Dr. Avi Loeb Thinks the Government Should set its Sights on Big Ideas in Space Exploration

Buzz Aldrin on the Moon

On July 20th, 2019, exactly 50 years will have passed since human beings first set foot on the Moon. To mark this anniversary, NASA will be hosting a number of events and exhibits and people from all around the world will be united in celebration and remembrance. Given that crewed lunar missions are scheduled to take place again soon, this anniversary also serves as a time to reflect on the lessons learned from the last “Moonshot”.

For one, the Moon Landing was the result of years of government-directed research and development that led to what is arguably the greatest achievement in human history. This achievement and the lessons it taught were underscored in a recent essay by two Harvard astrophysicists. In it, they recommend that the federal government continue to provide active leadership in the field of space research and exploration.

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Weekly Space Hangout: June 19, 2019 – Corey Gray, Lead Operator at the LIGO Hanford Observatory

Hosts:
Fraser Cain (universetoday.com / @fcain)
Dr. Kimberly Cartier (KimberlyCartier.org / @AstroKimCartier )
Dr. Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg & ChartYourWorld.org)
Dr. Brian Koberlein (briankoberlein.com / @BrianKoberlein)

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As Expected, the Newly Upgraded LIGO is Finding a Black Hole Merger Every Week

In February 2016, LIGO detected gravity waves for the first time. As this artist's illustration depicts, the gravitational waves were created by merging black holes. The third detection just announced was also created when two black holes merged. Credit: LIGO/A. Simonnet.

In February of 2016, scientists at the Laser Interferometer Gravitational-wave Observatory (LIGO) announced the first-ever detection of gravitational waves (GWs). Since then, multiple events have been detected, providing insight into a cosmic phenomena that was predicted over a century ago by Einstein’s Theory of General Relativity.

A little over a year ago, LIGO was taken offline so that upgrades could be made to its instruments, which would allow for detections to take place “weekly or even more often.” After completing the upgrades on April 1st, the observatory went back online and performed as expected, detecting two probable gravitational wave events in the space of two weeks.

Continue reading “As Expected, the Newly Upgraded LIGO is Finding a Black Hole Merger Every Week”

LIGO Just Got a Big Upgrade, Will Begin Searching for Gravitational Waves Again on April 1st

In February of 2016, scientists at the Laser Interferometer Gravitational-wave Observatory (LIGO) made history by announcing the first-ever detection of gravitational waves (GWs). These ripples in the very fabric of the Universe, which are caused by black hole mergers or white dwarfs colliding, were first predicted by Einstein’s Theory of General Relativity roughly a century ago.

About a year ago, LIGO’s two facilities were taken offline so its detectors could undergo a series of hardware upgrades. With these upgrades now complete, LIGO recently announced that the observatory will be going back online on April 1st. At that point, its scientists are expecting that its increased sensitivity will allow for “almost daily” detections to take place.

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New Gravitational Waves Detected From Four More Black Hole Mergers. Total Detections up to 11 Now

On February 11th, 2016, scientists at the Laser Interferometer Gravitational-wave Observatory (LIGO) made history when they announced the first-ever detection of gravitational waves (GWs). Since that time, multiple detections have taken place and scientific collaborations between observatories  – like Advanced LIGO and Advanced Virgo – are allowing for unprecedented levels of sensitivity and data sharing.

Previously, seven such events had been confirmed, six of which were caused by the mergers of binary black holes (BBH) and one by the merger of a binary neutron star. But on Saturday, Dec. 1st, a team of scientists the LIGO Scientific Collaboration (LSC) and Virgo Collaboration presented new results that indicated the discovery of four more gravitational wave events. This brings the total number of GW events detected in the last three years to eleven.

Continue reading “New Gravitational Waves Detected From Four More Black Hole Mergers. Total Detections up to 11 Now”

Gravitational waves were only recently observed, and now astronomers are already thinking of ways to use them: like accurately measuring the expansion rate of the Universe

Neutron stars scream in waves of spacetime when they die, and astronomers have outlined a plan to use their gravitational  agony to trace the history of the universe. Join us as we explore how to turn their pain into our cosmological profit.

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How to Listen to the Background Hum of Gravitational Waves From all the Black Holes Colliding into Each Other

The first-ever detection of gravitational waves (which took place in September of 2015) triggered a revolution in astronomy. Not only did this event confirm a theory predicted by Einstein’s Theory of General Relativity a century before, it also ushered in a new era where the mergers of distant black holes, supernovae, and neutron stars could be studied by examining their resulting waves.

In addition, scientists have theorized that black hole mergers could actually be a lot more common than previously thought. According to a new study conducted by pair of researchers from Monash University, these mergers happen once every few minutes. By listening to the background noise of the Universe, they claim, we could find evidence of thousands of previously undetected events.

Their study, titled “Optimal Search for an Astrophysical Gravitational-Wave Background“, recently appeared in the journal Physical Review X. The study was conducted by Rory Smith and Eric Thrane, a senior lecturer and a research fellow at Monash University, respectively. Both researchers are also members of the ARC Center of Excellence for Gravitational Wave Discovery (OzGrav).

Drs. Eric Thrane and Rory Smith. Credit: Monash University

As they state in their study, every 2 to 10 minutes, a pair of stellar-mass black holes merge somewhere in the Universe. A small fraction of these are large enough that the resulting gravitational wave event can be detected by advanced instruments like the Laser Interferometer Gravitational-Wave Observatory and Virgo observatory. The rest, however, contribute to a sort of stochastic background noise.

