How Earth-Like Planets Work

Since the Kepler telescope went online, astronomers have found there may be an estimate 40 billion planets like Earth in the Milky Way galaxy alone. What does it take for a planet to be considered Earth-like?

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Episode Transcript

Speaker 1 (00:01):
Welcome to you Stuff you should know from house Stuff
Works dot com. Hey, and welcome to the podcast. I'm
Josh Clark. There's Charles W. Chuck Bryant, There's Jerry AND's
the stuff you should know. Just a few geezas, what not?

(00:22):
Galizas very good? That was terrible, is what it was.
I read an article the other day on my people
find puns so offensive. It's very interesting. Oh yeah, I
know it is. Yeah, I'm sending my way, will you sure? Thanks,
You're welcome. Chuck. Yes, have you ever heard of an

(00:44):
exo planet? Yes? You have. Well that's all I got.
I'm down. I'm done with Kepler. Kepler is pretty awesome,
isn't it. Kepler is way awesome. Let's talk about Kepler.
What is it? Well, Kepler is a guess what you
call it? A program? Sure, the Kepler Project program. It's
a mission. Yes, it's all the mission. And since two

(01:08):
thousand nine they have Their task has been to survey
the sky in fact, um, well a small patch of
sky right now. And it's an outer space telescope. Yeah. Sure,
it's spine on people in the city park. No, no no,
they shot it out in a space. It's dressed in
like a silver um jumpsuit, so you can tell it's

(01:31):
a space telescope and not just like a regular one.
And uh yeah, it has a little twelve degree um
field of vision, and what it's doing is just looking
out into the cosmos in the Milky Way. Still. Yeah,
specifically near the constellations Sickness and Lira. For now. For now,

(01:53):
you gotta start somewhere, right, you only have twelve degrees.
You know, it's not the big ear. It's like a journey.
You have a thousand miles starts through the singles that. Uh. Basically,
what they're trying to do is see I think the
ultimate goal it's just to see what's out there. But
what they really secretly get giddy about and titter about

(02:16):
um late at night is finding exoplanets that are like
our own Earth. I know. I think the whole thing
was a straight up planet hunting mission. Well yeah, but
like I said, they're not just like we want to
find another Earth. They they're like, we want to see
what's out there because we don't know what's out there. Yes,
and they get really excited when it's not a big
giant ball of gas. So the Kepler mission actually the

(02:37):
first Kepler mission ended this past May because the Kepler
telescope I think ran out of battery power or something
like that to turn itself. But they started there. They're
ramping up the K two mission, which is actually this
is so amazing to me. I love this stuff. It's
they're going to use photons light from the Sun to

(02:59):
move it. Pretty amazing. And the photons are going to
move this thing called solar power to direct it and
look in different directions. It is very much so amazing. Um.
So the whole point is is defined planets. But really,
like you say, what they're looking for our planets that
fall within what's called the Goldilocks zone or the habitable zone.

(03:22):
And there's a couple a couple of different types of zones. Yeah,
if we're talking the Goldilocks zone, what we mean is
a planet that, um where there is water that doesn't
evaporate immediately or freeze. Well, yeah, that's one way to
put it. You know, flowing water would be great, so

(03:43):
CEO two that'd be awesome. So the whole Earth earthlike planets, right,
earthlike is what it what it comes down to, able
to sustain life, right, and the the whole thing. I've
read this really interesting article, Chuck, and it was I
think it was an aon magazine like it is one
of the greatest online magazines ever created, so interesting, everything

(04:05):
is so well written. It's just great. A on magazine,
aon magazine anyway. Um, the the person writing this article said,
what if our conception of life is really limited? And
when we think of life, we think of like um

(04:25):
genetic genetic molecules capable of self replicating, right, like us,
like life, like anything that that can make new copies
of itself, cellular reproduction. Right. So, um, what if there's
life has evolved in many, many other ways, not just
out an outter of space, but here on this planet,

