The Universe Beyond the Solar System: Facts, Photos, and a Poem
Mysteries of the Universe
The universe is a mysterious place. Astronomers say that about seventy percent of its total mass and energy exists as dark energy, which is believed to be responsible for the universe’s accelerating expansion. Another twenty-five percent is made of invisible dark matter. This type of matter does have mass but doesn’t reflect light and can’t be seen. Less than five percent of the universe consists of the “regular” matter that we can see.
Very little is known about dark energy and dark matter, despite the fact that they are believed to be so common in the universe. They are strange and intriguing concepts. An understanding of their nature would be a huge advance in our knowledge.
Scientists have other puzzling ideas about space. For example, the evidence indicates that the universe is expanding, but some researchers say that it may also be infinite. How do these two ideas fit together? Another fascinating idea proposed by some researchers is that other universes exist in addition to our own, forming a multiverse. Some scientists also suggest that our universe was produced as a bud or branch from another universe and in a similar way is producing other universes. Every new theory or new discovery in astronomy is exciting.
The space between stars is not a vacuum. It contains a thin mixture of gas and dust known as the interstellar medium or ISM. The main component of the ISM is hydrogen, which exists in a molecular, atomic, or ionic form, but other substances are also present.
Nebulae, Stars, and Galaxies
Space contains nebulae (or nebulas). These are clouds of gas and dust formed when interstellar medium partially collapses due to gravitational attraction between the particles. Nebulae contain mainly hydrogen and helium. Some glow and some are colored. The beautiful photos of nebulae that are shown on astronomy websites may have been color enhanced in order to approximate their real appearance, however. Nebulae often produce stars.
A star is "born" as particles in a nebula move even further towards each other under the influence of gravity. Part of the gas and dust cloud collapses to form the star. The temperature increases during the collapse, eventually becoming high enough to trigger nuclear fusion to begin. In nuclear fusion, nuclei of atoms join, producing the star's energy in the process.
A galaxy is a collection of stars, gas, and dust. Scientists know that our galaxy—the Milky Way—contains other solar systems beyond our own, each with a star surrounded by orbiting planets. They also know that there are other galaxies beyond the one in which we live.
As of July, 2019, NASA says that the existence of 4,009 exoplanets (ones beyond the solar system) has been confirmed.
The Known Universe: A Virtual Tour
The Life Cycle of a Star
Scientists talk about the "lives" of stars, since stars change over time. They are born in nebulae. They eventually stop releasing energy and are said to be dead. A star's life as it ages depends on its mass.
Low Mass Stars
A star with a low mass ends its life as a red dwarf. Red dwarfs are thought to be the most abundant type of star. They exist for a long time and release their energy very slowly. Astronomers suspect that some may be able to live for trillions of years before they run out of fuel.
Medium Mass Stars
A medium mass star like our sun will become a red giant as it ages, then change into a white dwarf and finally a cold and dark black dwarf. The sun is believed to be about 4.5 billion years old and is middle aged at present.
High Mass Stars
A high mass star has a more violent life than a low or medium mass star. As it ages it turns into a red supergiant and then undergoes a dramatic explosion called a supernova. The material remaining after the explosion becomes a neutron star, or in the case of a very massive star, a black hole.
Gravity is the force of attraction between objects. The larger the mass of the objects or the shorter the distance between them, the stronger the force of gravity.
Neutron Stars, Magnetars, and Pulsars
A neutron star is only about 20 km in diameter, yet it has a mass of about 1.4 times the mass of the sun. Its gravitational field is so intense that protons and electrons are pulled together to form neutrons, giving the object its name. It also has a strong magnetic field. In addition, neutron stars rotate rapidly. Some spin at a speed of more than 700 rotations per second.
A magnetar is a neutron star that has an extremely strong magnetic field. Magnetars rotate more slowly than other types of neutron stars. A pulsar is a neutron star that produces a beam of electromagnetic radiation from a particular point. As we view a pulsar from Earth, the beam appears to be turning on and off at regular intervals due to the rotation of the pulsar. The beam consists of visible light, radio waves, x-rays, gamma rays, or more than one type of electromagnetic radiation.
The Electromagnetic Spectrum
A neutron star is so dense that on Earth one teaspoonful would weigh a billion tons.— NASA
Exotic Neutron Stars, from the Chandra X-ray Observatory
A black hole isn't an empty spot in space, as its name might suggest. Instead, it's a place where matter with a very large mass is filling a very small space. Since a black hole has such a huge and concentrated mass, it exerts a tremendous force of gravity. The gravitational force is so strong that not even light can escape from the area.
Scientists detect black holes by their effects on the objects that surround them. An object may be torn apart as it's pulled into a black hole. The object accelerates as it gets nearer to the "hole" and emits radiation in the form of x-rays.
Most galaxies—including our own—have a supermassive black hole at their center. The one at the center of the Milky Way is believed to have a mass that is 4.5 million times greater than the sun's mass. It's located twenty-eight thousand light years away from the Earth. A light year is the distance that light travels in one year, which is 9.46 X 1012 kilometers (9.46 trillion kilometers or 5.88 trillion miles). The Milky Way also contains many smaller black holes.
Think of a star ten times more massive than the Sun squeezed into a sphere approximately the diameter of New York City.— NASA (Description of a black hole)
Quasars (quasi-stellar radio sources) are very distant, brilliant objects that are releasing an enormous amount of energy. To us, they look like a pinpoint of light, just like a star. This is due to their huge distance from Earth. Astronomers say that quasars are actually releasing far more energy than a star.
Scientists think that a quasar is located in the center of a distant galaxy and is being powered by a supermassive black hole. The quasars that we see today may no longer exist, however. The light emitted from a distant object in space takes a very long time to reach Earth. When we examine distant space, we are seeing it as it once existed, not as it exists today.
There is much that is not yet understood about the universe. Intriguing areas of study include the origin and possible fate of the universe, fields and the disturbances within them, gravitational waves, exotic and unusual particles, and the behavior of objects in space.
More is known about space than I describe in this overview. Even so, there are many mysteries about the universe that need to be solved. I love to lie comfortably on the ground on a clear night, look up at the stars and planets that can be seen, and think about the universe. Speculation is fun. Knowledge would be even better.
It’s frustrating to realize that there is so much that is unknown about space and to think about how difficult it is to study the universe from our little area within it. It’s awesome to explore the night sky and to think about all the possibilities, however.
Mysteries of the Universe
I want to see the universe beyond the Earth,
to reach beyond the confines of this world
and travel far beyond the sky
to new and ancient mysteries
outside this comfort zone,
smaller than a tiny speck
lodged in the universe’s eye.
I'd love to see the stars beyond the night
and experience the awe,
to view the wondrous scenes
of destruction and of birth,
the cosmic acts of power
and fire of novelty
in nature never still.
I’d like to walk upon another world
and fly through space above,
senses nourished and enthralled.
I want to marvel at strange life,
to know dark matter and dark energy,
to see creation in the act
and explore the vast unknown.
I’d love to find out why? what?...and even who?
then move on to find the end of space and time
if such a place or thought exists;
or make the giant leap
beyond the universe,
a never ending trail
into the infinite beyond.
© 2011 Linda Crampton