SUKABUMIUPDATE.com A galaxy is a collection of stars and space objects held together by gravity. The number of galaxies in the universe is estimated to be over 100 billion.
Galaxies in the universe present a beautiful structure that can be seen in telescope images like NASA’s latest and most advanced James Webb Telescope.
At the most basic level, we can think of a galaxy as a collection of stars, gas and dark matter, all of which are gravitationally bound to each other, said Jenna Samuel, a doctoral candidate in astrophysics at the University of California.
And what we see as a typical Galaxy in the image is mostly bright parts (stars) embedded in a circle of dark matter that’s much bigger and longer than it really is.
Launching from Live Science, Samuel said if the individual parts of the Milky Way would continue to interact with each other to give the Milky Way a shape.
The dark matter that forms part of the Milky Way provides most of the mass and uses gravity to hold it together.
In addition, the stars that make up the Milky Way also radiate heat around the gas and dust, and when dead stars explode spectacularly (supernova), they scatter other matter near and far.
Meanwhile, Earth and our Solar System are in the Milky Way, a large spiral galaxy containing between 100 billion and 400 billion stars.
At the center of the Milky Way Galaxy, there is a bright band resembling spilled milk, which the ancient Romans called Via Lactea, which in Latin means Milky Way.
At the center of the galaxy’s spiral is a wealth of energy that sometimes burns like clear fire.
Based on the extraordinary gravity needed to explain the motion of stars and the energy they emit, astronomers concluded that the center of the galaxy is a supermassive black hole.
And keep in mind, almost every known galaxy has a supermassive black hole at its center, which also plays a role in determining the characteristics of the galaxy.
So do you know what a galaxy is? If not, let’s take a look at the explanation below, as reported by Live Science.
1. Galaxy Types
The Milky Way is a spiral galaxy, which means it is flat, large, and has many arms around its central bulge, Samuel said.
Spiral galaxies themselves form stars at a moderate rate and generally have a mass similar to that of the Milky Way.
When you include all the stars, gas, dust and dark matter, the mass of a spiral galaxy is about 1 trillion times the mass of the Sun.
In addition to spiral galaxies, there are other types, such as dwarf galaxies, which means that these galaxies are much smaller than spirals and do not have a regular structure.
Then there is also a large elliptical galaxy which means that its size is much bigger than the Milky Way.
Elliptical galaxies look somewhat round like eggs and their stars are older. In addition, the ellipsoid has also stopped forming new stars long ago.
Elliptical galaxies are massive galaxies, often reaching 100 trillion or 1 quadrillion times the mass of the Sun.
2. The galaxy closest to the Milky Way
According to NASA, the closest galaxy to the Milky Way is Sagittarius. Sagittarius is a small, irregular galaxy located about 70,000 light-years from Earth.
Being so close to the Milky Way, the sagittal component is consumed by the gravity of our galaxy because the sagittal unit itself is very small.
In addition to Sagittarius, the Canis Major Dwarf Galaxy is also closer to the Milky Way at a distance of about 25,000 light-years from Earth.
In fact, it is estimated that in the next 1 billion years, Canis Major will completely merge with the Milky Way.
Samuel also noted that many other satellite galaxies orbit the Milky Way, as do planets around stars.
The two best known companion galaxies are the Large Magellanic Cloud and the Small Magellanic Cloud, which are visible from Earth only in the Southern Hemisphere.
According to NASA, the Large Magellanic Cloud is 179,000 light-years away from the Milky Way, while the Small Magellanic Cloud is 210,000 light-years away, and they too are expected to merge with the Milky Way one day.
In addition, there is a large galaxy closest to the Milky Way i.e. Andromeda or M31, and it is a large spiral galaxy located about 2.5 million light-years away.
The gravitational pull is pulling the Milky Way and Andromeda closer together, and research suggests they will collide in about 4.5 billion years, Live Science previously reported.
3. Galaxy Formation
Most galaxies are billions of years old and no one knows when the first galaxies were formed, but telescope observations suggest that there were only small, dwarf-sized galaxies at the beginning of the universe.
Meanwhile, larger galaxies and larger galaxies like the Milky Way formed over time as many smaller galaxies came together.
A recent study suggests that the Milky Way galaxy gained half of its current mass due to a merger about 7 billion years ago.
“That’s when we actually see something that starts to look like a galaxy,” he said.
Meanwhile, large ellipses are formed when many spiral galaxies gather together. Astronomers mostly see these galaxies in dense regions of the universe, where many galaxies have collapsed together over the course of the universe.
4. How many galaxies are there in the universe?
Astronomers count galaxies by training telescopes in dark patches of sky over long periods of time.
They count the galaxies they can see and then figure out how many more, depending on the range of telescopes they have.
But this method is limited and incomplete, meaning there may be more galaxies than scientists thought.
So according to Samuel, the correct answer to the question of how many galaxies are there in the universe is hundreds of billions.
Source: Live Science | NASA