Connect with us

Science

Cosmic Cataclysm Allows Precise Test of Einstein’s Theory of General Relativity – SciTechDaily

Published

on


The MAGIC telescope system at the Roque de los Muchachos Observatory, La Palma, Canary Islands, Spain. Credit: Giovanni Ceribella/MAGIC Collaboration

In 2019, the MAGIC telescopes detected the first Gamma Ray Burst at very high energies. This was the most intense gamma-radiation ever obtained from such a cosmic object. But the GRB data have more to offer: with further analyses, the MAGIC scientists could now confirm that the speed of light is constant in vacuum — and not dependent on energy. So, like many other tests, GRB data also corroborate Einstein’s theory of General Relativity. The study has now been published in Physical Review Letters.

Einstein’s general relativity (GR) is a beautiful theory that explains how mass and energy interact with space-time, creating a phenomenon commonly known as gravity. GR has been tested and retested in various physical situations and over many different scales, and, postulating that the speed of light is constant, it always turned out to outstandingly predict the experimental results. Nevertheless, physicists suspect that GR is not the most fundamental theory, and that there might exist an underlying quantum mechanical description of gravity, referred to as quantum gravity (QG).

Some QG theories consider that the speed of light might be energy dependent. This hypothetical phenomenon is called Lorentz invariance violation (LIV). Its effects are thought to be too tiny to be measured, unless they are accumulated over a very long time. So how to achieve that? One solution is using signals from astronomical sources of gamma rays. Gamma-ray bursts (GRBs) are powerful and far away cosmic explosions, which emit highly variable, extremely energetic signals. They are thus excellent laboratories for experimental tests of QG. The higher energy photons are expected to be more influenced by the QG effects, and there should be plenty of those; these travel billions of years before reaching Earth, which enhances the effect.

Gamma-Ray Burst Hits MAGIC

Artist’s impression of a gamma ray burst observed by the MAGIC telescope system and satellite observatories.
Credit: Superbossa.com and Alice Donini

GRBs are detected on a daily basis with satellite-borne detectors, which observe large portions of the sky, but at lower energies than the ground-based telescopes like MAGIC. On January 14, 2019, the MAGIC telescope system detected the first GRB in the domain of teraelectronvolt energies (TeV, 1000 billion times more energetic than the visible light), hence recording by far the most energetic photons ever observed from such an object. Multiple analyses were performed to study the nature of this object and the very high energy radiation.

Tomislav Terzić, a researcher from the University of Rijeka, says: “No LIV study was ever performed on GRB data in the TeV energy range, simply because there was no such data up to now. For over twenty years we were anticipating that such observation could increase the sensitivity to the LIV effects, but we couldn’t tell by how much until seeing the final results of our analysis. It was a very exciting period.”

Naturally, the MAGIC scientists wanted to use this unique observation to hunt for effects of QG. At the very beginning, they however faced an obstacle: the signal that was recorded with the MAGIC telescopes decayed monotonically with time. While this was an interesting finding for astrophysicists studying GRBs, it was not favorable for LIV testing. Daniel Kerszberg, a researcher at IFAE in Barcelona said: “when comparing the arrival times of two gamma-rays of different energies, one assumes they were emitted instantaneously from the source. However, our knowledge of processes in astronomical objects is still not precise enough to pinpoint the emission time of any given photon.”

Traditionally the astrophysicists rely on recognizable variations of the signal for constraining the emission time of photons. A monotonically changing signal lacks those features. So, the researchers used a theoretical model, which describes the expected gamma-ray emission before the MAGIC telescopes started observing. The model includes a fast rise of the flux, the peak emission and a monotonic decay like that observed by MAGIC. This provided the scientists with a handle to actually hunt for LIV.

A careful analysis then revealed no energy-dependent time delay in arrival times of gamma rays. Einstein still seems to hold the line. “This however does not mean that the MAGIC team was left empty-handed,” said Giacomo D’Amico, a researcher at Max Planck Institute for Physics in Munich; “we were able to set strong constraints on the QG energy scale.” The limits set in this study are comparable to the best available limits obtained using GRB observations with satellite detectors or using ground-based observations of active galactic nuclei.

