Starship Asterisk*

Image Credit: ESO/Petr Horálek

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This picture of the week showcases the night sky over the construction site for the Extremely Large Telescope. A beautiful array of stars and the hazy band of the Milky Way are clearly visible above the site. In order to see the Milky Way so distinctly, one must be in an area with low light pollution, such as the Chilean mountain Cerro Armazones, when there is little or no moonlight.

The ELT will be “the world’s biggest eye on the sky” when it begins operating in late 2025. With a 39-metre primary mirror, the ELT will search the sky in the optical and near-infrared wavelength regions for new exoplanets, specifically Earth-like planets in orbit around other stars. The ELT will also be able to perform a kind of “stellar archaeology,” answering fundamental questions about how planets, primordial stars, primordial galaxies and black holes form and evolve.

Perhaps the most exciting goal of the ELT is the possibility of making a direct measurement of the acceleration with which the Universe is expanding. Astrophysicists have known that the Universe is expanding for decades, meaning that the distances between galaxies are increasing. We now think this expansion is accelerating and to directly measure this acceleration would vastly increase humanity’s understanding of our Universe. ...

Image Credit: ESA/Hubble & NASA, P. Erwin et al

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This Picture of the Week, taken by the NASA/ESA Hubble Space Telescope, shows the galaxy NGC 4237. Located about 60 million light-years from Earth in the constellation of Coma Berenices (Berenice's Hair), NGC 4237 is classified as a flocculent spiral galaxy. This means that its spiral arms are not clearly distinguishable from each other, as in grand design spiral galaxies, but are instead patchy and discontinuous. This gives the galaxy a fluffy appearance, somewhat resembling cotton wool.

Astronomers studying NGC 4237 were actually more interested in its galactic bulge — its bright central region. By learning more about these bulges, we can explore how spiral galaxies have evolved, and study the growth of the supermassive black holes that lurk at the centres of most spirals. There are indications that the mass of the black hole at the centre of a galaxy is related to the mass of its bulge.

However, this connection is still uncertain, and why these two components should be so strongly correlated is still a mystery — one that astronomers hope to solve by studying galaxies in the nearby Universe, such as NGC 4237.

Image Credit: ESO/Babak Tafreshi

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The entire Universe is constantly on the move, from individual atoms all the way up to massive galaxy clusters. This is beautifully showcased in an image such as this, taken from the Chajnantor plateau some 5000 metres up in the Chilean Atacama Desert. This extremely arid and remote environment is home to the Atacama Large Millimeter/submillimeter Array (ALMA), the largest telescope array in existence.

The blurred object is a specialised transporter, caught in the act of carefully carrying one of ALMA’s 66 high-precision antennas to a specific position on the plateau. By arranging the antennas in more extended configurations, astronomers can obtain far more highly spatially resolved images (meaning that the image is more detailed), while more compact configurations give better sensitivity for sources which spread over more of the sky.

There’s movement going on above, too. Smooth stretches of cloud sweep across the pristine Chilean sky under the watch of Earth’s constant lunar companion. Given its tranquil, lantern-like appearance, it is easy to forget that the Moon is constantly hurtling round the Earth at breakneck speed. Further out, the visible pinpoints of starlight and the fuzzy shapes of galaxies may seem eternal, but of course they too are constantly moving and interacting. The many clear nights that Chajnantor has to offer provide ALMA with the perfect vantage point from which to see this flurry of cosmic activity.

Image Credit: ESA/Hubble & NASA, I. Karachentsev

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NGC 4618 was discovered on 9 April 1787 by the German-British astronomer, Wilhelm Herschel, who also discovered Uranus in 1781. Only a year before discovering NGC 4618, Herschel theorised that the “foggy” objects astronomers were seeing in the night sky were likely to be large star clusters located much further away then the individual stars he could easily discern.

Since Herschel proposed his theory, astronomers have come to understand that what he was seeing was a galaxy. NGC 4618, classified as a barred spiral galaxy, has the special distinction amongst other spiral galaxies of only having one arm rotating around the centre of the galaxy.

