Starship Asterisk*

Image Credit: ESO/Babak Tafreshi

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This photo from the Ultra High Definition Expedition to ESO’s La Silla Observatory in Chile shows the Danish 1.54-metre telescope admiring the starry southern skies. The Southern Cross — one of the most distinctive asterisms — can be seen to the left of the telescope’s open dome, nestled in the plane of the Milky Way.

The constellation of Crux (The Cross) is best known for this cross-shaped asterism, which comprises four stars — Alpha, Beta, Gamma and Delta Crucis. The closest of these stars, Gamma Crucis, sits just 88 light-years from Earth, while the furthest is 364 light-years away. The blue–white star Alpha Crucis, the bottom point of the Cross, is the 13th brightest star in the entire night sky.

The dark, inky smudge just above the Southern Cross is the Coalsack Nebula, one of the most prominent dark nebulae visible to the naked eye. This opaque cloud of interstellar dust obscures the light emitted by more distant stars, creating a seemingly starless void in the midst of the Milky Way. The fiery red emission nebula IC 2948 and distinctive Carina Nebula can be seen below the Cross as two patches of nebulosity.

The Southern Cross has great significance in the Southern Hemisphere. For centuries, it — like the Big Dipper in northern skies — served as a beacon for navigators because the longer bar of the Cross points almost exactly towards the south pole of the sky. The Cross has also played an important role in the spiritual beliefs of many southern cultures and it is also the logo of the European Southern Observatory.

Image Credit: ESA/Hubble & NASA

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This Picture of the Week shows the colourful globular cluster NGC 2108. The cluster is nestled within the Large Magellanic Cloud, in the constellation of the Swordfish (Dorado). It was discovered in 1835 by the astronomer, mathematician, chemist and inventor John Herschel, son of the famous William Herschel.

The most striking feature of this globular cluster is the gleaming ruby-red spot at the centre left of the image. What looks like the cluster’s watchful eye is actually a carbon star. Carbon stars are almost always cool red giants, with atmospheres containing more carbon than oxygen — the opposite to our Sun. Carbon monoxide forms in the outer layer of the star through a combination of these elements, until there is no more oxygen available. Carbon atoms are then free to form a variety of other carbon compounds, such as C₂, CH, CN, C₃ and SiC₂, which scatter blue light within the star, allowing red light to pass through undisturbed.

This image was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), using three different filters.

bystander wrote: ↑Mon Aug 06, 2018 2:23 pm A Globular Cluster’s Striking Red Eye
ESA Hubble Picture of the Week | 2018 Aug 06

Image Credit: ESA/Hubble & NASA

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This Picture of the Week shows the colourful globular cluster NGC 2108. The cluster is nestled within the Large Magellanic Cloud, in the constellation of the Swordfish (Dorado). It was discovered in 1835 by the astronomer, mathematician, chemist and inventor John Herschel, son of the famous William Herschel.

The most striking feature of this globular cluster is the gleaming ruby-red spot at the centre left of the image. What looks like the cluster’s watchful eye is actually a carbon star. Carbon stars are almost always cool red giants, with atmospheres containing more carbon than oxygen — the opposite to our Sun. Carbon monoxide forms in the outer layer of the star through a combination of these elements, until there is no more oxygen available. Carbon atoms are then free to form a variety of other carbon compounds, such as C₂, CH, CN, C₃ and SiC₂, which scatter blue light within the star, allowing red light to pass through undisturbed.

This image was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), using three different filters.

Ann wrote: ↑Mon Aug 06, 2018 6:02 pm

bystander wrote: ↑Mon Aug 06, 2018 2:23 pm A Globular Cluster’s Striking Red Eye
ESA Hubble Picture of the Week | 2018 Aug 06

Image Credit: ESA/Hubble & NASA

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This Picture of the Week shows the colourful globular cluster NGC 2108. The cluster is nestled within the Large Magellanic Cloud, in the constellation of the Swordfish (Dorado). It was discovered in 1835 by the astronomer, mathematician, chemist and inventor John Herschel, son of the famous William Herschel.

The most striking feature of this globular cluster is the gleaming ruby-red spot at the centre left of the image. What looks like the cluster’s watchful eye is actually a carbon star. Carbon stars are almost always cool red giants, with atmospheres containing more carbon than oxygen — the opposite to our Sun. Carbon monoxide forms in the outer layer of the star through a combination of these elements, until there is no more oxygen available. Carbon atoms are then free to form a variety of other carbon compounds, such as C₂, CH, CN, C₃ and SiC₂, which scatter blue light within the star, allowing red light to pass through undisturbed.

This image was captured by the NASA/ESA Hubble Space Telescope’s Advanced Camera for Surveys (ACS), using three different filters.

Fascinating. Are we sure that the red carbon star is a member of the globular?

Ann

Credit: Petr Horálek/ESO

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This fulldome view of the Very Large Telescope (VLT), at ESO’s Paranal Observatory, shows almost all of the telescope’s constituent units in one family photograph!

ESO's VLT comprises four large 8.2-metre Unit Telescopes (UTs), all of which can be seen here and are recognised by their boxy appearance, and four 1.8-metre Auxiliary Telescopes (ATs), two of which are seen here flanking their bigger relatives (both with their rounded domes open). Alongside their standard designations — UT1, UT2, and so on — each of the four giant UTs has its own name in the local Chilean Mapuche language: Antu (The Sun), Kueyen (The Moon), Melipal (The Southern Cross), and Yepun (Venus).

The yellow laser streaking up into the night sky, launched by one of the UTs, creates an artificial star high in the atmosphere, fittingly known as a Laser Guide Star (LGS). This ‘star’ is part of the telescope’s adaptive optics system, which allows astronomers to compensate for the effects of atmospheric turbulence and achieve far clearer images.

