Chinese Space Station Tiangong-1 Expected to Crash in the Next 24 Hours

It’s almost crash time for China’s falling space station Tiangong-1. As school bus-sized space station began what should be its last day in orbit today (April 1), experts weighed in on the possibilities of space debris – and whether this situation should have happened in the first place.

Tiangong-1 is expected to re-enter Earth’s atmosphere sometime between Sunday evening and early Monday, according to the European Space Agency. The latest forecast from the non-profit Aerospace Corp. pegged the space station crash at 8:10 p.m. EDT tonight (0010 GMT Monday, April 2), give or take 2.5 hours. But the time of the re-entry – along with the geographic area – is still highly volatile as Tiangong-1 continues its descent. [Track Tiangong-1! Use This Satellite Tracker]

We know that Tiangong-1 is tumbling, or at least it was when Germany took [a] radar update, so the question is it still tumbling, and is the tumbling getting faster or slower,” Andrew Abraham, a senior member of Aerospace’s technical staff, told Space.com in an interview at 7 p.m. EDT Saturday (March 31) when the group released its latest forecast. He noted that the time of re-entry keeps getting pushed into the future, so the window of uncertainty remains large. As the re-entry time approaches, the range of re-entry times will narrow.

An artist's illustration of China's Tiangong-1 space station falling to Earth as it burns up in the atmosphere. The spacecraft is expected to crash uncontrolled sometime overnight on April 1 or 2, 2018.

An artist’s illustration of China’s Tiangong-1 space station falling to Earth as it burns up in the atmosphere. The spacecraft is expected to crash uncontrolled sometime overnight on April 1 or 2, 2018.

Credit: China Manned Space Engineering Office

As of today, Tiangong-1 is flying in an orbit of 104 miles (167.6 kilometers) and falling, the China Manned Space Engineering Office said in a statement cited by Xinhua News Service. CMSEO officials have said Tiangong-1 will mostly burn up in the Earth’s atmosphere, and is unlikely to cause any damage on the ground, CMSEO officials added.

Although Abraham said this is speculation on the part of Aerospace, he said it is possible Tiangong-1 is now encountering more of Earth’s atmosphere as it falls towards the surface of the planet. If that’s the case, the atmosphere might be influencing the attitude or orientation of Tiangong-1’s tumble. He compared the situation to an arrow moving through the air, or a wind vane undulating in the wind. “They align themselves to the direction of travel,” he said. “There’s a bit higher drag in the back, and the center of mass is towards the front.”

Aerospace uses publicly available data from the United States Air Force in making its Tiangong-1 predictions. The military has a network of radar and optical telescopes, and publishes data at spacetrack.org. Abraham said after Tiangong-1 enters Earth’s atmosphere, there may be a delay of a few hours to confirm it. That’s because Aerospace will wait for information from multiple sensors, in the case that Tiangong-1-‘s descent isn’t observed.

China's Tiangong-1 space station is predicted to fall somewhere between the latitudes of 42.8 degrees north and 42.8 degrees south, the area shaded in yellow and green here.

China’s Tiangong-1 space station is predicted to fall somewhere between the latitudes of 42.8 degrees north and 42.8 degrees south, the area shaded in yellow and green here.

Credit: Aerospace Corporation

The docking of two robotic spacecraft, the Tiangong 1 space station and Shenzhou 8 capsule, provided a preview of larger Chinese space complexes planned for the future.

The docking of two robotic spacecraft, the Tiangong 1 space station and Shenzhou 8 capsule, provided a preview of larger Chinese space complexes planned for the future.

Credit: Karl Tate, SPACE.com Contributor

Chinese space officials lost contact with the 9.4-ton (8.5-metric ton) station in 2016 after five successful years of operations, including two visits by Chinese crews of astronauts. China did not make it clear if they cut off contact with the station deliberately, or if they lost telemetry with Tiangong-1 due to a technical issue. Whatever the cause, the result was the same: Tiangong-1 began an inevitable descent into Earth’s atmosphere.[China’s Falling Space Station: Everything You Need to Know]

“This should not have happened,” David Barnhart, a satellite designer who is the director of the University of Southern California’s space technology and systems group, told Space.com Saturday (March 30). “To date, almost everything we put into space, at some point, is going to die. But something that large, we now have the technology to go up to it and prolong its life.”