By measuring this noise, scientists may be able to study much more in the way of events and learn a great deal more about gravitational waves. As Dr Thrane explained in a Monash University press statement:

“Measuring the gravitational-wave background will allow us to study populations of black holes at vast distances. Someday, the technique may enable us to see gravitational waves from the Big Bang, hidden behind gravitational waves from black holes and neutron stars.”

Drs Smith and Thrane are no amateurs when it comes to the study of gravitational waves. Last year, they were both involved in a major breakthrough, where researchers from LIGO Scientific Collaboration (LSC) and the Virgo Collaboration measured gravitational waves from a pair of merging neutron stars. This was the first time that a neutron star merger (aka. a kilonova) was observed in both gravitational waves and visible light.

The pair were also part of the Advanced LIGO team that made the first detection of gravitational waves in September 2015. To date, six confirmed gravitational wave events have been confirmed by the LIGO and Virgo Collaborations. But according to Drs Thrane and Smith, there could be as many as 100,000 events happening every year that these detectors simply aren’t equipped to handle.

In February 2016, LIGO detected gravity waves for the first time. As this artist's illustration depicts, the gravitational waves were created by merging black holes. The third detection just announced was also created when two black holes merged. Credit: LIGO/A. Simonnet.
Artist’s impression of merging binary black holes. Credit: LIGO/A. Simonnet.

These waves are what come together to create a gravitational wave background; and while the individual events are too subtle to be detected, researchers have been attempting to develop a method for detecting the general noise for years. Relying on a combination of computer simulations of faint black hole signals and masses of data from known events, Drs. Thrane and Smith claim to have done just that.

From this, the pair were able to produce a signal within the simulated data that they believe is evidence of faint black hole mergers. Looking ahead, Drs Thrane and Smith hope to apply their new method to real data, and are optimistic it will yield results. The researchers will also have access to the new OzSTAR supercomputer, which was installed last month at the Swinburne University of Technology to help scientists to look for gravitational waves in LIGO data.

This computer is different from those used by the LIGO community, which includes the supercomputers at CalTech and MIT. Rather than relying on more traditional central processing units (CPUs), OzGrav uses graphical processor units – which can be hundreds of times faster for some applications. According to Professor Matthew Bailes, the Director of the OzGRav supercomputer:

“It is 125,000 times more powerful than the first supercomputer I built at the institution in 1998… By harnessing the power of GPUs, OzStar has the potential to make big discoveries in gravitational-wave astronomy.”

What has been especially impressive about the study of gravitational waves is how it has progressed so quickly. From the initial detection in 2015, scientists from Advanced LIGO and Virgo have now confirmed six different events and anticipate detecting many more. On top of that, astrophysicists are even coming up with ways to use gravitational waves to learn more about the astronomical phenomena that cause them.

All of this was made possible thanks to improvements in instrumentation and growing collaboration between observatories. And with more sophisticated methods designed to sift through archival data for additional signals and background noise, we stand to learn a great deal more about this mysterious cosmic force.

Further Reading: Monash, Physical Review X

Kilonova Neutron Star Collision Probably Left Behind a Black Hole

In February of 2016, scientists from the Laser Interferometer Gravitational-Wave Observatory (LIGO) announced the first-ever detection of gravitational waves. A little over a century after they were first predicted by Einstein’s Theory of General Relativity, we finally had proof that this phenomenon existed. In August of 2017, another major breakthrough occurred when LIGO detected waves that were believed to be caused by a neutron star merger.

Shortly thereafter, scientists at LIGO, Advanced Virgo, and the Fermi Gamma-ray Space Telescope were able to determine where in the sky the neutron star merger occurred. While many studies have focused on the by-products of this merger, a new study by researchers from Trinity University, the University of Texas at Austin and Eureka Scientific, has chosen to focus on the remnant, which they claim is likely a black hole.

For the sake of their study, which recently appeared online under the title “GW170817 Most Likely Made a Black Hole“, the team consulted data from the Chandra X-ray Observatory to examine what resulted of the supernova merger. This data was obtained during Director’s Discretionary Time observations that were made on December 3rd and 6th, 2017, some 108 days after the merger.

This data showed a light-curve increase in the X-ray band which was compatible to the radio flux increase that was reported by a previous study conducted by the same team. These combined results suggest that radio and X-ray emissions were being produced at the same source, and that the rising light-curve that followed the merger was likely due to an increase in accelerated charged particles in the external shock – the region where an outflow of gas interacts with the interstellar medium.

As they indicate in their study, this could either be explained as the result of a more massive neutron star being formed from the merger, or a black hole:

“The merger of two neutron stars with mass 1.48 ± 0.12 M and 1.26 ± 0.1 M — where the merged object has a mass of 2.74 +0.04-0.01 M… could result in either a neutron star or a black hole. There might also be a debris disk that gets accreted onto the central object over a period of time, and which could be source of keV X-rays.”

The team also ruled out various possibilities of what could account for this rise in X-ray luminosity. Basically, they concluded that the X-ray photons were not coming from a debris disk, which would have been left over from the merger of the two neutron stars. They also deduced that they would not be produced by a relativistic jet spewing from the remnant, since the flux would be much lower after 102 days.

 

Collisions of neutron stars produce powerful gamma-ray bursts – and heavy elements like gold. Credit: Dana Berry, SkyWorks Digital, Inc.

