When NASA plans a mission to explore the distant planets, moons, and comets that are orbiting our solar system, one of the first considerations is the type of power source needed by the spacecraft that will be making the journey.
Visiting Mercury or Venus, for instance, simply requires a solar panel to convert energy from the sun into electricity. But what about missions to Mars and beyond, to explore the frozen outer planets and their icy moons?
A radioisotope thermoelectric generator – an RTG – is just what it’s name says it is; a generator that converts heat into electricity using a radioactive material as a fuel source.
These “nuclear batteries” were invented in the 1960’s and have been safely powering unmanned space exploration for 50 years.
A chemical element is a substance, an atom, that exists in it’s simplest form and can be identified by it’s protons, electrons, and neutrons. A stable atom with a neutral charge is one that has the same number of protons and electrons. The number of protons in the nucleus is constant for a particular element, but when there are a varying number of neutrons, these are considered isotopes of that element.
Elements such as copper, lead, and gold were “discovered” thousands of years ago but in the past 150 years, scientists have organized the periodic table to include 94 naturally occurring elements and 24 synthetic ones.
As the atom of a radioactive element seeks to stabilize itself, it ejects particles from within the nucleus out into the atmosphere
Some atoms with an excess of protons or neutrons are said to be radioactive.
As the atom of a radioactive element seeks to stabilize itself, it ejects particles from within the nucleus out into the atmosphere in the form of alpha radiation, dangerous beta radiation or deadly gamma radiation.
The nuclear fuel used in most RTG’s is Plutonium-238. This element is synthesized by “bombarding” an atom of Uranium-238 with an isotope of Hydrogen to create an isotope of Plutonium.
Scientists have found that Plutonium-238 is the safest one for use in an RTG because it emits only alpha particles at a slow, steady pace for a long duration. These particles are emitted as heat that is converted into electricity within the generator.
Zodiac Sign: Jan 22 – Feb 21
When our human ancestors studied the night sky, it didn’t happen like you might guess. While we have to drive away from bright city lights and utilize expensive viewing equipment, they were noticing that – from one year to the next – there were patterns in the sky around them that coincided with the timing of the seasons. They were so amazed they began building monuments that aligned with the brightest stars.
Historians are finding new and much more decisive evidence that these early societies also developed an in-depth knowledge and practical uses of the sun, moon, and planets. They did this conceptually, since the observations of the stars pre-dates written books or possibly even a unifying language. They divided the night sky into twelve sections, what became known as the signs of the Zodiac. Despite the fact that there are myths associated with the Zodiac constellations originating in Rome, modern-day astrology and astronomy happen to be dissimilar.
Within the boundaries of Aquarius are luminous star clusters and colorful planetary nebulae.
Star Clusters
Open star clusters have been studied for centuries, mostly because they are so bright they can be seen from earth with even low-powered viewing equipment.
"Planetary" Nebula
As a star evolves, moving through it’s life span over a course of billions of years, it’s intensity and even it’s size changes. A nebula, or cloud of chemicals, is emitted from a star as it ages from a “giant” into a cooler, neutron star. The end result of this is called a “planetary nebula,” as astronomers in the 1780’s believed that these mysterious deep-sky objects resembled small, colorful planets.
The Saturn Nebula glows green, blue and yellow at a distance of 5,200 light-years from earth. Astronomers postulate that it began as a white or a blue main-sequence star before it began to evolve and release elements into the surrounding atmosphere. This colorful nebula was discovered in the 1780’s.
The age of the Helix Nebula is thought to be 10,500 years, meaning that an astronomer might tell you that this planetary nebula is practically in it’s infancy. This cloud of stellar dust is only 700 light years from earth.
The heart starts to beat practically at conception and continues it’s life-sustaining role for a hundred years or longer. It’s size and mass are proportional to each person, our hearts being roughly the size of our clenched fist.
This durable muscle powers the circulatory system that pumps blood into the lungs, exchanging CO2 for oxygen.
The structure of the heart isn’t complicated … a right and left atria, a right and left ventricle, four valves, and the surrounding arteries and veins of the circulatory system
The heart is located at the T5-T8 vertebrae of the spinal cord behind the sternum, and it’s monitored by the parts of the brain stem that control the involuntary workings of the respiratory, digestive, and lymphatic systems.
As the heart is pounding away and keeping us healthy its protected by the sternum and rib cage and encased within the pericardial sac. The outside of the double-layered pericardium is a tough membrane attached to the inner wall of the chest cavity to prevent the heart from shifting around. The inner pericardium is connected to the heart by a thin layer of connective tissue and fat. In between is the pericardial fluid that forms a cushion to lubricate the heart and prevent infection.
As health care professionals are quick to remind you, a healthy blood pressure is around 120/80.
High blood pressure, also known as hypertension, often has no symptoms, yet it could potentially weaken the arteries of the circulatory system and cause damage to the heart, brain, and kidneys over a span of many, many years.
Nearly 1 in 3 adults in America are taking medications and modifying their diet and exercise habits to keep their blood pressure low. Medications have different effects on blood pressure, but they’re tasked with slowing the heart to prevent it from being overworked, while keeping the arteries and veins open so blood can flow more easily.
A blood pressure reading is a measure of whether our hearts are pumping so forcefully that permanent damage could occur
A blood pressure reading is taken with a blood pressure cuff (either manually or with a computerized monitor) by constricting the brachial artery in the upper arm to the point when all pulse sounds disappear, and then slowly releasing pressure.
When the force of the bloodstream pushes blood through the constricted artery, a “thumping” sound is heard. This is the systolic pressure (when the heart is beating).
As the blood pressure cuff slowly releases pressure at a rate of approximately 2-3 mmHg per second, the sounds within the artery become quieter and then disappear completely, which is the diastolic pressure (when the heart is at rest).
