Starship Asterisk*

Image Credit: ESO/Yuri Beletsky

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Far from civilisation, deep in the barren, mountainous terrain of Chile’s Atacama Desert, stand four pillars of modern astronomy: the enormous and angular enclosures of the Unit Telescopes (UTs) of ESO’s Very Large Telescope (VLT).

The Sun’s diffuse orange glow peeking over the horizon is no match for the light display filling the sky above. Containing hundreds of billions of stars, the great bow of the Milky Way stretches across the panorama, dipping down to touch the horizon. The mottled look of our home galaxy is due to huge clouds of interstellar dust obscuring more distant starlight. Bright stars, celestial objects, and other phenomena in our cosmic neighbourhood hang like lanterns in the Chilean sky, backlit by ethereal red and green airglow.

Alone, each UT can make magnificent observations of the Universe from their home at ESO’s Paranal Observatory — but the four telescopes can also work together and observe the cosmos as a quartet, producing a telescope with an effective mirror diameter of up to 130 metres.

Credit: ESA/Hubble, NASA, J. Lee, PHANGS-HST Team

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Located in the constellation of Virgo (The Virgin), around 50 million light-years from Earth, NGC 4535 is truly a stunning sight to behold. Despite the incredible quality of this image, taken from the NASA/ESA Hubble Space Telescope, NGC 4535 has a hazy, somewhat ghostly, appearance when viewed from a smaller telescope. This led amateur astronomer Leland S. Copeland to nickname NGC 4535 the “Lost Galaxy” in the 1950s.

The bright colours in this image aren’t just beautiful to look at, as they actually tell us about the population of stars within this barred spiral galaxy. The bright blue-ish colours, seen nestled amongst NGC 4535’s long, spiral arms, indicate the presence of a greater number of younger and hotter stars. In contrast, the yellower tones of this galaxy’s bulge suggest that this central area is home to stars which are older and cooler.

This galaxy was studied as part of the PHANGS survey, which aims to clarify many of the links between cold gas clouds, star formation, and the overall shape and other properties of galaxies. On 11 January 2021 the first release of the PHANGS-HST Collection was made publicly available.

Image Credit: ESO / Petr Horálek

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The road to ESO’s La Silla Observatory in the Chilean Atacama Desert appears to curve around the mountain and collide with the downward slope of the Milky Way in this Picture of the Week. Small yellow bulbs light up the road at regular intervals; it is prohibited to use headlights on these roads between dusk and dawn, as even dim lights can interfere significantly with telescope observations. The site enjoys some of the darkest night skies on Earth.

The darkness, high altitude, and resulting dry air at La Silla make it an exceptional location for astronomy. In the foreground of this image, the Danish 1.54-metre telescope is performing its nightly observations. Its instruments have allowed astronomers to achieve several “firsts”. In 2005, for example, astronomers observed the afterglows of short gamma-ray bursts and showed that the bursts are likely caused by the dramatic collision of two neutron stars, while in 2006 the telescope was part of a global network of telescopes that discovered an exoplanet just five times as massive as Earth.

A number of interesting objects populate the sky above the observatory. To the left, almost hidden behind the telescope, is the faint green glow of Comet 252P/LINEAR and, overhead, the tail of Scorpius curves into the glowing clouds of the Milky Way, keeping close company to Mars and Saturn. Further up the bright galactic band are two bright stars — the intriguing triple-star systems Alpha and Beta Centauri — and at the very top right of the image is the iconic diamond of the Southern Cross.

Credit: ESA/Hubble & NASA, L. Stanghellini

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The lives of planetary nebulae are often chaotic, from the death of their parent star to the scattering of its contents far out into space. Captured here by the NASA/ESA Hubble Space Telescope, ESO 455-10 is one such planetary nebula, located in the constellation of Scorpius (The Scorpion).

The oblate shells of ESO 455-10, previously held tightly together as layers of its central star, not only give this planetary nebula its unique appearance, but also offer information about the nebula. Seen in a field of stars, the distinct asymmetrical arc of material over the north side of the nebula is a clear sign of interactions between ESO 455-10 and the interstellar medium.

The interstellar medium is the material — consisting of matter and radiation — between star systems and galaxies. The star at the centre of ESO 455-10 allows Hubble to see the interaction with the gas and dust of the nebula, the surrounding interstellar medium, and the light from the star itself. Planetary nebulae are thought to be crucial in galactic enrichment as they distribute their elements, particularly the heavier metal elements produced inside a star, into the interstellar medium which will in time form the next generation of stars.

