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

Mergers and Acquisitions

NGC 799 & NGC 800This pair of galaxies, NGC 799 (below) and NGC 800 (above), is located in the constellation of Cetus (The Whale) about 300 million light-years away. Our face-on point of view lets us see these objects are both spiral galaxies with characteristic long arms winding towards a bright bulge at the center.

It may appear that these spiral galaxies are coexisting in an everlasting peace, but that is unlikely. What we see is probably the calm before the storm. Typically, when two galaxies are close enough, they interact over hundreds of millions of years through mutual gravitational attraction. In some cases, only minor interactions occur, causing shape distortions, but sometimes galaxies collide, merging to form a single, new and larger galaxy.

We’ll have to check back in a few hundred million years.

Image Credit: ESO

A Large Galaxy and Its Satellite

NGC1232The colors of the different regions of NGC 1232 stand out in this picture—the central areas contain older reddish stars while the spiral arms are populated by younger blue stars and many star-forming regions. This galaxy is about 100 million light-years away and about twice the size of our Milky Way galaxy. Note the companion galaxy at the lower left, shaped like the squashed greek letter “theta”. NGC 1232A, the satellite galaxy of NGC 1232, is thought to be the cause of unusual bending in the spiral arms in its larger neighbor.

Image Credit: ESO

A Dark Place in the Sky

The Coalsack and the Southern CrossThe Coalsack is probably the most prominent the dark nebulae visible to the naked eye. It casts a dark silhouette against the Milky Way’s bright stripe of stars in the southern sky. The Coalsack is located roughly 600 light-years away in the southern part of the constellation of Crux (the Southern Cross).

This apparently starless dark patch is really an opaque cloud of interstellar dust blocking the light from the background stars. Dust grains in the cloud redden the starlight that reaches us by absorbing blue light preferentially, so that the red stars shimmering in the northern and darkest part of the Coalsack appear deeper red than they would in the absence of this dust.

Image Credit: ESO

Ptolemy’s Cluster

M7Messier 7 (aka M7 or  Ptolemy’s Cluster) is an open cluster of stars in the constellation of Scorpius. The cluster is visible to the naked eye, close to the “stinger” of Scorpius.

M7 has been known since antiquity; it was first recorded by the 1st-century Greek-Roman astronomer Ptolemy, who described it as a nebula in AD 130. Italian astronomer Giovanni Batista Hodierna observed it in the mid 17th-century and counted 30 stars in it. In 1764, French astronomer Charles Messier catalogued the cluster as the seventh member in his list of comet-like objects. This image was recently taken by the 2.2-metre ESO telescope in Chile.

Image Credit: ESO

A Young Star

HD 97300A newly formed star lights up the surrounding gas and dust clouds like a streetlight in enveloping fog, creating reflection nebula IC 2631. The glowing region is the reflection nebula known as IC 2631. These nebulae are clouds of cosmic dust that reflect light from a nearby star into space. IC 2631 is the brightest nebula in the Chamaeleon Complex, a large region of such clouds with numerous newborn and still-forming protostars. The complex is around 500 light-years away in the southern constellation of Chameleon. IC 2631 is illuminated by one of the youngest, most massive, and brightest stars in its region. This neighborhood is full of star-making material which form dark nebulae such as the dark areas above and below IC 2631 in this picture. Dark nebulae are so densely filled with gas and dust that they block background starlight.

HD 97300 a T Tauri star, the youngest visible stage for relatively small stars.They have not yet started to fuse hydrogen into helium in their cores like normal main sequence stars but are just starting to glow by generating heat from gravitational contraction. As these stars mature, they will lose mass and shrink, but during their T Tauri phase, these stars have not yet contracted to the more modest size that they will maintain for billions of years as main sequence stars. Because these young stars already have surface temperatures similar to their main sequence phase and because T Tauri-phase objects are essentially jumbo versions of their later selves, they appear brighter in their oversized youth than they will as mature main sequence stars.

Image Credit: ESO