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Tuesday, August 9, 2016

Con cò bé bé biết đi xe đạp - CHUYỂN ĐỘNG BỐN PHƯƠNG





Thursday, July 21, 2016

UFO SIGHTINGS 2016 | Strange lights are recorded on Sky Lahore Pakistan

Outro oceano debaixo da terra na cidade de Juína MT

Outro oceano debaixo da terra na cidade de Juína MT



Pesquisadores descobriram um pequeno diamante que aponta para a existência de um grande depósito de água sob o manto da Terra. Seu volume poderia preencher três vezes os oceanos que conhecemos.


O principal autor do estudo, Graham Pearson, membro da Universidade de Alberta, no Canadá, disse que “Uma das razões da Terra ser um planeta dinâmico é a presença de água em seu interior. As mudanças da água dependem da forma como o mundo funciona”.

Depois de discutir a teoria há décadas, os cientistas relatam que finalmente encontraram um grande oceano no manto da Terra, três vezes maior do que os oceanos que conhecemos.

Esta descoberta surpreendente sugere que a água da superfície vem do interior do planeta como parte de um ciclo integrado da água, desbancando a teoria dominante de que a água foi trazida para a Terra por cometas gelados que passaram por aqui há milhões anos.

Cada vez mais os cientistas estão aprendendo sobre a composição de nosso planeta, compreendendo os acontecimentos relacionados às mudanças climáticas. O clima e o mar estão intimamente relacionados com a atividade tectônica que tem estado continuamente vibrando sob nossos pés.

Assim, os pesquisadores acreditam que a água na superfície da Terra poderia ter vindo do interior do planeta, tendo sido “impulsionada” para a superfície por meio da atividade geológica.


Nas profundezas desse oceano, corre um rio sem que a água doce se misture com a salgada.
Estudo Diz: Água subterrânea cobriria toda a superfície do planeta
Depois de inúmeros estudos e cálculos complexos para testar suas teorias, os pesquisadores acreditam ter encontrado um reservatório gigante de água numa zona de transição entre as camadas superior e inferior do manto, uma região que se encontra em algum lugar entre 400 e 660 km abaixo da superfície da terra.

Como sabemos, a água ocupa a maior parte da área de superfície do nosso planeta, que é paradoxalmente chamado de Terra. Embora seja verdade que, em comparação com o diâmetro terrestre a profundidade dos oceanos represente apenas uma fina camada semelhante à casca de uma cebola, descobrimos agora que a presença deste precioso líquido não está limitada à superfície visível.

Na realidade, a cerca de centenas de quilômetros de profundidade no subsolo há também enormes volumes de água, com uma importância fundamental para a compreensão da dinâmica geológica do planeta. Quase um oceano no centro da Terra.

A descoberta do oceano subterrâneo

A importante descoberta foi realizada por pesquisadores canadenses, que se basearam em um diamante encontrado numa rocha, em 2008, em uma área conhecida como Juína, no estado do Mato Grosso, Brasil.


A descoberta ocorreu por acidente, pois a equipe que estava, na realidade, à procura de outro mineral, ter comprado o diamante de alguns garimpeiros que o tinham encontrado através de uma coleta de cascalho realizada em um rio raso. Ao analisar a pedra detalhadamente um estudante descobriu, um ano depois, que o diamante, de apenas três milímetros de diâmetro e de pouco valor comercial, continha em sua composição um mineral chamado ringwoodite, que até agora só tinha sido encontrado em rochas de meteoritos e que contém significativa quantidade de água. No entanto, a confirmação final da presença deste mineral levou muitos anos, pois foi necessária a realização de vários testes e análises científicas.

De onde vem este mineral?

A análise detalhada da amostra encontrada revelou que, neste caso, o mineral não provinha de meteoritos, mas do manto da Terra, a uma profundidade de cerca de 410 e 660 km, em uma área que é conhecida como “zona de transição”.

Anteriormente, discutia-se muito sobre a possibilidade da existência de grandes quantidades de água muitos quilômetros abaixo do subsolo, mas nunca tinha sido antes demonstrada nenhuma prova real de tal teoria, que tem implicações muito importantes para a forma como entendemos os fenômenos geológicos planetários, pois acredita-se que este é o mineral mais abundante na zona do manto. Desta forma, como a amostra encontrada possui até 1,5 por cento de seu peso em água, pode-se afirmar que existem volumes de água realmente extraordinários, como um grande oceano.

Esta descoberta é, sem dúvida, uma das mais importantes realizadas no campo da geologia nos últimos anos, e forçará os peritos a modificarem, até certo ponto, a abordagem que se tem utilizado até agora para analisar fenômenos como vulcanismo, placas tectônicas e muitos outros processos de importância na compreensão da dinâmica da Terra – cujo nome, depois dessa descoberta, se tornou ainda mais paradoxal.


A peculiaridade desta descoberta é que esta água não existe em qualquer um dos três estados que conhecemos: líquido, sólido ou gasoso. A água foi encontrada em estruturas moleculares de formações rochosas no interior da Terra.

Uma concentração tão importante de água trás uma mudança significativa nas teorias relacionadas com a origem da água na superfície da Terra.


Esta descoberta é a prova de que nas partes mais profundas do nosso planeta, a água pode ser armazenada. Fato este que poderá colocar fim em uma polêmica de 25 anos, sobre se o centro da terra é seco ou úmido em algumas áreas.

A capacidade de armazenar água em seu interior não é exclusiva da Terra. Outros planetas, como Marte, podem conter grandes quantidades de água, algo que nos faz pensar se o planeta vermelho poderia abrigar vida.







Thursday, July 7, 2016

UFOS IN GERMANY - Alien ship UFO Seen In Germany Multiple witnesses 2016

Huge Cross Shaped Object In The Sky | UFO Sightings Cross Shaped Object ...





Monday, July 4, 2016

NASA Approves New Horizons Extended KBO Mission, Keeps Dawn at Ceres

NASA Approves New Horizons Extended KBO Mission, Keeps Dawn at Ceres:



New Horizons trajectory and the orbits of Pluto and 2014 MU69.


In an ‘Independence Day’ gift to a slew of US planetary research scientists, NASA has granted approval to nine ongoing missions to continue for another two years this holiday weekend.



The biggest news is that NASA green lighted a mission extension for the New Horizons probe to fly deeper into the Kuiper Belt and decided to keep the Dawn probe at Ceres forever, rather than dispatching it to a record breaking third main belt asteroid.



And the exciting extension news comes just as the agency’s Juno probe is about to ignite a July 4 fireworks display on July 4 to achieve orbit at Jupiter - detailed here.



“Mission approved!” the researchers gleefully reported on the probes Facebook and Twitter social media pages.



“Our extended mission into the #KuiperBelt has been approved. Thanks to everyone for following along & hopefully the best is yet to come.









The New Horizons spacecraft will now continue on course in the Kuiper Belt towards an small object known as 2014 MU69, to carry out the most distant close encounter with a celestial object in human history.



“Here's to continued success!”



The spacecraft will rendezvous with the ancient rock on New Year’s Day 2019.



Researchers say that 2014 MU69 is considered as one of the early building blocks of the solar system and as such will be invaluable to scientists studying the origin of our solar system how it evolved.



It was almost exactly one year ago on July 14, 2015 that New Horizons conducted Earth’s first ever up close flyby and science reconnaissance of Pluto - the most distant planet in our solar system and the last of the nine planets to be explored.















The immense volume of data gathered continues to stream back to Earth every day.



“The New Horizons mission to Pluto exceeded our expectations and even today the data from the spacecraft continue to surprise,” said NASA’s Director of Planetary Science Jim Green at NASA HQ in Washington, D.C.



“We’re excited to continue onward into the dark depths of the outer solar system to a science target that wasn’t even discovered when the spacecraft launched.”













