The Crab Nebula

In 1054 AD, during the Song dynasty, Chinese astronomers spotted a bright new star in the night sky. This newcomer turned out to be a violent explosion within the Milky Way, caused by the spectacular death of a star some 1600 light-years away. This explosion created one of the most well-studied and beautiful objects in the night sky — the Crab Nebula.

The beautiful result of this cataclysmic Type II supernova is shown here, imaged by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys. Unlike more commonly seen views of this remnant (heic0515), which show incredibly intricate branches and spires laced throughout the region, this image uses just a single filter, giving rise to a smoother and far simpler view of the famous nebula.

The unstoppable collapse of the Crab’s progenitor star led to the formation of a rapidly rotating neutron star named the Crab Pulsar, which lurks at the heart of the nebula. This object is roughly the same size as Mars’ small moon Phobos, but contains almost one and a half times the mass of the Sun, and whirls around thirty times every second. This causes jets of high-energy radiation to periodically sweep in the direction of Earth, like the spinning beams of a lighthouse, causing the Crab Nebula to appear to pulse at specific wavelengths.

The Crab Nebula is also known as NGC 1952 and Messier 1. The second of these names was assigned by Charles Messier. He initially misclassified the nebula with Halley’s Comet but soon he realised that the object did not move. Hence he decided to call it M1 as the first object of a catalogue of objects that look like comets but are not.

Image Credit: ESA/Hubble & NASA, Judy Schmidt
Explanation from: https://www.spacetelescope.org/images/potw1644a/

Milky Way Galaxy seen from the International Space Station

ISS, Orbit of the Earth

September 2016

Image Credit: NASA/ESA

Aurora, Milky Way Galaxy, Large Magellanic Cloud Galaxy and Small Magellanic Cloud Galaxy seen over Australia

Contos Beach, Margaret River, Western Australia, Australia

March 17, 2013

Image Credit & Copyright: Colin Legg

Aurora over Canada

Yukon, Canada

Image Credit & Copyright: Marc Adamus

ESO’s VLT Detects Unexpected Giant Glowing Halos around Distant Quasars

An international team of astronomers has discovered glowing gas clouds surrounding distant quasars. This new survey by the MUSE instrument on ESO’s Very Large Telescope indicates that halos around quasars are far more common than expected. The properties of the halos in this surprising find are also in striking disagreement with currently accepted theories of galaxy formation in the early Universe.

An international collaboration of astronomers, led by a group at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, has used the unrivalled observing power of MUSE on the Very Large Telescope (VLT) at ESO’s Paranal Observatory to study gas around distant active galaxies, less than two billion years after the Big Bang. These active galaxies, called quasars, contain supermassive black holes in their centres, which consume stars, gas, and other material at an extremely high rate. This, in turn, causes the galaxy centre to emit huge amounts of radiation, making quasars the most luminous and active objects in the Universe.

The study involved 19 quasars, selected from among the brightest that are observable with MUSE. Previous studies have shown that around 10% of all quasars examined were surrounded by halos, made from gas known as the intergalactic medium. These halos extend up to 300 000 light-years away from the centres of the quasars. This new study, however, has thrown up a surprise, with the detection of large halos around all 19 quasars observed — far more than the two halos that were expected statistically. The team suspects this is due to the vast increase in the observing power of MUSE over previous similar instruments, but further observations are needed to determine whether this is the case.

“It is still too early to say if this is due to our new observational technique or if there is something peculiar about the quasars in our sample. So there is still a lot to learn; we are just at the beginning of a new era of discoveries”, says lead author Elena Borisova, from the ETH Zurich.

The original goal of the study was to analyse the gaseous components of the Universe on the largest scales; a structure sometimes referred to as the cosmic web, in which quasars form bright nodes. The gaseous components of this web are normally extremely difficult to detect, so the illuminated halos of gas surrounding the quasars deliver an almost unique opportunity to study the gas within this large-scale cosmic structure.

The 19 newly-detected halos also revealed another surprise: they consist of relatively cold intergalactic gas — approximately 10 000 degrees Celsius. This revelation is in strong disagreement with currently accepted models of the structure and formation of galaxies, which suggest that gas in such close proximity to galaxies should have temperatures upwards of a million degrees.

The discovery shows the potential of MUSE for observing this type of object. Co-author Sebastiano Cantalupo is very excited about the new instrument and the opportunities it provides: “We have exploited the unique capabilities of MUSE in this study, which will pave the way for future surveys. Combined with a new generation of theoretical and numerical models, this approach will continue to provide a new window on cosmic structure formation and galaxy evolution.”

Image Credit: ESO/Borisova et al.
Explanation from: https://www.eso.org/public/news/eso1638/

Sun's reflection on Solar Arrays of the International Space Station

ISS, Orbit of the Earth

September 2016

Image Credit: NASA/ESA

Moon and Earth's Atmosphere seen from the International Space Station

ISS, Orbit of the Earth

September 2016

Image Credit: NASA/ESA

Tornado near Wray in Colorado

Wray, Colorado, USA

Image Credit & Copyright: Tim Moxon

Lightning over Western Australia

Fremantle, Western Australia, Australia

January 29, 2015

Image Credit & Copyright: Graham Newman

Comet Lovejoy

Comet Lovejoy soars through the night sky in a green haze with an ion tail in its wake. The image shows Lovejoy appearing to lose its tail on 21 January 2015.

Image Credit & Copyright: Michael Jäeger
Explanation by: Royal Observatory Greenwich

Lightning Strikes over Africa seen from the International Space Station

ISS, Orbit of the Earth

September 2016

Image Credit: NASA/ESA

Puyehue-Cordón Caulle Volcano Eruption

Puyehue-Cordón Caulle, Chile

2011

Image Credit: Ian Salas