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Q & A: Regulus’s Declination

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Most recent answer: 10/22/2007
Regulus is a bright star regulus appeared to move across the sky chose from north east south west please help me
- rachel (age 12)
Rachel -

Regulus (also called 'Alpha Leonis') is a /very/ bright star located in the constalation Leo. In fact, it's the 21st brightest star in the entire sky! There's two different ways that you can think about how it moves. The first is really simple. Since the Earth rotates all the time, it looks like the stars are moving overhead. So, just like the Sun will rise in the East and set in the West, all the stars in the sky will look like they move from the East to the West. But this doesn't have to do with the star actually moving with respect to Earth... just with the Earth spinning around its axis.

But, stars don't stay in exactly the same place all the time. Both the sun and Regulus do move through space very slowly. A way of measuring this is by looking at the 'declination' of the star. Declination is a lot like latitude, only for things in space. It's basically the same as if you figured out the latitude that you'd have to be at for the star to look like it was straight above you.

In 1900, the declination of Regulus was +12.27'; in 1950, it was +12.12'; and in 2000, it was 11.58'. This means that if you were standing somewhere where the latitude is 12.27' in the year 1900 (like if you were in Nicaragua), it would look like Regulus was straight overhead. But as time went on, you'd have to move a little bit farther North to keep it straight overhead. So in 2000, it looked like it was just a tiny bit farther North than it did in 1900, as if it were slowly moving from the South to the North.


(published on 10/22/2007)

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