(04:46):
Like we could be surrounded by life and not even
be aware of it because we're not thinking of it
that way. We're strictly looking for evidence of um DNA
based life. If life evolved in other ways and it's
we're surrounded by it, that's pretty neat. That's one of
those late night college conversations, if you know what I mean.
But with Kepler too, it's looking for planets that could

(05:11):
sustain a certain brand of life, which is the life
that we know and the whole thing is predicated on
the idea that you need water and liquid form to
be the foundation, the the sustaining foundation of life. And
so that's what that's what this habitable zone is. It's
a planet that is far enough away from the Sun

(05:33):
that it can um. It's it's surface water is not
going to boil away and turn it into um and
just just go into the atmosphere far away from its star. Right,
not necessarily the Sun. Right, it's star is what I mean.
It's version of our Sun, yes, yes, oh, and but

(05:55):
it's not so far away that it's not getting enough
heat so that it just frees. So it's within this
what's called the circumstellar habitable habitable zone. It's or it's
in this little distance like we are in our sun.
Our stars habitable zone are its circumstellar habitable zone, right,
And so it's looking for planets that um are surrounding

(06:17):
stars in that little band that's not so close that
it's too hot and not so far away that it's
too cold. It's just right. I love it. That's called
the Goldilocks zone. Yeah, that's the name for it. Um.
So there are they have the Kepler mission has returned
UM a lot of startling information like thousands, perhaps tens

(06:40):
of thousands or hundreds of thousands of planets maybe out there. Um,
in fact, probably are out there. I think it's forty
billion in the the Milky Way alone, is what estimates
are unbelievable in the Milky Way alone. Forty billion Earth
sized planets, not just all plants. Forty potentially Earth sized

(07:03):
planets in the Milky Way alone. Yeah. So, like I
was saying, UM, giant balls of gas are fun gas
giants like Saturn and Jupiter, they're needo torpedo. But UM,
as far as science really getting um getting their rocks off,
these Earth size planets are the ones that that that's
where the money is, you know, right, And when I

(07:24):
say money, I don't mean cash money, although if we
colonize them, I guess it could be cash money. But
the smaller planets, what they call terrestrial planets earthlike planets,
UM are terrestrial planets would be a great band name,
by the way, because they are They have heavy metal
cores and rocky mantle, and they have smaller orbits, shorter years,

(07:47):
they're close to the host star. All these things that
are Earth like, which could mean potentially you know something there,
so okay, so something living. You've got the circumstellar habitable zone,
which is not too close to the Sun or not
too close to the star, not too far away from
the star. But there's also um a larger habitable zone

(08:08):
that that kind of if you have that one, great,
But there's some other qualifications that a planet has to
hit to be considered habitable, and these are galactic habitable zones, right,
So part of that is that it has to have
a heavy metal core, like you say, it's got to
be terrestrial. It also has to um it can't be

(08:31):
tidally locked. Right. There's we found actually some planets out
there that fit the bill, except they are tidally locked
with their star, which means only one side and the
same side is always facing the sun, which means that
that is a very very hot body of water right
there that's facing the sun. And then on the back side,

(08:52):
the dark side, it's just completely frozen and since it's
not turning, the atmosphere is not being um kept around,
the planet is able to like migrate to like say
the dark side of the planet and just freeze there.
That's a great example of how you can have all
these other things. That planet might be in the habitable

(09:13):
zone for its star, but it falls out of the
category of a truly habitable planet because it's missing some
other factors, for example not being tidally locked. So that
would be the case with Gliza fight one G. So yes, okay,
So that is was discovered in two thousand ten, and
there's been a lot of back and forth between a
lot of different countries and scientists saying is it really there?

