Many of us, while still in grade school, learned about the staggering distances to planets, stars and galaxies. The sun is approximately 150 million km or 93 million miles away, a distance that is known as the "astronomical unit" (AU). Venus, our closest neighbor, is 0.72 AU from the sun, while Mars is 1.52 AU from the sun. Neptune, the most distant planet, is 30 AU from the sun (i.e., 44.8 billion km or 27.9 billion miles). The Voyager 2 spacecraft, launched in 1977, reached Jupiter just two years later, but did not reach Neptune until 1989.
The nearest stars, the triplet Alpha Centauri A, Alpha Centauri B and Proxima Centauri, are roughly 1000 times more distant, approximately 40.7 trillion km (25.3 trillion mi). Such huge distances are …show more content…
It is roughly 2.54 million light-years away. There are hundreds of billions of galaxies in the observable universe. As of the present date, the most distant observed galaxy is some 13.2 billion light-years away, which is more than 5000 times more distant than the Andromeda Galaxy. The age of the universe itself is currently estimated to be 13.75 billion years (plus or minus 0.011 billion years), so this galaxy must have formed soon after the big bang. An interesting online tool, which one can use to determine first-hand the age of the universe from known data, is available at …show more content…
How can scientists possibly measure or calculate these enormous distances with any confidence?
Parallax
The most basic technique is known as parallax, which was first used by German astronomer Friedrich Wilhelm Bessel in 1838. Parallax is not sophisticated -- in fact your eyes use parallax to produce the perception of 3-D vision. If you cover one eye and note the position of a nearby object, compared with more distant objects, the nearby object "moves" when you view it with the other eye. This is parallax.
The same principle is used in astronomy, where instead of using the distance between your two eyes as a baseline, researchers use the diameter of the earth's orbit around the sun, which is 2 AU or approximately 300 million km (186 million mi). As the earth travels around the sun in its orbit, relatively close stars are observed to move slightly, with respect to other "fixed" stars that are evidently much more distant. In most cases, this movement is very slight, only a fraction of a second of arc, but reasonably accurate distance measurements can nonetheless be made for stars up to about 10,000 light-years away, encompassing over 100,000,000 stars. This scheme, which relies on very basic geometry and trigonometry, is illustrated by the following
The nearest stars, the triplet Alpha Centauri A, Alpha Centauri B and Proxima Centauri, are roughly 1000 times more distant, approximately 40.7 trillion km (25.3 trillion mi). Such huge distances are …show more content…
It is roughly 2.54 million light-years away. There are hundreds of billions of galaxies in the observable universe. As of the present date, the most distant observed galaxy is some 13.2 billion light-years away, which is more than 5000 times more distant than the Andromeda Galaxy. The age of the universe itself is currently estimated to be 13.75 billion years (plus or minus 0.011 billion years), so this galaxy must have formed soon after the big bang. An interesting online tool, which one can use to determine first-hand the age of the universe from known data, is available at …show more content…
How can scientists possibly measure or calculate these enormous distances with any confidence?
Parallax
The most basic technique is known as parallax, which was first used by German astronomer Friedrich Wilhelm Bessel in 1838. Parallax is not sophisticated -- in fact your eyes use parallax to produce the perception of 3-D vision. If you cover one eye and note the position of a nearby object, compared with more distant objects, the nearby object "moves" when you view it with the other eye. This is parallax.
The same principle is used in astronomy, where instead of using the distance between your two eyes as a baseline, researchers use the diameter of the earth's orbit around the sun, which is 2 AU or approximately 300 million km (186 million mi). As the earth travels around the sun in its orbit, relatively close stars are observed to move slightly, with respect to other "fixed" stars that are evidently much more distant. In most cases, this movement is very slight, only a fraction of a second of arc, but reasonably accurate distance measurements can nonetheless be made for stars up to about 10,000 light-years away, encompassing over 100,000,000 stars. This scheme, which relies on very basic geometry and trigonometry, is illustrated by the following