All of this indicated that the remnant was more likely to be a black hole than a hyper-massive neutron star. As they explained:

“We show next that if the merged object were a hyper-massive neutron star endowed with a strong magnetic field, then the X-ray luminosity associated with the dipole radiation would be larger than the observed luminosity 10 days after the event, but much smaller than the observed flux at t ~ 100 days. This argues against the formation of a hyper-massive neutron star in this merger.”

Last, but not least, they considered the X-ray and radio emissions that were present roughly 100 days after the merger. These, they claim, are best explained by continued emissions coming from the merger-induced shock (and the not remnant itself) since these emissions would continue to propagate in the interstellar medium around the remnant. Combined with early X-ray data, this all points towards GW170817 now being a black hole.

The first-ever detection of gravitational waves signaled the dawn of a new era in astronomical research. Since that time, observatories like LIGO, Advanced Virgo, and GEO 600 have also benefited from information-sharing and new studies that have indicated that mergers are more common than previously thought, and that gravity waves could be used to probe the interior of supernovae.

With this latest study, scientists have learned that they are not only able to detect the waves caused by black hole mergers, but even the creation thereof. At the same time, it shows how the study of the Universe is growing. Not only is astronomy advancing to the point where we are able to study more and more of the visible Universe, but the invisible Universe as well.

Further Reading: LIGO, arXiv

Weekly Space Hangout – Nov. 15, 2017: Dr. John Whelan of RIT

Hosts:
Fraser Cain (universetoday.com / @fcain)
Dr. Paul M. Sutter (pmsutter.com / @PaulMattSutter)
Dr. Kimberly Cartier (KimberlyCartier.org / @AstroKimCartier )
Dr. Morgan Rehnberg (MorganRehnberg.com / @MorganRehnberg ChartYourWorld.org)

Special Guests:
This week we are honored to welcome two (of the numerous) Rochester Institute of Technology faculty members who are part of the LIGO Scientific Collaboration. RIT researchers played a significant role in the recently announced detection of both gravitational waves and light, dubbed Multimessenger Astronomy, that resulted from the merger of two distant neutron stars. Joining us today is Dr. John Whelan, Principal Investigator of RIT’s group in the LIGO Scientific Collaboration (LSC).

Announcements:
The WSH Crew is doing another book giveaway – this time in conjunction with Dean Regas‘ joining us again on November 29th in a pre-recorded interview. Dean’s new book, “100 Things to See in the Night Sky” hits the stores on November 28th, but we are giving our viewers a chance to win one of two copies of Dean’s book! (Note: telescope not included!)

To enter for a chance to win, send an email to [email protected] with the Subject ‘100 Things’. Be sure to include your name and email address in the body of your message so that we can contact our winners afterward.

To be eligible, your entry must be postmarked no later than 11:59:59 PM EST on Monday, November 27, 2017. Two winners will be selected at random from all eligible entries live on the show, by Fraser, on Wednesday, November 29th. No purchase is necessary. You do not need to be watching the show live to win. Contest is open to all viewers worldwide. Limit: One entry per person – duplicate entries will be ignored.

On a side note, THIS awesomeness based on Dean’s FIRST book is now also available:
» 365 Facts from Space! 2018 Daily Calendar

If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!

We record the Weekly Space Hangout every Wednesday at 5:00 pm Pacific / 8:00 pm Eastern. You can watch us live on Universe Today, or the Weekly Space Hangout YouTube page – Please subscribe!

GW170817 Update: Surprises From First Gravitational Wave Observed Independently

“This is quite literally a physics gold mine!” said Masao Sako, with the University of Pennsylvania.

For over a week now, the astronomy and astrophysics communities have been buzzing with the news of the latest gravitational wave discovery. And this discovery has been big.

Four days before the Great American Solar Eclipse on August 21, a newly discovered gravitational wave caused more astronomers (8,223+), using more telescopes (70), to publish more papers (100 — see the list below) in less time than for any other astronomical event in history. The sixth gravitational wave (GW) to be discovered by the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo GW observatories, which occurred on August 17, 2017 at 12:41:04 UTC, was surprising in two ways already reported.

GW event six, designated GW170817, did not result from the collision and subsequent explosion of two black holes. All previous GW events, including the first ever discovered in 2015, had involved the collision of black holes with typically 40 times the mass of the Sun between them. Here however, the GW was evidently triggered by the collision and explosion of two neutron stars, having only 3 times the Sun’s mass in total.

Afterglow of GW170817 is shown in close-ups captured by the NASA Hubble Space Telescope, showing it dimming in brightness over days and weeks. CREDIT: NASA and ESA: A. Levan (U. Warwick), N. Tanvir (U. Leicester), and A. Fruchter and O. Fox (STScI)

Crucially, GW170817 occurred ten times closer to Earth than all earlier GW events. Earlier GWs involved black hole collisions at more than 1.3 billion light-years (400 million parsecs or Mpc). GW170817, in comparison, was known within hours of its discovery to lie within only 130 million light-years (40 Mpc). That vastly improved astronomer’s odds of detecting the event independently, because in cosmological terms, it occurred within less than 1% of the universe’s Hubble length of 14 billion light-years (4,300 Mpc).

