Astronomers announced today that they had discovered something new out in the dark: a stellar corpse too heavy to be a neutron star — the remnant of a supernova explosion — but not heavy enough to be a black hole.
Whatever it once was, it is long gone. About 780 million years ago — and 780 light-years away — it was eaten by a black hole 23 times more massive than the sun. That feast left behind an even heavier black hole — a vast, hungry nothing with the mass of 25 suns.
News of that event only recently reached Earth, in the form of space-time ripples known as gravitational waves. These evanescent vibrations were felt on Aug. 14, 2019, by an array of antennas in Italy and the United States called the International LIGO-Virgo Collaboration, and the results were published on Tuesday in Astrophysical Journal Letters.
According to a theory that has been the backbone of decades of astrophysical excitement, a star can wind up in one of three final states, depending on its mass: a perpetually cooling cinder known as a white dwarf; a dense star, with the mass of a couple of suns compressed into a ball only 12 or so miles wide, known as a neutron star; or a black hole, a beast reluctantly predicted by Albert Einstein to be so dense that nothing, not even light, can escape its gravity.
The victim in this collision weighed in at 2.6 solar masses, according to the LIGO-Virgo calculations. That is heavier than the accepted limit of 2.5 suns for a neutron star. But the lightest black hole ever measured was about five solar masses.
So the mystery object lies squarely in what astrophysicists call the “mass gap.” Astronomers have long wondered what, if anything, could occupy this astronomical no-man’s land.
“We’ve been waiting decades to solve this mystery” Vicky Kalogera of Northwestern University, one of the main authors of the paper, said in an interview. “We don’t know if this object is the heaviest known neutron star or the lightest known black hole, but either way it breaks a record.”
She added: “If it’s a neutron star, it’s an exciting neutron star. If it’s a black hole, it’s an exciting black hole.”
In a statement issued by the Science and Technology Facilities Council in Britain, Charlie Hoy, a graduate student at Cardiff University and Dr. Kalogera’s co-author, said, “I did not believe the alert when I first saw it come through.”
The LIGO observatory made history in 2016 when it detected gravitational waves from a pair of colliding black holes, proving the existence both of gravitational waves, a century after Einstein predicted them, and of black holes. The instrument consists of twin L-shaped antennas in Hanford, Wash., and Livingston, La.
Since then, LIGO has been joined in its exploration of the darkness by another antenna known as Virgo, in Cascina, Italy. The combined LIGO-Virgo Collaboration consists of about 2,000 scientists around the world. The alphabetical listing of their names and institutions takes up the first five and a half pages of the new paper.
The puzzling collision recorded last August was one of 56 possible gravitational wave events — most of which appear to be black hole collisions — detected during the observatory’s third run, which went from April 2019 until March 2020, when the coronavirus pandemic shut down most scientific activities around the world. The collaboration is still reviewing the data in an effort to analyze and confirm them.
Dr. Kalogera said that the event was exciting for several reasons. The ratio of the two colliding masses was the most extreme — nine to one — of the gravitational wave collisions that have been observed so far. Astronomers have difficulty imagining how such unmatched stars could get together in a binary double-star system to begin with.
“This is very hard for formation theories to explain,” she said.
The signal — a characteristic “chirp” caused by the colliding objects circling faster and faster as they approach their moment of ultimate doom — lasted about 10 seconds. “Due to the favorable circumstance of having observed such a loud signal with quite different component masses and for about 10 seconds, we achieved the most precise gravitational-wave measurement of a black hole spin to date,” Alessandra Buonanno, of the Albert Einstein Institute in Potsdam, Germany, said in a statement issued by the institute’s arm in Hannover, Germany.
A black hole’s spin carries important information about the birth and evolution of the black hole, Dr. Buonanno noted. In this case, it revealed that the black hole was spinning “rather slowly,” less than one-tenth the rate allowed by the strictures of Einstein’s theory.
Nobody had any immediate explanation or candidate for what kind of entity could fill this mass gap — a “dearth,” Dr. Kalogera called it — except to affirm that the calculations were robust.
