What is a galaxy, anyway?
Our galaxy is a gravitationally bound collection of stars, swirling in a spiral through space. Based on the inmost images gotten so far, its one of about 2 trillion galaxies in the observable universe. Our galaxy probably includes 100 to 400 billion stars, and is about 100,000 light-years across.
Ok, fine, however what the heck is a light-year?
Happy you asked. Its one of the most commonly used celestial yardsticks, the range light journeys in one year. Light zips along through interstellar area at 186,000 miles (300,000 kilometers) per second (more than 66 journeys throughout the entire United States, in one second). Multiply that by all the seconds in one year, and you get 5.8 trillion miles (9.5 trillion kilometers). Just for referral, Earth has to do with 8 light minutes from the Sun. A trip at light speed to the very edge of our solar system– the limits of the Oort Cloud, a collection of inactive comets method, method out there– would take about 1.87 years. Keep going to Proxima Centauri, our closest surrounding star, and strategy on showing up in 4.25 years at light speed.
, if you could take a trip at light speed.. Which, unless youre a photon (a particle of light), you cant, and, by present physics, might never be possible. But I digress.
Can we return to those…X-planets?
Exoplanets. Lets toss around some more huge numbers. How lots of are there? Based on observations made by NASAs Kepler space telescope, we can confidently predict that every star you see in the sky most likely hosts a minimum of one world. Realistically, were probably discussing multi-planet systems instead of just single planets. In our galaxy of hundreds of billions of stars, this presses the number of worlds possibly into the trillions. Verified exoplanet detections (made by Kepler and other telescopes, both in space and on the ground) now come to more than 3,900– whichs from looking at only small slices of our galaxy. A number of these are small, rocky worlds that may be at the best temperature for liquid water to swimming pool on their surface areas.
Where is the closest among these exoplanets?
Its a small, probably rocky world orbiting Proxima Centauri– as mentioned in the past, the next star over. Not much is known about this world; its close orbit and the regular flaring of its star lower its opportunities of being habitable.
Any others?
I d likewise point you to the TRAPPIST-1 system: seven worlds, all approximately in Earths size variety, orbiting a red dwarf star about 40 light-years away. They are likely rocky, with four in the “habitable zone”– the orbital range allowing possible liquid water on the surface area. And computer modeling reveals some have a great chance of being watery– or icy– worlds. In the next couple of years, we may learn whether they have atmospheres or oceans, or even indications of habitability.
Ok. Thanks. I need to go.
I comprehend. Youre short on time. That advises me: Did you know time slows down in the presence of gravity?
I know its decreasing today.
I guess thats a discussion for another time.
Our galaxy is a gravitationally bound collection of stars, swirling in a spiral through space. Based on the deepest images acquired so far, its one of about 2 trillion galaxies in the observable universe. Our galaxy most likely contains 100 to 400 billion stars, and is about 100,000 light-years across. Another galaxy, IC 1101, covers as much as 4 million light-years.
In our galaxy of hundreds of billions of stars, this pushes the number of worlds potentially into the trillions.
If viewed from above, this artists rendering reveals a view of our own Milky Way Galaxy and its central bar as it might appear. Credit: NASA/JPL-Caltech/R. Hurt (SSC).
When we discuss the enormity of the cosmos, its simple to toss out big numbers– but far more challenging to wrap our minds around just how large, how far, and how various heavenly bodies actually are.
To get a better sense, for example, of the real distances to exoplanets– worlds around other stars– we might begin with the theater in which we find them, the Milky Way galaxy.