Not widely reported is that our current astronomical theory regarding GW170817 still depends significantly on observations yet to be made. In brief, astronomers currently believe that GW170817 was triggered by the merger of two neutron stars, which triggered the explosion of a Short Gamma-Ray Burst (SGRB), which emitted only a fraction of the gamma-ray energy in our direction normally associated with SGRBs, because it was the first SGRB observed at such a large angle away from the direction of its focused jets of gamma-rays. The SGRB associated with GW170817 emitted its jet at roughly 30 degrees away from our line-of-sight. All other SGRBs have been observed at only a few degrees from alignment with their jets. The exact angle of the newly discovered SGRB’s jet is important in understanding how its afterglow compares with other SGRB afterglows. Significant properties reported for the GW, including its distance, depend on the angle at which the two neutron stars collided relative to Earth.

The collision angle determined roughly based on the GW itself is probably OK. Only radio maps of the SGRB region at 100 days however, will provide astronomers with the most precise measurements of the resulting explosion’s velocities and directions over time to date. Only then will astronomers learn more about the exact angle of the SGRB’s jet, providing potentially a more accurate estimate of the angle at which the neutron stars collided. More surprises could be in store as a result, including refinements of the properties reported.

ANIMATION (you may have to click image for animation in some browsers): This time-lapse image of the afterglow of GW170817 shows it continuing to increase in radio wavelength brightness over the first month, and was provided by the National Radio Astronomy Observatory Very Large Array radio telescope. CREDIT: NRAO/VLA

Unlike previous events, GW170817 was close enough that within 1.74 seconds of its initial detection by LIGO, it’s gamma radiation was detected by the Fermi Gamma-Ray space telescope. The INTEGRAL Gamma-Ray space observatory detected it too, and it was later designated SGRB 170817A. As an SGRB alone, the event would have triggered alerts to observatories worldwide and aloft, each aiming to detect the explosion’s faint optical afterglow. SGRB optical afterglows have been used to pinpoint the exact positions of SGRBs, not only on the sky, but also in terms of their distance from Earth.

Astronomers in this case had the first GW ever to coincide with, and be independently corroborated by, any observable counterpart, and alerts became a call to astronomical arms. Even though its exact position on the sky was uncertain by many degrees, GW170817 was so close that astronomers were able to quickly narrow down its exact location.

“With a previously-compiled list of nearby galaxies having positions and distances culled from the massive on-line archive of the NASA/IPAC Extragalactic Database (NED), our team rapidly zeroed in on the host galaxy of the event,” said Barry Madore, of Carnegie Observatories.

Precisely because GW170817 occurred at only 130 million light-years, the number of candidate galaxies to observe was only several dozen. In contrast, for previous GW discoveries occurring at billions of light-years, thousands of galaxies would have to be observed. Within 11 hours of the explosion, its afterglow was discovered in the lenticular galaxy NGC 4993, by the Swope 1-m telescope in Chile. They obtained the first-ever visual image of an event associated with a GW.

“Where observation is concerned, chance favors only the prepared mind,” added Madore, quoting Louis Pasteur from 150 years ago. Madore is also a researcher with the Swope team and a co-author on six papers reporting Swope’s discovery of the afterglow and some of its implications. “When alerts were sent out to the LIGO/VIRGO gravity wave detection consortium on the night of August 17, 2017, our team of astronomers was indeed prepared.”

New images of the afterglow of GW170817, aka SGRB 170817A, initially designated as Swope Supernova Survey SSS17a, revealed a bright blue astronomical transient, later designated as AT2017gfo by the International Astronomical Union (IAU).

“There will be more such events, no doubt; but this image taken at the Henrietta Swope 1m telescope at the Las Campanas Observatory in Chile was the first in history, and it truly ushered in the Era of Multi-Messenger Astronomy,” said Madore.

Radio observatories joined the hunt, including the Karl G. Jansky Very Large Array (VLA), the Australia Telescope Compact Array (ATCA) and the Giant Metrewave Radio Telescope (GMRT). So did the Swift ultraviolet and Chandra X-ray space observatory satellites. By day one after the explosion, all frequencies of the electromagnetic spectrum were being observed in the direction of NGC 4993. On multiple wavelengths, multiple “messengers” of GW170817’s existence began to reveal more than the sum of their parts.

Change in brightness of GW170817’s afterglow over time since explosion (merger), is shown in these light-curves. Brightness in 14 different optical wavelengths is shown, including invisible ultraviolet, and visible blue, green, and yellow, and invisible infrared wavelengths in orange and red. Afterglow fades quickly in all wavelengths, except infrared. In infrared, afterglow continues to brighten until ~3 days after explosion, before beginning to fade. CREDIT: Las Campanas Observatory, Carnegie Institution of Washington (Swope + Magellan)

AT2017gfo brightened over the next few days after explosion, in near infrared observations continued by Swope. Their light-curves show the changes in the afterglow’s brightness over time. At three days post explosion, the near-infrared afterglow stops brightening and begins to fade. As with other SGRB afterglows, AT2017gfo faded completely from visual observation over the course of days to weeks, but observations in X-rays and radio continue. Radio observations at 100 days post explosion, which will not occur until November 25, are crucial as said. Although a month away, planned radio observations will determine more than just the long-term evolution of the afterglow over 3 months. Indeed, our astronomical theory accounting for the event’s first three weeks, as already observed, analyzed, and reported, still depends to a surprising degree on an exact number of degrees. The number of degrees relative to Earth for this SGRB based on radio data however, will not be known for at least a month.

