Scientific objectives

Stars and phenomena within reach of the hypertelescope

Like traditional telescopes, the hypertelescopes must provide direct images of astrophysical objects very various. But, while the resolution of the 2.4 m Hubble space telescope mirror is 40 milliseconds, the Ubaye hypertelescope should reach in yellow light 2 milliseconds of arc for its version with 57 m meta-ouverture and 0.5 millisecond for the version enlarged 200 m, while ELHyT should be in the order of 0.1 millisecond. As to the resolution of the space versions of 100 or 100,000 km planned later, it should be of the order of micro – or nano-seconds.

The maximum angular size λ/s of the sources whose direct imaging is made possible with a hypertelescope is in principle limited in yellow light to approximately 20 milliseconds of arc for a configuration with 5 m spaced mirrors. However the effectiveness of image deconvolution methods recently developed by C. likes, D. Mary and P. Nunez to overcome this limitation and therefore achieve the angular sizes greater than 20 milliseconds. Thus become accessible to direct imaging supergiant stars the largest and closest, such as Betelgeuse. In the case of clusters whose stars are spaced by λ/d or more – either at least 100 milliseconds-, a hypertelescope may, using a cutter of field covering a few arc seconds, providing simultaneous images of the cluster. Each of the images covering the cluster can advantageously be obtained with a "hyperspectral" camera, it means providing a spectrum of every element resolved or resel.

Practised for almost a century on the Sun, this method will so to get to the stars close comments on their Crown, the chromosphere, the photosphere and even, via techniques tell of astero-seismology, internal their structure.

The existing interferometers – who have only a low number of openings – begin to produce reconstructed images obtained from observations repeated in time. Thanks to the great number of openings, the hypertelescope produced instead an instant direct imaging – which makes it possible to study stellar phenomena rapidly evolving. More light in the interference peak concentration to increase the sensitivity in terms of magnitude limit.

Magnitude limit of the hypertelescope

The accessible limit with a hypertelescope magnitude is identical to the one that would have a one-piece telescope same collecting area than the meta-ouverture of the hypertelescope. Note that for one and the other instrument, the theoretical magnitude is accessible if the technique of Adaptive Optics is being implemented for the implementation phase, which requires the installation of a laser guide Star (need not applicable in the case of a space instrument). As the current terrestrial interferometers are not laser guide star, gain in sensitivity for a hypertelescope with laser guide star is greater than the gain arising simply from the direct imaging.

Direct imaging and scientific goals: examples

Exoplanets

• exoplanets known to detect on their surface of changes in color or spectroscopic suggesting seasonal variations
• search for exoplanets around stars more distant from the Sun than the known exoplanets
• search for nearest exoplanets from their star than those detected by other means
• transits of planets appearing on the image resolved from their parent star

Stars

• structure of protoplanetary disks to clarify the conditions of formation of exo-planets (Bedi & al. 2010)
• surface of nearby stars to detect phenomena analogous to solar flares and spots
• surface chemically specific stars (CP stars) to resolve the tasks due to chemical inhomogeneities
• Star neutron such as the crab pulsar (in principle resolvable with a 100,000 achievable km in space meta-ouverture)
• optical afterglow of gamma-ray bursts, observable also in external galaxies

Galaxies

• Active nuclei of Galaxy, and including the milky way, all shown for the hypertelescopes, and already addressed by the interferometers that will confirm the presence of a giant black hole
• clusters of galaxies
• gravitational lensing
• more distant than those observed galaxies with the Hubble telescope, therefore giving access to an even younger universe

Souces-> LISE OCA

Forecast objectives detailed by years