Chapter 21. STARS. Characteristics of Stars. Groups of stars that form patterns in the sky are called constellations Example: Ursa Major (Big Bear), Ursa Minor (Little Bear), and Orion
The apparent motion of stars is due to the Earth’s daily rotation on its axis.
The stars don’t move – WE DO!!!!
Ex – when the Earth is in this position (Nov 21), the bright sun during the day blocks our view of all of the constellations toward the lower right side of the diagram
(See the H-R Diagram in the ESRT’s P.15)
One Astronomical Unit (AU) = 150,000,000 km
And, one light year (LY)= 9.5 trillion km(9,500,000,000,000 km)
Okay… let’s calculate the distances from Earth to each planet in Astronomical Units (AU)
Just divide the distance from the Sun in km by 150,000,000 km.
Example: Jupiter = 778,300,000 km 150,000,000 km
Jupiter is 5.19 AU from the Sun
occur at the end of a star's lifetime, when its nuclear fuel is exhausted and it is no longer supported by the release of nuclear energy
SUPERNOVA 1987 – right image is the star that became the left image after going supernova – shone brighter than most galaxies for a few months!
Here are some images of nebulae, courtesy of our friend Hubble…
8000 LY FROM EARTH – 200 LY ACROSS
5000 LY FROM EARTH - 10,000 YRS OLD
7,000 LY AWAY FROM EARTH
YOUNGEST KNOWN NEBULA – 130 SOLAR SYSTEMS ACROSS – 18,000 LY AWAY FROM EARTH
I WANT MY MOMMY!!
(UP TO 1.5 X MASS OF OUR SUN)
(1.5 – 3 X OUR SUN)
STARS FORM IN A NEBULA OF GAS & DUST
> 3 X OUR SUN
STAR COOLS ARE SHRINKS BECOMING ONLY A FEW THOUSAND MILES ACROSS!
NO NUCLEAR REACTION
LONGEST, MOST STABLE PERIOD OF A STAR’S LIFE – CONVERTS HYDROGEN TO HELIUM, RADIATING HEAT & LIGHT
STAR LOSES ALL HEAT TO SPACE AND BECOMES COLD AND DARK CARBON BALL
NUCLEAR FUEL DEPLETES, CORE CONTRACTS, SHELL EXPANDS
OUTER LAYERS DRIFT OFF INTO SPACE IN SPHERE-LIKE PATTERN
Betelgeuse a red supergiant, with about 20 times the mass and 800 times the radius of the Sun, so huge that it could easily contain the orbits of Mercury, Venus, Earth, Mars & Jupiter. It will probably explode as a supernova at some point within the next 100,000 years. Even at its relatively remote distance, it normally ranks as the tenth brightest star in the sky.
Rigel, a blue supergiant, has a diameter of about 100 million kilometers, some seventy times that of the Sun. Within a few million years, it will probably evolve to become a red supergiant like its neighbor in Orion (though not in physical space), Betelgeuse.
3,700 LY wide dust-disk encircling a 300 million solar mass blackhole in the center of an elliptical galaxy.
The disk is a remnant of an ancient galaxy collision and could be “swallowed” up by the blackhole in a few billion years.
Ursa Major’s galaxy (a galaxy that we can see within the constellation) –
50 million LY from earth!
Overlapping Spiral galaxies – 140 million LY from earth – within the constellation HYDRA
Hoag’s Galaxy – 120,000 LY wide – perfect ring of blue stars surrounding older nucleus of yellow stars