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Eye On The Sky: the top astro images of 2017

The top astro images released in 2017, as picked by BBC Sky at Night Magazine.

Although it looks like the pattern of a shell on the beach, this intriguing spiral is in fact astronomical in nature. The Atacama Large Millimeter/submillimeter Array (ALMA) captured this remarkable image of a binary star system, where two stars — LL Pegasi and its companion — are locked in a stellar waltz, orbiting around their common centre of gravity. The old star LL Pegasi is continuously losing gaseous material as it evolves into a planetary nebula, and the distinct spiral shape is the imprint made by the stars orbiting in this gas. The spiral spans light-years and winds around with extraordinary regularity. Based on the expansion rate of the spiralling gas, astronomers estimate that a new “layer” appears every 800 years — approximately the same time it takes for the two stars to complete one orbit around each other. LL Pegasi was first highlighted about 10 years ago when the NASA/ESA Hubble Space Telescope obtained a picture of the almost-perfect spiral structure. This was the first time a spiral pattern had been found in material surrounding an old star. Now, ALMA’s observations, of which this image only shows one “cross-section”, have added an extra dimension to reveal the exquisitely-ordered 3D geometry of the spiral pattern. A full view of the 3D video can be seen in this video. An additional image shows a composition of the ALMA and Hubble data. Links: ALMA and Hubble observe LL Pegasi 3D view of LL Pegasi

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Each month in BBC Sky at Night Magazine we present our favourite images captured by the world’s biggest and most hardworking telescopes for our Eye On The Sky image gallery.

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Here we present a month-by-month selection of the most amazing astrophotos that made our monthly galleries in 2017.

Launch Gallery
01 - Galaxy NGC 1398
A new vista of Orion

ESO VISTA telescope, 4 January 2017
The Orion A molecular cloud is a massive star-forming region about 1,350 lightyears away, making it the closest stellar factory to our planet. This image is the most detailed near-infrared image of the region ever taken. It shows the entirety of Orion A, which stretches for about 8° south of the ‘sword’ of the Orion constellation. The region is an incredibly active region with ongoing star formation being triggered by the death of previous generations of stars. This happens when older stars end their lives in an explosion, causing nearby molecular clouds to collapse and bringing about the formation of new stars to replace them. VISTA’s infrared capabilities mean it can see beyond the dust that would otherwise obscure optical observations, revealing young, hidden stars to astronomers on Earth. Credit: ESO/VISION survey
02 - Cats Paw Lobster
Cat and CrustaceanESO VLT Survey Telescope, 1 February 2017

Just like clouds in the sky over Earth, the cosmic clouds we call nebulae form such intricate, unique shapes that observers cannot help but spot familiar objects in them. The nebula in the top right of this image is NGC 6334, known as the Cat’s Paw Nebula as it forms a trio of clouds that look rather like a feline footprint. Bottom left is NGC 6357, known as the Lobster Nebula with its dusty tendrils reaching out to the edge of the image.

That these two nebulae appear so close together, as though the ‘cat’ were waiting to pounce on its unsuspecting prey, is actually an illusion. In reality the Cat’s Paw is about 5,500 lightyears away from Earth, while the Lobster is 8,000 lightyears away.

Credit: ESO
Although it looks like the pattern of a shell on the beach, this intriguing spiral is in fact astronomical in nature. The Atacama Large Millimeter/submillimeter Array (ALMA) captured this remarkable image of a binary star system, where two stars — LL Pegasi and its companion — are locked in a stellar waltz, orbiting around their common centre of gravity. The old star LL Pegasi is continuously losing gaseous material as it evolves into a planetary nebula, and the distinct spiral shape is the imprint made by the stars orbiting in this gas. The spiral spans light-years and winds around with extraordinary regularity. Based on the expansion rate of the spiralling gas, astronomers estimate that a new “layer” appears every 800 years — approximately the same time it takes for the two stars to complete one orbit around each other. LL Pegasi was first highlighted about 10 years ago when the NASA/ESA Hubble Space Telescope obtained a picture of the almost-perfect spiral structure. This was the first time a spiral pattern had been found in material surrounding an old star. Now, ALMA’s observations, of which this image only shows one “cross-section”, have added an extra dimension to reveal the exquisitely-ordered 3D geometry of the spiral pattern. A full view of the 3D video can be seen in this video. An additional image shows a composition of the ALMA and Hubble data. Links: ALMA and Hubble observe LL Pegasi 3D view of LL Pegasi
Stellar SpiralAtacama Large Millimeter/submillimeter Array, 6 March 2017

From a tiny seashell found on the beach to our own Milky Way, spirals are a common feature in nature. This one is caused by two stars orbiting each other in binary system LL Pegasi. One older star is ejecting gas and dust as it approaches the end of its life, and the spiral shape is carved out as the stars twirl around each other in orbit.

Credit: ALMA (ESO/NAOJ/NRAO)/H. Kim et al.
04 - solar flare
Solar Flares

NASA Solar Dynamics Observatory, 11 April 2017

An active region produced several medium sized solar flares over a ten-hour period on 3 April 2017. These were the strongest flares of the year so far. Some coronal mass ejections were also associated with some of these flares, ejecting plasma into space.

