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Reading the sky: from starspots to spotting stars
Kristianstad University, School of Education and Environment, Avdelningen för Naturvetenskap. Kristianstad University, Research environment Learning in Science and Mathematics (LISMA). (LISMA)ORCID iD: 0000-0001-6638-1246
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis encompasses two research fields in astronomy: astrometry and astronomy education and they are discussed in two parts. These parts represent two sides of a coin; astrometry, which is about constructing 3D representations of the Universe, and AER, where for this thesis, the goal is to investigate university students’ and lecturers’ disciplinary discernment vis-à-vis the structure of the Universe and extrapolating three-dimensionality.

Part I presents an investigation of stellar surface structures influence on ultra-high-precision astrometry. The expected effects in different regions of the HR-diagram were quantified. I also investigated the astrometric effect of exoplanets, since astrometric detection will become possible with projects such as Gaia. Stellar surface structures produce small brightness variations, influencing integrated properties such as the total flux, radial velocity and photocenter position. These properties were modelled and statistical relations between the variations of the different properties were derived. From the models it is clear that for most stellar types the astrometric jitter due to stellar surface structures is expected to be of order 10 μAU or greater. This is more than the astrometric displacement typically caused by an Earth-sized exoplanet in the habitable zone, which is about 1–4 μAU, making astrometric detection difficult.

Part II presents an investigation of disciplinary discernment at the university level. Astronomy education is a particularly challenging experience for students because discernment of the ‘real’ Universe is problematic, making interpretation of the many disciplinary-specific representations used an important educational issue. The ability to ‘fluently’ discern the disciplinary affordances of these representations becomes crucial for the effective learning of astronomy. To understand the Universe I conclude that specific experiences are called. Simulations could offer these experiences, where parallax motion is a crucial component. In a qualitative study, I have analysed students’ and lecturers’ discernment while watching a simulation video, and found hierarchies that characterize the discernment in terms of three-dimensionality extrapolation and an Anatomy of Disciplinary Discernment. I combined these to define a new construct: Reading the Sky. I conclude that this is a vital competency needed for learning astronomy and suggest strategies for how to implement this in astronomy education.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2014. , 229 p.
, Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1196
Keyword [en]
Astrometry, Astronomy Education Research, Disciplinary Discernment, Extrapolating three-dimensionality, Reading the Sky
National Category
URN: urn:nbn:se:hkr:diva-13268ISBN: 9789155490867OAI: diva2:768879
Public defence
2014-12-11, 09:00 (English)
Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2014-12-05Bibliographically approved
List of papers
1. Limits of ultra-high-precision optical astrometry: stellar surface structures
Open this publication in new window or tab >>Limits of ultra-high-precision optical astrometry: stellar surface structures
2007 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 476, no 3, 1389-1400 p.Article in journal (Refereed) Published
Abstract [en]

Aims. To investigate the astrometric effects of stellar surface structures as a practical limitation to ultra-high-precision astrometry (e.g. in the context of exoplanet searches) and to quantify the expected effects in different regions of the HR-diagram. Methods. Stellar surface structures (spots, plages, granulation, non-radial oscillations) are likely to produce fluctuations in the integrated flux and radial velocity of the star, as well as a variation of the observed photocentre, i.e. astrometric jitter. We use theoretical considerations supported by Monte Carlo simulations (using a starspot model) to derive statistical relations between the corresponding astrometric, photometric, and radial velocity effects. Based on these relations, the more easily observed photometric and radial velocity variations can be used to predict the expected size of the astrometric jitter. Also the third moment of the brightness distribution, interferometrically observable as closure phase, contains information about the astrometric jitter. Results. For most stellar types the astrometric jitter due to stellar surface structures is expected to be of the order of 10 micro-AU or greater. This is more than the astrometric displacement typically caused by an Earth-size exoplanet in the habitable zone, which is about 1-4 micro-AU for long-lived main-sequence stars. Only for stars with extremely low photometric variability (< 0.5 mmag) and low magnetic activity, comparable to that of the Sun, will the astrometric jitter be of the order of 1 micro-AU, sufficient to allow the astrometric detection of an Earth-sized planet in the habitable zone. While stellar surface structure may thus seriously impair the astrometric detection of small exoplanets, it has in general a negligible impact on the detection of large (Jupiter-size) planets and on the determination of stellar parallax and proper motion. From the starspot model we also conclude that the commonly used spot filling factor is not the most relevant parameter for quantifying the spottiness in terms of the resulting astrometric, photometric and radial velocity variations.

