particles may burn even brighter possible popping in the sky bursting leaving smoke trails. Often called fireballs.
Now if the meteor is generally over 30kg then only the surface layers are lost during re-entry where our atmosphere eventually slows it down to around 90mph known as freefall.
And it hits the ground becoming a meteor-ite,
There are three classifications of Meteorites
1. STONEY METEORITES – MOST COMMON AT 93% OF METEORITES SO FAR FOUND
2. IRON METEORITES – WHICH ARE RARER AT 5% OF METEORITES
3. STONEY-IRON METEORITES
Stoney- Iron Meteorites are the rarest of the three and have a similar compostion to the Rocky Planets
in our and other Solar Systems.
This is why NASA launched OSIRIS-REX in 2016 to visit 'Bennu', one of the Asteroids in the belt between Mars and Jupiter, as it may be the core of a failed planet.
As you can see from the above images, meteorites hitting residential areas are a very rare occurrence.
Lets move onto the month ahead!
On the 11th we have a new moon, which if you are into astrology means a new birth depending on which sign it is in…. but to us astronomers it means we can look into the depths of the universe past our solar system at the nebula within our galaxy or even at other galaxies farther afield… can I get a wahooooo
On the 12th-13th the Perseid Meteor Showere peaks at around 1-2am
from the constellation Perseus, with predicted meteors of 50-70 an hour.
Which is also the subject of UK Astronomy’s photo competition.
To get people out with their cameras or phones trying to capture them!
Lets move onto the month ahead!
On the 11th we have a new moon, which if you are into astrology means a new birth depending on which sign it is in…. but to us astronomers it means we can look into the depths of the universe past our solar system at the nebula within our galaxy or even at other galaxies farther afield… can I get a wahooooo
On the 12th-13th the Perseid Meteor Showere peaks at around 1-2am
from the constellation Perseus, with predicted meteors of 50-70 an hour.
Which is also the subject of UK Astronomy’s photo competition.
To get people out with their cameras or phones trying to capture them!
We have spoken about the Lunar X and V before but on the 18th it will be visible during the day. Have a look at the moon around 6.30pm and see if you can spot the illusion, caused by the terminator (shadow) across the moon on the top of it's craters, creating a X and V. |
On the 22nd/23rd The moon now heads towards the still very bright Mars just out of opposition.
So get out and see it asap as we start to move past it.
So get out and see it asap as we start to move past it.
The 26th is Mercury's time to reach it's greatest western elongation In the morning sky. If you want to see the elusive planet you’ll need to get up early before the sun rises and Be Careful Not To Look At The Sun! The planet will go from a thin crescent, to three quarters full at the end of the month. |
On the 28th Mars becomes stationary in the sky due to how Earth orbits planets. Mars seems to reverse briefly as we pass it and then moves back as we carry on. This is called retrograde and Mars will create what looks like a loop in the sky if recorded overnight An Awesome project for budding astrophotographers out there. |
And that’s this months highlights.
I'm pretty sure we will be out for the Meteor showers so keep an eye on the UK Astronomy FaceBook Group and website www.ukastronomy.org
As always, feel free to email U.K Astronomy at [email protected]