A Gap in the Stars?

LDN 483Some of the stars appear to be missing, but the black gap in this starfield is not really a hole. It’s a region clogged with gas and dust. This dark cloud is called Lynds Dark Nebula 483 0r LDN 483. Clouds such as this are the birthplaces of future stars.

LDN 483 is about 700 light-years away in the constellation of Serpens (The Serpent). The cloud contains enough dusty material to completely block the visible light from background stars. Such a dense molecular cloud qualifies as a dark nebulae because of this obscuring property. One might think that the starless nature of a cloud like LDN 483 would suggest that it’s not a place where stars can take root and grow. The opposite is true: dark nebulae offer the most fertile environments for eventual star formation.

Studies of star formation in LDN 483 have discovered some of the youngest observable kinds of baby stars hidden in LDN 483. These gestating stars can be thought of as still being in the womb, having not yet been born as immature stars. In this first stage of stellar development, the star-to-be is just a clump of gas and dust contracting under the force of gravity within the surrounding molecular cloud. The protostar is still quite cool. At about -250°C they are colder than liquid oxygen on the Earth’s surface, and they “shine” only in long-wavelength submillimetrer light. Still, temperature and pressure are beginning to increase in the fledgling star’s core.

This earliest period of star growth lasts for a few thousands of years, an very short amount of time in astronomical terms.Stars typically live for millions or billions of years. Over the course of several million years, the protostar will grow warmer and denser. Its emission will increase, graduating from mainly cold, far-infrared light to near-infrared and finally to visible light. The once-dim protostar will have then become a fully luminous star.

As more and more stars emerge from LDN 483, the dark nebula will disperse and lose its opacity. Finally, the missing background stars that are currently hidden will then come into view, but they will be outshone by the bright young-born stars in the cloud.

Image Credit: ESO

Two Views of M83

This video fades between views of Messier 83 in visible light and infrared images captured at European Southern Observatory’s La Silla Observatory in Chile. The dust that obscures many stars becomes nearly transparent in the infrared image. That image may seem less dramatic, but it shows a swarm of new stars that are otherwise invisible.

Video Credit: ESO / M. Gieles
Acknowledgement: Mischa Schirmer

Mergers and Acquisitions

ngc2207Over next couple of billion years, these two spiral galaxies will end up in a complete galactic merger—the two galaxies will become a single, larger one. They’re about 150 million light-years away in the constellation of Canis Major (the Great Dog). The gravitational attraction of NGC 2207, the larger of the pair, is already stirring things up throughout its smaller partner, distorting IC 2163’s shape and throwing stars and gas into long streamers that extend over 100,000 light-years. However, most of the space between stars in a galaxy is empty. When these galaxies collide, almost none of the stars in them will crash into another star.

Image Credit: ESO

The Fuzz Around PDS 70c

The star PDS 70 is still in the process of planet formation, This image of the system taken by the Atacama Large Millimeter Array has attracted a lot of interest. It isn’t the large dust ring still undergoing planet formation that’s the main point of interest. It’s not the Jupiter-sized planet PDS 70c (just above 3 o’clock inside the ring) that’s already come together either. It’s the fuzzy dust cloud around that planet that intrigues astronomers. They believe it’s a region of moon formation. The planet may wind up with three of four large moons just like Jupiter’s.

Image Credit: ESO (ALMA) / NAO / NARO

A Nearby Cluster

FornaxClusterNamed for the southern constellation in whose part of the sky most of its galaxies can be found, the Fornax Cluster is one of the closest clusters of galaxies. At an average of 62 million light-years away, it is almost 20 times more distant than the nearby Andromeda Galaxy. Almost every yellow blob in this two-degree-wide image is an elliptical galaxy in the cluster. The barred spiral galaxy NGC 1365 that stands out in the lower right is a member of the cluster.

Image Credit: ESO

An Imperfect Spiral

Portrait of an Imperfect but Beautiful SpiralNot all spiral galaxies are picture-perfect. Messier 96 (aka NGC 3368) is a case in point: its core is off-center, its gas and dust are distributed asymmetrically, and its spiral arms are ill-defined. It’s still pretty.

Image Credit: ESO

A Ring Galaxy

A Cosmic Hit and RunThe odd galaxy next to the bright foreground star in this picture is the Vela ring galaxy, visible as a bright core surrounded by a blue halo. As the name suggests, this ring galaxy is located in the southern constellation of Vela (The Sails). It is notable for its compact core and large circular belt of gas and stars.

It is thought that a ring galaxy like this is created when a small galaxy passes through the center of a larger one, triggering a shock wave that spreads outward. That forces gas to the galaxy’s periphery where it begins to collapse and form new stars. The Vela ring galaxy is unusual in that it actually exhibits at least two rings, suggesting that its collision was not a recent one.

Image Credit: ESO

NCC 1365

NGC 1365NGC 1365 is enormous. It is one of the largest galaxies known to astronomers—over 200,000 light-years across. This, plus the sharply defined bar of old stars across its structure is why it is also known as the Great Barred Spiral Galaxy. Astronomers believe that the Milky Way, which is only half as big, may look very similar to this galaxy. The bright centre of the galaxy is thought to be caused by huge amounts of superhot gas ejected from the ring of material circling a central black hole. Young luminous hot stars, born in the interstellar clouds, give the arms their blue color. The bar and spiral pattern rotates, with one full turn taking about 350 million years. NGC 1365 is about 61 million light-years away in the constellation Fornax (the Furnace).

Image Credit: ESO