He said the demise of Tiangong-1 raises questions about the end of the International Space Station, which is projected to host crews until at least 2024, if not longer. It’s unclear what will happen to the ISS after that. While the nominal plan is to deorbit it, at least one commercial company is considering using modules of the ISS for its own research. Barnhart urged engineers to plan how to re-use ISS as soon as possible, to avoid throwing it away into the Earth’s atmosphere.

Tiangong-1’s orbital inclination carried it over most of Earth’s populated areas, between 43 degrees north and 43 degrees south latitudes. The zone includes the United States, Central America, South America, Australia and much of Europe and Asia.

With so many people below Tiangong-1’s path, its descent caused worldwide speculation about the dangers of space debris from the 9.4-ton (8.5-metric ton) module. Several entities closely monitored its fall and issued updates, including the China Manned Space Engineering (CMSE) Office, the European Space Agency’s Space Debris Office in Germany, and Aerospace Corp.

 Late in Tiangong-1’s life, it was unclear how much debris would make it down to the surface.

“Our company has the ability to do that [predict space debris] if we have a firm idea of the exact composition of the space object … especially ones in which we’re involved with the design,” Abraham told Space.com in another interview earlier Saturday (March 31). [The Biggest Spacecraft to Fall Uncontrolled From Space]

“But because China doesn’t really send that information, the best we can tell you is between 10 percent and 40 percent of the mass of Tiangong-1 would survive,” he added. Assuming the space station is 9.4 tons, this would imply roughly 1,880 to 7,520 pounds (850 to 3,411 kg) would reach the surface, he confirmed, but this is a broad generalization given that Aerospace does not have Tiangong-1’s exact composition.

While Space Safety Magazine gave similar space debris predictions, other people said not nearly as much material would make it through the atmosphere. In an interview with Space.com sister site Live Science, Harvard University astrophysicist Jonathan McDowell predicted only 220 lbs. to 440 lbs. (100 to 200 kg) would survive the descent.

China's first space station Tiangong-1, shown here in an artist's illustration, is expected to fall to Earth around April 1, 2018.

China’s first space station Tiangong-1, shown here in an artist’s illustration, is expected to fall to Earth around April 1, 2018.

Credit: China Manned Space Engineering Office

USC’s Barnhart said perhaps a couple of hundred pounds would make it to the surface, but that depends on many factors – the angle of Tiangong-1’s re-entry, the melting point of any metals on board, and how shielded the inside of the space station will be from re-entry. He added that trying to predict Tiangong-1’s generated space debris is no worse than other uncontrolled re-entries he saw. “It’s pretty complicated stuff, but this is normal,” Barnhart said.

China’s CSME, for its part, told the public that little of Tiangong-1 would survive, and added it would most likely splash down somewhere in the ocean since water covers 70 percent of the Earth’s surface.

“It won’t crash to the Earth fiercely, as in sci-fi movie scenarios, but will look more like a shower of meteors,” read a March 29 update from CMSE, according to the Chinese state media outlet Xinhua.

The CMSE added that the disintegration of Tiangong-1 will take place in multiple phases, Xinhua added.

“During the first phase [of Tiangong-1’s re-entry], the atmospheric drag will rip solar arrays, antennas, and other external parts off a spacecraft at an altitude of about 100 kilometers [62 miles],” Xinhua said, noting the station would likely disintegrate at 80 km (49 miles) in altitude. “The fragments will keep burning and most of them will get dissipated in air. Only a small amount of debris will reach the ground, and will float down at a very slow speed due to their small mass.”

China began addressing safety concerns at least as far back as May 2017, when representatives from the Permanent Mission of the People’s Republic of China made a statement to the United Nationsoutlining their plan to disseminate information through the media and government channels. Back then, they predicted re-entry would happen any time between October 2017 and April 2018.

As Tiangong-1’s re-entry time drew close in March, the sun’s activity confounded predictions. Forecasts of the sun’s activity at first showed that a stream of particles would collide with Earth’s atmosphere, causing it to balloon. The increased atmospheric density at Tiangong-1’s low altitude would, predictions said, cause the station to fall faster into the atmosphere as its orbital speed slowed due to drag.

The sun remained quiescent, however, and Tiangong-1’s final entry time was delayed by several days due to lower atmospheric density than expected. The atmosphere not only affects the resistance Tiangong-1 encountered in its orbit, but how it was expected to fall apart, Barnhart said. “Most platforms in space are made from some level of aluminum or titanium,” he added. “Each has a different melting point, and they are also affected differently from the forces they will see in the atmosphere.”