“With GW170817 we have for the first time truly independent verification of a gravitational wave source,” said Robert Quimby, of the Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo, and coauthor of a paper regarding the event’s implications. “The electromagnetic signature of this event can be uniquely matched to the predictions of binary neutron star mergers, and it is actually quite amazing how well the theory matches the data considering how few observational constraints were available to guide the model.”

“With GW170817, we can learn about nuclear physics, relativity, stellar evolution, and cosmology all in one shot,” added Sako, who is also a co-author on ten papers regarding the event. “Plus we now know how all of the heaviest elements in the Universe are created.”

Afterglow faded from optical observations over days to weeks. Here, however, as observed at radio frequencies by the Very Large Array radio telescope, the electromagnetic counterpart to GW170817 is seen brightening over the first month since explosion. CREDIT: Courtesy of Gregg Hallinan, California Institute of Technology, and the National Radio Astronomy Observatory Very Large Array radio telescope

EVENT CHRONOLOGY

T = 0 sec.: GW170817 detected by LIGO/VIRGO [1, 82]
T = 1.74 sec.: SGRB 170817A detected by Fermi Gamma-Ray Burst Monitor satellite immediately after GW170817 [52]
T = 28 min.: Gamma-ray Coordinates Network (GCN) Notice [53]
T = 40 min.: GCN Circular [53]
T = 5.63 hr.: First sky map locating GW170817 to within several degrees [53]
T = 10.9 hr.: Swope 1-m observatory discovers explosion’s afterglow, AT 2017gfo, in galaxy NGC 4993 [18, 24, 64, 75, 77]
T = 11.09 hr.: PROMPT 0.4m observatory detects AT 2017gfo [88]
T = 11.3 hr.: Hubble Space Telescope images AT 2017gfo [20]
T = 12-24 hr.: Magellan; Las Campanas Observatory; W. M. Keck Observatory; Blanco 4-m Cerro Tololo Inter-American Observatory; Gemini South; European Southern Observatory VISTA; Subaru among 6 Japanese telescopes; Pan-STARRS1; Very Large Telescope; 14 Australian telescopes; and Antarctic Survey Telescope optical observatories, and VLA, VLITE, ATCA, GMRT, and ALMA radio observatories, as well as Swift and NuSTAR ultraviolet satellite observatories

PROPERTIES

Position: Right Ascension 13h09m48.085s ± 0.018s; Declination -23d22m53.343s ± 0.218s (J2000 equinox); 10.6s or 7,000 light-years (2.0 kiloparsecs or kpc) from the nucleus of lenticular galaxy NGC 4993 [18]
Distance: 140 ± 40 million light-years (41 ± 13 Mpc), with 30% scatter based on 3 GW-based estimates [1, 25, 82], and 131 ± 9 million light-years (39.3 ± 2.7 Mpc), with 7% scatter based on 3 distance indicators, including GW-based as well as new Fundamental Plane relation-based distances for NGC 4993 [41, 43], and Tully-Fisher relation-based distances for galaxies in the group of galaxies including NGC 4993 from the NASA/IPAC Extragalactic Database (NED)
Mass: Neutron stars total 2.82 +0.47 -0.09 Sun’s mass [82]; mass ejected in elements heavier than iron is 0.03 ± 0.01 Sun’s mass or 10,000 Earth masses, based on 4 estimates [24, 59, 82, 93], including gold amounting to 150 ± 50 Earth masses [60]
Luminosity: Peaks at 0.5 days after explosion, at ~1042 erg/s, equivalent to 260 million Suns [24]
SGRB jet angle: 31 ± 3 degrees away from line-of-sight to Earth, based on 9 estimates [2, 25, 34, 35, 36, 44, 58, 62, 82]
SGRB jet speed: 30% speed of light, based on 4 estimates [20, 42, 59, 75]
Names: GW170817, SGRB 170817A, AT 2017gfo = IAU designation for SGRB afterglow, aka SSS17a, DLT17ck, J-GEM17btc, and MASTER OTJ130948.10-232253.3

IMPLICATIONS

Astronomy (1): Confirms binary neutron star collisions as a source for GW and SGRB events [1, 82]
Astronomy (2): GWs provide a new way of measuring neutron star diameters [8]
Astronomy (3): Gives universal expansion rate, or Hubble constant, as H0 = 71 ± 10 km -1 Mpc-1, with 14% accuracy, based on 6 GW-based estimates for GW170817 ranging from 69 to 74 km -1 Mpc-1, bridging current estimates [1, 22, 36, 60, 74, 82]; accuracy will improve to 4% with future similar events [74]
General Relativity (1): Confirms GW velocity equals speed of light to within 1 part per 1,000,000,000,000,000 or 1/1015 [7, 21, 70, 91]
General Relativity (2): Confirms equivalence of gravitational energy and inertial energy, or Weak Equivalence Principle, to within 1 part per 1,000,000,000 or 1/109 [7, 11, 91, 92]
Physics: Confirms binary neutron star collisions are significant production sites for elements heavier than iron, including gold, platinum, and uranium [17, 69]
Life on Earth: Indicates a higher deadly rate of gamma-rays for extraterrestrial life [15]
GW170817 (1): Predicted one binary neutron star collision per year similar to GW170817 within a distance from Earth of 130 million light-years [40 Mpc] [24]
GW170817 (2): Predicted to produce a 10 Giga-Hertz afterglow that peaks at ~100 days with a radio magnitude of ~10 milli-Janskys [24]
GW170817 (3): Predicted to remain visible in radio for 5-10 years, and for decades with next-generation radio observatories [2]

