Mechanism

Creativity with ROI Advertising? Email info@mechanism.com for more information

How to Measure Asstronomical Distances: An Introduction

What are the distances we come across in our daily lives? One km, 10 km, 100 km, 1000 km, or even 50,000 km. But the distance between the sun and earth is approximately 150 million kilometers (i.e. 150,000,000 km). So how to scientists make such large astronomical measurements? Up to a certain level (i.e. within our solar system) we can follow some direct precise measurement methods. But beyond that we have to rely upon photometry and spectroscopy.

The extragalactic distance scale is known as cosmic distance ladder (a series of methods used to determine the distances of celestial objects with each step building upon the results of the previous step). By extending the ladder, we can measure larger and larger distances which implies that the base of the ladder refers to direct measurement techniques like RADAR, LiDAR etc.

RADAR (Radio Detection and Ranging) is not limited to applications within our earth. It can be used to measure the distances up to certain planets in our solar system. The principle of RADAR basically involves sending out radio waves and receiving them. The distance of the target is calculated by the time taken for travelling to and fro.

LiDAR is similar to RADAR with the difference being that the light source is Laser pulses instead of radio waves. LiDAR provides accurate measurements but it can be used only within a short astronomical range (say to find the distance between Earth and its moon).

The distance to nearby stars can be studied by parallaxes (a.k.a triangulation). A simple analogy would be to place a pencil in front of your nose and to see it through your left eye and then through the right eye while closing the other eye. You would see the shift in the position of the pencil. This is because the distance of the pencil from your left eye is different than from the right eye. This difference in distance forms the base of an isosceles triangle while the distance to the star forms the lengthier sides of the triangle. The base is taken to be the earth's diameter (measurements taken across two extremes of the earth). As time evolves, the stars appear to shift in position leading a different angle. The difference in angles is used to calculate the distance of the star. The greater the distance, the smaller the parallax (angle). Thus it cannot be used to measure distances larger than few thousands of light years.

To measure the distances of stars at large distances we rely on photometry i.e. measurements are made in terms of their brightnesses. According to the inverse-square law, brightness decreases proportional to the square of the distance. If we know the absolute brightness of a star, then by measuring the apparent brightness of star, we can calculate the distance of the star. The problem here is knowing the absolute brightness of the star whose distance which we don't know. But this problem can be somewhat solved with the help of known neighboring stars.

Apart from a few of the popular methods above, there are many other methods such as observing shift in colour spectrum, Hertzsprung-Russell diagram etc. The major units of astronomical distances are au and parsec although light year is very common.

 

* Image Courtesy Pixabay.com

 

tyogav

tyogav

Top Posts | Aerospace

Get Ready to Experience Mars in Real Time

Space travel is reaching new horizons as the years go by, with plans already in the works to develop colonies on Mars. Until that happens, anyone interested in space and the red planet, in particular, can enjoy a virtual journey of Mars’ surface thanks to a great new program from NASA. As tec ... ...

This Windbot Will Fly over Jupiter Forever

Exciting new space programs are on the horizon as the world turns its attention towards the exploration of the various planets throughout our solar system. After the launch of the famous Curiosity robot that is currently roaming around Mars, NASA now has plans to develop a windbot that will make us ...

The U.S. Air Force Hypersonic X-51A Waverider Program

Just recently the U.S. Air Force teamed up with Defense Advanced Research Project Agency (DARPA) to sign a new contract. The group will continue working on the X-51A Waverider program that the Air Force began in 2004. The hypersonic flight program was given a $300 million budget to develop a hypers ...

Futuristic Jetpacks are Here!

Martin Aircraft Co in New Zealand was originally established as a research and development company. However, this year at the International Paris Air Show the company introduced their new Martin Jetpack. The new jetpack is a fan-propelled personal flying machine that will be available next year. Bu ...

Nasa to Bring in Cheap Supersonic Air Travel

The number of air travel passengers is expected to rise within the next five to ten years, and NASA is working on a solution involving eco-friendly and cheap supersonic air travel along with some industry partners. If everything goes well, we might have commercial supersonic flights in 15 years, or ...

3D Printed Rocket Engines Open Door to Space Entrepreneurs

A satellite launch can cost from $10 million to $50 million, but 3D print technology could see these costs plummet.Cost savingsFor a mere $4.9 million, New Zealand company Rocketlab can send a small satellite up into orbit.  The engine the company uses is called the Rutherford and is ... ...

13 Ways to Write a Brilliant Blog Post on Mechanism

So, you're ready to write an awesome blog post. Fantastic!Here are some useful tips and tricks to get you on your way to blogging glory in no time.Edit It Like You Mean It: While we don't want to play the role of Captain Obvious, editing your blog post for spelling, grammar, and punctuation ... ...

How to Measure Asstronomical Distances: An Introduction

What are the distances we come across in our daily lives? One km, 10 km, 100 km, 1000 km, or even 50,000 km. But the distance between the sun and earth is approximately 150 million kilometers (i.e. 150,000,000 km). So how to scientists make such large astronomical measurements? Up to a certain leve ...