While waiting for news on whether NASA would approve an extended mission, the New Horizons engineering and science team already ignited the main engine four times to carry out four course changes in October and November 2015, in order to preserve the option of the flyby past 2014 MU69 on Jan 1, 2019.



Green noted that mission extensions into fiscal years 2017 and 2018 are not final until Congress actually passes sufficient appropriation to fund NASA’s Planetary Science Division.



“Final decisions on mission extensions are contingent on the outcome of the annual budget process.”





Tough choices were made even tougher because the Obama Administration has cut funding for the Planetary Sciences Division - some of which was restored by a bipartisan majority in Congress for what many consider NASA ‘crown jewels.’



NASA’s Dawn asteroid orbiter just completed its primary mission at dwarf planet Ceres on June 30, just in time for the global celebration known as Asteroid Day.



“The mission exceeded all expectations originally set for its exploration of protoplanet Vesta and dwarf planet Ceres,” said NASA officials.



The Dawn science team had recently submitted a proposal to break out of orbit around the middle of this month in order to this conduct a flyby of the main belt asteroid Adeona.



Green declined to approve the Dawn proposal, citing additional valuable science to be gathered at Ceres.



The long-term monitoring of Ceres, particularly as it gets closer to perihelion – the part of its orbit with the shortest distance to the sun -- has the potential to provide more significant science discoveries than a flyby of Adeona,” he said.



Dawn is Earth’s first probe in human history to explore any dwarf planet, the first to explore Ceres up close and the first to orbit two celestial bodies.



The asteroid Vesta was Dawn’s first orbital target where it conducted extensive observations of the bizarre world for over a year in 2011 and 2012.



The mission is expected to last until at least later into 2016, and possibly longer, depending upon fuel reserves.



Dawn will remain at its current altitude at LAMO for the rest of its mission, and indefinitely afterward, even when no further communications are possible.



Green based his decision on the mission extensions on the biannual peer review scientific assessment by the Senior Review Panel.



The other mission extension - contingent on available resources - are: the Mars Reconnaissance Orbiter (MRO), Mars Atmosphere and Volatile EvolutioN (MAVEN), the Opportunity and Curiosity Mars rovers, the Mars Odyssey orbiter, the Lunar Reconnaissance Orbiter (LRO), and NASA’s support for the European Space Agency’s Mars Express mission.



Stay tuned here for Ken's continuing Earth and planetary science and human spaceflight news.



Ken Kremer











The post NASA Approves New Horizons Extended KBO Mission, Keeps Dawn at Ceres appeared first on Universe Today.

EARTH PLANET - Earth at Aphelion 2016

Earth at Aphelion 2016:



Sunset over Naples, Florida. Image credit: Dave Dickinson


Having a great July 4th? The day gives us another cause to celebrate, as the Earth reaches aphelion today, or our farthest point to our host star.



Aphelion is the opposite of the closest point of the year, known as perihelion. Note that the 'helion' part only applies to things in solar orbit, perigee/apogee for orbit 'round the Earth, apolune/perilune for orbit around the Moon, and so on. You'll hear the words apijove and perijove bandied about this week a bit, as NASA's Juno spacecraft enters orbit around Jupiter tonight. And there are crazier and even more obscure counterparts out there, such as peribothron and apobothron (orbiting a black hole) and apastron/periastron (orbiting a star other than our Sun). And finally, there's the one-size fits all generic periapsis and apoapsis, good for all occasions and ending pedantic arguments.



In the 21st century, aphelion for the Earth can actually fall anywhere from July 2nd to the 7th. The once every four year leap day is the primary driver in this oscillation, and the exclusion of a century leap day in 2100 — the first such exclusion since 1900 — will reset things even farther astray.







In 2016, the Moon reaches New on July 4th at 11:01 Universal Time (UT) just over five hours prior to aphelion, marking the start of lunation 1157. The sighting of the waxing crescent Moon also marks the end of the Muslim fasting month of Ramadan.



Earth reaches aphelion at 16:24 UT today, 1.0168 AU from the Sun. This year's close occurrence of aphelion versus a New Moon won't get topped until 2054, with an aphelion versus New Moon just 5 hours 6 minutes apart. The 2016 coincidence is also the closest since the start of the 21st century.



Fun fact: we're headed towards an aphelion maximum just 6,590 kilometers off of the mean on July 4th, 2019, the widest for the 21st century. Mean distance from the Sun at aphelion is 1.0167 AU (152,097,701 km). Aphelion for the Earth can range over a variation of 21,225 kilometers for the 21st century.







It's a happy circumstance that Earth reaches aphelion in our current epoch in the midst of northern hemisphere summer, and just a few weeks after the June solstice. The eccentricity of the Earth's orbit actually varies from near-circular to 0.0679 and back over the span of 413,000 years. In our current epoch, the eccentricity of our orbit is 0.017 and decreasing. Add this variation to changes in the axial tilt of our planet and orbital obliquity, and you have what are known as Milankovitch Cycles. One only has to look at Mars's wacky orbit with an eccentricity of 0.0934 to see what a difference it makes. Ironically, Mars reaches perihelion in October 29th, 2016, and will make a very close pass near next opposition pass in 2018.







Want to prove it for yourself? You can indeed 'observe' aphelion. The trick is to image the solar disk using the same rig and settings... about six months apart. At aphelion, the solar disk is 31.6' across, versus 32.7' across at perihelion. This variation is slight, but you can indeed see the subtle difference side by side:







Aphelion means a smaller apparent Sun, a good target for a total solar eclipse. Stick around until July 2nd, 2019 and you'll see just that, as a total solar eclipse occurs near aphelion for South America and the southern Pacific at 4 minutes and 33 seconds in central duration.







This month also sees another special treat, as all classical planets enter the evening sky.



More to come on that soon. For now, happy 4th of July, and merry aphelion!

The post Earth at Aphelion 2016 appeared first on Universe Today.

STARS DE L'UNIVERS - Stars Are The Universe’s Neat Freaks

Stars Are The Universe’s Neat Freaks:



The Andromeda Galaxy, viewed using conventional optics and IR. Credit: Kitt Peak National Observatory


Imagine, if you will, that the Universe was once a much dirtier place than it is today. Imagine also that what we see around us, a relatively clean and unobscured Universe, is the result of billions of years of stars behaving like giant celestial Roombas, cleaning up the space around them in preparation for our arrival. According to a set of recently published catalogues, which detail the latest findings from the ESA's Herschel Space Observatory, this description is actually quite fitting.



These catalogues represents the work of an international team of over 100 astronomers who have spent the past seven years analyzing the infrared images taken by the Herschel Astrophysical Terahertz Large Area Survey (Herschel-ATLAS). Presented earlier this week at the National Astronomy Meeting in Nottingham, this catalogue revealed that as early as 1 billion years ago, the Universe looked much different than it does today.



In order to put this research into context, it is important to understand the important of infrared astronomy. Prior to the deployment of missions like Herschel (which was launched in 2009), astronomers were unable to see a good portion of the light emitted by stars and galaxies. With roughly half of this light being absorbed by interstellar dust grains, research into the birth and lives of galaxies was difficult.







But thanks to surveys like Herschel ATLAS - as well NASA's Spitzer Space Telescope and the Wide-field Infrared Survey Explorer (WISE) - astronomers have been able to account for this missing energy. And what they have seen (especially from this latest survey) has been quite remarkable, presenting a Universe that is far denser than previously expected.



Last week (Friday, June 29th), during the final day of the National Astronomy Meeting, the first of the catalogues was presented. The images they showed gave all those present a glimpse of the unseen stars and galaxies that have existed over the last 12 billion years of cosmic history. In sum,  over half-a-million far-infrared sources have been spotted by the Herschel-ATLAS survey, and what they revealed was fascinating.