(09:36):
Is it not there? I think where it lands now is?
They are pretty sure it's there. Um. But with Glees
eight one g um, it faces uh the star at
all times, one side of it does, so it's tightly locked,
tightly locked. Um. Although it does orbit once every thirty

(09:56):
seven days, it keeps that face. So basically what they think,
because if there could be life there, you have what
they would call an eyeball Earth with a one part
of this planet having being liquid water right and the
rest of frozen, so like an eyeball in the middle
kind of neat. I think what keeps Glees of eight
one g in the news is the fact that it's

(10:19):
only twenty point five light years away. Um. And we'll
talk about some more of these, but a lot of
them are like over a thousand light years away. So
let's take a break real quick and we'll get back
to exoplanets right after this. So check you you touched

(10:50):
on something I think is very important before we go
any further there. People say, well, yeah it exists, or no,
it doesn't exist. And there's a lot of back and
forth in the scientific community. And the reason is, is
the as as high powered and awesome as the Kepler
telescope is it really is. It doesn't look at a

(11:11):
star and say, oh, look at that planet. That's a
fine looking planet right there. It looks like, oh yeah,
I can see water on there and wall like a
giant pterodactyl like a monkey head. Yes it is. No,
it can't see these kind of things, right. So there's
different techniques that are used for hunting planets exoplanets, um,

(11:35):
that use deduction in a lot of ways in concert
with these telescopes right to surmise the existence of planets.
So um, there's three main techniques that even these telescopes
us Like the Kepler telescope is it uses a photometer

(11:56):
which senses light, right, and it'll look at a star,
are and it'll just keep looking at the star, looking
at the star. It's got a really good Uh, something
weird just happened at the star got dim and then
it went back to normal light. And what just happened
was probably a planet orbited in between the telescope and
the star, which dim the light of the star. That's right.

(12:19):
They called that a transit and that technique is called
the transit method. And so they, like you said, they
use that photometer and um, if they see that dim
that's a lead in the right direction. Yeah, and now
it doesn't prove anything, no, so that that that planet
becomes a candidate planet. So they go back and they
look at it. And if they say, use a different technique,

(12:41):
or if they um, if they come up with the
same data using that same technique again and again, then
most likely that planet does exist and it becomes a right,
it becomes a confirmed planet. So it goes from a
candidate planet to a confirmed planet. Um. And there's a
lot of criticism in this side actific community because when
a candidate planet is found, it is far from being

(13:04):
proven as existing. But um, it's very frequently rushed out
to the media, which treats it like a new planet's
been discovered and we know all about it, when we
really don't even know for a fact it exists, And
very infrequently the science behind having to deduce its existence
is explained in in the in the articles that are

(13:28):
written about them. So it just gets rushed to press
a little too premisuarly to keep that public interest up,
you know. Yeah, but it wouldn't hurt to also educate
the public at the same time. So a lot of
people say, oh, well that we just discovered a new
planet where it's still a candidate planet and it doesn't
we don't necessarily know it exists. It's a good point, um.

(13:50):
So that the transit method is is the one where
the light pulses, the star pulses, well, it dims because
the planet comes in between the telescope and the yeah star.
Then you have the wobble method, which is pretty neat
in itself. Um. It looks for changes in relative velocity
caused by the gravitational pull of another nearby planet. So

(14:12):
basically what happens is they use the spectrum of light
for this one and they analyze that spectrum around this
uh what they think could be a planet. It planet
it planet it can planet it so, thank you. So
what happens is if it is being pulled by another planet,
when it surges towards Earth and then away, it causes

(14:33):
variations in that light spectrum. So when it comes towards Earth, um,
it shortens a wavelength and you see a blue spectrum
more um. When it goes away from Earth, it lengthens
and you see red more So it's almost like a
color pulse. Uh. And that is the Wobble method. So
that's number two. And that's the Doppler effect. Uh is it? Yeah,

(14:55):
but with light instead of sound. But the Compler effect
is only sound. No, it's any kind of wavelength. Oh
I thought the Doppler effect was strictly sound. No, it's
it's it's any I'm telling you. It's the thing that
links bats to earthlike planets, to Doppler to a passing ambulance. Yes, man,

(15:15):
I'm so psyched about the Doppler effect. Uh. And you
want to go ahead and hit us up with that
last one micro lensing that's pretty neat too, yes. So, um,
when you have a star and another star passes, if
you're looking at a star with say if um, like
the the Kepler telescope, which the Kepler telescope strictly uses
the transit method from what I understands, So you have

