Sunday, February 26, 2017

What are we hurtling towards?

Outline of Virgo Author: AugPi at en.wikipedia

This is not a project idea, but an interesting question. It will help you exercise your reasoning and visualizing skills.
At any moment, the earth, as a whole, has a velocity in relation to the solar system due to its orbital motion around the Sun. Consider the stars as providing a frame of reference. If you represent earth’s velocity as a vector, it is pointing roughly in the direction of some star. Given that there are 92 relatively bright stars in the sky (the Wikipedia lists 92 stars brighter than magnitude 2.49), it would be nice to find a way of mapping the earth’s orbital velocity on any given night to one of these 92 stars. Then we can tell anyone interested that the earth is hurtling that night roughly in the direction of that star.  What a simple way to do this mapping? 

The first satisfactory answer posted as a comment on this blog will earn the author an honor. If the first name of the author is, say Herman, we will name star concerned as “Herman’s Star”. (Don’t make a mistake; “Herman” is used only to give an example. The star is going to be named after you!) A second clarification: Herman’s Star is not one particular star. At any given moment, there is one star which qualifies to be called thus. Over a period of time, different stars would qualify to be called Herman’s Star, one after another. To use another example, on any given date there is one Mayor in a given city, but the Mayor is replaced periodically.
A sub-question: Can every one of the 92 stars mentioned above be a Herman’s Star during your lifetime?

Let me not say more, I do not want to give you too many hints!


aj said...

My guess is that the star in that list, which is closest to the point of intersection of the ecliptic to the local meridian at sunrise would be the one we're hurtling towards. This is due to the fact that Earth's orbital motion at any instant would be perpendicular to the direction of the sun, in that direction.
Sub answer: No, many of the stars in that list are nowhere close to the ecliptic, and earth's orbital plane doesn't precess enough in one lifetime for them to be in the direction of the vector of Earth's motion.

Srinivasan Ramani said...

Please read through AJ's answer above. Is it correct? Do you have any comments on it?

Srinivasan Ramani said...

AJ (Adarsha Joisa) has won this competition. His answer is right on both counts - main question as well as the sub-question. Visit my new blog post for details Adarsha's Star

So, we define Adarsha’s Star on a given day as follows:
the star in a given list of brightest stars, which was closest to the point of
intersection of the ecliptic with the local meridian at 6 AM on that day.