Many of these sources were galaxies that are nearby and similar to our own, and which are detectable using using conventional telescopes. The others were much more distant, their light taking billions of years to reach us, and were obscured by concentrations of cosmic dust. The most distant of these galaxies were roughly 12 billion light-years away, which means that they appeared as they would have 12 billion years ago.



Ergo, astronomers now know that 12 billion years ago (i.e. shortly after the Big Bang)., stars and galaxies were much dustier than they are now. They further concluded that the evolution of our galaxies since shortly after the Big Bang has essentially been a major clean-up effort, as stars gradually absorbed the dust that obscured their light, thus making it the more "visible" place it is today.







The data released by the survey includes several maps and additional files which were described in an article produced by Dr. Elisabetta Valiante and a research team from Cardiff University - titled "The Herschel-ATLAS Data Release 1 Paper I: Maps, Catalogues and Number Counts". As Dr. Valiante told Universe Today via email:



"Gas and dust are the main components of stars: they collapse to form stars and they are ejected at the end of stars’ life. The interesting thing that has been discovered thanks to the Herschel data is that the two phenomena are not in equilibrium. We knew this was true 10 billion years ago, but we expected, according to the current models, that some equilibrium was reached at more recent times. Instead, the amount of dust in galaxies 5 billion years ago was much larger than the amount we see in galaxies today: this was unexpected."
Until recently, such a survey would have been impossible due to the fact that many of these infrared sources would have  been invisible to astronomers. The reason for this, which was revealed by the survey, was that these galaxies were so dusty that they would have been virtually impossible to detect with conventional optics. What's more, their light would have been gravitationally magnified by intervening galaxies.



The huge size of the survey has also meant that changes that have occurred in galaxies - relatively recent in cosmic history - can be studied for the first time. For instance, the survey showed that even only one billion years in the past, a small fraction of the age of the universe, galaxies were forming stars at a faster rate and contained more dust than they do today.







Dr. Nathan Bourne - from the University of Edinburgh - is the lead author of another other paper describing the catalogues. As he told Universe Today via email:



“We can think of galaxies as big recycling machines. When they form, they accrete gas (mostly hydrogen and helium, with traces of lithium and a couple of other elements) from the universe around them, and they turn it into stars. As time goes on, the stars pump this gas back out into the galaxy, into the interstellar medium. Due to the nuclear processes within the stars, the gas is now enriched by heavy elements (what we call metals, though they include both metals and non-metals), and some of these form microscopic solid particles of dust, as a sort of by-product.



"But there are still stars forming, and the next generations of stars recycle this interstellar material, and now that it contains heavy elements and dust, things are a bit different, and planets can also form around the new stars, from accumulations of this heavy material. So, if you look at the big picture, when the first galaxies started forming within the first billion years after the Big Bang, they began using up the gas around them, and then while they are active they fill their interstellar medium up with gas and dust, but by the end of a galaxy's lifecycle, it has used up all this gas and dust, and you could say that it has cleaned itself.”
The catalogues and maps of the hidden universe are a triumph for the Herschel team. Despite the fact that the last information obtained by the Herschel observatory was back in 2013, the maps and catalogues produced from its years of service have become vital to astronomers. In addition to showing the Universe's hidden energy, they are also laying the groundwork for future research.







"Now we need to explain why there is dust where we did not expect to find it." said Valiante. "And to explain this, we need to change our theories about how the Universe evolves. Our data poses a challenge we have accepted, but we haven’t overcome it yet!"



"[W]e understand a lot more about how galaxies evolve," added Bourne, "about when most of the stars formed, what happens to the gas and dust as galaxies evolve, and how rapidly the star-forming activity in the Universe as a whole has faded in the latter half of the Universe's history. It's fair to say that this understanding comes from having a whole suite of different types of instruments studying different aspects of galaxies in complementary ways, but Herschel has certainly contributed a major part of that effort and will have a lasting legacy."



The implications of these findings are also likely to have a far-reaching effect, ranging from cosmology and astronomy, to perhaps shedding some light on that tricky Fermi paradox. Could it be intelligent life that emerged billions of years ago didn't venture to other star systems because they couldn't see them? Just a thought...



This data release from the H-ATLAS team was coordinated with releases made in late June from the Herschel Extragalactic Project (HELP) team and the Herschel Multi-tiered Extragalactic Survey (HerMES). H-ATLAS and HerMES are parts of the EU Research Executive Agency's HELP program, which brings together various extragalactic surveys carried out by Herschel and combines them with major surveys conducted by other observatories to give the Herschel mission a lasting legacy.



Further Reading: Royal Astronomical Society, ESA

The post Stars Are The Universe’s Neat Freaks appeared first on Universe Today.

Juno Snaps Final View of Jovian System Ahead of ‘Independence Day’ Orbital Insertion Fireworks Tonight – Watch Live

Juno Snaps Final View of Jovian System Ahead of ‘Independence Day’ Orbital Insertion Fireworks Tonight – Watch Live:



This is the final view taken by the JunoCam instrument on NASA's Juno spacecraft before Juno's instruments were powered down in preparation for orbit insertion. Juno obtained this color view on June 29, 2016, at a distance of 3.3 million miles (5.3 million kilometers) from Jupiter.  See timelapse movie below.  Credits: NASA/JPL-Caltech/MSSS


After a nearly 5 year odyssey across the solar system, NASA’s solar powered Juno orbiter is all set to ignite its main engine late tonight and set off a powerful charge of do-or-die fireworks on America’s ‘Independence Day’ required to place the probe into orbit around Jupiter - the ‘King of the Planets.’



To achieve orbit, Juno must will perform a suspenseful maneuver known as ‘Jupiter Orbit Insertion’ or JOI tonight, Monday, July 4, upon which the entire mission and its fundamental science hinges. There are no second chances!



You can be part of all the excitement and tension building up to and during that moment, which is just hours away - and experience the ‘Joy of JOI’ by tuning into NASA TV tonight!



Watch the live webcast on NASA TV featuring the top scientists and NASA officials starting at 10:30 p.m. EDT: https://www.nasa.gov/nasatv









And for a breathtaking warm-up act, Juno’s on board public outreach JunoCam camera snapped a final gorgeous view of the Jovian system showing Jupiter and its four largest moons, dancing around the largest planet in our solar system.



The newly released color view image was taken on June 29, 2016, at a distance of 3.3 million miles (5.3 million kilometers) from Jupiter.



It shows a dramatic view of the clouds bands of Jupiter, dominating a spectacular scene that includes the giant planet's four largest moons -- Io, Europa, Ganymede and Callisto.



NASA also released this new time-lapse JunoCam movie today:



https://youtu.be/kjfQCTat-8s



Video caption: Juno's Approach to Jupiter: After nearly five years traveling through space to its destination, NASA's Juno spacecraft will arrive in orbit around Jupiter on July 4, 2016. This video shows a peek of what the spacecraft saw as it closed in on its destination. Credits: NASA/JPL-Caltech/MSSS





The spacecraft is approaching Jupiter over its north pole, affording an unprecedented perspective on the Jovian system - “which looks like a mini solar system,” says Juno Principal Investigator and chief scientist Scott Bolton, from the Southwest Research Institute (SwRI) in San Antonio, Tx, at today’s media briefing at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif.



The 35-minute-long main engine burn is preprogrammed to start at 11:18 p.m. EDT. It is schedule to last until approximately 11:53 p.m.



JOI is required to slow the spacecraft so it can be captured into the gas giant’s orbit as it closes in over the north pole.









Juno is the fastest spacecraft ever to arrive at Jupiter and is moving at over 165,000 mph relative to Earth and 130,000 mph relative to Jupiter.



After a five-year and 2.8 Billion kilometer (1.7 Billion mile) outbound trek to the Jovian system and the largest planet in our solar system and an intervening Earth flyby speed boost, the moment of truth for Juno is now inexorably at hand.



