Astronomers Finally Find the Neutron Star Leftover from Supernova 1987A

Astronomers at Cardiff University have done something nobody else has been able to do. A team, led by Dr. Phil Cigan from Cardiff University’s School of Physics and Astronomy, has found the neutron star remnant from the famous supernova SN 1987A. Their evidence ends a 30 year search for the object.

Continue reading “Astronomers Finally Find the Neutron Star Leftover from Supernova 1987A”

Pulsar Seen Speeding Away From the Supernova That Created it

When a star exhausts its nuclear fuel towards the end of its lifespan, it undergoes gravitational collapse and sheds its outer layers. This results in a magnificent explosion known as a supernova, which can lead to the creation of a black hole, a pulsar or a white dwarf. And despite decades of observation and research, there is still much scientists don’t know about this phenomena.

Luckily, ongoing observations and improved instruments are leading to all kinds of discoveries that offer chances for new insights. For instance, a team of astronomers with the National Radio Astronomy Observatory (NRAO) and NASA recently observed a “cannonball” pulsar speeding away from the supernova that is believed to have created it. This find is already providing insights into how pulsars can pick up speed from a supernova.

Continue reading “Pulsar Seen Speeding Away From the Supernova That Created it”

Astronomers are Continuing to Watch the Shockwaves Expand from Supernova SN1987A, as they Crash Into the Surrounding Interstellar Medium

When stars reach the end of their life cycle, many will blow off their outer layers in an explosive process known as a supernova. While astronomers have learned much about this phenomena, thanks to sophisticated instruments that are able to study them in multiple wavelengths, there is still a great deal that we don’t know about supernovae and their remnants.

For example, there are still unresolved questions about the mechanisms that power the resulting shock waves from a supernova. However, an international team of researchers recently used data obtained by the Chandra X-Ray Observatory of a nearby supernova (SN1987A) and new simulations to measure the temperature of the atoms in the resulting shock wave.

Continue reading “Astronomers are Continuing to Watch the Shockwaves Expand from Supernova SN1987A, as they Crash Into the Surrounding Interstellar Medium”

Astronomers See the Exact Moment a Supernova Turned into a Black Hole (or Neutron Star)

A look at The Cow (approximately 80 days after explosion) from the W.M. Keck Observatory in Maunakea, Hawaii. The Cow is nestled in the CGCG 137-068 galaxy, 200 million light years from Earth. Image Credit:Raffaella Margutti/Northwestern University

On June 17th 2018, the ATLAS (Asteroid Terrestrial-impact Last Alert System) survey’s twin telescopes spotted something extraordinarily bright in the sky. The source was 200 million light years away in the constellation Hercules. The object was given the name AT2018cow or “The Cow.” The Cow flared up quickly, and then just as quickly it was gone.

What was it?

Continue reading “Astronomers See the Exact Moment a Supernova Turned into a Black Hole (or Neutron Star)”

A Guide to Hunting Zombie Stars

R Aquarii is called a symbiotic star system because of their relationship. As the white dwarf draws in material from the Red Giant, it ejects some if it in weird looping patterns, seen in this Hubble image. Image Credit: By Judy Schmidt from USA - Symbiotic System R Aquarii, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=63473035

Apparently not all supernovas work. And when they fail, they leave behind a half-chewed remnant, still burning from leftover heat but otherwise lifeless: a zombie star. Astronomers aren’t sure how many of these should-be-dead creatures lurk in the interstellar depths, but with recent simulations scientists are making a list of their telltale signatures so that future surveys can potentially track them down.

Continue reading “A Guide to Hunting Zombie Stars”

A Supernova 2.6 Million Years Ago Could Have Wiped Out the Ocean’s Large Animals

Artist's impression of a Type II supernova. Credit: ESO

For many years, scientists have been studying how supernovae could affect life on Earth. Supernovae are extremely powerful events, and depending on how close they are to Earth, they could have consequences ranging from the cataclysmic to the inconsequential. But now, the scientists behind a new paper say they have specific evidence linking one or more supernova to an extinction event 2.6 million years ago.

About 2.6 million years ago, one or more supernovae exploded about 50 parsecs, or about 160 light years, away from Earth. At that same time, there was also an extinction event on Earth, called the Pliocene marine megafauna extinction. Up to a third of the large marine species on Earth were wiped out at the time, most of them living in shallow coastal waters.

“This time, it’s different. We have evidence of nearby events at a specific time.” – Dr. Adrian Melott, University of Kansas.

Continue reading “A Supernova 2.6 Million Years Ago Could Have Wiped Out the Ocean’s Large Animals”

Astronomers Finally Spot the Type of Star That Leads to Type 1C Supernovae

As astronomical phenomena go, supernovae are among the most fascinating and spectacular. This process occurs when certain types of stars reach the end of their lifespan, where they explode and throw off their outer layers. Thanks to generations of study, astronomers have been able to classify most observed supernovae into one of two categories (Type I and Type II) and determine which kinds of stars are the progenitors for each.