Click to view full size image

To celebrate a new year, the NASA/ESA Hubble Space Telescope has published a montage of six beautiful galaxy mergers. Each of these merging systems was studied as part of the recent HiPEEC survey to investigate the rate of new star formation within such systems. These interactions are a key aspect of galaxy evolution and are among the most spectacular events in the lifetime of a galaxy.

It is during rare merging events that galaxies undergo dramatic changes in their appearance and in their stellar content. These systems are excellent laboratories to trace the formation of star clusters under extreme physical conditions.

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Top left: NGC 3256

This image of NGC 3256 was taken with the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS), both installed on the NASA/ESA Hubble Space Telescope. The galaxy is about 100 million light-years from Earth and provides an ideal target in which to investigate starbursts that have been triggered by galaxy mergers.

Credit: ESA/Hubble, NASA

Top Middle: NGC 1614

The galaxy system NGC 1614 has a bright optical centre and two clear inner spiral arms that are fairly symmetrical. It also has a spectacular outer structure that consists principally of a large one-sided curved extension of one of these arms to the lower right, and a long, almost straight tail that emerges from the nucleus and crosses the extended arm to the upper right.

Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

Top Right: NGC 4194 Snakes and Stones

NGC 4194 is also known as the Medusa merger. An early galaxy consumed a smaller gas-rich system, throwing out streams of stars and dust out into space. These streams, seen rising from the top of the merger galaxy, resemble the writhing snakes that Medusa, a monster in ancient Greek mythology, famously had on her head in place of hair, lending the object its intriguing name. The Medusa merger is located about 130 million light-years away in the constellation of Ursa Major (The Great Bear).

Credit: ESA/Hubble & NASA, A. Adamo

Bottom Left: NGC 3690

This system consists of a pair of galaxies, dubbed IC 694 and NGC 3690, which made a close pass some 700 million years ago. As a result of this interaction, the system underwent a fierce burst of star formation. In the last fifteen years or so six supernovae have popped off in the outer reaches of the galaxy, making this system a distinguished supernova factory.

Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University)

Bottom Middle: NGC 6052 Colliding Galaxies

Located in the constellation of Hercules, about 230 million light-years away, NGC 6052 is a pair of colliding galaxies. They were first discovered in 1784 by William Herschel and were originally classified as a single irregular galaxy because of their odd shape. However, we now know that NGC 6052 actually consists of two galaxies that are in the process of colliding. This particular image of NGC 6052 was taken using Hubble’s Wide Field Camera 3.

Credit: ESA/Hubble & NASA, A. Adamo et al.

Bottom Right: NGC 34 Beauty From Chaos

Lying in the constellation Cetus (The Sea Monster), NGC 34’s outer region appears almost translucent, pin pricked with stars and strange wispy tendrils. This image shows the galaxy's bright centre, a result of this merging event that has created a burst of new star formation and lit up the surrounding gas. As the galaxies continue to intertwine and become one, NGC 34’s shape will become more like that of a peculiar galaxy, devoid of any distinct shape.

Credit: ESA/Hubble & NASA, A. Adamo et al.

• Monthly Notices of the RAS 499(3):3267 (Dec 2020) DOI: 10.1093/mnras/staa2380
• arXiv.org > astro-ph > arXiv:2008.12794 > 28 Aug 2020

A treasure trove of data from the SMASH survey unveils the Magellanic Clouds in exquisite detail

Part of the SMASH dataset showing an unprecedented wide-angle view of the Large
Magellanic Cloud (top) and Small Magellanic Cloud (bottom). The Magellanic Clouds
are the largest satellite galaxies of the Milky Way and, unlike the rest of the satellite
galaxies, are still actively forming stars — and at a rapid pace.
Credit: CTIO/NOIRLab/NSF/AURA/SMASH/D. Nidever (Montana State Univ)
Image Processing: Travis Rector (Univ of Alaska), Mahdi Zamani, & Davide de Martin

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Images from the Survey of the MAgellanic Stellar History (SMASH) reveal a striking family portrait of our galactic neighbors — the Large and Small Magellanic Clouds. The images represent a portion of the second data release from the deepest, most extensive survey of the Magellanic Clouds. The observations consist of roughly 4 billion measurements of 360 million objects.

