Exoplanets: Crash Course Astronomy #27

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Today Phil explains that YES, there are other planets out there and astonomers have a lot of methods for detecting them. Nearly 2000 have been found so far. The most successful method is using transits, where a planet physically passes in front of its parent star, producing a measurable dip in the star’s light. Another is to measuring the Doppler shift in a star’s light due to reflexive motion as the planet orbits. Exoplanets appear to orbit nearly every kind of star, and we’ve even found planets that are the same size as Earth. We think there may be many billions of Earth-like planets in our galaxy.

This is a reupload of last week’s episode to correct an error in the way we covered reflexive motion.
For more information on the change and reflexive motion, you can check out Phil’s blog: http://www.slate.com/blogs/bad_astronomy/2015/08/07/crash_course_astronomy_exoplanets.html

Table of Contents
Other Planets Orbit Other Stars 2:10
Nearly 2000 Have Been Found 9:29
Transits 5:44
Doppler Shift 3:30
Exoplanets Orbit Nearly Every Kind of Star 8:44
Billions of Earth-Like Planets 9:33

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Stars as viewed from ISS https://www.youtube.com/watch?v=TOQrx-7qgak [credit: Alex Rivest & NASA]
Jupiter http://www.nasa.gov/centers/goddard/multimedia/largest/Jupiter_sphere.jpg.html [credit: NASA]
Mars http://mars.jpl.nasa.gov/multimedia/images/?ImageID=2633 [credit: NASA/JPL-Caltech/MSSS]
Mercury http://solarsystem.nasa.gov/multimedia/display.cfm?Category=Planets&IM_ID=7543 [credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington]
Earth https://www.nasa.gov/topics/earth/overview/index.html [credit: NASA]
Uranus http://photojournal.jpl.nasa.gov/catalog/PIA18182 [credit: NASA/JPL-Caltech]
Lost in the Glare http://planetquest.jpl.nasa.gov/video/23 [credit: NASA Kepler Mission/Dana Berry]
Reflexive Motion gifs http://spaceplace.nasa.gov/barycenter/en/ [credit: NASA]
Artist’s conception of PSR B1257+12’s system of planets https://en.wikipedia.org/wiki/Pulsar_planet#/media/File:Artist%27s_concept_of_PSR_B1257%2B12_system.jpg [credit: NASA/JPL-Caltech/R. Hurt (SSC)]
Artist’s impression of the exoplanet 51 Pegasi b (image) http://www.eso.org/public/usa/images/eso1517a/ [credit: ESO/M. Kornmesser/Nick Risinger (skysurvey.org)]
Artist’s impression of the exoplanet 51 Pegasi b (video) http://www.eso.org/public/usa/videos/eso1517b/ [credit: ESO/M. Kornmesser/Nick Risinger (skysurvey.org)]
Kepler Transit Graph http://planetquest.jpl.nasa.gov/video/22 [credit NASA Kepler Mission/Dana Berry]
Kepler “Beauty Shot” http://planetquest.jpl.nasa.gov/video/2 [credit: NASA/Kepler mission/Dana Berry]
The Brown Dwarf 2M1207 and its Planetary Companion https://www.eso.org/public/usa/images/eso0515a/ [credit: ESO]
Beta Pictoris b http://www.eso.org/public/archives/images/screen/eso1024c.jpg [credit: ESO]
A size comparison of the planets in the Kepler-37 system and objects in the Solar System http://photojournal.jpl.nasa.gov/catalog/PIA16694 [credit: NASA/Ames/JPL-Caltech]
Water World http://planetquest.jpl.nasa.gov/video/39 [credit: NASA Kepler Mission/Dana Berry]
Earth-like World http://planetquest.jpl.nasa.gov/video/42 [credit: NASA Kepler Mission/Dana Berry]


ociv delos says:

"Hot Jupiter"

abdullah bedir says:

I want to quit my job here and be an astronomer

Batoul S says:

i am very confused.
Does every planet orbit a star? does every star have an exoplanet since the planets outnumber the stars?
Why cant we see other planets in our sky since most planets are reflective? Are there other planets orbiting the sun or is it just our solar system?

Baby Vegeta says:

wow. this is a very powerful series

Ahmed Yanaal says:

CrashCourse is love, CrashCourse is life.

ffggddss says:

Nice treatment! I like the way you cover so much ground in a limited time; and in this format, if the viewer finds that something went by too fast to catch, it can be re-rolled.

Phil, when you introduced the detection methods, it brought to mind a seminar I attended at UMd back in the 70's about Peter van de Kamp's efforts in that direction.
If I recall correctly, he was trying to detect the (very tiny!) waviness in the stars' proper motions, and I don't think he managed to bag any actual live ones — that could be confirmed, that is. Adaptive optics methods were in their infancy then; I don't think he was using those. Do you recall?

Any case, it's astonishing to me how far this effort has come in 40 years — from mere pipe dreams and ghosts of ideas, to solid detections – thousands of them!

Begs speculation about what state this will be in 40 years hence!

Sara Lejon says:

When you said you had a photo of an exoplanet, I GASPED with excitement. My favorite crash course series.

Matthew Lee says:

Sup Nate!!

natnew32 says:

1) Hot Jupiter-like planets are very close to stars 2) they formed very far out 3) when they move in, they take the inner planets with them 4) Earth is an inner planet 5) We have a Jupiter 6) Saturn stopped it from moving | in Conclusion: THANK YOU, SATURN!

constellation says:


castalderman nn says:

All this series makes me dream about how wonderful is the universe! 

TheShockerKnocker says:

I hate this bald mother fucker's facial expressions. Eat your fucking glasses cancerous bitch.

Michael Gusevsky says:

the sky is philled with planets!!

Michael Gusevsky says:

prob with detecting exo planets relies on the fact of the exo being in orbit around it's star so some time the earth exo and it's star from a line but what if rotation axis's surface is perpandicular (90 degress) to th line between the star and the earth? as said u can't meassure the reflex motion…

CanuckMonkey13 says:

I love how the script is future-proofed by having Phil say "in 2015" and not "earlier this year" or something. Just one way that this series will be useful for years to come!

Tyrannosaurus aegyptiacus 423 (Dinofan15) says:

It's actually the third biggest question in astronomy

1. The cause of big bang
2. What is on the other side of black holes
3. Are there planets orbiting other stars


why does he speak out the end credits…did those people complain that much about them not getting enough credit for their work?

surfingsuicune says:

"A good scientist wants other scientists to poke holes in their ideas."

Too bad we have so many scientists who are politically motivated or funded by governments with political agendas.

Damien Green says:

So what if the first colony to enter these worlds dies due to disease because we haven't built immunity to any of these worlds.

Sl1f3rDrag0n says:

Orphan planets?

Su hoe says:


orangejuicerox says:

Am i the only one here who watches these astronomy videos to de-stress?

Minecraftassasin77 says:

Anyone was thinking about the group EXO?

MiddleClass SeaBass says:

With that many earth-like planets I think it's a bigger statement to say there isn't intelligent life out there than it is to say there is. There's no doubt in my mind that we aren't alone.

abbieness says:

Is he rhe same guy narrating in that pther science youtube channel? The one with stick illustrations on whiteboard?

Liam Cullen says:

Love this guy. Great episode!

TheFireflyGrave says:

I had no idea that we'd found so many planets. The universe in our minds just keeps getting bigger.

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