Galaxy Zoo Talk

Missing star

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    While finding out more about this galaxy in SDSS i noticed this green star, which is not visible in DECaLS. I thought DECaLS has a better resolution than SDSS, any thoughts on this one? (No SN reference)

    SDSS star

    Posted

  • Budgieye by Budgieye moderator

    I'm not sure why the green object is not in DECaLS.

    DECaLS and SDSS http://skyserver.sdss.org/dr9/en/tools/explore/obj.asp?ra=246.41624601424928&dec=21.402967170292513

    enter image description here

    http://skyserver.sdss.org/dr9/en/tools/explore/obj.asp?id=1237662224628385447

    Green in SDSS is yellow to our eyes.

    Most probably, the software for DECaLS saw this green spot, and removed it, thinking that it was a cosmic ray hit.

    Possible yellow star, some cataclymic variable stars are a very green - yellow.

    Possible "pea", an extreme starforming galaxy. Place this object in The Green Pea Galaxies by RickN http://talk.galaxyzoo.org/#/boards/BGZ0000001/discussions/DGZ0000zvt The thread in Talk for discussions about peas

    just in case it is real.

    Supernova are often greenish-blue, but this star doesn't seem to be in a galaxy. A supernova in our own galaxy would be much brighter.

    Variable stars or nova would have a small star in the same place, I would think.

    Possible that it is a green quasar. Quasars half way across the universe are green. Some of the iron containing ones which are closer are a green colour.

    not in dr7

    Unless there is a spectrum, there is no way to tell.

    REading

    Re: Zooite Guide to Spectra Part 7 A spectral analysis of 6 round green things http://www.galaxyzooforum.org/index.php?topic=274815.msg300406#msg300406

    PAGE 2 Galaxy Redshift Chart http://talk.galaxyzoo.org/#/boards/BGZ0000007/discussions/DGZ0000ulp?page=2

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    Yes too bad there is no spectrum, would be so much easier..

    Although it isn't visible in DR7 and back, it's presented as photometric object in all Data Releases, and funnily pops up again in DR3 😃 (and DR12)

    enter image description here
    DR3

    SDSS DR3 Star

    So best guess is indeed a CV star. No reference on CV Catalogue for RA16:25:39.86 Dec+21:24:10.04

    http://archive.stsci.edu/prepds/cvcat/Forms/varcat_query.html

    but since this catalogue was frozen as of 1 February 2006 (wiki) it certainly isn't complete

    Posted

  • c_cld by c_cld

    This object http://cas.sdss.org/dr3/en/tools/explore/obj.asp?id=588017978380191296 is a square cosmic ray hit which appears only in r band.

    588017978380191296

    It has been imaged on

    run rerun camcol field

    3900 41 3 741

    Its location was further imaged on

    run camcol field

    4014 6 0269

    4520 6 0067

    without any "star" in this 12"x12" area 😃

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR

    So this explains why it appears and disappears in the different data releases (only visible in DR3, DR9 and DR12).

    And the only way to tell in which bands an 'object' like this does or doesn't appear is by using / comparing the different FITS files?

    Thanks for the clarification

    Posted

  • CeciliaB by CeciliaB

    The simplest way to find out would, I suppose, have been to just zoom out on SDSS. Then one would have seen that the object was square snd subsequently not a star.

    Posted

  • Ghost_Sheep_SWR by Ghost_Sheep_SWR in response to CeciliaB's comment.

    Possibly, but real objects are often also pixelated, which makes it difficult to discern the two.

    Take for comparison the same picture from DR12 (equal to DR9); it has some square features but not as obvious as the DR3 image, so might be caused by bad resolution.

    enter image description here DR12 image

    I also try to gather as much information before posting anything, which turned out to be a photometric object in all SDSS Data Releases.

    Ah well learned something more today, just unsure how one can find the further imaging of locations in SDSS (run camcol field) mentioned in the post from c_cld

    Posted