The rim of RCW 86

Image of part of a stellar remnant whose explosion was recorded in 185 AD. By studying this remnant in detail, a team of astronomers was able to solve the mystery of the Milky Way’s super-efficient particle accelerators. The team shows that the shock wave visible in this area is very efficient at accelerating particles and the energy used in this process matches the number of cosmic rays observed on Earth. North is toward the top right and east to the top left. The image is about 6 arc minutes across.

Image Credit: ESO/E. Helder & NASA/Chandra
Explanation from: https://www.eso.org/public/images/eso0923a/

The WLM Galaxy on the edge of the Local Group

This image, captured by ESO’s OmegaCAM on the VLT Survey Telescope, shows a lonely galaxy known as Wolf-Lundmark-Melotte, or WLM for short. Although considered part of our Local Group of dozens of galaxies, WLM stands alone at the group’s outer edges as one of its most remote members. In fact, the galaxy is so small and secluded that it may never have interacted with any other Local Group galaxy — or perhaps even any other galaxy in the history of the Universe.

Image Credit: ESO, VST/Omegacam Local Group Survey
Explanation from: http://www.eso.org/public/images/eso1610a/

H II Region N44 in the Large Magellanic Cloud

Southern part of the spectacular N44 H II region in the Large Magellanic Cloud. The green colour indicates areas that are particularly hot. The field measures 27.5 x 26.5 square arcminutes.

Image Credit: ESO

A star set to explode

Floating at the centre of this Hubble image is a lidless purple eye, staring back at us through space. This ethereal object, known officially as [SBW2007] 1 but sometimes nicknamed SBW1, is a nebula with a giant star at its centre. The star was originally twenty times more massive than our Sun, and is now encased in a swirling ring of purple gas, the remains of the distant era when it cast off its outer layers via violent pulsations and winds.

But the star is not just any star; scientists say that it is destined to go supernova! 26 years ago, another star with striking similarities went supernova — SN 1987A. Early Hubble images of SN 1987A show eerie similarities to SBW1. Both stars had identical rings of the same size and age, which were travelling at similar speeds; both were located in similar HII regions; and they had the same brightness. In this way SBW1 is a snapshot of SN1987a's appearance before it exploded, and unsurprisingly, astronomers love studying them together.

At a distance of more than 20 000 light-years it will be safe to watch when the supernova goes off. If we are very lucky it may happen in our own lifetimes...

Image Credit: ESA/Hubble, NASA, Nick Rose/Steve Byrne
Explanation from: https://www.spacetelescope.org/images/potw1401a/

Artist's Impression of the Exoplanet 55 Cancri e

This animated illustration shows one possible scenario for the hot, rocky exoplanet called 55 Cancri e, which is nearly two times as wide as Earth. New data from NASA's Spitzer Space Telescope show that the planet has extreme temperature swings from one side to the other-- and a possible reason for this might be the presence of lava pools.

This planet is tidally locked to its star, just as our moon is to Earth, which means that one side always sizzles under the heat of its star while the other side remains in the dark. If the planet were covered in lava, then the hot, sun-facing side of the planet would have liquid lava flows, while the colder, dark side would see solidified lava rock. The hardened lava would be unable to transport heat across the planet, explaining why Spitzer detected that the cold side of the planet is much colder than the hot side.

Such a lava planet, if it exists, would have dust streaming off of it, as illustrated here. Radiation and winds from the nearby star would blow off the material.

Scientists say that future observations with NASA's upcoming James Webb Space Telescope should provide more details about the nature of this exotic world.

Video Credit: NASA/JPL-Caltech
Explanation from: http://photojournal.jpl.nasa.gov/catalog/PIA20068

The Milky Way over the Temple of Poseidon

Temple of Poseidon, Cape Sounion, Greece

May 2015

Image Credit & Copyright: Alexandros Maragos

Orion

A phenomenal view of the huge expanse of the Orion complex, made up of 34 panes comprising over 400 hours of exposure. The red emission nebula Barnard’s Loop stretches -approximately 300 lightyears in length - across the vastness captured here, arcing around the famed Orion and Horsehead nebulae.

Image Credit & Copyright: Tom O'Donoghue and Olly Penrice
Explanation by: Royal Observatory Greenwich

Colour image of galaxy cluster MACS J0416.1–2403

This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster MCS J0416.1–2403. This is one of six being studied by the Hubble Frontier Fields programme. This programme seeks to analyse the mass distribution in these huge clusters and to use the gravitational lensing effect of these clusters, to peer even deeper into the distant Universe.