BIBLIOGRAPHY

96 papers on GW170817 released on arXiv during week of October 16-20

1. Abbott, B. P. et al., A gravitational-wave standard siren measurement of the Hubble constant, Nature, arXiv:1710.05835
2. Alexander, K. D. et al., The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. VI. Radio Constraints on a Relativistic Jet and Predictions for Late-Time Emission from the Kilonova Ejecta, ApJL, arXiv:1710.05457
3. Andreoni, I. et al., Follow up of GW170817 and its electromagnetic counterpart by Australian-led observing programs, PASA, arXiv:1710.05846
4. ANTARES, IceCube, Pierre Auger, LIGO Scientific, Virgo Collaborations, Search for High-energy Neutrinos from Binary Neutron Star Merger GW170817 with ANTARES, IceCube, and the Pierre Auger Observatory, na, arXiv:1710.05839
5. Arcavi, I. et al., Optical emission from a kilonova following a gravitational-wave-detected neutron-star merger, Nature, arXiv:1710.05843
6. Arcavi, I. et al., Optical Follow-up of Gravitational-wave Events with Las Cumbres Observatory, ApJL, arXiv:1710.05842
7. Baker, T. et al., Strong constraints on cosmological gravity from GW170817 and GRB 170817A, na, arXiv:1710.06394
8. Bauswein, A. et al., Neutron-star radius constraints from GW170817 and future detections, ApJL, submitted, arXiv:1710.06843
9. Belczynski, K. et al., GW170104 and the origin of heavy, low-spin binary black holes via classical isolated binary evolution, A&A, arXiv:1706.07053
10. Blanchard, P. K. et al., The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. VII. Properties of the Host Galaxy and Constraints on the Merger Timescale, ApJL, arXiv:1710.05458
11. Boran, S. et al., GW170817 Falsifies Dark Matter Emulators, na, arXiv:1710.06168
12. Brocato, E. et al., GRAWITA: VLT Survey Telescope observations of the gravitational wave sources GW150914 and GW151226, MNRAS, submitted, arXiv:1710.05915
13. Bromberg, O. et al., The gamma-rays that accompanied GW170817 and the observational signature of a magnetic jet breaking out of NS merger ejecta, MNRAS, arXiv:1710.05897
14. Buckley, D. A. H. et al., A comparison between SALT/SAAO observations and kilonova models for AT 2017gfo: the first electromagnetic counterpart of a gravitational wave transient – GW170817, MNRAS, arXiv:1710.05855
15. Burgess, J. M. et al., Viewing short Gamma-ray Bursts from a different angle, na, arXiv:1710.05823
16. Chang, P.; & Murray, N., GW170817: A Neutron Star Merger in a Mass-Transferring Triple System, MNRAS Letters, arXiv:1710.05939
17. Chornock, R. et al., The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. IV. Detection of Near-infrared Signatures of r-process Nucleosynthesis with Gemini-South, ApJL, arXiv:1710.05454
18. Coulter, D. A. et al., Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source, Science, arXiv:1710.05452
19. Covino, S. et al., The unpolarized macronova associated with the gravitational wave event GW170817, Nature Astronomy, arXiv:1710.05849
20. Cowperthwaite, P. S. et al., The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. II. UV, Optical, and Near-IR Light Curves and Comparison to Kilonova Models, ApJL, arXiv:1710.05840
21. Creminelli, P.; & Vernizzi, F., Dark Energy after GW170817, na, arXiv:1710.05877
22. Di Valentino, E.; & Melchiorri, A., Cosmological constraints combining Planck with the recent gravitational-wave standard siren measurement of the Hubble constant, na, arXiv:1710.06370
23. Diaz, M.C. et al., Observations of the first electromagnetic counterpart to a gravitational wave source by the TOROS collaboration, ApJL, arXiv:1710.05844
24. Drout, M. R. et al., Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis, Science, arXiv:1710.05443
25. Evans, P.A. et al., Swift and NuSTAR observations of GW170817: detection of a blue kilonova, Science, arXiv:1710.05437
26. Ezquiaga, J. M.; & Zumalacarregui, M., Dark Energy after GW170817, na, arXiv:1710.05901
27. Fargion, D.; Khlopov, M.; & Oliva, P., Could GRB170817A be really correlated to a NS-NS merging?, Research in Astron. Astrophys. , arXiv:1710.05909
28. Fermi-LAT Collaboration, Fermi-LAT observations of the LIGO/Virgo event GW170817, na, arXiv:1710.05450
29. Fong, W. et al., The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. VIII. A Comparison to Cosmological Short-duration Gamma-ray Bursts, ApJL, arXiv:1710.05438
30. Gall, C. et al., Lanthanides or dust in kilonovae: lessons learned from GW170817, ApJL, arXiv:1710.05863
31. Goldstein, A. et al., An Ordinary Short Gamma-Ray Burst with Extraordinary Implications: Fermi-GBM Detection of GRB 170817A, ApJL, arXiv:1710.05446
32. Gompertz, B. P. et al., The Diversity of Kilonova Emission in Short Gamma-Ray Bursts, ApJ, submitted, arXiv:1710.05442