 The chance of Tiangong-1 hitting any single spot on the surface is extremely low; a particular person would have a far better chance of winning the Powerball jackpot, according to Live Science. The odds of getting hit by space station debris were about in 292 trillion. The odds of winning the Powerball are about one in 292 million, according to Aerospace Corp.

Tiangong-1 is about the mass of ATV-1 “Jules Verne”, a European cargo freighter that came back from the International Space Station in 2008. ESA deliberately targeted Jules Verne for a nighttime descent over the Pacific Ocean; a chase plane filmed fireballs lighting up the darkness. ESA posted footage of the light show in 2015. Aerospace Corp. said Tiangong-1 could generate fireballs of a similar magnitude, if it fell at night.

Tiangong-1 is just one example of large space modules falling apart in Earth’s atmosphere. The descending Skylab space station famously dropped pieces into rural Australia, west of Perth, in 1979; however, Skylab was about 10 times more massive than Tiangong-1. Other prominent examples of uncontrolled re-entries include NASA’s Upper Atmosphere Research Satellite (2011) and Europe’s Gravity Field and Steady-State Ocean Circulation Explorer (2013).

Chinese space station operations remain active with a successor space station, called Tiangong-2. The newer station launched in September 2016, and astronauts aboard Shenzhou 11 visited Tiangong-2 in October and November 2016. China plans an even larger, multi-module space station that will be built in the 2020s.

Editor’s note: If you spot Tiangong-1 streaking across your sky during its re-entry and capture video or images of the descent, let us know! You can send images and video in to spacephotos@space.com. This story was updated at 10:36 a.m. EDT to include the latest re-entry forecast by ESA and Aerospace Corp.

Visit Space.com today for complete coverage of the Tiangong-1 re-entry.

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Source: Space

Annunci

Where Will Debris from China’s Falling Space Station Land? Here’s the Latest Update

 

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 While it’s still hard to predict exactly when and where the doomed Chinese space station Tiangong-1 will fall this weekend, the latest prediction from Aerospace Corp. says the debris will most likely descend into the Pacific Ocean Sunday (April 1).

As of late Friday, Tiangong-1 was predicted to fall from space on Sunday at 12:15 p.m. EDT (1615 GMT), give or take 9 hours. Earlier in the day, when the space station’s fall was forecast for 12 p.m. EDT on Sunday, an expert told Space.com that earlier prediction would have seen Tiangong-1 begin its re-entry over Malaysia, and rain debris downrange into the Pacific Ocean.because the space station is moving in its orbit across the equator, toward the north.

“It should be a show for anybody on a boat,” Aerospace Corp.’s Ted Muelhaupt told Space.com. He runs a center for orbit and re-entry debris studies at the California nonprofit research organization, which is tracking the descent of Tiangong-1. [Track Tiangong-1! Use Our Satellite Tracker Here by N2YO]

Real-time tracking information for Tiangong-1 is available here from Aerospace Corp.’s Center for Orbital and Debris Reentry Studies.

TheAerospaceCorp

@AerospaceCorp

Our current prediction of the reentry is April 1 at 16:15 UTC ± 9 hours. Further updates can be found here: http://www.aerospace.org/cords/reentry-predictions/tiangong-1-reentry/ 

Muelhaupt said people around Malaysia can expect to see fireballs similar in magnitude to the spectacular planned breakup of ATV-1 “Jules Verne,” a European cargo freighter that returned from the International Space Station in 2008. In 2015, ESA published a video from a chase plane showing the dramatic, fiery breakup of ATV-1 over the Pacific Ocean. ATV-1 was similar in mass to Tiangong-1, which is 9.4 tons (8.5 metric tons).

While the amount of space debris generated from Tiangong-1 is tough to predict, roughly 220 to 440 lbs. (100 to 200 kg) may survive the fall through the atmosphere, Harvard astrophysicist Jonathan McDowell told Space.com sister site Live Science. That’s less material than what was left behind after the 1979 breakup of the 100-ton (90.7 metric ton) Skylab, which unexpectedly threw debris into rural Australia during re-entry.

China's first space station Tiangong-1, shown here in an artist's illustration, is expected to fall to Earth around April 1, 2018.

China’s first space station Tiangong-1, shown here in an artist’s illustration, is expected to fall to Earth around April 1, 2018.

