Nulling interferometry for extra-solar planet detection: sensitivity and image reconstruction
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interferometry extra-solar planets↗
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Nulling interferometry for extra-solar planet detection: sensitivity and image reconstruction
This paper addresses the image reconstruction issues for nulling interferometer arrays and the sensitivities for planet detection.
extra-solar planets interferometry↗
Radio detection of Jupiter-like extra-solar planets
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Fennelly, A. J.↗
Direct imaging of extra-solar planets with stationary occultations viewed by a space telescope
The use of a telescope in space to detect planets outside the solar system by means of imaging at optical wavelengths is discussed. If the 'black' limb of the moon is utilized as an occulting edge, a hypothetical Jupiter-Sun system could be detected at a distance as great as 10 pc, and a signal-to-noise ratio of 9 could be achieved in less than 20 min with a 2.4 m telescope in space. An orbit for the telescope is proposed; this orbit could achieve a stationary lunar occultation of any star for a period of nearly two hours.
Elliot, J. L.↗
First spectrum of an extra-solar object in the extreme ultraviolet The white dwarf HZ 43
An EUV instrument is described which has been used to carry out a spectroscopic observation of the hot white dwarf HZ 43. The instrument consists of an EUV telescope and spectrometer housed in a sounding-rocket shell 44 cm in diameter and 176 cm in length. It is noted that HZ 43 was successfully observed for 200 sec and that the EUV spectrum was strongly detected from 170 to 400 A. A second-order image was detected beyond 400 A, and a decrement was observed at 200 A, which corresponds to photoelectric absorption of He II. The observed spectrum is shown to be inconsistent with a coronal model. It is concluded that the surface number density of helium relative to hydrogen must be in the range from 0.00001 to 0.0001 and that an upper limit of 4 x 10 to the 17th per sq cm can be placed on the column density of ionized helium in the intervening interstellar medium.
Malina, R. F.↗
Systems level feasibility study for the detection of extra-solar planets. Volume 1: Infrared interferometer (IRIS) known as the Stanford Concept
A sensor system for the direct detection of extrasolar planets from an Earth orbit is evaluated: a spinning, infrared interferometer (IRIS). It is shuttle deployed, free flying, requires no on-orbit assembly and no reservicing over a design life of five years. The sensor concept and the mission objectives are reviewed, and the performance characteristics of a baseline sensor for standard observation conditions are derived. A baseline sensor design is given and the enabling technology discussed. Cost and weight estimates are performed; and a schedule for an IRIS program including technology development and assessment of risk are given. Finally, the sensor is compared with the apodized visual telescope sensor (APOTS) proposed for the same mission. The major conclusions are: that with moderate to strong technology advances, particularly in the fields of long life cryogenics, dynamical control, mirror manufacturing, and optical alignment, the detection of a Jupiter like planet around a Sunlike star at a distance of 30 light years is feasible, with a 3 meter aperture and an observation time of 1 hour. By contrast, major and possibly unlikely breakthroughs in mirror technology are required for APOTS to match this performance.
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Extra-solar astronomy with a 2.4 m normal incidence X-ray telescope at 0.1 arcsec resolution
The advantages and disadvantages for astrophysical observations of a normal incidence X-ray telescope are considered. The baseline configuration is for a 2.4 meter diameter mirror operating at 0.23-0.28 keV with a CCD detector having a pixel size equivalent to 0.1 arcsec. This resolution enables X-ray images to be made comparable to those of Space Telescope in the optical and to those of the Very Large Array in the radio for a large number of sources. Specific examples cover essentially the entire range of astrophysics.
Elvis, M.↗
Direct detection of extra-solar planetary systems from the ground and space
This paper discusses recent work in the development of instrumentation used for the direct detection of planetary systems from ground-based and space-based observatories. Direct methods such as CCD coronagraphic imaging of nearby stars must overcome the large contrast differences between parent star and the circumstellar material. However, these methods have the advantage over indirect methods in that more advanced space-based direct detection instrumentation can lead to a significantly greater science return.
