The Small Telescopes Still Useful for the Astrometry
Magda Stavinschi Astronomical Institute of the Romanian Academy
What is the Astrometry?
•It provides the positionand, by extension, the dimensions and the shapes of the celestial bodies.
•As the stars change their positions in time, it has to describe their motion.
•It allows us to determine the geometrical and dynamical properties of the bodies from our Universe.
1 To measure the motion of the closest objects we need to materialize a fixed RS on the sky.
Quasars and distant galaxies: ideal fiducial points for RF
RS = theoretic concept, materialized by a RF
Continuous and more and more precise astrometric observations
Star positions determined for Hipparchus (190 BC œ 120 BC) years by GB observations, within the framework of a large international campaign, known as "Carte duciel".
Catalogues of star positions with greater and greater accuracy
2 HIPPARCOS (High Precision Parallax Collecting Satellite) first space experiment fully dedicated to astrometry.
HIPPARCOS mission 1989 - 1993
•FK5 RS was replaced by a CRS based on the positions of extragalactic radio sources => ICRS. •Epoch = 1998, January 1 •consistent with FK5 - S at J 2000.0. •materialized by equatorial coordinates of extragalactic radio sources observed by VLBI. •based on a kinematical definition (assuming that the visible Universe does not rotate).
HIPPARCOS system coincides
• with the principal axes of the ICRS at + 0.6 mas
• with individual p.m. consistent with an inertial system at +0.25 mas/yr.
3 HIPPARCOS catalogue:
- 118,218 stars (≈ 3 stars/square degree) - astrometric parameters - photometric information
The astrometric precision in position, p.m. & parallax of order 1 mas or mas/yr, or better for the brighter stars
The mean magnitude Hp = 8.7 Half of the catalogue lies in the interval 8 < Hp < 9.5.
It makes the accessible universe 8 times larger than expected from the nominal mission
. HIPPARCOS catalogue => TYCHOcatalogue, (1 million of stars) => TYCHO 2 (3 millions stars)
Mean value of internal standard errors: •25 mas for the position components •0.10 magfor BT-VT colour index
4 ACHIEVEMENTS
•predict the impacts of Comet Shoemaker-Levy 9 on Jupiter
•identified stars that will pass close to the Sun
•established the distances of stars possessing planets
•discovered that the Milky Way is changing shape
•identified a group of stars that invaded our Galaxy when it was young
•altered the cosmic distance scale, making the Universe bigger and younger
•confirmed Einstein's prediction of the effect of gravity on starlight
What about the future?
As HIPPARCOS was not enough, the astronomers like to reach better and better accuracy as soon as possible.
Other missions are ready to be launched
composition, formation and evolution of our Galaxy by mapping with unprecedented precision the stars positions, p. m. & parallaxes of at least 4 - 50 million objects down to V = 15 mag accuracy better than 10 mas along with multi-colour multi-epoch photometry of each object.
It could offer the possibility to detect the presence of Earth-like planets around stars within 20 pc
LAUNCH DATE: Dec-2011 MISSION END: 2020 317 million Euros
OBJECTIVES:
The largest and most precise three dimensional chart of our Galaxy by providing unprecedented positional and radial velocity measurements for about one billion stars in our Galaxy and throughout the Local Group.
6 Additional scientific products
•detection and orbital classification of tens of thousands of extra-solar planetary systems,
•a comprehensive survey of objects ranging from huge numbers of minor bodies in our SS, through galaxies in the nearby Universe, to some 500000 distant quasars
• number of stringent new tests of general relativity and cosmology
It is the GB Astrometry still useful?
WG FUTURE DEVELOPMENT OF THE GB ASTROMETRY
founded in 2000
7 FDGBA PROJECTS
A FOLLOW-UP PROGRAM FOR THE SPACE ASTROMETRY PROJECT GAIA
W. Thuillot (1) & M. Stavinschi (2) (1)Institut de mécanique céleste et de calcul des éphémérides, Paris Observatory (2) Astronomical Institute of the Romanian Academy, Bucharest
8 The Solar System WG of GAIA(SSWG), coordinated by F. Mignard (Observatoire de la Cote d'Azur, France) and V. Zappala (Torino Observatory), undertakes exploratory studies for the observation program of the solar system by GAIA.
Within this framework it plans to constitute a network for GB observations to follow-up GAIAwith the principal aim to confirm new target detections by GAIA and to carry out any astrometric measurements necessary for the improvement of the orbital elements and the cataloguing of these objects.
Robotic telescopes
In France, ARAGOproject (PI M. Boër, CESR/OMP Toulouse) whose speed of pointing will make it possible to observe on alarm for multiple programs, appears perfectly well suited to this type of task.
Mainly dedicated to the study of the transitory events, Gamma Ray Bursts in particular, this project has included a contribution for GAIA follow-up obs. within the whole of the programs which it is envisaged to carry out.
9 Conventional telescopes
These projects will be certainly far from providing an adequate cover of the sky in longitude and latitude, and their number will be insufficient to combat the weather risks.
Telescopes of the 1-2m class will be particularly well suited, mainly due to access to these telescopes being more flexible than that for larger telescopes.
CCD cameras on these telescopes are generally well suited for accurate astrometry of fast and eventually faint objects.
Smaller telescopes could also be used for the brighter objects
Mutual phenomena of Uranus satellites in 2007-2008 and further observations in network
November 15-18, 2006, Paris Institut de Mécanique Céleste et de Calcul des Éphémérides
Several astronomical studies require a large network of observers in order to acquire enough data of rare phenomena or to observe objects on alert or for a follow-up.
10 •the observation of the mutual events of the satellites of Uranus (2007-2008, only every 42 years), of the Jovian ones in 2009, the Saturnian ones in 2010 & any event involving asteroids for the study of natural satellites systems or double asteroids
•the preparation for ground-based follow-up observations needed for GAIA
other possible objectives for GB astrometry
Solar system • Observation of minor planet positions for the determination of the masses of perturbing bodies
• Observations of Earth-cruisers, for which one needs to update frequently the orbits
• Bulk observations of newly discovered objects in order to get good orbits for recognition purposes
• Observation of small planetary satellites using mask technique to dim the luminosity of the planet
11 Stars and stellar systems:
• Observation of close binaries by speckle interferometry. The large number of these objects and their potential obtained data for determining stellar masses call for more instruments devoted to speckle interferometry.
• Determination of stellar diameters by speckle interferometry or using occultations by the Moon.
• Photometry of variable stars, in particular eclipsing binaries, which permits to determine stellar masses.
• Recognition of stars and determination of their p.m. in highly crowded fields badly conditioned for space astrometry.
Last but not least there are the educational efforts for the training of a new generation of astrometrists, now before the launching of new space specialized missions and the processing of a huge amount of data collected so far.
12 CONCLUSIONS YY EE SS
The Small Telescopes are still useful for the Astrometry
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