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Hey there! I'm Dave Hearn and I'm the Director of Kissimmee Park Observatory. In this Star
Hopping "Extra", we're going to take a break from our normal routine, and learn about the
different types of Star Clusters - all the different shapes and structures that these
collections of suns can have, and how they might appear in your telescope eyepiece. More
about all this great stuff right after this - stay tuned.
Hey Hello Hi and welcome to Episode 21 of Star Hopping with Kissimmee Park Observatory!
I'm Dave Hearn, and I'm just over the moon to be your host. In this series of programs
we'll show you the most beautiful sights in the night sky, and explain exactly how to
find them with your binoculars or telescope.
So this episode is a Star Hopping Extra - a discussion we can have while we wait for more
interesting targets to rise up from the Eastern horizon. As Spring is fast approaching, a
new type of deep sky object will replace the many galaxies that we have been seeing; These
are the most numerous type of deep sky object: Star Clusters. Clusters can appear in three
main configurations, and they are:
Open Clusters, Clusters with Nebulosity,
and Globular Clusters
Let’s start out with Open Clusters, which are definitely the most numerous deep sky
object up there, with nearly 1000 of these objects lying within our galaxy. An open cluster
can also be described as a Galactic Cluster. These are collections of stars ranging in
number from 10 or so individual stars to a mass of over a thousand stars, that were all
formed from the same molecular cloud. All the stars within these groupings have roughly
the same age, and can appear as loose collections or groupings, or appear so densely packed
that it is difficult to see black sky between the individual cluster members.
Open Clusters are classified by a somewhat complicated designation created by the astronomer
Robert Trumpler in 1930. The Trumpler scheme gives a cluster a three part designation,
with a Roman Numeral from I-IV indicating its concentration (from strongly to weakly
concentrated), an Arabic numeral from 1 to 3 indicating the range in brightness of members
(from small to large range), and the letters p, m or r to indication whether the cluster
is poor, medium or rich in stars. An 'n' is appended if the cluster lies within nebulosity.
Under the Trumpler scheme, the Pleiades are classified as I3rn (strongly concentrated
and richly populated with nebulosity present), while the nearby Hyades cluster in Taurus
are classified as II3m (more dispersed, and with fewer members).
Some great examples of the different kinds of loose Open Clusters are the Beehive Cluster
in Cancer, and M7 in Scorpius. Some examples of tighter open clusters are M35 in Gemini,
the Double Cluster in Perseus, and M11 in Scutum.
Moving along to a similar configuration of stars, a Cluster with Nebulosity is an open
cluster that is cradled within a stellar nursery of gas and dust, essentially a set of recently
born “baby” stars. These are some of the most photogenic targets in the heavens, as
they are very sparkly and colorful in images. Some of the popular nebulae with galactic
star clusters embedded within them are targets like the Pleiades, the Lagoon Nebula, the
Trifid Nebula, the North American Nebula, and the Star Queen Nebula. So are you completely
star struck yet? These are all gorgeous deep sky objects and are images taken at KPO.
The last type of star cluster also presents a very impressive and sometimes breathtaking
spectacle in the eyepiece, and are know as Globular Clusters. Globulars are spherical
collection of stars that orbit a galaxy’s core as a satellite, and there are over 150
of these objects within our Milky Way Galaxy. The stars in a Globular Cluster are very tightly
bound by gravity, which gives them their spherical shapes and relatively high stellar densities
toward their centers. Globulars are found in the halo of a galaxy, they generally contain
considerably more stars and are much older than the less dense galactic open clusters,
which are found in the galaxy’s disk. Globulars contain hundreds of thousands of stars within
them, and in the largest ones there are a million or more stars.
Globular clusters tend to all look very similar, but the distinctive differences are in the
way the outer stars spill into the blackness of space around them. The largest and most
famous Globular is Omega Centauri, lying in the constellation of Centaurus. The second
largest of these type of deep sky targets is 47 Tucana, and can be viewed only from
the southern hemisphere. Other amazing globulars are M13 in Hercules, M22 in Sagittarius, M15
in Pegasus, M3 in Bootes, and M4 in Scorpius.
If you lived on a planet orbiting a star within a globular cluster, the sky would most likely
be filled with tens of thousands of stars.
These Denizens of the Deep Sky provide an entertaining viewing experience, because the
popular ones are relatively bright, and can handle a lot of magnification to allow you
to zoom in to resolve individual stars near their core. I’ve heard many gasps of surprise
come from some of our more impressionable guests when they first view a globular cluster
through the KPO Reflector.
So let’s look back at what we’ve learned about the different types of Star Clusters.
First, and most common, is the Open Star Cluster, also known as a Galactic Cluster. These vary
greatly in star density, brightness, and color, and are generally have all of stars within
them being around the same age.
Second are Clusters with Nebulosity which are found in some of the most beautiful deep
sky objects in the sky, and often appear sparkly and colorful due to the bright stars and different
compositions of the nebula associated with them. Most often these are stellar birthplaces,
with the stars in these nebula all being very young indeed.
And Lastly are the impressive Globular Clusters, found in the outer halo of our galaxy, containing
hundreds of thousands or even millions of stars, tightly clustered together, bound by
gravity.
It’s amazing what wonderfully varied and unique configurations these groupings of stars
can take. They certainly provide variety and beauty to our interesting hobby of astronomy.
So that does it for this week’s episode. You can find the show notes on our website
at kpobservatory.org/SH021, where you can comment and leave any questions that you may
have. Thanks for joining us, and I’ll see you next week with more Star Hopping tips
and tricks.
I'm Cassie, and I hope you've enjoyed star hopping around the Milky Way. We'll continue
to bring you these video astronomy tutorials every week on Thursday, and in their podcast
format on Fridays. They will be designed to help you find deep sky objects that are up
in the sky at the time we post them on the Internet.
The reason we create these video and podcasts is to help beginning amateur astronomers learn
the sky and get more enjoyment out of their telescopes and astronomy in general. If you
have any requests or suggestions of potential targets in the night sky that you would like
to see us present, just let us know down in the comment section below, or on our website
blog.
Don’t miss our free Field Notes for this episode, basically the script of the show,
with all the images and start charts we use for our star hopping activities. You can get
them for free at kpobservatory.org/FieldNotes.
If this is the first time you’re checking out Star Hopping, and if you found this video
useful, please consider Subscribing to our Channel by clicking the Big Yellow Button
down there, click the Thumbs Up on the video, and please share this tutorial out to your
friends who like looking at stars. Also, as I just mentioned, please feel free to leave
any question or comment below, and we will be sure to respond quickly.
Also, please follow KPO on Facebook, where we post all of our astrophotos and keep everyone
informed about upcoming astronomical events. We'd love to hear from you to discuss all
this great stuff up in the sky.
All the links to these places including our website kpobservatory.org, can be found below
in the Episode Notes as well.
And finally, if you feel this video provides you value, and if you'd like to see more,
please consider supporting us on Patreon, where for a small amount per video, you can
support our efforts and let us make even more great astronomy tutorials like this one.
Well thanks again for watching, and we'll see you next time on Star Hopping with Kissimmee
Park Observatory.