Archive for the ‘Astrophysics’ Category

Solar wind at Mars [image credit: universetoday.com]


The researchers say ‘the solar wind likely only had a very small direct effect on the amount of Mars atmosphere that has been lost over time.’ This makes them suspect that ‘a magnetic field is not as important in shielding a planet’s atmosphere as the planet’s gravity itself.’ It was always hard to see how the magnetic shield theory worked when Venus with its dense atmosphere has little magnetism.

The Red Planet’s low gravity and lack of magnetic field makes its outermost atmosphere an easy target to be swept away by the solar wind, but new evidence from ESA’s Mars Express spacecraft shows that the Sun’s radiation may play a surprising role in its escape, reports Phys.org.

Why the atmospheres of the rocky planets in the inner solar system evolved so differently over 4.6 billion years is key to understanding what makes a planet habitable.

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Image credit: phys.org


When does absence of evidence become evidence of absence? Dark matter has never been detected despite years of effort. Here we have ‘a universal phenomenon that demands new explanations’, says the lead researcher. Galaxies in disc-shaped planes appear to mirror what we see with solar systems – like ours – and their planets.

An international team of astronomers led by the University of Basel in Switzerland has looked at the movement and distribution of satellite galaxies in the constellation Centaurus A and finds that their observations call into question the existence of dark matter, says The Space Reporter.

The findings are reported in the journal Science.

Dark matter is a hypothetical type of invisible matter that has never been directly observed because it does not emit or interact with electromagnetic radiation. Its existence has been inferred by its apparent influences on visible matter and light.

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Triton: Neptune’s odd moon

Posted: January 27, 2018 by oldbrew in Astrophysics, exploration
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Neptune and Triton (below) [credit: NASA]


Triton has the second-biggest ratio of moon-to-planet to Neptune, being only lower than the ratio between Earth and its own Moon. As well as having over 400 times the mass of any other Neptunian moon, Triton has some peculiarities about its environment, including the fact that it orbits backward to Neptune’s rotation and seems to have undergone a huge melt in the past, as Space.com explains. NASA believes it has similarities to Pluto. In 2006, a model published in Nature suggested Triton was originally a member of a binary system that orbited the sun.

Triton is the largest of Neptune’s moons. Discovered in 1846 by British astronomer William Lassell — just weeks after Neptune itself was found — the moon showed some strange characteristics as astronomers learned more about it.

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Jupiter-sized exoplanet [Wikipedia]


It seems the planetary structure of our solar system is an oddity compared to most of the exoplanetary systems so far discovered. On the other hand it’s easier to find planets close to their stars than those a long way away, so what is known so far might not be giving us the whole picture.

An international research team led by Université de Montréal astrophysicist Lauren Weiss has discovered that exoplanets orbiting the same star tend to have similar sizes and a regular orbital spacing, says Phys.org.

This pattern, revealed by new W. M. Keck Observatory observations of planetary systems discovered by the Kepler Telescope, could suggest that most planetary systems have a different formation history than the solar system.

Thanks in large part to the NASA Kepler Telescope, launched in 2009, many thousands of exoplanets are now known. This large sample allows researchers to not only study individual systems, but also to draw conclusions on planetary systems in general.

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cr-atmos

Illustration of cosmic rays interacting with the atmosphere. A proton with energy of 100 GeV interact at the top of the atmosphere and produces a cascade of secondary particles who ionize molecules when traveling through the air. One 100 GeV proton hits every m2 at the top of the atmosphere every second.

H/T GWPF: Researchers have claimed a breakthrough in understanding how cosmic rays from supernovas react with the sun to form clouds, which impact the climate on Earth.

The findings have been described as the “missing link” to help resolve a decades long controversy that has big implications for climate science.

Lead author, Henrik Svensmark, from The Technical University of Denmark has long held that climate models had greatly underestimated the impact of solar activity.

He says the new research identified the feedback mechanism through which the sun’s impact on climate was varied.

Professor Svensmark’s theories on solar impact have caused a great deal of controversy within the climate science community and the latest findings are sure to provoke new outrage.

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Star system has record eight exoplanets

Posted: December 14, 2017 by oldbrew in Astronomy, Astrophysics, News
Tags: ,

Kepler Space Telescope [credit: NASA]


The two nearest planets to the star Kepler-90 (90b and 90c) are very close to a 5:4 (i.e. first order) orbit ratio.

Nasa finds a distant star circled by eight planets, equal to the complement in our own Solar System, BBC News reports.

It’s the largest number of worlds ever discovered in a planetary system outside our own.

The star known as Kepler-90, is just a bit hotter and larger than the Sun; astronomers already knew of seven planets around it.

The newly discovered world is small enough to be rocky, according to scientists.

