Tag: supernovae

Movies of two supernovae remnants produced from two decades of Chandra X-ray images

9:51 am

Using more than two decades of data from the Chandra X-ray Observatory, scientists have created two movies of the supernovae remnants the Crab nebula and Cassiopeia A.

I have embedded those movies below. From the press release:

Over 22 years, Chandra has taken many observations of the Crab Nebula. With this long runtime, astronomers see clear changes in both the ring and the jets in the new movie. Previous Chandra movies showed images taken from much shorter time periods — a 5-month period between 2000 and 2001 and over 7 months between 2010 and 2011 for another. The longer timeframe highlights mesmerizing fluctuations, including whip-like variations in the X-ray jet that are only seen in this much longer movie. A new set of Chandra observations will be conducted later this year to follow changes in the jet since the last Chandra data was obtained in early 2022.

…Cassiopeia A (Cas A for short) is the remains of a supernova that is estimated to have exploded about 340 years ago in Earth’s sky. While other Chandra movies of Cas A have previously been released, including one with data extending from 2000 to 2013, this new movie is substantially longer featuring data from 2000 through to 2019.

» Read more

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Webb: Infrared data sees neutron star remaining after 1987 supernova, the nearest in more than 4 centuries

9:29 am

Webb's infrared view of Supernova 1987a
Click for original image.

Using the Webb Space Telescope, astronomers have obtained infrared data that confirms the existence of a neutron star at the location of Supernova 1987a, located in the Large Magellanic Cloud, the nearest such supernova in more than four centuries and the only one visible to the naked eye since the invention of the telescope.

Indirect evidence for the presence of a neutron star at the center of the remnant has been found in the past few years, and observations of much older supernova remnants — such as the Crab Nebula — confirm that neutron stars are found in many supernova remnants. However, no direct evidence of a neutron star in the aftermath of SN 1987A (or any other such recent supernova explosion) had been observed, until now.

…Spectral analysis of the [Webb] results showed a strong signal due to ionized argon from the center of the ejected material that surrounds the original site of SN 1987A. Subsequent observations using Webb’s NIRSpec (Near-Infrared Spectrograph) IFU at shorter wavelengths found even more heavily ionized chemical elements, particularly five times ionized argon (meaning argon atoms that have lost five of their 18 electrons). Such ions require highly energetic photons to form, and those photons have to come from somewhere.

That “somewhere” has to be a neutron star, based on present theories. The image above shows three different Webb views of Supernova 1987a, with the one on the lower right suggesting the existence of a point source at the center of the supernova remnant. In the left image the circular ring of bright spots is an older ring of dust and material that has been lit up by the crash of the explosive material (as indicated in blue at the center) flung out from the star when it went supernova and collapsed into a neutron star. That wave of explosive material took several decades to reach the ring and enflame it.

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Scientists: More evidence cosmic rays come from nearby supernova remnants

9:07 am

The uncertainty of science: According to high energy data from an instrument on ISS, astronomers found more evidence that the cosmic rays that enter our solar system likely come from nearby supernova remnants.

Current theory posits that the aftermath of supernovae (exploding stars), called supernova remnants, produce these high energy electrons, which are a specific type of cosmic ray. Electrons lose energy very quickly after leaving their source, so the rare electrons arriving at CALET with high energy are believed to originate in supernova remnants that are relatively nearby (on a cosmic scale), Cannady explains.

The study’s results are “a strong indicator that the paradigm that we have for understanding these high-energy electrons—that they come from supernova remnants and that they are accelerated the way that we think they are—is correct,” Cannady says. The findings “give insight into what’s going on in these supernova remnants, and offer a way to understand the galaxy and these sources in the galaxy better.”

The results however do not prove this. Nor do they eliminate the possibility that cosmic rays might also come from other sources outside our galaxy. At present the data is simply too uncertain.

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Update on the ongoing research of the closest supernovae in a decade

12:47 pm

Gemini North image of supernova in Pinwheel Galaxy
Click for original image, taken by the Gemini North telescope in Hawaii.

Link here. Though the press release from UC-Berkeley focuses mostly of research being done by its astronomers, it also provides a very good overview of what all astronomers worldwide have been learning since Supernova SN 2023ixf was first discovered by amateur astronomer Koichi Itagaki in Japan on May 19, 2023 in the Pinwheel Galaxy, only 20 million light years away. This tidbit is probably the most significant:

Another group of astronomers led by Ryan Chornock, a UC Berkeley adjunct associate professor of astronomy, gathered spectroscopic data using the same telescope at Lick Observatory. Graduate student Wynn Jacobson-Galán and professor Raffaella Margutti analyzed the data to reconstruct the pre- and post-explosion history of the star, and found evidence that it had shed gas for the previous three to six years before collapsing and exploding. The amount of gas shed or ejected before the explosion could have been 5% of its total mass — enough to create a dense cloud of material through which the supernova ejecta had to plow.

