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Cepheids - NASA From these observations one determines the period of each of these stars. Leavitt's data states that a given period has a unique brightness associated to it. So from the period and Leavitt's plot we get the brightness at the distance of one light-year (see the image above). We can also measure the brightness on Earth.
StarChild: Galaxies - NASA A light-year is the distance light travels in one year. It is 9.5 trillion (9,500,000,000,000) kilometers. The size of a galaxy may be as little as a thousand light-years across or as much as a million light-years across.
StarChild: The Dwarf Planet Pluto - NASA Pluto was discovered in 1930 by astronomer Clyde Tombaugh. However, it was not until the year 2015 that we finally got a close-up look at the dwarf planet. After a nine-year journey, NASA's New Horizons spacecraft flew by Pluto, taking pictures and collecting data. We now know that the surface of the dwarf planet is a tannish-red color.
Does the Sun move around the Milky Way? - NASA The Sun (and, of course, the rest of our solar system) is located near the Orion arm, between two major arms (Perseus and Sagittarius). The diameter of the Milky Way is about 100,000 light-years and the Sun is located about 28,000 light-years from the Galactic Center. You can see a drawing of the Milky Way below which shows what our Galaxy ...
StarChild Question of the Month for April 2001 - NASA The sidereal period is the time required for a celestial body within our solar system to complete one revolution with respect to the fixed stars‹i.e., as observed from some fixed point outside the system. The sidereal period of the Moon is the time needed for it to return to the same position against the background of stars.
Just How Big is this Place? - NASA A light year is equal to 9,500,000,000,000 km and is the distance that light travels in one year. A light year can be expressed as 9.5 trillion km or in scientific notation as 9.5 x 10 12 km. The star outside of our solar system that is closest to Earth is Alpha Centauri C.
Round and Round They Go! - NASA In words, the pull exerted on one body by another equals Newton's Constant times the mass of the first body times the mass of the second body divided by the square of the distance between the centers of the two bodies. Notice that in this equation, there is no distinction between which body is doing the pulling. Think about what this means.
Why is the crescent moon sometimes lit on the bottom? - NASA The Moon does not generate any light of its own. So the lit part of the Moon always points toward the Sun. Now as you can see in the diagram, as the Earth travels aroound the Sun, the tilt of the Earth on its axis sometimes points the northern hemisphere toward the Sun and sometimes points the southern hemisphere toward the Sun.
What is a light-year and how is it used?? - NASA What is a light-year. and how is it used? Answer: A light-year is a unit of distance. It is the distance that light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 trillion km. More p recisely, one light-year is equal to 9,500,000,000,000 kilometers.
Where do comets come from? - NASA Although the Oort Cloud is much farther away from the Sun than the Kuiper Belt, it appears that the Oort Cloud objects were formed closer to the Sun than the Kuiper Belt objects. Small objects formed near the giant planets would have been ejected from …