Credit: China Manned Space Engineering Office

Although the Pacific Ocean is the most likely location for Tiangong-1’s demise, Muelhaupt emphasized it’s hard to say where the station will re-enter Earth’s atmosphere. The station is constantly orbiting Earth at an inclination between 43 degrees north and 43 degrees south latitudes, which includes the United States and much of the civilized world.

“The probability along the ground track is still pretty flat for the entire length of the track,” he explained. This means that although Malaysia is where the probability of re-entry peaks, it’s only a low spike compared to all of the other predicted points of re-entry.

At this point, Aerospace Corp. is more comfortable saying where the station likely will not re-enter; the Amazon, for example, is a “pretty safe” location, Muelhaupt said. He compared the situation to trying to predict the odds of who will won a lottery.

“One of the things about probability — just because you bought two lottery tickets, doesn’t mean you have a much higher probability of winning than someone who bought one,” Muelhaupt said. He added that the chance of any particular location “winning” the Tiangong-1 re-entry lottery — of experiencing space debris from the falling space station — is extraordinarily low. But as geographical regions of possible space debris are eliminated, the other locations on Earth will have a slightly higher probability of debris.

As Tiangong-1 descends closer to Earth, predictions of its fall location will improve. No one will know for sure where the space station will fall, however, until it actually comes down. “By tomorrow afternoon, we’ll probably know within two to three orbits where it will come in,” Muelhaupt said. [Chinese Space Station’s Crash to Earth: Everything You Need to Know]

This map by the European Space Agency shows the area in which China's Tiangong-1 space station could fall (shown in green) around April 1, 2018.
This map by the European Space Agency shows the area in which China’s Tiangong-1 space station could fall (shown in green) around April 1, 2018.

Credit: European Space Agency

To create its Tiangong-1 re-entry prediction, Aerospace Corp. uses no less than eight prediction methods. It tries to find a consensus between the models for its published estimates.

“Each one [model] makes slightly different assumptions, with slightly different orbit propagators,” Muelhaupt said. “Depending on how the model is written, you have to make guesses about different things. Each of them comes with a slightly different perspective. There is no one way to model these things, so we run a basket and look at where we think the consensus is.”

For example, one of the models uses a Monte Carlo simulation — a computer simulation that shows a range of possible outcomes, and the probability of each outcome occurring. Another model emphasizes one particular outcome, or “truth,” over all others, Muelhaupt explained. Some models assume breakup occurs at a slightly higher altitude than others, which also affects Tiangong-1’s predicted fall.

An artist's illustration of China's Tiangong-1 space station as it breaks apart and burns up in Earth's atmosphere.

An artist’s illustration of China’s Tiangong-1 space station as it breaks apart and burns up in Earth’s atmosphere.

Credit: Aerospace Corporation

“We base all public statements on publicly released information, run through each of the different models, average the results and look for consensus,” Muelhaupt said, but said even that can produce challenges.

“Occasionally we get one model that is an outlier. For example, it might put more weight on a later prediction, vs. earlier measurements … that’s why we run multiple models. Every time you think you’ve got all of the guesses right, you are wrong. So it is best to get multiple opinions.”

One important factor in making predictions is the geomagnetic index — the amount of activity generated in Earth’s vicinity from the sun. The sun’s energy, as it strikes the Earth’s atmosphere, can make gases balloon higher and increase the density at more elevated altitudes. The sun’s activity in recent days, however, was quieter than expected.

The sun’s quiescence keeps delaying the time of Tiangong-1’s expected re-entry, because it means the Earth’s atmospheric density near the station is lower than expected. That’s made a huge difference in re-entry predictions. Just three days ago, Muelhaupt noted, Aerospace Corp. predicted a re-entry time of 0200 GMT April 1 (10 p.m. EDT March 31). That’s 16 hours earlier than the current expected re-entry time.

Tiangong-1 launched in 2011 and hosted two crews of taikonauts (Chinese astronauts) in 2012 and 2013. China subsequently lost contact with the space station in 2016, and Tiangong-1 has been falling to Earth ever since. Tiangong-1 is the first Chinese space station, and a successor — Tiangong 2 — began operations in 2016.

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Source: Space

Saturday’s Blue Moon Is the Last One Until 2020 (Don’t Miss It!)

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Skywatchers take note: The last Blue Moon of 2018 is just around the corner. If you miss it, you’ll have to wait to 2020 for the next one.

