The oldest science! Astronomy
What is Astronomy? Astronomy is the study of everything beyond the Earth’s atmosphere. What is Cosmology? Cosmology is the study of how the Universe has changed over the past 13.7 billion years.
How has technology advanced our understanding of the known Universe? Telescopes! Refractors Reflectors Compound Scopes Mulit-mirror Scopes Radio Telescopes Computers Space-based Observatories Particle Accelerators
How has our understanding of the Universe been refined over the last 4000 years? 3000 years ago Egyptian farmers deduced that when the star Sirius rose a few hours before dawn, the Nile River would rise and crops should be planted. They drew lines between the stars and filled in the rest with their imagination and folklore. 2000 years ago everyone knew that the World was flat, the Earth was the center of the Universe and that by calculating the hours of daylight, crop planting could begin. 500 years ago someone figured out that the Earth and all the planets orbited the Sun, but they still thought the Universe was only a bit bigger than the planets we could see. Today, we can accurately measure the age of the Universe to within 300,000 years, we know that our nearest companion galaxy is about 2.5 million light years away and that other suns in our Milky Way Galaxy have planets orbiting them much like planets orbit our Sun. Can you imagine what we’ll know tomorrow?
Telescopes gather energy emitted by objects in space. They don’t magnify objects by themselves. Every telescope has some device or attachment that provides magnification of the energy: lenses or cameras for light, transponders for radio waves, spectrometers to measure a star’s temperature.
The first telescope was invented by a Danish lens maker named Hans Lippershay. Galileo was the first to actually take one of Lippershay’s looking glasses and point it to the skies. The first telescopes were very crude compared to today’s telescopes, and Galileo improved upon Lippershay’s designs. About 30 years after Galileo’s death, Sir Isaac Newton invented a new type of telescope that did not use lenses to refract the image. His new idea utilized mirrors to reflect light to the viewer’s eye. Over time, telescopes got bigger and bigger. William Herschel and his wife designed really large reflecting telescopes.
The Hale Telescope was constructed in California and today represents the largest refracting telescope every built. With it, many new discoveries were made. It was with this telescope that Edwin Hubble calculated that galaxies were moving away from us in space, leading to the creation of the Big Bang theory, the accepted version of the creation of the Universe.
Today, most people have access to telescopes many times better than the telescopes that have been used for the past 400 years to discover many of the wonders of the Universe. Prices of these telescopes range from 150 on up. One of the best purchases people new to the hobby of astronomy can make is to buy a good pair of binoculars. Everything that Galileo observed is visible in the simplest binoculars manufactured today. Binoculars have several advantages over a telescope: they are portable and they allow for the use of two eyes in observing! Almost every amateur astronomer packs a pair of binoculars when they go outside for night-time observing!
There are three types of telescopes used in amateur astronomy. The include the: Refracting Telescopes Reflecting Telescopes Compound Telescopes
So, what can you expect to see with a pair of binoculars or a decent telescope? Almost everything! Although the images you will see in an eyepiece will never compare to the images from extremely large telescopes or spaced-based observatories, the fact that you can see a galaxy that is 44,000 light-years away is pretty cool! That is 6 trillion times 44 thousand miles, and in terms of the size of the Universe, that’s still really close!! When you look up at the light from the stars, you are looking back in time. Telescopes are time machines that allow us to look back in time to when the light from those objects left them. It’s a big place. Get out and look up. It’s a really big place!
What are the properties of light and what is light’s contribution to our understanding of the Universe? What is light? Light is electromagnetic radiation, especially in wavelengths visible to the naked eye. The study of light is called optics. Light has intensity, has a frequency or wavelength, can be polarized and has phases. Light exists in tiny packets called photons and demonstrates properties of both waves and particles. Light can be refracted, reflected or absorbed. In 1021, it was proposed that light was streams of minute energy particles that travel in straight lines at a finite speed! Einstein developed his special theory of relativity that stated, among other things, that the speed of light was consistent, no matter the speed of the observer of that light.
Wavelength = distance between crests Amplitude = half the height of trough to crest Frequency = number of crests that pass a point in space every second
What emits EM radiation? Everything does! You do! • the hotter the object, the shorter the wavelength of the peak • the hotter the object, the more intense the radiation
Radio Waves What kinds of things emit radio waves? • Cold molecular clouds • Planets • Pulsars • Radio galaxies • Intergalactic matter • Stars
Microwaves What kinds of things emit Microwaves? • Warm molecular clouds • Planets • Galaxies • The Universe!
Infrared Waves What kinds of things emit waves in the Infrared? • Nebulae • Planets • “Normal” stars • Brown dwarfs • Enshrouded protostars • Galaxies
Visible Light What can we see in visible light? • Nebulae • Planets • “Normal” stars, sun-like • and hotter • Galaxies
Ultraviolet Waves • Nebulae • Planets with magnetic fields • (aurorae) • O-F stars • Galaxies
X-Ray Wave lengths • Planets • O star winds • Solar corona • White dwarfs • Pulsars • Black holes • Galaxy clusters • Dark matter, indirectly
Gamma Rays • Supernovae • Diffuse Galactic emission • Active Galaxy jets • (some) Pulsars • Gamma Ray Bursts • Solar flares
How is distance calculated in the Universe? Astronomical Unit: was first accurately estimated by Giovanni Cassini in 1672. Parallax: it is a process that measures the apparent displacement of an object as seen from two different points. The parallax of the planet Mars was used to develop a fairly accurate measurement of the Earth/Sun distance. This allows us to measure up to distances of 100 ly. We next use the HR plot of star luminosities to allow us to measure out to distances of 300 K ly. Henrietta Swan Leavitt used variable stars that brighten and dim in predictable periods. Longer the period, the brighter the star. This system is accurate out to about 13 million ly. Type IA Supernovas can be used to measure distances equaling 1 Billion ly. For distances beyond, Edwin Hubble measured the Red Shift of galaxies to distances beyond 1 billion ly!