How to Find an Exoplanet

How to Find an Exoplanet

This episode of Real Engineering is brought
to you by Skillshare, home to over 20,000 classes that could teach you a new life skill. Staring at the sky in awe is one of the few
quintessential human experiences. Gazing into the vast emptiness of space wondering
where our place in the universe stands. For millennia the mystery of these celestial
bodies captivated the human mind, seeding religions and mythical stories. We couldn’t ignore the moon above us, influencing
our tides, or the sun, our benevolent provider, burning in the blue sky. At night, individual stars melded together
into a boundless blanket of glittering light, until we began to notice patterns in their
chaos, guiding us as we explored our world. These star maps helped us make a monumental
discovery, some stars in the sky moved differently to others. Wandering through the night sky, planets like
ours orbiting our sun. Mercury, Venus, Mars, Jupiter and Saturn,
all visible to the naked eye were discovered this way by ancient babylonian astronomers
over 4 thousand years ago. Later Galileo improved the telescope, allowing
him to observe even fainter points in the sky, invisible to the naked eye. He discovered Jupiter’s moons. Ganymede, Callisto, Io and Europa and Saturn’s
moons soon followed mostly discovered by Cassini. Uranus & Neptune had been observed numerous
times through telescopes, but astronomers continually mistook them them for stationary
stars or comets. It was only when astronomers noticed the circular
orbit of Uranus that it was accepted as a planet. Then as it’s orbit was further examined
astronomers noticed deviations, that could only be caused by a nearby planet, and thus
Neptune, our solars systems final planet, was discovered *on screen joke – Sorry Pluto* It tooks thousands of years to just discover
the planets in our solar system, but in the last 30 years we have discovered over 3717
planets orbiting stars so far away that we will never be able to visit them with current
technology. Perhaps the most fascinating planetary system
we have discovered is that of Trappist-1, an ultra-cool dwarf star located 40 light
years away from our Sun, which has not only 1 temperate terrestrial planet, but 7. Each of the planets are rocky and between
the size of Earth and Mars. The star is small and cold compared to ours,
but the planets orbit so closely to the star, closer than mercury orbits the Sun, that they
all have the possibility of containing liquid water. This is a lot of information about planets
that we can’t even see directly. So how do present day astronomers find these,
relatively speaking, tiny objects floating in space? The first planets discovered orbiting this
star were discovered by a Belgian team using the Trappist-south telescope located high
the Chilean mountains. The team had their telescope trained on the
dwarf star waiting for a dimming of it’s light, a tell tale sign of a planet in orbit
passing in front of the star, and thus blocking some of it’s light. But how have we discovered so much about this
system, simply by a dimming of light in its star? If we calculate the distance to the star,
using the parallax method, we can discover a lot more about the planets passing in front
of it. You can see how the parallax method works
right now by holding your thumb in front of you with one eye open. Now close that eye and open the other. Did you notice it appeared to move relative
to the background, this is called parallax and we can use it to measure the distance
to a star, but instead of closing our eyes and staring
at the sky, we take measurements of the planets position from opposite sides of our orbit
around the sun.We know the distance between these two points, and we can measure the change
in the stars position relative to distant stars behind it, giving us the parallax angle,
thus we have all the information we need to calculate the distance to the star using some
simply trigonometry. Now that we know the distance to the star,
we can calculate its mass and size by observing its apparent brightness and temperature observed
from earth. We have models for how stars form, with massive
stars being hotter and brighter than smaller stars, and so by measuring these values we
can get a lot of information about the star. That’s how we know Trappist-1 is an ultra-cool
dwarf star. Now that we know more about the star, we discover
what we are really interested in. The planets size, mass, and whether it resides
in the goldilocks zone where humans could survive. To do that we need to know how far away the
planet is from the star. We do this using
Kepler’s Third Law which looks like this. It tells us the orbital period for planet,
that’s how long it takes to orbit it’s star. Here G is the Newton’s Gravitational Constant,
capital M is the Star’s mass, lowercase m is the planet’s mass, and a is the orbital