 The upcoming Blue Moon — the name given to the second full moon to occur in a single calendar month — rises on Saturday (March 31). It’ll be the second Blue Moon of the year; the first occurred on Jan. 31, when we experienced the “Super Blue Blood Moon Lunar Eclipse.”
If you’re a Blue Moon fan, make sure to get an eyeful on Saturday; the next one won’t come until Halloween night in 2020, according to the Weather Channel.

An airplane flies in front of the Blue Moon of July 31, 2015, in this photo captured by skywatcher Chris Jankowski of Erie, Pennsylvania.

An airplane flies in front of the Blue Moon of July 31, 2015, in this photo captured by skywatcher Chris Jankowski of Erie, Pennsylvania.

Credit: Chris Jankowski

Thought to be called "blue" after an old english term meaning "betrayer," a Blue Moon is an extra full moon that occurs due to a quirk of the calendar. [<a href="http://www.space.com/16776-blue-moon-explained-infographic.html">See the full Blue Moon Infographic here</a>.]
Thought to be called “blue” after an old english term meaning “betrayer,” a Blue Moon is an extra full moon that occurs due to a quirk of the calendar. [See the full Blue Moon Infographic here.]

Credit: Karl Tate, SPACE.com

Blue Moons aren’t actually blue, and they don’t look different from any other full moon in the sky. The term, which has been around for hundreds of years, apparently originally signified something that’s absurd, but then shifted over time to refer to exceedingly rare events, Philip Hiscock wrote in a 2012 article for Sky & Telescope. (Interestingly, a Blue Moon previously meant the third full moon in a season that had four of them. This sense of an “extra” full moon morphed into the definition most people recognize today. Language is a slippery and changeable thing!)

 But Blue Moons aren’t all that rare, really: On average, they occur about once every 2.7 years. Blue Moons are possible because it takes Earth’s nearest neighbor 29.5 days to circle our planet, but each calendar month (except February) contains 30 or 31 days.

Editor’s note: If you capture an amazing photo of the Blue Moon or any other celestial sight and would like to share it with Space.com for a story or gallery, send images and comments to managing editor Tariq Malik at spacephotos@space.com.

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @SpacedotcomFacebook or Google+. Originally published on Space.com.

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Astronomer Announces He Has Discovered … Mars

Astronomer Announces He Has Discovered ... Mars

Mars will spend March in the southeastern pre-dawn sky – rising every morning about 3 a.m. local time.

Credit: Starry Night software

Astronomer Peter Dunsby just made a groundbreaking discovery, after noticing a very bright “star” pop up in his field of view at an observatory at the University of Cape Town that was not present two weeks prior.

Too bad Dunsby was perhaps thousands of years late … the bright object was the planet Mars. Though no one knows for sure who discovered the Red Planet, Galileo Galilei observed the giant red orb — whose diameter spans a whopping 4,222 miles (6,794 km) — in 1609; and Martian fascination has arguably not waned since.

Before realizing his marvelous mistake, Dunsby posted a note on the Astronomer’s Telegram, a publication for very short (under 4,000 characters) reports by astronomers, detailing his observations, in which he described the bright object had shown up between the Lagoon and Trifid nebulas, both nestled in the constellation Sagittarius.

About 40 minutres later, the Telegram issued a correction: “The object reported in ATel 11448 has been identified as Mars. Our sincere apologies for the earlier report and the inconvenience caused.”

And, not to let Dunsby go quietly into the night, the Telegram also sent out a cheeky tweet: “For Discovery of Mars.  Congratulations, Prof.  Peter Dunsby!”

 

 

As for why Mars showed up in Dunsby’s field of view, the blood-red planet, like Earth, makes a trek around the sun — though in a different orbit from our own.

Here’s the full telegram that Dunsby published March 20:

“Peter Dunsby (University of Cape Town) reports the detection of a very bright optical transient in the region between the Lagoon and Trifid Nebulae based on observations obtained from Cape Town on 20 March 2018, between 01:00 and 03:45 UT. The object was visible throughout the full duration of the observations and not seen when this field was observed previously (08 March 2018). The optical transients is at least first magnitude and is located at the following coordinates: RA (2000): 18h 04m 50s Declination (2000.0): -23d 29m 58s The coordinates are accurate to a few arcseconds. There is no obvious counterpart at this position on the Digital Sky Survey plates. Observations were obtained using an 80mm refractor. The attached URL show the image of this field (2.3 x 1.7 degrees, plate scale of 9 arcseconds per pixel) on 20 March 2018. The optical transient is the brightest star in the field. Further observations are strongly encouraged to establish the nature of this very bright optical transient. ”

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A Hungry Black Hole Devoured a Star, and Its ‘Burp’ Reveals How It Chowed Down

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A Hungry Black Hole Devoured a Star, and Its 'Burp' Reveals How It Chowed Down

An artist’s impression of the material falling into a black hole and the resulting jet it produced.