Gordon Baym, an expert on neutron stars at the University of Illinois, pointed out that the collision of a pair of neutron stars in 2017, which produced a cosmic fireworks spectacle, left behind a neutron star with about 2.7 solar masses, thus briefly occupying the mass gap. But that object is thought to have collapsed into a black hole almost immediately.
Most well-measured neutron stars have masses of around 1.4 suns, Dr. Baym said, and only a handful have masses more than two. In theoretical calculations, he said, “it is very hard to make matter stiff enough, using reasonable physics,” to conjure a neutron star in the range of 2.6 solar masses.
Daniel Holz, an astronomy professor at the University of Chicago who is a member of the LIGO collaboration, but not one of the principal authors of this paper, mused that neutron stars and black holes are in some sense “polar opposites.”
“A neutron star is composed of the densest matter in the universe, and is in some sense the ultimate star,” he said in an email. “A black hole is just warped space and time. It doesn’t even have a physical surface! And the interior of a black hole is in some sense not even part of our universe, since nothing can come out of it.”
He added: “What is astounding is that, despite their profound differences, in this particular case we can’t tell which is which!” All the clues disappeared into the resultant black hole.
“So we’re not sure if this object is a neutron star or a black hole, and either way it’s exciting and we learn something new,” Dr. Holz said. “It’s a win-win! Lots of theorists are now sharpening their pencils to try to explain what we’ve seen.”
What’s Happening with Betelgeuse? Astronomers Propose a Specialized Telescope to Watch the Star Every Night – Universe Today
Starting in late 2019, Betelgeuse began drawing a lot of attention after it mysteriously started dimming, only to brighten again a few months later. For a variable star like Betelgeuse, periodic dimming and brightening are normal, but the extent of its fluctuation led to all sorts of theories as to what might be causing it. Similar to Tabby’s Star in 2015, astronomers offered up the usual suspects (minus the alien megastructure theory!)
Whereas some thought that the dimming was a prelude to the star becoming a Type II supernova, others suggested that dust clouds, enormous sunspots, or ejected clouds of gas were the culprit. In any case, the “Great Dimming of Betelgeuse” has motivated an international team of astronomers to propose that a “Betelgeuse Scope” be created that cant monitor the star constantly.
The paper that outlines their proposal was recently presented at the International Society for Optics and Photonics (SPIE) Optical Engineering + Applications 2020, a virtual conference that took place from Aug. 24th to Sept. 4th. The paper, “Betelgeuse scope: single-mode-fibers-assisted optical interferometer design for dedicated stellar activity monitoring,” is also available online as part of the Proceedings of SPIE, Vol. 11490.
To recap, Betelgeuse is a red giant star that is about 12 times as massive as our Sun and about 900 times as large. It is located about 700 light-years from Earth in the Orion constellation and is easily spotted by looking for “the Hunter’s” left shoulder. Ordinarily, Betelgeuse is the second-brightest star in Orion (after Rigel) and the tenth-brightest star in the night sky.
Starting in November of 2019, the star began to dim rather suddenly, reaching a historical minimum of just 37% of its average brightness by Feb. 10th, 2020. At this point, Betelgeuse began to brighten until the end of May, at which point the dimming started all over again. For the sake of their article, the team explored different theories as to what caused the dimming.
This included the “Dark Spots hypothesis,” which was based on submillimeter observations taken by the James Clerk Maxwell Telescope and Atacama Pathfinder Experiment. Then there’s the “Dust formation and blocking hypothesis,” which is based on observations conducted with the VLT/SPHERE and the Hubble Space Telescope that suggest that there was a mass ejection from a large convective cell in the photosphere.
According to the authors, all of these possibilities can be investigated by observing the change of Betelgeuse’s angular diameter accurately. In order to do this, telescopes that are capable of conducting high-angular resolution observations (such as optical interferometry) would be needed. In this process, visible light is gathered by two or more telescopes and then combined to obtain higher-resolution images.
As they state in their study, today’s optical telescope facilities are not optimized for the kind of time-evolution monitoring that would be needed. In short, conducting this type of campaign would mean committing observation time from multiple facilities, which is a very expensive prospect. For this reason, the team recommends that a telescope be commissioned for the task.