Such data is going to help astronomers better predict when a star is about to go boom, by identifying similar behavior.

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More evidence found suggesting supernovae occurred near the solar system during its formation

9:22 am

Scientists have now detected more evidence that suggests a supernovae occurred very close to our solar system during its early period of formation.

Astronomers have for decades found such evidence inside meteorites. Small spherical inclusions called chondrules are thought by some to have formed when the heat of a nearby supernova caused melting. The new study finds more evidence in isotopes also found in primitive meteorites dubbed short-lived radionuclides (SLRs).

While SLRs probably existed in the part of the filament where the Sun and Solar System formed, the meteorite samples contained too much of a particular aluminum isotope for the interstellar medium to have been the Solar System’s only SLR source. Cosmic rays, which can convert stable isotopes to radioactive ones, had a better chance of explaining the number of isotopes found in the meteorites. However, it would have taken too long for this process to produce the levels of SLRs found in the early Solar System.

It is most likely that such high SLR levels could have come from either very intense stellar winds, which would have occurred during massive star formation, or from what was left after one of the massive stars went supernova.

You can read the published paper here.

If true, this data adds weight to the possibility that our solar system is somewhat unique, which in turn suggests finding just another like it — with life — might be difficult.

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A spiral galaxy as seen by Hubble

9:40 am

A spiral galaxy as seen by Hubble
Click for original image.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was taken as part of a research project to use the Hubble Space Telescope to photograph galaxies where supernovae had recently occurred. From the caption:

UGC 11860 lies around 184 million light-years away in the constellation Pegasus, and its untroubled appearance can be deceiving; this galaxy recently played host to an almost unimaginably energetic stellar explosion.

A supernova explosion — the catastrophically violent end of a massive star’s life — was detected in UGC 11860 in 2014 by a robotic telescope dedicated to scouring the skies for transient astronomical phenomena; astronomical objects which are only visible for a short period of time. Two different teams of astronomers used Hubble’s Wide Field Camera 3 to search through the aftermath and unpick the lingering remnants of this vast cosmic explosion.

This Hubble image once again illustrates the vastness of the universe. Note that every single dot surrounding UGC 11860 in this picture is another far more distant galaxy. As much as UGC 11860 is in our local intergalactic neighborhood, it is still so distant that this field of view is small enough that it contains no stars.

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A faint irregular cloud of stars

9:06 am

A faint irregular cloud of stars
Click for original picture.

Cool image time! The picture to the right, cropped, reduced, and sharpened to post here, was released today by the science team of the Hubble Space Telescope. It shows an irregular galaxy thought to be about 44 million light years away.

Alongside its hazy shape, NGC 7292 is remarkably faint. As a result, astronomers classify NGC 7292 as a low surface brightness galaxy, barely distinguishable against the backdrop of the night sky. Such galaxies are typically dominated by gas and dark matter rather than stars.

Astronomers directed Hubble to inspect NGC 7292 during an observational campaign studying the aftermath of Type II supernovae. These colossal explosions happen when a massive star collapses and then violently rebounds in a catastrophic explosion that tears the star apart. Astronomers hope to learn more about the diversity of Type II supernovae they have observed by scrutinising the aftermath and remaining nearby stars of a large sample of historical Type II supernovae.

NGC 7292’s supernova was observed in 1964 and accordingly given the identifier SN 1964H. Studying the stellar neighbourhood of SN 1964H helps astronomers estimate the initial mass of the star that went supernova, and could uncover surviving stellar companions that once shared a system with the star that would become SN 1964H.

I searched but was unable to locate any 1964 images of this galaxy when the supernova was still visible, so I could not pinpoint its location in the picture. It has long since faded away.

Note that the reddish smudges scattered throughout the picture are likely galaxies so far distant that their light has shifted entirely into the reddish spectrum. This likely places them one to several billions of light years away, not millions.

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Watch a still brightening new supernova only 20 million light years away

10:09 am

A new still brightening supernova has been discovered in the Pinwheel Galaxy, also known as Messier 101, only 20 million light years away, one of the closest such supernovae in years.

The discovery was made on May 19, 2023. Because the supernova is so close, it was discovered very early in its explosion and is still brightening to maximum. It is also an object that ordinary amateur astronomers can spot using their own telescopes. The Pinwheel Galaxy is located in the Big Dipper, making it a good target for amateurs in the northern hemisphere.

A live stream of the supernovae, dubbed SN 2023ixf, is also being broadcast today by the Virtual Telescope Project, and will be available here starting at 3 pm (Pacific).

