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Results for “extrasolar planet detection”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
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NASA NTRS1990

On the feasibility of detecting extrasolar planets by reflected starlight using the Hubble Space Telescope

The best metrology data extant are presently used to estimate the center and wing point-spread function of the HST, in order to ascertain the implications of an observational criterion according to which a faint source's discovery can occur only when the signal recorded near its image's location is sufficiently larger than would be expected in its absence. After defining the maximum star-planet flux ratio, a figure of merit Q, defined as the contrast ratio between a 'best case' planet and the scattered starlight background, is introduced and shown in the HST's case to be unfavorable for extrasolar planet detection.

Brown, Robert A.↗
NASA NTRS1974

Use of the moon and the large space telescope as an extrasolar planet detection system

Roman (1959), Spitzer (1962), and Huang (1973) have discussed photometric detection of extrasolar planets using a 3-m space telescope such as the Large Space Telescope (LST). A space telescope could be an extrasolar planet detection system if used in conjunction with an occulter placed 10,000 km in front of the telescope. The occulter would reduce the amount of light received from the star under observation. For a semi-infinite plane occulter 10,000 km in front of the telescope, Spitzer and Huang's results indicate that a Jupiter-like planet would be observed with a signal/noise of 1.00, for observations at 0.4 micron using a 3-m telescope like the LST.

Matloff, G. L.↗
NASA NTRS1989

Fabrication experiments on supersmooth optics for extrasolar planet detection

The direct detection of extrasolar planets by imaging will require reductions in scattered and diffracted light by factors in excess of 1000 within one arcsecond of a bright source. While diffraction can be reduced by a number of approaches, small angle scatter can only be reduced by controlling midspatial frequency figure errors. The surface requirements are reviewed and their meaning when compared to the data base of existing mirrors is considered. Experiments are discribed that were successful in reducing midspatial frequency figure so that the scatter level was 500 times less than diffraction for a 25-cm spherical mirror.

Ftaclas, C.↗
NASA NTRS1994

Extrasolar planet detection

This paper discusses the concept of extrasolar planet detection using a large-aperture infared imaging telescope. Coronagraphic stellar apodization techniques are less efficient at infrared wavelengths compared to the visible, as a result of practical limitations on aperture dimensions, thus necessitating additional starlight suppression to make planet detection feasible in this spectral domain. We have been investigating the use of rotational shearing interferometry to provide up to three orders of magnitude of starlight suppression over broad spectral bandwidths. We present a theoretical analysis of the system performance requirements needed to make this a viable instrument for planet detection, including specifications on the interferometer design and telescope aperture characteristics. The concept of using rotational shearing interferometry as a wavefront error detector, thus providing a signal that can be used to adaptively correct the wavefront, will be discussed. We also present the status of laboratory studies of on-axis source suppression using a recently constructed rotational shearing interferometer that currently operates in the visible.

Korechoff, R. P.↗
NASA NTRS1989

IBIS: An Interferometer-Based Imaging System for Detecting Extrasolar Planets with a Next Generation Space Telescope

The direct detection of extrasolar planetary systems is a challenging observational objective. The observing system must be able to detect faint planetary signals against the background of diffracted and scattered starlight, zodiacal light, and in the IR, mirror thermal radiation. As part of a JPL study, we concluded that the best long-term approach is a 10-20 m filled-aperture telescope operating in the thermal IR (10-15 microns). At these wavelengths, the star/planet flux ratio is on the order of 10(exp 6)-10(exp 8). Our study supports the work of Angel et al., who proposed a cooled 16-m IR telescope and a special apodization mask to suppress the stellar light within a limited angular region around the star. Our scheme differs in that it is capable of stellar suppression over a much broader field-of- view, enabling more efficient planet searches. To do this, certain key optical signal-processing components are needed, including a coronagraph to apodize the stellar diffraction pattern, an infrared interferometer to provide further starlight suppression, a complementary visible-wavelength interferometer to sense figure errors in the telescope optics, and a deformable mirror to adaptively compensate for these errors. Because of the central role of interferometry we have designated this concept the Interferometer-Based Imaging System (IBIS). IBIS incorporates techniques originally suggested by Ken Knight for extrasolar planet detection at visible wavelengths. The type of telescope discussed at this workshop is well suited to implementation of the IBIS concept.

Diner, David J.↗
NASA NTRS1994

The photometric method of extrasolar planet detection revisited

We investigate the geometry concerning the photometric method of extrasolar planet detection, i.e., the detection of dimunition of a parent star's brightness during a planetary transit. Under the assumption that planetary orbital inclinations can be defined by a Gaussian with a sigma of 10 deg centered on the parent star's equatorial plane, Monte Carlo simulations suggest that for a given star observed at an inclination of exactly 90 deg, the probability of at least one Earth-sized or larger planet being suitably placed for transits is approximately 4%. This probability drops to 3% for a star observed at an inclination of 80 deg, and is still approximately 0.5% for a star observed at an inclination of 60 deg. If one can select 100 stars with a pre-determined inclination equal or greater than 80 deg, the probability of at least one planet being suitably configured for transits is 95%. The majority of transit events are due to planets in small-a orbits similar to the Earth and Venus; thus, the photometric method in principle is the method best suited for the detection of Earthlike planets. The photometric method also allows for testing whether or not planets can exist within binary systems. This can ge done by selecting binary systems observed at high orbital inclinations, both eclipsing binaries and wider visual binaries. For a 'real-world' example, we look at the alpha Centauri system (i = 79.2 deg). If we assume that the equatorial planes of both components coincide with the system's orbital plane, Monte Carlo simulations suggest that the probability of at least one planet (of either component) being suitably configured for transits is approximately 8%. In conclusion, we present a non-exhaustive list of solar-type stars, both single and within binary systems, which exhibit a high equatorial inclination. These objects may be considered as preliminary candidates for planetary searches via the photometric method.