NASA’s Solar Dynamics Observatory was able to capture images of the flares in a wavelength of extreme ultraviolet light

Credit: NASA/GSFC/Solar Dynamics Observatory
05 - Perseus Galaxy Cluster
Close encounters of the galactic kind

Chandra X-ray Observatory, 2 May 2017

The Perseus Galaxy Cluster resides in the Perseus constellation about 240 million lightyears away, and is so huge it would take light about 11 million years to cross it.

At roughly the 7 o’clock position in this image is a curved wave blowing across the cluster, spanning about 200,000 lightyears; roughly twice the size of the Milky Way.

The wave was probably formed billions of years ago as a result of a close encounter between the galaxy cluster and a smaller counterpart.

Credit: NASA/CXC/GSFC/S.A.Walker, et al.
06 - SOHOs solstice
SOHO’s solstice

Solar & Heliospheric Observatory, 21 June 2017

While we on Earth’s northern hemisphere experienced the summer solstice as the longest day of the year, the SOHO space observatory was busy observing the Sun at different ultraviolet wavelengths to produce this image.

From left to right, the brightest parts of the Sun in each image are 60,000–80,000ºC, 1 million, 1.5 million and 2 million respectively.

Credit: SOHO (ESA & NASA)
Phobos orbiting Mars, as seen by the Hubble Space Telescope. Credit: NASA, ESA, and Z. Levay (STScI)
Phobos Photobomb

Hubble Space Telescope, 20 July 2017

Astronomers were capturing images of Mars when they happened to spot the moon Phobos appearing from behind the Red Planet. 13 separate images taken over 22 minutes reveal the moon’s motion as it orbits Mars, which it does so once every 7 hours and 39 minutes.

Phobos is edging closer to Mars with each orbit, and it is predicted that in 30-50 million years it may eventually smash into the planet.

Credit: NASA, ESA, and Z. Levay (STScI)
Acknowledgment: J. Bell (ASU) and M. Wolff (Space Science Institute)
08 - ic10
Starburst

Chandra X-ray Observatory, 10 August 2017

Chandra observations of IC 10,a starburst galaxy, revealed about 110 X-ray sources. Starburst galaxies are galaxies that are producing stars at a fantastic rate; faster than the stellar ingredients can be replenished.

Observations revealed over a dozen black holes and neutron stars feeding off gas from younger, massive stellar companions. These ‘X-ray binaries’ emit large amounts of X-ray light. As a massive star orbits a compact companion such as a black hole or neutron star, material can be pulled away to form a disk of material around the compact object. Frictional forces then heat up this material, producing a bright X-ray source.

Credit  X-ray: NASA/CXC/UMass Lowell/S.Laycock et al. Optical: Bill Snyder Astrophotography
09 - 13 Sep 2017
Saturn’s shadows

Cassini spacecraft, 13 September 2017

The Cassini mission ended 14 September 2017, as the spacecraft purposely crashed into Saturn’s atmosphere. This is one of the last images captured by Cassini, just before its final plunge.

Bright bands of clouds on Saturn disappear into the shadows in this image, which has also managed to capture the hexagonal storm at the planet’s north pole. We can clearly see Saturn’s rings emerging just beyond the limb on the left edge of the picture.

Credit: NASA/JPL-Caltech/Space Science Institute
10 - Moons of a gas giant
Satellites of a gas giant

Juno spacecraft, 6 October 2017

NASA’s Juno spacecraft is currently orbiting Jupiter, sending back data that is helping scientists unlock the secrets of the Gas Giant.

In this image, Jupiter’s limb can be seen top right, while its moons Io (right) and Europa (left) appear dwarfed in comparison. This image was processed by citizen scientist Roman Tkachenko using raw data captured by Juno.

Credit: NASA/JPL-Caltech/SwRI/MSSS/Roman Tkachenko
Multi wavelength composite astronomical image using data from the Jansky Very Large Array, Chandra X-ray Observatory, and optical data from the VLT and Subaru Telescopes.
Colliding clusters

Karl G Jansky Very Large Array / NASA Chandra X-ray Observatory, 7 November 2017

Galaxy clusters are some of the most massive objects in the Universe, so naturally create quite a scene when they collide. Abell 2744 is the collective name for one such collision, located 4 billion lightyears away. This collision produced an enormous amount of energy, seen as bright radio emission in red and orange, and purple X-rays caused by extreme heating.

Credit: Pearce et al.; Bill Saxton, NRAO/AUI/NSF; Chandra, Subaru; ESO.
WeAreMadeStarStuff
We are made of star stuffChandra X-ray Observatory, 12 December 2017

Many of the elements that make up our bodies and the world around us come from the scorching furnaces of stars. Astronomers study supernova remnants – the remains of exploded stars – to learn more about how stars produce and distribute these elements throughout the Universe.

Cassiopeia A is one of the most studied. Chandra observations revealed the iron in Cas A has the mass of about 70,000 Earths, and detected the ejection of oxygen equivalent to about three times the mass of the Sun.

Credit: NASA/CXC/SAO
###gallery-end###

Authors

Iain Todd, BBC Sky at Night Magazine

Iain Todd

Science journalist

Iain Todd is BBC Sky at Night Magazine's Staff Writer. He fell in love with the night sky when he caught his first glimpse of Orion, aged 10.

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