{ Astronomy Unit 3 What we’ve learned so far…

 There are 7 types (from longest to shortest wavelength)  Radio, Micro, Infrared, Visible, Ultraviolet, X-ray, Gamma Rays  Radio has lowest energy and lowest frequency, Gamma has highest energy and highest frequency *** They ALL travel at the speed of light: 3 x 10 8 m/s  A light year is how far light travels in 1 year. The Electromagnetic Spectrum…

 Constellations are star patterns in the sky  There are two names for each constellation  The zodiac has 13 constellations, but only 12 signs. (1 is on the ecliptic, but doesn’t fit the calendar)  The stars are NOT the same distance from us.  Because of the Earth’s precession, the zodiac symbols don’t match what’s in the sky. Constellations

 Describes a position in space.  Right Ascension (like longitude) is measured eastward along the celestial equator (units: hours, minutes, and seconds). Based on the Vernal Equinox, when the Sun cross the celestial equator.  Declination: (like latitude) is measured up or down from the celestial equator (units: degrees (˚), then minutes (‘), and seconds (“)). Right Ascension and Declination…

Precession Precession is the Earth’s “wobble” around its axis. The whole cycle takes 26,000 years. Because of precession our current North star is Polaris. In 12,000 years our North star will be Vega, and 5,000 years ago it was Thuban. Precession is why the zodiac constellations don’t match up.

Eclipses  Lunar Eclipse: When the Earth is between the moon and the Sun. Earth shadows cover the moon.  Solar Eclipse: When the moon crosses between the Sun and the Earth.

Sidereal vs. Tropical  In a little less than 24 hours the Earth rotates 360˚ in space (sidereal day)  A sidereal day is less than 24 hours, and is a rotation relative to space.  A tropical day 24 hours, the Earth rotates 361˚.  A tropical day is the Earth’s rotation relative the Sun.  In order to see the same star in the same location the next day, you will need to view it 4 minutes EARLIER.

Distances…  The sun is 93 million miles from the Earth.  Rigel 776 light years from Earth  Polaris is 433 light years away..  Sirius is only 9 light years…

Telescopes  What type of telescope did Galileo first use?  REFRACTING!!!!  What is the benefit of using the telescopes at the Mauna Kea observatory?  A thin atmosphere, very large telescopes (less distortion from atmosphere)

Telescopes  Telescopes are “light buckets”  There are 7 types of light  Harder to take images Gamma and X-rays because they are so high-energy and they don’t reflect well.  MOST MODERN TELESCOPES ARE REFLECTORS!

Polaris…  Polaris is our CURRENT north star.  Because of precession, our next north star will be Vega, then Thuban  Located in the Ursa Minor.

Light years vs. AU…  Light Years – distance that light will travel in a year. 1 ly is about 6 trillion miles. We use light years to measure when a ruler doesn’t “cut it”.  Astronomical Units (93 million miles) – it’s the distance from the Sun to the Earth. AU’s are used in our Solar System.

Earth’s surface!  Is constantly changing. There are fewer craters on Earth compared to the moon or some other planets because the atmosphere “burns them up”. Also, weathering takes on Earth, and tectonic plate action causes the Earth to change.