We often refer to our expanding universe with one simple word: space. But where does space begin and more importantly, what is it?
Space is a near-perfect vacuum, almost devoid of matter and with extremely low pressure. In space, sound is not carried because there are no molecules close enough to each other to transmit sound between them. Not completely empty, pieces of gas, dust, and other matter float around the “emptier” regions of the universe, while the more densely populated regions may contain planets, stars and galaxies.
Our word Earth– frontier perspective, outer space is generally thought to begin about 62 miles (100 km) above sea level in what is known as The Kármán . line. This is the imaginary boundary at high altitude where there is no appreciable air to breathe or scatter light. Beyond this altitude, blue begins to give way to black because oxygen molecules are not abundant enough to make the sky blue.
No one knows exactly how big space is. It is difficult to determine because of what we can see in our detector. We measure long distances in space in “light years,” which represents the distance that light travels in a year (about 5.8 trillion miles (9.3 trillion kilometers)).
From the light visible in our telescopes, we’ve charted galaxies as far as the Big Bang, thought to have started our universe about 13.8 billion years ago . This means we can “see” into space at a distance of nearly 13.8 billion light-years. But the universe continues to expand, making “measurement of space” all the more difficult.
In addition, astronomers are not entirely sure whether our universe is the only one that exists. This means that space can be a lot bigger than we think.
Spatial radiation invisible to the human eye
Much of the space is relatively empty, with only bits of dust and gas floating around. This means that when humans send a probe to a distant planet or asteroid, the probe will not experience “drag” in the same way that an airplane does when it slams through space. time.
In fact, the vacuum environment in space and on the moon, is one reason why the Apollo lunar lander was designed to have an almost spider-like appearance, as it was described by the Apollo 9 crew. Since the spacecraft is designed to operate in the no-atmosphere, it does not need to have smooth edges or an aerodynamic shape.
In addition to debris dotting regions of “emptier” space, research has shown that these regions are also home to different forms of radiation. In our solar system, wind – charged particles emitted by the sun – which radiate throughout the solar system and sometimes cause auroras near the Earth’s poles. Cosmic rays also pass through our neighborhood, originating from supernovae outside the solar system.
In fact, the universe as a whole is flooded with what’s known as the cosmic microwave background (CMB), which is essentially radiation left over from the explosion, mostly commonly known as the Big Bang. CMB is the oldest radiation that our instruments can detect.
Infographics: Cosmic microwave background explanation
Dark matter and energy
While scientists have provided much evidence for the existence of dark matter and dark energy, they are still poorly understood because until now, scientists could not directly observe them and only their effects can be observed.
About 80% of the mass in the universe is made up of what scientists call “dark matter”, but it is not known what it really is or if it is matter by current definition. at ours. However, while dark matter emits no light or energy and is therefore not directly observable, scientists have found overwhelming evidence that it makes up most of the matter in the universe.
Dark energy may have a similar name to dark matter, but it is a completely different composition.
Believed to make up nearly 75% of the universe, dark energy is a mysterious and unknown force or entity that scientists think is responsible for the continued expansion of the universe.
Less black hole can form from the gravitational collapse of a massive star, forming a singularity from which nothing can escape – not even light, hence the object’s name. No one is sure what lies inside a black hole, or what will happen to a person or object that falls into it – but research is ongoing.
One example is gravitational waves, or ripples in space-time that come from interactions between black holes. This was first predicted by Albert Einstein at the turn of the last century, when he showed that time and space are interrelated; Time speeds up or slows down when space is distorted.
As of mid-2017, the Scientific Cooperation Organization of the Laser Interferometer Gravitational-Wave Observatory (LIGO) has published three Black hole interactions and mergers detected via gravitational waves, in just two years.
Scientists said in May 2017. The team found these three events over about two years, showing that when LIGO was deployed at maximum sensitivity, the observatory was able to find the types of events. This event is regular, scientists said in May 2017. If this series of black hole events are detected. , it can help scientists learn how black holes of certain sizes (several tens of solar masses) are born, and then merge into new black holes.
Stars, planets, asteroids and comets
Stars (like our sun) are giant spheres of gas that produce their own radiation. They can range from a red supergiant to a cooling white dwarf that is the remains of a supernova, or the stellar explosions that occur when a massive star runs out of gas to burn. These explosions spread elements throughout the universe and are the reason for the existence of elements like iron. Star explosions can also give rise to extremely dense objects known as neutron star. If these neutron stars emit pulses of radiation, they are called pulsars.
Planets are objects whose definition was thoroughly studied in 2006, when astronomers were debating about can Pluto be considered a planet?. At that time, the International Astronomical Union (the governing body on Earth for these decisions) ruled that a planet was a celestial body orbiting the sun, large enough to have a close appearance. is round and has cleared its orbit. By this name, Pluto and similar small objects are considered “dwarf planets”, although not everyone agrees with the name. After the New Horizons spacecraft flew by Pluto in 2015, principal investigator Alan Stern and others opened up the debate again, saying that the variety of terrain on Pluto makes it look like a planet. more refined.
The definition of an extrasolar planet, or planet outside the solar system, has not yet been solidified by the IAU, but astronomers basically understand it to mean objects that behave like planets. in our neighborhood. The first such planet was found in 1992 (in constellation Pegasus) and since that time thousands of exoplanets have been confirmed – with many more suspected. In the solar system with forming planets, these objects are often referred to as “protoplanets” because they are not quite the maturity of the planets we have in our own solar system.
Small planet are rocks that are not large enough to be dwarf planets. We have even found asteroids with rings around them, such as 10199 Charilko. Their small size often leads to the conclusion that they are remnants from when the solar system was formed. Most of the asteroids are concentrated in a belt between the planets Mars and Jupiter, but there are also many asteroids that follow behind or in front of the planets, or may even cross in their path. of a planet. NASA and several other entities have asteroid-seeking programs that scan for potentially dangerous objects in the sky and monitor their orbits closely.
In our solar system, comet (sometimes called dirty snowballs) are objects thought to have originated from a huge collection of icy objects known as the Oort Clouds. As a comet approaches the sun, the heat of our star causes the rock to melt and flow away from the comet. The ancients often associated comets with destruction or some kind of great change on Earth, but the discovery Halley’s Comet and related “cyclic” or retrograde comets suggest that they are normal solar system phenomena.
Galaxies and quasars
Among the largest cosmic structures we can see are galaxies, essentially huge collections of stars. Our galaxy is called Galaxy, and is considered a “barred spiral”. There are several types of galaxies, from spiral to elliptical to irregular, and they can change as they approach other objects or as the stars within them age.
Usually galaxies have supermassive black hole embedded in the centers of their galaxies, which can only be seen through the radiation each black hole emits as well as through its gravitational interactions with other objects. If the black hole were particularly active, with a lot of matter falling into it, it would generate enormous amounts of radiation. This type of galaxy is called quasar (just one of several similar object types.)
Large groups of Galaxies can form in clusters those are groups as large as hundreds or thousands of galaxies that are gravitationally bound together. Scientists consider these to be the largest structures in the universe.
This page was updated in January 2022 by Space.com senior writer Chelsea Gohd.
https://www.space.com/24870-what-is-space.html What is space? – Definition of our universe and beyond