The SpaceX Starlink mega-constellation now has 422 satellites orbiting Earth after yesterday’s successful launch of another batch of 60.
It was the seventh batch of Starlinks sent to into orbit, and astronomers and astrophotographers are annoyed.
Starlink satellites are brighter than anyone expected, leading to a swarm of bright lights crossing the night sky that look like a “string of pearls.”
Such a sight was visible this week in Europe, and the new batch are sure to be similarly visible in the coming months.
Although many stargazers have enjoyed seeing them streak across the night sky in “trains,” it’s not ideal; Starlink satellites were never intended to be bright, and their brightness is bad news for science.
So what is SpaceX CEO Elon Musk doing about it?
“We’re fixing it now,” said Musk in a tweet after yesterday’s launch, as reported by the BBC.
What does that mean?
Musk said that the issue was the angle of the solar panels during the orbit/raise park. Let’s break that down. He’s referring to the fact that Starlink satellites light-up when the Sun hits their solar panels as viewed from specific locations on Earth in twilight. He’s also referencing the fact that after launch they take some time to reach their operational orbit. That’s why satellites launched in March have been visible as “trains” of over the night skies of Europe this week.
Hopefully, Starlink satellites in their “final” positions won’t flare anywhere near as much as the newly-launched satellites do, but it’s likely that the 60 launched yesterday will cause significant problems for some in the next few months.
With 12,000 satellites planned to be in for the final configuration of the Starlink constellation, that’s potentially a lot of launches and post-launch periods of bright Starlinks.
However, Musk’s comments suggest that SpaceX will change the angle of the satellites’ solar panels to lessen the problem.
Angles and sunshades
In another tweet he said that SpaceX would be changing the angles of the solar panels on Starlink satellites and that they would all be getting “sunshades” starting with launch number nine.
Yesterday’s launch was the seventh Starlink mission, with the eighth planned for May 2020. Dates of further launches are yet to be made public.
When will Starlink go live?
According to SpaceX, Starlink will deliver high speed broadband internet to locations where access has been unreliable, expensive, or completely unavailable. With 422 satellites already in orbit no commercial plans have been officially unveiled.
However, a tweet yesterday by Elon Musk suggested that a private beta of a Starlink broadband internet service would begin in less than three months, followed by a public beta in under six months, though only to locations in “high latitudes.”
Wishing you clear skies and wide eyes.
Bright, rare comet lighting up Canadian skies for next few days – CityNews Vancouver
WINNIPEG (CITYNEWS) – Stargazers across Canada and the world have been catching rare glimpses of the brightest comet of the last two decades – and there’s still time to do so.
Comet Neowise, named after the satellite that first discovered it, is headed toward Earth and will continue to light up the night sky for the next few days. The best times to see it are just after sunset and around 3 a.m.
Scott Young, manager of the Planetarium at the Manitoba Museum says the comet, which is composed of rock and ice, dates back to the origin of the solar system.
“Most of the time, these are not something you can see without a telescope,” said Young. “But once in a while, one of these comets surprises us and gets brighter than expected, and that is what we are seeing here. It is visible to the unaided eye and from a location away from city lights.
“It’s really cool to see a comet like this. This is probably, almost certainly, the first time that any humans have seen this particular object.”
Young says the comet will get as close as 100 million kilometres from Earth, which is normally too far to be seen with the naked eye.
“For whatever reason, this comet has melted a lot and the tail has grown very big and bright, and that’s what we’re able to see from this distance,” he said.
Another shot from Friday morning! Stacked to bring out more of the brilliance of all the stars and nocilucent clouds! THIS one, I would be proud to hang on my wall! I can’t wait to shoot #NEOWISE again!❤️#comet #cometNEOWISE #StormHour #noctilucentclouds #NOCs #Manitoba #Canada pic.twitter.com/Y2AUbPAL0e
— Shannon Bileski☈ (@shannbil) July 11, 2020
Photographer Shannon Bileski has captured several snapshots of the comet in the last few days. She says her photos were made even better by the presence of very vibrant clouds in the upper atmosphere.
“They’re very incredible to see and I knew the spot that I wanted to hit, try to hit the comet and that’s where I went,” said Bileski, whose bucket list included photographing a comet. “Get out, see it, shoot it. It’s pretty amazing to see.”
The last time a comet of this calibre was visible from Earth was Comet Hale-Bopp in 1997, according to Young. He says Comet Neowise is not expected to re-enter our solar system for another 6,000 years.
“They could happen at any time,” said Young. “They’re very unpredictable. We don’t know where they all are, and sometimes a new discovery like this one will come out of nowhere and just surprise us.
“Astronomers have basically dropped everything they are doing to take advantage of this limited opportunity.”
Cosmic Cataclysm Allows Precise Test of Einstein’s Theory of General Relativity – SciTechDaily
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.
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.
Weather: Richmond expects a mix of sun and clouds this week – Richmond News
Richmond will see sunshine and higher temperatures early this week with some showers and cloud leading into the weekend.
According to Environment Canada, Sunday will see a mixture of sun and clouds with a 40 per cent chance of showers in the early afternoon. Skies are expected to clear up later in the day with temperatures as high as 20 C. Few clouds will roll in in the evening with a low of 11 C.
Monday through Wednesday will expect sunshine all day with a high of 22 C and a low of 12 C.
There is a 60 per cent chance of showers from Wednesday evening until Thursday evening.
Clouds will make reappear again on Friday and Saturday with a high of 21 C and a low of 15 C.
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