Image Credit & Copyright: NASA/ESA Hubble Space Telescope.
What a view we have here! This visually busy region of sky is known as the Antlia Dwarf Galaxy (ADG) and it’s over 4 million light years away in either the Antlia or Local group of galaxies (that’s still up in the air). This particular dwarf is just a handful of light years in diameter and has only about 1-3 million stars in it, of which we’re only seeing the brightest members. Compared to the 1-2 hundred billion stars in our 100,000 + light year diameter Milky Way, you can see why they call em dwarfs!
It’s believed that this dwarf galaxy and the nearby barred spiral galaxy NGC 3109 are gravitationally interacting because of the formation and disruption of the two objects as well as the fact that they are traveling in roughly the same direction at roughly the same velocity. If nothing else, it appears that the two have had a close encounter upwards of a billion years ago.
This is an interesting region because we have a vast collection (but not too vast) of stars ranging from ancient to young and stages in between. If you look this image over carefully, you will notice the telltale glint of stars in our own milky way in the image. Those stars are of course, between us and the dwarf galaxy. It’s kind of like looking through a screen door to see outside. Many views beyond the galaxy are obstructed with Milky Way stars in our line of sight but that doesn’t stop us from seeing beyond them. From an aesthetic viewpoint, it adds to the image in my opinion.
How about what’s beyond this object? The “wow” factor is alive and well there too as the backdrop that ADG is using to show itself off is a few handfuls of galaxies strewn across the image. Think about that for a moment; the first layer closest to us, is individual stars in the Milky Way; the second layer is a distant collection of a few million stars in a dwarf galaxy and the third layer are entire galaxies, each with roughly a hundred billion Sun’s and accompanying them, an untold sum of…..well, I’ll let you imagine the possibilities for yourself.
NAME: Antlia Dwarf Galaxy.
WHAT IS IT?: Dwarf Spheroidal Irregular Galaxy.
HOW FAR AWAY IS IT?: Roughly 4.3 million light years.
HOW BIG IS IT?: 2’x1.5’ arcminutes on the night sky.
HOW OLD IS IT?: More than 10 billion years old.
DISCOVERY: H. Corwin, Gerard de Vaucouleurs and A. de Vaucouleurs in 1985.
APPARENT MAGNITUDE? (Brightness from Earth): N/A: Too dim to be relevant but somewhere around 15.
WHERE IS IT? (General): Constellation Antlia (The Pump) and is thought to be a member of either the Antlia or Local Group of galaxies.
WHERE IS IT? (Exact RA/DEC J2000): RA 10h 04m 03.9s / DEC −27° 19′ 55″.
ESA Space Telescope page for this image: http://www.spacetelescope.org/images/potw1209a/