Cedric Perennes, postdoctoral researcher at the university of Padova added: “We were all very happy and feel privileged to be in the position to perform the first study on Lorentz invariance violation ever on GRB data in TeV energy range, and to crack the door open for future studies!”

In contrast to previous works, this was the first such test ever performed on a GRB signal at TeV energies. With this seminal study, the MAGIC team thus set a foothold for future research and even more stringent tests of Einstein’s theory in the 21st century. Oscar Blanch, spokesperson of the MAGIC collaboration, concluded: “This time, we observed a relatively nearby GRB. We hope to soon catch brighter and more distant events, which would enable even more sensitive tests.”

Reference: “Bounds on Lorentz Invariance Violation from MAGIC Observation of GRB 190114C” by V. A. Acciari et al. (MAGIC Collaboration), 9 July 2020, Physical Review Letters.
DOI: 10.1103/PhysRevLett.125.021301

Let’s block ads! (Why?)



Source link

Continue Reading

Science

SpaceX launches 57 more Starlink satellites, lands rocket at sea – Space.com

Published

on


CAPE CANAVERAL, Fla. — SpaceX successfully launched dozens of Starlink internet satellites and two small Earth-imaging satellites into orbit Friday (Aug. 7) in the second of what’s expected to be a series of Starlink rideshare missions.

A two-stage Falcon 9 rocket carrying 57 SpaceX Starlink satellites, along with two BlackSky Global Earth-observation satellites, lifted off at 1:12 a.m. EDT (0512 GMT) from Pad 39A here at NASA’s Kennedy Space Center.

It was the fifth launch for this Falcon 9’s first stage. And the booster pulled off yet another landing this morning, settling softly onto the deck of SpaceX’s “Of Course I Still Love You” droneship in the Atlantic Ocean about eight minutes after liftoff.

Related: SpaceX’s Starlink satellite megaconstellation launches in photos

This is SpaceX’s 10th Starlink mission since 2019, and the company’s 12th overall mission for 2020. SpaceX has been relying on its fleet of used, flight-proven boosters to sustain a rapid launch cadence. The company has had a stellar summer, with the launch and landing of two NASA astronauts on the Demo-2 mission to the International Space Station — a first for a private company — and isn’t slowing down anytime soon. 

The third time was the charm for SpaceX as its Falcon 9 rocket roared to life and lit up the night sky over Florida’s Space Coast. Nighttime launches are always a stunning spectacle, and this one did not disappoint. The rumble from the rocket’s nine engines seemed especially loud tonight and could still be heard even after the rocket disappeared from view. 

Hitchhiking satellites

Tucked inside the Falcon 9’s nose cone this morning was a stack of 57 internet-beaming satellites. Part of SpaceX’s Starlink megaconstellation, the satellites will join hundreds already in orbit. To date, the company has launched 595 Starlink satellites as it works to complete the huge constellation. 

SpaceX founder and CEO Elon Musk has said that SpaceX needs between 400 and 800 Starlink satellites in orbit to begin to roll out minimal coverage. As that goal draws nearer, SpaceX has been teasing the arrival of a beta program, which will help the company test the service for eventual worldwide consumption. 

SpaceX is also taking other steps to make Starlink service a reality. For example, the company has gained approval from the U.S. Federal Communications Commission for up to one million user terminals

Musk has said that he wants the terminals to be easy to operate. Resembling a “UFO on a stick,” as Musk calls it, each terminal is equipped with actuators to ensure that it points at the sky at all times. All a user has to do is plug it in and point it at the sky. 

Hitching a ride with the Starlink stack today were two small, Earth-observing satellites for BlackSky. The rideshare was arranged by another company called Spaceflight, which finds rides to space for smaller satellites. SpaceX also has its own rideshare program, which books small satellites directly instead of going through a third-party service. (Three small Earth-observing satellites built by San Francisco-based company Planet flew on the previous Starlink mission last month, in a deal booked directly through SpaceX.)

Related: What’s that in the sky? It’s a SpaceX rocket, but it sure doesn’t look like it

Satellite sunshades

The Starlink satellites on this mission are a bit different than the ones that have launched previously. That’s because they’re outfitted with a special visor that will help reduce their apparent brightness. 

