This presentation was submitted to Mr. Nahid-Ur-Rahman Chowdhury, Assistant Professor, Dept. of EEE, AUST as a part of course performance.
Published on: February 15, 2017
Team Nucleus consists five bright minds:
Nafis Sadeque, Shadman Sakib, Shaer Ahmed, Sabrina Sabah, Jahid Hasan
Nafis Sadeque, Shadman Sakib, Shaer Ahmed, Sabrina Sabah, Jahid Hasan
The greatness of human accomplishment has always been measured by size. The bigger, the better. Until now! Nanotech. Small is the new big.
This is Shaer and I welcome you on behalf of our team Nucleus to our presentation of the topic “From Nanometers to Gigaparsecs: Applications of Nanotechnology in Astronomy”.
Usually the credit for inspiring nanotechnology goes to an after dinner lecture by Caltech Physicist Richard Phillips Feynman titled “There’s plenty of room at the bottom”. Norio Taniguchi of the Tokyo University of Science coined the term ‘nanotechnology’ to describe technology that strives for precision at the level of about one nanometer. While nanometer is used to describe the minuscule length, the unit Gigaparsec is used measure the distance to most distant objects, 3.26 billion light years to be exact. In this presentation we’ll see how nanotechnology is being applied to see objects gigaparsecs away.
In the past thirty years, research and application in nanotechnology has grown rapidly. Just as our understanding of the nanoscale world has improved, our knowledge about the universe has advanced too. We largely owe to nanotechnology for our current understanding of the scale of the universe. Hubble Space Telescope has provided us photos of most distant galaxies with unprecedented clarity and resolution, helped us discover dark energy and helped us understand the age of the universe. The Hubble mirror was polished to a smoothness of only 10 nanometers. Its precisely controlled 65 nanometer thick Aluminum reflective coating was essential to achieve the best possible image. The mere 25 nanometer thick Magnesium Fluoride protective coating ensured very little to no absorption by the coating.
But immediately after launching into space, a major flaw on Hubble’s primary mirror was detected. It was very precisely ground to the prescribed curvature of only 10 nanometers but in wrong shape. The result was catastrophic and produced severely blurry images that you can see here. This error was due to a flawed null corrector that was used to calibrate the mirror. Fortunately, the scientists were able to develop and install the Corrective Optics Space Telescope Axial Replacement (COSTAR) module on Hubble Space Telescope on 1993. The device was even more precisely designed and the coating thickness was restricted to only 2 nanometers.
On July 23, 1999, NASA launched their third Great Observatory, the Chandra X-Ray Observatory which was crucial for understanding the radiating cosmic objects. The carefully polished surface that has a RMS smoothness between 0.185-0.344 nanometers allows very precise reflection and is responsible for Chandra's unparalleled resolution.
Normal mirrors in an optical telescope would absorb the X-ray photons so X-ray telescopes require cylindrical mirror surface with low grazing angle. Chandra uses four pairs of mirrors called the High Resolution Mirror Assembly. The 2 cm-thick mirror substrate is coated with 33 nanometer iridium. The grating spectrometer in Chandra has a precise plate base of 5 nanometer of Chromium and 20 nanometer of Gold and an anti-reflection coating of 15 nanometer thick Tantalum Pentoxide.
Now let’s get back to earth observatories. An extremely large telescope named Giant Magellan Telescope is under construction in Andes, Chile that has an effective aperture of 80 feet diameter telescope. The mirrors are polished to an average smoothness of only 25 nanometers. To put that in perspective, if the mirror was the size of the continental U.S., the highest mountains would be little more than a half-inch high.
Gravitational waves are 'ripples' in the fabric of space-time caused by catastrophic events such as colliding black holes, the collapse of supernovae etc. To detect these gravitational waves in conjunction with Einstein’s theory of relativity, the Laser Interferometer Gravitational-Wave Observatory (LIGO) was built. The surface quality of the mirrors used in the advanced LIGO is determined by the targeted round-trip optical loss in the arm cavities. Although polishing specifications required less than only 0.3 nanometer smoothness, advanced LIGO mirrors has a smoothness of 0.08 – 0.23 nanometers
The successor to Hubble Space Telescope and NASA’s current flagship program is a $9 billion orbital observatory named James Webb Space Telescope, planned to lift off in 2018. It will offer unprecedented resolution and sensitivity from long-wavelength visible light, and near-infrared to the mid-infrared light. While Hubble has a 7.9 ft primary mirror, the JWST features a much larger 21.3 ft mirror, composed of 18 hexagonal segments. When combined, these will offer seven times the light collecting area of Hubble, alongside instruments that are 100 times more sensitive. When fully operational, the JWST will be the most powerful space telescope ever built, capable of seeing the very first generation of stars which ignited less than 200 million years after the Big Bang.
The mirrors’ reflective coating must be a uniform 100 nanometer thick gold coating which was achieved through a process called vacuum vapor disposition. The mirrors were then polished to an average smoothness of only 20 nanometers. To align the 18 mirror segments and focus on the most distant objects, the Webb Observatory must be highly stable, with a movement of nanometer-level precision. The backplane structure is designed to provide unprecedented thermal stability performance at temperatures colder than -240°C. At these temperatures, the backplane was engineered to be steady down to 32 nanometers.
Up until now we’ve mostly seen the use of nanotechnology in astronomy only in mirror technology. But NASA is doing extensive research about other nanomaterials such as carbon nanotubes, graphene etc. We hope to see the incorporation of these nanomaterials in future observatories for making nanosensors, lightweight structure and mirror substrate that will significantly reduce weight and launching cost. As mirror technology gets better and the sensors are improved, we hope to see the universe in even greater clarity. Nanometer level components will one day help us reach places billions of light years away.
- COSTAR Image:
- Before and after installing COSTAR: hubblesite.org/image/123/news_release/1994-01
- CXO image with Cassiopeia A: svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=11185
- CXO Cross sectional view: snl.mit.edu/pub/papers/2001/Mark_jvb2001.pdf
- CXO image 1: snl.mit.edu/pub/papers/2001/Mark_jvb2001.pdf
- CXO image 2 : chandra.harvard.edu/resources/illustrations/instrumentsSchema.html#instruments7
- CXO image 3: cxc.harvard.edu/proposer/POG/html/chap4.html
- LIGO image 1: www.ligo.caltech.edu/image/ligo20150731a
- LIGO image 2: arxiv.org/ftp/arxiv/papers/1411/1411.4547.pdf
- JWST Trailer: www.youtube.com/watch?v=TD0uk6nX6fU
- JWST Mirror: en.wikipedia.org/wiki/File:JWST_Full_Mirror.jpg
- Mirror Anatomy: www.flickr.com/photos/nasawebbtelescope/13291410214/in/album-72157658888594928/
- Euclid Image: www.nasa.gov/mission_pages/euclid/multimedia/euclid-artist-impression.html
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