Hale, Alan↗
NASA NTRS1980

Project Orion: A Design Study of a System for Detecting Extrasolar Planets

A design concept for a ground based astrometric telescope that could significantly increase the potential accuracy of astrometric observations is considered. The state of current techniques and instrumentation is examined in the context of detecting extrasolar planets. Emphasis is placed on the direct detection of extrasolar planets at either visual or infrared wavelengths. The design concept of the imaging stellar interferometer (ISI), developed under Project Orion, is described. The Orion ISI employs the state-of-the-art technology and is theoretically capable of attaining 0.00010 arc sec/yr accuracy in relative astrometric observations.

Black, D. C.↗
NASA NTRS1988

Systematic aspects of direct extrasolar planet detection

Using the first optical observatory in space, the Hubble Space Telescope, images of possible extrasolar planets will have poor contrast against the background of diffracted and scattered starlight. The very long exposure time required to achieve an adequate signal-to-noise ratio will make their detection infeasible. For a future telescope, a 16-fold increase in either the smoothness of the collecting area of the optics would reduce the exposure time to a tolerable value, but the contrast would remain low and the required photometric precision high. In this situation, the feasibility of detection would be contingent on the careful identification and control of systematic errors.

Brown, Robert A.↗
NASA NTRS1976

Optical techniques for the detection of extrasolar planets - A critical review

Proposed optical techniques of extrasolar planet detection are discussed and compared. These include terrestrial, orbital, and moon-based systems. Terrestrial systems include ground-level searches for random eclipses of primaries and 'light' echoes of stellar flares from companion planets as well as balloon-mounted telescopes operating in the stratosphere used in conjunction with orbital occulters. Space telescopes considered are multimirror systems simulating huge mirror diameters and single-mirror telescopes, such as the 3-meter Large Space Telescope, used in conjunction with occulters. Although very modest systems are capable of detecting extrasolar planets, the amount of information we can gather regarding these worlds is a function of system complexity and program duration.

Matloff, G. L.↗
NASA NTRS1998

The Kepler Mission: Search for Habitable Planets

Detecting extrasolar terrestrial planets orbiting main-sequence stars is of great interest and importance. Current ground-based methods are only capable of detecting objects about the size or mass of Jupiter or larger. The difficulties encountered with direct imaging of Earth-size planets from space are expected to be resolved in the next twenty years. Spacebased photometry of planetary transits is currently the only viable method for detection of terrestrial planets (30-600 times less massive than Jupiter). This method searches the extended solar neighborhood, providing a statistically large sample and the detailed characteristics of each individual case. A robust concept has been developed and proposed as a Discovery-class mission. Its capabilities and strengths are presented.

Borucki, William↗
NASA NTRS1999

Remote Thermal IR Spectroscopy of our Solar System

Indirect methods to detect extrasolar planets have been successful in identifying a number of stars with companion planets. No direct detection of an extrasolar planet has yet been reported. Spectroscopy in the thermal infrared region provides a potentially powerful approach to detection and characterization of planets and planetary systems. We can use knowledge of our own solar system, its planets and their atmospheres to model spectral characteristics of planets around other stars. Spectra derived from modeling our own solar system seen from an extrasolar perspective can be used to constrain detection strategies, identification of planetary class (terrestrial vs. gaseous) and retrieval of chemical, thermal and dynamical information. Emission from planets in our solar system peaks in the thermal infrared region, approximately 10 - 30 microns, substantially displaced from the maximum of the much brighter solar emission in the visible near 0.5 microns. This fact provides a relatively good contrast ratio to discriminate between stellar (solar) and planetary emission and optimize the delectability of planetary spectra. Important molecular constituents in planetary atmospheres have rotational-vibrational spectra in the thermal infrared region. Spectra from these molecules have been well characterized in the laboratory and studied in the atmospheres of solar system planets from ground-based and space platforms. The best example of such measurements are the studies with Fourier transform spectrometers, the Infrared Interferometer Spectrometers (IRIS), from spacecraft: Earth observed from NIMBUS 8, Mars observed from Mariner 9, and the outer planets observed from Voyager spacecraft. An Earth-like planet is characterized by atmospheric spectra of ozone, carbon dioxide, and water. Terrestrial planets have oxidizing atmospheres which are easily distinguished from reducing atmospheres of gaseous giant planets which lack oxygen-bearing species and are characterized by spectra containing hydrocarbons such as methane and ethane. Spectroscopic information on extrasolar planets thus can permit their classification. Spectra and spectral lines contain information on the temperature structure of the atmosphere. Line and band spectra can be used to identify the molecular constituents and retrieve species abundances, thereby classifying and characterizing the planet. At high enough spectral resolution characteristic planetary atmospheric dynamics and unique phenomena such as failure of local thermodynamic equilibrium can be identified. Dynamically induced effects such as planetary rotation and orbital velocity shift and change the shape of spectral features and must be modeled in detailed spectral studies. We will use our knowledge of the compositional, thermal and dynamical characteristics of planetary atmospheres in our own solar system to model spectra observed remotely on similar planets in extrasolar planetary systems. We will use a detailed radiative transfer and beam integration program developed for the modeling and interpretation of thermal infrared spectra measured from nearby planet planets to generate models of an extra-solar "Earth" and "Jupiter". From these models we will show how key spectral features distinguish between terrestrial and gaseous planets, what information can be obtained with different spectral resolution, what spectral features can be used to search for conditions for biogenic activity, and how dynamics and distance modify the observed spectra. We also will look at unique planetary phenomena such as atmospheric lasing and discuss their utility as probes for detection and identification of planets. Results of such studies will provide information to constrain design for instrumentation needed to directly detect extrasolar planets.