Stars : general, starspots, planetary systems, techniques : interferometric, methods : statistical
National Category
Astronomy, Astrophysics and Cosmology
urn:nbn:se:hkr:diva-50 (URN)10.1051/0004-6361:20078031 (DOI)000251507500032 ()
Available from: 2008-12-23 Created: 2008-12-23 Last updated: 2014-12-05Bibliographically approved
2. Who needs 3D when the universe is flat?
Open this publication in new window or tab >>Who needs 3D when the universe is flat?
2014 (English)In: Science Education, ISSN 0036-8326, E-ISSN 1098-237X, Vol. 98, no 3, 412-442 p.Article in journal (Refereed) Published
Abstract [en]

An overlooked feature in astronomy education is the need for students to learn to extrapolate three-dimensionality and the challenges that this may involve. Discerning critical features in the night sky that are embedded in dimensionality is a long-term learning process. Several articles have addressed the usefulness of three-dimensional (3D) simulations in astronomy education, but they have neither addressed what students discern nor the nature of that discernment. A Web-based questionnaire was designed using links to video clips drawn from a simulation video of travel through our galaxy and beyond. The questionnaire was completed by 137 participants from nine countries across a broad span of astronomy education. The descriptions provided by the participants were analyzed using hermeneutics in combination with a constant comparative approach to formulate six categories of discernment in relation to multidimensionality. These results are used to make the case that the ability to extrapolate three-dimensionality calls for the creation of meaningful motion parallax experiences.

Astronomy education research, Extrapolating three-dimensionality, Higher education, Discernment, Learning challenges
National Category
urn:nbn:se:hkr:diva-11886 (URN)10.1002/sce.21109 (DOI)000337696000007 ()
Available from: 2014-03-24 Created: 2014-03-24 Last updated: 2014-12-05Bibliographically approved
3. Introducing the anatomy of disciplinary discernment: an example from astronomy
Open this publication in new window or tab >>Introducing the anatomy of disciplinary discernment: an example from astronomy
2014 (English)In: European Journal of Science and Mathematics Education, ISSN 2301-251X, Vol. 2, no 3, 167-182 p.Article in journal (Refereed) Published
Abstract [en]

Education is increasingly being framed by a competence mindset; the value of knowledge lies much more in competence performativity and innovation than in simply knowing. Reaching such competency in areas such as astronomy and physics has long been known to be challenging. The movement from everyday conceptions of the world around us to a disciplinary interpretation is fraught with pitfalls and problems. Thus, what underpins the characteristics of the disciplinary trajectory to competence becomes an important educational consideration. In this article we report on a study involving what students and lecturers discern from the same disciplinary semiotic resource. We use this to propose an Anatomy of Disciplinary Discernment (ADD), a hierarchy of what is focused on and how it is interpreted in an appropriate, disciplinary manner, as an overarching fundamental aspect of disciplinary learning. Students and lecturers in astronomy and physics were asked to describe what they could discern from a video simulation of travel through our Galaxy and beyond. In all, 137 people from nine countries participated. The descriptions were analysed using a hermeneutic interpretive study approach. The analysis resulted in the formulation of five qualitatively different categories of discernment; the ADD, reflecting a view of participants’ competence levels. The ADD reveals four increasing levels of disciplinary discernment: Identification, Explanation, Appreciation, and Evaluation. This facilitates the identification of a clear relationship between educational level and the level of disciplinary discernment. The analytical outcomes of the study suggest how teachers of science, after using the ADD to assess the students disciplinary knowledge, may attain new insights into how to create more effective learning environments by explicitly crafting their teaching to support the crossing of boundaries in the ADD model.  

National Category
urn:nbn:se:hkr:diva-12530 (URN)
Available from: 2014-08-11 Created: 2014-08-11 Last updated: 2014-12-05Bibliographically approved

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