A team of researchers used almost 200 images of distant galaxies, whose light has been bent and magnified by this huge cluster, combined with the depth of Hubble data to measure the total mass of this cluster more precisely than ever before.

Image Credit: ESA/Hubble, NASA, HST Frontier Fields
Explanation from: https://www.spacetelescope.org/images/heic1416a/

Around the star-formation region Gum 19 (RCW 34)

This image shows the area around the star-forming region Gum 19 (also known as RCW 34), in the direction of the constellation of Vela (The Sails), as seen by the Digitized Sky Survey 2. The image covers an area of 3 by 3 degrees on the sky.

Image Credit: NASA/JPL-Caltech
Explanation from: http://www.eso.org/public/images/eso1014b/

The star formation region Messier 17

This image of the rose-coloured star forming region Messier 17 was captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. It is one of the sharpest images showing the entire nebula and not only reveals its full size but also retains fine detail throughout the cosmic landscape of gas clouds, dust and newborn stars.

Image Credit: ESO
Explanation from: https://www.eso.org/public/images/eso1537a/

Globular Cluster Messier 22

This image shows the centre of the globular cluster Messier 22, also known as M22, as observed by the NASA/ESA Hubble Space Telescope. Globular clusters are spherical collections of densely packed stars, relics of the early years of the Universe, with ages of typically 12 to 13 billion years. This is very old considering that the Universe is only 13.8 billion years old.

Messier 22 is one of about 150 globular clusters in the Milky Way and at just 10 000 light-years away it is also one of the closest to Earth. It was discovered in 1665 by Abraham Ihle, making it one of the first globulars ever to be discovered. This is not so surprising as it is one of the brightest globular clusters visible from the northern hemisphere, located in the constellation of Sagittarius, close to the Galactic Bulge — the dense mass of stars at the centre of the Milky Way.

The cluster has a diameter of about 70 light-years and, when looking from Earth, appears to take up a patch of sky the size of the full Moon. Despite its relative proximity to us, the light from the stars in the cluster is not as bright as it should be as it is dimmed by dust and gas located between us and the cluster.

As they are leftovers from the early Universe, globular clusters are popular study objects for astronomers. M22 in particular has fascinating additional features: six planet-sized objects that are not orbiting a star have been detected in the cluster, it seems to host two black holes, and the cluster is one of only three ever found to host a planetary nebula — a short-lived gaseous shells ejected by massive stars at the ends of their lives.

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1514a/

Moon, Venus, Jupiter and Moons

On June 30, 2015, Venus and Jupiter were close in western skies at dusk. Near the culmination of this year's gorgeous conjunction, the two bright evening planets are captured in the same telescopic field of view in this image taken after sunset from Bejing, China. As the two bright planets set together in the west, a nearly Full Moon rose above the horizon to the south and east. Imaged that night with the same telescope and camera, the rising Moon from the opposite part of the sky is compared with the planetary conjunction for scale in the digitally composited image. The full lunar disk covers an angle of about 1/2 degree on the sky. Visible as well in binoculars and small telescopes are Venus' crescent and Jupiter's four Galilean moons.

Image Credit & Copyright: Wang, Letian
Explanation from: http://apod.nasa.gov/apod/ap150702.html

Artist's Impression of the Quasar 3C 279

This is an artist’s impression of the quasar 3C 279. Astronomers connected the Atacama Pathfinder Experiment (APEX), in Chile, to the Submillimeter Array (SMA) in Hawaii, USA, and the Submillimeter Telescope (SMT) in Arizona, USA for the first time, to make the sharpest observations ever, of the centre of a distant galaxy, the bright quasar 3C 279. Quasars are the very bright centres of distant galaxies that are powered by supermassive black holes. This quasar contains a black hole with a mass about one billion times that of the Sun, and is so far from Earth that its light has taken more than 5 billion years to reach us. The team were able to probe scales of less than a light-year across the quasar — a remarkable achievement for a target that is billions of light-years away.

Image Credit: ESO/M. Kornmesser
Explanation from: https://www.eso.org/public/images/eso1229a/

Wide-field view of the Lagoon Nebula

This spectacular image shows the very rich region of sky around the Lagoon Nebula (Messier 8). The Lagoon appears at the centre, the Trifid Nebula (Messier 20) close to the top. Other nebulae, both bright and dark, can be seen elsewhere in the picture as well as several star clusters. This view was created from pictures forming parts of the Digitized Sky Survey 2.

