How supernovae became the basis of observational cosmology

Supernova classification

Supernova classification

Maria Victorovna Pruzhinskaya, Sergey Mikhailovich Lisakov
This paper is dedicated to the discovery of one of the most important relationships in supernova cosmology – the relation between the peak luminosity of Type Ia supernovae and their luminosity decline rate after maximum light.
The history of this relationship is quite long and interesting. The relationship was independently discovered by the American statistician and astronomer Bert Woodard Rust and the Soviet astronomer Yury Pavlovich Pskovskii in the 1970s.
Using a limited sample of Type I supernovae they were able to show that the brighter the supernova is, the slower its luminosity declines after maximum.
Only with the appearance of CCD cameras could Mark Phillips re-inspect this relationship on a new level of accuracy using a better sample of supernovae. His investigations confirmed the idea proposed earlier by Rust and Pskovskii.

Appearances of the Refsdal supernova

This video shows the three appearances of the Refsdal supernova in the galaxy cluster MACS J1149.5+2223. Calculations showed that the first image of the supernova appeared in 1998 — an event not observed with a telescope. The second image produced an almost perfect Einstein Cross, which was observed in November 2014 (heic1505). The latest appearance was observed by the NASA/ESA Hubble Space telescope on 11 December 2015, as correctly predicted by seven different models.
The positions of all three events are highlighted in this video with animated supernovae, even though the Einstein Cross event is also visible in the original image.


Type 1a Supernova Animation

Animation showing a binary star system in which a white dwarf accretes matter from a normal companion star. Matter streaming from the red star accumulates on the white dwarf until the dwarf explodes. With its partner destroyed, the normal star careens into space. This scenario results in what astronomers refer to as a Type Ia supernova.
Read also: NASA Spacecraft Capture Rare, Early Moments of Baby Supernovae

Magnetorotational Core-Collapse Supernovae

… in Three Dimensions (xz-slice)

This movie shows the time-evolution of the shock wave that is created when the core of a rapidly rotating, strongly magnetized massive star collapses to a proto-neutron star. The dynamics are dominated by the ultra-strong magnetic field (~10^16G) that is build up during and shortly after the collapse. A prompt jet-like explosion is foiled by a spiraling MHD kink instability that disrupts the jet. Subsequently magnetic fields continue to dominate as funnels of highly magnetized, launched from the proto-neutron star, advance the shock front outwards in a highly asymmetric fashion. The different colors correspond to gas of different temperature (the variable shown is “specific entropy”, which is closely related to temperature). Blue corresponds to the coldest gas, green is hotter gas, and yellow and red are the hottest gas. The movie depicts a 2D simulation on the left, and the corresponding meridional slice from a 3D simulation on the right.

This movie was generated by the Simulating eXtreme Spacetimes (SXS) project. The simulation work was led by Philipp Moesta at Caltech and the movie was rendered by Sherwood Richers, also at Caltech.

Read also: To Supernova or Not to Supernova: A 3-D Model of Stellar Core Collapse 

Detection of the Gravitational Lens Magnifying a Type Ia Supernova

supernovaAn exceptionally bright supernova that baffled scientists has been explained.

It is so luminous because a galaxy sitting in front amplifies its light – making it appear 100 billion times more dazzling than our Sun.

This cosmic magnifying glass lay hidden between Earth and the supernova – and has now been detected with a telescope in Hawaii.

The discovery, reported in the journal Science, settles an important controversy in the field of astronomy…

How Much Is a Supernova Worth?

If I had a nickel for every nickel you could make from the nickel in supernova SN1999em, I’d be very, very, VERY rich.

If I were you, dear BABloggee, I’d be thinking, “What the what?” So let me explain. Well, let me explain in a minute. First, I want to introduce you to the gorgeous but somewhat lopsided spiral galaxy NGC 1637, care of the Very Large Telescope in Chile:

Very Large Telescope image of the spiral galaxy NGC 1637

Very Large Telescope image of the spiral galaxy NGC 1637

NGC 1637 is a decent-size spiral galaxy about 26 million light years away. That’s pretty close for a galaxy, roughly equivalent to being down the block in our galactic neighborhood. As you can see, it’s noticeably asymmetric—lopsided—with the arm to the upper left a lot longer than its counterpart on the other side. This kind of thing is fairly common, occurring in about a third of all spiral galaxies. It’s even more common when the galaxy is part of a cluster of galaxies, so it’s probably due to gravitational interactions with other galaxies as they pass close by………

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Mysterious star deaths are really mergers in disguise

A stellar merger and acquisition (Image: NASA/ESA/H. Bond/STSCI)

A stellar merger and acquisition (Image: NASA/ESA/H. Bond/STSCI)

by Stuart Clark
SOAP operas have nothing on supernovae. A charlatan star that appeared to explode earlier this year may have faked its own death to unite with a secret companion.

