Andromeda in UV


AndromedaGalex_900Andromeda Galaxy (aka M31) is just next door as large galaxies go, only about 2.5 million light-years. So close and spanning some 260,000 light-years, it took 11 images from the Galaxy Evolution Explorer (GALEX) satellite’s telescope to produce this portrait of the spiral galaxy in ultraviolet light. While its spiral arms stand out in visible light images, they look like rings in UV because the image is dominated by light from hot, young, massive stars. As sites of intense star formation, the rings have been interpreted as evidence Andromeda collided with its smaller neighboring elliptical galaxy M32 more than 200 million years ago.

Image Credit: NASA

Gamma Ray Raindrops


Five billion years ago, a great disturbance rocked a region near the monster black hole at the center of galaxy 3C 279. On 14 June, the burst of high-energy light produced by this event finally arrived at Earth, setting off detectors aboard the Fermi Gamma-ray Space Telescope and other satellites. This visualization shows gamma rays detected during 3C 279’s big flare by Fermi. Gamma rays are represented as expanding circles reminiscent of raindrops on water.The size of the circle and its color represent the energy of the gamma ray, with white lowest and magenta highest. The highest-energy gamma ray detected during this flare (52 billion electron volts) arrives near the end.

Video Credit: NASA

A Starbursting Galaxy


This is the dwarf galaxy known as NGC 1140. It lies 60 million light-years away in the constellation of Eridanus. It has an irregular form, much like the Large Magellanic Cloud, a small galaxy that orbits the Milky Way. This small galaxy is undergoing a starburst. Despite being only about one-tenth the size of the Milky Way, it is creating stars at about the same rate—the equivalent of one star the size of our sun being created per year. The galaxy is full of bright, blue-white, young stars.

Galaxies like NGC 1140 are of particular interest to astronomers because their composition makes them similar to the intensely star-forming galaxies in the early Universe, and those early Universe galaxies were the building blocks of present-day large galaxies like our Milky Way. Because they are so far away, the early Universe galaxies are harder to study, so these closer starbursting galaxies are a good substitute for studyingt galaxy evolution.

Its vigorous star formation eventually will have a very destructive effect on this small dwarf galaxy. When the larger stars in the galaxy die and explode as supernovae, the gas blown into space may escape the gravitational pull of the galaxy. The ejection of gas from the galaxy throws away one of the building blocks for future star formation. Thus, NGC 1140’s starburst cannot last for long.

Image Credit: ESA