Signals traveling at the speed of light take 48 minutes to reach Earth, said Rick Nybakken, Juno project manager from NASA's Jet Propulsion Laboratory, at the media briefing.





So the main engine burn, which is fully automated, will already be over for some 13 minutes before the first indications of the outcome reach Earth via a series of Doppler shifts and tones.



“The engine burn will slow Juno by 542 meters/seconds and is fully automated as it approaches over Jupiter’s North Pole,” explained Nybakken.



“The long five year cruise enabled us to really learn about the spacecraft and how it operates.”



As it travels through space, the basketball court sized Juno is spinning like a windmill with its 3 giant solar arrays.



“Juno is also the farthest mission to rely on solar power. The solar panels are 60 square meters in size. And although they provide only 1/25th the power at Earth, they still provide over 500 watts of power at Jupiter.”



The protective cover that shields Juno's main engine from micrometeorites and interstellar dust was opened on June 20.



During a 20 month long science mission - entailing 37 orbits lasting 14 days each – the probe will plunge to within about 3000 miles of the turbulent cloud tops and collect unprecedented new data that will unveil the hidden inner secrets of Jupiter’s origin and evolution.



“Jupiter is the Rosetta Stone of our solar system,” says Bolton. “It is by far the oldest planet, contains more material than all the other planets, asteroids and comets combined and carries deep inside it the story of not only the solar system but of us. Juno is going there as our emissary — to interpret what Jupiter has to say.”



During the orbits, Juno will probe beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet's origins, structure, atmosphere and magnetosphere.







The $1.1 Billion Juno was launched on Aug. 5, 2011 from Cape Canaveral, Florida atop the most powerful version of the Atlas V rocket augmented by 5 solid rocket boosters and built by United Launch Alliance (ULA). That same Atlas V 551 version just launched MUOS-5 for the US Navy on June 24.









Along the way Juno made a return trip to Earth on Oct. 9, 2013 for a flyby gravity assist speed boost that enabled the trek to Jupiter.



The flyby provided 70% of the velocity compared to the Atlas V launch, said Nybakken.



During the Earth flyby (EFB), the science team observed Earth using most of Juno’s nine science instruments since the slingshot also serves as an important dress rehearsal and key test of the spacecraft’s instruments, systems and flight operations teams.



Juno also went into safe mode - something the team must avoid during JOI.



What lessons were learned from the safe mode event and applied to JOI, I asked?



“We had the battery at 50% state of charge during the EFB and didn't accurately predict the sag on the battery when we went into eclipse. We now have a validated high fidelity power model which would have predicted that sag and we would have increased the battery voltage,” Nybakken told Universe Today



“It will not happen at JOI as we don't go into eclipse and are at 100% SOC. Plus the instruments are off which increases our power margins.”





Junocam has took some striking images of Earth as it sped over Argentina, South America and the South Atlantic Ocean, as it came within 347 miles (560 kilometers) of the surface.

For example the dazzling portrait of our Home Planet high over the South American coastline and the Atlantic Ocean.



For a hint of what’s to come, see our colorized Junocam mosaic of land, sea and swirling clouds, created by Ken Kremer and Marco Di Lorenzo

















Stay tuned here for Ken's continuing Earth and Planetary science and human spaceflight news.



Ken Kremer















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THE UNIVERSE - Messier 17 (M17) – the Omega Nebula

Messier 17 (M17) – the Omega Nebula:



The rose-coloured star forming region Messier 17, captured by the Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile.. Credit: ESO/Subaru Telescope (NAOJ)/Hubble Space Telescope


Welcome back to Messier Monday! In our ongoing tribute to the great Tammy Plotner, we take a look at the Messier 17 nebula – aka. The Omega Nebula (and a few other names).



In the 18th century, while searching the night sky for comets, French astronomer Charles Messier began noticing a series of “nebulous objects” in the night sky. Hoping to ensure that other astronomers did not make the same mistake, he began compiling a list of these objects,. Known to posterity as the Messier Catalog, this list has come to be one of the most important milestones in the research of Deep Sky objects.



One of these is the star-forming nebula known as Messier 17 - or as it's more famously known, the Omega Nebula (or Swan Nebula, Checkmark Nebula, and Horseshoe Nebula). Located in the Sagittarius constellation, this beautiful nebula is considered one of the brightest and most massive star-forming regions of our galaxy.



Description:

From its position in space some 5,000 to 6,000 light years from Earth, the "Omega" nebula occupies a region as large as 40 light years across, with its brightest porition covering a 15 light year expanse. Like many nebulae, this giant cosmic cloud of interstellar matter is a starforming region in the Sagittarius or Sagittarius-Carina arm of our Milky Way galaxy.



What you see is the hot hydrogen gas that is illuminated when its particles are excited by the hottest of the stars that have just formed within the nebula. Also, some of the light is being reflected by the nebula's own dust. These remain hidden by dark obscuring material, and we know their presence only through the detection of their infrared radiation.







In an study titled "Interstellar Weather Vanes: GLIMPSE Mid-Infrared Stellar-Wind Bowshocks in M17 and RCW49", astronomer Matthew S. Povich (et al.) of the University of Wisconsin-Madison said of M17:



"We report the discovery of six infrared stellar-wind bowshocks in the Galactic massive star formation regions M17 and RCW49 from Spitzer GLIMPSE (Galactic Legacy Infrared Mid-Plane Survey Extraordinaire) images. The InfraRed Array Camera (IRAC) on the Spitzer Space Telescope clearly resolves the arc-shaped emission produced by the bowshocks. We use the stellar SEDs to estimate the spectral types of the three newly-identified O stars in RCW49 and one previously undiscovered O star in M17. One of the bowshocks in RCW49 reveals the presence of a large-scale flow of gas escaping the HII region. Radiation-transfer modeling of the steep rise in the SED of this bowshock toward longer mid-infrared wavelengths indicates that the emission is coming principally from dust heated by the star driving the shock. The other 5 bowshocks occur where the stellar winds of O stars sweep up dust in the expanding HII regions."
Is Messier 17 still actively producing stars? You bet. Even protostars have been discovered hiding in its folds. As M. Nielbock (et al), wrote in 2008:



"For the first time, we resolve the elongated central infrared emission of the large accretion disk in M 17 into a point-source and a jet-like feature that extends to the northeast. We regard the unresolved emission as to originate from an accreting intermediate to high-mass protostar. In addition, our images reveal a weak and curved southwestern lobe whose morphology resembles that of the previously detected northeastern one. We interpret these lobes as the working surfaces of a recently detected jet interacting with the ambient medium at a distance of 1700 AU from the disk centre. The accreting protostar is embedded inside a circumstellar disk and an envelope causing a visual extinction. This and its K-band magnitude argue in favour of an intermediate to high-mass object, equivalent to a spectral type of at least B4. For a main-sequence star, this would correspond to a stellar mass of 4 M."
How many new stars lay hidden inside? Far more than the famous Orion nebula may contain. So says a 2013 study produced by L. Eisa (et al):



"The complex resembles the Orion Nebula/KL region seen nearly edge-on: the bowl-shaped ionization blister is eroding the edge of the clumpy molecular cloud and triggering massive star formation, as evidenced by an ultra-compact HII region and luminous protostars. Only the most massive members of the young NGC 6618 stellar cluster exciting the nebula have been characterized, due to the comparatively high extinction. Near-infrared imagery and spectroscopy reveal an embedded cluster of about 100 stars earlier than B9. These studies did not cover the entire cluster, so even more early stars may be present. This is substantially richer than the Orion Nebula Cluster which has only 8 stars between O6 and B9."

