Disk Detective Talk

SED crash course?

  • geckzilla by geckzilla

    I'm unfamiliar with SED diagrams. Could someone give me a few pointers? I read the short paragraph on the science page so I get the gist but I was wondering what some specific examples as they pertain to this project might look like.

    Posted

  • lrebull by lrebull scientist, translator, admin

    Let me see if I can do this tersely enough .. 😃

    SED=spectral energy distribution. So, it tells you where the energy is coming out from the combined light of {star+disk+anything else nearby including background sources OR galaxy} that is measured at the optical (SDSS, DSS), near-IR (2MASS), and mid-IR (WISE).

    Stars without disks will look something like what physicists call a blackbody. There is a mathematical description of this shape, but basically it describes the energy coming out from anything that is glowing due to heat - you, your toaster heating elements, an incandescent bulb, etc. Stars with disks have a little "extra" energy coming out in the IR - that is light from the star that is absorbed by the dust around it, which heats up and re-emits in the IR. That's part of why SEDs are so handy for looking at the Disk Detective objects. You get to see the emission from the images translated into relative energy, and once you look at a bunch of SEDs, you develop a calibrated eye for what works and what doesn't.

    Example of an SED from a plain star, star with big disk, and star with a ring of dust:
    http://www.spitzer.caltech.edu/images/2632-sig05-026-The-Invisible-Disk
    and another:
    http://www.spitzer.caltech.edu/images/1179-ssc2004-08c-Spectra-Show-Protoplanetary-Disk-Structures
    Example of an SED from a white dwarf with a relatively large excess:
    http://www.spitzer.caltech.edu/images/2054-sig09-002-Emission-from-the-White-Dwarf-System-GD-16
    Example of an SED from a star with a little excess:
    http://www.spitzer.caltech.edu/images/3282-ssc2010-07a-Spectral-Signatures-of-Planetary-Doom

    Hope that helps at least a little.

    Posted

  • geckzilla by geckzilla

    Yes! Just looking at a few examples makes them feel more familiar. I thought it might be a hard question; kind of like hoping to become a radiologist after looking at a couple of CT scans. Good thing these are just stars. I wonder how accurate Internet crowd-sourced radiology would be. Here, take this tutorial, now identify the stroke!

    Posted

  • jdebes by jdebes scientist, admin

    Ha! We didn't want to overwhelm people with SEDs, but if you get into it, feel free to tag interesting ones, especially any that look like the examples above.

    Posted