If so, it joins a growing cast of oddball stars suspected to be the products of stellar mergers, which have the potential to change our understanding of the universe’s chemical make-up.

Stars are powered by nuclear fusion, converting hydrogen into helium in their cores. When very massive stars run out of hydrogen fuel, they start fusing heavier elements until their cores collapse and they explode. These types of exploding stars, or supernovae, scatter the elements that go on to make new cosmic bodies.

Because most of these stars detonate when they hit a set mass limit, their behaviour is fairly predictable, but occasionally we see a dying star go off the rails. Such was the case with SN 2009ip, which flared up and died down for three years before finally seen going supernova in September.

But Noam Soker of the Technion-Israel Institute of Technology in Haifa challenges the supernova interpretation of the outburst. Based on observations, he calculates that SN 2009ip generated less than 10 per cent of the kinetic energy of a typical star explosion ( “The more we look at it, the stranger its behaviour for a supernova,” he says.

Instead, Soker and Amit Kashi of the University of Nevada in Las Vegas argue that the outburst has more in common with V838 Monocerotis, another flaring star now thought to be the result of a merger, shown right. They think the early outbursts from SN 2009ip were caused by two large stars brushing against each other. When they merged in September, they created a new star between 100 and 120 times the mass of the sun.

Gijs Nelemans of Radboud University Nijmegen in the Netherlands says astronomers are starting to realise how common star mergers must be. “We now know there is an extraordinary diversity of strange, transient objects,” he says, referring to the hundreds of fleeting celestial flare-ups that appear beyond the solar system each year. They can’t all be supernovae, says Nelemans, because of their widely different durations and brightnesses.

There’s still much work to be done to understand how many stars merge and their impact on the universe’s composition. Not all stars may survive the merger process, and some of those that do probably don’t live for long. “We must attempt a more systematic observation of merger stars throughout the galaxy,” says Nelemans.

As for SN 2009ip, Soker and others will be watching closely for any distinctive elements that are only created in star explosions. “If we see evidence of radioactive cobalt, then it was a supernova and we can rule out the merger,” he says.
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Hubble Spotted a Supernova in NGC 5806

A new image from the NASA/ESA Hubble Space Telescope shows NGC 5806, a spiral galaxy in the constellation Virgo (the Virgin). It lies around 80 million light years from Earth. Also visible in this image is a supernova explosion called SN 2004dg.

The exposures that are combined into this image were carried out in early 2005 in order to help pinpoint the location of the supernova, which exploded in 2004. The afterglow from this outburst of light, caused by a giant star exploding at the end of its life, can be seen as a faint yellowish dot near the bottom of the galaxy.

NGC 5806 was chosen to be one of a number of galaxies in a study into supernovae because Hubble’s archive already contained high resolution imagery of the galaxy, collected before the star had exploded. Since supernovae are both relatively rare, and impossible to predict with any accuracy, the existence of such before-and-after images is precious for astronomers who study these violent events.

Aside from the supernova, NGC 5806 is a relatively unremarkable galaxy: it is neither particularly large or small, nor especially close or distant.

The galaxy’s bulge (the densest part in the center of the spiral arms) is a so-called disk-type bulge, in which the spiral structure extends right to the center of the galaxy, instead of there being a large elliptical bulge of stars present. It is also home to an active galaxy nucleus, a supermassive black hole which is pulling in large amounts of matter from its immediate surroundings. As the matter spirals around the black hole, it heats up and emits powerful radiation.

This image is produced from three exposures in visible and infrared light, observed by Hubble’s Advanced Camera for Surveys. The field of view is approximately 3.3 by 1.7 arcminutes.

A version of this image was entered into the Hubble’s Hidden Treasures Image Processing Competition by contestant Andre van der Hoeven (who won second prize in the competition for his image of Messier 77). 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. The competition has now closed.
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