Image Credit: ESO/Digitized Sky Survey 2, Davide De Martin
Explanation from: http://www.eso.org/public/images/eso1403c/

Comet PanSTARRS and the Moon

July 2015

Image Credit & Copyright: Yuri Beletsky

The Orion Nebula

This image of the Orion Nebula was captured using the Wide Field Imager camera on the MPG/ESO 2.2-metre telescope at the La Silla Observatory, Chile. This image is a composite of several exposures taken through a total of five different filters. Light that passed through a red filter, as well as light from a filter that shows the glowing hydrogen gas, is coloured red. Light in the yellow–green part of the spectrum is coloured green, blue light is coloured blue and light that passed through an ultraviolet filter has been coloured purple. The exposure times were about 52 minutes through each filter.

Image Credit: ESO/Igor Chekalin
Explanation from: https://www.eso.org/public/images/eso1103a/

Center of the Milky Way Galaxy in Near-Infrared

Although best known for its visible-light images, the Hubble Space Telescope also observes over a limited range of infrared light. The galactic center is marked by the bright patch in the lower right. Along the left side are large arcs of warm gas that have been heated by clusters of bright massive stars. In addition, Hubble uncovered many more massive stars across the region. Winds and radiation from these stars create the complex structures seen in the gas throughout the image. This sweeping panorama is the sharpest infrared picture ever made of the galactic center region.

Image Credit: NASA/ESA/STScI/D.Wang et al.
Explanation from: http://chandra.si.edu/photo/2009/galactic/more.html

ALMA telescope

Centre-stage in this image is one of the array of dishes that make up the ALMA telescope. In the background are some of its 65 fellow telescopes, operating together to produce some of the sharpest astronomical images imaginable using light at millimetre and submillimeter wavelengths. This photograph was taken by one of a team of crack photographers — the Fulldome Expedition — who are visiting ESO's observatories in Chile to obtain spectacular images for use in planetarium presentations

Image Credit: B. Tafreshi/ESO
Explanation from: http://www.eso.org/public/images/_nik2781-cc/

Bright Galaxy Centaurus A

Centaurus A is the fifth brightest galaxy in the sky -- making it an ideal target for amateur astronomers -- and is famous for the dust lane across its middle and a giant jet blasting away from the supermassive black hole at its center. Cen A is an active galaxy about 12 million light years from Earth.

This image is part of a "quartet of galaxies" collaboration of professional and amateur astronomers that combines optical data from amateur telescopes with data from the archives of NASA missions. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls Chandra's science and flight operations.

Image Credit: X-ray: NASA/CXC/SAO; Optical: Rolf Olsen; Infrared: NASA/JPL-Caltech
Explanation from: http://www.nasa.gov/mission_pages/chandra/multimedia/galaxy-centaurusA.html

A snowstorm of distant galaxies

At first glance, the scatter of pale dots on this NASA/ESA Hubble Space Telescope image looks like a snowstorm in the night sky. But almost every one of these delicate snowflakes is a distant galaxy in the cluster MACS J0717.5+3745 and each is home to billions of stars. This apparently placid scene also hides a storm of epic scale. This picture shows a region where three galaxy clusters are merging and releasing enormous amounts of energy in the form of X-rays. These distant objects are around 5.4 billion light-years from Earth, and were imaged during the Massive Cluster Survey, a project to study distant clusters of galaxies using Hubble.

The amount of mass in this sea of galaxies is huge, and is great enough to visibly bend the fabric of spacetime. The strange distortion in the shapes of many of the galaxies in this picture, which appear stretched and bent as if they were looked at through a glass bottle, is a result of gravitational lensing, where the gravitational fields around massive objects bend light around them.

Predicted by Einstein in his famous general theory of relativity, gravity’s ability to distort light was first demonstrated in 1919 in a well-known experiment carried out by Sir Arthur Eddington, who led an expedition to the island of Principe, off the coast of Africa, to measure the apparent shift of a star when observed close to the edge of the Sun’s disc during a solar eclipse.

This picture was created from images taken through near-infrared (F814W) and yellow (F555W) filters using the Wide Field Channel of Hubble’s Advanced Camera for Surveys. The exposure times were about 67 minutes and 33 minutes respectively and the field of view of the image is about 3 arcminutes across.

Image Credit: ESA/Hubble, NASA and H. Ebeling
Explanation from: https://www.spacetelescope.org/images/potw1017a/