A sprawling portrait of two astronomical galactic neighbors presents a new perspective on the swirls of stars, gas, and dust making up the nearby dwarf galaxies known as the Large and Small Magellanic Clouds — a pair of dwarf satellite galaxies to our Milky Way. While this isn’t the first survey to map these nearby cosmic siblings — the Survey of the Magellanic Stellar History (SMASH) is the most extensive survey yet.

The international team of astronomers responsible for the observations used the 520-megapixel high-performance Dark Energy Camera (DECam) on the Víctor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. These data are now available to astronomers worldwide through Astro Data Lab at NOIRLab’s Community Science and Data Center (CSDC). CTIO and CSDC are both Programs of NSF’s NOIRLab. ...

The complete SMASH survey, which includes the view shown in these images, covers an area 2,400 times greater than the full Moon, and required about 50 nights of specialized observations. This second data release contains new data from DOE-built DECam on the central and most complex regions of the Magellanic Clouds. The Large and Small Magellanic Clouds are the largest satellite galaxies of the Milky Way and, unlike the rest of the satellite galaxies, are still actively forming stars — and at a rapid pace. ...

As the Magellanic Clouds are so close to the Milky Way, they sprawl across a large area of the sky, making it challenging to map their full extent. DECam’s huge field of view allowed astronomers to capture details within some of the most interesting regions of these dwarf galaxies.

The SMASH team are using their deep dataset to study the history of star formation across both of these galaxies. They have uncovered evidence that the pair of galaxies have collided with each other in the recent past and that this sparked the recent episode of intense star formation. ...

• Astronomical Journal 161(2):74 (2021 Feb) DOI: 10.3847/1538-3881/abceb7
• arXiv.org > astro-ph > arXiv:2011.13943 > 27 Nov 2020

Stunning deep image of NGC 1003 reveals hundreds of cluster galaxies

NGC 1003 ~ Credit: KPNO/NOIRLab/NSF/AURA, M T. Patterson (New Mexico State Univ) Image Processing: Travis Rector (Univ of Alaska), Mahdi Zamani, & Davide de Martin

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A stunning long-exposure observation from the Kitt Peak National Observatory reveals the spiral galaxy NGC 1003 in glorious detail. The deep observation also shows a treasure trove of background galaxies spread throughout the image.

Astronomers refer to observations as “deep” when they are taken with very long exposure times. Just as with photography, this gathers more light, revealing distant, fainter objects. Deeper exposures let astronomers look deeper into the Universe — hence the name. This particular deep image was taken with a 70-minute exposure with the Nicholas U. Mayall 4-meter Telescope at Kitt Peak National Observatory, a Program of NSF’s NOIRLab, and captures the spiral galaxy NGC 1003.

NGC 1003 lies over 30 million light-years from Earth in the direction of the constellation Perseus. While it makes for a spectacular sight, it is only one of many galaxies captured in this image. Upon closer inspection, other galaxies can also be seen strewn throughout the image, with everything from delicate spiral galaxies to hundreds of fuzzy, red elliptical galaxies lurking in the background. The long exposure time of this deep observation — arguably the deepest image of NGC 1003 ever captured — allowed these usually overlooked background cluster galaxies to be captured in breathtaking detail. ...

Susanna Kohler wrote:

The panels in the image ... show frames from a dramatic simulation of the collision of a planetary-mass impactor with the proto-Earth in the early solar system. In the chaos that follows the collision, the debris that doesn’t escape settles into a disk around the young Earth — a disk that will later form into our Moon. While the giant impact described here has been simulated in detail in the past, most models have yet to incorporate the effects of magnetic fields into the giant impact and the subsequent evolution of the protolunar disk. In a new study, scientists Patrick Mullen and Charles Gammie (University of Illinois at Urbana-Champaign) develop state-of-the-art simulations that include weak initial magnetic fields. The authors show how these fields are amplified by turbulence in the collision, impacting the how the disk — and, ultimately, the Moon — evolves. ...

