Summary january 11 2006
Download
1 / 32

Summary January 11 2006 - PowerPoint PPT Presentation


  • 49 Views
  • Uploaded on

Summary January 11 2006. The wobble technique assumes that a star will physically be perturbed by the orbit of a planet around it and the resulting motion of the star’s spectral lines can be observed. The wobble technique has been the most successful to date in finding exoplanets.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Summary January 11 2006' - buzz


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Summary january 11 2006
Summary January 11 2006

  • The wobble technique assumes that a star will physically be perturbed by the orbit of a planet around it and the resulting motion of the star’s spectral lines can be observed.

  • The wobble technique has been the most successful to date in finding exoplanets.

  • Most of the exoplanets are large Jupiter sized planets orbiting very close to the parent star. This is not surprising as the wobble technique will preferentially first see those planets that are very massive and with small orbital distances. This called a selection effect.

  • Even though the 170 ish planets found to date have all been much larger than Earth (or any terrestrial world) this is not to say Earth-sized worlds cannot exist around these stars. Rather more time and greater observational accuracy will be needed to detect these worlds.

  • Other exoplanet detection techniques include Pulsar Timing, Dust-disk warping and Optical Interfermoetry.

  • Of these techniques, the optical interfermoetry offers the best opportunity to directly observe an exoplanet. This technique has the potential to yield unprecedented resolution, accuracy needed to be able to distinguish a planet from its parent star.

  • Space based missions in the near future will include the Terretrial Planet Finder (TPF) mission, Kepler and the Space Interferometry Mission (SIM).

  • Based upon the current detection of exoplanets, it seems that something like 5% (minimum) of all Sun-like stars possess planets (Jupiter size) and there are something like 20 billion Sun-like stars in the Milky Way galaxy. This up to 1 billion planetary systems seem probable in our galaxy. This suggests that as many as 100 million terrestrial worlds likely exist.


By exploring the planets astronomers uncover clues about the formation of the solar system
By exploring the planets, astronomers uncover clues about the formation of the solar system

  • The star we call the Sun and all the celestial bodies that orbit the Sun

    • including Earth

    • the other eight planets

    • all their various moons

    • smaller bodies such as asteroids and comets




Astronomers use angles to denote the positions and apparent sizes of objects in the sky
Astronomers use angles to denote the positions and apparent sizes of objects in the sky

  • The basic unit of angular measure is the degree (°).

  • Astronomers use angular measure to describe the apparent size of a celestial object—what fraction of the sky that object seems to cover

  • The angular diameter (or angular size) of the Moon is ½° or the Moon subtends an angle of ½°.


If you draw lines from your eye to each of two stars, the angle between these lines is the angular distance between these two stars



Angular measurements
Angular Measurements of estimating angles

  • Subdivide one degree into 60 arcminutes

    • minutes of arc

    • abbreviated as 60 arcmin or 60´

  • Subdivide one arcminute into 60 arcseconds

    • seconds of arc

    • abbreviated as 60 arcsec or 60”

      1° = 60 arcmin = 60´

      1´ = 60 arcsec = 60”


It is convenient to imagine that the stars are located on a celestial sphere
It is convenient to imagine that the stars are located on a celestial sphere

  • The celestial sphere is an imaginary object that has no basis in physical reality

  • However it is still a model that remains a useful tool of positional astronomy

  • Landmarks on the celestial sphere are projections of those on the Earth


Parallax
Parallax celestial sphere


The small angle formula
The Small Angle Formula celestial sphere

D = linear size of object

a = angular size of object (in arcsec)

d = distance to the object


Astronomical distances are often measured in astronomical units parsecs or light years
Astronomical distances are often measured in astronomical units, parsecs, or light-years

  • Astronomical Unit (AU)

    • One AU is the average distance between Earth and the Sun

    • 1.496 X 108 km or 92.96 million miles

  • Light Year (ly)

    • One ly is the distance light can travel in one year at a speed of about 3 x 105 km/s or 186,000 miles/s

    • 9.46 X 1012 km or 63,240 AU

  • Parsec (pc)

    • the distance at which 1 AU subtends an angle of 1 arcsec or the distance from which Earth would appear to be one arcsecond from the Sun

    • 1 pc = 3.09 × 1013 km = 3.26 ly


Eighty eight constellations cover the entire sky
Eighty-eight constellations cover the entire sky units, parsecs, or light-years

  • Ancient peoples looked at the stars and imagined groupings made pictures in the sky

  • We still refer to many of these groupings

  • Astronomers call them constellations (from the Latin for “group of stars”)


Modern constellations
Modern Constellations units, parsecs, or light-years

  • On modern star charts, the entire sky is divided into 88 regions

  • Each is a constellation

  • Most stars in a constellation are nowhere near one another

  • They only appear to be close together because they are in nearly the same direction as seen from Earth


Ancient astronomers invented geocentric models to explain planetary motions
Ancient astronomers invented geocentric models units, parsecs, or light-yearsto explain planetary motions

  • Like the Sun and Moon, the planets move on the celestial sphere with respect to the background of stars

  • Most of the time a planet moves eastward in direct motion, in the same direction as the Sun and the Moon, but from time to time it moves westward in retrograde motion


If a star s distance is known its luminosity can be determined from its brightness
If a star’s distance is known, its luminosity can be units, parsecs, or light-yearsdetermined from its brightness

  • A star’s luminosity (total light output), apparent brightness, and distance from the Earth are related by the inverse-square law

  • If any two of these quantities are known, the third can be calculated


Wavelength and frequency
Wavelength and Frequency units, parsecs, or light-years


The nature of light
The Nature of Light units, parsecs, or light-years

  • In the 1860s, the Scottish mathematician and physicist James Clerk Maxwell succeeded in describing all the basic properties of electricity and magnetism in four equations

  • This mathematical achievement demonstrated that electric and magnetic forces are really two aspects of the same phenomenon, which we now call electromagnetism




Kirchhoff s laws
Kirchhoff’s Laws also called


ad