Credit: L. Calçada/ESO

A black hole that’s gobbling down a stellar meal is providing insight into how black holes devour matter and affect the evolution of galaxies.

Researchers found that the X-ray signal burst caused when a black hole shredded a passing star was repeated in the radio wavelengths nearly two weeks later. The radio echo most likely came from an exodus of highly energetic particles streaming out of the black hole, the researchers said.

In 2014, Las Cumbres Observatory’s All-sky Automated Survey for Supernovae, a collection of robotic telescopes spread across the globe, picked up signals from 300 million light-years away. The event, known as ASASSN-14li, occurred as a star was ripped to shreds after passing too close to a black hole. Multiple telescopes immediately turned to track the tidal disruption flare, a powerful explosion of electromagnetic energy caused by the destruction. After poring through about six months’ worth of data, Dheeraj Pasham, a researcher at the Massachusetts Institute of Technology, and Sjoert van Velzen, of Johns Hopkins University, found a pattern in the radio wavelength that nearly duplicates the X-ray signal. [No Escape: Dive Into a Black Hole (Infographic)]
“This is telling us the black hole feeding rate is controlling the strength of the jet it produces,” Pasham said in a statement. “A well-fed black hole produces a strong jet, while a malnourished black hole produces a weak jet or no jet at all. This is the first time we’ve seen a jet that’s controlled by a feeding supermassive black hole.”

When a star passes too close to a black hole, the enormous mass of the black hole exerts a tidal tug on the star. The forces are so strong that they can stretch and flatten the star, eventually tearing it to pieces. The stellar debris falls toward the black hole, where it is caught in the accretion disk, the collection of material that feeds the black hole. This is what happened in the case of ASASSN-14li.

The feeding process generates enormous energy visible in multiple wavelengths. Flares have been observed around other black holes in optical, ultraviolet, X-ray and radio wavelengths. As ultrahot material in the innermost regions of the accretion disk funnels toward the black hole, it produces X-ray emissions, while material farther out produces optical and ultraviolet emission. The source of radio emissions, however, has remained unknown.

“We know that the radio waves are coming from really energetic electrons that are moving in a magnetic field — that is a well-established process,” Pasham said. “The debate has been, where are these really energetic electrons coming from?”

One possibility is that, in the moments following the stellar explosion, a shock wave moves outward, energizing the plasma particles and causing them to emit radio waves. These radio waves would look dramatically different from the pattern of X-rays created by the infalling stellar material. But the signal Pasham and Van Velzen found in the radio is a 90-percent match with the X-ray signal.

“What we found basically challenges this paradigm,” Pasham said.

The close match suggests that the sources responsible for creating the radio waves and X-rays are related.

“It’s not a coincidence that this is happening,” Pasham said. “Clearly there’s a causal connection between this small region producing X-rays and this big region producing radio waves.”

The pair proposes that the radio waves are created by high-energy particles streaming out of the black hole soon after the behemoth begins to absorb material from the shredded star. Because the radio waves formed in a region tightly packed with other electrons, most of the signal was absorbed by those particles, the researchers said. The electrons responsible for the radio signal could escape only when they traveled downstream of the jet, producing the signal the scientists detected.

The researchers concluded that the strength of the jet must be controlled by the accretion rate, or the speed at which the black hole is consuming the stellar debris responsible for emitting X-rays.

The new observations, which were published March 19 in The Astrophysical Journal, may help scientists better characterize the physics of jet behavior. This, in turn, may help improve researchers’ understanding of how galaxies evolve.

Galaxies grow by producing new stars, but they can only do so under very cold temperatures. Jets emitted by black holes heat up the surrounding galaxies, temporarily halting stellar births. Pasham said the team’s new insight into jet production and black-hole accretion may help to simplify models of galaxy evolution.

“If the rate at which the black hole is feeding is proportional to the rate at which it’s pumping out energy, and if that really works for every black hole, it’s a simple prescription you can use in simulations of galaxy evolution,” Pasham said. “So this is hinting toward some bigger picture.”

Follow Nola Taylor Redd at @NolaTReddFacebook, or Google+. Follow us at @SpacedotcomFacebook or Google+. Originally published on Space.com.

