Astronomy 2022 October 10-12

center of mass, where the lines between two stars intersect

if the light source is moving towards the observer, the observed waves become shorter and blue shifted, if moving away, longer and red shifted. Used to measure the radial velocity

speeds of objects moving towards or away from earth, motion is parallel to the line of the observer

some binary stars are so far away it’s impossible to see stars, but the Doppler effect and their colors reveal which is orbiting towards us and which is orbiting away

the Doppler shift shows the star’s speed (v), we then observe the tie it takes to complete one orbit (p). using these we can determine the circumference of the orbit, from that we can find the radius and “a”.

binary stars whose orbits are aligned edge on from our line of sight, light dims as one star passes in front of and then behind the other star

described in the Cairo calendar and is the oldest, recorded naked-eye observation fo an apparent variable star

shows how the combined light from both stars changes due to eclipses over the time span of an orbit

stars that orbit in a plane that lies in the line of sight of the observer

method of determining stellar radii. Most accurate method to determine mass of a star, used to combine images from 2+ telescopes to obtain higher resolutions. Can measure P by timing eclipses, V with the Doppler effect, and orbital speeds/periods to determine A

determines stellar radii, if radius and mass are both in solar units, then radius= mass^.8

determines stellar radii, combines light from several telescopes, worlds largest telescope

determines stellar radii, radius of a star can be determined from its luminosity and temperature

determines stellar radii, when a star passes in front of another. During the time interval between contacts 1 and 2, smaller star moved a distance equal to its own diameter, and during time between 1 and 3, diameter of larger star

determines stellar radii, passage of the Moon, as it moves through the nighttime sky, in front of a celestial object, such as a star or planet

a star’s position appears to move back and forth with respect to the background stars, in a yearly cycle

type of stellar motion, how fast a star is moving directly towards or away from earth. Measured using Doppler effect. (change in wavelength)/(laboratory wavelength)

type of stellar motion, combination of radial velocity, proper motion, and distance. How the star actually moves through the three dimensions

a recognizable pattern of stars, like Pleiades cluster, hyades cluster

type of stellar motion, the angular motion of a star across the sky, typically around .1 arc sec/year. A star with .1 arc sec/year would move 10 arc seconds in 10 years. It would take thousands of years to notice this in a star

a red dwarf star 6 light years away in Ophiuchus, apparent magnitude 11.2, largest observable proper motion (10.25 arc sec/yr)

archives (compare images of the sky taken years apart, Paris observatory, palomar all sky survey). Data from the Gaia spacecraft has supplied proper motion for 2.5 million stars. can be measured out to about 1k pc

discovered the proper motions of Arcturus, Sirius nad Aldebaran by comparing the star charts of Hipparchus to current star charts

depends on star’s distance and speed. The more distant star will have a smaller angle, closer will have larger