Comments on: Astronomers Use Light Echos to Measure the Distance to a Star http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/ Space and astronomy news Sun, 8 Nov 2009 10:14:11 -0600 http://wordpress.org/?v=2.8.5 hourly 1 By: David Madison, Sr. http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/comment-page-1/#comment-12083 David Madison, Sr. Tue, 12 Feb 2008 17:42:45 +0000 http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/#comment-12083 1. They are only absolute if you already know the relationship between their distance, variable period, and average brightness. The distance ladder that we calculate the scale of the universe depends on the parallax, which is reliable only to approximately the distance of the closest Cepheid. This introduces uncertainty in the Cepheids’ distance. That this particular one, the only one, embeds in a nebula gives us a means to verify their triple relationship. 1. They are only absolute if you already know the relationship between their distance, variable period, and average brightness. The distance ladder that we calculate the scale of the universe depends on the parallax, which is reliable only to approximately the distance of the closest Cepheid. This introduces uncertainty in the Cepheids’ distance. That this particular one, the only one, embeds in a nebula gives us a means to verify their triple relationship.

]]> By: Ken VanLew http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/comment-page-1/#comment-12072 Ken VanLew Tue, 12 Feb 2008 15:32:42 +0000 http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/#comment-12072 Hi Frazer, Cepheid variables give absolute, not just relative distance, using the distance modulus formula. Once period is known, absolute magnitude is known, and by comparison to apparent magnitude, we have distance. What is the meaning of the statement, "But this only tells you how far they are relative to one another." in your article? Thanks, Ken Hi Frazer,
Cepheid variables give absolute, not just relative distance, using the distance modulus formula. Once period is known, absolute magnitude is known, and by comparison to apparent magnitude, we have distance.
What is the meaning of the statement, "But this only tells you how far they are relative to one another." in your article?
Thanks,
Ken

]]> By: Bryan A. http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/comment-page-1/#comment-12044 Bryan A. Tue, 12 Feb 2008 05:25:25 +0000 http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/#comment-12044 I get it - it took hours. Scientists measure the ARC in the field of view that's created by measuring between the peaks of two waves. The speed is constant, the time is constant and the arc is established and distance figured. Wow. What a video too! I get it – it took hours. Scientists measure the ARC in the field of view that's created by measuring between the peaks of two waves. The speed is constant, the time is constant and the arc is established and distance figured.

Wow. What a video too!

]]> By: just Physics! » Blog Archive » Physics alerts … http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/comment-page-1/#comment-12023 just Physics! » Blog Archive » Physics alerts … Tue, 12 Feb 2008 01:03:53 +0000 http://www.universetoday.com/2008/02/11/astronomers-use-light-echos-to-measure-the-distance-to-a-star/#comment-12023 [...] that students - or anyone else, for that matter - can use at no charge. “I’m amazed by Astronomers Use Light Echos to Measure the Distance to a StarUniverse Today - If you want more info on this, check an episode of astronomy Cast where we measure [...]

[...] that students – or anyone else, for that matter – can use at no charge. "I'm amazed by Astronomers Use Light Echos to Measure the Distance to a StarUniverse Today – If you want more info on this, check an episode of astronomy Cast where we measure [...]

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