A Cluster of Galaxies

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

Sharpless 2-274

ESO’s Very Large Telescope images the Medusa NebulaESO’s Very Large Telescope in Chile captured this image of the Medusa Nebula (also known Abell 21 and Sharpless 2-274). As the star at the heart of this nebula made its final transition into the final stage of its existence, it blew off its outer layers into space, forming this colorful cloud. The Sun will go through a similar process in a few billion years.

Image Credit: ESO

Climate Change on Neptune

These thermal images taken from Neptune were taken with the VISIR instrument on ESO’s Very Large Telescope. Taken between 2006 and 2021, they show Neptune gradually cooling down, followed by a dramatic heating of its south pole in the last few years. From 2003 to 2018 Neptune’s average temperature dropped about 8 °C, and over the next three years it spiked 11 °C hotter.

Video Credit: ESO

A Herbig-Haro Object

HH 46:47This picture was assembled from combined observations from NASA’s Spitzer Space Telescope and ESO’s Atacama Large Millimeter/submillimeter Array (ALMA) in Chile. It reveals the throes of stellar birth in an object known as HH 46/47.

HH or Herbig-Haro objects form when particle jets shot out by newborn stars collide with surrounding matter, producing small, bright, nebulous regions. The dynamics within many HH objects are obscured from observation with visible light by the enveloping gas and dust, but the infrared and submillimeter light seen by Spitzer and ALMA, respectively, cuts through the cloud around HH 46/47. (Infrared light has longer wavelengths than what we see with our eyes, and submillimeter wavelengths are longer still.)

In this false-color image the shorter-wavelength light appears blue and longer-wavelength light, red. Blue shows gas energized by the outflowing jets. Green traces a combination of hydrogen gas molecules and dust that follows the boundary of the gas cloud surrounding the young star. The red areas are excited carbon monoxide gas.

Image Credit: NASA / ESO

A Barred Spiral Galaxy

An Often Ignored BeautyThis is the spiral galaxy NGC 986 in the constellation of Fornax (The Furnace). The galaxy is about 56 million light-years away, and we see it almost perfectly face-on from Earth, allowing us to see the two main spiral arms and also a central bar-shaped structure, composed of stars and dust, which makes it a barred spiral galaxy.

Image Credit: ESO

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