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Intense X-ray flares thought to be caused by a black hole devouring a star [credit: NASA]


Who’s afraid of the big bad black hole now? Its imagined powers have been seriously overrated, according to new research. This poses unexpected problems for theorists.

Black holes are famous for their muscle: an intense gravitational pull known to gobble up entire stars and launch streams of matter into space at almost the speed of light, says Phys.org.

It turns out the reality may not live up to the hype.

In a paper published today in the journal Science, University of Florida scientists have discovered these tears in the fabric of the universe have significantly weaker magnetic fields than previously thought.

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Although the author appears sold on the idea of trace gases controlling the temperature of planetary atmospheres, the discussion about planets and water is worth a look. The answer to the question may depend on more powerful space telescopes like the James Webb.

Wherever we find water on Earth, we find life writes Elizabeth Tasker at Many Worlds.

It is a connection that extends to the most inhospitable locations, such as the acidic pools of Yellowstone, the black smokers on the ocean floor or the cracks in frozen glaciers.

This intimate relationship led to the NASA maxim, “Follow the Water”, when searching for life on other planets.

Yet it turns out you can have too much of a good thing.

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Juno probe


There’s nothing like observation for contradicting, or supporting, theory and the Juno probe has already upset a few ideas that scientists had about Jupiter.

Since it established orbit around Jupiter in July of 2016, the Juno mission has been sending back vital information about the gas giant’s atmosphere, magnetic field and weather patterns, as Universe Today reports.

With every passing orbit – known as perijoves, which take place every 53 days – the probe has revealed more interesting things about Jupiter, which scientists will rely on to learn more about its formation and evolution.

During its latest pass, the probe managed to provide the most detailed look to date of the planet’s interior. In so doing, it learned that Jupiter’s powerful magnetic field is askew, with different patterns in its northern and southern hemispheres.

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Orbiting dust cloud – artists’ impression [credit: Karen L. Teramura]


An orbiting cloud of dust round ‘Tabby’s star’ may lack excitement for casual observers, but there it is – probably.

University of Arizona astronomer Huan Meng and co-authors have found the long-term dimming of KIC 8462852 — a main-sequence F-type star located in the constellation Cygnus, about 1,480 light-years from Earth — appears to be weaker at longer infrared (IR) wavelengths of light and stronger at shorter ultraviolet (UV) wavelengths, reports Sci-News.com.

Such reddening is characteristic of dust particles and inconsistent with more fanciful ‘alien megastructure’ concepts, which would evenly dim all wavelengths of light.

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Where is Planet 9? [credit: NASA]


Planetary theorists say super-Earths are commonly found in other planetary systems, but missing – so far – in our solar system. The evidence seems to be mounting, so is it just a case of tracking one down?

It might be lingering bashfully on the icy outer edges of our solar system, hiding in the dark, but subtly pulling strings behind the scenes: stretching out the orbits of distant bodies, perhaps even tilting the entire solar system to one side, says NASA’s Jet Propulsion Laboratory.

If a planet is there, it’s extremely distant and will stay that way (with no chance — in case you’re wondering — of ever colliding with Earth, or bringing “days of darkness”). It is a possible “Planet Nine” — a world perhaps 10 times the mass of Earth and 20 times farther from the sun than Neptune.

The signs so far are indirect, mainly its gravitational footprints, but that adds up to a compelling case nonetheless.

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Image credit: NASA


We now know that Saturn’s rings share a process with spiral galaxies, and the unique co-orbital pattern of two of its moons get some attention.

This view from NASA’s Cassini spacecraft shows a wave structure in Saturn’s rings known as the Janus 2:1 spiral density wave, reports Phys.org.

Resulting from the same process that creates spiral galaxies, spiral density waves in Saturn’s rings are much more tightly wound.

In this case, every second wave crest is actually the same spiral arm which has encircled the entire planet multiple times. This is the only major density wave visible in Saturn’s B ring.

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As the Talkshop reaches the milestone of 5 million visits, do we hear echoes of Scotty of Star Trek fame: ‘Ye cannae change the laws of physics’? Does fundamental mean universal – or could some ‘laws’ depend on where you look in the universe? Meanwhile Tallbloke is boldly going…somewhere… 😎

A study that will ‘test our understanding of how the Universe works, particularly outside the relatively narrow confines of our planet’ is being undertaken by an international team of researchers led by the University of Leicester, reports Phys.org.

The research probes whether the fundamental laws of physics are the same everywhere in the universe.

In their new study, the Leicester-led team assesses whether these laws are the same within the hot, dense conditions in the atmosphere of a dying white dwarf star as here on Earth.

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Sunspots [image credit: NASA]


One of the authors of the research says: “The results of our study show us that we have identified the governing parameters in our model”. Both climate and exoplanet research could benefit from the findings.

