In my last video we reviewed how to find the planets in the night sky and which five can be
seen with the unaided eye, but what I didn't talk about are the existence of planets outside of
our own solar system, and we call these bodies exoplanets. In January of 2022 when this was
recorded scientists have discovered 4,903 confirmed planets outside of our own solar system and many
of these star systems have more than one planet, and astronomers have created a group of exoplanet
types that include Earth size, and terrestrial, or super Earth's, Neptune-like, and gas giants, and
the techniques to observe these exoplanets have evolved over time, and it's a really exciting field
right now studying exoplanets. So in this video we're going to examine how exoplanets are detected,
the types of planets that exist, and what you can do to contribute to the hunt for more exoplanets.
Welcome to Learn the Sky, my name is Janine and I'll be your guide as we explore the night
sky together one constellation at a time. There are four different ways astronomers can detect
exoplanets. The first and most common method is through transit when the planet passes in front,
we have radial velocity which is also measuring the wobble of a star due to a planet going around
it, there's micro lensing by measuring how light changes but when it's focused by gravity, and then
imaging techniques. So let's look at these in a little bit more detail. So the most common
way we detect exoplanets is through transit method. So as you watch this animation notice
when there's a small planet going in front of the star there is a decrease right there but
when a bigger planet goes in front of it we see um even more of a decrease in light, which um
astronomers can detect these changes in brightness and calculate the presence of a planet or even
a family of planets. Here's another diagram of kind of how this works, you can see the planet passing
in front and the star's brightness changing over time. The next way is through radial velocity,
and as you're watching this animation notice how the star sort of wobbles side to side and that's
because of the influence of the gravity from this planet going around it, and what astronomers see
from their perspective is a shift in the stars spectrum and that's one way that we can detect
exoplanets. The third way is through microlensing, and this is when light from a distant star
it is bent and focused by gravity and this happens when the planet passes between the
star and Earth. So here you can see like two little spikes in the star's brightness. Notice that um
only two percent of the exoplanets that have been discovered thus far um have been discovered this
way, and of course these numbers are all going to change even you know after I record this because
we just keep finding more and more planets. The final way is through imaging techniques and we
can take pictures of exoplanets using techniques um that remove the glare of the stars they orbit.
So this one's really interesting. It is um a picture of this is the star HR 8799, I'll give you
some links to this below so you can read up on it, but this was taken over the course of seven years
by the Keck Observatory, and that's on top of Mauna Kea in Hawaii, it's one of my favorite places to be.
Here I'm pointing at the shadow of Mauna Kea. So I've been there lots of times and
it's always cool to see a telescope you're familiar with in the news and contributing to
two different types of sciences. So um but this star is located in the constellation of Pegasus.
It is larger than our sun, and it's estimated to be 133 light years away, and this is where that star
is located. So um only about at the time that this videos was published less than 30 exoplanets have
been discovered using this technique. So it's interesting um I find that I'm sure we'll find
that as time goes on our imaging techniques will become more sophisticated, and we'll be detecting
more and more planets around different stars that surround us.
In the next portion of this video we'll review the different categories that scientists have
created for exoplanets, and astronomers have become so adept at learning about exoplanets
that they can measure surface temperatures, magnetic fields,
orbits, and even their colors, and as technology and detection methods improve
and become more sophisticated they will be able to get even more data about these far-off worlds, and
this kind of gives you a nice overview. This is a little dated because now we're up to 4,903
for this confirmed exoplanets, but what it does is it gives you a distribution of the types
of planets we have detected. So neptune-like gas giants are the most common, as well as super earths,
we have found some terrestrial smaller rocky planets, and some were just not sure about.
Here are just another um I captured this image from the NASA website about exoplanets, which
I'm going to share with you in the next portion of the video because it's such a good resource,
but here you can see gas giants, neptune-like, super earths which may be potentially rocky planets but
much bigger than bigger than our own earth, and then smaller terrestrial planets like earth.
