This picture of the Crab Nebula is courtesy of NASA/JPL
Hi there, my night sky astro-buddies!
As we all know, the weather has been typical for late-October, with cold temps, rain, a bit of snow and wind, punctuated by spectacularly beautiful days.
Since our night sky viewing days are limited by inclement weather, it makes us really appreciate the clear nights when the sky puts on a great show.
By the way, the Moon was Full on Oct. 27.
Also, don’t forget to move your clocks back an hour the morning of Nov. 1 for the return to Eastern Standard Time.
As the Moon starts to diminish in the weeks ahead, spend some time orienting yourself with the night sky, using your navigation skills and the names of the larger, more prominent constellations. You can even go ahead and memorize the names of the brighter stars. Try and knowing the night sky well enough that you can easily tell the cardinal direction you are looking at (East, West, North or South).
The constellation of Taurus rises in the east around 9 p.m. and is much higher in the sky by midnight, and is easy to find. The “eyes” of the Bull are dominated by two bright stars—the red star Aldebaran is the eastern most one. The constellation of the Pleiades (the “Seven Sisters”) is directly above Taurus in the eastern sky, so it’s an easy constellation to find.
If you follow the stars out from Aldebaran to the last bright star, you have reached the “tip” of the left horn. Very close to it is the deep sky object M 1.
If you might have forgotten, a sky object with a letter “M” in front of a number stands for a Messier object.
Charles Messier was an 18th century comet hunter who did not want to confuse his observations with these little nebulous patches he was able to observe through his primitive telescope. His compiled list is of 110 deep sky objects, almost all of which are visible with good binoculars or a small telescope.
M1, the first in his list, is the remnant of a supernova explosion which was first seen and recorded here on Earth by the Chinese in 1054 AD.
They politely called it a “guest star”, and it was so bright that it was visible during the day! After a few months it faded away, but the remnants of this titanic explosion are visible with a telescope. It is expanding at a thousand kilometers a second!
A supernova is the violent death of a large, hot and massive star. In order for a star to be an eventual supernova candidate, it must be at least eight times more massive than our Sun. As you know, the Sun shines via a thermonuclear reaction—converting enormous amounts of hydrogen into helium every second. This is exactly how a hydrogen bomb works.
The Sun has enough hydrogen fuel to do this for several billion more years. At that point it will begin to swell, using up whatever elements remain until it collapses to become a white dwarf star.
In a supernova star, the star burns much hotter and will use its fuel up rapidly, sometimes within a few hundred million years. The gravity is so strong, only the fusion reactions trying to explode outwards keep things “in balance” and the star intact.
When it runs out of hydrogen, it starts burning helium and this undergoes nuclear fusion to form carbon. This process continues, fusing heavier and heavier elements, until the core starts to fuse iron. Once this reaction starts, nuclear fusion stops instantly!
At this point, the star’s core then has no resistance to the force of gravity, and once it starts to contract, a very rapid collapse and then violent rebound will take place (in less than a second!).
The protons and electrons combine to give a core composed of neutrons and a vast amount of energy is released as the star explodes. This energy is sufficient to blow away all the outer parts of the star in an incredibly violent blast and the star becomes a supernova. The light of this one star at its peak during the explosion is then about as bright as that from all the other 100,000,000,000 stars in the host galaxy.
During the blast, the heat and energy are so intense (literally billions of degrees), that the heavier elements can form (and the only time they can form) by fusion—silver, gold, lead—all the way up through the table of elements to uranium, etc. Thus, the violent death of a large star is also a creative force by seeding the galaxy with the heavy elements.
The gold and silver jewelry we wear, the iron in our red blood cells and the calcium in our bones, the aluminum foil we use in the kitchen—all were forged in the crucible of high energy thermonuclear reactions and a long past but incredibly violent supernova explosion. This means that we are all intimately connected to each other and with the cosmos, as we are all made from the same star stuff.
The next meeting of NOMAC (Northern Michigan Astronomy Club) is Nov. 12 on the campus of NCMC. Check out the details at our website www.nomac.net. The talk will be on “How Stellar Nuclear Fusion Works.” And so, fellow children of the cosmos, hope for clear skies and keep looking up! Pictured in the center of the story is M1, the Crab Nebula. Photo is courtesy of NASA/JPL