Kostiuk, Theodor↗
NASA NTRS1996

Astrometric Detection of Extrasolar Planets: Results of a Feasibility Study with the Palomar 5 Meter Telescope

The detection of extrasolar planets around stars like the Sun remains an important goal of astronomy. We present results from Palomar 5 m observations of the open cluster NGC 2420 in which we measure some of the sources of noise that will be present in an astrometric search for extrasolar planets. This is the first time that such a large aperture has been used for high-precision astrometry. We find that the atmospheric noise is 150 micro-arcsec hr(exp 1/2) across a 90 sec field of view and that differential chromatic refraction (DCR) can be calibrated to 128 micro-arcsec for observations within 1 hr of the meridian and 45 deg of zenith. These results confirm that a model for astrometric measurements can be extrapolated to large apertures. We demonstrate, based upon these results, that a large telescope achieves the sensitivity required to perform a statistically significant search for extra solar planets. We describe an astrometric technique to detect planets, the astrometric signals expected, the role of reference stars, and the sources of measurement noise: photometric noise, atmospheric motion between stars, sky background, instrumental noise, and DCR. For the latter, we discuss a method to reduce the noise further to 66 micro-arcsecond for observations within 1 hr of the meridian and 45 deg of zenith. We discuss optimal lists of target stars taken from the latest Gliese & Jahreiss catalog of nearby stars with the largest potential astrometric signals, declination limits for both telescope accessibility and reduced DCR, and galactic latitude limits for a sufficiant number of reference stars. Two samples are described from which one can perform statistically significant searches for gas giant planets around nearby stars. One sample contains 100 "solar class" stars with an average stellar mass of 0.82 solar mass; the other maximizes the number of stars, 574, by searching mainly low-mass M stars. We perform Monte Carlo simulations of the statistical significance of the expected results by using measured and estimated noise quantities. We show the semimajor axis parameter spaces that are searched for each star and how an increase in the length of the observing program expands these spaces. The search over semimajor axis parameter space relates to the theory of gas giant planet formation.

Pravdo, Steven H.↗
NASA NTRS1975

Photometric detection of extrasolar planets using L.S.T.-type telescopes

Detection of planets similar to the earth and Jupiter that might be circling nearby stars is possible with the large space telescope (LST), or modifications of this instrument. The use of the moon as an occulter to increase the signal-to-noise ratio and the expected photon fluxes from hypothetical planetary companions to alpha Centauri A and B, tau Ceti, and epsilon Eridani are discussed. Because Barnard's Star is a red dwarf of visual apparent magnitude 9.5, photometric detection of its hypothetical Jupiter-like companion would be difficult using the LST-occulter system described in this paper.

Fennelly, A. J.↗
NASA NTRS1975

Basic research in meteorology and atmospheric physics

The effect was studied of the variations of the electromagnetic properties of the three phases of water on measurements of atmospheric and oceanographic parameters by microwave instruments aboard satellites. Other studies reported include: orbital detection of extrasolar planets, detection of stratospheric aerosols from earth orbit, chemistry of Jupiter's atmosphere, and stratospheric ozone.

Miller, J. E.↗
NASA NTRS2004

The Antarctic Planet Interferometer

The Antarctic Planet Interferometer is an instrument concept designed to detect and characterize extrasolar planets by exploiting the unique potential of the best accessible site on earth for thermal infrared interferometry. High-precision interferometric techniques under development for extrasolar planet detection and characterization (differential phase, nulling and astrometry) all benefit substantially from the slow, low-altitude turbulence, low water vapor content, and low temperature found on the Antarctic plateau. At the best of these locations, such as the Concordia base being developed at Dome C, an interferometer with two-meter diameter class apertures has the potential to deliver unique science for a variety of topics, including extrasolar planets, active galactic nuclei, young stellar objects, and protoplanetary disks.

interferometry↗