Telescopes, Astronomy, and Stellar Evolution

Refractor and Reflector Telescopes

Refractor (lens) - Galileo 1609
Reflectors (mirrors) - Newton 1670 - Cassagrain 1671
Reflectors (mirrors and lenses) - Schmidt 1930

Galileo's Contributions

Lunar surface phases of Venus, an aspect of Mars, 4 major satellites of Jupiter, solar rotation, stellar appearance of the Milky Way, an aspect of Saturn.

Aberration / Image Deficiencies

1) Spherical: Blurry images. It removes focus from the image.
2) Chromatic (color): Images with distinct edges. It is improved by adding a correcting lens.

Telescope Properties

A - Magnification: Number of times the image is enlarged as seen with the naked eye.
P - Resolving power: The ability of a telescope to distinguish or separate two spaced light sources.
d is the diameter of the lens
λ is the wavelength of light rays.

Calendar and Time Units

Schedule: Set of rules adopted by astronomers to try to match the calendar year with the tropical year.
- Calendar year: 365 days
- Tropical year: Time between two consecutive passages of the sun at the Aries Point. It measures 365 days, 5 hours, 48 minutes, and 46 seconds, or 365.2422 days.

Units

Year: Earth's translation, tropical year.
Month: Lunar synodic month (phases), 29.5 days.
Week: Interval between two consecutive phases of the Moon. 7 days.
Monday-Moon. Tuesday-Mars. Wednesday-Mercury. Thursday-Jupiter. Friday-Venus. Saturday-Saturn. Sunday-Sun.
Day: Rotation of the Earth, lasting 23 hours, 25 minutes, and 4 seconds.

Calendar Reforms

Julian Reform (Julius Caesar, 46 BC): Year of twelve months of 30 and 31 days each. February with 28 days, with leap years every four years.
Gregorian Reform (1582): Eliminated more than 10 days of October 1582.
Mobile Dates: Easter and Carnival. 1 day after the full moon of the Aries Equinox (March 21) + 7 days is Palm Sunday. / 7 weeks before, it's Carnival.

Astronomical Distance Units

Short Distance (within the Solar System) - miles and astronomical unit (AU)
Long distance (outside the Solar System) - light-year (ly) and Parsec (pc)
Absolute Magnitude - M

Light-Year and Parsec

Light-Year: 300,000 km/s - 10 trillion km. 1 ly = 0.31 pc
Parsec: Distance corresponding to a parallax of one second. 1 pc = 3.26 ly

Absolute Magnitude

Takes into account the 10 pc distance and is defined as the apparent brightness of a star at 10 pc away. M sun = 5th magnitude, 10 pc
- Frequency: 1 cycle/second = 1 Hz
- Wavelength
= Magnetic spectrum
- Atmospheric windows: Spectrum allowing passage to the Earth

Origin of a Star

1st Stage: A condensed protostar of interstellar dust and gas dispersed in space.
2nd Stage: The protostar shrinks as gravity starts to act.
3rd Stage: On contraction, the temperature at the center rises, reaching the level necessary for nuclear fusion to occur.
4th Stage: The protostar has become a true star that radiates enormous energy.

Stellar Evolution

1) Small Star (up to 1.3 solar masses) - Red Giant -> White Dwarf
2) Large Star (up to 3 solar masses) - Red Giant -> Supernova -> Pulsar
3) Very Large Star (+ 3 solar masses) - Red Giant -> Black Hole

The Sun

Solar Interior: Core, radiative zone, convective zone
Photosphere: Spots, faculae, granulations
Solar Atmosphere: Chromosphere, Corona (solar wind)