The sunshade, as SpaceX is calling it, is a deployable visor designed to prevent sunlight from reflecting off the shiniest parts of the satellites, such as the antennas. The company — as well as astronomers and dark-sky advocates around the world — are hoping to decrease the Starlink fleet’s overall brightness. This will enable them to appear as dark as possible in the night sky, thus minimizing their impact on night sky observations. 

When the very first set of Starlink satellites launched, it caught the astronomy community off guard as the satellites appeared brighter in the sky than SpaceX intended. Scientists around the globe voiced their disapproval, concerned that the bright satellites would inhibit scientific observations. 

A previous Starlink launch back in June featured one satellite outfitted with the experimental visor; today’s mission is the first in which all 57 sport it. 

Rocket reuse

The first stage of the Falcon 9 featured in today’s mission is now a five-time flier, as it previously launched the Demo-1 mission in 2019, which sent an uncrewed Crew Dragon spacecraft to the International Space Station; a trio of Earth-observing satellites for Canada; and two Starlink missions this year. 

It is the third Falcon 9 booster to launch five times, and the second to launch and land successfully five times. The first booster to launch five times, designated B1048 by SpaceX, experienced an inflight anomaly. There was some residual cleaner trapped inside an engine part, which resulted in the booster missing its intended landing on the drone ship. (The booster did deliver the payload to orbit with no issues, however.) 

SpaceX subsequently changed its refurbishment techniques and has now launched and recovered two different boosters five times. Each of these should fly again soon, especially if SpaceX is going to keep up its rapid launch cadence. 

Related: See the evolution of SpaceX’s rockets in pictures

The Falcon 9’s first stage successfully landed on SpaceX’s drone ship “Of Course I Still Love You” approximately eight minutes after liftoff. To do so, the booster separated from its upper stage and conducted a series of orbital ballet moves, reorienting itself for landing. The rocket conducted a series of three engine burns to slow itself enough to gently touch down on the deck of a floating platform. 

The massive drone ship, stationed out in the Atlantic Ocean, is one of two vessels that SpaceX uses to catch its returning boosters. To date, the company has successfully recovered 56 first-stage boosters. Once they’re back in Florida’s Port Canaveral, the boosters are transported back to SpaceX facilities, where they’re carefully inspected and repurposed to fly again. 

The current iteration of the Falcon 9 was finalized in 2018. Known as the Block 5, it features 1.7 million pounds of thrust as well as some other upgrades that make it capable of rapid reuse. SpaceX boasts that each of these boosters can fly as many as 10 times with minor refurbishments in between, and as many as 100 times before retirement. (To date, SpaceX has launched and landed the same booster a maximum of five times.) 

Rapid reuse, coupled with the fact the company now has two drone ships to recover its first-stage boosters, means that the company can launch more frequently. SpaceX launched a total of four times between the end of May and the end of June, and it plans to conduct a number of launches through the end of 2020.

Related: SpaceX launches 60 Starlink satellites and lands rocket in dazzling nighttime liftoff 

Falling fairings

Ahead of today’s launch, SpaceX deployed its twin fairing catchers, GO Ms. Tree and GO Miss Chief. These two boats act as giant, mobile catcher’s mitts, snagging payload fairings in their attached nets as they fall back down to Earth. Whether or not they’re able to make a catch depends on many factors, including the weather. 

To facilitate reuse, SpaceX has equipped its payload fairings (also known as the rocket nose cones) with parachutes and software that guides them to the recovery zone. If Ms. Tree or Ms. Chief are unable to catch the fairings, which come back to Earth in two pieces, the boats can scoop them up out of the water and carry them back to port. 

Once back in Port Canaveral, the fairings (along with the booster) are refurbished and reused, so long as they’re intact. SpaceX has reflown fairings several times, most of which were retrieved from the ocean and refurbished. However, on a recent mission, the dynamic boat duo made its first double catch, snagging both falling fairings.

SpaceX attempted to catch the fairings today but did not succeed, company launch commentators said about 48 minutes after liftoff.