No supernovae have occurred within our own galaxy, the Milky Way, since the invention of the telescope, so any such event in a nearby galaxy is an important opportunity for astronomers to learn more about these explosions.

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New research expands lethal zone around supernovae

9:58 am

According to data collected from a number of orbiting space X-ray telescopes, astronomers now believe that the lethal zone for nearby habitable planets when a supernova explodes is much larger than previously thought, as great as almost 200 light years.

The calculations in this latest study are based on X-ray observations of 31 supernovae and their aftermath mostly obtained from Chandra, NASA’s Swift and NuSTAR missions, and ESA’s (European Space Agency’s) XMM-Newton. The analysis of these observations shows that there can be lethal consequences from supernovae interacting with their surroundings, for planets located as much as about 160 light-years away. “If a torrent of X-rays sweeps over a nearby planet, the radiation would severely alter the planet’s atmospheric chemistry,” said Ian Brunton of the University of Illinois at Urbana-Champaign who led the study. “For an Earth-like planet, this process could wipe out a significant portion of ozone, which ultimately protects life from the dangerous ultraviolet radiation of its host star.”

You can read the paper here [pdf], which includes a figure that suggests in certain circumstances the lethal zone can be 200 light years across. As the scientists note:

Perhaps the most interesting results are the distances at which the X-ray emission can impose lethal effects on an Earth-like biosphere. This larger range of influence has consequences for the Galactic habitable zone, such as the harmful implications for recently discovered exoplanets that would be susceptible to nearby [supernovae].

In other words, this data suggests the galaxy is far less hospitable to the development of life. It takes a lot of time for life to evolve, billions of years, and during that time a solar system traveling through the galaxy has now a much higher chance of passing too close to a supernova explosion.

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Astronomers propose method for predicting the stars that will go supernovae

9:12 am

The uncertainty of science: Using a computer model based on the most recent data that suggests red supergiant stars like Betelgeuse are the kind of stars that produce certain kinds of supernovae, astronomers now think they have a method for predicting which of those stars are about to go supernovae.

You can read the science paper here. From the link above:

In a few examples, astronomers have looked back at old catalogs and found images of the stars before they exploded, and they all seem to be red supergiants like Betelgeuse. That’s a clear indication that those kinds of stars are supernova candidates, ready to go off at a moment’s notice.

The stars that result in these kinds of supernovas are thought to have dense shrouds of material surrounding them before they explode. These shrouds are orders of magnitude denser than what’s measured around Betelgeuse.

More importantly, the data suggests that once this shroud of material forms, the supernova will follow, in just a few years. As the scientists conclude in their paper:

The final overarching conclusion we can make from this work is that, shortly before core-collapse, [red supergiants] must undergo some prodigious mass-losing event which radically alters the appearance of the star. Therefore, the signature of an imminent explosion should be a dramatic change in the progenitor stars’ optical – near-IR photometry on timescales of less than a month. Such a signature should be detectable in the coming era of wide-field short cadence photometry. [emphasis mine]

Near-IR (infrared) photometry is exactly in the wavelengths in which the James Webb Space Telescope operates. Thus, if it is lucky and sees this kind of star in an image, and a supernova follows shortly thereafter, this theory will have been proven correct.

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Scientists: Plow the solar system through a dense-enough interstellar cloud and the heliosphere would no longer protect the Earth

11:20 am

The Earth's orbit outside the heliosphere

The uncertainty of science: Using a computer simulation, scientists have determined that if the solar system had two million years ago passed through one of the known nearby interstellar clouds within the relatively empty Local Bubble of space, it would have shrunk the Sun’s heliosphere enough so that the Earth would no longer be inside it, thus exposing the planet to interstellar space.

The image to the right comes from that simulation, and is figure 1 of the scientist’s paper [pdf]. The red line marks the Earth’s orbit (tilted sideways slightly to make it obvious), the yellow blob the shrunken heliosphere.

From the paper’s abstract:

There is overwhelming geological evidence from 60Fe and 244Pu isotopes that Earth was in direct contact with the ISM [interstellar medium] 2 million years ago, and the local ISM is home to several nearby cold clouds. Here we show, with a state-of the art simulation that incorporate all the current knowledge about the heliosphere that if the solar system passed through a cloud such as Local Leo Cold Cloud, then the heliosphere which protects the solar system from interstellar particles, must have shrunk to a scale smaller than the Earth’s orbit around the Sun (0.22).

Using a magnetohydrodynamic simulation that includes charge exchange between neutral atoms and ions, we show that during the heliosphere shrinkage, Earth was exposed to a neutral hydrogen density of up to 3000cm-3. This could have had drastic effects on Earth’s climate and potentially on human evolution at that time, as suggested by existing data.

