The Hubble Space Telescope …. and it’s successor …. plus ‘Edwin Hubble, his life and work’ Context - what and where • Solar system • Distances • Stars and Galaxies • The Milky Way • Earliest Light The Solar System The Solar system formed about 5 billion (5 thousand million) years ago. The circumference of Earth is 40,000km (25,000 miles) and of the Moon is 11,000 km (6,800 miles). We are, on average, 93 million miles (150 million kms) from the Sun, and it takes 8 minutes 20 seconds for light from the Sun to reach the Earth. The average distance from the Earth to the Sun is also known as one Astronomical Unit (AU). Astronomical units are usually used to measure distances within our Solar System. The Earth orbits the Sun in one year. One day is the time it takes for the earth to spin round once. Other planets orbit at different rates; eg, Jupiter takes 12 years for one orbit of the Sun; Mars takes 687 days. The Moon orbits around the Earth once every 27.32 days. It is 250 thousand miles (400 thousand km) away, so it takes 1.3 seconds for light to travel from the Moon to us. Every individual star your eyes can see in the night sky is in the Milky Way Galaxy. Our Sun is just one minor star in one Galaxy Distances and times Distances in space are so huge that new measurements are needed. The distance measurement often used is the light-year, the distance that light travels in one year in a vacuum. One light-year = 9.46 trillion (million million) km = 5.88 trillion (million million) miles. If we ‘see’ a galaxy that is 5 light years away we are actually seeing it as it was 5 years ago, and have no idea if it has changed in the meantime. The parsec is another unit of length used to measure large distances to astronomical objects outside the Solar System. One parsec is equal to about 3.26 light-years (30 trillion km or 19 trillion miles) in length. The Universe is 13.8 billion years old. The age of the solar system, derived from the study of meteorites (thought to be the oldest accessible material around) is ~ 5 billion years; that of the Earth is taken as 4.6 billion years. The oldest rocks on Earth are dated as 3.8 billion years. Stars and Galaxies A galaxy is a huge area in space, made up of stars, (exo)planets, moons, dust and gas. ‘Small’ galaxies can contain 100,000,000 stars, giants 100,000,000,000,000 stars, all spinning round the galaxy’s centre. Many galaxies are thought to have black holes at their active centres. Recent estimates of the number of galaxies in the observable universe range from 200,000,000,000 to 2,000,000,000,000 or more, each containing more stars than all the grains of sand on planet Earth. Most galaxies are 3,000 to 300,000 light-years in diameter and separated by distances of millions of light-years. The space between galaxies is filled with a very thin gas having an average density of less than one atom per cubic metre. Each cubic metre of air on Earth contains about 10 trillion trillion molecules. The largest structure of galaxies yet recognised is a cluster of superclusters named Laniakea - which contains the Milky Way and approximately 100,000 other nearby galaxies. The Milky Way - a rotating spiral disc The Milky Way is constantly rotating. The solar system travels at an average speed of 515,000 mph (828,000 km/h) relative to the centre of the galaxy. It still takes us about 230 million years to make one complete orbit around the Milky Way. Andromeda Galaxy The Andromeda Galaxy is the closest big galaxy to our Milky Way. At 2.537 million light years from Earth, it’s the most distant thing you can see with your eyes alone. This magnificent image of a keen astrophotographer in Moab, Utah was taken by Brad Goldpaint. The photo captures the Andromeda Galaxy, the Milky Way and the canyons below. It won the top prize at the Royal Observatory Greenwich Astronomy Photographer of the Year awards 2018. Earliest light Light travels at 300,000 kilometres per second so when we see distant objects we are looking back in time. You're not seeing the sun as it is today, you're seeing an 8 minute old sun. You're seeing 642 year-old Betelgeuse. 