 

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The Alien Planets of TRAPPIST-1 May Be Too Wet for Life

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The Alien Planets of TRAPPIST-1 May Be Too Wet for Life

An artist’s illustration of the view from one of the seven planets orbiting the red dwarf TRAPPIST-1, with several other worlds visible closer to the small, dim star.

Credit: N. Bartmann/spaceengine.org/ESO

The seven rocky planets circling the nearby star TRAPPIST-1 have lots of water, a new study suggests — perhaps too much to make them good bets for life.

All of the TRAPPIST-1 worlds likely harbor hundreds of Earth oceans’ worth of water on their surfaces, and the wettest ones may have over 1,000 times more of the stuff than our planet does, according to the study.

Surprisingly, this probably isn’t great news for the TRAPPIST-1 system’s life-hosting potential, study team members said. [Meet the 7 Earth-Size Exoplanets of TRAPPIST-1]

“Too much water can be a bad thing,” lead author Cayman Unterborn, a postdoctoral fellow in the School of Earth and Space Exploration at Arizona State University, told Space.com. “The TRAPPIST-1s are interesting, but maybe not for life.”
TRAPPIST-1 is a dim red dwarf star that lies about 39 light-years from Earth. Astronomers discovered three planets circling the star in 2016, and four more were announced a year later. Each of the seven worlds — which are known as TRAPPIST-1b, c, d, e, f, g and h — is about the same size as Earth. And three of the alien worlds (e, f and g) are thought to lie in TRAPPIST-1’s “habitable zone” — that just-right range of distances where liquid water could likely exist on a planet’s surface.

TRAPPIST-1 is about 2,000 times dimmer than the sun, so the red dwarf’s habitable zone is very close-in. Indeed, all seven TRAPPIST-1 planets lie closer to their star than Mercury does to the sun.

This diagram shows illustrations of the seven TRAPPIST-1 planets and compares some of their key characteristics with those of the rocky planets in our own solar system.

This diagram shows illustrations of the seven TRAPPIST-1 planets and compares some of their key characteristics with those of the rocky planets in our own solar system.

Credit: NASA/JPL-Caltech

All of the TRAPPIST-1 planets were discovered via the “transit method“; several different instruments noticed the tiny brightness dips that resulted when the worlds crossed their host star’s face. The magnitude of these dips revealed the sizes of the worlds. And astronomers have been able to estimate the planets’ masses, though not nearly as precisely, by studying how their transits have varied over time. (These variations occur as neighboring planets tug on one another gravitationally.)

With this mass and volume information in hand, Unterborn and his team used computer models to get a better idea of the composition of six of the TRAPPIST-1 worlds. (They didn’t deal with TRAPPIST-1h, the outermost planet, because not enough is known about it.)

This modeling work suggested that there’s a wetness gradient in the TRAPPIST-1 system. The innermost planets, b and c, are probably about 10 percent water by mass, whereas the wet stuff makes up at least 50 percent of the more distant f and g. The middle planets d and e fall somewhere in between.

All of these worlds are sopping wet, even at the low end of the gradient. For comparison, Earth is just 0.2 percent water by mass. Indeed, the TRAPPIST-1 planets are probably “water worlds,” with no land to break the monotony of wind and wave, Unterborn said.

If that is indeed the case, the odds of finding life in the system may not be great.

“With no exposed land, key geochemical cycles including the drawdown of carbon and phosphorus into oceanic reservoirs from continental weathering will be muted, thus limiting the size of the biosphere,” the researchers wrote in the new study, which was published online today (March 19) in the journal Nature Astronomy. “As such, although these planets may be habitable in the classical definition of the presence of surface water, any biosignature observed from this system may not be fully distinguishable from abiotic, purely geochemical sources.”

And all that water might shut down some key geological processes that could help life get a foothold, Unterborn said. For example, rocks in Earth’s mantle often become liquid after moving upward to a zone of lower pressure, where their melting point is lower. But such “decompression melting” may occur rarely, if at all, on the TRAPPIST-1 worlds, because the huge weight of the overlying global oceans jacks up mantle pressures so much.

