Galaxy Zoo Starburst Talk

What's that?

  • SuperSupremePizza by SuperSupremePizza

    What's the object in the center?


  • fatha731 by fatha731

    In the centre? I don't see anything. The bulge is very bright if that's what you mean.


  • JeanTate by JeanTate in response to Haitham94's comment.

    It's a foreground star, in our own galaxy (bretarn was right)! Nice find ... though it will probably mean we have to throw it out of our sample.

    How to tell? From the spectrum:
    enter image description here

    There's a prominent, unmarked, absorption line at ~656.4nm, and another, not so prominent at ~486.2nm. One is probably enough to tell, but both makes it certain: these are H-alpha and H-beta, close to their 'rest wavelengths'. Look closely, and you'll find all the other Balmer lines too; so this is a foreground (z~=0) A (or perhaps F) star. I'm sure Laura - or any other of the GZ professional astronomers - could overplot an A star spectrum, at z=0, and remove it, giving us the background galaxy (nucleus/bulge) one.

    One mystery (for me): what's the unmarked, very strong (and narrow) absorption line at ~393.4nm? It's between two Balmer lines, Hε (396.9) and H8 (388.9)


  • JeanTate by JeanTate

    Silly me! The line at 396.8, which I said was Hε, is actually the famous Fraunhofer "H" line (or a blend of Hε and H); and the 'mystery' line (at ~393.4nm), is its sibling (or twin), the "K" line. Due to (singly ionized) Ca. Making the foreground star more likely to be an F than A, perhaps even a G ...