Our Sun is one of at least 100 billion stars in the
One such estimate says that there are between 100 and 200 billion galaxies in the observable universe. Other astronomers have tried to estimate the number of 'missed' galaxies in previous studies and come up with a total number of 2 trillion galaxies in the universe.
Generally, they conclude, life is possible only in the outer regions of large galaxies. (Our own solar system is about 27,000 light-years from the center.)
In a galaxy that likely holds trillions of planets, ours is so far the only known life-bearing world.
In the vast, expanding space known as the universe, humans reside on a small, rocky planet called Earth. Our planet is part of a discrete solar system in an arm of the spiral shaped Milky Way Galaxy. Our galaxy is only one of billions of other galaxies that exist within the universe.
If the universe is infinite, there is nothing beyond it, by definition. A finite expanding universe conjures up the idea that it would have a boundary or edge, separating it from something beyond.
Among the stunning variety of worlds in our solar system, only Earth is known to host life. But other moons and planets show signs of potential habitability.
Live Fast, Die Young
Why these galaxies stopped forming stars so early is still a puzzle. These dead galaxies appear to remain dead even after 11 billion years, in the present-day universe.
Flexi Says: Right now and for the foreseeable future, humans can only live on Earth. Humans have not traveled very far into space. The Moon is the only other place humans have visited. No other planet in our solar system currently has the conditions to support life as we know it on Earth.
But when NASA's Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array (ALMA) in northern Chile gazed toward cosmic objects in this period, they found something odd: six early, massive, "dead" galaxies that had run out of the cold hydrogen gas needed to make stars.
To date, no proof of past or present life has been found on Mars. Cumulative evidence suggests that during the ancient Noachian time period, the surface environment of Mars had liquid water and may have been habitable for microorganisms, but habitable conditions do not necessarily indicate life.
Using data from NASA's Transiting Exoplanet Survey Satellite, scientists have identified an Earth-size world, called TOI 700 e, orbiting within the habitable zone of its star – the range of distances where liquid water could occur on a planet's surface. The world is 95% Earth's size and likely rocky.
Are we going to stay on the Milky Way Galaxy forever? The milky way is 100,000 Light years across. This would mean that we will have to travel very very very fast to even leave the Milky Way. However in time we may work out how to Terra-form a planet or find life on planets and slowly expand.
Our Planet Is Among the First of Many, Many Earths
A billion trillion of them. In the Milky Way alone, that would mean another 5 billion Earth-like planets over time.
In total, Hubble has discovered about 100 billion galaxies in the Universe. However, after James Webb is fully operational, this number will probably increase to 200 billion. Moreover, scientists are not sure that even 200 billion galaxies is the final figure.
We currently have no evidence that multiverses exists, and everything we can see suggests there is just one universe — our own.
Only our two nearest neighbours Venus and Mars have been landed on. Landing on another planet is technically challenging and many attempted landings have failed. Mars is the most explored of the planets. Mercury could be landed on but the speeds involved and the proximity to the Sun are challenging.
Because of the Moon's sparse atmosphere, there is no protection from meteorites or radiation. The temperature fluctuations on the Moon are also intense, ranging from -248 to 123 degrees Celsius (-414 to 253 degrees Fahrenheit). To make the Moon habitable, we would need to live in shelters.
Jupiter's environment is probably not conducive to life as we know it. The temperatures, pressures, and materials that characterize this planet are most likely too extreme and volatile for organisms to adapt to.
At five times the mass of the Large Magellanic Cloud, Andromeda could completely destroy the Milky Way when the two collide. That cosmic catastrophe is expected in about four billion years' time.
Milky Way Galaxy and the Andromeda Galaxy merge into one
Approximately five billion years from now, or 19 billion years after the Big Bang, the Milky Way and the Andromeda Galaxy will collide with one another and merge into one large galaxy based on current evidence (see, Andromeda–Milky Way collision.)
Someday our little corner of the universe will have a ringside seat for one of the biggest events in the cosmos. Two billion years from now, the Milky Way and Andromeda, our closest neighboring galaxy, will begin to fuse into one giant football-shaped galaxy.
Earth is at an adequate distance from the sun which gives us heat that is neither too hot nor too cold. Earth has enough amount of water, food, and air for the survival of living organisms. Earth has a protective ozone layer which protects us from the harmful rays.
It is a common misconception that “Terra” is the internationally-recognized scientific name of the planet, but in reality Earth does not have an official international name. The standard English name of the planet, including in science, is “Earth”.
The name Earth derives from the eighth century Anglo-Saxon word erda, which means ground or soil, and ultimately descends from Proto-Indo European *erþō. From this it has cognates throughout the Germanic languages, including with Jörð, the name of the giantess of Norse myth.