Date: January 21, 2011
Title: Finding Exoplanets, Part 2
Podcaster: Thomas Hofstätter
Organization: The Hidden Space Project :: at http://hidden-space.at.tf.
Description: This podcast discusses the topic of Exoplanets and life on other planets out of our solar system. If you have any questions, comments or suggestions to the podcast, feel free to write me an email to hidden-space (at) gmx (dot) at or visit me at my website at www.hidden-space.at.tf!
Bio: Born in 1993 near Vienna, Austria, Europe. Upper High School with focus on Computer Science.Interested in extreme small and extreme big, devious and uninvestigated things. My main aim is to bring astronomy to public and to establish secular interest in astronomy, physics and mathematics. Host of :: The Hidden Space Project :: at http://hidden-space.at.tf.
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Transcript:
Hello and welcome to this episode of 365 Days of Astronomy. My name is Thomas Hofst‰tter and I am the hoster of :: The Hidden Space Project :: at www.hidden-space.at.tf.
[Leon:] And I’m Leon Dombroski from the state of Connecticut in the United States.
In this and other episodes we are going to talk about Exoplanets. We will have a look at the origin of thinking of life in other planetary systems as well as the science and technology behind the discovery of planets like in our own solar system.
[Leon:] Exoplanets are quite hard to find around a bright shining star because they don’t emit any light, scientists on earth would be able to detect. Instead, they just reflect the light of their parents’ star. This light is very dim because the planets are in a huge distance to earth. Proxima Centauri, the closest star to earth, is about 4.2 light years away from us. That’s 7000 times the distance to (134340) Pluto.
Most times, exoplanets are so small in relation to the distance and their host star that it isn’t even possible to detect them directly in the optical or infrared part of the spectrum. Therefore, scientists have to apply other techniques. They are not looking directly for planets, but their effects on the star.
[Leon:] One effect, a planet has on its star, is the gravitational pull. Not only the star is affecting its planets, but the planets have their effect too. Indeed, two masses are rotating around the same center. If the masses are about the same, the center is in the middle between the two objects. Looking at a star and a planet, the center of rotation is located closely to the star because it’s more massive. That causes stars with a planetary system around them to sway.
Doing so, the star slightly moves toward and away from us. That causes the so-called Doppler shift of light. If the star moves away from us, the light is bent and therefore it’s shifted into the red. When the star moves towards us, the light of it is shifted toward the blue. Scientists can measure these changes taking spectra of the star and draw the conclusion that the star is orbited by at least one planet.
[Leon:] Of course, this planet has to be much more massive than earth. That’s the reason, why planets detected earlier had several times the mass of Jupiter. These planets were mostly so-called “Hot Jupiters” because they orbited their star quite close, which again makes the effect in the Doppler shift more significant.
Taking these spectra of a star also allows asking questions about the planet itself. If the planet is beside the star, you have the spectrum of the star alone. But if the planet lies in front of the star, the spectrum taken shows not only the spectrum of the star but also of the exoplanet.
[Leon:] By dividing these spectrums, scientists can get the spectrum of the planet itself. So it was with data taken with the Hubble Space Telescope in 2001. The star HD 209458 in the constellation Pegasus was the first from which scientists know it’s chemical ingredients of the atmosphere.
Not far from the detection via the measurement of the Doppler shift is the one using Astrometry. Stars having a planetary system don’t only move towards and away from us, but also move to the left and right (seen from our direction). By exactly surveying the star over a longer period of time, scientists using huge telescopes, such as the Hubble Space Telescope or the Keck Observatory on Mauna Kea are able to find exoplanets, too.
[Leon:] In 2002, the Hubble Space Telescope determined the exact mass of the exoplanet Gliese 876b orbiting the star Gliese 876 in the constellation Aquarius, of the zodiac. According to the investigations of Hubble, the planet has 1.89 to 2.4 times the mass of Jupiter. Previously, scientists only estimated 1.9 and 100 times.
That’s it for today. I hope, you enjoyed it. If you have any questions, comments or suggestions, write me an email to hidden-space (at) gmx (dot) at or visit me at my website at www.hidden-space.at.tf.
Thanks for listening and clear-skies!
[Leon:] Good bye for now!
The next storries of this series will go on air soon!
End of podcast:
365 Days of Astronomy
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