This model is just one possible explanation of the presence of 60Fe and 244Pu isotopes on Earth. Another popular hypothesis is that a supernova occurred about 30 light years away, close enough to expose the Earth to interstellar space but not so close as to cause the total extinction of life.

With both theories, the event could also be an explanation for the significant climate changes two million years ago — such as the beginning of the most recent and now-ending ice age (no SUVs required) — as well as major evolutionary changes that occurred at that time among the ancestor species of humanity.

All is uncertain however. The scientists have no evidence the Earth actually entered a local dense cloud two million years ago. All they are doing is postulating that if such a thing happened, the dense cloud could shrink the heliosphere so much the Earth would be exposed to the interstellar medium.

Since we also do not yet have evidence of a specific nearby supernovae event either, neither theory can be favored. In fact, both could have been happened at different times in the past. Or neither.

Hat tip to reader Phil Berardelli, author of Phil’s Favorite 500: Loves of a Moviegoing Lifetime.

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The very first observations of dying star before, during, and after it goes supernova

9:43 am

Astronomers have, for the very first time, observed in real time a dying red supergiant star prior to, during, and after it exploded as a supernova, thus destroying itself and collapsing into either a neutron star or a black hole.

This discovery is unprecedented because previous observations of the star prior to its explosion were discovered post-supernova, when astronomers went back and found it in archival footage. In this case the astronomers were studying the star before it exploded, and thus got a far more detailed look at its behavior.

Prior to this, all red supergiants observed before exploding were relatively quiescent: they showed no evidence of violent eruptions or luminous emission, as was observed prior to SN 2020tlf. However, this novel detection of bright radiation coming from a red supergiant in the final year before exploding suggests that at least some of these stars must undergo significant changes in their internal structure that then results in the tumultuous ejection of gas moments before they collapse.

This data will require the computer modelers and theorists to completely revise their computer models and theories for explaining the ignition of a supernova.

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Astronomers detect 1st evidence of neutron star left behind after 1987 supernova

10:42 am

The uncertainty of science: More than three decades after the 1987 supernova in the Large Magellanic Cloud, the only naked eye supernova in the 400 years, astronomers think they might finally have detected evidence of the neutron star left over from that blast and buried within the explosion’s wake.

“Astronomers have wondered if not enough time has passed for a pulsar to form, or even if SN 1987A created a black hole,” said co-author Marco Miceli, also from the University of Palermo. “This has been an ongoing mystery for a few decades and we are very excited to bring new information to the table with this result.”

The Chandra and NuSTAR data also support a 2020 result from ALMA that provided possible evidence for the structure of a pulsar wind nebula in the millimeter wavelength band. While this “blob” has other potential explanations, its identification as a pulsar wind nebula could be substantiated with the new X-ray data. This is more evidence supporting the idea that there is a neutron star left behind.

If this is indeed a pulsar at the center of SN 1987A, it would be the youngest one ever found.

The data is still somewhat tentative and unconfirmed, but intriguing nonetheless. The pulsar itself, if it really is a pulsar, remains buried in the explosion’s expanding cloud, and has as yet not been seen directly.

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Hubble creates time lapse movie of fading supernova

10:42 am

Using the Hubble Space Telescope, astronomers have created a time lapse movie showing the fading of a supernova in a nearby galaxy over a year.

The supernova is captured by Hubble in exquisite detail within this galaxy in the left portion of the image. It appears as a very bright star located on the outer edge of one of its beautiful swirling spiral arms. This new and unique time-lapse of Hubble images created by the ESA/Hubble team shows the once bright supernova initially outshining the brightest stars in the galaxy, before fading into obscurity during the year of observations. This time-lapse consists of observations taken over the course of one year, from February 2018 to February 2019.

The video of that time lapse is embedded below the fold.

The galaxy itself is located 70 million light years away. That the supernova of this single star initially outshone the entire galaxy indicates the almost unimaginable power of the explosion.
» Read more

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Astronomers detect the first exoplanet orbiting a white dwarf

3:33 pm

Astronomers announced today that they have detected the first exoplanet orbiting a white dwarf, meaning that it somehow survived the star’s expansion into a red giant.

The way a white dwarf is created destroys nearby objects either by incineration or gravitational destruction. White dwarfs form when stars like the Sun near the end of their life cycles. They swell up, expand to hundreds and even thousands of times their regular size, forming a red giant. Eventually, that outer, expanded layer is ejected from the star and only a hot, dense white dwarf core remains.

So how did a planet, known as WD 1856 b, that is Jupiter-like get into such a close proximity that it completes an orbit of the white dwarf (that is only 18,000 km / 11,000 miles across) every 34 hours?

“WD 1856 b somehow got very close to its white dwarf and managed to stay in one piece,” said Andrew Vanderburg, an assistant professor of astronomy at the University of Wisconsin-Madison. “The white dwarf creation process destroys nearby planets, and anything that later gets too close is usually torn apart by the star’s immense gravity. We still have many questions about how WD 1856 b arrived at its current location without meeting one of those fates.”