33. Gottlieb, O. et al., A cocoon shock breakout as the origin of the ?-ray emission in GW170817, MNRAS, arXiv:1710.05896
34. Granot, J.; Guetta, D.; & Gill, R., Lessons from the short GRB170817A — the First Gravitational Wave Detection of a Binary Neutron Star Merger, na, arXiv:1710.06407
35. Granot, J. et al., Off-Axis Emission of Short GRB Jets from Double Neutron St.r Mergers and GRB 170817A, MNRAS, arXiv:1710.06421
36. Guidorzi, C. et al., Improved Constraints on H0 from a combined analysis of gravitational-wave and electromagnetic emission from GW170817, ApJL, submitted, arXiv:1710.06426
37. H.E.S.S. Collaboration et al., TeV gamma-ray observations of the binary neutron star merger GW170817 with H.E.S.S, ApJL, submitted, arXiv:1710.05862
38. Haggard, D. et al., A Deep Chandra X-ray Study of Neutron Star Coalescence GW170817, ApJL, arXiv:1710.05852
39. Hallinan, G. et al., A Radio Counterpart to a Neutron Star Merger, Science, arXiv:1710.05435
40. He, X.-B.; Tam, P-H. T.; & Shen, R. F.), GRB 170817A: a short GRB seen off-axis, MNRAS, arXiv:1710.05869
41. Hjorth, J. et al., The Distance to NGC 4993: The Host Galaxy of the Gravitational-wave Event GW170817, ApJL, arXiv:1710.05856
42. Hu, L. et al., Optical Observations of LIGO Source GW 170817 by the Antarctic Survey Telescopes at Dome A, Antarctica, Science Direct, arXiv:1710.05462
43. Im, M. et al., Distance and properties of NGC 4993 as the host galaxy of a gravitational wave source, GW170817, ApJL, arXiv:1710.05861
44. Ioka, K.; & Nakamura, T., Can an Off-axis Gamma-Ray Burst Jet in GW170817 Explain All the Electromagnetic Counterparts?, Prog. Theor. Exp. Phys. , arXiv:1710.05905
45. Kasen, D. et al., Origin of the heavy elements in binary neutron-star mergers from a gravitational wave event, Nature, arXiv:1710.05463
46. Kasliwal, M. M. et al., Illuminating Gravitational Waves: A Concordant Picture of Photons from a Neutron Star Merger, Science, arXiv:1710.05436
47. Kilpatrick, C. D. et al., Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger, Science, arXiv:1710.05434
48. Kim, S. et al., ALMA and GMRT constraints on the off-axis gamma-ray burst 170817A from the binary neutron star merger GW170817, na, arXiv:1710.05847
49. Lamb, G. P.; & Shiho Kobayashi, GRB 170817A as a jet counterpart to gravitational wave trigger GW 170817, MNRAS, arXiv:1710.05857
50. Levan, A. J. et al., The environment of the binary neutron star merger GW170817, ApJL, arXiv:1710.05444
51. Li, T.-P. et al., Insight-HXMT observations of the first binary neutron star merger GW170817, Sci. China-Phys. Mech. Astron. , arXiv:1710.06065
52. LIGO Scientific Collaboration, Virgo Collaboration, Fermi Gamma-Ray Burst Monitor, INTEGRAL, Gravitational Waves and Gamma-rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A, ApJL, arXiv:1710.05834
53. LIGO Scientific Collaboration, Virgo Collaboration, et al., Multi-messenger Observations of a Binary Neutron Star Merger, ApJL, arXiv:1710.05833
54. Lipunov, V. M. et al., MASTER optical detection of the first LIGO/Virgo neutron stars merging GW170817, ApJL, arXiv:1710.05461
55. Lipunov, V. et al., Discovery of the neutron stars merger GW170817/GRB170817A and Binary Stellar Evolution, New Astronomy Review, arXiv:1710.05911
56. Lu, R.-J. et al., {\em Fermi}/GBM Short Gamma-ray Burst Catalog and Case Study for GRB 170817A/GW 170817, na, arXiv:1710.06979
57. Margalit, B.; & Metzger, B., Constraining the Maximum Mass of Neutron Stars From Multi-Messenger Observations of GW170817, ApJL, submitted, arXiv:1710.05938
58. Margutti, R. et al., The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. V. Rising X-ray Emission from an Off-Axis Jet, ApJL, arXiv:1710.05431
59. McCully, C. et al., The Rapid Reddening and Featureless Optical Spectra of the optical counterpart of GW170817, AT 2017gfo, During the First Four Days, ApJL, arXiv:1710.05853
60. Metzger, B. D. , Welcome to the Multi-Messenger Era! Lessons from a Neutron Star Merger and the Landscape Ahead, na, arXiv:1710.05931
61. Murguia-Berthier, A. et al., A Neutron Star Binary Merger Model for GW170817/GRB170817a/SSS17a, ApJL, arXiv:1710.05453
62. Nicholl, M. et al., The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/VIRGO GW170817. III. Optical and UV Spectra of a Blue Kilonova From Fast Polar Ejecta, ApJL, arXiv:1710.05456
63. Palmese, A. et al., DECam and DES perspective of the GW170817 host, NGC 4993: indication for dynamically-driven formation of binary neutron star in early type galaxies, na, arXiv:1710.06748
64. Pan, Y.-C. et al., The Old Host-Galaxy Environment of SSS17a, the First Electromagnetic Counterpart to a Gravitational Wave Source, ApJL, arXiv:1710.05439