So that's the types we've detected, this probably could change in the future if you're watching this
months or years later as we continue to detect more exoplanets out there, and I'm not going to
go into the specifics of exoplanets, there's just really too much to uncover here that this video
is really just an introduction to the incredibly diverse planets that exist in our universe, but I
am gonna share with you the resources I recommend for you to check out, and these include NASA Eyes
on the Exoplanet, I'll get that get to that in the next section, Spitzer Space Telescope,
and Tess which is um stands for Transiting Exoplanet Survey Satellite, try saying
that five times fast, but this mission is meant to detect exoplanets, and then we'll talk about
how to contribute as a citizen science through zunifers.org, you can take a look at different
transit data and help classify it for different scientific projects that are out there. The first
resource I want to share with you is NASA's exoplanet website which is exoplanets.nasa.gov.
I'll put the link down in the description below, but this is a great website to explore.
It shows you how many planets have been confirmed, which ones are waiting to be confirmed, and then
how many planetary systems exist out there, and you can scan through this but my favorite is this
right here. Eyes on Exoplanets, so if I flip over to that what you can do is you can scan through
all the different stars and when you click on a star it'll tell you what the name of it is,
and you can go to that system, and what this shows you is the star, okay, so this is a a red dwarf star,
an M-type star, it's the most common that's out there, they're more red and cooler and dimmer than
our sun, but here's what the system looks like. In this green area if I toggle it on and off
this is the zone, the Goldilocks zone like where life can exist according to our estimates at this
time, and then we can zoom in on the planet and it gives you this hypothetical visualization that
you can look at, and this is just an incredible resource. You can get lost on here for hours,
and I did, I was like 'I have to get back to making this video,' but it's so much fun to explore,
it tells you how far away you are. So this is just an incredible tool for you to use and
explore, so you can, this is a zoomed out as far as you can go, and then oh no I lie, you can go
out you can go in, but this um you can also look at the missions, which is what we talked about, the um
you know where these are right now, discovered, confirmed, this i'm not gonna keep going here
this is just um you can get lost on here and I definitely encourage you to check this website out.
Another great resource to explore is NASA's website about the Spitzer Space Telescope.
This was a space-based infrared observatory, and it was in operation for 16 years. It was
decommissioned in January of 2020, but scientists are still learning about all kinds of exoplanets
from the archive data from this mission. So it actually its mission went on longer than it
was originally predicted, so I encourage you to explore this website and the science behind this
particular telescope. You can also explore the TESS website, which is again Transiting Exoplanet Survey
Satellite, and learn more about the different types of atmospheres that are being detected on planets
and all the information that we have learned about so far, and then my final suggestion is if you want
to contribute at all to the hunt for exoplanets and help scientists process data you can be a
citizen scientist, and for me I usually go to xonoverse.org. I have some other videos about
the different projects, the astronomy projects on here, but this one in particular is called
planet hunters, right there, and what you do is you help scientists classify the data that they see
from transits of planets in front of other stars, and it gives you a tutorial it walks you through
what what the tools are and what how they're collecting this data through 12 8-inch telescopes,
and it teaches you goes through all the science, you can read this on your own of course but
it teaches you how to classify the different transit curves that we see here, and I was doing
this before I was recording this video and it was pretty easy to go through, and of course
I usually read through about this project so I know exactly what it is, and then I would have my
own students in my classroom work on on this data too. It just gives them a little bit of experience
trying to discover you know just being the discoverer like scientists are. So those are my
recommendations for you, and of course my favorite is the Eyes on Exoplanets. It's just so much fun to
explore this. I feel like every time I go in here I'm finding a different
system that I didn't know existed, and you can look of course at the planet and what
it's expected to look like based upon current data. You can look at its system,
and of course you can zoom in on the star, which this one's not quite going, there it
is, okay. So this is a K-type star, an orange star. So anyway I hope this was helpful for
you to learn a little bit more about exoplanets. I'm not going to of course redo the brilliance
of NASA and everything they have to offer, so if you really want to learn more you have to go
to these websites. They're so much fun to explore. So I wish you luck and as always keep looking up!