International Celestial Reference System and its realizations
Do you know how we use maps to know where we are on Earth? When we look up at the sky, there are a lot of different stars and objects up there, but how do we know exactly where they are and how they move?
Well, scientists have come up with something called the International Celestial Reference System (ICRS). This is like a map of the stars and objects in the sky. But instead of using latitude and longitude like we do on Earth maps, the ICRS uses something called right ascension and declination.
Right ascension is like the "longitude" of the sky. It measures east-west, or how far an object is from an imaginary line that runs from the north pole to the south pole of the sky.
Declination is like the "latitude" of the sky. It measures north-south, or how far an object is from the celestial equator, which is like the Earth's equator projected onto the sky.
The ICRS is a way to measure the positions and movements of objects in the sky that are really far away, like other stars and galaxies. It's important because it helps astronomers share their observations with each other and track things in the sky over time.
But the ICRS isn't just one map - there are different ways to make the map depending on how you take measurements and what objects you're interested in. These different ways of making the ICRS are called realizations.
So just like there are different kinds of Earth maps, there are different kinds of ICRS maps. And just like how different maps can be useful for different purposes, different ICRS realizations can be useful for different kinds of astronomical research.
Well, scientists have come up with something called the International Celestial Reference System (ICRS). This is like a map of the stars and objects in the sky. But instead of using latitude and longitude like we do on Earth maps, the ICRS uses something called right ascension and declination.
Right ascension is like the "longitude" of the sky. It measures east-west, or how far an object is from an imaginary line that runs from the north pole to the south pole of the sky.
Declination is like the "latitude" of the sky. It measures north-south, or how far an object is from the celestial equator, which is like the Earth's equator projected onto the sky.
The ICRS is a way to measure the positions and movements of objects in the sky that are really far away, like other stars and galaxies. It's important because it helps astronomers share their observations with each other and track things in the sky over time.
But the ICRS isn't just one map - there are different ways to make the map depending on how you take measurements and what objects you're interested in. These different ways of making the ICRS are called realizations.
So just like there are different kinds of Earth maps, there are different kinds of ICRS maps. And just like how different maps can be useful for different purposes, different ICRS realizations can be useful for different kinds of astronomical research.