As Dr. Narsireddy Anugu, a Prize Fellow in Astronomical Instrumentation and Technology at the University of Arizona’s Steward Observatory and the lead author on the study, explained to Universe Today via email:
“High-angular observations are required to image any existing dark spots on the Betelgeuse’s surface and ‘rogue’ convection cells. Collaborators [are also needed], and we have been taken some data with the Very Large Telescope Interferometer at Paranal, Chile (led by M. Montarges) and the CHARA array at the Mount Wilson Observatory. We are currently working on image reconstruction of interferometry data to reveal any dark spots and convection cells on the Betelgeuse surface.”
As they describe it, this “Betelgeuse Scope” will leverage advancements made in the field of optical interferometry and the telecommunication industry. It will consist of an array of 12 x 4 inch Cassegrain-reflector optical telescopes, which will be mounted to the surface of a large radio dish, which will allow for snapshot imaging of convection cells and time-evolution monitoring. As Dr. Anugu described it:
“We have proposed a unique six telescope interferometer concept installing on a radio antenna. This concept aims at a low budget by cutting the costs of pointing and tracking of each individual telescope using the already existing pointing and tracking of the radio antenna. Another benefit of installing the telescope array on a common mount is that we don’t need longer delay lines as in the classical non-common mount based long-baseline interferometers. Where an active compensation of changing the geometrical delay is required between the wavefronts reaching any two telescopes.”
Polarization-maintaining single-mode optical fibers will then carry the coherent beams from the individual optical telescopes to a central beam-combining facility. To compensate for atmospheric turbulence, vibrations, and pointing errors caused by windy conditions, the team recommends a fast steering mirror, a standard tip-tilt correction system, a fast frame rate detector, and a metrology laser system to measure vibrations.
In addition to being able to monitor Betelgeuse and resolve the mystery of its dimming, the Betelgeuse Scope will also allow for significant advancements in the field of astronomy. Said Dr. Anugu:
“Our proposed telescope monitors the Betelgeuse every-night with high-angular resolutions, makes a movie of motion of dynamic convection activity on the surface. This way, we will probe future mysterious dimming events such as 2019-2020 and origins of the dust formation around the Betelgeuse.”
At present, Anugu and his team are building a prototype of their proposed telescope, which will be mounted on the University of Arizona’s 6-meter (~20 foot) radio dish. So far, they have procured one set of light-collecting and fiber injection optics (12 are needed overall) and are integrating them into their lab at the Steward Observatory. They anticipate that the prototype will be finished and ready to be installed by the end of the year.
“Our proposed concept is straight forward, but we are building a pathfinder to test them,” said Dr. Anugu. “Once successful, we reuse the same optics and actuators for the actual 12-m radio antenna, and 12 telescope interferometer array as this concept is scalable and modular.”
Further Reading: arXiv
Elon Musk's SpaceX gets CRTC application approval for Starlink satellite internet – CTV News
Space Exploration Technologies Corp, better known as SpaceX, moved closer to launching its high-speed satellite internet service in Canada after the Canadian Radio-television and Telecommunications Commission approved the company’s application for a licence.
SpaceX, founded by Elon Musk, applied for a Basic International Telecommunications Services (BITS) licence in May. The approval for the application was granted last week, according to a letter to the company posted on the CRTC website.
A BITS licence authorizes telecommunications providers or carriers to carry international telecommunications traffic between Canada and any other country.
The CRTC said it received 2,585 interventions regarding the application and approved the application after considering all the comments received. Interventions are submissions by the public on whether they support or oppose the issue in question and why, or if they would simply like to make a comment. The application garnered significant support from rural Canadians who lack reliable, fast, and affordable internet service in remote parts of the country.
Musk tweeted earlier this month that Starlink would be “revolutionary” for remote regions and in emergency services situations where landlines are damaged.
The Commission noted in its approval letter to SpaceX that the “BITS licence does not by itself authorize an entity to operate as a facilities-based carrier or non-facilities based service provider,” adding that a carrier or service provider must comply with regulatory requirements, including those around ownership and control.
Starlink, the internet service SpaceX is launching, is made up of a constellation of low-Earth orbit satellites. The company already has U.S. FCC approval to launch thousands of satellites and has a goal to launch tens of thousands more. There are more than 800 Starlink satellites in orbit now.