Today’s launch was the third attempt at getting this particular mission off the ground. The launch was originally scheduled to blast off in mid-June, but was delayed due to the need for extra rocket checks. Another attempt on July 8 was called off due to poor weather at the launch site. 

Follow Amy Thompson on Twitter @astrogingersnap. Follow us on Twitter @Spacedotcom or Facebook.

Let’s block ads! (Why?)



Source link

Continue Reading

Science

ATLANTIC SKIES: Young astronomers and the Perseid meteors – SaltWire Network

Published

on


If you are intrigued by the concept of space travel and exploration, no doubt you watched or read about the launch of NASA’s Mars 2020 Perseverance spacecraft on July 30. NASA’s 29th mission to Mars (22 of which have been successful), Perseverance is slated to arrive at the Red Planet in February 2021, after a 7-month, 480-million-kilometre journey, to continue NASA’s ongoing exploration of Mars in preparation for its ultimate goal: landing humans on the planet’s surface in the next decade or two.

I remember, as a very young child (I was 5 at the time), my mother telling me that one day, when I was grown up, people would walk on the Moon. Sure enough, in 1969, when I was 21, Neil Armstrong and Buzz Aldrin stepped onto the Moon’s surface from the Apollo 11 spacecraft. Perhaps my mother was prophetic to foresee this event, or perhaps, as I suspect, she was just intuitive enough to understand that humankind’s destiny ultimately lies out there, beyond Earth, among the stars. 

Perhaps there is some component of the human genome that, like that which causes some animals to migrate, is responsible for humankind’s celestial wanderlust. Having explored and settled most every corner of our planet, perhaps this innate instinct to move onward is now driving us to consider migrating outwards from Earth to distant worlds. 


Perhaps there is some component of the human genome that, like that which causes some animals to migrate, is responsible for humankind’s celestial wanderlust.


Whatever the genesis of my mother’s statement, it ignited in me a burning desire and an insatiable curiosity to know more about what was “out there”. It is a desire and curiosity that has lasted my whole life, and will, no doubt, remain with me until I draw my final breath. Without waxing too poetic, I like to think that, even then, some part of me will continue, as Star Trek’s Captain James T. Kirk states, “to explore strange new worlds” across the eternity of outer space.

My granddaughter, Scarlet, has a fascination with outer space, constantly asking me what lies beyond the planets, our solar system, and the Milky Way Galaxy. Of course, it is a curiosity that I readily and happily feed, answering her questions (in greater detail and depth as she grows older), encouraging her to read my astronomy books (and columns), to pick out her own astronomy books (“space books” as she calls them) at the library, or to go on-line and look up the information herself. 

It is both amazing and gratifying to not only watch her search for the answers by herself, but also to watch where those searches take her in terms of the array of astronomy topics she delves into. As her knowledge base expands, so does the distance she travels outward from Earth; she is currently focused on the Oort Cloud, the massive sphere of frozen ice bodies out beyond Pluto. 

Her plan (at 8 years old) is to be the first woman astronaut to walk on Mars, or, should another woman beat her to that prize, to be the first woman to pilot a spaceship to another planet in a distant star system. “Attention, this is Captain Scarlet speaking.”

If you have children and/or grandchildren who show an interest in astronomy, I urge you to encourage that interest. Just as my mother’s insightful statement fostered my abiding love of and curiosity about outer space, your encouragement and support (and, perhaps, shared interest) may well result in your child, grandchild or great-grandchild one day walking on another planet or moon, or travelling out into space as a crew member on a fact-finding exploration. Perhaps, he or she may even be part of my granddaughter’s crew.

One of the ways to foster an interest in outer space in your children/grandchildren is to get them outside to watch a meteor shower. Children of any age love to watch for “shooting stars”, and the warm summer evenings of August are just the time to afford them that opportunity. The annual Perseid meteor shower (radiant in Perseus – the Prince) peaks during the pre-dawn hours of Aug. 11 – 13. 

Though light from the Last Quarter Moon will, after it has risen, somewhat reduce the overall number of meteors observable on those dates, the Perseids are known for their large number of extremely bright meteors, many of which, in the absence of cloud cover, will still be highly visible. 