radius. We can ignore the planet’s mass for now,
as it’s miniscule compared to the star’s. If we do this for Earth, it introduces an
error of just 0.001%. The period is measured by seeing the time
between transits, and so we have all the variables we need to calculate the orbital radius. Now that we know how far away the planet is,
figuring out it’s diameter from the transit dimming is simple. The next bit of information gathering requires
a bit of a perspective shift. We are used to the idea that planets orbit
a star, but it would be more accurate to say that the planet and star orbit the centre
of mass of the star-planet system, which is not at the centre of the star. This means the planet’s mass is actually
impacting the orbit of the star around this point. The larger the mass of the planet the larger
the deviation. We can measure the magnitude of this deviation
by detecting the doppler shift in the stars light frequency. As the star moves towards us the light becomes
slightly more blue, and when the star moves away from us it becomes slightly more red. Using the law of conservation of momentum
we can easily calculate the mass of the planet. We know the velocity of the planet from orbital
radius and period measurements, the mass of the Star from our distance and luminosity
measurements, and the velocity of the sun is measured from these doppler shifts in the
light frequency. Leaving us with all the information we need
to calculate the mass of the planet. Using these tools Astronomers have inferred
quite a lot of information about these planets. The 7 planets orbit so closely to their star
that a year ranges from just 1.5 days for the innermost planet to 20 days for the outermost
planet. They are so close packed that the planets
will at times appear in each others sky, larger than our moon appears in ours. Maybe the coolest part of the entire thing,
is the planetary system is named after the beer the scientist used to toast their discovery. But it isn’t all good news, because they
orbit so close, many of the planets will be tidally locked, like our moon is to the earth,
meaning one side of the planet will constantly face the sun. Which may restrict life to the terminator,
the narrow band of perpetual twilight. On top of this, orbiting this closely to a
dwarf star exposes it to radiation from solar flares, which can strip it’s atmosphere
away, especially if it is not protected by a strong magnetic field like earth. For now, we don’t have a lot of information
on these planets, beyond their position, period and mass. But we’ll know more soon, as the James Webb
Telescope will be able to give us more information about the atmosphere on these planets by observing
the light that shines through their atmosphere during transit. By examining the spectrum of light coming
through the atmosphere we can discover what gases are in its atmosphere. Here we have the spectroscopy analysis of
Venus, Earth and Mars. All have the fingerprints of carbon dioxide
in their atmosphere, while only Earth has the traits of an atmosphere rich in ozone
and water. If we see results like these coming from any
of the Trappist-1 planets, a world wide toast with Belgian beers may be in order. Learning how astronomers discover our universe
is fascinating, but it’s unlikely you will ever have the tools to discover your own worlds,
but you can explore the world you stand on and its night time sky using fairly inexpensive
equipment to produce incredible photos like this. You can learn how to do this using this course
on Skillshare, which will teach you how to find the best times of month plan your shoot,
how to find dark areas near your location, how to identify and plan the stars you will
photograph and how to set up your equipment. This is probably my favourite course I have
taken on Skillshare to date, and I bet you will like it too. These days you can teach yourself pretty much
any skill online and Skillshare is a fantastic place to do it. With professional and understandable classes,
that follow a clear learning curve, you can dive in and start learning how to do the work
you love. .
A Premium Membership begins around $10 a month for unlimited access to all courses, but the
first 1000 people to sign up with this link will get their first 2 months for free. So ask yourself right now. What skill have you been putting off learning. What project have you been dreaming of completing,
but you aren’t sure if you have the skills to do it. Why not start right now and sign up to Skillshare
using the link below to get your first 2 months free. You have nothing to lose and a valuable life
skill to gain. As usual thanks for watching and thank you
to all my Patreon supporters. If you would like to see more from me, the
links to my twitter, facebook, discord server, subreddit and instagram pages are below.

