Category: Other Astronomy Newsletters

November, 2009

By Tom Koonce

Antelope Valley Astronomy Club, Inc.

Lancaster, California

“The bigger they are, the harder they fall…â€?  This is certainly true of stars.  When single stars condense from a star forming nebula, their life history is pre-written based upon their initial mass and the cloud’s composition.  High mass stars burn very hot, have very short stellar lifetimes then explode in spectacular Supernovae, forming either Neutron Stars or Black Holes.  On the other end of the mass scale, low mass single stars have relatively cool temperatures, but live extremely long lifetimes and may radiate dimly for many, many billions of years

Over time, higher density regions within giant nebulae like the Orion Nebula or the Eagle Nebula begin to contract gravitationally, and as they do, the cloud rotates.  As the gas contracts and rotates faster, the gas begins to heat up to become a Protostar.  Once its temperature reaches approximately 15,000,000 Celsius, nuclear fusion initiates in the cloud’s center causing the Protostar to begin to radiate brightly.   The smallest stellar objects that form in the star forming regions are called Sub-Stellar Objects.  These form with masses between 0.013 and 0.08 times the mass of our own Sun (our Sun = one solar mass).  These stars radiate briefly as a dim star, but gradually collapse, cool as they evolve further into Brown Dwarf stars.  Eventually the Brown Dwarf will cool further and it will cease radiating at all.

The stars known as “Red Dwarfâ€? stars have between 0.08 and 0.4 solar masses when they form.  These are the most common type of stars in the observable universe and have lifetimes longer than 13 billion years.  As these small, long living stars eventually cool, they die and become Black Dwarf stars.

Stars approximately the size of our Sun with 0.4 to 8 solar masses are called “Intermediateâ€? stars and will swell into Red Giant stars as their fuel is expended.  Eventually, these stars will end their lives as White Dwarf stars.

Nebulae and stars are typically composed of 74% hydrogen, 25% helium and 1% everything else in the periodic table by mass.  A star’s initial mass is determined by the amount of material available within the nebula from which the star forms.  Very dense nebulae can produce the most massive stars – true giants with 8 times (or greater than) our Sun’s mass.  Those stars with between 8 and 25 solar masses will expand into Super Giant stars then explode as supernovae and end their lives as Neutron Stars; those stars with greater than 25 solar masses will expand into Super Giant stars, explode as supernovae and become Black Holes.  It isn’t known what the upper limit is to a star’s initial mass is, but in the early 1990’s, a star nicknamed the “Pistol Starâ€? was discovered by the Hubble Space Telescope near the center of the Milky Way galaxy with a mass of 100 solar masses and a radius of 100 million miles, comparable to the Earth-Sun distance of 93 million miles.  The Pistol Star is called a Blue Hyper Giant and is so hot that its gravity can’t stabilize it and it is expected to go supernova within only 1 to 3 million years.  A great deal of gas and matter is expelled during these supernovae explosions which then give rise to future generations of stars, repeating the cycle of stellar birth.

Smaller stars burn dimly, but may burn for billions and billions of years.  Giant stars burn with incredible intensity, but go through their hydrogen and helium fuel in as little as millions of years, and then end their lives in dramatic supernovae explosions.  I can think of a few analogous Hollywood situations…but that’s for another type of “Starâ€? article altogether.

References and image credit: NASA StarChild initiative, NASA Hubble Space Telescope, Wikipedia.

Other Newsletter inserts:

The zodiac names we use today are actually the names our ancestors gave to special star groups known as constellations. How many of the ancient constellation names can you correctly identify? Place the constellation’s letter on the line next to its description.

A. Gemini	_____ The Water Carrier
B. Cancer	_____ The Crab
C. Aries	_____ The Goat
D. Libra	_____ The Twins
E. Ursa Major	_____ The Dragon
F. Capricornus	_____ The Winged Horse
G. Leo	_____ The Scorpion
H. Draco	_____ The Bull
I. Pegasus	_____ The Archer
J. Taurus	_____ The Fish
K. Pisces	_____ The Hunter
L. Aquarius	_____ The Lion
M. Sagittarius	_____ The Scales
N. Scorpius	_____ The Ram
O. Orion	_____ The Great Bear

STAR SIGNS ANSWER KEY

A. Gemini – The Twins

B. Cancer – The Crab

C. Aries – The Ram

D. Libra – The Scales

E. Ursa Major – The Great Bear

F. Capricornus – The Goat

G. Leo – The Lion

H. Draco – The Dragon

I. Pegasus – The Winged Horse

J. Taurus – The Bull

K. Pisces – The Fish

L. Aquarius – The Water Carrier

M. Sagittarius – The Archer

N. Scorpius – The Scorpion

O. Orion – The Hunter

How many star terms can you find hidden in the puzzle below? Words may be written

horizontally, vertically, diagonally, left to right or right to left. Circle each word as you

find it.

Star Terms:

hot, atoms, nebula, supernova, neutron, red giant, cycle, sphere, energy, fusion,

core, galaxy, hydrogen, evolve, gas, cloud, glow, x-ray.