(15:39):
another telescope that that is more open minded. Yeah. UM,
And you're looking at a star and another star comes
in between you and the star. You're looking at that
star that's in the foreground, that's in between you and
the original star. UM actually takes the light and acts
as a kind of a magnifying lens and intensifies the

(16:01):
light of the star behind it thanks to its gravity.
This is called micro lensing. Right. If a planet falls
into that that's an orbit around that other star falls
in line with this, it takes that um that micro
lensing effect and amplifies it even further. And then you
can calculate, based on the amplification of the micro lensing effect,

(16:24):
the mass of all of the stars and this new
mystery planet that just came into into line with this orbit. UM,
And they use that mind blowingly enough to deduce the
presence of planets around stars too. So you've got these
three methods and all of them though again it's really
important to remember this, all of these used deduction, Like

(16:48):
none of these planets have been visually observed. They are
all deduced to exist based on um, the mathematical evidence
that there's something going on here, like that this light
is dimming, this color is changing, or the light is
being amplified by something, and it all has to do

(17:08):
with mass and gravity. It's pretty amazing. Yeah, alright, so
we'll take a little break here and come back and
talk about some of these exo planets and if there
are people living there, there aren't so chuck. Remember we

(17:40):
mentioned the transit method. You can also use these things
to deduce even more stuff about these planets once you
confirm they exist. Personality, right, it's signed like kind of things. Um.
There's something called transit spectroscopy which uses the apparently the
atmosp fear of a planet leaves a certain kind of

(18:03):
mark on the light that it messes with in the
star that you're looking at. So not only are you
deducing that the planets there, you're deducing by the effect
that that planet has on the light the type of
atmosphere it has as well. So pretty amazing, right, So
once they figure out that yes, the planet is likely there,

(18:25):
they go back and look at it and the planet
goes from a candidate to a confirmed planet, and the
Kepler Um came up with one thousand and thirty confirmed exoplanets,
twelve of which are in a Goldilocks zone. Right. Um,
they really start going to town studying this planet and
figuring out what its atmosphere is like, where it is

(18:46):
in relation to the star, what the temperature is, and
they can tell some pretty amazing stuff about an exo
planet just from all of these deductions. Yeah, Like, uh,
I guess let's just talk about a couple of these
UM the the Gliza. Uh I guess it's a group
because there are several glazes. There's a gliza. So each

(19:08):
one of these UM exoplanets is named after the star
that it orbits. Yeah. So so the Glaza Gleaz is
a star. Yeah, and it has several potential habitable planets
around it. We already talked a little bit about five
eight one G, but there's also a five eight one C.
It is twelve thousand miles in diameter UM, which is

(19:30):
not too much bigger than Earth um, and makes one
complete revolution in thirteen Earth days, which means it's too hot,
but it balances that out because it has a surface
temperature one uh that of our Sun, which means potentially,
and again this is all speculation. Potentially the temperature range

(19:52):
on the surface of five eight one C could be
thirty two degrees to two degrees fahrenheit, such as in
the wheelhouse. It isn the wheelhouse. I think further study
has kind of discarded the idea that um gleeza vibe
eight one c is habitable. Yeah, it's pretty quick right
as far as breaking news goes. But you raise a

(20:13):
really good point that if this thing has a revolution
a year that's thirteen days long, the there's no part
of the planet that's going to get cool enough to
even things out. It's gonna just stay too hot. And conversely,
if the thing has a year that lasts too long,

(20:34):
it's gonna it's not gonna get hot enough. It's gonna
stay cool. So that's another galactic habitable zone factor. Well,
I love him, man, keep them coming. I know. I
basically went and looked today. I was like, what are
the most likely habitable exoplanets? And an article from a
year ago has a top five that's different from an

(20:55):
article now, Like that's how quickly things change, right, Well,
I mean these things were all just basically theoretical, like
we assumed that, you know, a star would have planets
orbiting it, but it wasn't until the Coupler mission within
the last like ten years or so, I think it
was from the Arecibo telescope was the first confirmed exo

