Archive for the ‘Astrophysics’ Category

How Weird Is Our Solar System?

Posted: August 24, 2014 by oldbrew in Astrophysics, solar system dynamics

Exoplanet: artist's interpretation [credit: NASA]

Exoplanet: artist’s interpretation
[credit: NASA]


Why haven’t exoplanet searches uncovered any solar systems similar to our own? Most appear to have fewer planets – although detection can be difficult – than ours, and often orbit a lot closer to their star than our planets do, plus there’s something else.

astrobites asks: ‘Earth and its Solar System compatriots all have nearly circular orbits, but many exoplanets orbit their stars on wildly eccentric paths. Is our home system strange? Or is our sense of the data skewed?’

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Mars-Earth comparison [image credit: Wikipedia]

Mars-Earth comparison
[image credit: Wikipedia]


It’s an old question, and investigations are hotting up.

Phys.org reports: ‘On October 19, 2014, Comet Siding Spring will pass by Mars only 132,000 km away—which would be like a comet passing about 1/3 of the distance between Earth and the Moon.’

In other words, very close. And NASA’s MAVEN probe will arrive at Mars just in time to see the show.

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A quantum of space hype at NASA?

Posted: August 8, 2014 by oldbrew in Astrophysics, innovation, Uncertainty

To boldly go... [image credit: Wikipedia]

To boldly go…
[image credit: Wikipedia]


Is NASA close to inventing a ‘quantum spaceship’?

The New Scientist quotes astronomer and blogger Phil Plait:

‘The internet has been buzzing about a paper published by a team of engineers at NASA claiming that they have built a device that creates thrust without propellant. There have been lots of articles written about it, it’s spawned a zillion tweets, and I’m getting plenty of emails asking me about it.’

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imageAfter ten years, five months, four days and six and a half billion kilometres,  the Rosetta space probe has arrived in orbit around Comet 67P.

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View from the Moon [credit: Wikipedia]

View from the Moon
[credit: Wikipedia]


First there was a report saying:
‘Computer model shows moon’s core surrounded by liquid and it’s caused by Earth’s gravity’

Of course the words ‘Computer model shows’ will ring a few alarm bells with some talkshop readers. Yes, it’s a theory based on a model, and the output of ‘climate models’ has led to many controversies so we may well be suspicious already.

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saturn2

From NASA:

Cassini took readings of the day-length indicator regarded as most reliable, the rhythm of natural radio signals from the planet. The results give 10 hours, 45 minutes, 45 seconds (plus or minus 36 seconds) as the length of time it takes Saturn to complete each rotation. Here’s the puzzle: That is about 6 minutes, or one percent, longer than the radio rotational period measured by the Voyager 1 and Voyager 2 spacecraft, which flew by Saturn in 1980 and 1981.

[Tallbloke notes that Venus has also slowed by an unexplained six minutes since 1997]

Cassini scientists are not questioning Voyager’s careful measurements. And they definitely do not think the whole planet of Saturn is actually rotating that much slower than it did two decades ago. Instead, they are looking for an explanation based on some variability in how the rotation deep inside Saturn drives the radio pulse.

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imageThe New Scientist reports the discovery of many more electron eating bacteria.

Geobacter and Shewanella were the first, now a further eight have been identified.

Kenneth Nealson from the University of South California “electrons must flow in order for energy to be gained. This is why, when someone suffocates another person, they are dead within minutes. You have stopped the supply of oxygen, so the electrons can no longer flow”. Nealsons team have grown electric bacteria on battery electrodes. Bacteria can either “eat” electrons from the higher voltage, or “breathe” electrons to the lower voltage electrode

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From Nature.com, a new paper which looks at how dry atmosphere’s of some exoplanets could cast doubt on long cherished notions about planet formation. Current mainstream thinking is that big planets form a long way out and migrate inwards. Perhaps the opposite may be the case, and ‘hot jupiters’ form near the parent star and increase the size of their orbits asthay gain angular moentum. Supporting this possibility, a recent paper by Poppenhaeger on the electromagnetic coupling of proto-planetary discs with the host star posit a slowing the stellar rotation and a shift of its angular momentum to the forming planets.

hd189733Scientists searching for worlds outside of the Solar System say that three such planets — distant gas giants that resemble Jupiter — are surprisingly dry.

The atmospheres of these exoplanets, known as ‘hot Jupiters’, contain between one-tenth and one-thousandth water vapour than predicted, measurements from the Hubble Space Telescope show. The findings, published 24 July in Astrophysical Journal Letters1, are at odds with theories of how planets form.

