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UK funding (129 957 £) : Addressing outstanding issues of the local distance scale: Independent tests of astrometric missions Ukri01/10/2005 UK Research and Innovation, Royaume Uni
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Addressing outstanding issues of the local distance scale: Independent tests of astrometric missions
| Abstract | Modern astronomers have a very detailed knowledge of the physics of stars; their structure and chemical composition, how they generate energy through nuclear burning, and how they behave and evolve over time. However this is not the case for galaxies - even our own Milky Way galaxy. We really do not know in any detail how galaxies formed, how their structure evolves over time and how this is all related to the stars which are in them. In order to tackle this problem we need detailed information on the distances, ages and chemical compositions of as many objectives as possible within our galaxy, for both individual stars and for star (or stellar) clusters. Probably the most important objects in this type of study are globular clusters. These large, dense clusters of stars inhabit the outer parts of the Galaxy, and are believed to be some of the oldest objects in the Universe - they are effectively a fossil record of the state of the Galaxy at very early times. The forthcoming ESA satellite mission, GAIA (due for launch around 2010), will be able to measure very precise distances to up to a billion individual stars in our Galaxy and beyond. Perhaps more importantly, GAIA will be able to directly measure distances to many stellar clusters, including globular clusters, for the first time. GAIA will also be able to provide information on the chemical composition and ages of stars and clusters, enabling astronomers to form a very detailed picture of the structure of our galaxy. GAIA will use the same method of measuring distances as one of ESA's previous satellite missions, Hipparcos. Hipparcos measured distances to around 100,000 stars in the 'local' part of our galaxy, and the data became available to astronomers in 1997. Since then it has been used by many groups studying the properties of various types of stars and stellar clusters. However, very recently it has become evident that there is a significant problem with some of the Hipparcos data, in particular for one of the nearby stellar clusters, the Pleiades. The method used to calculate the distance to the Pleiades gives a much shorter distance than was expected from earlier, pre-Hipparcos studies, and at first it was assumed that Hipparcos must be giving the right answer. However, recent work done by myself (and other groups), based on our detailed knowledge of the properties of particular types of stars, has shown that in fact the Hipparcos distance to the Pleiades really is too short. My work is based on a method which uses other Hipparcos data for nearby field stars (i.e. stars which are not in clusters) and led to the conclusion that there are inconsistencies within the Hipparcos data itself. The Hipparcos team have now admitted that there is a problem with the way in which some of their data was interpreted - this problem mainly affects the way in which distances to stellar clusters are calculated but does not appear to be a problem for individual stars. Floor van Leeuwen, a member of the Hipparcos team, is currently working on a complete re-analysis of all the Hipparcos data. this will be finished in the next few months and made publicly available. The experience with the Hipparcos data has shown how important it is to keep on developing other methods of determining the distances, ages and chemical compositions of objects in the Galaxy in order to provide a 'consistency check' for the results which come out of the various satellite missions. My proposed work will develop and expand on methods of distance and age determination of important stellar clusters, in particular globular clusters, using techniques which I have already applied to Hipparcos data. I propose to first test these methods on nearby stellar clusters, using the revised Hipparcos data when it becomes available. I will then develop the methods so that they can be applied to globular clusters, in preparation for the detailed analysis which will be possible once we have GAIA |
| Category | Fellowship |
| Reference | PP/C50603X/1 |
| Status | Closed |
| Funded period start | 01/10/2005 |
| Funded period end | 06/11/2011 |
| Funded value | £129 957,00 |
| Source | https://gtr.ukri.org/projects?ref=PP%2FC50603X%2F1 |
Participating Organisations
| Liverpool John Moores University |
Cette annonce se réfère à une date antérieure et ne reflète pas nécessairement l’état actuel. L’état actuel est présenté à la page suivante : Liverpool John Moores University EXEMPT CHARITY, Liverpool, Royaume Uni.
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