100 thoughts on “How to Find an Exoplanet

  1. Just shared a wee preview to my first "vlog" on instagram, which will be going up on my personal channel later this month. Check it out. It's 10/10 hipster shit.

  2. Imagine if life was alive on one of those planets. It would have a vast amount of time to evolve. That would be a great history to find out

  3. Add our ability to calculate the radius of an exoplanet by measuring the magnitude of the dip in the brightness curve of the star, and this video would be a complete 101!

  4. The total number of 'earth-like' planets we know about is 1. And we're sitting on it. Just because a planet is in a zone where theoretically there is a possibility of liquid water – it is not 'earth-like.'

  5. Great video. Thanks! While we are looking for intelligent life 'out there', the Allies of Humanity reveal that extraterrestrial races are on and around our world, today and that contact and 'intervention' has been ongoing for several decades.

  6. I see that your Squarespace website has expired:
    :'( Please don't die out! If you need a new option for a website, I can happily host your website on my server for free – but you'll need to build it – I can setup a basic WordPress instance if that works for you!

  7. Can you give me any good ideas for my EPQ (Extended Project Qualification). I aspire to be an engineer one day so a solid EPQ question can help out a lot.

  8. You really deserve a billion subscribers , your channel grew up so quickly , I've seen it growing the whole way to 1 million subscribers ,your work is commendable. Love your channel a lot and respect your effort . 🙂

  9. How about getting to one without traveling so fast that time passes on Earth and everyone that knew about the venture dies?

  10. a red dwarf is not ultra cold, only a white dwarf might be called like that. they got a surface temperature of less than 4k K, while our sun has 5k…

  11. every time he says sterr… drink a shot! and till the end of the video you will also find many exoplanets

  12. I don't expect anyone can easily answer this but…
    I see how the description of calculating A planet's mass would work- but not with a system of MULTIPLE planets all in different positions. This would seem to be a difficult if not impossible remote calculation, and thus my skepticism about any accurate hypothesis on the star's overall planetary condition.

  13. Great vid! I have one question, however. In science class I was taught that the first exoplanets were discovered around pulsars by using the doppler effect. Pulsars rotate very quickly and emit radio waves at consistent frequencies, allowing scientists to detect changes in the frequency of these waves due to the star shifting due to orbiting the center of mass alongside a planet due to the doppler effect. Pulsars are essentially the ultra-dense cores of stars many times the mass of our sun and do not emit visible light, and thus the systems that they are a part of are not comparable to our own solar system. Just for clarification, did you leave this method out of the video because the pular systems are not as comparable to our solar system because the sun isn't a pulsar? Thanks!

  14. Your best chance as a random person with internet access to get a planet named after you is to play Eve Online's exoplanet minigame Planet Discovery. It's a citizen science project where individuals must identify transits based off noisy light intensity samples that some European astronomers think humans can process faster than computers. It's free to play as well.

  15. Ancient Indians knew the number of planets even thousand of years ago. In India we consider "Nava Graha", Nava = Nine and Graha=Planets, but the western civilization call us Third world… this concept of 9 Planets has been even considered as demigods and so there are hundreds of references of 9 planets in indian historical scripts..

  16. I know you probably have a plan and i do understand, but is it possible for you to do a video on nuclear missles and hoe they work, the explosion and the rocket. I would find it interesting. Good video by the way.

  17. why west ignores the fact that eastern civilizations too discovered the planets way before 4000 years? there white propaganda is running at it's best.

  18. why not take resources like metals and water from syars and other planets since the earth s resoirces are runnning out

  19. So 98% of Nasa tells us are just on their calculations and Theory.. No 100% real proof? Damn. Hahaha

  20. 90 percent of the stuff flew over my head but the 10 percent I understood was really fascinating

  21. If anyone wants to see an excellent video series on the history of discovering Uranus, Neptune, Pluto, Eris, and the origins of the Planet X theory, check out ParallaxNick on youtube. I'm an astrophysicist and I learned an enormous number of new facts from that guy. I can't recommend him enough. He tells it more like a story than a documentary, and his descriptions of not only the scientists and their achievements, but also their quirky character traits really gives it that human touch that a lot of history videos are missing. The first one is called The Strange History of Planet X Part One: Uranus.

    He also has had health issues and economic hardship recently, so I'm sure any support for his channel would be appreciated immensely.

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