Here we go again: This news story, as well as all of the press releases for this announcement (here, here, here, and here) — in their effort to hype this release — all conveniently forget to mention that the very first exoplanets ever discovered back in 1992 actually orbited a pulsar, the remains of a star that had not only died but had died in a cataclysmic supernova explosion. Moreover, that discovery was not of one exoplanet, but three, forming a solar system of three rocky terrestrial exoplanets all orbiting the pulsar at distances less than 43 million miles, which would put them inside the orbit of Venus.

How those terrestrial planets survived a supernova was a mystery. Today’s discovery only heightens that same puzzle, as this Jupiter-sized exoplanet orbits much closer to its white dwarf.

Regardless, the press releases from these universities and NASA should have made these facts clear. Instead, they pump up this discovery as if it is the very first ever. Today’s discovery might have unique components (the first hot Jupiter exoplanet orbiting a white dwarf) but it isn’t the first of this kind, not by a long shot.

Expect the press by tomorrow to compound this failure. Modern reporters seem completely uneducated about the subjects they write about, and also seem all-to-willing to accept on faith whatever public relations departments tell them.

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Neutron star left over from Supernova 1987A?

8:24 am

The uncertainty of science: Two different teams of astronomers are now suggesting that, based on evidence recently obtained by the Atacama Large Millimeter/submillimeter Array (ALMA), a neutron star is what is left over from the star that caused Supernova 1987A, the only naked eye supernova in the past four hundred years.

Recently, observations from the ALMA radio telescope provided the first indication of the missing neutron star after the explosion. Extremely high-resolution images revealed a hot “blob” in the dusty core of SN 1987A, which is brighter than its surroundings and matches the suspected location of the neutron star.

..The theoretical study by Page and his team, published today in The Astrophysical Journal, strongly supports the suggestion made by the ALMA team that a neutron star is powering the dust blob. “In spite of the supreme complexity of a supernova explosion and the extreme conditions reigning in the interior of a neutron star, the detection of a warm blob of dust is a confirmation of several predictions,” Page explained.

These predictions were the location and the temperature of the neutron star. According to supernova computer models, the explosion has “kicked away” the neutron star from its birthplace with a speed of hundreds of kilometers per second (tens of times faster than the fastest rocket). The blob is exactly at the place where astronomers think the neutron star would be today. And the temperature of the neutron star, which was predicted to be around 5 million degrees Celsius, provides enough energy to explain the brightness of the blob.

They haven’t actually gotten any direct evidence of this stellar remnant, so some healthy skepticism is required. At the same time, the data favors this solution, which means the star did not collapse into a black hole when it exploded.

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Astronomers discover giant arc spanning a third of the night sky

9:05 am

Astronomers have discovered a giant arc of hydrogen gas near the Big Dipper that span a third of the night sky and is thought to be the leftover shockwave from a supernova.

Ultraviolet and narrowband photography have captured the thin and extremely faint trace of hydrogen gas arcing across 30°. The arc, presented at the recent virtual meeting of the American Astronomical Society, is probably the pristine shockwave expanding from a supernova that occurred some 100,000 years ago, and it’s a record-holder for its sheer size on the sky.

Andrea Bracco (University of Paris) and colleagues came upon the Ursa Major Arc serendipitously when looking through the ultraviolet images archived by NASA’s Galaxy Evolution Explorer (GALEX). They were looking for signs of a straight, 2° filament that had been observed two decades ago — but they found out that that length of gas was less straight than they thought, forming instead a small piece of a much larger whole.

This is a great illustration of the uncertainty of science. Earlier observations spotted only 2 degrees of this arc, and thus thought it was a straight filament. Newer more sophisticated observations show that this first conclusion was in error, that it was much bigger, and curved.

I wonder what even more and better observations would reveal.

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Rethinking the theories that explain some supernovae

10:30 am

The uncertainty of science: New data now suggests that the previous consensus among astronomers that type Ia supernovae were caused by the interaction of a large red giant star with a white dwarf might be wrong, and that instead the explosion might be triggered by two white dwarfs.

If this new origin theory turns out to be correct, then it might also throw a big wrench into the theory of dark energy.

The evidence that twin white dwarfs drive most, if not all, type Ia supernovae, which account for about 20% of the supernova blasts in the Milky Way, “is more and more overwhelming,” says Dan Maoz, director of Tel Aviv University’s Wise Observatory, which tracks fast-changing phenomena such as supernovae. He says the classic scenario of a white dwarf paired with a large star such as a red giant “doesn’t happen in nature, or quite rarely.”