According to the Starlink website, it was targeting service in the northern part of the United States and Canada this year, and aiming for a rapid expansion “to near global coverage of the populated world by 2021.”
There has been some criticism about SpaceX and other similar types of initiatives, however, due to concerns including space debris and light pollution.
Several astronomical organizations had previously issued public statements of concern on the light pollution caused by these satellite constellations, which they say impacts scientific observations. Earlier this year the company said it was introducing sunshades that would help reduce the brightness and solar reflection from its satellites. Musk said in a tweet that it will become “increasingly difficult to see Starlink satellites, as we are actively working with the astronomer community to ensure that even the most sensitive telescopes are fine & scientific progress is not impeded.”
To address space debris concerns, Starlink said on its website that its satellites have an on-board propulsion system that would allow it to eventually deorbit at the end of life and should that method not work, the satellites would burn within one to five years in the Earth’s atmosphere.
NASA’s OSIRIS-REx poised to reach out and touch an asteroid – Al Jazeera English
Imagine having to parallel park a 15-passenger van in a narrow parking spot surrounded by two-storey boulders. Then imagine doing it on an asteroid hurtling through outer space at speeds of more than 62,700 miles per hour (101,000 km/h).
On Tuesday, a mission led by US space agency NASA and a team of researchers from the University of Arizona in the United States will do just that, sending commands to a small spacecraft more than 200 million miles (321.9 million kilometres) away, and guiding OSIRIS-REx to vacuum up bits of an asteroid named Bennu and bring them back to Earth. Inside those samples could be clues about the origins of life itself.
Four years ago, the US space agency deployed OSIRIS-REx on a mission to explore Bennu, a primordial piece of space debris that can trace its origins back to the formation of the solar system. Now, OSIRIS-REx is poised to land on Bennu’s surface, making for NASA’s first-ever asteroid sample return mission, and the biggest delivery of extraterrestrial material since the Apollo era of the 1960s and ‘70s.
It’s a technological feat nearly two decades in the making, and its main goal is to collect a pristine, unaltered sample from the asteroid’s surface. To do so, the spacecraft will utilise a special robotic arm with a collection head on the end. On Tuesday afternoon, the plucky little craft is expected to descend to Bennu’s surface, extend its arm and blast the asteroid with enough nitrogen gas to push surface material up into the collection head.
Studying Bennu is going to help us better understand the role asteroids might play in delivering these life-forming compounds to Earth.
It will take OSIRIS-REx four hours to traverse the 0.6 miles (one kilometre) distance down to the surface, moving approximately 3.9 inches per second (10 centimetres per second). Once it gets close to the surface, the craft will extend its more than nine-foot-long (three-metre-long) robotic arm, called TAGSAM (or Touch-and-go Sample Acquisition Mechanism), which is topped with a sample collection device resembling a large shower head. It’s designed to blow a small burst of nitrogen gas onto Bennu’s surface to stir up some dust and rocks.
This material will then be collected in a ring around the head, which can store just about four pounds (1.8kg) of material. OSIRIS-REx’s goal is to collect at least 0.13 pounds (60g) of surface material from Bennu, which may not sound like a lot, but is an incredibly tricky manoeuvre to pull off that requires extreme precision – especially on a rocky, uneven surface like Bennu’s, where boulders can be the size of football pitches.
OSIRIS-REx arrived at Bennu in 2018 and meticulously mapped the asteroid’s surface across a two-year period to determine the best place to collect the sample. The result? A 66-foot-wide (20-metre-wide) crater near Bennu’s north pole that the team calls Nightingale. It was selected primarily because the crater appears to be young, which means that the exposed rock is likely to consist of pristine samples from when the asteroid was formed billions of years ago.
OSIRIS-REx’s collection head was designed to work best on a flat, sandy surface, which Bennu does not have. So scientists will have to aim carefully, as it could spell trouble for the mission if the arm touches down on top of rocks that are more than a few centimetres in diameter — severely limiting how much material that could be collected. Also, TAGSAM only has three nitrogen bottles, so the team can’t afford to waste them.
The team basically has a single shot to collect as much material as they can from Nightingale crater. That’s because once the nitrogen gas is fired, the surface material is disrupted, flying – hopefully – up into the collection head. It’s an opportunity literally years in the making.
