![]() Reaction wheels manoeuvre the telescope into place, and gyroscopes monitor its position. Two solar wings provide power for the computers and scientific instruments and charge six nickel-hydrogen batteries to power the spacecraft for about 25 minutes per orbit while it flies through Earth's shadow.Īn elaborate system of attitude controls improves Hubble’s stability during observations. HST was placed in a low orbit, designed to be serviced in space by astronauts on the Space Shuttle, allowing instruments to be replaced as technology improved, and observatory subsystems to be repaired and modernised. It has three cameras, two spectrographs and a set of Fine Guidance Sensors that allow Hubble to accurately point to targets on the sky. They are so blue they must be deficient in heavy elements, thus representing a population with primordial characteristics.Īt the heart of HST is a 2.4 m-diameter primary mirror supplying light to five science instruments working across the entire optical spectrum: from infrared, through the visible, to ultraviolet light. With the sensitive ‘WFC3’ panchromatic camera, Hubble has seen galaxies that formed just 600-800 million years after the Big Bang, which are showing signs of their origin from the first stars. Coordinating with other observatories, Hubble has taken long exposures of small regions of sky, to bring out the most distant and most ancient galaxies. Hubble has pushed back the observational boundaries of the Universe. Hubble showed at high resolution that about half of the young stars in the Orion Nebula are surrounded by gas and dust structures, many of them discs. For centuries it has been believed that the Solar System began as a disc. ![]() Prior to Hubble, the presence of dust discs around a small number of young stars had been inferred from observations by infrared satellites, but only one disc, around Beta Pictoris, had been directly imaged with a ground-based coronagraph. This points to the existence of ‘dark energy’, a force that comes to exceed gravity and causes the Universe’s expansion to accelerate. By studying ‘Type Ia supernovae’ – stars that explode at the end of their life – as distance indicators, Hubble found that the speed with which the Universe is presently expanding had been increasing for the last several billion years. It was also thought that expansion of the Universe would be slowing by now, as gravity acts to reduce the remnant velocity from the Big Bang. It directly imaged an exoplanet orbiting Fomalhaut. Hubble made measurements of a planet’s atmosphere around another star (HD 209458), finding evidence of sodium, carbon and oxygen, and methane in the atmosphere of another Jupiter-sized planet, HD 189733b. When it was launched, planets outside our Solar System (exoplanets) had not been observed. Hubble has made some dramatic discoveries. High above the atmosphere, Hubble collects visible light and observes the infrared and ultraviolet wavelengths usually filtered out. Putting a telescope in space avoids this problem. However, before arriving at a telescope on Earth, it must travel through our turbulent atmosphere, which blurs out the fine cosmic details. Light can travel through the Universe virtually undisturbed for thousands of millions of years.
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