Starship Asterisk*

bystander wrote: ↑Mon Feb 25, 2019 5:42 pm NGC 6902 Caught by SPECULOOS
ESO Picture of the Week | 2019 Feb 25

Credit: ESO/SPECULOOS

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This Picture of the Week is a special treat: a first-light image from the newest resident of ESO’s Paranal Observatory, the SPECULOOS Southern Observatory. This planet-hunting machine aims to observe nearby but dim stars to locate exoplanets for other telescopes — such as ESO’s forthcoming Extremely Large Telescope (ELT) — to study in detail. Comprising four one-metre telescopes, each named after one of Jupiter’s Galilean moons, SPECULOOS promises to open up new frontiers in exoplanet research.

This image, however, is obviously not of a faint star, but of a galaxy called NGC 6902. Before a telescope starts its primary mission it must successfully undertake an event called “first light”: the first time it is used for a scientific observation. Astronomers typically pick well-known objects for this initial test of a telescope’s capabilities, which is half demonstration and half celebration. In this case, the team settled on NGC 6902 as the first-light target for the Ganymede telescope.

The result was this stunning image of the spiral galaxy, which is found about 120 million light-years from Earth in the constellation of Sagittarius (The Archer). The galaxy’s spiral arms swirl outwards from a bright centre until they dissolve into streams of blue haze at the galaxy’s edge. If this is what Ganymede can produce as its first observation of something it wasn’t even designed to image, we have a lot to look forward to. Watch this space!

Image Credit: ESA/Hubble & NASA, S. Larsen et al.

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Globular clusters like NGC 2419, visible in this image taken with the NASA/ESA Hubble Space Telescope, are not only beautiful, but also fascinating. They are spherical groups of stars which orbit the centre of a galaxy; in the case of NGC 2419, that galaxy is the Milky Way. NGC 2419 can be found around 300 000 light-years from the Solar System, in the constellation Lynx (the Lynx).

The stars populating globular clusters are very similar to one another, with similar properties such as metallicity. The similarity of these stellar doppelgängers is due to their formation early in the history of the galaxy. As the stars in a globular cluster all formed at around the same time, they tend to display reasonably homogeneous properties. It was believed that this similarity also extended to the stellar helium content; that is, it was thought that all stars in a globular cluster would contain comparable amounts of helium.

However, Hubble’s observations of NGC 2419 have shown that this is not always the case. This surprising globular cluster turns out to be made up of two separate populations of red giant stars, one of which is unusually helium-rich. Other elements within the different stars in NGC 2419 vary too — nitrogen in particular. On top of this, these helium-rich stars were found to be predominantly in the centre of the globular cluster, and to be rotating. These observations have raised questions about the formation of globular clusters; did these two drastically different groups of stars form together? Or did this globular cluster come into being by a different route entirely?

Credit: ESO/SPECULOOS

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This Picture of the Week is a special treat: a first-light image from the newest resident of ESO’s Paranal Observatory, the SPECULOOS Southern Observatory. This planet-hunting machine aims to observe nearby but dim stars to locate exoplanets for other telescopes — such as ESO’s forthcoming Extremely Large Telescope (ELT) — to study in detail. Comprising four one-metre telescopes, each named after one of Jupiter’s Galilean moons, SPECULOOS promises to open up new frontiers in exoplanet research.

This image, however, is obviously not of a faint star, but of a galaxy called NGC 6902. Before a telescope starts its primary mission it must successfully undertake an event called “first light”: the first time it is used for a scientific observation. Astronomers typically pick well-known objects for this initial test of a telescope’s capabilities, which is half demonstration and half celebration. In this case, the team settled on NGC 6902 as the first-light target for the Ganymede telescope.

The result was this stunning image of the spiral galaxy, which is found about 120 million light-years from Earth in the constellation of Sagittarius (The Archer). The galaxy’s spiral arms swirl outwards from a bright centre until they dissolve into streams of blue haze at the galaxy’s edge. If this is what Ganymede can produce as its first observation of something it wasn’t even designed to image, we have a lot to look forward to. Watch this space!

Credit: ALMA (ESO/NAOJ/NRAO); M. Cordiner, NASA/CUA

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In December 2018, the comet 46P/Wirtanen passed within 11.6 million kilometres of the Earth — about 30 times the distance from the Earth to the Moon. This close pass gave astronomers the chance to observe the comet in detail, and ALMA (the Atacama Large Millimeter/submillimeter Array) took full advantage. ALMA’s speciality is observing the cooler components of the Universe, such as gas and dust, and the array often focuses on specific molecules. This image is no exception, as it highlights one key thing: the hydrogen cyanide gas in the coma around the comet’s nucleus.

