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Eclipse Newsletter ECLIPSE NEWSLETTER The Eclipse Newsletter is dedicated to increasing the knowledge of Astronomy, Astrophysics, Cosmology and related subjects. VOLUME 3 NUMBER 2 MARCH – APRIL 2019 PLEASE SEND ALL PHOTOS, QUESTIONS AND REQUST FOR ARTICLES TO [email protected] Beginning in this issue, if it is in green, my hope is you will do some research. I will continue to use hyperlinks. Just swipe, right click, open hyperlink. 1 CONTENTS: CONSTELLATION CANCER WHAT ARE THE MESSIER OBJECTS? MESSIER OBJECT NUMBER 17 THE OMEGA NEBULA WHAT IS THE LIFECYCLE OF A STAR? PART 2. ASTROBIOLOGY MORE ON PLANET NINE. NEUTRINOS MARS ROVER OPPORTUNITY IS DEAD. MCAO PUBLIC NIGHTS AND FAMILY NIGHTS. HOW TO FIND CONSTELLATIONS UPCOMING STAR PARTIES HYPERLINKS IN BLUE NORMALLY - DEFINITIONS IN RED DO THE RESEARCH. YOU WILL LEARN MORE THAN IF I TELL YOU THE DEFINITION. 2 CONSTELLATION CANCER – THE CRAB 3 Cancer constellation is located in the northern sky. Its name means “the crab” in Latin. Cancer is the faintest of the 12 zodiac constellations. The constellation was first catalogued by the Greek astronomer Ptolemy in the 2nd century. Cancer contains a number of famous deep sky objects, among them the open cluster Praesepe, also known as the Beehive Cluster (Messier 44), the open cluster Messier 67, and the interacting spiral galaxies NGC 2535 and NGC 2536. Cancer is the 31st largest constellation in the sky, occupying an area of 506 square degrees. It lies in the second quadrant of the northern hemisphere (NQ2) and can be seen at latitudes between +90° and -60°. The neighboring constellations are Canis Minor, Gemini, Hydra, Leo, Leo Minor, and Lynx. Cancer belongs to the Zodiac family of constellations, along with Aries, Taurus, Gemini, Leo, Virgo, Libra, Scorpius, Sagittarius, Capricornus, Aquarius, and Pisces. Cancer contains two Messier objects – the Beehive Cluster (M44, NGC 2632) and M67 (NGC 2682) – and has two stars with known planets. The brightest star in the constellation is Al Tarf, Beta Cancri. The Delta Cancrids are the only meteor shower associated with the constellation. WHAT ARE THE MESSIER OBJECTS? The Messier objects are a set of over 100 astronomical objects first listed by French astronomer Charles Messier in 1771.[1] Messier was a comet hunter, and was frustrated by objects which resembled but were not comets, so he compiled a list of them,[2] in collaboration with his assistant Pierre Méchain, to avoid wasting time on them. The number of objects in the lists he published reached 103, but a few more thought to have been observed by Messier have been added by other astronomers over the years. For a list of Messier objects: https://en.wikipedia.org/wiki/List of Messier objects The Omega Nebula, also known as the Swan Nebula, Lobster, and the Horseshoe Nebula Messier 17. 4 The above is a sketch from the Naval Observatory in 1875 This is a photo taken recently of the Omega Nebula. If you study this photo long enough, you will start to see the various parts of the above sketch. 5 M17 Omega Nebula is located upper left hand corner. The Omega Nebula (nicknamed the Swan Nebula) is an H II region in the constellation of Sagittarius. It is about 5,500 light-years away from Earth. It was discovered by Philippe Loys de Chéseaux in 1745 by Charles Messier added it to his catalog as M17 on the night of 3 June 1764.[2] M17 has more name’s than any other deep-sky object. In addition to the Omega Nebula and Swan Nebula, it is also called the Horseshoe Nebula, the Checkmark Nebula and the Lobster Nebula. Omega can be seen through binoculars or a small telescope 6 WHAT IS THE LIFECYCLE OF A STAR? PART 2 What causes a Supernova and why does it come apart? There are currently two explanations involving theoretical mechanisms that are related to the two ways in which stars die. Stars cannot shine forever for the simple reason that their energy supply— nuclear burning—is finite. What happens to stars once they exhaust their nuclear fuel (mainly hydrogen) is believed to depend crucially on their mass. One of the most important theoretical discoveries in astrophysics is that a critical mass exists above which stars cannot 7 sustain themselves against their own gravitational pull without a continuous supply of energy. The two types of star endings depend on whether their mass is above or below this critical mass, which is called the Chandrasekhar mass limit, named after Subrahmanyan Chandrasekhar one of its discoverers. If, by the time a star exhausts its fuel, it has a mass greater than this limit, the core of the star cannot sustain itself and collapses. A huge amount of energy is released