Starship Asterisk*

Susanna Kohler wrote:

This complex map shows the locations of dust in our galaxy, as measured out to a distance of 500 pc (roughly 1,630 light-years). Dust reveals important information about galactic structure and star formation — but it can also present a hindrance, dimming and reddening faraway sources. To correctly interpret distant observations, we need an accurate picture of how dust is distributed within our galaxy. A team of scientists led by Gregory Green (Stanford, MPIA) have now built a detailed three-dimensional map of dust reddening in our galaxy out to a distance of a few kiloparsecs (~10,000 light-years). The authors accomplished this by using Gaia parallaxes and stellar photometry from Pan-STARRS 1 and 2MASS to infer the distances, reddenings, and types of 799 million stars. Their 3D map and data are freely accessible for use ...

• Astrophysical Journal 887(1):93 (2019 Dec 10) DOI: 10.3847/1538-4357/ab5362
• arXiv.org > astro-ph > arXiv:1905.02734 > 07 May 2019

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

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The galaxy depicted in this Picture of the Week is a barred spiral known as NGC 7541, seen here as viewed by the NASA/ESA Hubble Space Telescope, in the constellation of Pisces (The Fishes).

A barred spiral is a galaxy with whirling, pinwheeling, spiral arms, and a bright centre that is intersected by a bar of gas and stars. This bar cuts directly through the galaxy’s central region, and is thought to invigorate the region somewhat, sparking activity and fuelling myriad processes that may otherwise have never occurred or have previously ground to a halt (star formation and active galactic nuclei being key examples). We think bars exist in up to two-thirds of all spiral galaxies, including our own home, the Milky Way.

NGC 7541 is actually observed to have a higher-than-usual star formation rate, adding weight to the theory that spiral bars act as stellar nurseries, corralling and funnelling inwards the material and fuel needed to create and nurture new baby stars. Along with its nearby companion NGC 7537, the galaxy makes up a pair of galaxies located about 110 million light-years away from us.

Image Credit: ESO/Babak Tafreshi (TWAN)

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In this photograph, taken by ESO Photo Ambassador Babak Tafreshi, a slice of fiery colour streaks along the horizon near Paranal Observatory in northern Chile, bathing the four Unit Telescopes of the Very Large Telescope (VLT) in a soft, peachy glow.

The Milky Way appears to soar directly up from one of the Unit Telescopes, bounded on either side by a spectacular array of stars — including Sirius, which dazzles at the top of the image. Part of Canis Major (The Greater Dog), Sirius is the brightest star in the sky and is actually a binary system, consisting of a main-sequence star (Sirius A, a star in stable “adulthood” that is burning nuclear fuel) and a white dwarf (Sirius B, the dense corpse of a star that ran out of fuel long ago).

Wander down the edge of the Milky Way, and you might spy a small group of bright stars to the left. This is Orion’s belt, an eye-catching asterism composed of three stars lying in a straight line. A red giant star named Betelgeuse lies to the right of the belt, and the pinkish glow of the Orion Nebula can be seen to the left. These objects form part of the constellation of Orion, named for the mighty hunter from Ancient Greek mythology.

Further down, past the face of Taurus (the Bull) and just above a small open dome gazing eagerly at the night sky (a VLT Auxiliary Telescope), a tightly clustered group of stars hangs above the bright horizon. This is the Pleiades, or Seven Sisters, an open star cluster dominated by hot, blue B-type stars — and one of the nearest clusters to Earth.

Image Credit: ESA/Hubble & NASA, A. Seth

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This peculiar galaxy, beautifully streaked with tendrils of reddish dust, is captured here in wonderful detail by the NASA/ESA Hubble Space Telescope.

The galaxy is known as NGC 1022, and is officially classified as a barred spiral galaxy. You can just about make out the bar of stars in the centre of the galaxy in this image, with swirling arms emerging from its ends. This bar is much less prominent than in some of the galaxy’s barred cousins and gives the galaxy a rather squat appearance; but the lanes of dust that swirl throughout its disc ensure it is no less beautiful.

Hubble observed this image as part of a study into one of the Universe’s most notorious residents: black holes. These are fundamental components of galaxies, and are thought to lurk at the hearts of many — if not all — spirals. In fact, they may have quite a large influence over their cosmic homes. Studies suggest that the mass of the black hole sitting at a galaxy’s centre is linked with the larger-scale properties of the galaxy itself. However, in order to learn more, we need observational data of a wider and more diverse range of galaxies — something Hubble’s study aims to provide.

Credit: ESO Cosmic Gems/VLT/FORS

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The Milky Way contains many regions of starbirth — areas where new stars are springing to life within collapsing clumps of gas and dust. One such region, named Gum 26, is shown here as imaged by the FORS instrument on ESO’s Very Large Telescope in Chile.

Gum 26 is located roughly 20,000 light-years away in the southern constellation of Vela (The Sails). It is something known as an HII region or emission nebula, where the intense ultraviolet radiation streaming from newly-formed stars ionises the surrounding hydrogen gas, causing it to emit a faint pinkish glow. By catching new stars “pink-handed” in this manner, astronomers can learn more about the conditions under which stars arise, and study how they influence their cosmic environment.

This image was created as part of the ESO Cosmic Gems programme, an outreach initiative to produce images of interesting, intriguing or visually attractive objects using ESO telescopes, for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations. All data collected may also be suitable for scientific purposes, and are made available to astronomers through ESO’s science archive.

Susanna Kohler wrote:

Magnetic Fields in NGC 1068 ~ SOFIA/HAWC+/E. Lopez-Rodriguez et al

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This cryptic image is the (false-color) view of a large spiral galaxy, NGC 1068, at the far-infrared wavelength of 89 μm (click for the full view). The tiny hairs threading the galaxy show the magnetic field lines — ordinarily invisible — that pervade interstellar space. This magnetic field has been imaged using the HAWC+ instrument on SOFIA, a telescope that points out of a Boeing 747 airplane, observing above 99% of the Earth’s infrared-blocking atmosphere. HAWC+ has captured not only the infrared flux of the thermally emitting dust in NGC 1068, but also the polarization of the dust, which tells us what direction the magnetic field points at each location. By piecing this information together, a team led by Enrique Lopez-Rodriguez (SOFIA Science Center) has determined the overall structure of NGC 1068’s magnetic field, finding that it closely traces all the way along the spiral arms of the galaxy (24,000 light-years across!).

• Astrophysical Journal 888(2):66 (2020 Jan 10) DOI: 10.3847/1538-4357/ab5849
• arXiv.org > astro-ph > arXiv:1907.06648 > 15 Jul 2019 (v1), 15 Nov 2019 (v2)