However, to date, astronomers have been unable to determine which type of star eventually leads to a Type Ic supernova – a special of class where a star undergoes core collapse after being stripped of its hydrogen and helium. But thanks to the efforts of two teams of astronomers that pored over archival data from the Hubble Space Telescope, scientists have now found the long sought-after star that causes this type of supernova.

Continue reading “Astronomers Finally Spot the Type of Star That Leads to Type 1C Supernovae”

A Magnetar Just Woke Up After Three Years of Silence

When stars reach the end of their main sequence, they undergo a gravitational collapse, ejecting their outermost layers in a supernova explosion. What remains afterward is a dense, spinning core primarily made up of neutrons (aka. a neutron star), of which only 3000 are known to exist in the Milky Way Galaxy. An even rarer subset of neutron stars are magnetars, only two dozen of which are known in our galaxy.

These stars are especially mysterious, having extremely powerful magnetic fields that are almost powerful enough to rip them apart. And thanks to a new study by a team of international astronomers, it seems the mystery of these stars has only deepened further. Using data from a series of radio and x-ray observatories, the team observed a magnetar last year that had been dormant for about three years, and is now behaving somewhat differently.

The study, titled “Revival of the Magnetar PSR J1622–4950: Observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR“, recently appeared in The Astrophysical Journal. The team was led by Dr Fernando Camilo – the Chief Scientist at the South African Radio Astronomy Observatory (SARAO) – and included over 200 members from multiple universities and research institutions from around the world.

Magnetars are so-named because their magnetic fields are up to 1000 times stronger than those of ordinary pulsating neutron stars (aka. pulsars). The energy associated with these these fields is so powerful that it almost breaks the star apart, causing them to be unstable and display great variability in terms of their physical properties and electromagnetic emissions.

Whereas all magnetars are known to emit X-rays, only four have been known to emit radio waves. One of these is PSR J1622-4950 – a magnetar located about 30,000 light years from Earth. As of early 2015, this magnetar had been in a dormant state. But as the team indicated in their study, astronomers using the CSIRO Parkes Radio Telescope in Australia noted that it was becoming active again on April 26th, 2017.

At the time, the magnetar was emitting bright radio pulses every four seconds. A few days later, Parkes was shut down as part of a month-long planned maintenance routine. At about the same time, South Africa’s MeerKAT radio telescope began monitoring the star, despite the fact that it was still under construction and only 16 of its 64 radio dishes were available. Dr Fernando Camilo describes the discovery in a recent SKA South Africa press release:

“[T]he MeerKAT observations proved critical to make sense of the few X-ray photons we captured with NASA’s orbiting telescopes – for the first time X-ray pulses have been detected from this star, every 4 seconds. Put together, the observations reported today help us to develop a better picture of the behaviour of matter in unbelievably extreme physical conditions, completely unlike any that can be experienced on Earth”.

Artist’s rendering of an outburst on an ultra-magnetic neutron star, also called a magnetar. Credit: NASA/Goddard Space Flight Center

After the initial observations were made by the Parkes and MeerKAT observatories, follow-up observations were conducted using the XMM-Newton x-ray space observatory, Swift Gamma-Ray Burst Mission, the Chandra X-ray Observatory, and the Nuclear Spectroscopic Telescope Array (NuSTAR). With these combined observations, the team noted some very interesting things about this magnetar.

For one, they determined that PSR J1622-4950’s radio flux density, while variable, was approximately 100 times greater than it was during its dormant state. In addition, the x-ray flux was at least 800 times larger one month after reactivation, but began decaying exponentially over the course of a 92 to 130 day period. However, the radio observations noted something in the magnetar’s behavior that was quite unexpected.

While the overall geometry that was inferred from PSR J1622-4950’s radio emissions was consistent with what had been determined several years prior, their observations indicated that the radio emissions were now coming from a different location in the magnetosphere. This above all indicates how radio emissions from magnetars could differ from ordinary pulsars.

This discovery has also validated the MeerKAT Observatory as a world-class research instrument. This observatory is part of the Square Kilometer Array (SKA), the multi-radio telescope project that is building the world’s largest radio telescope in Australia, New Zealand, and South Africa. For its part, MeerKAT uses 64 radio antennas to gather radio images of the Universe to help astronomers understand how galaxies have evolved over time.

Aerial image of the South African MeerKAT radio telescope in the Karoo, South Africa. Credit: SKA

Given the sheer volume of data collected by these telescopes, MeerKAT relies on both cutting edge-technology and a highly-qualified team of operators. As Abbott indicated, “we have a team of the brightest engineers and scientists in South Africa and the world working on the project, because the problems that we need to solve are extremely challenging, and attract the best”.

Prof Phil Diamond, the Director-General of the SKA Organization leading the development of the Square Kilometer Array, was also impressed by the contribution of the MeerKAT team. As he stated in an SKA press release:

“Well done to my colleagues in South Africa for this outstanding achievement. Building such telescopes is extremely difficult, and this publication shows that MeerKAT is becoming ready for business. As one of the SKA precursor telescopes, this bodes well for the SKA. MeerKAT will eventually be integrated into Phase 1 of SKA-mid telescope bringing the total dishes at our disposal to 197, creating the most powerful radio telescope on the planet”.