Which picture prevails has impacts across astronomy: Type Ia supernovae play a vital role in cosmic chemical manufacturing, forging in their fireballs most of the iron and other metals that pervade the universe. The explosions also serve as “standard candles,” assumed to shine with a predictable brightness. Their brightness as seen from Earth provides a cosmic yardstick, used among other things to discover “dark energy,” the unknown force that is accelerating the expansion of the universe. If type Ia supernovae originate as paired white dwarfs, their brightness might not be as consistent as was thought—and they might be less reliable as standard candles.

If type Ia supernovae are not reliable standard candles, then the entire Nobel Prize results that discovered dark energy in the late 1990s are junk, the evidence used to discover it simply unreliable. Dark energy might simply not exist.

What galls me about this possibility is that it was always the case. The certainty in the 1990s about using type Ia supernovae as a standard candle to determine distance was entirely unjustified. Even now astronomers do not really know what causes these explosions. To even consider them to always exhibit the same energy release was just not reasonable.

And yet astronomers in the 1990s did, and thus they fostered the theory of dark energy upon us — that the universe’s expansion was accelerating over vast distances — while winning Nobel Prizes. They still might be right, and dark energy might exist, but it was never very certain, and still is not.

Much of the fault in this does not lie with the astronomers, but with the press, which always likes to sell new theories as a certainty, scoffing over the doubts and areas of ignorance that make the theories questionable. This is just one more example of this, of which I can cite many examples, the worst of all being the reporting about global warming.

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Confirmed: Betelguese is brightening, as predicted

1:58 pm

More observations have now confirmed that Betelguese is once again brightening, as predicted.

Photometry secured over the last ~2 weeks shows that Betelgeuse has stopped its large decline of delta-V of ~1.0 mag relative to September 2019. The star reached a mean light minimum of = 1.614 +/- 0.008 mag during 07-13 February 2020. This is approximately 424+/-4 days after the last (shallower: V ~ +0.9 mag) light minimum was observed in mid-December 2018. Thus the present fading episode is consistent with the continuation of the persistent 420-430 day period present in prior photometry.

In other words, the star’s dimming, though deeper than earlier dips, was right in line with a well-known variation cycle. While absolutely worth close observation and study, the data now strongly suggests that this is relatively normal behavior for this aging red giant star. It will likely go supernova sometime in the future, not likely now.

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Astronomers think they have pinned down location of Supernova 1987a’s central star

11:10 am

More than three decades after Supernova 1987a erupted, becoming the first supernova in centuries visible to the naked eye, astronomers finally think they have narrowed the location of the neutron star remaining from that supernova.

Astronomers knew the object must exist but had always struggled to identify its location because of a shroud of obscuring dust. Now, a UK-led team thinks the remnant’s hiding place can be pinpointed from the way it’s been heating up that dust.

The researchers refer to the area of interest as “the blob”. “It’s so much hotter than its surroundings, the blob needs some explanation. It really stands out from its neighbouring dust clumps,” Prof Haley Gomez from Cardiff University told BBC News. “We think it’s being heated by the hot neutron star created in the supernova.”

It will still likely be 50 to 100 years before the dust clears enough for the neutron star itself to be visible.

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TESS spots first exoplanets plus supernovae and more

5:17 pm

The Transiting Exoplanet Surveying Satellite (TESS) has successful spotted its first exoplanets.

NASA’s Transiting Exoplanet Survey Satellite (TESS) has found three confirmed exoplanets, or worlds beyond our solar system, in its first three months of observations.

The mission’s sensitive cameras also captured 100 short-lived changes — most of them likely stellar outbursts — in the same region of the sky. They include six supernova explosions whose brightening light was recorded by TESS even before the outbursts were discovered by ground-based telescopes.

These discoveries confirm that the spacecraft is operating exactly as designed. Now comes the herculean task of analyzing the gigantic amount of data it is pouring down to see what is hidden there.

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Astronomers get best and earliest view of supernovae ever

9:15 am

Using ground-based telescopes as well as the space telescope Kepler astronomers have obtained their best and earliest view of a Type Ia supernova.

The supernova, named SN 2018oh, was brighter than expected over the first few days. The increased brightness is an indication that it slammed into a nearby companion star. This adds to the growing body of evidence that some, but not all, of these thermonuclear supernovae have a large companion star that triggers the explosion.

Las Cumbres Observatory (LCO), based in Goleta, California, is a global network of 21 robotic telescopes that obtained some of the best data characterizing the supernova in support of the NASA mission. Wenxiong Li, the lead author of one of three papers published today on the finding, was based at LCO when much of the research was underway. Five other LCO astronomers, who are affiliated with the University of California Santa Barbara (UCSB), also contributed to two of the papers.

