36x300s
91x120s
This is the 2nd dwarf galaxy that I shot. See my picture of Leo I here:
https://www.astrobin.com/jhr0sw/Oh, what a drama for this dwarf. All pictures were massively affected by streaks of stray light and it took me quite a while to figure out what has happened. While I first suspected stray light from the LED of my EQ6R that somehow reached the sensor, I'm now confident that the stray light came from the 2.55m bright star Zosma (delta Leo) which is more than one 1° away from the edge of the picture. I'm glad that the GraXpert software could rescue this and removed the hefty gradient. It took a lot of time to work through this and I had to cut off the dark parts of the histrogram.
Leo2 is a spheroidal dwarf galaxy in the constellation of Leo. Like Leo 1 it has only been detected in the year 1950.
It's ~690000 lightyears away and has a mass of only ~27 million solar masses and a diameter of ~4200ly. It has a low metallicity of [Fe]/[H]=-1.9, i.e. a factor of 80 less iron than the sun. This indicates that Leo II consists of old stars.
The paper
https://iopscience.iop.org/article/10.1086/519955/pdf says:
"Leo II first began forming stars throughout the whole galaxy with a constant (inefficient) star formation rate. (b) The star formation then began to cease in the outskirts, and the star-forming region gradually shrank toward the center. (c) The star-forming activity dropped to ?0 by ?4 Gyr ago except at the center, where a small population younger than 4 Gyr is found." Dwarf galaxies challenge more current theories. For example it is not explained yet why we only find so few dwarf galaxies while cosmological simulations predict way more (
https://en.wikipedia.org/wiki/Dwarf_galaxy_problem). (However, more and more dwarf galaxies and dwarf galaxy candidates are found.)
There are more problems:
Cusp/Core problem
https://en.wikipedia.org/wiki/Cuspy_halo_problemToo-Big-To-Fail problem (
https://arxiv.org/abs/1111.2048)
Planes-of-satellites problem (the mystery that observations have suggested that the Milky Way and Andromeda each have satellite galaxies generally within a plane, and each such plane is not the plane of the host galaxy, but tilted in relation to it which is unexpected when satellites are indeed formed together with the host galaxy).
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