lecture_tan36 - Key Concepts Lecture 36 The Search for...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Key Concepts: Lecture 36: The Search for Planets and Life Transit Technique The Habitable Zone Estimates from Drake Equation SETI and Fermi’s Paradox Planet Search Techniques Planet Searches: (Many more extrasolar planets are now known than there are planets in our own solar system) 1. Radial velocity search: gravity of planet causes star to wobble. Look for the blue and redshift of spectral lines from the star Most sensitive to massive planets that are close to their stars detected >~500 planets to date 2. Transit Search A planet passes in front of its star. We see a small dip in the brightness of the star. If we know the size of the star, we can then measure the size of the planet. Depth of Transit Depends on Relative Sizes of Star and Planet Transit search technique measures the size of the planet (if we already know the size of the star)
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
First Planetary Transit Detected in year 1999 Star is called HD209458 Radius of planet is 1.3 times Jupiter’s radius Mass of planet (from radial velocity technique) is 0.63 times Jupiter’s mass Why is the planet so big? Probably because it is so close to its star, is strongly heated, and so is puffed up. 3. The Microlensing Technique Microlensing is when a star (the Lens star) passes in front of a background star (the Source star) and acts as a gravitational lens, bending the light to our telescopes (recall Einstein’s General Relativity). This causes the source star to appear to brighten and then fade over time (see fig. on right). If the lens star has a planet, this can cause an extra blip in the magnification. This method is good at finding small planets that are far from their star (in contrast to the radial velocity method). But it requires monitoring millions of source stars and generally the planets that are found are so far away from us they are difficult to study further with other techniques.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern