The Kepler Space Telescope’s Supernova Surprise

Supernovae are stellar blasts that herald the deaths of stars, and they can be so bright that they may briefly out-dazzle their complete great number galaxy. A particular class of supernovae, called kind Ia, proved to be a basic tool in the important discovery of the dark energy–a mysterious force that is causing the Universe to accelerate in its expansion, and consists of the lion’s proportion of the mass-energy part of the Cosmos. Nevertheless, the time of action that triggers kind Ia supernovae conflagrations has remained a question of Cosmic dimensions. However, astronomers announced at the January 2014 winter meeting of the American Astronomical Society (AAS), held outside of Washington D.C. in National shelter, Maryland, that NASA’s ill-fated, but nevertheless highly successful, planet-hunting Kepler Space Telescope had succeeded in the surprising discovery of two kind Ia supernovae explosions, that discarded captivating light on their mysterious origins.

The Kepler mission was the first space telescope to be launched that was capable of detecting Earth-size exoplanets in our Galactic neighborhood located in their stars’ habitable zones. Over 75% of the 3,500 exoplanet candidates spotted by Kepler sport sizes ranging from that of Earth to that of Neptune.

The habitable zone around a star is that “just right” Goldilocks vicinity where water, in its life-loving liquid state, can exist on an revolving world. Where liquid water exists, life as we know it can also evolve! This does not average that life definitely exists on such a happy watery world–but it does average that the possibility is there.

Kepler, launched on March 7, 2009, from Cape Canaveral, Florida had, as its dominant mission, the task of staring at more than 100,000 stars, hunting for small dips in their brightnesses caused by transiting planets. Kepler, a special-purpose spacecraft, was designed to precisely measure these tiny alterations of the light of those distant stars, in search of alien planets causing subtle dips in their bright, fiery light.

For all four years of its mission, Kepler stared relentlessly at a single patch of sky, gathering brightness measurements every half hour. Sometimes the telescope fortuitously spotted tiny dips in a star’s brightness, suggesting that planets had made a transit–that is, passed in front of–the glaring confront of a parent-star. Unfortunately, the Kepler mission came to a premature end when a piece of its equipment failed in May 2013.

In late 2009, Dr. Robert Olling, an astronomer at the University of Maryland in College Park, began to think about what Kepler might be able to do if it also turned to stare at galaxies. Dr. Olling, who studies supernovae and black holes, realized that, like stars, galaxies sparkle with comparatively consistent brightnesses. However, in the event of some uncommon occurrence–such as the feeding frenzy of a voracious black hole, or the fatal explosion of a giant star–a galaxy’s radiance could greatly strengthen. After Dr. Olling and two of his colleagues, Dr. Richard Mushotsky and Dr. Edward Shaya, also of the University of Maryland, submitted a proposal to the Kepler team, the telescope began staring at 400 galaxies dancing around in its field of view.

What A Blast!

Most supernovae blast off when a lone, lonely star explodes and “dies”. Frequently, the supernova progenitor is a heavy star, with a enormous chief weighing-in at about 1.4 solar-masses. This is what is called the Chandrasekhar limit. Smaller, less weighty stars–like our own Sun–usually do not perish in the bright violence of explosive supernovae blasts, like their more enormous stellar kin. Small stars, like our Sun, go much more “gentle into that good night”, and perish in relative peace–and great beauty. Our Sun, at this point in time, is a very ordinary and rather petite (by stellar-standards), main-ordern (hydrogen-burning) star. It appears in our daytime sky as a large, enchanting, brilliantly sparkling golden sphere. There are eight major planets, a multitude of bewitching moons, and a high assortment of other, smaller bodies in orbit around our Sun, which dwells happily in the far suburbs of a large, majestic, barred-spiral Galaxy, our Milky Way. Our Sun will not live forever. Like all stars, it is doomed to perish, at some point–but, in our Sun’s case, not for a very long time. A star, of our Sun’s comparatively small mass, can “live” for about 10 billion years, blissfully fusing the hydrogen of its chief into heavier atomic elements, in a course of action termed stellar nucleosynthesis.

However, our Sun is not currently a bouncing stellar baby. In fact, it is a middle-aged star. However, it is experiencing an active mid-life, and is nevertheless exuberant enough to go on merrily fusing hydrogen in its chief for another 5 billion years, or so. Our Sun is currently about 4.56 billion years old–it is not young by star-standards, but it isn’t exactly old, either.

When stars like our Sun have at long last managed to fuse most of their supply of hydrogen, they begin to grow into glowering, swollen red giant stars. The now-elderly Sun-like star produces a heart of helium, surrounded by a shell in which hydrogen is nevertheless being fused into helium. The shell puffs itself up outward, and the star’s dying heart grows ever larger, as the star grows older. Then the helium heart itself begins to shrivel up under its own weight, and it becomes ever hotter and hotter until, at last, it has become so searing-hot at its center that the helium is now fused into the nevertheless-heavier atomic component, carbon. The Sun-like, small star ends up with a small, extremely hot heart that churns out more energy than it did, long ago, when it was a younger main-ordern star. The outer layers of the elderly, dying star have puffed up to hideous dimensions. In our own Solar System, when our Sun has finally gone Red Giant, it will cannibalize some of its own planetary-children–first Mercury, then Venus–and then (perhaps), the Earth. The temperature at the flaming surface of this ghastly Red Giant will be considerably cooler than it was when our Sun was nevertheless an enchanting, young, vibrant main-ordern tiny, tiny Star!

The comparatively gentle deaths of small stars, like our Sun, are characterized by the tender puffing off of their outer layers of luminous, multi-colored gases, and these objects are so stunningly beautiful that they are frequently called the “butterflies of the Cosmos,” by enchanted astronomers.

Our Sun will die this way–with comparative peace, and great beauty. That is because our Sun is a loner. The Sun’s corpse will be a small, thick stellar remnant called a white dwarf, and its shroud will be a shimmering Cosmic “butterfly”.

However, something very different happens when a small solar-kind star dwells in a binary system with another sister star. The sister star rudely interferes with its sibling’s precious, peaceful solitude, and in this case the dying small star goes supernova–just like its more enormous starry kin, when they reach the end of the stellar road.

Supernova Surprise!

Kepler data revealed at the minimum five–and possibly eight–supernovae over a two year period. at the minimum two of them were identified as kind Ia, and their light was captured in greater time related detail than ever before. This new information adds credibility to the theory that kind Ia supernovae consequence from the merger of two white dwarfs–the Earth-sized, extremely thick relics of Sun-like stars. This new discovery casts doubt on the older, longstanding form that kind Ia supernovae are the consequence of a lone white dwarf sipping up material from a companion sister star–and victim. The companion star could be either a main-ordern Sun-like star, or an elderly, bloated red giant.

This new information was the surprising discovery of Kepler–whose main purpose was to hunt for alien planets by staring at stars in our Galactic neighborhood. far away galaxies also danced around in the space telescope’s field of view, and its success in gathering data every half hour, along with its sensitivity to very small alterations in brightness, made it ideal for recording the rise and fall of light sent forth during supernovae blasts.

Dr. Olling was fortunate enough to identify the duo of kind Ia supernovae after a two-year study of some 400 galaxies in Kepler’s field. He reported his discovery on January 8, 2014, at the winter meeting of the AAS. “As a technical tour de force, it’s really cool to use Kepler for more than it was intended,” Dr. Robert P. Kirshner told the press at the AAS meeting. Dr. Kirshner is an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.

In certain ways the data gathered are rudimentary. This is because they are composed only of the brightness measurements, so astronomers cannot calculate details like the two structures of the duo of kind Ia blasts, and the chemical composition of what they hurled violently into Space. Kepler also dispatched data back to Earth only once every three months. Because supernovae faint after several weeks of radiance, astronomers were unable to point other telescopes at the supernovae that Kepler had spotted in order to gather more-perfect observations.

kind Ia explosions are the most commonly observed form of supernovae. Kepler’s data provided a precious clue as to what triggers these stellar blasts. The Kepler data helps astronomers to discriminate between the two competing supernovae scenarios. Both require that a white dwarf accumulates star-stuff from a companion, until the pressure sparks a runaway thermonuclear blast. However, in the companion form, the expanding shell of material from the white dwarf would crash into the sister star. This would churn out additional heat and light–that would show up as a bump in the first days of a supernova’s brightening. However, no such bump was seen in Dr. Olling’s data.

This essentially rules out red giant companions, Dr. Olling explained at the AAS meeting, because these large, bloated, elderly stars would cause a nice big bump. However, the data might nevertheless be compatible with the form of smaller, more Sun-like companions, noted Dr. Daniel Kassen to the press on January 14, 2014. Dr. Kassen is an astronomer at the University of California, Berkeley, and a collaborator with Dr. Olling on the survey. Not only would these comparatively small stars cause a tinier bump, but the bump could well be overlooked completely depending on the observer’s viewpoint, Dr. Kassen continued to explain.

For a long time, the form of kind Ia supernovae being caused by merging white dwarfs was not particularly popular among astronomers because the end stages of the mergers were believed to occur very slowly–over the span of thousands of years. Such a gradual accretion of material would more likely rule to the creation of a neutron star. However, in 2010, simulations suggested that such mergers could occur much more rapidly–within seconds or minutes, and this would allow for the emotional, sudden pressure alteration that triggers such a blast.

There may be some problems, however, with the merger scenario. Dr. Craig Wheeler noted in the January 14, 2014 issue of character News that simulations of the mergers frequently show highly asymmetric explosions–in addition observations so far appear to be more spherical. Dr. Wheeler is a supernova theorist at the University of Texas at Austin.

Dr. Olling believes that it is important to make at the same time observations using ground-based ‘scopes. This is because Kepler can only record brightness and cannot divided light into spectra. However, in order to do this, Kepler needs to be pointed in the opposite direction. Dr. Olling hopes that the Kepler team will permit this when NASA discloses its future plans for the crippled spacecraft during the summer of 2014.

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