when the core collapses to the tiny size of a few kilometers, becoming a black hole or a neutron star. While most of this energy is emitted in invisible neutrinos (See topic below), a small fraction of this energy ejects the outer parts of the star, creating an explosion sufficient to produce a supernova. Such a theoretical event is called a core-collapse supernova. Just before the collapse of a star, you can see Fe, O, Ne and C have developed. He and H now occupy the outer edges. There is another type of demise our sun may encounter. Stars vary in size, mass and temperature, some are smaller than the Sun, while some are thousands of times larger; temperatures can range from 3,000°C to 50,000°C. The energy produced by stars is by nuclear fusion in the stars' core. Stars that are fusing hydrogen into helium, they are known as 'main sequence' stars. Astronomers believe, over 90% of the stars in the observable universe are in main sequence. Our Star, the Sun is an example. More massive stars tend to have higher core temperatures than smaller stars, as a consequence of which large stars exhaust the hydrogen fuel in the core quickly, whereas, small stars burn it more slowly. When a small star eventually exhausts all the hydrogen fuel, the fusion stops, but there is a lot of helium in the core; the core temperature drops, and so it expands, and starts to fuse helium into Carbon even though this process generates a little less energy than fusing hydrogen to helium. Because the temperature is low, it appears red in color - and hence the term 'red giant'. Eventually, when the helium fuel is also exhausted, only a core of carbon remains - but it is not massive enough to start fusion so it remains as a glowing white-hot sphere of carbon - a 'white dwarf'. Stars that are less than one solar mass are too small and cool even to fuse helium to carbon, so they will end up as a white dwarf made of helium. More massive stars are different. If a star about 8 to 10 times as massive as the Sun exhausts the hydrogen, it continues to fuse helium into carbon, and then carbon to neon, neon to oxygen, oxygen to silicon, and finally silicon to iron. 8 Image courtesy of: google images Take note of Jupiter’s orbit. At this point in time, Earth’s orbit is well within the outer edge of the supergiant star. When a main sequence star runs out of hydrogen atoms in its core, the star may begin to fuse helium atoms. This causes a change in heat and pressure which in turn may cause the star to expand many times its original size, creating a supergiant. Once the star reaches the iron stage, it’s doomed. The star has reached the end of its life. Iron cannot be fused into anything heavier because of the huge amounts of energy and pressure required to fuse iron atoms. Suddenly, the Star is no longer in equilibrium, it becomes unstable and collapses in on itself and it casts off its gaseous outer shells in one big explosion, sparking a supernova. What is left behind after a supernova explosion may be a (1) neutron star - if the mass of the core is between 1.4 and 3 solar masses, or (2) a black hole - if the mass is 3 or more solar masses. According to NASA, supernovae are “the largest explosion that takes place in space.” On average, a supernova occurs about once every 50 years in a galaxy like the Milky Way. Taken the observable universe as a whole, a star explodes every second somewhere in the universe. THE LIFE CYCLE OF A STAR PART 3 WHAT HAPPENS AFTER THE SUPERNOVE EXPLODES WILL BE IN THE MAY JUNE ISSUE. 9 ASTROBIOLOGY From astrobiology.com Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe: extraterrestrial life and life on Earth. Astrobiology addresses the question of whether life exists beyond Earth, and how humans can detect it if it does. Astrobiology makes use of physics, chemistry, astronomy, biology, molecular biology, ecology, planetary science, geography, and geology to investigate the possibility of life on other worlds and help recognize biospheres that might be different from that on Earth. Astrobiology seeks to understand the origin of the building blocks of life, how these biogenic compounds combine to create life, how life affects - and is affected by the environment from which it arose, and finally, whether and how life expands beyond its planet of origin. None of these questions is by any means new - but for the first time since they were posed, these questions may now be answerable. Astrobiology seeks to provide a philosophical and programmatic underpinning whereby life's place in the universe can be explored - at levels of inter-related complexity ranging from molecular to galactic.
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