2.5 million year-old Andromeda. The universe is expanding, so stars and galaxies were closer in the past. The moment of first light in the universe, around 370,000 years after the Big Bang, is known as Recombination. Electrons and protons formed hydrogen atoms; at this point the universe transitioned from being totally opaque to transparent. Before that photons were unable to escape from a dense ‘particle soup’. This is the earliest possible light that astronomers can see - the Cosmic Microwave Background (CMB) radiation. How far can we ‘see’? A huge blue star nicknamed Icarus is the farthest individual star ever ‘seen’. Astronomers using the Hubble Space Telescope were able to identify this distant star and set a new distance record. The star is so far away that its light has taken 9 billion years to reach Earth. It appears to us as it did when the universe was about 30% of its current age. Redshift is a phenomenon where electromagnetic radiation (such as light) from an object undergoes an increase in wavelength when objects move apart in space. This is an example of the Doppler effect. GN-z11 is a high-redshift galaxy found in the constellation Ursa Major and is currently the oldest and most distant known galaxy in the observable universe. The redshift corresponds to a proper distance of approximately 32 billion light-years. GN-z11 is observed as it existed 13.4 billion years ago, just 400 million years after the Big Bang. The Hubble Space Telescope (HST) • Technology • Cost • Management • Maintenance • Science Introduction to the Hubble Space Telescope https://www.youtube.com/watch?v=073GwPbyFxE Hubble Space Telescope The Hubble Space Telescope (HST) was launched into low Earth orbit in April1990 and remains in operation. Although not the first space telescope, Hubble is one of the largest and most versatile, and is both a vital research tool and a public relations boon for NASA and astronomy generally. The HST is named after the astronomer Edwin Hubble, and is one of NASA's Great Observatories, along with the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and the Spitzer Space Telescope. Design, build operation and servicing With a 2.4-metre (7.9 ft) mirror, Hubble's four main instruments observe in the near ultraviolet, visible, and near infrared spectra. Hubble orbits outside the distortion of Earth's atmosphere, which allows it to take extremely high-resolution images with substantially lower background light than ground-based telescopes. The Hubble Space Telescope (HST) was built by the National Aeronautics and Space Administration (NASA), with contributions from the European Space Agency (ESA). The Space Telescope Science Institute (STScI) selects Hubble's targets & processes the resulting data; the Goddard Space Flight Center controls the spacecraft. Hubble was funded in the 1970s, with a proposed launch in 1983, but the project was delayed by technical issues, budget problems, and the Challenger disaster (1986). When finally launched in 1990, Hubble's main mirror was found to have been ground incorrectly. The optics were corrected by a servicing mission in 1993. Hubble is the only telescope designed to be serviced in space by astronauts. The telescope is (May 2020) still operating, and could continue until 2030–2040. HST facts NASA named the world's first space-based optical telescope after American astronomer Edwin P. Hubble (1889 -- 1953) who confirmed an "expanding" universe, which provided the foundation for the big-bang theory. Mission • Launch: April 24, 1990, from space shuttle Discovery (STS-31) • Deployment: April 25, 1990 • First Image: May 20, 1990: Star cluster NGC 3532 • Servicing Mission 1 (STS-61): December 1993 • Servicing Mission 2 (STS-82): February 1997 • Servicing Mission 3A (STS-103): December 1999 • Servicing Mission 3B (STS-109): February 2002 • Servicing Mission 4 (STS-125): May 2009 Size • Length: 43.5 feet (13.2 m) • Weight: At Launch: about 24,000 pounds (10,886 kg) • Post Servicing Mission 4: about 27,000 pounds (12,247 kg) • Maximum Diameter: 14 feet (4.2 m) Orbital Statistics • Low Earth Orbit: Altitude of 340 miles (295 nautical miles, or 547 km), inclined 28.5 degrees to the equator • Time to Complete One Orbit: about 95 minutes • Speed: about 17,000 mph (27,300 kph) HST facts /2 Hubble uses two mirrors, laid out in a Cassegrain telescope design, to collect and focus light. After light travels down the length of the telescope, it hits the concave, or bowl-shaped, primary mirror. The light reflects off of the primary mirror and travels back toward the front of the telescope. There it hits the secondary mirror, which is convex, or dome-shaped. The secondary mirror concentrates the light into a beam the size of a dinner plate that travels back toward and then through a hole in the primary mirror. The light is then directed into science and guidance instruments for analysis. HST facts /3 Optical Capabilities • Sensitivity to Light: Ultraviolet through Infrared (115–2500 nanometers) Hubble's Mirrors • Primary Mirror Diameter: 94.5 inches (2.4 m) • Primary Mirror Weight: 1,825 pounds (828 kg) • Secondary Mirror Diameter: 12 inches (0.3 m) • Secondary Mirror Weight: 27.4 pounds (12.3 kg) HST facts / 4 Pointing Accuracy • In order to take images of distant, faint objects, Hubble must be extremely steady and accurate.