65. Paul, D., Binary neutron star merger rate via the luminosity function of short gamma-ray bursts, MNRAS, arXiv:1710.05620
66. Pian, E. et al., Spectroscopic identification of r-process nucleosynthesis in a double neutron star merger, Nature, arXiv:1710.05858
67. Piro, A. L.; & Kollmeier, J. A., Evidence for Cocoon Emission from the Early Light Curve of SSS17a, na, arXiv:1710.05822
68. Pozanenko, A. et al., GRB170817A associated with GW170817: multifrequency observations and modeling of prompt gamma-ray emission, ApJL, submitted, arXiv:1710.05448
69. Rosswog, S. et al., The first direct double neutron star merger detection: implications for cosmic nucleosynthesis, A&A, accepted?, arXiv:1710.05445
70. Sakstein, J.; & Jain, B., Implications of the Neutron Star Merger GW170817 for Cosmological Scalar-Tensor Theories, na, arXiv:1710.05893
71. Salafia, O. S.; Ghisellini, G.; & Ghirlanda, G., Jet-driven and jet-less fireballs from compact binary mergers, MNRAS Letters, arXiv:1710.05859
72. Savchenko, V. et al., INTEGRAL Detection of the First Prompt Gamma-Ray Signal Coincident with the Gravitational Wave Event GW170817, ApJL, arXiv:1710.05449
73. Scolnic, D. et al., How Many Kilonovae Can Be Found in Past, Present, and Future Survey Datasets?, ApJL, submitted, arXiv:1710.05845
74. Seto, N.; & Kyutoku, K., Prospects of the local Hubble parameter measurement using gravitational waves from double neutron stars, MNRAS, arXiv:1710.06424
75. Shappee, B. J. et al., Early Spectra of the Gravitational Wave Source GW170817: Evolution of a Neutron Star Merger, Science, arXiv:1710.05432
76. Shoemaker, I. M.; & Murase, K., Constraints from the Time Lag between Gravitational Waves and Gamma Rays: Implications of GW 170817 and GRB 170817A, na, arXiv:1710.06427
77. Siebert, M. R. et al., The Unprecedented Properties of the First Electromagnetic Counterpart to a Gravitational Wave Source, ApJL, arXiv:1710.05440
78. Smartt, S. J. et al., A kilonova as the electromagnetic counterpart to a gravitational-wave source, Nature, arXiv:1710.05841
79. Soares-Santos, M. et al., The Electromagnetic Counterpart of the Binary Neutron Star Merger LIGO/Virgo GW170817. I. Dark Energy Camera Discovery of the Optical Counterpart, ApJL, arXiv:1710.05459
80. Tanaka, M. et al., Kilonova from post-merger ejecta as an optical and near-infrared counterpart of GW170817, PASJ, arXiv:1710.05850
81. Tanvir, N. R. et al., The Emergence of a Lanthanide-Rich Kilonova Following the Merger of Two Neutron Stars, na, arXiv:1710.05455
82. The LIGO Scientific Collaboration, The Virgo Collaboration, GW170817: Observation of Gravitational Waves from a Binary Neutron Star Inspiral, Phys. Rev. Lett., arXiv:1710.05832
83. The LIGO Scientific Collaboration, the Virgo Collaboration, Estimating the Contribution of Dynamical Ejecta in the Kilonova Associated with GW170817, ApJL, arXiv:1710.05836
84. The LIGO Scientific Collaboration, the Virgo Collaboration, On the Progenitor of Binary Neutron Star Merger GW170817, ApJL, arXiv:1710.05838
85. Tominaga, N. et al., Subaru Hyper Suprime-Cam Survey for An Optical Counterpart of GW170817, PASJ, submitted, arXiv:1710.05865
86. Troja, E. et al., The X-ray counterpart to the gravitational wave event GW 170817, Nature, arXiv:1710.05433
87. Utsumi, Y. et al., J-GEM observations of an electromagnetic counterpart to the neutron star merger GW170817, PASJ, arXiv:1710.05848
88. Valenti, S. et al., The discovery of the electromagnetic counterpart of GW170817: kilonova AT 2017gfo/DLT17ck, ApJL, arXiv:1710.05854
89. Verrecchia, F. et al., AGILE Observations of the Gravitational Wave Source GW 170817: Constraining Gamma-Ray Emission from a NS-NS Coalescence, ApJL, submitted, arXiv:1710.05460
90. Wang, F. Y.; & Zou, Y. C., Measuring peculiar velocities from gravitational waves and electromagnetic counterparts, na, arXiv:1710.06113
91. Wang, H. et al., GW170817/GRB 170817A/AT2017gfo association: some implications for physics and astrophysics, na, arXiv:1710.05805
92. Wei, J.-J. et al., Multimessenger tests of the weak equivalence principle from GW170817 and its electromagnetic counterparts, na, arXiv:1710.05860
93. Xiao, D. et al., Afterglows and Macronovae Associated with Nearby Low-Luminosity Short-Duration Gamma-Ray Bursts: Application to GW170817/GRB170817A, na, arXiv:1710.05910
94. Yang, S. et al., An empirical limit on the kilonova rate from the DLT40 one day cadence Supernova Survey, ApJL, submitted, arXiv:1710.05864
95. Yue, C. et al., Is GRB 170817A Alone?, na, arXiv:1710.05942
96. Zhang, B.-B. et al., A peculiar low-luminosity short gamma-ray burst from a double neutron star merger progenitor, na, arXiv:1710.05851