Earlier in the evening, you may see some Perseid “earthgrazers” – colourful meteors that travel slowly and horizontally across the pre-midnight sky, when the meteor shower’s radiant (apparent point of origin in the sky) is just below or just above the eastern horizon. While the main peak of most meteor showers usually occurs after midnight, starting to watch for the Perseids during the mid-to-late evening period (perhaps more conducive to maintaining the interest of your young, sleepy-eyed observers), before the Moon rises, could significantly increase the total number of meteors seen. 

Go to this moonrise and moonset calculator to find your local moonrise/set times. Also, watching for Perseids on the nights/mornings after the noted peak dates might produce a large number of viewed meteors. As the week progresses, there will be less moonlight to contend with, as the Moon phase changes from Last Quarter towards a gibbous phase. Finally, the well-known variableness of meteor showers, even a famous one such as the Perseids, sometimes brings surprisingly large numbers of meteors in the days following designated peak dates; it is always worth a try, particularly if you are clouded out during the predicted peak period.

Heading towards superior conjunction with the Sun on Aug. 17, Mercury is now too close to the Sun to be observed. Venus (mag. -4.32) is that wonderfully brilliant “morning star” visible in the eastern, pre-dawn sky. Rising in the east around 2:30 a.m., Venus will be observable 31 degrees above the eastern horizon until dawn breaks around 5:45 a.m. 

Mars (mag. -1.3) is visible about 7 degrees above the eastern horizon around 11:45 p.m., reaching a height of 48 degrees above the southern horizon before fading in the dawn twilight. Jupiter and Saturn are both visible in the southeast evening sky by about 9 p.m. Jupiter (mag. -2.68) reaches its highest point (21 degrees) in the southern sky shortly after 11 p.m., remaining observable until about 2:30 a.m. when it sinks below 7 degrees above the southwest horizon. Saturn (mag. +0.2) hits its highest point in the southern sky shortly before midnight, disappearing from view around 3 a.m. when it dips below 10 degrees above the southwest horizon.

Until next week, clear skies.

Events:

  • Aug. 11 – Last Quarter Moon
  • Aug. 11-13 – Perseid meteor shower peak
  • Aug. 13 – Venus at greatest western elongation from Sun

RELATED:

Let’s block ads! (Why?)



Source link

Continue Reading

Science

SpaceX Bringing 2 Astronauts Home on Sunday!! But a Tropical Storm May Become the Hurdle!! – Gizmo Posts 24

Published

on


NASA space travelers Bob Behnken and Doug Hurley, who made spaceflight history on May 30 by turning into the primary individuals to dispatch to circle abroad a SpaceX automobile, their plan of returning home may get affected due to tropical storm.

Thus, after landing SpaceX’s Crew Dragon “Endeavour ” boat to the International Space Station and going through two months there, the men are getting ready to undock on Saturday. They’re expected back on Earth on Sunday at 2:48 p.m. ET.

NASA

Do the Astronauts have to stay there for more time?

NASA is supervising SpaceX’s trial strategic, Demo-2. On Wednesday, the office gave the organization a “go” to continue with its arrival plans. In any case, Tropical Storm Isaias could drive the space explorers to remain in a circle some time longer. The wind previously hit Puerto Rico with high breezes and glimmer floods. Its present way would carry awful climate to a few potential landing destinations by Sunday evening — the arranged time for the space travelers’ splashdown.

Crew Dragon can’t come down if there are rain, lightning, or winds overrunning 10 mph

Nevertheless, the managers of the mission probably may cancel the landing attempt depending on the climate. Thus, the heavy rain, winds lightning, and low clouds will moreover become a hurdle in the path of astronauts returning home. On Wednesday, the executive of NASA’s Commercial Crew Program, Steve Stich said, “We’re going to examine the conditions very carefully”.

However, Stich explained that, when the space travelers undock, they need to land inside around three days because the spaceship just has enough water and lithium hydroxide – which scours carbon dioxide from the air – to last Bob and Doug for that long.

Stich noted SpaceX and NASA can make a call as late as an hour prior undocking to defer the entire succession and attempt again one more day.

Let’s block ads! (Why?)



Source link

Continue Reading

Trending