Presentation on theme: "Announcements The second project presentations are next time, Wednesday April 30 at 4:30pm. If we don’t get through all of them the others will present."— Presentation transcript:
Announcements The second project presentations are next time, Wednesday April 30 at 4:30pm. If we don’t get through all of them the others will present Monday May 5 Exam 3 is Monday May 5. If there are presentations to be made, they will be done first and then the exam will be given. It will be a 1-hour exam like the others. Covers Chapters 8 & 9. Sample questions are posted on the class website.
The Next Generation of Telescopes The GMT and Thirty- Meter Telescopes will be enormous. The LSST, while only 8.2-m, will add the time domain
There are now two methods for making BIG telescopes Combine 8.2m mirrors or make 1-m segments and combine lots of them The 1-m segments are made using “traditional” methods. The 8.2m mirrors are spin-cast
The Steward Mirror Lab is where all 8.2m mirrors are made
Space Telescopes The HST has been up for 24 years. It is “only” a 2.4-m telescope. The James Webb Telescope is slated for launch in 2018. It will be a 6.5-m telescope.
Radio Astronomy pre-WWII In the 1930’s Karl Jansky detected a signal from the direction of the center of the Milky Way Also in the 1930’s Grote Reber did scans of the sky in radio wavelengths
After WWII radio astronomy began to advance rapidly The NRAO was established in 1956 and radio telescopes began sprouting in Green Bank WV
By 1963 the Arecibo Radio Telescope was built Built in a natural hollow in the mountains of Puerto Rico the dish is 300-m across
The Very Large Array (VLA) is Socorro NM uses interferometry Each of the 27 dishes is 25-m in diameter
Radio telescopes were able to penetrate the obscuring dust and show the spiral structure of the Milky Way
Radio telescopes also began discovering objects outside the Milky Way Cygnus A was one of the first “radio loud” galaxies but because the radio lobes were so far from the galaxy, the two weren’t associated together for some time
Radio astronomy also answered the “Big Question” in cosmology Fred Hoyle was the leading proponent of the Steady State Theory. It proposed that new matter was being created in intergalactic space to make new galaxies as the older galaxies moved away
Arno Penzias and Robert Wilson ended the debate In 1963 the two had been trying to calibrate a radio horn for satellite communication when they discovered the cosmic background radiation. A group at Princeton, headed by Robert Dicke, was trying to build a radio telescope to look for the CBR at the same time but were scooped.
Beyond Radio and Visible To “see” wavelengths other than visible and radio requires telescopes above the Earth’s atmosphere and astronomy benefited from the space race between the US and USSR
Early “telescopes” were put on V-2 rockets Equipment would be loaded where the warhead had been and sent as high as possible
After Sputnik, space astronomy literally took off The Orbiting Astronomical Observatory was launched in 1968 and lasted for 8 years.
Skylab carried several small telescopes Among the telescopes was a small x-ray telescope that was used to study the Sun
By the 1980’s a number of space telescopes were launched IRAS, an infrared telescope, was launched in 1983 COBE was launched in 1989
First came the discovery of star- like objects that were radio loud In visible light they looked like a star but they were radio loud and stars don’t produce radio waves so they were called Quasi Stellar Radio Sources or Quasars
Maarten Schmidt measured the spectra of a quasar and found extreme redshift
Eventually a super massive black hole theory is proposed The jet from a central supermassive black hole creates radio lobes when it plows into intergalactic gas. The bright accretion disk around the black hole is only the size of the solar system, thus the star-like appearance
The Hubble Space Telescope was eventually able to resolve host galaxies
In 1967 Jocelyn Bell, working under Antony Hewish, discovered pulsars
Pulsars are spinning neutron stars Light is emitted out the magnetic axis via synchrotron emission
Binary pulsars have proven General Relativity under extreme conditions The first were discovered by Russell Hulse and Joseph Taylor in 1974. The won the Nobel Prize for it in 1993