The Night Sky

Due to the observatory being a small enclosed space, unfortunately it will not be open for this event. However, the volunteers who support events at the observatory (usually scheduled here, https://www.facebook.com/groups/1576662229235265), will set up telescopes in the field near the observatory to view the wonders of the heavens on October first with a cloud date of the second. These telescopes will provide views as good as the scope in the observatory of many celestial objects.  Beginning at 7 PM, the scopes will be aimed at the most interesting of planets, Jupiter with its moon and Saturn featuring its rings. They will be visible most of the event, but as the sky darkens, we will also target what are known as deep sky objects, because they are much farther away than anything in our solar system.

 

The first of these will be a selection of double stars; one being the well-known Albireo, which features components of contrasting colors and is located at the bottom of the Northern Cross in the constellation Cygnus the Swan.  It takes 430 years for the light from Albireo to reach us, compared to 1.3 hours from Saturn.  Deep.

 

Going deeper into the summer Milky Way, there are many star clusters and nebulae for our viewing pleasure.  The first object we come to is the Dumbbell nebula, a planetary nebula which resulted from the collapse of a sun-like star into a white dwarf.  A cloud of gas surrounding the white dwarf is ionized which allows us to see it, from a distance that happens to be close to double that of Albireo.  Next is another planetary, the Ring, which looks like a small ring or donut or bagel, your choice.  Its light arrives after travelling for 2550 years. 

 

At about the same distance as the Ring lies a special type of nebula, a supernova remnant.  The Veil Nebula is what remains of a star ten times larger than the sun, a star that collapsed and exploded 10,000 to 20,000 years ago when it ran out of nuclear fuel.  The blast was so violent that, even from that great distance, it would have been brighter than Venus and therefore visible in the daytime.  The important thing about supernovae is that without them, we wouldn’t be here.  Not this one of course, since the ones that created all the atoms heavier than hydrogen that make up our bodies had to have exploded more than 4.5 billion years ago.  As Carl said, “We are all star stuff.”

 

Next up, open star clusters, groups of stars that formed at the same time in a large cloud of gas and dust known as diffuse nebula.  (The best example of a diffuse nebula is the Orion Nebula, but that has to wait until a winter observing session.)  These clusters are comprised of young stars because gravitational forces eventually tear them apart.  Billions of years ago the Sun was a member of an open cluster, but its companions are now spread far and wide. 

 

The first open cluster, the Wild Duck cluster, is a small one but has 100 stars packed in that area.  Those stars are 6200 light years away.  The next cluster is very large, in fact it is two clusters side by side and thus known as the Double Cluster.  Even though a little farther away than the Wild Duck, 7500 light years, both are larger with brighter stars, approximately 200 in each.  And the stars are very young, only about 12 million years; they are babies compared to the Sun’s 4.5 billion years!

 

Now we jump to the edge of our Milky Way galaxy, to a globular cluster.  Unlike the open clusters which are in the plane of the Milky Way, which is what we see high in the sky on late summer evenings, the globulars form a halo around our galaxy, are very old and comprised of as many as half a million stars.  Our globular target will be the Great Hercules Cluster, at a distance of 25,000 light years and boasting several hundred thousand stars.  At that distance and all those stars, it appears as a solid ball of light, but at higher powers it will appear granular which indicates it is individual stars, not a nebula.

 

Finally, we leave the Milky Way behind and go to the nearest large galaxy, the Andromeda at a distance of 2.5 MILLION light years, and that’s the close one.  In the spring we could go to many more millions of light years.  Back to Andromeda, it is similar to our galaxy, a spiral, somewhat edge on from our perspective but larger.  The Milky Way has about 100 billion stars, Andromeda perhaps 10 times that many!  However, at that distance it is not possible to resolve them individually so it looks like a large nebula, which is what galaxies were called for many years, until telescopes were large enough to show individual stars.

 

The observatory is behind the portable class rooms, which are just past the entrance to the large parking lot on Roberts Road.  Park in front of the portables or beside them; please do not drive past them and please do not bring white flashlights onto the observing area.  Use something red to cover white lights or wait a few minutes for your eyes to adapt to the darkness if you arrive late.  Most importantly, with covid not going away, please wear a mask.  Thank you.

 

 

Tom Hoffelder