Terrile, R. J.↗
Direct imaging of extra-solar planetary systems with the Circumstellar Imaging Telescope (CIT)
In a joint study conducted by the Jet Propulsion Laboratory and the Perkin-Elmer Corporation it was found that an earth orbital, 1.5 meter diameter low scattered light coronagraphic telescope can achieve a broad range of scientific objectives including the direct detection of Jupiter-sized planets around the nearby stars. Recent major advances in the understanding of coronagraphic performance and in the field of super smooth mirror fabrication allow such an instrument to be designed and built within current technology. Such a project, called the Circumstellar Imaging Telescope (CIT), is currently being proposed.
Terrile, Richard J.↗
Application of super smooth optics to extra-solar planet detection
The observational constraints on direct detection of extrasolar planets around nearby stars are defined. The design of an instrument capable of meeting these goals requires the efficient reduction of diffracted and scattered light by about three orders of magnitude below the airy wings of the unapodized aperture. The diffraction reduction is achieved through the high-efficiency coronagraph, which uses Gaussian occulting masks in the first focus to concentrate better diffracted light in the pupil plane. Laboratory experiments confirm this high efficiency to the limits set by the experimental setup. Scattering due to midspatial scale figure error in the mirrors must also be reduced to a comparable level.
Terrile, Richard J.↗
An IRAS search for extra-solar Oort clouds
The presumptively close connection between Oort cloud formation and planetary formation is that the detection of comet clouds around other stars would imply the presence of extrasolar planetary systems. Low-resolution IRAS data and an S/N-enhancement method are presently used to search 17 nearby stars for comet cloud-indicating IR emission. While no such detections were obtained, upper limits have been set for extrasolar Oort clouds (ESOCs) around the candidate stars; the nondetections may be a results either of the absence of the ESOCs around these stars or, with greater probability, of the sensitivity and background confusion limitations of IRAS data.
Stern, S. Alan↗
Radial velocity detection of extra-solar planetary systems
The goal of this program was to detect planetary systems in orbit around other stars through the ultra high precision measurement of the orbital motion of the star around the star-planet barycenter. The survey of 33 nearby solar-type stars is the essential first step in understanding the overall problem of planet formation. The program will accumulate the necessary statistics to determine the frequency of planet formation as a function of stellar mass, age, and composition.
Cochran, William D.↗
Space optics for studying extra-solar planetary systems
The sharp imaging of telescopes in space will improve the ability to see faint objects near bright ones. One exciting application is the search for planets around other stars. However, because a planet is, at best, 10 exp 9 times fainter than a star in visible light, specialized optical systems are required. Using apodization to remove diffracted light, the limiting source of noise is the intensity of starlight scattered by mirror figure errors. Based on the prelaunch metrology of the HST mirrors, and considering only photonstatistics, months of integration would be needed for HST to detect Jupiter next to the sun at a distance of 5 pc. The integration times will be shorter for future telescopes in space with smoother mirrors and/or larger apertures.
Brown, Robert A.↗
Studies of extra-solar Oort Clouds and the Kuiper disk
In 1991 we detected extended 1.1 mm emission around Fomalhaut (alpha PsA) at distances in order of magnitude beyond previous detections. This emission is plausibly related to the presence of an extended comet cloud, like our Oort Cloud, and may therefore represent indirect evidence for the formation of a planetary system at Fomalhaut. We propose now to extend this work to create a map of the angular and spatial extent of this emission. Fomalhaut is the only known main-sequence, submm-resolved IR excess source besides beta Pic.
