Starship Asterisk*

Image Credits: ESO/Inserra et al., Amram et al.

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Around 500 million light-years away in the constellation Sculptor lies a rather peculiar looking galaxy, known as the Cartwheel galaxy. It was once a normal spiral galaxy that underwent a head-on interaction with a smaller companion galaxy several million years ago, giving it its signature cartwheel appearance. But there are other curious things about this object. Something interesting is taking place in the lower left corner of the right image, captured in December 2021 with ESO’s New Technology Telescope (NTT): a supernova. The image on the left, taken in August 2014 by the Multi Unit Spectroscopic Explorer (MUSE) mounted on ESO’s Very Large Telescope (VLT), shows the galaxy before this supernova took place.

This event, called SN2021afdx, is a type II supernova, which occurs when a massive star reaches the end of its evolution. Supernovae can cause a star to shine brighter than its entire host galaxy and can be visible to observers for months, or even years — a blink of an eye on astronomical timescales. Supernovae are one of the reasons astronomers say we are all made of stardust: they sprinkle the surrounding space with heavy elements forged by the progenitor star, which may end up being part of later generations of stars, the planets around them and life that may exist in those planets.

Detecting and studying these unpredictable events requires international collaboration. The first time SN2021afdx was spotted was in November 2021 by the ATLAS survey, and it was then followed up by ePESSTO+, the advanced Public ESO Spectroscopic Survey for Transient Objects. ePESSTO+ is designed to study objects that are only in the night sky for very short periods of time, such as this supernova. It does this by using the EFOSC2 and SOFI instruments on the NTT, located at ESO's La Silla Observatory in Chile. EFOSC2 not only took this beautiful image, but also spectra that allowed the PESSTO team to identify this event as a type II supernova.

Image Credit: ESA/Hubble & NASA, B. Nisini

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An energetic outburst from an infant star streaks across this image from the NASA/ESA Hubble Space Telescope. This stellar tantrum — produced by an extremely young star in the earliest phase of formation — consists of an incandescent jet of gas travelling at supersonic speeds. As the jet collides with material surrounding the still-forming star, the shock heats this material and causes it to glow. The result is the colourfully wispy structures, which astronomers refer to as Herbig–Haro objects, billowing across the lower left of this image.

Herbig–Haro objects are seen to evolve and change significantly over just a few years. This particular object, called HH34, was previously captured by Hubble between 1994 and 2007, and again in glorious detail in 2015. HH34 resides approximately 1250 light-years from Earth in the Orion Nebula, a large region of star formation visible to the unaided eye. The Orion Nebula is one of the closest sites of widespread star formation to Earth, and as such has been pored over by astronomers in search of insights into how stars and planetary systems are born.

The data in this image are from a set of Hubble observations of four nearby bright jets with the Wide Field Camera 3 taken to help pave the way for future science with the NASA/ESA/CSA James Webb Space Telescope. Webb — which will observe at predominantly infrared wavelengths — will be able to peer into the dusty envelopes surrounding still-forming protostars, revolutionising the study of jets from these young stars. Hubble’s high-resolution images of HH34 and other jets will help astronomers interpret future observations with Webb.

Image Credits: Data: Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA; Processing: T.A. Rector (University of Alaska Anchorage/NSF’s NOIRLab), J. Miller (Gemini Observatory/NSF’s NOIRLab), M. Zamani & D. de Martin (NSF’s NOIRLab)

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This Image of the Week features a sky speckled with stars and galaxies. The most prominent galaxy, in the upper right quadrant of the image, is known as NGC 1703. It was observed using the Dark Energy Camera (DECam), a high-performance camera installed by the US Department of Energy at the Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO), a Program of NSF’s NOIRLab. NGC 1703 lies in a region of the sky that constitutes the constellation Dorado, the dolphinfish. You may know this fish by its Hawaiian name, mahi-mahi. The constellation was named Dorado back in the 16th century and the name was made official in the early 20th century. It is one of the 88 astronomical constellations recognized by the International Astronomical Union. So NGC 1703 could fancifully be thought of as one of the Dorado’s more impressive scales. Use the interactive zoom tool to explore the thousands of background galaxies, each with billions of stars like our Sun.

starsurfer wrote: ↑Sun Mar 13, 2022 11:14 pm IC 5052
https://members.pcug.org.au/~stevec/ic5 ... 3_RC14.htm
Copyright: Steve Crouch

Click to view full size image

Image Credit: ESO/PHANGS

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This image features the spectacular galaxy NGC 4254, also known as Messier 99. It’s an example of a grand design spiral galaxy, featuring strong, prominent, well-defined arms that wrap clearly around the galaxy’s centre.

Messier 99 is located 49 million light-years from Earth in the constellation of Coma Berenices. Here it was imaged in exquisite detail by the Multi-Unit Spectroscopic Explorer (MUSE) on ESO’s Very Large Telescope (VLT). It is a combination of observations conducted in different colours, or wavelengths, of light, showing clouds of gas ionised by newly born stars. Hydrogen, oxygen and sulphur gas are shown in red, blue and orange respectively.

The image was taken as part of the Physics at High Angular resolution in Nearby GalaxieS (PHANGS) project, which is making high-resolution observations of nearby galaxies across all wavelengths of the electromagnetic spectrum to understand the life-cycle of star formation in galaxies.

Image Credit: ESA/Hubble & NASA, D. Sand, K. Sheth

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This finely detailed image shows the heart of NGC 1097, a barred spiral galaxy that lies about 48 million light-years from Earth in the constellation Fornax. This picture reveals the intricacy of the web of stars and dust at NGC 1097’s centre, with the long tendrils of dust picked out in a dark red hue. The extent to which the galaxy’s structure is revealed is thanks to two instruments on the NASA/ESA Hubble Space Telescope: the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS).

The idea that a single image can be taken using two different cameras is not very intuitive. However, it makes far more sense after delving into how beautiful astronomical images like this one are composed. A helpful starting point is to consider what colour is, exactly. Our eyes can detect light waves at optical wavelengths between roughly 380 and 750 nanometres, using three types of receptors, each of which is sensitive to just a slice of that range. Our brain interprets these specific wavelengths as colours. By contrast, a telescope camera like the WFC3 or ACS is sensitive to a single, broad range of wavelengths to maximise the amount of light collected. Raw images from telescopes are always in greyscale, only showing the amount of the light captured across all those wavelengths.

Colour images from telescopes are indirectly possible, however, with the help of filters. By sliding a filter over the aperture of an instrument like the WFC3 or ACS, only light from a very specific wavelength range is let through — one such filter used in this image is for green light around 555 nanometres. This yields a greyscale image showing only the amount of light with that wavelength. This multicolour image of NGC 1097 is composed of images using seven different filters in total.

Ann wrote: ↑Mon Mar 14, 2022 5:27 am

starsurfer wrote: ↑Sun Mar 13, 2022 11:14 pm IC 5052
https://members.pcug.org.au/~stevec/ic5 ... 3_RC14.htm
Copyright: Steve Crouch

Click to view full size image

That intensely blue-white star smack dab in the middle of a central dust lane inside the galaxy sure looks like a supernova.

Ann