But why would scientists be looking for an infamous poison? Well, it turns out that hydrogen cyanide is as common as mystery novels have led us to believe — throughout the cosmos, at least! Because it’s a simple organic molecule that forms relatively easily, it’s been observed in comets, stellar atmospheres, and the clouds of dust and gas that exist between stars. This image builds on those observations by showing clearly the hydrogen cyanide emanating from the nucleus of this comet. Further ALMA observations showed that other, more complex organic molecules were present, too.

This matters because, while it may be poisonous to many organisms on Earth today, hydrogen cyanide may have played an important role in getting life started on Earth. It’s very reactive, so it easily interacts with surrounding chemicals to create new molecules — including some of those essential for life, such as amino acids. One theory posits that hydrogen cyanide, brought here in part by comets, jump-started organic chemistry here on Earth, eventually leading to the beginning of life. ALMA’s imaging of 46P/Wirtanen further supports the idea that comets could have brought this life-giving material to the early Earth.

Credit: NASA, ESA, A.A. Simon (GSFC), and M.H. Wong and A.I. Hsu (UC Berkeley)

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Since Pluto’s demotion from fully-fledged planet to dwarf planet, Neptune holds the title of outermost planet in the Solar System. This new image of the planet was made during Hubble’s Outer Planet Atmosphere Legacy (OPAL) programme, under which it has observed the four outermost planets, including Neptune, on a yearly basis since 2014.

The observations of Neptune carried out in September and November 2018 show the first evidence of a huge storm brewing, with the discovery of a new northern Great Dark Spot (visible here to the upper left of the planet’s disc, partially overlapping a large patch of white). This new dark storm is of a similar size and shape to the storm discovered in 1989 by the Voyager 2 space probe.

While the future evolution of the storm will be tracked through the continued yearly Hubble observations and also by ground-based telescopes, older OPAL observations from Hubble show that its appearance was preceded by increased cloud activity throughout the region. There are hints of the storm forming in images from as early as 2015. This slow origin process indicates that the storm developed deep within Neptune's atmosphere, pulling up dark material from its depths, and only became visible once the top of it reached higher altitudes.

Credits: NASA, ESA, A. Simon (GSFC), and M.H. Wong and A. Hsu (UC Berkeley)

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One of the NASA/ESA Hubble Space Telescope’s many scientific objectives is to study the planets within the Solar System — and in past years, our system’s outer planets have been observed several times as part of Hubble’s Outer Planet Atmosphere Legacy (OPAL) programme.

This programme has given us this new image of the planet Uranus, the seventh planet in the Solar System in order of increasing distance from the Sun. Past observations of Uranus using Hubble have led to many interesting insights about the cold ice giant; in 2006 the telescope managed to capture a shot in which the moon Ariel and its accompanying shadow were traversing the face of Uranus (opo0642b), and in 2011 Hubble was able to spot faint auroras in its atmosphere (opo1221a).

Observations made over the course of several years also allowed astronomers to study the planet’s faint ring system as its inclination changed with respect to Earth’s orbit. This new image, taken with Hubble’s Wide Field Camera 3 (WFC3), adds to the legacy of images already taken and will provide scientists with even more new insights into our distant neighbour.

Credit: ALMA (ESO/NAOJ/NRAO), S. Andrews et al.; NRAO/AUI/NSF, S. Dagnello

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This week’s Picture of the Week highlights another of the 20 images to come out of ALMA’s first Large Program, the Disk Substructures at High Angular Resolution Project (DSHARP). DSHARP explored a number of nearby protoplanetary discs to learn more about the earliest stages of planet formation, and a staggering quantity of data from the project has just been released.

This object, called AS 205, is notable for being a multiple star system, one of two such systems imaged by DSHARP (the other being HT Lup). While two discs are discernible here, the lower right disc is in fact shared by two stars in a binary system, so we are actually looking at a system of three fledgling stars.

Although most high-resolution studies have so far focused on single stars, multiple systems are far from uncommon in the Universe. It is thought that over half of all stars may exist in multiple systems, an estimate that may be even higher for young stars. The presence of companion stars is likely to have complex implications for a disc and its substructures. This is due to as the gravitational influence of a stellar neighbour, which may distort and redistribute the material within the disc. Data from AS 205 and HT Lup indicate that stars and their neighbouring discs interact strongly.

Despite their unsettled birth environments, planets have been detected in multiple stellar systems — some orbiting just one of the stars, others orbiting the entire system. The latter are more likely to have stable orbits than the former, which get caught up in volatile interstellar dynamics.