 Without molten rock near the surface, there can be no volcanoes (at least not the kind we’re used to here on Earth). And without volcanoes, heat-trapping gases, such as carbon dioxide, may have a hard time reaching the atmosphere — which means the TRAPPIST-1 planets may have been subjected to a “runaway snowball” effect, Unterborn said. [Gallery: The Strangest Alien Planets]

Planets orbiting red dwarfs face other habitability challenges, many researchers have stressed. For example, if these worlds orbit tightly enough to be in the habitable zone, they’re almost certainly “tidally locked,” meaning they always show the same face to their parent star. So, one side of such planets may be boiling hot while the other is frigid. This problem could be mitigated by the presence of a thick atmosphere, which would circulate heat. But red dwarfs fire off lots of powerful flares, which may quickly strip away the atmospheres of habitable-zone worlds.

Such issues are heavily debated and studied, which isn’t surprising given the prevalence of red dwarfs: About 75 percent of the Milky Way’s stars are red dwarfs, so they likely harbor most of the galaxy’s real estate, habitable or otherwise.

The new study also sheds light on the formation and evolution of the TRAPPIST-1 system. For example, all seven planets currently lie inside the primordial “snow line” — the point beyond which it was cold enough for water to remain frozen when the worlds were taking shape. But the team’s results suggest that planets f, g and h actually formed beyond this boundary and migrated inward over time. Planets b and c, on the other hand, coalesced inside the primordial snow line. (It’s not clear where TRAPPIST-1d and e were born in relation to this line, which the researchers said was likely located somewhere between the newborn worlds c and f.)

Overall, the study indicates that red dwarf systems such as TRAPPIST-1 shouldn’t be thought of as just miniature versions of our own solar system, Unterborn said; their planets may form in slightly different ways, and/or on slightly different timescales.

“Understanding it from a planetary formation and evolution perspective, I think, is — for the public especially — a much more powerful way of selling TRAPPIST-1 than life,” he said. “No one likes being the wet blanket who says, ‘Well, actually, they’re not that great for life.’ But they’re really interesting, and we need to know these things in order to understand the planets that are likely to have life.”

Follow Mike Wall on Twitter @michaeldwall and Google+. Follow us @SpacedotcomFacebook or Google+. Originally published on Space.com.

Source:Space

Vernal Equinox 2018: Satellite Sees First Day of Spring

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Happy Spring and happy ! Today the length of night and day are nearly equal. The days will now become longer at the higher latitudes because it takes the sun longer to rise and set. More satellite imagery: http://goo.gl/eEwncX 

The National Oceanic and Atmospheric Administration (NOAA) celebrated a crisp start to spring today (March 20) in the Northern Hemisphere with a stunning view of Earth from sunset to sunrise.

NOAA officials tweeted the view of sunset on March 19 through sunrise March 20, taken with the agency’s GOES-East weather satellite.

“Happy Spring #Equinox and happy #firstdayofspring!” NOAA officials wrote. “Today the length of night and day are nearly equal. The days will now become longer at the higher latitudes because it takes the sun longer to rise and set.”

The Suomi NPP satellite took this image of the snow-covered northeastern United States and Canada on March 18, 2018. The image was created by combining the three color channels of the satellite's Visible Infrared Imaging Radiometer Suite (VIIRS) instrument.

The Suomi NPP satellite took this image of the snow-covered northeastern United States and Canada on March 18, 2018. The image was created by combining the three color channels of the satellite’s Visible Infrared Imaging Radiometer Suite (VIIRS) instrument.

Credit: NOAA/NESDIS

The vernal equinox occurs as the sun passes over the equator from Earth’s perspective and the Northern Hemisphere begins to tilt toward the sun, leading to longer days in the north and shorter days in the south. It marks the north’s first day of spring — snowy weather in some areas notwithstanding — and the beginning of fall for those in the Southern Hemisphere. While the day-to-day variations in weather are much more complex, the vernal equinox is a sign that warmer days are on the way.

The next big sun event for the Northern Hemisphere is the summer solstice on June 21, the longest day of the year, when Earth’s northern half is most directly tilted toward the sun. (It’s also the south’s winter solstice.)

A true-color view of Earth taken with the Suomi NPP satellite’s VIIRS instrument on March 19, 2018.

Credit: NOAA/NESDIS

Even better views are coming. NOAA launched what will be the new GOES-West spacecraft this month in partnership with NASA; the eagle-eyed satellite will help track extreme weather across the western United States and eastern Pacific Ocean as a counterpart to GOES-East. The satellite will move to its final GOES-West vantage point after about six months of preparing its instruments and running checks.

To see more NOAA imagery taken today, readers can visit https://www.nesdis.noaa.gov/content/imagery-and-data.

Source: Space

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