Understanding the origins of Type Ia supernovae is critical because they are used as standard candles to map out distances in cosmology. They were used to discover Dark Energy, the mysterious force causing the universe to accelerate in its expansion. Astronomers have long known that a supernova is the explosion of a dense white dwarf star (A white dwarf has the mass of the sun, but only the radius of the Earth; one teaspoon of a white dwarf would weigh roughly 23000 pounds) What triggers the explosion is less well understood. One theory holds that the explosions are the merger of two white dwarf stars. Another is that the second star is not a white dwarf at all, but a normal-sized or even giant star that loses only some of its matter to the white dwarf to initiate the explosion. In this theory, the explosion then smashes into the surviving second star, causing the supernova to be exceedingly bright in its early hours.

Finding that Type Ia supernovae can be brighter than previously believed throws a wrench into the results that discovered dark energy, since those results made assumptions about the brightness and thus the distance of those supernovae. If the brightness of these supernovae are not as reliable as expected, they are also less of a standard candle for estimating distance.

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Astronomers identify first progenitor star for Type 1C supernovae

3:27 pm

Astronomers have for the first time identified a progenitor star for a Type 1C supernovae.

[The search for supernovae progenitor stars has found] a few pre-supernova stars. But the doomed stars for one class of supernova have eluded discovery: the hefty stars that explode as Type Ic supernovas. These stars, weighing more than 30 times our Sun’s mass, lose their hydrogen and helium layers before their cataclysmic death. Researchers thought they should be easy to find because they are big and bright. However, they have come up empty. Finally, in 2017, astronomers got lucky. A nearby star ended its life as a Type Ic supernova. Two teams of researchers pored through the archive of Hubble images to uncover the putative precursor star in pre-explosion photos taken in 2007. The supernova, catalogued as SN 2017ein, appeared near the center of the nearby spiral galaxy NGC 3938, located roughly 65 million light-years away.

An analysis of the candidate star’s colors shows that it is blue and extremely hot. Based on that assessment, both teams suggest two possibilities for the source’s identity. The progenitor could be a single star between 45 and 55 times more massive than our Sun. Another idea is that it could have been a binary-star system in which one of the stars weighs between 60 and 80 times our Sun’s mass and the other roughly 48 solar masses. In this latter scenario, the stars are orbiting closely and interact with each other. The more massive star is stripped of its hydrogen and helium layers by the close companion, and eventually explodes as a supernova.

As can be seen by the quote above, identifying the star that exploded still leaves much unknown, including whether the star is a single or a binary. Still, they finally have some idea what kind of star erupts in a Type IIC supernovae, which will help constrain the theories for explaining the cause of these explosions.

Note also that this identification will not be confirmed until the supernova itself completely fades in about two years. They might find when that happens that the candidate progenitor is still there, meaning it was not the progenitor of the supernova at all.

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Timelapse movie of Supernova 1987A’s evolution from 1992 to 2017

9:42 am

Cool movie time! An astronomy graduate student in Toronto has created a movie showing the steady evolution of the shock wave from Supernova 1987A, the first supernova visible to the naked eye since the discovery of the telescope, during the past twenty-five years.

Yvette Cendes, a graduate student with the University of Toronto and the Leiden Observatory, has created a time-lapse showing the aftermath of the supernova over a 25-year period, from 1992 to 2017. The images show the shockwave expanding outward and slamming into debris that ringed the original star before its demise.

In an accompanying paper, published in the Astrophysical Journal on October 31st, Cendes and her colleagues add to the evidence that the expanding remnant is shaped—not like a ring like those of Saturn’s—but like a donut, a form known as a torus. They also confirm that the shockwave has now picked up some one thousand kilometres per second in speed. The acceleration has occurred because the expanding torus has punched through the ring of debris.

The animation, which I have embedded below the fold, uses images produced by an array radio telescopes in Australia.
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How to blow up a star

8:29 am

Link here. The story details the new supercomputer simulation work attempting to model the internal processes inside a dying star that cause it to explode as a supernova.

For more than half a century, physicists have suspected that the heat produced by elusive particles called neutrinos, created in the core of a star, could generate a blast that radiates more energy in a single second than the Sun will in its lifetime. But they have had trouble proving that hypothesis. The detonation process is so complex — incorporating general relativity, fluid dynamics, nuclear and other physics — that computers have struggled to mimic the mechanism in silico. And that poses a problem. “If you can’t reproduce it,” Janka says, “that means you don’t understand it.”

Now, improvements in raw computing power, along with efforts to capture the stellar physics in acute detail, have enabled substantial progress. Janka’s simulation marked the first time that physicists had been able to get a realistic 3D model of the most common type of supernova to explode. Just months later, a competing group based at Oak Ridge National Laboratory in Tennessee repeated the feat with a heavier, more complex star. The field is now buzzing, with more than half a dozen teams currently working on exploding stars in 3D.

