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

NGC 6153

A nitrogen-rich nebula This is NGC 6153. The faint blue haze is what remains of a star like the sun after it had depleted most of its fuel. When that happened, the outer layers of the star were ejected and then ionized by the ultraviolet light from hot core of the star, forming the nebula.

NGC 6153 is a planetary nebula which contains large amounts of neon, argon, oxygen, carbon and chlorine—up to three times more than can be found in our solar system. It contains five times more nitrogen than our sun! It could be that the star developed higher levels of these elements as it grew and evolved, but it is more likely that the star originally formed from a cloud of material that already contained an abundance of those elements.

Image Credit: ESA / NASA

The SDP.81 Einstein Ring

SDP_81 Einstein RingESO’s ALMA long baseline array has produced a marvelously detailed image of a distant galaxy being gravitationally lensed. The new image shows star-forming regions, the likes of which have never been seen before in such detail in a galaxy so remote. The new observations are far more detailed than any previously made of such a distant galaxy, including those made using the Hubble Space Telescope, and reveal clumps of star formation in the galaxy equivalent to giant versions of the  Orion Nebula.

The left panel shows the foreground lensing galaxy as seen via Hubble and the gravitationally lensed galaxy SDP.81. The lensed galaxy forms an almost perfect Einstein Ring but is barely visible.

The center image shows the sharp ALMA image of the Einstein ring. The foreground lensing galaxy being invisible to ALMA.

On the right, the reconstructed image of the distant galaxy created using sophisticated models of the magnifying gravitational lens reveals fine structures within the ring: several dust clouds within the galaxy thought to be giant cold molecular clouds, the birthplaces of stars and planets.

Image Credits: ALMA (NRAO / ESO / NAOJ)
Y. Tamura (The University of Tokyo)
Mark Swinbank (Durham University)

On the Edge of the Local Void

0105-4x5color.aiMost galaxies are clumped together in groups or clusters, but NGC 6503 is in a lonely position at the edge of a strangely empty patch of space called the Local Void. The Local Void is a region of space over 150 million light-years across that is essentially empty of stars or galaxies. NGC 6503 is 18 million light-years away from us in the constellation Draco. It’s about 30,000 light-years or a third of the size of the Milky Way.

Image Credit: NASA / ESA