Located about 21 million light-years from our galaxy in the constellation Canes Venatici, NGC 4618 has a diameter of about one third that of the Milky Way. Together with its neighbour, NGC 4625, it forms an interacting galaxy pair, which means that the two galaxies are close enough to influence each other gravitationally. These interactions may result in the two (or more) galaxies merging together to form a new formation, such as a ring galaxy.

bystander wrote: ↑Mon Mar 23, 2020 2:31 pm Single Arm Galaxy
ESA Hubble Picture of the Week | 2020 Mar 23

Image Credit: ESA/Hubble & NASA, I. Karachentsev

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NGC 4618 was discovered on 9 April 1787 by the German-British astronomer, Wilhelm Herschel, who also discovered Uranus in 1781. Only a year before discovering NGC 4618, Herschel theorised that the “foggy” objects astronomers were seeing in the night sky were likely to be large star clusters located much further away then the individual stars he could easily discern.

Since Herschel proposed his theory, astronomers have come to understand that what he was seeing was a galaxy. NGC 4618, classified as a barred spiral galaxy, has the special distinction amongst other spiral galaxies of only having one arm rotating around the centre of the galaxy.

Located about 21 million light-years from our galaxy in the constellation Canes Venatici, NGC 4618 has a diameter of about one third that of the Milky Way. Together with its neighbour, NGC 4625, it forms an interacting galaxy pair, which means that the two galaxies are close enough to influence each other gravitationally. These interactions may result in the two (or more) galaxies merging together to form a new formation, such as a ring galaxy.

Susanna Kohler wrote:

Are baby planets responsible for the gaps and rings we’ve spotted in the disks that surround distant, young stars? A new study led by Christophe Pinte (Monash University, Australia; Univ. Grenoble Alpes, France) has found evidence supporting this theory in the images of eight circumstellar disks observed in the Disk Substructures at High Angular Resolution (DSHARP) project. DSHARP uses the Atacama Large Millimeter/submillimeter Array (ALMA) to explore the gas distributed within the disks around young stars. In the image ... the left-most panel shows the 1.3-millimeter dust continuum images of five complex circumstellar disks. The panels to the right show gas measurements for each disk in different velocity channels, revealing “velocity kinks” — deviations from the normal Keplerian velocity expected from unperturbed, orbiting gas. According to Pinte and collaborators, the kinks signatures of planets that perturb the gas flow in their vicinity.

• Astrophysical Journal Letters 890(1):L9 (2020 Feb 10) DOI: 10.3847/2041-8213/ab6dda
• arXiv.org > astro-ph > arXiv:2001.07720 > 21 Jan 2020

Image Credit: ESO/Yuri Beletsky

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This Picture of the Week captures the Milky Way streaking across the skies above the Chilean Atacama Desert. Dark wisps of interstellar dust form a turbulent mix with the bright glow of hot gas and billions of stars, creating a scene reminiscent of the thick smoke trail of a rocket after launch.

In contrast to the tempestuous sight above, a tower at ESO’s Paranal Observatory stands serenely beneath the evening sky. Paranal is home to the Very Large Telescope (VLT), a ground-breaking observatory composed of four Unit Telescopes and four movable Auxiliary Telescopes. The telescopes can be used in different combinations to form an interferometer, combining the light they collect and allowing astronomers to study the Universe in spectacular resolution.

The VLT has achieved many scientific firsts over the years, including tracking individual stars orbiting the centre of the Milky Way at unprecedented speeds. This indicated the presence of a powerful gravitational field, providing evidence that a supermassive black hole — named Sagittarius A* — lurks there.

Image Credit: ESA/Hubble & NASA, D. Leonard

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This remarkable spiral galaxy, known as NGC 4651, may look serene and peaceful as it swirls in the vast, silent emptiness of space, but don’t be fooled — it keeps a violent secret. It is believed that this galaxy consumed another smaller galaxy to become the large and beautiful spiral that we observe today.

Although only a telescope like the NASA/ESA Hubble Space Telescope, which captured this image, could give us a picture this clear, NGC 4651 can also be observed with an amateur telescope — so if you have a telescope at home and a star-gazing eye, look out for this glittering carnivorous spiral.

bystander wrote: ↑Mon Mar 30, 2020 3:59 pm Feeding Time
ESA Hubble Picture of the Week | 2020 Mar 30

Image Credit: ESA/Hubble & NASA, D. Leonard

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This remarkable spiral galaxy, known as NGC 4651, may look serene and peaceful as it swirls in the vast, silent emptiness of space, but don’t be fooled — it keeps a violent secret. It is believed that this galaxy consumed another smaller galaxy to become the large and beautiful spiral that we observe today.

Although only a telescope like the NASA/ESA Hubble Space Telescope, which captured this image, could give us a picture this clear, NGC 4651 can also be observed with an amateur telescope — so if you have a telescope at home and a star-gazing eye, look out for this glittering carnivorous spiral.