• Astrophysical Journal Letters 903(1):L15 (2020 Nov 01) DOI: 10.3847/2041-8213/abbffd
• arXiv.org > astro-ph > arXiv:2010.04798 > 09 Oct 2020

Susanna Kohler wrote:

Some astronomical mysteries are found deep in the interiors of stars. Such is the case with the puzzle of Q-branch white dwarfs, a population of these evolved, dense stars that seems to have an unexpected heat source, causing them to cool more slowly than a typical white dwarf. One hypothesis proposes that Q-branch white dwarfs gain extra heat from the rapid sedimentation — sinking to the center of the star — of neutron rich neon, ^₂₂Ne. But recent molecular dynamics simulations conducted by Matt Caplan (Illinois State U.), Charles Horowitz (Indiana U.), and Andrew Cumming (McGill U., Canada) show that the tiny crystals of neon needed to speed up this sedimentation can’t exist in a stable state in the interior of a typical white dwarf — which means there must be some other mechanism at work heating Q-branch white dwarfs. The image above shows the initial state of the authors’ simulations, in which a ^₂₂Ne microcrystal (red) lies within a soup of carbon and oxygen (white) under the dense, high-pressure conditions that exist inside a white dwarf.

• Astrophysical Journal Letters 902(2):L44 (2020 Oct 20) DOI: 10.3847/2041-8213/abbda0
• arXiv.org > astro-ph > arXiv:2010.00036 > 30 Sep 2020

Susanna Kohler wrote:

Did you know that the stars around us are organized into a tangle of threads and strings? The unprecedented precision and sensitivity of the Gaia second data release has given us the ability to map the precise locations of and distances to the stars around us, allowing us to piece together these clusters and structures. In a new study led by Marina Kounkel (Western Washington University), a team of scientists has conducted clustering analysis to identify a total of 8,292 structures of stars within about 10,000 light-years of us. These threads have a typical length of ~650 light-years and width of ~30 light-years, and they likely trace the shape of the filamentary giant molecular clouds from which they formed. The image above shows the 2D projection of the locations of some of these clustered stars, but to really dive into the data, you need to see it in 3D. For that, you can check out the authors’ interactive figure, which allows you to manipulate their data and view the strings from your angle of choice. We’ll be discussing interactive figures further on this site soon! In the meantime, you can check out the authors’ work (and their figures) in the article below.

• Astronomical Journal 160(6):279 (2020 Dec) DOI: 10.3847/1538-3881/abc0e6
• arXiv.org > astro-ph > arXiv:2004.07261 > 15 Apr 2020 (v1), 06 Oct 2020 (v2)

Susanna Kohler wrote:

A new pair of free-floating planetary-mass objects has recently been identified via direct imaging: Oph 98 AB. In a study led by Clémence Fontanive (University of Bern, Switzerland), a team of scientists presents their observations of this set of two bodies locked in an exceptionally wide orbit. In the three views above (click for a closer look), captured at different times with different telescopes, you can see Oph 98 A and B as the two bright objects at the centers of the images. The additional source at the top right is a background star. Fontanive and collaborators show that this binary system consists of two bodies of perhaps 15 and 8 Jupiter masses, separated by around 200 au (for reference, Pluto’s semimajor axis is just 39 au!). The low masses and wide separation of Oph 98 AB make it the lowest binding energy system imaged to date, and it’s sure to offer us new insight into young, free-floating planetary-mass objects. To learn more, check out the original article below.

• Astrophysical Journal Letters 905(2):L14 (2020 Dec 20) DPI: 10.3847/2041-8213/abcaf8
• arXiv.org > astro-ph > arXiv:2011.08871 > 17 Nov 2020

How do systems of multiple stars form in the dense cores inside molecular clouds? Systems like the one captured above, L1448 IRS3B and A, may help us to better understand this process. In the image shown above (and again below, with scales and color bars), the triple protostar system IRS3B is seen in the process of forming from a surrounding (circum-triple) disk of molecular gas and dust. An additional disk can be seen at the opposite end of the image: IRS3A, a wide companion that lies 2,300 au away. In a recent study led by Nickalas Reynolds (University of Oklahoma), a team of scientists peered deep into the Perseus molecular cloud with the Atacama Large Millimeter/submillimeter Array (ALMA) to produce these images and study IRS3B and A. Reynolds and collaborators determine from their observations that the disk of IRS3B is gravitationally unstable at radii of 200–500 au, and its fragmentation may have recently produced the third protostar in IRS3B (visible as the outer bright spot in the circum-triple disk), which lies at 230 au. For more information, check out the full figure and the article below.

• Astrophysical Journal Letters 907(1):L10 (2021 Jan 20) DOI: 10.3847/2041-8213/abcc02
• arXiv.org > astro-ph > arXiv:2011.08293 > 16 Nov 2020