Extrasolar planets

Although current observations suggest that Earth-size rocky planets may be common, their abundance is quite uncertain. The information to-date, however, is encouraging:

• Roughly 7 percent of all nearby stars harbor a giant planet within 3 AU.

• The number of planets increases as mass decreases towards the mass of an Earth.

• Stars that contain higher abundance of metals are more likely to have planets.

• Multiple planets are common, often in resonant orbits. • The number of planets increases with distance from the star. • Eccentric orbits are common, with only 10 percent being nearly

circular.

HW Questions 9 & 10#9 is asking you to point to evidence of ecosystem change or climate change that occurs rapidly (as in the length of a human life). The obvious things to talk about are the effects of global warming and the fact that many ecosystems are being destroyed and organisms going extinct due to human influence

#10 is asking you to research the effects of the space environment on terrestrial animals (including humans). There has been much research done on the Space Shuttle, the International Space Station, and Mir that made use of animal subjects. Also you can talk about the effects of the space environment (microgravity) and lunar (1/6 gravity) and Mars (1/3 gravity) on humans.

Wobble Method: Astrometry

Transit Photometry

Direct Imaging Method

Terrestrial Planet- finder (2012)

By combining the high sensitivity of space telescopes with revolutionary imaging technologies, the TPF observatories will measure the size, temperature, and placement of planets as small as the Earth in the habitable zones of distant solar systems.

A major goal of Terrestrial Planet Finder (TPF) mission is to provide data to the biologists andatmospheric chemists who will be best able to evaluate the observations for evidence of life.

Detection of O2 or its photolytic product O3 merits highest priority because O2 is our mostreliable biomarker gas. O3 is easier to detect at low O2 concentrations. O3 might be detected in theUV range (at 0.34 to 0.31m), but potential interferences must first be evaluated. Even thoughH2O is not a bio-indicator, its presence in liquid form on a planet’s surface is considered essentialto life. CO2 is required for photosynthesis and for other important metabolic pathways. CO2

indicates an atmosphere and oxidation state typical of a terrestrial planet. Abundant CH4 canindicate a biological source, although nonbiological sources might be detectable, depending uponthe degree of oxidation of a planet’s crust and upper mantle. A planet’s size is very important forassessing its habitability, as illustrated by comparing Earth and Mars. Planet size can be estimatedin the mid-infrared range, but not in the visible to near infrared range. Both mid-infrared andvisible to near-infrared ranges offer valuable information regarding biomarkers and planetaryproperties; therefore both merit serious scientific consideration for TPF. The best overall strategyfor the Origins Program includes a diversity of approaches, therefore both wavelength rangesshould ultimately be examined prior to launching the “Life-Finder” mission. The program mustembrace the likelihood that the range of characteristics of extrasolar rocky planets far exceeds ourexperiences with our own four terrestrial planets and the Moon.

SIM Planetquest (2011)

SIM PlanetQuest will exploit the classical measuring tool of astrometry with unprecedented precision to make dramatic advances in many areas of astronomy and astrophysics. Of particular importance to NASA's goal of searching for habitable planets will be SIM's surveys of the closest ~100 stars for planets of a few earth-masses to identify potential Earth analogs and determine their mass and orbital properties. SIM will also survey a few thousand stars of a much wider variety of ages, spectral types, and other properties than is possible with radial velocity studies to build up a complete understanding of the formation, evolution, and architecture of planetary systems generally. But the scientific return from SIM is far broader than searching for planets and will include improving our understanding of the physical properties of stars, determining the mass, including the dark matter component, and its distribution in our Galaxy, observing the motions of the Milky Way’s companions in the Local Group, and probing the behavior of supermassive black holes in other galaxies. More than half of the assigned SIM time has been allocated to astrophysics questions. A substantial share of time remains open for future assignment.