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What distance must astronomers know before using parallax to determine the distance to a star?
Wiki User
∙ 10y ago
The baseline distance is one astronomical unit, the average radius of the Earth's orbit.
Measurements of a star's position against the background of distant stars are made at intervals of 6 months, when the Earth is at two different places, to measure the parallax and hence the distance to individual stars.
For a parallax of 1 arc-second the distance is 1 parsec, equal to a distance of 3.26 light-years. In astronomical data, stars' distances are quoted in parsecs.
In the 19th century Bessel was the first astronomer to measure parallax and so discover that the stars are at distances that are much larger than was thought possible before then.
Even the closest stars have a parallax of under 1 second of arc, and until the 19th century the apparent absence of parallax in stars was taken as a major proof that the Earth cannot be in motion round the Sun, and this was quoted by Galileo (among many others) before he adopted the Copernican heliocentric system later.
Wiki User
∙ 10y ago
Wiki User
∙ 14y agothey use it in relation to the moon!
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Why must a star's parallax be known before you can find the luminosity?
What must be known is the distance. And the most accurate method to measure the distance of nearby stars is the parallax - but this method won't work for stars that are far away.
Do all-stars have measurable parallax angles?
No, only the closer ones have a parallax that is large enough to be measured. The first star to have its parallax measured was 61 Cygni, measured by Bessel in 1838 and found to be at a distance of 10.3 light years, later corrected to 11.4. The closest star Proxima Centauri has a parallax of only about 0.7 seconds of arc. Before then the absence of parallax for the stars was considered an important part of the case that the Earth cannot be revolving round the Sun.
Before the telescope was invented what were ancient astronomers able to learn about the planets?
before the teloscope was invented what were ancient astronomers able to learn about the planets ?
How did astronomers know Neptune existed before they could see it?
Astronomers knew that Neptune existed before they could see it because they observed that the other planets orbited the sun in a way that could only be explained if they were being influenced by the gravity of another object of such mass. So the astronomers contemplated that there must be another planet somewhere that was changing the orbits of other planets. That planet is today called Neptune.
Why do astronomers say that looking at constellations is looking into the past?
Because of the speed of light. A light year is a term of measurement of distance, not time - i.e. the distance that light can travel in one year. Light travels at 299,792,458 metres per second - almost 3 million kilometres a second - therefore in one year it would travel a collosal distance - near 94 million million kilometres. When astronomers say a planet is 400,000 light years away, what we see of this planet happened 400,000 years ago since the light is only reaching us now. It would be another 400,000 years before we see that planet as it is today.
Why must a star's parallax be known before you can find the luminosity?
What must be known is the distance. And the most accurate method to measure the distance of nearby stars is the parallax - but this method won't work for stars that are far away.
Do all-stars have measurable parallax angles?
No, only the closer ones have a parallax that is large enough to be measured. The first star to have its parallax measured was 61 Cygni, measured by Bessel in 1838 and found to be at a distance of 10.3 light years, later corrected to 11.4. The closest star Proxima Centauri has a parallax of only about 0.7 seconds of arc. Before then the absence of parallax for the stars was considered an important part of the case that the Earth cannot be revolving round the Sun.
Before the telescope was invented what were ancient astronomers able to learn about the planets?
before the teloscope was invented what were ancient astronomers able to learn about the planets ?
How long do astronomers estimate the sun will last before it begins to die?
Astronomers think the sun will die in 2012
What planet would have no advantage of any kind over earth for making parallax measurements?
You have to ask yourself what is an advantage when parallax measurements are being made? . . parallax happens when you move to a different place and the object you see look a little different, the closest ones appear to have moved more than the ones that are further away. In astronomy parallax is created when the Earth is in opposite points of its orbit. Stars that are close appear to have moved a little, relative to the mass of stars that are a long distance away. Parallax was not observed before the 19th century, and the lack of parallax was always used to 'prove' that the Earth could not possibly be going round the Sun. It was only in the 19th century that parallax was observed, but it was only very tiny movements of the closest stars. It forced people to realise that the stars are incredibly far away and the Earth does go round the Sun after all, so it was extra evidence of the Sun being at the centre of the solar system. A parallax measurement is easier to make if the baseline is longer, so the answer to your question is that Mercury and Venus have no advantage for making parallax measurements.
When i see a storm cloud in the distance is their a way for me to determine how long it will be before it reaches me and starts raining?
If you know how far the could is from you, and watch the cloud and determine its speed (distance/time) you can use math to determine when it will move over you, and if it looks dark and such, then there is a good chance it will rain, but that is mostly a guess using probability.
Why do we use parallax?
As Earth orbits the Sun individual stars seem to move their position against the celestial background. The nearer a star is to is, the greatest that apparent move is. That apparent change in the stars position is known as its parallax. A star close enough to show a change of 1 second of an arc is said to be at a distance of one parsec. No star is actually that close. Proxima Centauri, the nearest start to us after the Sun, is 0.75 of a second of an arc. One parsec is equivalent to 3.76 light years. The farther away a star is, the smaller its parallax. Stars over 50 light years away have a parallax that is too small to measure, even with the most powerful of telescopes. Only about 1000 stars have an accurately measured parallax. Beyond that, the absolute magnitude of a star is used to estimate its distance, which relates to its brightness.
Which information is needed to determine the horizontal distance a projectile travels?
-- the initial horizontal speed of the projectile -- the time it remains in flight before it hits the ground
What apparent shift is in the position of an object when viewed from two places?
Parallax. A comparatively small spacing of observation allows estimation of much greater distances. For example, just the distance between our eyes, a bit more than an inch, allows us to notice which of two buildings hundreds of feet away is the closer. In the days before laser rangefinding, gunners used double telescopes whose objective lenses could be yards apart to very accurately judge objects more than a mile away. Too see distant stars' distance, we take advantage of the Earth's orbit, and take one set of pictures in the spring and another in the fall (or just six months apart). By comparison with the deep space objects and how much the stars "move" we can estimate their distance. There's even a special term for the huge distances involved: "parsec". At a distance of one PARSEC, a star (or other object) has a PARallax of one SECond of arc (1/3600th of a degree). The "second" here is not the second of time, 1/60th of a 1/60th of an hour, but the 1/60th of a 1/60th of a degree. A parsec is as far as a beam of light could travel in 3.26 years, or just a bit more than 100,000,000 light seconds, each one equal to 300,000,000 meters.
Why didn't astronomers know much about mercury before mariner 10 flew by it?
Because it didn't :)
What scientific concept did astronomers prove long before europeans did?
The Earth is round the earth was round
Why didn't astronomers know much about mercury before mariner 10 flew by?
Because it didn't :)