The Sun shines from the heavens, seemingly calm and unvarying. In fact, it doesn’t always shine with uniform brightness, but shows dimmings and brightenings, reports Phys.org.

Two phenomena alone are responsible for these fluctuations: the magnetic fields on the visible surface and gigantic plasma currents, bubbling up from the star’s interior.

A team headed by the Max Planck Institute for Solar System Research in Göttingen reports this result in today’s issue of Nature Astronomy. For the first time, the scientists have managed to reconstruct fluctuations in brightness on all time scales observed to date – from minutes up to decades.

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Credit: NASA


Among other findings, solar EUV [extreme ultraviolet radiation] turns out to be a greater planetary force than expected in this new research. Also the bow shock is greater the nearer Mars gets to the Sun during its orbit.

As the energetic particles of the solar wind speed across interplanetary space, their motion is modified by objects in their path. A study, based on data from ESA’s Mars Express orbiter, has thrown new light on a surprising interaction between the planet Mars and supersonic particles in the solar wind, reports Phys.org.

Scientists have long been aware that a feature known as a bow shock
forms upstream of a planet – rather like the bow of a ship, where the water is slowed and then diverted around the obstacle.

The bow shock marks a fairly sharp boundary where the solar wind slows suddenly as it begins to plough into a planet’s magnetosphere or outer atmosphere.

In the case of Mars, which does not generate a global magnetic field and has a thin atmosphere, the main obstacle to the solar wind is the ionosphere – a region of electrically charged particles in its upper atmosphere.

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These two 1977 vintage machines really are ‘cosmic overachievers’ as this Phys.org report calls them. Voyager 1 reached interstellar space in 2012, but the last science instrument is not due to be switched off until 2030.

Humanity’s farthest and longest-lived spacecraft, Voyager 1 and 2, achieve 40 years of operation and exploration this August and September.

Despite their vast distance, they continue to communicate with NASA daily, still probing the final frontier. Their story has not only impacted generations of current and future scientists and engineers, but also Earth’s culture, including film, art and music.

Each spacecraft carries a Golden Record of Earth sounds, pictures and messages. Since the spacecraft could last billions of years, these circular time capsules could one day be the only traces of human civilization.

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Jupiter is living up to its billing as a ‘planet on steroids’.
http://www.theguardian.com/science/2016/jun/04/probe-jupiter-juno

Planet Pailly

Last week, the Juno mission flew over Jupiter’s Great Red Spot and sent back some spectacular close-ups. But I’m not ready to talk about that. Not yet. I’m still catching up on the Juno news from two months ago.

Toward the end of May, NASA released a ton of fresh data from Juno, including new information about Jupiter’s auroras. Astro-scientists had previously known about two sources contributing to these auroras: the solar wind and the Io plasma torus. Now Juno may have discovered a third.

As Juno flew over Jupiter’s poles, it detected electrically charged particles flying up.

I can’t emphasize enough how weird this is. I wanted to write about it right away, but I held off doing this post because I was sure I must have misunderstood what I was reading.

Auroras are caused by electrically charged particles accelerated down toward a planet’s magnetic poles. These…

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Niagara Falls [image credit: Saffron Blaze / Wikipedia]


The author of this theory says “Jupiter and Saturn’s growth naturally pollutes the inner Solar System with water-rich planetesimals. In my mind the mechanism is very clear”. The theory does seem to bear a resemblance to this summary from the Hans Rickman Uppsala Astronomical Observatory.

Water on Earth, Mars and everywhere within the inner Solar System can be traced back to the rapid waist-expanding growth of Jupiter and Saturn, which knocked inwards a local population of icy planetesimals, as Sci-News reports.

This is according to a new model, which could also explain the current makeup of our modern asteroid belt.

Whilst Earth is often described as the blue marble, with over 70% of its surface covered in oceans, seas, rivers and lakes, water actually makes up less than 0.1% of our planet by mass.
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Credit: NASA


Extreme ultraviolet radiation (EUV) is perhaps an aspect of solar activity that gets less attention than it should. The authors make the interesting point in their introduction to the research article that ‘Although the total solar irradiance at Earth varies very little, the relative variance in the EUV is as large as the mean irradiance. This EUV light interacts with Earth’s thermosphere and stratosphere and may affect climate in a “top-down” process in regions such as northern Europe’.

A pair of researchers with Aberystwyth University in the U.K. has used data from NASA’s Solar Dynamics Observatory to learn more about how the sun’s corona behaves over differing stages of its 11-year cycle, reports Bob Yirka at phys.org.

In their paper published on the open access site Science Advances, Huw Morgan and Youra Taroyan describe attributes of the sun they observed over time and what they discovered about the “quiet corona” and its possible impact on us back here on Earth.

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