History of Observation:

The Omega Nebula was first discovered by Philippe Loys de Cheseaux and is just one of the six nebulae in his documents. As he wrote of his discovery:



"Finally, another nebula, which has never been observed. It is of a completely different shape than the others: It has perfectly the form of a ray, or of the tail of a comet, of 7' length and 2' broadth; its sides are exactly parallel and rather well terminated, as are its two ends. Its middle is whiter than the border." Because De Cheseaux's work wasn't widely read, Charles Messier independently rediscovered it on June 3, 1764 and cataloged it in his own way: "In the same night, I have discovered at little distance of the cluster of stars of which I just have told, a train of light of five or six minutes of arc in extension, in the shape of a spindle, and in almost the same as that in the girdle of Andromeda; but of a very faint light, not containing any star; one can see two of them nearby which are telescopic and placed parallel to the Equator: in a good sky one perceives very well that nebula with an ordinary refractor of 3 feet and a half. I have determined its position in right ascension of 271d 45' 48", and its declination of 16d 14' 44" south."
By historical accounts, it was Sir William Herschel who may have truly had a little bit of insight on what this object might one day mean when he observed it on his own and reported:



"1783, July 31. A very singular nebula; it seems to be the link to join the nebula in Orion to others, for this is not without a possibility of being stars. I think a great deal more of light and a much higher power would be of service. 1784, June 22 (Sw. 231). A wonderful nebula. Very much extended, with a hook on the preceding [Western] side; the nebulosity of the milky kind; several stars visible in it, but they seem to have no connection with the nebula, which is far more distant. I saw it only through short intervals of flying clouds and haziness; but the extent of the light including the hook is above 10'. I suspect besides, that on the following [Eastern] side it goes on much farther and diffuses itself towards the north and south. It is not of equal brightness throughout and has one or more places where the milky nebulosity seems to degenerate into the resolvable [mottled] kind; such a one is that just following the hook towards the north. Should this be confirmed on a very fine night, it would bring on the step between these two nebulosities which is at present wanting, and would lead us to surmise that this nebula is a stupendous stratum of immensely distant fixed stars, some of whose branches come near enough to us to be visible as a resolvable nebulosity, while the rest runs on to so great a distance as only to appear under the milky form."
So where did the name "Omega Nebula" come from? That credit goes to John Herschel, who stated in his observing notes:



"The figure of this nebula is nearly that of the Greek capital Omega, somewhat distorted and very unequally bright. It is remarkable that this is the form usually attributed to the great nebula in Orion, though in that nebula I confess I can discern no resemblence whatever to the Greek letter. Messier perceived only the bright preceding branch of the nebula now in question, without any of the attached convolutions which were first noticed by my Father. The chief peculiarities which I have observed in it are, 1st, the resolvable knot in the following portion of the bright branch, which is in a considerable degree insulated from the surrounding nebula; strongly suggesting the idea of an absorption of nebulous matter; and 2ndly, the much feebler and smaller knot in the north preceding end of the same branch, where the nebula makes a sudden bend at an acute angle. With a view to a more exact representation of this curious nebula, I have at different times taken micrometrical measures of the relative places of the stars in and near it, by which, when laid down on the chart, its limits may be traced and identified, as I hope soon to have better opportunity to do than its low situation in this latitudes will permit."

Locating Messier 17:

Because M17 is both large and quite bright, its distinctive "2" shape isn't hard to make out in optics of any size. For binoculars and image correct finderscopes, try starting with the constellation of Aquila and begin tracing the stars down the eagle’s back to Lambda. When you reach that point, continue to extend the line through to Alpha Scuti, then southwards towards Gamma Scuti. M16 is slightly more than 2 degrees (about a fingerwidth) southwest of this star.



If you are in a dark sky location, you can also identify it easily in binoculars by starting at the M24 "Star Cloud", north of Lambda Sagittari (the teapot lid star), and simply scanning north. This nebula is bright enough to even cut through moderately light polluted skies with ease, but don't expect to see it when the Moon is nearby. You'll enjoy the rich starfields combined with an interesting nebula in binoculars, while telescopes will easily begin resolving the interior stars.



And here are the quick facts on M17 for your convenience:



Object Name: Messier 17

Alternative Designations: M17, NGC 6618, Omega, Swan, Horseshoe, or Lobster Nebula

Object Type: Open Star Cluster with Emission Nebula

Constellation: Sagittarius

Right Ascension: 18 : 20.8 (h:m)

Declination: -16 : 11 (deg:m)

Distance: 5.0 (kly)

Visual Brightness: 6.0 (mag)

Apparent Dimension: 11.0 (arc min)



And be sure to enjoy this video from the European Southern Observatory (ESO) that shows this nebula in all its glory:



https://youtu.be/YE5YEVU65pA



We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.



Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.

The post Messier 17 (M17) – the Omega Nebula appeared first on Universe Today.

L'IMAGE NASA DU JOUR - Firefly Trails and the Summer Milky Way

Firefly Trails and the Summer Milky Way:

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2016 July 2


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: A camera fixed low to a tripod on a northern summer's eve captured the series of images used in this serene, southern Ontario skyscape. The lakeside view frames our fair galaxy above calm water and the night's quintessential luminous apparitions. But the trails of light are neither satellite glint, nor meteor flash, nor auroral glow. In the wide-field composite constructed with four consecutive 15 second exposures, a pulsing firefly enters at the right, first wandering toward the camera, then left and back toward the lake, the central Milky Way rising in the background.

L'IMAGE NASA DU JOUR - Counting Down to Juno's Arrival at Jupiter

Counting Down to Juno's Arrival at Jupiter: A model of the Juno spacecraft is seen at a news briefing on Thursday, June 30, 2016, at the Jet Propulsion Laboratory. The Juno mission will arrive at Jupiter July 4, 2016, to orbit the planet for 20 months and collect data on the planetary core, map the magnetic field, and measure the amount of water and ammonia in the atmosphere.


Original enclosures:


L'IMAGE NASA DU JOUR - Juno Closes in on Jupiter

Juno Closes in on Jupiter: This is the final view taken by the JunoCam instrument on NASA's Juno spacecraft before Juno's instruments were powered down in preparation for orbit insertion on July 4.


Original enclosures:


Saturday, July 2, 2016

DIAMETERS OF THE PLANETS - What Are The Diameters of the Planets?

What Are The Diameters of the Planets?:



Planets in the Solar System. Image credit: NASA/JPL/IAU


The planets of our Solar System vary considerably in size and shape. Some planets are small enough that they are comparable in diameter to some of our larger moons - i.e. Mercury is smaller than Jupiter's moon Ganymede and Saturn's moon Titan. Meanwhile, others like Jupiter are so big that they are larger in diameter than most of the others combined.



In addition, some planets are wider at the equator than they are at the poles. This is due to a combination of the planets composition and their rotational speed. As a result, some planets are almost perfectly spherical while others are oblate spheroids (i.e. experience some flattening at the poles). Let us examine them one by one, shall we?



Mercury:

With a diameter of 4,879 km (3031.67 mi), Mercury is the smallest planet in our Solar System. In fact, Mercury is not much larger than Earth's own Moon - which has a diameter of 3,474 km (2158.64 mi). At 5,268 km (3,273 mi) in diameter, Jupiter's moon of Ganymede is also larger, as is Saturn's moon Titan - which is 5,152 km (3201.34 mi) in diameter.







As with the other planets in the inner Solar System (Venus, Earth, and Mars), Mercury is a terrestrial planet, which means it is composed primarily of metals and silicate rocks that are differentiated into an iron-rich core and a silicate mantle and crust.



Also, due to the fact that Mercury has a very slow sidereal rotational period, taking 58.646 days to complete a single rotation on its axis, Mercury experiences no flattening at the poles. This means that the planet is almost a perfect sphere and has the same diameter whether it is measured from pole to pole or around its equator.



Venus:

Venus is often referred to as Earth's "sister planet", and not without good reason. At 12,104 km (7521 mi) in diameter, it is almost the same size as Earth. But unlike Earth, Venus experiences no flattening at the poles, which means that it almost perfectly circular. As with Mercury, this is due to Venus' slow sidereal rotation period, taking 243.025 days to rotate once on its axis.