They have apparently solved one problem, figuring out how the neutrino blast wave gets enough energy to blast free from the star’s core. A close read of the article indicates that, while progress has been made, they still have many gaps of their understanding.

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“One of the greatest discoveries of the century is based on these things and we don’t even know what they are, really.”

9:42 am

The uncertainty of science: New research suggests that astronomers have little understanding of the supernovae that they use to estimate the distance to most galaxies, estimates they then used to discover dark energy as well as measure the universe’s expansion rate.

The exploding stars known as type Ia supernovae are so consistently bright that astronomers refer to them as standard candles — beacons that are used to measure vast cosmological distances. But these cosmic mileposts may not be so uniform. A new study finds evidence that the supernovae can arise by two different processes, adding to lingering suspicions that standard candles aren’t so standard after all.

The findings, which have been posted on the arXiv preprint server and accepted for publication in the Astrophysical Journal, could help astronomers to calibrate measurements of the Universe’s expansion. Tracking type Ia supernovae showed that the Universe is expanding at an ever-increasing rate, and helped to prove the existence of dark energy — advances that secured the 2011 Nobel Prize in Physics.

The fact that scientists don’t fully understand these cosmological tools is embarrassing, says the latest study’s lead author, Griffin Hosseinzadeh, an astronomer at the University of California, Santa Barbara. “One of the greatest discoveries of the century is based on these things and we don’t even know what they are, really.”

The key to understanding this situation is to maintain a healthy skepticism about any cosmological theory or discovery, no matter how enthusiastically touted by the press and astronomers. The good astronomers do not push these theories with great enthusiasm as they know the feet of clay on which they stand. The bad ones try to use the ignorant mainstream press to garner attention, and thus funding.

For the past two decades the good astronomers have been diligently checking and rechecking the data and the supernovae used to discover dark energy. Up to now this checking seems to still suggest the universe’s expansion is accelerating on large scales. At the same time, our knowledge of supernovae remains sketchy, and thus no one should assume we understand the universe’s expansion rate with any confidence.

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The supernovae that fertilized the Earth

5:45 pm

A new study has pinned down the dates of two recent supernovae that showered the Earth with the heavier elements that make life here possible.

Many mainstream articles about this story have been implying that this research has discovered the existence of supernovae near the primordial Earth. This is false. Scientists have had evidence of these early supernovae for decades, from asteroids, in isotopes on Earth, and in the existence of the Local Bubble in which the Sun is presently traveling. What this study has done is narrow the location and the time of at least two of these supernovae, a significant discovery, though not the one much of the ignorant press is pushing.

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Most powerful supernovae ever

6:56 pm

The uncertainty of science: Astronomers have discovered the most powerful supernovae ever detected.

This one, called ASASSN-15lh, is about 3.8 billion light years away, 200 times more powerful than most supernovas, and twice as bright as the previous record holder. It shines 20 times brighter than the combined output of the Milky Way’s 100 billion stars, and in the last six months, it has spewed as much energy as the sun would in 10 lifetimes, says Krzysztof Stanek of the Ohio State University, co-principal investigator of the All Sky Automated Survey for SuperNovae (ASAS-SN) network that spotted the explosion. “This is really on steroids, and then some,” he says. “If it was in our own galaxy, it would shine brighter than the full moon; there would be no night, and it would be easily seen during the day.”

At the moment astronomers don’t really have an theory to explain how the supernovae could produce that much energy.

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Dark energy evidence found to be uncertain

10:10 am

The uncertainty of science: Astronomers have discovered that the type of supernovae they have used as a standard to measure the accelerating expansion of the universe, which also is evidence for the existence of dark energy, are actually made up of two different types.

The authors conclude that some of the reported acceleration of the universe can be explained by color differences between the two groups of supernovae, leaving less acceleration than initially reported. This would, in turn, require less dark energy than currently assumed. “We’re proposing that our data suggest there might be less dark energy than textbook knowledge, but we can’t put a number on it,” Milne said. “Until our paper, the two populations of supernovae were treated as the same population. To get that final answer, you need to do all that work again, separately for the red and for the blue population.”

The authors pointed out that more data have to be collected before scientists can understand the impact on current measures of dark energy.

It has always bothered me that the evidence for dark energy was based entirely on measurements of type 1a supernovae from extremely far away and billions of years ago. Not only was that a different time in the universe’s history when conditions could be different, our actual understanding of those supernovae themselves is very tenuous. We really do not have a full understanding of what causes them, or how they even happen. To then assume that these distant explosions are all so similar that their brightness can be used as a “standard” seems untrustworthy. From my perspective, the conclusions, though interesting, are being pushed based on extremely weak data.

The research at the link illustrates just how weak that data was.

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