How distant are stars?

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Speed of light: ​

Distance = Speed x Time (d = v * t)

​1.5 x 10¹¹ = 3 x 10⁸ * t

t = ​500 seconds

• Divide by 60 to get minutes -> 8.3 minutes​

1) Trigonometric Parallax

2) Standard Candles​

• ​Cepheid Variable

• ​Type Ia Supernovae

Methods to Determine Distance

​To determine stars that are farther away, we use the standard candle method.

• Light sources which are further away appear fainter because the light is spread out over a greater area.

• If we know how luminous a source really is, then we can estimate its distance from how bright it appears from Earth.​

• Used to determine the distance of nearby stars

• Apparent shift of object with respect to the background

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• Looks like your thumb has moved while ​more distant objects have remained in place

• Approximately 93 million miles​

• Distance to a star that has a parallax angle of 1 arcsecond​

• Appears to shift by only the diameter of a dime at a distance of 2.4 km (about 4.2 light-years away)

• It is in the southern constellation of Centaurus, and is not visible from most of the United States.​

A bit about constellations

• ​Constellations are a group of stars that make an imaginary shape in the night sky.

• They are usually named after mythological characters, people, animals and objects.

• In different parts of the world, people have made up different shapes out of the same groups of bright stars.

Orion the Hunter

• For example, the constellation we now call Orion the Hunter was seen as different shapes by different people around the world, including:

  • China: Shen, the supreme warrior

  • Egypt: Orion or Osiris in Ancient Egyptian traditions

  • India/Hindus: Skanda, a celestial General riding a peacock​​

Constellations

• ​Today astronomers recognize 88 “official” Constellations. To be able to see all 88 Constellations, we would need to be at the equator.

• ​Brightest star in constellation is alpha, then beta, then gamma, then delta, etc

https://www.youtube.com/watch?v=CWMh61yutjU&list=WL&index=21​

• Add information from today.