Earth:

With a mean diameter of 12,756 km (7926 mi), Earth is the largest terrestrial planet in the Solar System and the fifth largest planet overall. However, due to flattening at its poles (0.00335), Earth is not a perfect sphere, but an oblate spheroid. As a result, its polar diameter differs from its equatorial diameter, but only by about 41 km (25.5 mi)



In short, Earth measures 12713.6 km (7900 mi) in diameter from pole to pole, and 12756.2 km (7926.3 mi) around its equator. Once again, this is due to Earth's sidereal rotational period, which takes a relatively short 23 hours, 58 minutes and 4.1 seconds to complete a single rotation on its axis.



Mars:

Mars is often referred to as "Earth's twin"; and again, for good reason. Like Earth, Mars experiences flattening at its poles (0.00589), which is due to its relatively rapid sidereal rotational period (24 hours, 37 minutes and 22 seconds, or 1.025957 Earth days).



As a result, it experiences a bulge at its equator which leads to a variation of 40 km (25 mi) between its polar radius and equatorial radius. This works out to Mars having a mean diameter of 6779 km (4212.275 mi), varying between 6752.4 km (4195.75 mi) between its poles and 6792.4 km (4220.6 mi) at its equator.









Jupiter:

Jupiter is the largest planet in the Solar System, measuring some 139,822 km (86,881 mi) in diameter. Again, this its mean diameter, since Jupiter experiences some rather significant flattening at the poles (0.06487). This is due to its rapid rotational period, with Jupiter taking just 9 hours 55 minutes and 30 seconds to complete a single rotation on its axis.





Combined with the fact that Jupiter is a gas giant, this means the planet experiences significant bulging at its equator. Basically, it varies in diameter from 133,708 km (83,082.3 mi) when measured from pole to pole, and 142,984 km (88,846 mi) when measured around the equator. This is a difference of 9276 km (5763.8 mi), one of the most pronounced in the Solar System.



 Saturn:

With a mean diameter of 116,464 km (72,367.37 mi), Saturn is the second largest planet in the Solar System. Like Jupiter, it experiences significant flattening at its poles (0.09796) due to its high rotational velocity (10 hours and 33 minutes) and the fact that it is a gas giant. This means that it varies in diameter from 108,728 km (67560.447 mi) when measured at the poles and 120,536 km (74,897.6 mi) when measured at the equator. This is a difference of almost 12,000 km, the greatest of all planets.







Uranus:

Uranus has a mean diameter of 50,724 km (31,518.43 mi), making it the third largest planet in the Solar System. But due to its rapid rotational velocity - the planet takes 17 hours 14 minutes and 24 seconds to complete a single rotation - and its composition, the planet experiences a significant polar flattening (0.0229). This leads to a variation in diameter of 49,946 km (31,035 mi) at the poles and 51,118 km (31763.25 mi) at the equator - a difference of 1172 km (728.25 mi).



Neptune:

Lastly, there is Neptune, which has a mean diameter of 49,244 km (30598.8 mi). But like all the other gas giants, this varies due to its rapid rotational period (16 hours, 6 minutes and 36 seconds) and composition, and subsequent flattening at the poles (0.0171). As a result, the planet experiences a variation of 846 km (525.68 mi), measuring 48,682 km (30249.59 mi) at the poles and 49,528 km (30775.27 mi) at the equator.



In summary, the planets of our Solar System vary in diameter due to differences in their composition and the speed of their rotation. In short, terrestrial planets tend to be smaller than gas giants, and gas giants tend to spin faster than terrestrial worlds. Between these two factors, the worlds we know range between near-perfect spheres and flattened spheres.



We have written many articles about the Solar System here at Universe Today. Here's Interesting Facts about the Solar SystemHow Long Is A Day On The Other Planets Of The Solar System?, What Are the Colors of the Planets?, How Long Is A Year On The Other Planets?, What Is The Atmosphere Like On Other Planets?, and How Strong is Gravity on Other Planets?



For more information of the planets, here is a look at the eight planets and some fact sheets about the planets from NASA.



Astronomy Cast has episodes on all the planets. Here is Mercury to start out with.

The post What Are The Diameters of the Planets? appeared first on Universe Today.

Huge Plasma Tsunamis Hitting Earth Explains Third Van Allen Belt

Huge Plasma Tsunamis Hitting Earth Explains Third Van Allen Belt:



This is an illustration to explain the dynamics of the ultra-relativistic third Van Allen radiation belt. Credit: Andy Kale


The dynamic relationship between Earth and the Sun two sides. The warmth from the Sun makes life on Earth possible, but the rest of the Sun's intense energy pummels the Earth, and could destroy all life, given the chance. But thanks to our magnetosphere, we are safe.



The magnetosphere is our protective shield. It's created by the rotation of the molten outer core of the Earth, composed largely of iron and nickel. It absorbs and deflects plasma from the solar wind. The interactions between the magnetosphere and the solar wind are what create the beautiful auroras at Earth's poles.







In the inner regions of Earth's magnetosphere are the Van Allen belts, named after their discoverer James Van Allen. They consist of charged particles, mostly from the Sun, and are held in place by the magnetosphere. Usually, there are two such belts.







But the output from the Sun is not stable. There are periods of intense energy output from the Sun, and when that happens, a third, transient belt can be created. Up until now, the nature of this third belt has been a puzzle. New research from the University of Alberta has shown how this phenomena can happen.



Researchers have shown how a so-called "space tsunami" can create this third belt. Intense ultra-low frequency plasma waves can transport the outer part of the radiation belt into interplanetary space, and create the third, transient belt.



The lead author for this study is physics professor Ian Mann from the University of Alberta, and former Canada Research Chair in Space Physics. "Remarkably, we observed huge plasma waves," said Mann. "Rather like a space tsunami, they slosh the radiation belts around and very rapidly wash away the outer part of the belt, explaining the structure of the enigmatic third radiation belt."



This new research also sheds light on how these "tsunamis" help reduce the threat of radiation to satellites during other space storms. "Space radiation poses a threat to the operation of the satellite infrastructure upon which our twenty-first century technological society relies," adds Mann. "Understanding how such radiation is energized and lost is one of the biggest challenges for space research."



It's not just satellites that are at risk of radiation though. When solar wind is most active, it can create extremely energetic space storms. They in turn create intense radiation in the Van Allen belts, which drive electrical currents that could damage our power grids here on Earth. These types of storms have the potential to cause trillions of dollars worth of damage.



A better understanding of this space radiation, and an ability to forecast it, are turning out to be very important to our satellite operations, and to our exploration of space.



The Van Allen belts were discovered in 1958, and classified into an inner and an outer belt.







In 2013, probes reported a third belt which had never before been seen. It lasted a few weeks, then vanished, and its cause was not known. Thanks to Mann and his team, we now know what was behind that third belt.



"We have discovered a very elegant explanation for the dynamics of the third belt," says Mann. "Our results show a remarkable simplicity in belt response once the dominant processes are accurately specified."



An understanding of the radiation in and around Earth and the Van Allen belts is of growing importance to us, as we expand our presence in space. Our technological society relies increasingly on satellite communications, and on GPS satellites. Radiation in the form of high-energy electrons can wreak havoc on satellites. In fact, this type of radiation is sometimes referred to as a satellite killer. Satellites require robust design to be protected from them.



Organizations like the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) and the International Living with a Star (ILWS) Program are attempts to address the threat that radiation poses to our system of satellites.





The post Huge Plasma Tsunamis Hitting Earth Explains Third Van Allen Belt appeared first on Universe Today.