The image was created by ESO Photo Ambassador Petr Horálek, and is a puzzle made up of numerous different pictures stitched together to form this high resolution panorama.

Credit: ESA/Hubble & NASA, RELICS

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Galaxies abound in this spectacular Hubble image; spiral arms swirl in all colours and orientations, and fuzzy ellipticals can be seen speckled across the frame as softly glowing smudges on the sky. Each visible speck of a galaxy is home to countless stars. A few stars closer to home shine brightly in the foreground, while a massive galaxy cluster nestles at the very centre of the image; an immense collection of maybe thousands of galaxies, all held together by the relentless force of gravity.

Galaxy clusters are some of the most interesting objects in the cosmos. They are the nodes of the cosmic web that permeates the entire Universe — to study them is to study the organisation of matter on the grandest of scales. Not only are galaxy clusters ideal subjects for the study of dark matter and dark energy, but they also allow the study of farther-flung galaxies. Their immense gravitational influence means they distort the spacetime around them, causing them to act like giant zoom lenses. The light of background galaxies is warped and magnified as it passes through the galaxy cluster, allowing astronomers insight into the distant — and therefore early — Universe.

This image was taken by Hubble’s Advanced Camera for Surveys (ACS) and Wide-Field Camera 3 (WFC3) as part of an observing programme called RELICS (Reionization Lensing Cluster Survey). RELICS imaged 41 massive galaxy clusters with the aim of finding the brightest distant galaxies for the forthcoming NASA/ESA/CSA James Webb Space Telescope (JWST) to study.

Image Credit: Petr Horálek/ESO

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In this spectacular image, taken by ESO Photo Ambassador Petr Horálek, we see the bright arc of the Milky Way stretching across the sky above ESO’s La Silla Observatory in Chile. On the ground are the dome of ESO’s 3.6-metre optical telescope (on the right) and the silvery dish of the Swedish-ESO submillimetre telescope (on the left). Even though it was decommissioned in 2003 to make way for the more advanced APEX and ALMA instruments, the Swedish-ESO dish still seems to be gazing longingly at the sky, perhaps hoping for another chance to explore the mysteries of the heavens.

The Milky Way dominates this image, showing clearly why La Silla is one of the best astronomical sites in the world, famed for its dark skies and clear air. From the peak of the bright arc hangs a striking red feature known as Gum Nebula. This, like similar regions along the band of the Milky Way, is an emission nebula, where gas is made to glow by radiation emitted from nearby bright stars. The bright band of the Milky Way is broken up by dark filaments of dust, wherein stars are forming, stars that will add to the spectacle in the millennia to come.

Sitting under the arc is one of the Milky Way’s companion dwarf galaxies, the Large Magellanic Cloud; below it, just to the right of the Swedish-ESO dish, is the second such companion, known unsurprisingly as the Small Magellanic Cloud. Over to the right of the image is the planet Jupiter, glowing brightly against the faint glow of the gegenschein, a phenomenon only seen in the darkest skies. A rare sight for most, this magical celestial display is commonplace at astronomical observing sites like La Silla.

Image Credit: ESA/Hubble & NASA

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The Hubble Deep Field (HDF) from 1995 allowed astronomers a first glimpse into the early Universe. This first picture was followed later by an even deeper observation, the Hubble Ultra Deep Field (HUDF) in 2004. Both images were observed in visible light, the same form of light human eyes can see. But astronomers are also interested in the many forms of invisible light out in the Universe. Therefore, the Ultra Deep Field was later observed in the infrared and the ultraviolet as well, allowing scientists to learn even more about the Universe and to look back even further into its history.

It is less known that the famous deep field observations were not the only images the NASA/ESA Hubble Space Telescope took of the distant Universe. Hubble is also an essential part of the GOODS (The Great Observatories Origins Deep Survey) programme, which unites extremely deep observations from several space telescopes: NASA’s Spitzer and Chandra; ESA's Herschel and XMM-Newton; and Hubble.

Together these observatories observe two patches of the sky, the GOODS North and the GOODS South fields, with the aim of studying it in as many different wavelengths as possible. The new image here shows part of the GOODS North Field; it includes new Hubble data at ultraviolet wavelengths in addition to the existing data. Because Earth’s atmosphere filters out most ultraviolet light, these observations can only be accomplished from space.

The observation programme, called the Hubble Deep UV (HDUV) Legacy Survey, harnessed the ultraviolet vision of Hubble’s Wide Field Camera 3 (WFC3). This study extends and builds on the previous Hubble multi-wavelength data in the CANDELS-Deep (Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey) fields within the central part of the GOODS (The Great Observatories Origins Deep Survey) fields. This mosaic is 14 times the area of the Hubble Ultraviolet Ultra Deep Field (UVUDF) released in 2014.

Ann wrote: ↑Sun Aug 26, 2018 1:56 pm NGC 4691
http://www.caelumobservatory.com/gallery/n4691.shtml
Copyright: Adam Block

NGC 4691.png

Adam Block has posted a new picture of a galaxy, the remarkable barred spiral galaxy NGC 4691.

The entire spiral pattern of NGC 4691 is extremely fuzzy and devoid of any signs of youth. It looks like it is billions of years old. The bar, by contrast, is bursting with ongoing star formation. This is very unusual!

According to Principal Galaxy Catalog, the distance to NGC 4691 is about 47 million light-years, which would make it a little closer than the Virgo Cluster, and its true brightness would be 6 billion stars like the Sun, or 0.3 times the brightness of the Milky Way. But according to this page, NGC 4691 is located some 73 million light-years away, and its true brightness would be much higher.

Ann