When the SKA goes online, it will be one of the most powerful ground-based telescopes in the world and roughly 50 times more sensitive than any other radio instrument. Along with other next-generation ground-based and space-telescopes, the things it will reveal about our Universe and how it evolved over time are expected to be truly groundbreaking.

Further Reading: SKA Africa, SKA, The Astrophysical Journal

Astronomers Find The Most Distant Supernova Ever: 10.5 Billion Light-Years Away

Astronomers have discovered the most distant supernova yet, at a distance of 10.5 billion light years from Earth. The supernova, named DES16C2nm, is a cataclysmic explosion that signaled the end of a massive star some 10.5 billion years ago. Only now is the light reaching us. The team of astronomers behind the discovery have published their results in a new paper available at arXiv.

“…sometimes you just have to go out and look up to find something amazing.” – Dr. Bob Nichol, University of Portsmouth.

The supernova was discovered by astronomers involved with the Dark Energy Survey (DES), a collaboration of astronomers in different countries. The DES’s job is to map several hundred million galaxies, to help us find out more about dark energy. Dark Energy is the mysterious force that we think is causing the accelerated expansion of the Universe.

DES16C2nm was first detected in August 2016. Its distance and extreme brightness were confirmed in October that year with three of our most powerful telescopes – the Very Large Telescope and the Magellan Telescope in Chile, and the Keck Observatory, in Hawaii.

This image from 2015 shows the same area of sky before DES16C2nm exploded. Image: Mat Smith and DES collaboration.

DES16C2nm is what’s known as a superluminous supernova (SLSN), a type of supernova only discovered 10 years ago. SLSNs are the rarest—and the brightest—type of supernova that we know of. After the supernova exploded, it left behind a neutron star, which is the densest type of object in the universe. The extreme brightness of SLSNs, which can be 100 times brighter than other supernovae, are thought to be caused by material falling into the neutron star.

“It’s thrilling to be part of the survey that has discovered the oldest known supernova.” – Dr Mathew Smith, lead author, University of Southampton

Lead author of the study Dr Mathew Smith, of the University of Southampton, said: “It’s thrilling to be part of the survey that has discovered the oldest known supernova. DES16C2nm is extremely distant, extremely bright, and extremely rare – not the sort of thing you stumble across every day as an astronomer.”

Dr. Smith went on to say that not only is the discovery exciting just for being so distant, ancient, and rare. It’s also providing insights into the cause of SLSNs: “The ultraviolet light from SLSN informs us of the amount of metal produced in the explosion and the temperature of the explosion itself, both of which are key to understanding what causes and drives these cosmic explosions.”

“Now we know how to find these objects at even greater distances, we are actively looking for more of them as part of the Dark Energy Survey.” – Co-author Mark Sullivan, University of Southampton.

Now that the international team behind the Dark Energy Survey has found one of the SLSNs, they want to find more. Co-author Mark Sullivan, also of the University of Southampton, said: “Finding more distant events, to determine the variety and sheer number of these events, is the next step. Now we know how to find these objects at even greater distances, we are actively looking for more of them as part of the Dark Energy Survey.”

The instrument used by DES is the newly constructed Dark Energy Camera (DECam), which is mounted on the Victor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory (CTIO) in the Chilean Andes. DECam is an extremely sensitive 570-megapixel digital camera designed and built just for the Dark Energy Survey.

The DECam in operation at its home in the Chilean Andes. The extremely sensitive, 570 megapixel camera is mounted on the Victor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory. Image: DES/CTIO

The Dark Energy Survey involves more than 400 scientists from over 40 international institutions. It began in 2013, and will wrap up its five year mission sometime in 2018. The DES is using 525 nights of observation to carry out a deep, wide-area survey to record information from 300 million galaxies that are billions of light-years from Earth. DES is designed to help us answer a burning question.

According to Einstein’s General Relativity Theory, gravity should be causing the expansion of the universe to slow down. And we thought it was, until 1998 when astronomers studying distant supernovae found that the opposite is true. For some reason, the expansion is speeding up. There are really only two ways of explaining this. Either the theory of General Relativity needs to be replaced, or a large portion of the universe—about 70%—consists of something exotic that we’re calling Dark Energy. And this Dark Energy exerts a force opposite to the attractive force exerted by “normal” matter, causing the expansion of the universe to accelerate.

“…sometimes you just have to go out and look up to find something amazing.” – Dr. Bob Nichol, University of Portsmouth.

To help answer this question, the DES is imaging 5,000 square degrees of the southern sky in five optical filters to obtain detailed information about each of the 300 million galaxies. A small amount of the survey time is also used to observe smaller patches of sky once a week or so, to discover and study thousands of supernovae and other astrophysical transients. And this is how DES16C2nm was discovered.

Study co-author Bob Nichol, Professor of Astrophysics and Director of the Institute of Cosmology and Gravitation at the University of Portsmouth, commented: “Such supernovae were not thought of when we started DES over a decade ago. Such discoveries show the importance of empirical science; sometimes you just have to go out and look up to find something amazing.”