(21:18):
planet to be detected. And that was but once Kepler
started going, it's they started to come like hard and fast.
And once they started and people started rushing to press,
then the science is having to retract them now and
things are going from yeah, well, well there's a new
exit planet that we could just travel to now if
we wanted to to. This thing actually doesn't exist or

(21:42):
it's not really habitable. I looked. The most recent one
I found was from like three months ago and May
of this year, and they say, I believe this was
from space dot Com said that Kepler forty eight B
is the most earthlike planet yet that we've discovered. Um
it orbits a distant star in the constellation of Lira,

(22:03):
which is where Kepler is looking. Which eight B. It
gets really confusing. They need to start naming these things,
they do, you know, So four thirty eight B is
a little bit bigger than Earth, uh more heat than
Earth than what we received from the Sun though. UH.
It's small though, which means it is UM just because

(22:25):
it's twelve percent larger means it's seventy has a seventy
chance of being rocky like Earth. UH. It is four
d and seventy light years away, which is not too
bad considering some of these are thousands and thousands of
light years away. UH completes an orbit around its star
every thirty five days, which is about ten times as
fast as Earth. UM. And basically the Harvard Smithsonian Center

(22:51):
of astro UH for Astrophysics said that UM, they announced
this one along with seven other planets UM in the
same habit of ball zone. So decent chance. But UM,
like I said this this, By the time this comes out,
this may be old news and debunked. Who knows. UM.

(23:11):
There's another one that I think they discovered even more recently,
which is Kepler fifty two B and it's light years
away UM, and it is an earthlike planet. I think
it's UM like uh si larger in diameter than the
Earth UM, but it's still Earth like. It is a

(23:31):
super Earth, yes, UM. No, that automatically qualifies it as
a super Earth. So it's it's Earth size, but it's
not so big that it's like a gas giant. It's
terrestrial likely um. And it's in the Goldilocks zone for
its star um, and they're pretty excited about it. Actually.
I think the it has a mass that's five or

(23:54):
six times Earth's and so you would be you you
would feel about double your weight or you would weigh double.
Well you do here. But they think that if we
did sink colonists there, their bodies would adapt to be
like working out all the time. Um, but you would
become super strong, and if you came back to Earth

(24:16):
you could just beat everybody up. Interesting because you'd be
twice as strong. Pretty cool, huh, it'd be great. That's
the point of space travel is to find ways to
just walk around and come back and beat everybody up
on Earth. It's a bully program. That is a good question, though,
what's the point of all this? If these things are
light years away? What's what's the point? Um geez, just

(24:40):
to keep looking beyond? I mean, isn't that exploration the
whole point? I guess, because it's not like we could
colonize any of these places, well not now. But I
think that some people have an eye toward that that
the if we ever do figure out interstellar travel, um,
it would be really good to know where we could

(25:02):
go and take off our helmets and breathe. Yeah, I
think of it more in the opposite way, like you
can't stop doing stuff like this. No, I agree with
because then you've just I don't know, then you're just
you've given up. You're an isolationist. Yeah, you're adults living
on Earth and o'tre I'm just gonna die anyway. Well,
the other thing that they're looking for that that exoplanets

(25:24):
searches bring into the fold is steady the search for
estratra extra extraterrestrial intelligence or just the search for life
um elsewhere. And again, if you're looking at planets that
can sustain humans, they could conceivably sustain other types of
life as well. So we're hedging our bets for the future.

(25:45):
We're also looking to see if we're alone out there
or not. Imagine there are people out there that thinks
there's a big waste of time and money though probably
you know, whatevs. The adults, the isolationists, you got anything
else right now? Oh? This is uh, this is good.
Stuff is a little heady and it's such a rapidly
changing thing. Yeah, we could revisit this easily. Yeah, I

(26:05):
mean this will be outdated in six months. But tops, Hey,
we we like to do these topical things every now
and then. Uh, if you want to know more about
earth like planets, you can type that into the search
part how stuff forks dot com. And since I said
search parts, time for listener mail. I'm gonna call this,

