Question
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suelaine
What is the cloud and can anyone tell how old this galaxy is? #unusual
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JeanTate
It would seem to be a nearby, dwarf galaxy, with some recent star-formation. And a background ETG (early-type galaxy; elliptical or lenticular). While the gas in the dwarf is likely as old as the universe, the stars (that we see) are young, possibly only ~100 million years old (or perhaps younger). Someone who has done a detailed analysis of the spectrum could tell you what range of ages is consistent with the spectrum; in any case, if there's a population of older, redder stars, it may not show up even in the spectrum (so perhaps much of the mass of this dwarf galaxy has been there since forever!)
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fatha731
in response to JeanTate's comment.
I agree with you about the dwarf galaxy, but is my assumption about the blue irregular one correct?
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JeanTate
in response to fatha731's comment.
It's certainly blue. If you consider it to be, morphologically, irregular, then that's what it is.
I'm not very familiar with dwarf galaxies, but I vaguely recall that many, perhaps most, are irregular. From memory, there are dE (dwarf ellipticals) and dSph (dwarf spheroidals - I don't know what they are), and dIrr (dwarf irregulars) (there are also compact dwarfs, but in SDSS images they would be indistinguishable from stars, or globular clusters associated with galaxies other than those in the Local Group)
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