A Spiral Within a Spiral
The NASA/ESA Hubble Space Telescope captured this image of the spiral galaxy known as ESO 498-G5. One interesting feature of this galaxy is that its spiral arms wind all the way into the centre, so that ESO 498-G5’s core looks like a bit like a miniature spiral galaxy. This sort of structure is in contrast to the elliptical star-filled centres (or bulges) of many other spiral galaxies, which instead appear as glowing masses, as in the case of NGC 6384.
Astronomers refer to the distinctive spiral-like bulge of galaxies such as ESO 498-G5 as disc-type bulges, or pseudobulges, while bright elliptical centres are called classical bulges. Observations from the Hubble Space Telescope, which does not have to contend with the distorting effects of Earth’s atmosphere, have helped to reveal that these two different types of galactic centres exist. These observations have also shown that star formation is still going on in disc-type bulges and has ceased in classical bulges. This means that galaxies can be a bit like Russian matryoshka dolls: classical bulges look much like a miniature version of an elliptical galaxy, embedded in the centre of a spiral, while disc-type bulges look like a second, smaller spiral galaxy located at the heart of the first — a spiral within a spiral.
The similarities between types of galaxy bulge and types of galaxy go beyond their appearance. Just like giant elliptical galaxies, the classical bulges consist of great swarms of stars moving about in random orbits. Conversely, the structure and movement of stars within disc-type bulges mirror the spiral arms arrayed in a galaxy’s disc. These differences suggest different origins for the two types of bulges: while classical bulges are thought to develop through major events, such as mergers with other galaxies, disc-type bulges evolve gradually, developing their spiral pattern as stars and gas migrate to the galaxy’s centre.
ESO 498-G5 is located around 100 million light-years away in the constellation of Pyxis (The Compass). This image is made up of exposures in visible and infrared light taken by Hubble’s Advanced Camera for Surveys. The field of view is approximately 3.3 by 1.6 arcminutes.
Credit:
ESA/Hubble & NASA
Source: spacetelescope.org
Sky at Night Magazine Vodcast Episode 33 — Meeting MIRI (by bbcskyatnightmag)
In this episode Will Gater travels to the Rutherford Appleton Laboratory in Oxfordshire to meet MIRI, one of the instruments which will fly on board the James Webb Space Telescope, and speak to some of the scientists involved with the project.
Source: youtube.com
Edge-on Beauty
Visible in the constellation of Andromeda, NGC 891 is located approximately 30 million light-years away from Earth. The NASA/ESA Hubble Space Telescope turned its powerful wide field Advanced Camera for Surveys towards this spiral galaxy and took this close-up of its northern half. The galaxy’s central bulge is just out of the image on the bottom left.
The galaxy, spanning some 100 000 light-years, is seen exactly edge-on, and reveals its thick plane of dust and interstellar gas. While initially thought to look like our own Milky Way if seen from the side, more detailed surveys revealed the existence of filaments of dust and gas escaping the plane of the galaxy into the halo over hundreds of light-years. They can be clearly seen here against the bright background of the galaxy halo, expanding into space from the disc of the galaxy.
Astronomers believe these filaments to be the result of the ejection of material due to supernovae or intense stellar formation activity. By lighting up when they are born, or exploding when they die, stars cause powerful winds that can blow dust and gas over hundreds of light-years in space.
A few foreground stars from the Milky Way shine brightly in the image, while distant elliptical galaxies can be seen in the lower right of the image.
NGC 891 is part of a small group of galaxies bound together by gravity.
A version of this image was entered into the Hubble’s Hidden Treasures Image Processing Competition by contestant Nick Rose. Hidden Treasures is an initiative to invite astronomy enthusiasts to search the Hubble archive for stunning images that have never been seen by the general public.
Credit:
ESA/Hubble & NASA
Acknowledgement: Nick Rose
Source: spacetelescope.org
ESOcast 43 Special: Seeing Sharp — Special 50th anniversary episode #3 (by ESOobservatory)
The third special episode of this series — ESOcast 43 overall — presents ESO’s flagship facility: the Very Large Telescope (VLT). In this episode we discover the state-of-the-art technology behind this telescope, which has provided astronomers with an unequalled view of the Universe.
More information and full credits:http://www.eso.org/public/videos/esocast43a/
Source: youtube.com
Black-Hole Hunter (by JPLnews)
NASA’s NuSTAR will use its X-ray eyes to scout for hidden black holes in the universe.
Source: youtube.com
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This blog is mostly about space... and other things.