Mapping the asteroid
OSIRIS-REx has two key tools that will help the spacecraft determine if it’s safe to land and start the collection process on Tuesday.
“There are two key products we’ve built, one of which is a detailed map of the asteroid’s surface, complete with potential hazards for the spacecraft,” Dante Lauretta, the mission’s principal investigator from the University of Arizona, told Al Jazeera. “And the other is a catalogue of features in the crater.”
If a sample is collected, it will be weighed and the team will determine if another attempt is necessary. But if all goes as planned and there is enough material in the OSIRIS-REx’s collection head, it will be stowed in a special canister that will be jettisoned when the spacecraft swings by Earth in 2023.
If this kind of chemistry is happening in the early solar system, it probably happened in other solar systems as well. It helps us assess the likelihood of the origin of life occurring throughout the galaxy and, ultimately, throughout the universe.
But if OSIRIS-REx’s onboard hazard map determines it isn’t safe to land in Nightingale, the spacecraft will abort the manoeuvre and the team will have to reassess its plans – and its maps. Both the onboard hazard map and the catalogue of features in the crater “change as a result of us firing the TAGSAM at the surface, so we will need to rebuild our maps,” Lauretta explained.
If the team fails to collect at least 0.13 pounds of material from Bennu on Tuesday, there is a second chance as early as December, but it might require relocating to a different crater. That manoeuvre would be a repeat of Tuesday’s plans, at another site near Bennu’s equator, called Osprey, which is equally enticing. Each dive is incredibly risky, so the team is hoping it will collect enough samples on the first try.
Asteroid researchers have been waiting for years to get their hands on dirt from Bennu. These types of space rocks are incredibly interesting to scientists because asteroids contain pieces of the earliest materials that formed our solar system, and studying them might allow scientists to answer fundamental questions about the origins of the solar system. That’s because moons and planets have changed over time, but most asteroids have not.
“Asteroids are like time capsules floating in space that can provide a fossil record of the birth of our solar system,” Lori Glaze, NASA’s director of Planetary Science, told Al Jazeera. “They can provide valuable information about how planets, like our own, came to be.”
Bennu was selected as a target because scientists believe it is a small fragment of what was once a much larger space rock that broke off during a collision between two asteroids early on in our solar system’s history.
The rubble pile seen today is more than 4.5 billion years old, a perfectly preserved cosmic time capsule that could contain clues about the origin of life, Lauretta said.
“Bennu turned out to be exactly the kind of target we hoped it would be,” Lauretta said.
Thanks to data collected from orbit, the team has determined two key discoveries: first, that between 5 and 10 percent of Bennu’s mass is water, and second, that its surface is littered with carbon-rich molecules. This means that any samples returned to Earth could help scientists better understand what role asteroids played in bringing water to our planet, and seeding it with the prebiotic material that provided the building blocks for life.
Asteroids are like time capsules floating in space that can provide a fossil record of the birth of our solar system. They can provide valuable information about how planets, like our own, came to be.
Earlier this month, researchers on the OSIRIS-REx team made an exciting discovery, one that confirmed something the team suspected all along: Bennu is rich in organic material. The results were published in a series of papers in the journal, Science.
“Organic molecules make up all living things on Earth,” Jamie Elsila, a research scientist at NASA Goddard Space Flight Center, told Al Jazeera. “Studying Bennu is going to help us better understand the role asteroids might play in delivering these life-forming compounds to Earth.”
Studying that material could also help scientists discover whether life exists elsewhere in the solar system, as well.
“If this kind of chemistry is happening in the early solar system, it probably happened in other solar systems as well,” Lauretta said. “It helps us assess the likelihood of the origin of life occurring throughout the galaxy and, ultimately, throughout the universe.”
Once the asteroid samples are back on Earth, they will be catalogued by scientists at NASA’s Johnson Space Center. The agency will keep the majority of the material, studying some of it immediately and sending some samples to research groups around the world. NASA also plans to store a portion in a secure location in New Mexico for safekeeping.
“The Bennu sample is going to provide important science information now, but also for generations to come,” Elsila said.
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