If we imagined that the distance from the Earth to the Sun was 1 Centimeter….. Sun Earth 1 Centimeter
How far away do you think the next nearest star would be??? 2.5 Kilometers 1.5 miles
In real distance, the next closest star would be 300,000 times the distance form the Earth to the Sun, or…… Earth Proxima Centauri Sun 39 Trillion miles (that’s 4.24 Light Years!)
In the Universe, however, the kilometer is just too small to be useful. For example, the distance to the next nearest big galaxy, the Andromeda Galaxy, is 21,000,000,000,000,000,000 km. This is a number so large that it becomes hard to write and hard to interpret. So astronomers use other units of distance. Andromeda Spiral Galaxy Earth 21,000,000,000, 000,000,000 kms
The basic unit of measurement of distance inside of our solar system is the… Astronomic Unit
An Astronomic Unit is equal to the distance from the Sun to the Earth, which is about 93 million miles. 93 million miles Earth Sun
Planets inside Earth’s orbit have distances from the Sun of less than 1 AU. (Mercury is .4 AU’s from the Sun.) .4 AU’s Sun Mercury
Planets outside the orbit of the Earth have distances from the Sun of greater than 1 AU. (Mars is 1.5 AU’s and Pluto is 39 AU’s from the Sun.)
But, Astronomic Units are too small for measuring distances outside of our own Solar System.
The closest star to the Sun, Proxima Centauri, would be more than 300,000 AU’s from our star, and that’s the closest!
Astronomers use Light Years to measure distances outside our Solar System.
A Light-Year is a unit of Distance. A Light Year is equal to the distance that light can travel in one Earth year. A Light Year is equal to 5.3 trillion miles. Use of Light Years makes the units used in measuring distances in Space smaller, but “small” is pushing it!
The Speed of Light is 186,000 miles per second. Peeoooummmmmmm!!! That is almost 8 times around the Earth in 1 second!
Big Bang Theory • The universe originated from the instant expansion of an extremely small agglomeration of matter of extremely high density and temperature.
Scientists learn about the Universe by collecting Wave- Energy from the Electromagnetic Spectrum
The Electromagnetic- Spectrum is a continuum depicting the full range of Electromagnetic Radiation, with the longest wavelength at one end, and the shortest at the other.
Electromagnetic Radiation is energy in the form of a Wave, resulting from the motion of electric charges and the magnetic fields that they produce.
Electromagnetic Spectrum Visible Light
Objects in space emit energy in several different Frequencies and Wavelengths. Frequency Wavelength
The Spectroscope and the Visible Spectrum When light passes through a prism and out again, they are refracted, or bent, forming a band called the Visible Spectrum.
Stars emit light that falls within the visible spectrum. Scientists use an instrument called a Spectroscope to separate this starlight into its colors so that it can be studied.
Spectroscopes break light into three different types. • Continuous Spectrum • Emission Spectrum • Absorption Spectrum
Emission Spectrum of Hydrogen By studying these different spectra, and comparing the emission/absorption spectra of stars to those of gaseous elements in a lab, astronomers can determine the types of elements that make up the atmospheres of the stars that emitted the light. Absorption Spectrum of Hydrogen
Scientists use Spectral Analysis to not only determine what gases are present in stars, but also how they are moving relative to the Earth. The Doppler Effect This is possible because of a phenomenon called the Doppler Effect.
Let’s look at an example of the Doppler Effect that you have all experienced. The Doppler Effect also applies to Light.
Because of Doppler Shift, scientists have determined that our Universe is expanding Bright Line Spectrum
How are Stars and Planets different? • They differ in a lot of ways, but for the moment, we will focus on the fact that: • Stars emit light, due to nuclear fusion in their center, while planets only reflect light.
The Life Cycles of Stars Dr. Jim Lochner, NASA/GSFC
Life Cycle of a Star Foldable
Stage 1 Stage2 Stage 3
Stage 1 Stage2 Stage 3 Main Sequence Star (stars like our Sun) • Nebula spins & flattens • To form a protostar • Protostar shrinks due to • gravitional attraction. • Temp , Pressure , light • and heat are emitted • Energy is produced from • Nuclear fusion of H2 into • He begins – moves to next stage • Core temp to a point that He • can fuse into heavier elements • (O2 and C) • H2 into He continues in the • outer layers. • When Hydrogen is exhausted • the outer layers blow away • leaving only the carbon-oxygen • core – White Dwarf. • Expelled layer absorbs the • white dwarfs ultraviolet emission • causing a halo affect called a • Planetary Nebula • Main sequence stage, last • the longest • Star stays until all H2 fuel • is used up (converted to He) • He core shrinks and • Contracts to produce • additional heat. • H2 fusion starts in the outer • Layers causing the star to • swells– moves to next stage. Massive Star • Fusion in core continues until iron • forms • Iron does not release energy so it • absorbs it, thus leading to a quick • collapse resulting in an explosion – • Supernova. • Result of explosion is either a Black • hole or Neutron Star. • Same process however due • to the more massive size it • swells to an even larger size • than the main sequence star • does • Same process however • much more dust and gas • present
Main Sequence Main Sequence Line; Core Fusion of H at constant rate; Volume directly related to mass
Giants Core fusion of He
Supergiants . . . Supergiants
Polaris, the North Star Time-lapse image of circumpolar stars.
Polaris (the North Star) Circumpolar Constellations Little Dipper; Last star in handle is Polaris, the North Star Big Dipper; Two right stars of the “cup” point to Polaris
How is the distance to Star determined: Parallax:
As Polaris is directly above the geographic North Pole, it does not move, to the naked eye, as the Earth spins. Therefore, it was, and still is, a very powerful tool for navigation. Polaris Polaris Geographic North Pole As Polaris is directly above the geographic North Pole, it does not move, to the naked eye, as the Earth spins. Therefore, it was, and still is, a very powerful tool for navigation.
Because of Precession, however, Polaris will not always be the “North Star”