Taking the Twinkle Out Of Starlight Craig Mackay, Institute of Astronomy, University of Cambridge.
Download ReportTranscript Taking the Twinkle Out Of Starlight Craig Mackay, Institute of Astronomy, University of Cambridge.
Taking the Twinkle Out Of Starlight Craig Mackay, Institute of Astronomy, University of Cambridge. Introduction and Outline • Everything we know about the universe comes to us through telescopes and their detectors. • Astronomical objects are very faint and very distant. • We need to see more and more detail if we are to understand what is going on in the universe. • I will talk about the extraordinary progress that has been made in the last 50 years, and show how much of this has been done. • I will also give some astronomical examples of what we know and are still trying to find out. What Stops Us Seeing What We Want? • If we simply look at the light coming into a telescope on a good site it looks terrible mess! • It is atmospheric turbulence that is causing this problem and it makes are images dramatically poorer than they should be. Origins of Turbulence 14 December 2007: U3A, King’s Lynn Origins of Turbulence Improving Resolution Using Adaptive Optics • For many years, instrumentalists have tried to overcome atmospheric degradation in image quality. • Adaptive optics techniques tries to measure the wavefront distortion and correct for it before it all changes. 22 March, 2012: Open University Managing Atmospheric Turbulence • We can work out what has happened to the light from a distant star by using an instrument to measure the distortions. • We then use a deformable mirror to compensate. • Unfortunately this doesn’t work very well! (Images from 4.2m William Herschel Telescope on La Palma.) Managing Atmospheric Turbulence • Another approach is to put your telescope in space. • The Hubble Space Telescope has shown just how successful this can be. • Unfortunately it is eye-wateringly expensive! • But the results have transformed almost every field of astronomy. We Need a Radically New Approach! • A new imaging technology developed in the UK suggested a very different approach. • If we take pictures very quickly on a ground-based telescope then sometimes they are very sharp indeed. • We choose the best ones and combine these to give us a much better picture. • This is called Lucky Imaging, and has been developed to give us much better pictures than is possible from the ground by any other method. • We started to test this on La Palma in the Canary Islands. LuckyCam on the NOT LuckyCam on the NOT 14 December 2007: U3A, King’s Lynn LuckyCam on the NOT LuckyCam on the NOT LuckyCam on the NOT The Einstein Cross • The image on the left is from the Hubble Space Telescope Advanced Camera for Surveys (ACS) while the image on the right is the lucky image taken on the NOT in July 2009 through significant amounts of dust. • The central slightly fuzzy object is the core of the nearby Zwicky galaxy, ZW 2237+030 that gives four gravitationally lensed images of a distant quasar at redshift of 1.7 New Results with Lucky Astronomy • Techniques are also very popular with amateur astronomers. • This shows a short movie of the moon taken under poor conditions (roof of skyscraper in Hong Kong!). (Images courtesy Wah!, Hong-Kong) • Wah! used Registax Lucky software. New Results with Lucky Astronomy • Techniques are also very popular with amateur astronomers. • This shows a short movie of the moon taken under poor conditions (roof of skyscraper in Hong Kong!). (Images courtesy Wah!, Hong-Kong) • Wah! used Registax Lucky software. New Results with Lucky Imaging • Image of the International Space Station, with Space Shuttle Atlantis & Soyuz, June 2007. • Resolution ~20 cm at an altitude of 330 km altitude, or ~ 0.12 arcsec. • Downward looking resolution is much better, ~20 milliarcsecs or ~ 2 cm. Large Telescope Lucky Imaging. • Lucky imaging techniques on larger telescopes simply will not work. • How to improve our luck? • We remove much of the turbulent power with a simple AO system, leaving Lucky to work with what is left. • We used the Palomar 5 m telescope low-order adaptive optics system plus our Lucky Imaging camera. 14 December 2007: U3A, King’s Lynn Large Telescope Lucky Imaging. • Globular cluster M13 on the Palomar 5m. • Imaged via the PALMAO system and our EMCCD Lucky Camera. • The resolution is about 20 times better than from the ground. • This is the highest resolution image ever taken in the visible by any telescope on the ground or in space! Large Telescope Lucky Imaging. • The comparison of our system, both without Lucky/AO and with Hubble Advanced Camera (ACS) is quite dramatic. 14 December 2007: U3A, King’s Lynn What Astronomers Trying to Understand Today? • There are many basic facts about the Universe that we just do not understand. • 96% of the total mass of the Universe is invisible to us. • We know this by looking at how galaxies like this one rotate at different distances from their centres. • But it means that about 25% is dark matter. • Then there is the 70% that is dark energy….. Why is this now so Important to astronomers? • • • • The most distant supernovae suggest that the expansion of the Universe is now accelerating. These are “before” and “after” pictures showing a new supernova, visible when the Universe was ~ half its present age. It is these data that suggest the expansion of the universe is accelerating. This has been called “Dark Energy”. 22 March, 2012: Open University 22 March, 2012: Open University 22 March, 2012: Open University 22 March, 2012: Open University 22 March, 2012: Open University Gravitational Lenses Distort our View of the Universe. • • Light from very distant galaxies is bent round massive galaxies and clusters. Images are then distorted and magnified. • We need to survey where lensing is weaker, to trace where all the matter in the Universe actually is. • A Lucky survey instrument will let us measure the threedimensional distribution of dark matter for the first time. Not even sure that Newtonian Gravity is correct! • The Pioneer 10 spacecraft was launched in 1972 to survey distant planets of the solar system. • We can measure where it is, and how fast it is moving. • We can navigate very accurately in the solar system and land spacecraft on other planets and moons such as Titan. • Pioneer is not where it should be, but 400,000 km behind. • What has slowed it down? • Could be gravity anomaly. 22 March, 2012: Open University Instrumentation Group Institute of Astronomy University of Cambridge, UK [email protected]