Estrella vs astro (heavenly bodies)

Estrella vs astro (heavenly bodies)
 

Hi,

Are these words exactly synonymous? Connotations and all?

No, to me they are not the same. All "estrellas" are "astros", but not all "astros" are "estrellas".
An "astro" is any celestial body (sun, moon, planets, comets, stars...), but "estrella" is only a star, understood as a mass of hot, gaseous, self-luminous celestial body, like the sun.

- Los astros dicen que serás millonario.
The stars say you'll be a millionaire. -> Astrology believers use all kinds of celestial bodies, so we say "astros", not "estrellas". :)
- El astro/la estrella de Hollywood, Johnny Smith, falleció esta madrugada.
The Hollywood star, Johnny Smith, died early in the morning. (In this case they're perfect synonyms.)
- Los antiguos dioses tenían los nombres de los astros.
The ancient gods had the names of the celestial bodies.
- Los movimientos de rotación y translación de la tierra causan el movimiento aparente de los astros.
The earth's rotation and revolution cause the apparent motion of the celestial bodies.

Thanks!

So, talking about human stars, they don't have to agree in gender?

Johnny Smith can be either astro or estrella, whatever they wish?

"Astro" in singular, is only for men. "Estrella" is more often used for women, but it may be used for men too.

- La película tiene en los papeles principales a la estrella Penélope Cruz y al astro Javier Bardem.
The main roles of the movie will be played by Penélope Cruz and Javier Bardem.
- El astro del basquetball ahora busca convertirse en estrella de Hollywood.
The great basketball player now wants to become a Hollywood star.
- Robert Downey Jr., estrella de películas de superhéroes, visita niños en el hospital.
RDJ, star in super hero movies, visits children in hospital.
- Test: ¿puedes nombrar a todas las estrellas de las siguientes fotografías?
Test: can you name all the stars in these pictures? (Men and women included in this particular case, where I found the sentence.) ;)
- Anne Hathaway, la estrella de películas como Les Misérables, filma en nuestro país.
Anne Hathaway, the star in movies like Les Misérables, is filming in our country.