Spiral galaxy outlined with bright stars and dark dust. Today’s Image of the Day from the European Space Agency features a spiral galaxy known as NGC 2775, located 67 million light-years away in the constellation of Cancer.
According to the ESA, the central part of the galaxy is dominated by “an unusually large and relatively empty galactic bulge.”
The feathered spiral arms of NGC 2775 are highlighted by millions of young blue stars as they intersect with dark regions of dust. A galaxy is a gravitationally bound system of stars, stellar remnants, interstellar gas, dust, and dark matter. The word galaxy is derived from the Greek galaxias (γαλαξίας), literally “milky”, a reference to the Milky Way. Galaxies range in size from dwarfs with just a few hundred million (10) stars to giants with one hundred trillion (10) stars, each orbiting its galaxy’s center of mass.
Research released in 2016 revised the number of galaxies in the observable universe from a previous estimate of 200 billion (2×1011) to a suggested two trillion (2×1012) or more and, overall, as many as an estimated 1×1024 stars (more stars than all the grains of sand on planet Earth). Most of the galaxies are 1,000 to 100,000 parsecs in diameter (approximately 3,000 to 300,000 light years) and separated by distances on the order of millions of parsecs (or megaparsecs). For comparison, the Milky Way has a diameter of at least 30,000 parsecs (100,000 ly) and is separated from the Andromeda Galaxy, its nearest large neighbor, by 780,000 parsecs (2.5 million ly.)
Image Credit: ESA