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# Arcturus

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by

## Richard Nguyen

on 25 March 2013

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#### Transcript of Arcturus

Arcturus By: Richard Nguyen RA = 14h 15m 39.7s, Dec = +19° Apparent Magnitude: -0.05
Absolute Magnitude: -0.31 In 1888, Elkin measured the parallax angle of Arcturus to be 0".018 ± 0".022
Another scientist by the name, Peters, also measured the parallax angle; his measurement being 0".127±0".073. The average between these two values, 0".094, can then be used in the Parallax Method to determine how far away Arcturus really is.

1/0.094 = 10.63829787 pc
10.63829787 x 3.26 = 34.68085106 ly

Therefore, Arcturus is about 34.7 light years away! Distance and the Parallax Method This is roughly where Arcturus can be found Location in the Sky Arcturus is located in the constellation, Bootes It is the brightest star in the Bootes constellation and the 4th brightest star in our sky Star Type and Classification As shown by the HR Diagram, Arcturus is a:
Giant, specifically a Red Giant
Class K Star This is Arcturus' present stage These are its future stages Magnitude and Luminosity What is the Parallax Method again?

The Parallax Method is used to measure stellar distances (the distance between us and stars). This method utilizes something known as the parallax angle. The parallax angle is the angle between two instances of the Earth; one time of year and six months later. These values mean that Arcturus should be even brighter than the one we see from Earth!

Arcturus is already the 4th brightest object in our sky; how brighter can it possibly be? Composition and Spectral Class Observed Stage of Life and Age Gallery Example of Another Star Future Lifecycle and Predicted End State Arcturus is currently a Red Giant This means that it is approaching its end state soon Bibliography After Arcturus can no longer sustain fusion reactions in its core, it will then fall to its own gravity and shed its outer layer, which becomes a Planetary Nebula Inside of the Planetary Nebula, which is just a giant cloud of gases, lies the old core of Arcturus. At this point, it should now be a White Dwarf; small, hot and dense After several billions of years, the white dwarf will eventually cool and become a Black Dwarf, an energy-less lump of carbon Black Dwarf Temperature We can use Wein's Displacement Law to determine what the temperature of Arcturus... ...but what is Wein's Displacement Law? 2.9 x 10 6 T = Wein's Displacement Law was discovered by a man named Wilhelm Wien

It states that the higher the temperature of a star, the shorter the wavelength This law can then be simplified into an equation... ...where temperature is in Kelvin and wavelength is in nanometres. The number above the temperature is Wein's constant. Through observations, Arcturus has been found to emit radiation in the infared spectrum

This means that its peak wavelength is 700nm Peak Wavelength If we plug this value into our equation, we would get the approximate surface temperature of Arcturus, which turns out to be 4143K! Like all stars, Arcturus is mainly composed of Hydrogen and Helium

These two elements are undergoing the processes of nuclear fusion at its core Furthermore, we can use the spectral sequence to determine the other elements Arcturus is composed of The black lines on the spectra represent the chemical reactions going on inside a star

If we can figure out what the reactions are, we can figure out what the stars are composed of

From this method, scientists have discovered that Class K stars are also composed of neutral metals

Thus, Arcturus is composed of Hydrogen, Helium, and neutral metals Epsilon Eridani Similarities:
It's a star
Specifically, a Class K Star Differences:
It has a magnitude of about 3.73
Located 10.5 light years away
Has a surface temperature of 5080K
Has planets in orbit around it Mass and Radius We can use the HR Diagram to determine the mass and radius of Arcturus

To do this, we would use the sun as our reference point and compare its location on the diagram to our star's The diagonal lines on this chart show us Solar Radii and Solar Mass

Judging by Arcturus' location, we can say that it has an approximate: