Astronomy – The Original Science

Lets talk about calendars….

Ancient Calendars Based on observations of the sky Ancient Mayans – used the cycles of the sun, moon and Venus Ancient Chinese – used the moon’s phases and positions in the sky Ancient Egyptians – used the sun Ancient Hebrews – used the moon and sun

Getting closer to our Modern Calendar Early Roman calendar Had 365 days in a year Had 7 days in a week Eventually the seasons began to shift

Getting closer to our Modern Calendar Julian calendar Had 365.25 days in a year Added an extra day every 4 years (Leap year) Gregorian calendar Had 365.242 days in a year Dropped 10 days from the year 1582 Restricted leap years to years divisible by 4 but not 100 Scientists calculate this calendar will be accurate for 3,000 years

The Beginnings of Astronomy Recorded astronomical observations date back to 6,000 to 7,000 years ago Stonehenge is probably one such place Built between 3000 B.C. and 1500 B.C.

Early Astronomers Ptolemy In 140 A.D. he theorized the Earth was the center of the solar system and all celestial bodies revolved around it Geocentric

Early Astronomers Copernicus In 1543 created a new theory about the movement of celestial objects He theorized the sun is the center of the solar system not the Earth Heliocentric

Early Astronomers

Early Astronomers Brahe Disputed Copernicus’ theory Believed the Earth was the center, and the solar system revolved around the Earth

Early Astronomers Kepler Sided with Copernicus, but discovered the orbits of the planets are elliptical not circular

Early Astronomers Galileo In 1609, he became the first person to use a telescope to observe celestial bodies Contributions 4 moons of Jupiter Craters/mountains on the moon Sunspots on the sun Phases of Venus Showed planets as more than dots of light but actual physical bodies like the earth

Early Astronomers Sir Isaac Newton Explained why planets orbit the sun and moons orbit planets Gravity

Mapping the Stars Constellations - sections of the sky that have recognizable star patterns. Different cultures had different names There are a total of 88 constellations The constellations change from season to season

Common Constellations

Aries

Cancer

Aquarius

Finding stars in the Night Sky Concepts that describe the location of a celestial object Altitude – the angle between the object and the horizon Zenith – an imaginary point directly over the observer……. Always 90 degrees Horizon – the line where the sky and Earth appear to meet …….. Always 0 degrees

Astrolabe

Sextant

Describing a Star's Position Celestial equator – an imaginary circle created by extending the Earth's equatorinto space. Right Ascention – hours eastward from the vernal equinox. Declination – defrees north and south of the celestialequator. Ecliptic- the apparent path the sun takes across the sky

Circumpolar Stars Circumpolar stars – stars that can be seen any time of the year and at any time of night. * found near the north and south pole areas Animation

Telescopes and the Electromagnetic Spectrum Section 3

Optical Astronomy Optical telescope Collects visible light for closer observation 2 lenses Objective lens: collects light and forms an image at the back of the telescope Eyepiece: magnifies the images from the objective lens

Without an optical telescope you can see about 6,000 stars With an optical telescope you can see millions of stars

Refracting Telescopes Use a set of lenses Curved objective lens bends light and focuses it to the eyepiece Eyepiece lens magnifies the image Disadvantage: if the curved lens is too large the glass will sag and distort the image Disadvantage: imperfections in glass can distort image

Reflecting Telescopes Use curved mirrors Large curved mirror reflects light to a focal point The focal point reflects light to the eyepiece Advantages: Mirrors can be made very large Mirrors are polished on one side to prevent flaws from glass Mirrors reflect light of all colors to the same place

Optical Telescopes Continued http://www.astro-tom.com/telescopes/telescopes.htm

Hubble Telescope

What do you think would be an advantage to having a telescope in space compared to one on Earth?

Electromagnetic Spectrum Made of all the wavelengths of electromagnetic radiation Visible light is only a small portion Earth’s atmosphere allows these in…. Infrared, visible light, some ultraviolet, and radio Earth’s atmosphere blocks…. Gamma, X rays, some ultraviolet Astronomers can detect…. Visible light, infrared, and radio waves

Non Optical Telescopes Radio telescope -n telescope designed to listen for radio waves (sound) coming from space. X-ray Telescope – designed ton detect x rays that are coming from space. This telescope can only be used in space because the Earth's atmosphere blocks all x rays. Infrared Telescope – a telescope that uses infrared light to detect celestial bodies.

Radio Telescope

VLA (Very Large Array)