Stern, S. Alan↗
Gamma-ray burst constraints on the galactic frequency of extra-solar Oort clouds
With the strong CGRO/BATSE evidence that most gamma-ray bursts do not come from galactic neutron stars, models involving the accretion of a comet onto a neutron star (NS) no longer appear to be strong contenders for explaining the majority of bursts. If this is the case, then it is worth asking whether the lack of an observed galactic gamma-ray burst population provides a useful constraint on the number of comets and comet clouds in the galaxy. Owing to the previously unrecognized structural weakness of cometary nuclei, we find the capture cross sections for comet-NS events to be much higher than previously published estimates, with tidal breakup at distances R(sub b) approximately equals to 4 x 10(exp 10) cm from the NS. As a result, impacts of comets onto field NS's penetrating the Oort Clouds of other stars are found to dominate all other galactic NS-comet capture rates by a factor of 100. This in turn predicts that if comet clouds are common, there should be a significant population of repeater sources with (1) a galactic distribution, (2) space-correlated repetition, and (3) a wide range of peak luminosities and luminosity time histories. If all main sequences stars have Oort Clouds like our own, we predict approximately 4000 such repeater sources in the Milky Way at any time, each repeating on timescales of months to years. Based on estimates of the sensitivity of the CGRO/BATSE instrument and assuming isotropic gamma-ray beaming from such events, we estimate that a population of approximately 20-200 of these galactic NS-Oort Cloud gamma-ray repeater sources should be detectable by CGRO. In addition, if giant planet formation is common in the galaxy, we estimate that the accretion of isolated comets injected to the interstellar medium by giant planet formation should produce an additional source of galactic, nonrepeating events. Comparing these estimates to the three to four soft gamma-ray repeater sources detected by BATSE, one is forced to conclude that (1) comet impacts on NS's are inefficient at producing gamma-rays; or (2) the gamma-rays from such events are highly beamed; or (3) the fraction of stars in the galaxy with Oort Cloud like our own is not higher than a few percent.
Shull, J. Michael↗
High-precision VLBI astrometric observations of radio-emitting stars for detection of extra-solar planets
The displacement of a radio-emitting star around the barycenter of a possible planetary system can be measured by astrometric very long baseline interferometry (VLBI) observations. We have observed the radio-emitting star sigma(sup 2) CrB at 8 epochs over 5 years by VLBI and fitted its 5 astrometric parameters to the observed coordinates. The post-fit coordinate residuals have and rms scatter of 0.22 milliarcseconds and show no systematic behavior. We use this result to set a limit on the presence of planets around sigma(sup 2) CrB and conclude that our present VLBI astrometric precision corresponds to the threshold to detect a Jupiter-like planet around this star. We also discuss the astrometric monitoring program of 11 radio-emitting stars that we are conducting for the Hipparcos space mission and its possible contribution to a long-term planet search program.
Lestrade, Jean-Francois↗
The Edison infrared space observatory and the study of extra-solar planetary material
Edison is a proposed large-aperture, radiatively-cooled space observatory planned to operate at wavelengths between 2 and 130 micrometers or longer. Current estimates for the telescope allow an aperture of 1.7 m which will achieve a final equilibrium temperature of about 30 K, although use of cryocoolers may permit temperatures below 20 K. Edison will be a powerful tool to investigate our Solar System, as well as planetary material around distant stars. At near- and mid-infrared wavelengths, where planetary material emits most of its radiation, Edison will be the most sensitive photometric and spectroscopic observatory under current consideration by the space agencies. With its large aperture, Edison will be able both to resolve the structure in nearby circumstellar 'Vega disks' and to discriminate faint IR emission in the crowded environment of the galactic plane. With its long lifetime, Edison will allow extensive follow-up observations and increase the likelihood of catching transient events. We propose Edison as a precursor to elements of a future space-based IR interferometer.
Thronson, H. A., Jr.↗
The Circumstellar Imager: Direct detection of extra-solar planetary systems
The Astrometric Imaging Telescope (AIT) is designed to probe the circumstellar environment by both direct imaging and indirect astrometric measurements. The Circumstellar Imager (CI) is a coronagraphic camera and is the direct imaging component of the AIT. The CI is designed to obtain high-sensitivity images of the circumstellar region. It provides crucial non-inferential information relating to the frequency, origin, and evolution of planetary systems and all forms of circumstellar matter. Such imaging is usually limited by the scattered and diffracted light halos of the star itself, which are greatly suppressed in the CI by mating a novel high-efficiency coronagraph with a phase-compensated optical system. For faint point sources in the circumstellar region, the CI will have a sensitivity in excess of 5 magnitudes fainter than the as-designed Hubble Space Telescope (HST). Laboratory data are shown for the coronagraph, which, in a diffraction-limited environment, is capable of suppressing the stellar diffraction sidelobes by several orders of magnitude without significant sacrifice of field of view. In order to realize the high rejection levels inherent in the coronagraph design, it is necessary to limit scatter in the optical systems, imposing a mid-spatial frequency figure error requirement an order of magnitude smaller than that of the HST. Experimental data directed toward meeting this requirement are also shown.
Ftaclas, Christ↗