(26:29):
uh road rage and no not road rage. Citizens arrest. Okay,
there's kind of a difference, big difference. Guys. Have a
citizens rest story. Um from two thousand one. I was
a naive nineteen year old behind the wheel of the
first car ever bought myself when I was rear ended. Um.
It was two thousand one, so we didn't have cell
phones and there was no phone booth nearby, so we

(26:51):
could not call the highway patrol or police. The other
driver had insurance, but did not have a valid driver's license,
only an expired one. Later found out he obtained a
license during a window time when the Governator of California
announced him to be issued to undocumented persons who had
emigrated without completing all their legal steps yet. So basically
this guy got in a window had it license at
one point it was expired. I got my crunch car

(27:14):
home that afternoon and, at the suggestion of my parents,
called the local cops to file a police report since
we couldn't do one at the scene in the accident.
The officer that came out to my home was the
most militant, sour woman in law enforcement that I have
ever had the pleasure or displeasure I'm encountering. She impatiently
asked the questions and took notes, all while sneering at me.

(27:36):
When I got to the part about the other driver
having expired license, she literally yelled at me for not
placing him under citizens arrest. Mind you, this was a
car full of men. I was a nineteen year old
girl who weighed a hundred pounds and was four ft ten,
and she chastised me for not placing an entire car
full of grown men under citizens arrest for driving on

(27:57):
an expired license. Uh. She went on about how many
undocumented persons have criminal records and can be very dangerous,
and this would have been a good opportunity to get
them deported. Well, this is an explosive listener mail. Yeah,
or a car full of potentially dangerous men. Maybe you
should not try and place under citizens rests would be
my idea. At this point, my father had enough of

(28:20):
her shenanigans and asked her to leave. That was the
end of that, but we still chuckled this day over
the absurdity of her suggestion. Uh. And she goes on
to say that the guy in the car and the
dudes were very nice, and the exchange insurance and it
wasn't like a bad scene or anything. So, um, it
just sounds like this officer was not a very nice persons. Like, yeah,

(28:42):
and every cop that we heard from after citizen arrest
said don't do it, and this lady saying, now try it.
A little four ft tin lady shot on a car
full of men, and um, all of sudden, you want
to point out that I forgot that one of the
most legendary Remember I was trying to think of famous
citizens arrests. The most legendary of all time is, uh,

(29:07):
the night Stalker. Oh yeah, he got arrested by a
citizen by citizens Like he was checked the knight Stalker
did no not him? Richard Richard Ramirez. He was recognized
out on this because they eventually found out who he
was and blasted his face out everywhere in this group
of Hispanic women saw him and started screaming in uh

(29:27):
in Spanish like night stalker, night stalker. And he was
gang piled by like fifteen people and cops had to
pull people off. He was almost beaten to death. So
I guess you would call that a citizen's arrest. I
would call that, yes, yeah, like a good one, yeah,
an effective one. Yeah, well they got a serial killer.
You always gotta feel good about that citizens arrest. Yeah.

(29:49):
I fell down the rabbit hole of reading all about
that guy recently. Yeah. Yeah, man, what a crazy time
to be living in l A. I bet people were
because there was no rhyme or reason and it was
like one night, then two nights later, than three nights later,
than two nights later, and just crazy, awful, awful things.
That was like The Zodiac, one of my favorite movies
of all times. Zodiac. It's a great movie. That was

(30:10):
a great one. But then you read ramirez is background
and it's like abusive father, Um, this crazy uncle that
was in Vietnam that showed him pictures of like decapitated bodies,
and you know, he was dropped on his head like
three times, like he had a whole list of things
that's like how to become a serial killer. And uh

(30:33):
so it's two times you're fine, that third time you
get dropped on your head, that's big. And let's not
say every head trauma leads to that, but they think
it could have something to do in cases like that.
It was just it was very sad and fascinating. Yep,
do you have a particular article you recommend on the dude? Uh? No, Okay,

(30:53):
well look, come up. Yeah, uh if you want to
let us know about your personal story of something that
has to do with what we've talked about in the past,
how's that for call action? You can tweet to us
at s y s K podcast. You can join us
on Facebook dot com, slash stuff you Should Know. You

(31:14):
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