Centaurs Keep Their Rings From Greedy Gas Giants

Centaurs Keep Their Rings From Greedy Gas Giants:



Artist's impression of what the rings of the asteroid Chariklo would look like from the small body's surface. The rings' discovery was a first for an asteroid. Credit: ESO/L. Calçada/Nick Risinger (skysurvey.org)


When we think of ring systems, what naturally comes to mind are planets like Saturn. It's beautiful rings are certainly the most well known, but they are not the only planet in our Solar System to have them. As the Voyager missions demonstrated, every planet in the outer Solar System - from Jupiter to Neptune - has its own system of rings. And in recent years, astronomers have discovered that even certain minor planets - like the Centaur asteroids 10199 Chariklo and 2006 Chiron - have them too.



This was a rather surprising find, since these objects have such chaotic orbits. Given that their paths through the Solar System are frequently altered by the powerful gravity of gas giants, astronomers have naturally wondered how a minor planet could retain a system of rings. But thanks to a team of researchers from the Sao Paulo State University in Brazil, we may be close to answering that question.



In a study titled "The Rings of Chariklo Under Close Encounters With The Giant Planets", which appeared recently in The Astrophysical Journal, they explained how they constructed a model of the Solar System that incorporated 729 simulated objects. All of these objects were the same size as Chariklo and had their own system of rings. They then went about the process of examining how interacting with gas giant effected them.







To break it down, Centaurs are a population of objects within our Solar System that behave as both comets and asteroids (hence why they are named after the hybrid beasts of Greek mythology). 10199 Chariklo is the largest known member of the Centaur population, a possible former Trans-Neptunian Object (TNO) which currently orbits between Saturn and Uranus.



The rings around this asteroid were first noticed in 2013 when the asteroid underwent a stellar occultation. This revealed a system of two rings, with a radius of 391 and 405 km and widths of about 7 km 3 km, respectively. The absorption features of the rings showed that they were partially composed of water ice. In this respect, they were much like the rings of Jupiter, Saturn, Uranus and the other gas giants, which are composed largely of water ice and dust.
This was followed by findings made in 2015 that indicated that 2006 Chiron - another major Centaur - could have a ring of its own. This led to further speculation that there might be many minor planets in our Solar System that have a system of rings. Naturally, this was a bit perplexing to astronomers, since rings are fragile structures that were thought to be exclusive to the gas giants of our System.
As Professor Othon Winter, the lead researcher of the Sao Paulo team, told Universe Today via email:
"At first it was a surprise to find a Centaur with rings, since the Centaurs have chaotic orbits wandering between the giant planets and having frequent close encounters with them. However, we have shown that in most of the cases the ring system can survive all the close encounters with the giant planets. Therefore,  Centaurs with rings might be much more common than we thought before."
For the sake of their study, Winter and his colleagues considered the orbits of 729 simulated clones of Chariklo as they orbited the Sun over the course of 100 million years. From this, Winter and his colleagues found that each Centaur averaged about 150 close encounters with a gas giant, within one Hill radius of the planet in question. As Winter described it:



"The study was made in two steps. First we considered a set of more than 700 clones of Chariklo. The clones had initial trajectories that were slightly different from Chariklo for statistical purposes (since we are dealing with chaotic trajectories) and computationally simulated their orbital evolution forward in time (to see their future) and also backward in time (to see their past). During these simulations we archived the information of all the close encounters (many thousands) they had with each of the giant planets."
"In the second step, we performed simulations of each one of the close encounters found in the first step, but now including a disk of particles around Chariklo  (representing the ring particles). Then, at the end of each simulation we analyzed what happened to the particles. Which ones were removed from Chariklo  (escaping its gravitational field)? Which ones were strongly disturbed (still orbiting around Chariklo)? Which ones did not suffer any significant effect?"

In the end, the simulations showed that in 90 percent of the cases, the rings of the Centaurs survived their close encounters with gas giants, whereas they were disturbed in 4 percent of cases, and were stripped away only 3 percent of the time. Thus, they concluded that if there is an efficient mechanism that creates the rings, then it is strong enough to let Centaurs keep them.







More than that, their research would seem to indicate that what was considered unique to certain planetary bodies may actually be more commonplace. "It reveals that our Solar System is complex not just as whole or for large bodies," said Winter, "but even small bodies may show complex structures and even more complex temporal evolution."



The next step for the research team is to study ring formation, which could show that they in fact picking them up from the gas giants themselves. But regardless of where they come from, its becoming increasingly clear that Centaurs like 10199 Chariklo are not alone. What's more, they aren't giving up their rings anytime soon!



Further Reading: iopscience.iop.org

The post Centaurs Keep Their Rings From Greedy Gas Giants appeared first on Universe Today.

STARS AND BLACK HOLES - A Star Is About To Go 2.5% The Speed Of Light Past A Black Hole

A Star Is About To Go 2.5% The Speed Of Light Past A Black Hole:



Artist’s impression of the star S2 passing very close to the supermassive black hole at the centre of the Milky Way. Credit: ESO


Since it was first discovered in 1974, astronomers have been dying to get a better look at the Supermassive Black Hole (SBH) at the center of our galaxy. Known as Sagittarius A*, scientists have only been able to gauge the position and mass of this SBH by measuring the effect it has on the stars that orbit it. But so far, more detailed observations have eluded them, thanks in part to all the gas and dust that obscures it.



Luckily, the European Southern Observatory (ESO) recently began work with the GRAVITY interferometer, the latest component in their Very Large Telescope (VLT). Using this instrument, which combines near-infrared imaging, adaptive-optics, and vastly improved resolution and accuracy, they have managed to capture images of the stars orbiting Sagittarius A*. And what they have observed was quite fascinating.



One of the primary purposes of GRAVITY is to study the gravitational field around Sagittarius A* in order to make precise measurements of the stars that orbit it. In so doing, the GRAVITY team - which consists of astronomers from the ESO, the Max Planck Institute, and multiple European research institutes - will be able to test Einstein's theory of General Relativity like never before.







In what was the first observation conducted using the new instrument, the GRAVITY team used its powerful interferometric imaging capabilities to study S2, a faint star which orbits Sagittarius A* with a period of only 16 years. This test demonstrated the effectiveness of the GRAVITY instrument - which is 15 times more sensitive than the individual 8.2-metre Unit Telescopes the VLT currently relies on.



This was an historic accomplishment, as a clear view of the center of our galaxy is something that has eluded astronomers in the past. As GRAVITY’s lead scientist, Frank Eisenhauer - from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany - explained to Universe Today via email:



"First, the Galactic Center is hidden behind a huge amount of interstellar dust, and it is practically invisible at optical wavelengths. The stars are only observable in the infrared, so we first had to develop the necessary technology and instruments for that. Second, there are so many stars concentrated in the Galactic Center that a normal telescope is not sharp enough to resolve them. It was only in the late 1990' and in the beginning of this century when we learned to sharpen the images with the help of speckle interferometry and adaptive optics to see the stars and observe their dance around the central black hole."
But more than that, the observation of S2 was very well timed. In 2018, the star will be at the closest point in its orbit to the Sagittarius A*  - just 17 light-hours from it. As you can see from the video below, it is at this point that S2 will be moving much faster than at any other point in its orbit (the orbit of S2 is highlighted in red and the position of the central black hole is marked with a red cross).



https://youtu.be/-aKVw2Ol-Ek



When it makes its closest approach, S2 will accelerate to speeds of almost 30 million km per hour, which is 2.5% the speed of light. Another opportunity to view this star reach such high speeds will not come again for another 16 years - in 2034. And having shown just how sensitive the instrument is already, the GRAVITY team expects to be able make very precise measurements of the star's position.



In fact, they anticipate that the level of accuracy will be comparable to that of measuring the positions of objects on the surface of the Moon, right down to the centimeter-scale. As such, they will be able to determine whether the motion of the star as it orbits the black hole are consistent with Einstein's theories of general relativity.



