Astronomers have identified six massive stars before they exploded as core-collapse supernovae

The venerable Hubble House Telescope has given us a lot through the historical past of its service (32 years, seven months, six days, and counting). Even in any case these years, the versatile and complex observatory remains to be pulling its weight alongside newer addition, just like the James Webb House Telescope (JWST) and different members of NASA’s Nice Observatories household. Along with how it’s nonetheless conducting commentary campaigns, astronomers and astrophysicists are combing via the volumes of knowledge Hubble collected through the years to seek out much more hidden gems.

A workforce led by Caltech’s not too long ago made some very fascinating finds within the Hubble archives, the place they noticed the websites of six supernovae to study extra about their progenitor stars. Their observations have been a part of the Hubble House Telescope Snapshot program, the place astronomers use HST pictures to chart the life cycle and evolution of stars, galaxies, and different celestial objects. From this, they have been in a position to place constraints on the scale, mass, and different key traits of the progenitor stars and what they skilled earlier than experiencing core collapse.

The workforce was led by Dr. Schuyler D. Van Dyk, a senior analysis scientist with Caltech’s Infrared Processing and Evaluation Middle (IPAC). His teammates included researchers from the College of California, Berkeley, the House Telescope Science Institute, the College of Arizona’s Steward Observatory, the College of Hawai’i’s Institute for Astronomy, and the Faculty of Physics and Astronomy on the College of Minnesota. Their findings have been printed in a paper titled “The disappearance of six supernova progenitors” that may seem within the Month-to-month Notices of the Royal Astronomical Society.

As they point out of their paper, the targets of their research have been all close by core-collapse supernovae (SNe) that Hubble imaged at excessive spatial resolutions. The pictures have been a part of the Hubble Snapshot program, created by the House Telescope Science Institute (STScI) to offer a big pattern of pictures for varied targets. Each goal is noticed in a single orbit of Hubble across the Earth between different commentary packages, permitting a level of flexibility that isn’t doable with different observatories.

For his or her research, Van Dyk and his colleagues examined pictures of six extragalactic supernovae earlier than and after they exploded—designated SN 2012A, SN 2013ej, SN 2016gkg, SN 2017eaw, SN 2018zd, and SN 2018aoq. With extragalactic targets, astronomers have problem realizing if the celebs they recognized have been progenitors to the supernova, given the space concerned. As Van Dyk to universe At present by way of e mail, the one method to make sure is to attend for the supernova to dim, then affirm that the progenitor star has disappeared:

“For the reason that supernova explosion is so luminous, now we have to attend plenty of years till it has pale sufficient that it’s much less luminous than was the progenitor. In a number of of the circumstances we present in our paper, there’s little query that the star that was there pre-explosion is now gone. Within the different circumstances, we’re moderately certain, however the supernova remains to be detectable and is simply faint sufficient for us to deduce that the progenitor has vanished.”

In a earlier research, Van Dyk and a number of other colleagues who have been co-authors of this research investigated one other supernova (iPTF13bvn) whose progenitor star disappeared. On this case, the analysis workforce relied on information obtained by Hubble of the SN web site—as a part of the Ultraviolet Extremely Deep Subject (UVUDF) marketing campaign—roughly 740 days after the star exploded. In 2013, Van Dyk led a research that used pictures from an earlier Snapshot program to verify that the progenitor of SN 2011dh within the Whirlpool galaxy (Messier 51) had disappeared.

These and different papers through the years have proven that progenitor candidates might be immediately recognized from pre-explosion pictures. On this most up-to-date research, Van Dyk and his colleagues noticed supernovae within the later levels of their evolution to study what mechanisms are powering them. In lots of circumstances, the mechanism is the decay of radioactive nuclei (specifically, radioactive nickel, cobalt, and iron) that have been synthesized by the big power of the explosion. However as he defined, they suspected that different mechanisms could be concerned:

“Nonetheless, now we have indications that some supernovae inevitably have further energy sources—one risk is that the sunshine of the supernova has been scattered by interstellar dust speedy to the explosion, within the type of a ‘gentle echo’; one other extra doubtless risk is that the shockwave related to the explosion is interacting with gasoline that was deposited across the progenitor star by the star itself through the course of the star’s life, within the type of wind or outburst, that’s, circumstellar matter. The ejecta from the explosion shifting via and interacting with this circumstellar matter can lead to luminous power that may persist for years, even for many years.”

Briefly, the workforce was making an attempt to estimate how most of the supernovae they noticed advanced via radioactive decay versus extra unique powering mechanisms. Their outcomes confirmed that SN 2012A, SN 2018zd, and SN 2018aoq had pale to the purpose the place they have been not detectable within the Hubble Snapshot pictures, whereas SN 2013ej, SN 2016gkg, and SN 2017eaw had pale simply sufficient. Due to this fact, they may infer in all six circumstances that the progenitors had disappeared. Nonetheless, not all have been the results of a single large star present process core collapse.

Within the case of SN 2016gkg, the photographs acquired by Hubble’s Extensive Subject Digicam 3 (WFC3) have been of a lot greater spatial decision and sensitivity than the photographs of the host galaxy, beforehand taken by the now-retired WFC2. This allowed them to theorize that SN 2016gkg was not the results of a single core-collapse supernova however a progenitor star interacting with a neighboring star.

Mentioned Van Dyk, “So, within the previous picture, the progenitor appeared like one ‘star,’ whereas within the new pictures, we might see that the progenitor needed to have been spatially distinct from the neighboring star. Due to this fact, we have been in a position to acquire a greater estimate of the progenitor’s luminosity and shade, now uncontaminated by the neighbor, and from that, we have been in a position to make some new inferences concerning the total properties of the progenitor, or, on this case, progenitor system, since we characterised the brand new outcomes utilizing present fashions of binary star programs.”

Particularly, they decided that the progenitor belonged to the category of “stripped-envelope” supernovae (SESNe), during which the outer hydrogen H-rich envelope of the progenitor star has been considerably or solely eliminated. They additional estimated that the progenitor was the first and its companion was doubtless a fundamental sequence star. They even positioned constraints on their respective plenty earlier than the explosion (4.6 and 17–20.5 solar plenty, respectively).

After consulting pictures taken across the identical time by one other Snapshot program, additionally they observed one thing fascinating about SN 2017eaw. These pictures indicated that this supernova was particularly luminous within the UV band (an “ultraviolet extra”). By combining these pictures with their information, Van Dyk and his workforce speculated that SN 2017eaw had an extra of sunshine within the UV on the time it was noticed, which was doubtless attributable to interplay between the supernova shock and the circumstellar medium round that progenitor.

The workforce additionally famous that the dust created by a supernova explosion is a complicating issue because of the way it cools because it expands outward. This dust, mentioned Van Dyk, can obscure gentle from distant sources and result in problems with the observations.

“The caveat right here, then, is that the star that we noticed pre-explosion may not be the progenitor in any respect, for example and—once more, due to the distances to the host galaxies—that star is inside fractions of a pixel of the particular progenitor (bodily, within the speedy neighborhood of the progenitor), such that, if the supernova has made dust, that dust is successfully blanketing each the supernova and that neighboring star. That is doable, however not inordinately doubtless. And it turns into a tougher argument to make in these few circumstances the place nothing is seen on the supernova place years later—as we level out within the paper, that will require huge quantities of dust, which is probably going bodily not doable.”

Tracing the origins of supernovae is likely one of the some ways astronomers can study extra concerning the life cycle of stars. With improved devices, data collection, and adaptability, they can reveal extra about how our universe advanced and can proceed to vary over time.