And I think it's fair to say, we've learned a few things since then.

Hey planetoids, Trace here for DNews. In 1584, a Catholic Monk, Giordano Bruno claimed

there were "countless suns and countless Earths." More than 400 years later, in a 1995 book

on exoplanets three scientists wrote, "The detection and study of Earth-like planets

outside our Solar System will be one of the great scientific, technological and philosophical

events of our time." Because even with so much time in between, no earth-like planets

had been confirmed! A decade later, the first earth-like planet, Gliese 581 C, was discovered;

and as of March 2015, we've confirmed 29 water-holding habitable, earth-like planets; and calculations

say there might be BILLIONS more,. Do you feel like you live in the era of a huge scientific,

technological and philosophical event? You should!

There's a huge database of possible candidates and confirmed exoplanets, and as we observe

OTHER solar systems we're learning things about how OUR solar system works. New research

in the Proceedings of the National Academy of Sciences used other solar systems as a

model for our own. Our solar system was formed from leftovers after the Big Bang, gas and

dust coalesced into planets over many many millions of years. OTHER solar systems have

supermassive exoplanets closer to their sun, but we don't. Scientists believe Jupiter was

the reason ours looks different.

They believe, Jupiter USED to be closer to the sun, and tacked outward, dragging all

the junk from the inner solar system with it. When the solar system first formed, there

were planetesimals, or small planetary building blocks, flying around in the inner solar system

where Mercury, Venus, Earth, and Mars are now. While today, Jupiter orbits at about

5 AUs, it used to range from 3 to 10! All that motion cleared the way like a wrecking

ball. It could have even destroyed any other proto-planets which formed before the four

inner planets we have now. This Wandering Jupiter hypothesis isn't the perfect explanation

for why we look different, but it hits a lot of checkboxes on the way to a good theory.

Keeping an eye on the sky has also helped us feel a little less alone. A study in the

Astrophysical Journal found Kepler 444, a solar system which has five Earth-like planets

orbiting it in a way very similar to our own -- AND it's 11.4 billion years old, meaning

those planets were formed long before ours and are relatively similar in size. The problem

is, they're too close to their star, orbiting in only around 10 days -- Mercury orbits in

84 days. So, while 444 doesn't have life, it shows planets can form really FAST, and

that's USEFUL because there might be life-capable planets with a billion-year head start on

us out there!

The Kepler telescope was launched in 2009 to search for exoplanets and, in case you've

forgotten, KEPLER is BROKEN and is STILL finding them. The Milky Way has between 100 and 400

billion stars -- that's a lot of places to point a telescope. The more we learn, the

more scientists can make educated guesses and point telescopes at the right stars. It

might be blazé to say it, but I'm pretty sure, finding other planets really is the

most scientific, technological and philosophical event that you never think about. And we really

should think about it more, because it teaches us so much about our own!