"[I]t is not the speed itself to cause the general relativistic effects," explained Eisenhauer, "but the strong gravitation around the black hole. But the very  high orbital speed is a direct consequence and measure of the gravitation, so we refer to it in the press release because the comparison with the speed of light and the ISS illustrates so nicely the extreme conditions.







As recent simulations of the expansion of galaxies in the Universe have shown, Einstein's theories are still holding up after many decades. However, these tests will offer hard evidence, obtained through direct observation. A star traveling at a portion of the speed of light around a supermassive black hole at the center of our galaxy will certainly prove to be a fitting test.



And Eisenhauer and his colleagues expect to see some very interesting things. "We hope to see a "kick" in the orbit." he said. "The general relativistic effects increase very strongly when you approach the black hole, and when the star swings by, these effects will slightly change the direction of the

orbit."



While those of us here at Earth will not be able to "star gaze" on this occasion and see R2 whipping past Sagittarius A*, we will still be privy to all the results. And then, we just might see if Einstein really was correct when he proposed what is still the predominant theory of gravitation in physics, over a century later.



Further Reading: eso.org

The post A Star Is About To Go 2.5% The Speed Of Light Past A Black Hole appeared first on Universe Today.

MASSES OF THE PLANETS - What are the Different Masses of the Planets?

What are the Different Masses of the Planets?:



Planets and other objects in our Solar System. Credit: NASA.


It is a well known fact that the planets of the Solar System vary considerably in terms of size. For instance, the planets of the inner Solar System are smaller and denser than the gas/ice giants of the outer Solar System. And in some cases, planets can actually be smaller than the largest moons. But a planet's size is not necessarily proportional to its mass. In the end, how massive a planet is has more to do with its composition and density.



So while a planet like Mercury may be smaller in size than Jupiter's moon Ganymede or Saturn's moon Titan, it is more than twice as massive than they are. And while Jupiter is 318 times as massive as Earth, its composition and density mean that it is only 11.21 times Earth's size. Let's go over the planet's one by one and see just how massive they are, shall we?



Mercury:

Mercury is the Solar System's smallest planet, with an average diameter of 4879 km (3031.67 mi). It is also one of its densest at 5.427 g/cm3, which is second only to Earth. As a terrestrial planet, it is composed of silicate rock and minerals and is differentiated between an iron core and a silicate mantle and crust. But unlike its peers (Venus, Earth and Mars), it has an abnormally large metallic core relative to its crust and mantle.



All told, Mercury's mass is approximately 0.330 x 1024 kg, which works out to 330,000,000 trillion metric tons (or the equivalent of 0.055 Earths). Combined with its density and size, Mercury has a surface gravity of 3.7 m/s² (or 0.38 g).







Venus:

Venus, otherwise known as "Earth's Sister Planet", is so-named because of its similarities in composition, size, and mass to our own. Like Earth, Mercury and Mars, it is a terrestrial planet, and hence quite dense. In fact, with a density of 5.243 g/cm³, it is the third densest planet in the Solar System (behind Earth and Mercury). Its average radius is roughly 6,050 km (3759.3 mi), which is the equivalent of 0.95 Earths.



And when it comes to mass, the planet weighs in at a hefty 4.87 x 1024 kg, or 4,870,000,000 trillion metric tons. Not surprisingly, this is the equivalent of 0.815 Earths, making it the second most massive terrestrial planet in the Solar System. Combined with its density and size, this means that Venus also has comparable gravity to Earth - roughly 8.87 m/s², or 0.9 g.



Earth:

Like the other planets of the inner Solar System, Earth is also a terrestrial planet, composed of metals and silicate rocks differentiated between an iron core and a silicate mantle and crust. Of the terrestrial planets, it is the largest and densest, with an average radius of 6,371.0 km (3,958.8 mi) and a mean of density of 5.514 g/cm3.







And at 5.97 x 1024 kg (which works out to 5,970,000,000,000 trillion metric tons) Earth is the most massive of all the terrestrial planets. Combined with its size and density, Earth experiences the surface gravity that we are all familiar with - 9.8 m/s², or 1 g.



Mars:

Mars is the third largest terrestrial planet, and the second smallest planet in our Solar System. Like the others, it is composed of metals and silicate rocks that are differentiated between a iron core and a silicate mantle and crust. But while it is roughly half the size of Earth (with a mean diameter of 6792 km, or 4220.35 mi), it is only one-tenth as massive.



In short, Mars has a mass of 0.642 x1024 kg, which works out to 642,000,000 trillion metric tons, or roughly 0.11 the mass of Earth. Combined with its size and density - 3.9335 g/cm³ (which is roughly 0.71 times that of Earth's) - Mars has a surface gravity of 3.711 m/s² (or 0.376 g).



Jupiter:

Jupiter is the largest planet in the Solar System. With a mean diameter of 142,984 km, it is big enough to fit all the other planets (except Saturn) inside itself, and big enough to fit Earth 11.8 times over. But with a mass of 1898 x 1024 kg (or 1,898,000,000,000 trillion metric tons), Jupiter is more massive than all the other planets in the Solar System combined - 2.5 times more massive, to be exact.







However, as a gas giant, it has a lower overall density than the terrestrial planets. It's mean density is 1.326 g/cm, but this increases considerably the further one ventures towards the core. And though Jupiter does not have a true surface, if one were to position themselves within its atmosphere where the pressure is the same as Earth's at sea level (1 bar), they would experience a gravitational pull of 24.79 m/s2 (2.528 g).



Saturn:

Saturn is the second largest of the gas giants; with a mean diameter of 120,536 km, it is just slightly smaller than Jupiter. However, it is significantly less massive than its Jovian cousin, with a mass of 569 x 1024 kg (or 569,000,000,000 trillion metric tons). Still, this makes Saturn the second most-massive planet in the Solar System, with 95 times the mass of Earth.



Much like Jupiter, Saturn has a low mean density due to its composition. In fact, with an average density of 0.687 g/cm³, Saturn is the only planet in the Solar System that is less dense than water (1 g/cm³).  But of course, like all gas giants, its density increases considerably the further one ventures towards the core. Combined with its size and mass, Saturn has a "surface" gravity that is just slightly higher than Earth's - 10.44 m/s², or 1.065 g.







Uranus:

With a mean diameter of 120,536 km, Uranus is the third largest planet in the Solar System. But with a mass of 86.8 x 1024 kg (86,800,000,000 trillion metric tons) it is the fourth most massive - which is 14.5 times the mass of Earth. This is due to its mean density of 1.271 g/cm3, which is about three quarters of what Neptune's is. Between its size, mass, and density, Uranus' gravity works out to 8.69 m/s2, which is 0.886 g.



Neptune:

Neptune is significantly larger than Earth; at 49,528 km, it is about four times Earth's size. And with a mass of 102 x 1024 kg (or 102,000,000,000 trillion metric tons) it is also more massive - about 17 times more to be exact. This makes Neptune the third most massive planet in the Solar System; while its density is the greatest of any gas giant (1.638 g/cm3). Combined, this works out to a "surface" gravity of 11.15 m/s2 (1.14 g).



As you can see, the planets of the Solar System range considerably in terms of mass. But when you factor in their variations in density, you can see how a planets mass is not always proportionate to its size. In short, while some planets may be a few times larger than others, they are can have many, many times more mass.



We have written many interesting articles about the planets here at Universe. For instance, here's Interesting Facts About the Solar System, What are the Colors of the Planets?, What are the Signs of the Planets?, How Dense are the Planets?, and What are the Diameters of the Planets?.



For more information, check out Nine Planets overview of the Solar System, NASA's Solar System Exploration, and use this site to find out what you would weigh on other planets.



Astronomy Cast has episodes on all of the planets. Here's Episode 49: Mercury to start!

The post What are the Different Masses of the Planets? appeared first on Universe Today.