Mapping the universe Flashcards
Scientists believe that the universe was created in the ………. and this………… million years ago.
Scientists believe that the universe was created in the ‘Big Bang’ 14,000 million years ago. Since then, the galaxies in the universe have all been moving further apart as space itself expands. Evidence for this comes from observations that astronomers have made of stars.
Since then, the galaxies in the universe have all been ….. ……….. apart as ……… ………… expands.
Since then, the galaxies in the universe have all been moving further apart as space itself expands.
Evidence for space expanding has come from what?
Evidence for this comes from observations that astronomers have made of stars.
what is parallax?
When the observer moves, objects that are closer appear to move relative to ones that are far away.
Parallax makes stars that are nearer to Earth appear to move over the course of a year, relative to stars that are further away. In fact, it is caused by the movement of the Earth around the sun.
Hold one finger up in front of you at arm’s length. Close one eye. Now open that eye and close the one that was open. Repeat this a few times. Your finger seems to move against the background, even though you know that it is actually staying still. That is called parallax.
How do you define a Parallax angle?
The parallax angle of a star is defined as half the angle that a star moves in six months, against a background of very distant stars.
The effect of parallax can be used to measure what?
The effect of parallax can be used to measure how far stars are from Earth. The smaller the parallax angle, the further away the star is.
What is a parsec?
A parsec (pc) is a unit of distance that astronomers use. A parsec is defined as being the distance to a star with a parallax angle of 1 second of an arc.
There are ? degrees in a circle. Each degree has ? minutes in it, and each minute has ? seconds in it.
There are 360 degrees in a circle. Each degree has 60 minutes in it, and each minute has 60 seconds in it.
Each degree has how many minutes in it ?
Each degree has 60 minutes in it, and each minute has 60 seconds in it.
How many seconds are there in one degree of a circle?
there are 3,600 seconds in just one degree of a circle.
1 second of an arc is what size of angle?
This means that 1 second of an arc is a very small angle indeed, which means that a parsec is a very large distance - similar in size to one light year (the distance that light can travel through space in one year).
Is a parsec is a similar distance to what?
This means that 1 second of an arc is a very small angle indeed, which means that a parsec is a very large distance - similar in size to one light year (the distance that light can travel through space in one year).
which start is nearest to Earth.? The next closest star is Proxima Centauri. It has a parallax angle of 0.77 seconds of arc.
The Sun is the nearest star to Earth.
Which star is second closest star ? What is its parallax angle?
The next closest star is Proxima Centauri. It has a parallax angle of 0.77 seconds of arc.
Astronomers measure great distances in megaparsecs (Mpc).
Astronomers measure even greater distances, such as those between galaxies, in megaparsecs (Mpc).
The next nearest galaxy is ?, .
The next nearest galaxy is Andromeda, which is 0.77 Mpc away. This is 770,000 pc. The parallax angle of the Andromeda galaxy would be too small to measure.
How far away is Andromeda?
0.77 Mpc away. This is 770,000 pc.
What is the parallax angle of the andromeda galaxy ?
The parallax angle of the a galaxy would be too small to measure
The luminosity of a star depends on two things - what are they?
its size
its temperature
What are Cepheid variable stars ?
Cepheid variable stars do not have a constant luminosity. They pulse light and their luminosity depends on the period of their pulses (how long each pulse lasts).
How do astronomers to estimate the distance to Cepheid variable stars -
This relationship allows astronomers to estimate the distance to Cepheid variable stars - as long as they know how bright the star actually is and how bright the star appears to be.
What is the Big Bang theory ?
Scientists believe that the universe began with a huge explosion called the Big Bang about 14,000 million years ago.
Edwin Hubble by observing Cepheid variable stars in distant galaxies and concluded what?
Edwin Hubble made observations of Cepheid variable stars in distant galaxies and concluded that the universe is expanding. In fact, the further away a star is, the faster it is moving.
How do scientists work out the value of the Hubble constant?
Because scientists knew how far away some Cepheid variable stars were (their distance) and were able to use the red shift from these stars to calculate the speed with which they were moving away from us (the recession speed), they were able to calculate a value of the Hubble constant.
