Sandy Astronomical Society
Deep Sky monthly newsletter
March 2017
Welcome to my latest deep sky newsletter, this month sees the return of the monthly competition
and I intend to make available some great prizes for the lucky winners. However, before I move on I
must say that February was a total wash out for me, I only managed a handful of days at the
beginning of the month and then nothing, I really hope March has more to offer.
In this month’s newsletter, I shall have a look at the “Local group” of galaxies that of course includes
our own Milky way and then focus on the object of the month and then finally round off with the
competition question.
The Local Group of Galaxies
The Local Group is the galaxy group that includes the Milky Way. The Local Group comprises more
than 54 galaxies, most of them dwarf galaxies. Its gravitational centre is located somewhere
between the Milky Way and the Andromeda Galaxy. The Local Group covers a diameter of 10 Million
light years and the group itself is a part of the larger Virgo Supercluster, which in turn may be a part
of the Laniakea Supercluster.
The local group has three large galaxies, these being, Messier 31 The Andromeda Galaxy, Messier 33
The Triangulum Galaxy and of course our own Milky way galaxy. The Andromeda Galaxy and the
Milky way are the two largest of them and each has its own system of satellite galaxies. We shall
have a look in closer detail at these two galaxies and their satellites.
The Milky way system
The Milky way galaxy is what is known as a barred spiral, this is a galaxy that has the distinct spiral
arms but with a central bar running either side of the central nucleus. The image below is an
interpretation of what our galaxy may look like.
Our own galaxy has a number of associated satellite galaxies, the two better known ones are the
Large Magellanic Cloud and the Small Magellanic Cloud, these are classified as irregular galaxies and
unfortunately can only be viewed from the Southern Hemisphere. The image below is of both
galaxies
In close up these two galaxies contain a wealth of interesting detail, the image below is of the Large
Magellanic cloud, the areas indicated are regions of star formation like our own Orion Nebula. These
two galaxies are approximately 160,000 light years from our own Milky way.
The Messier 31 (Andromeda galaxy) system
The Andromeda galaxy is a spiral galaxy and is one that is viewed at a slightly tilted angle so the full
splendour of the spiral arms cannot be seen, however, the nucleus of the galaxy can be clearly seen
and long exposure photographs show the dust lanes. Our very own Andrew Knight has captured a
lovely image of this galaxy, which is reproduced below. You can clearly see the dust lanes and 2 of
the galaxy’s satellites. This galaxy is approximately 2,500,000 light years from our own Milky way
galaxy
Like the Milky way system Messier 31 also has a number of satellite galaxies. The two better known
are also contained within Messier’s catalogue and are known as Messiers 32 and 110, both are
elliptical galaxies and as such contain no spiral arms. The image below shows a close up of one of
these galaxies.
Messier 33 The Triangulum galaxy
It has been suggested that the third largest member of the local group, Messier 33 is a satellite of
the Andromeda galaxy, this is a nice galaxy, however, it can be tricky to spot. The two images below
are of Messier 33, one in monochrome and the other in negative. As you can see this galaxy is also a
spiral galaxy and lies approximately 2,400,000 light years from the Milky way.
Finally, to put everything into perspective this graphic shows the enormity of the universe and our
place within it
Not wishing alarm anyone but it is predicted that in about 4 billion years’ time a collision between
the two largest galaxies in the Local Group; the Milky Way and the Andromeda Galaxy will occur.
The stars involved are sufficiently far apart that it is improbable that any of them will individually
collide, however, some stars will be ejected from the resulting galaxy.
This link demonstrates what is predicted to occur.
https://upload.wikimedia.org/wikipedia/commons/transcoded/d/da/Andromeda_and_Milky_Way_
collision.ogv/Andromeda_and_Milky_Way_collision.ogv.240p.webm
Object of the month
This month’s object is an often overlooked planetary nebula in Charles Messier’s catalogue, it is over
shadowed by its more famous big brother that being Messier 27 The Dumbbell Nebula. This object
has been given the subservient name of the Little Dumbbell and can be found in the constellation of
Perseus, it is the 76th object listed in Messier’s catalogue.
Where can I find it?
Messier 76 can be found under the W
of the constellation of Cassiopeia, it
does require a telescope as it has an
apparent magnitude of +10.1 so is not
visible to the naked eye. It is, as
indicated, a Planetary nebula which lies
at a distance of 2,500 light years from
the Sun.
What does it look like?
This is a sketch of The Little Dumbbell
I have managed to image this object on several occasions and here are some of them
Competition time
As indicated earlier, this month sees the return of the deep sky competition and up for grabs is this
astronomy book, it is an excellent book with a wealth of information.
With every competition comes a question and this month’s question is.
Mark Thompson has appeared on many TV shows including BBC’s Stargazing live, which will be
aired later this month. In what year was the first Stargazing live aired?
Please send your entries to [email protected] by 31st March 2017. I will announce the
winner in the April edition of the deep sky newsletter. Good luck.
Finally, if you have any images you would like me to showcase in future newsletters please send
them to me at the same e mail address.
Here’s to clear skies and all the best until next month.
Best wishes
Ian
Ian Papworth