N	G	F	C	E	L	S	I	U	A	A
E	N	T	U	L	S	D	W	C	I	L
B	O	N	A	S	S	P	E	O	G	U
U	R	A	I	H	I	M	H	R	D	B
L	T	I	G	Y	E	O	O	E	E	E
E	U	G	A	D	T	V	N	T	R	N
L	E	D	L	R	O	E	L	W	A	E
C	N	E	A	O	R	D	U	O	L	C
Y	A	R	X	G	A	S	Y	L	V	U
C	T	O	Y	E	N	A	I	G	X	E
A	A	V	O	N	R	E	P	U	S	N

When I first heard about the Galileoscope project which seeks to get a ‘good’ telescope into people’s hands for $20, I was, to say the least, a bit dubious about their claims.  I wasn’t expecting much, but for $20 and an acknowledged addiction to telescopes, I took a chance and ordered one from their website:   https://www.galileoscope.org/gs/

The Galileoscope™: An IYA2009 Cornerstone Project

The Galileoscope™ is a high-quality, low-cost telescope kit developed for the International Year of Astronomy 2009 by a team of leading astronomers, optical engineers, and science educators. No matter where you live, with this easy-to-assemble, 50-mm (2-inch) diameter, 25- to 50-power achromatic refractor, you can see the celestial wonders that Galileo Galilei first glimpsed 400 years ago and that still delight stargazers today. These include lunar craters and mountains, four moons circling Jupiter, the phases of Venus, Saturn’s rings, and countless stars invisible to the unaided eye. The Galileoscope costs just US$20 each plus shipping for 1 to 99 units.

Production and distribution are managed by Galileoscope, LLC, a new company established by the Galileoscope project team with the express purpose of ensuring delivery of the best possible product at the lowest possible price.

Sounds great right?  But we all know that “talk is cheap.â€?  Well, I am now a believer in this product!  I ordered my Galileoscope in early March and didn’t receive delivery until mid July.   But as I said, I wasn’t expecting much for my $20, and the delay turned out to be caused by the sheer number of orders they had.

The telescope arrived in kit form, and thanks to outstanding online directions, it only took 30 minutes from the box to mounting the completed two inch refractor, with two 1 ¼ inch eyepieces being mounted onto my existing photo tripod!  It went together easily and probably would for ages 8 and up with adult supervision and for ages 12 and up, building it by themselves.  Also, despite the name, the telescope is NOT a model of Galileo’s telescope.  He would have loved to have an instrument of this quality and capability!

You have to supply your own mount for the scope, but the scope has a standard tripod mount thread on it and the instructions describe how to make a poor-man’s cardboard box mount that would work fine.  I mounted mine on an inexpensive photo tripod  I already had.

The two inch, two element objective lens produces well color-corrected imagery of the Moon and Venus, and the eyepieces produce 18X and 25X images when used individually or by combing these into a Barlow arrangement, you can get up to 50X.  I have left it at 25X.  First light for the scope was a daylight terrestrial object, the top of a power pole located 1 mile from my house that I frequently use to sight in telescopes and finder scopes.  I’m glad I did this during the day because I was able to get familiar with the drawtube focusing of the Galileoscope and get focus set close to infinity before I used it later that night.  The daylight images of the mountains we very sharp, but I was trying to not be too anxious in case the night-time views were less spectacular.  The first object I looked at later in the evening was the gibbous Moon.  Wow!  It was tack sharp and I could see all details which I wasn’t expecting to see for a $15 dollar telescope.  I could also see subtle shade differences and crater details that made me smile.  I remembered the views through my very first Tasco two inch refractor with its “75X Zoomâ€? eyepiece that had to cost $50 in the 1960’s.  You probably had similar experiences with fuzzy imagery and chromatic aberration that made looking at the Moon poorly surreal experience.  The Galileoscope is a breath of fresh air.

What can be seen?  After studying the Moon with both eyepieces, I decided I liked the 25X view better, made sure the focus was still sharp before I pointed it at Jupiter, about thirty degrees above the eastern horizon.  The very first thing I noticed about Jupiter were the four sharply focused moons, one just emerging from behind the planet.  I guess I wasn’t expecting to even see the Moons very well, not the two primary and one set of secondary bands on the planet.  But there they were!  I can imagine the inspiration that the Galileoscope will provide youngsters around the world.  I observed the beautiful gold and blue double star Albireo at the head of Cygnus next.  Great color, nice view.  The globular cluster M13 was a nice fuzz ball and I could tell it was a globular and not a comet.  The next morning I got up at 4:30 am to point the scope at the Orion Nebula and was not disappointed.  I resolved everything I expected a two inch telescope to reveal, and the contrast was pretty darn good!  I had to kneel on the ground while looked nearly overhead at the nice view of the Andromeda Galaxy M31, ($20 folks!  This scope is sooo cool!), then I got the entire Pleiades cluster in the field of view.  I saved Venus for last, since it is typically a big problem for inexpensive scopes because Venus appears small, white and very bright.  I immediately noted two things.  I was looking at a gibbous Venus and that I saw an afterimage from internal reflection between the front two elements and a faint afterimage reflection between the two elements of the eyepiece.  The front reflection was a bit distracting, but not overwhelmingly so.

The Moon, major planets, the brighter deep sky objects – all for one twenty dollar bill.  Better yet, buy one for yourself and in the spirit of the International Year of Astronomy 2009, buy a second scope for just $12.50 to donate to someone around the world who otherwise would never get an opportunity to see the sky in such detail.