Milky Way Galaxy: Let's Deep Dive Into Our Space

When we talk about the enormity of the cosmos, it’s easy to toss out big numbers – but far more difficult to wrap our minds around just how large, how far, and how numerous celestial bodies really are.

What is a galaxy, anyway?

Milkyway is a galaxy that includes the solar system. A hazy of light seen in the night sky formed from stars that can not be distinguished by the naked eye, Deep down, our galaxy is a gravitationally bound collection of stars, swirling in a spiral through space. In the early 1920s, most astronomers thought that the Milky Way contained all the stars in the Universe. Groups of them are bound into clusters of galaxies. Our galaxy probably contains 100 to 400 billion stars, and it is about 100,000 light-years across.

Does it sound enormous?

It is one of the most common only used celestial yardsticks, the distance light travels in one year. Light zips along through interstellar space at 186,000 miles (300,000 kilometres) per second. Multiply that by all the seconds in one year, and you get 5.8 trillion miles (9.5 trillion kilometres). Earth is about eight light minutes from the Sun. A trip at light speed to the very edge of our solar system. The farthest reaches of the Oort Cloud, a collection of dormant comets way, out there, would take about 1.87 years. Keep going to Proxima Centauri, our nearest neighbouring star, and plan on arriving in 4.25 years at light speed.

According to NASA's Kepler space telescope, they predict confidently that every star you see in the sky probably hosts at least one planet. In our galaxy of hundreds of billions of stars, pushes the number of planets potentially into the trillions.

Where is the nearest one of these exoplanets

It is a small, probably rocky planet orbiting Proxima Centauri, the next star over. A little more than four light-years away, or 24 trillion miles as the crow flies. If an airline offered a flight there by jet, it would take 5 million years. Not much is known about this world; its close orbit and the periodic flaring of its star lower its chances of being habitable.

Any others?

I would also point you to the seven planets, all roughly in Earth's size range, orbiting a red dwarf star about 40 light-years away. They are more likely rocky, with four in the "habitable zone". The orbital distance allows potential liquid water on the surface. and computer modelling shows have a good chance of being watery or icy worlds. In the next few years, we might learn whether they have an atmosphere or oceans, or even signs of habitability.

Ok. Thanks. I need to go.

I understand. You’re short on time.

That reminds me: Did you know time slows down in the presence of gravity?