Madhusudhan thinks that it is possible, but not likely, that clouds are skewing his results. The particles would have to be high in the atmosphere, above the water vapour, for this to be true. That would place the clouds in the thinnest part of each exoplanet’s atmosphere, but they could be too heavy to stay aloft. The clouds would also need to survive in the wide range of temperatures the three planets’ atmospheres span — 900–2,200 ºC — which models can’t yet explain. “There is just no candidate cloud composition or physics that can do it,” he says.

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ImageReversals of the solar magnetic dipole in the light of observational data and simple dynamo models
V. V. Pipin., D. Moss, D. Sokoloff, and J. T. Hoeksema

Astronomy & Astrophysics, July 17th 2014

http://dx.doi.org/10.1051/0004-6361/201323319

ABSTRACT
Context. Observations show that the photospheric solar magnetic dipole usually does not vanish during the reversal of the solar magnetic field, which occurs in each solar cycle. In contrast, mean-field solar dynamo models predict that the dipole field does become zero. In a recent paper it was suggested that this contradiction could be explained as a large-scale manifestation of small-scale magnetic fluctuations of the surface poloidal field.
Aims. Our aim is to confront this interpretation with the available observational data.

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I came across this paper today while searching for the heat capacity of Venus near surface atmosphere, which is actually an ocean-like (in thermodynamic terms) supercritical fluid. It presages Harry Dale Huffman’s ‘rediscovery’ of the lapse rate calculation by four decades. Another paper, much more recent, (Bolmatov et al 2013) contains some theory which raises yet more questions about the reasons for Venus’ high surface temperature. So, greenhouse due to radiative proerties of co2 as Sagan claimed, lapse rate due to gravity and pressure as Nikolov and Zeller maintain, or the thermal properties of supercritical fluids and geothermal energy having a hard time escaping the lower atmosphere? Let the debate recommence!

venustemp1

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While browsing Ian Wilson’s excellent Astro-Climate Connection blog, I found a graphic showing the coincidence of El Nino with the alignment of the Lunar line of nodes (declination cycle) and line of apse (orbital precession), with the Sun. I’ve taken the liberty of adding my Solar – El Nino hypothesis to it: the proposal is that El Nino tends to be initiated as the cycle starts to decline steeply and initiated again at solar minimum as it ‘bottom’s out’. I’ll reproduce Ian’s accompanying text below the break but to get to the point, here’s  the result:

enso-lunisolar

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From Ian Wilson’s Astro-Climate Connection blog:

rranom.vic.0112.19917

The Moon’s orbit is tilted by approximately five degrees compared to the Earth-Sun plane. The net affect of this is that the strength of Lunar-tides at a given latitude on the Earth’s surface vary in strength over a cycle of 18.6 years. This 18.6 year Draconic cycle is also clearly evident in the small changes that take place in the rate of rotation of the Earth.

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I’m of the opinion that before getting into the complexity of numerical modelling, it’s wise to put considerable effort into trying to understand the physical processes at work in the climate system, and the origins of the energy flows that drive them. David Evans’ recent series of posts over at Jo Nova’s site have generated a lot of interesting discussion (despite being roundly ignored by Anthony Watts at WUWT), and I think we can shed some light on the ‘mysterious 11yr lag’ between solar input and climate response.

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kaptyenchart-600x383

A newly discovered planet pair orbiting a red dwarf a mere 13 light years from our solar system is in a near 2:5 orbital resonance. From National Geographic:

An international team of astronomers reports the discovery of two new planets orbiting Kapteyn’s star, a nearby red dwarf with a long history. One of its newly discovered worlds, dubbed Kapteyn b, circles the star at the right distance to allow seas to survive on its surface, where water is seen as a key ingredient of life as we know it.

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Andromeda galaxy [credit: Wikipedia]

Andromeda galaxy
[credit: Wikipedia]

Once again observation clashes with theory. This time it’s dwarf galaxies putting a spanner in the works of the ‘standard model’, says an international team of researchers.

“When we compared simulations … to what is observed by astronomers, we found a very substantial mismatch,” the lead author said.

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Speculative result based on a new toy at University of Göttingen

How Did the Moon Really Form?

Dan is a deputy news editor for Science.
Email Daniel

By Daniel Clery Thursday, June 5, 2014 – 3:45pm

Planetary scientists have long believed that our moon formed following a collision between Earth and another planet, but studies of Earth and moon rocks suggest otherwise. A new analysis of the composition of moon rocks brought back by Apollo astronauts may help finally resolve the mystery.

Science magazine article

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Big Bang [image credit: wikipedia]

Big Bang [image credit: wikipedia]

More ‘settled science’ on the ropes.

Quote: ‘These results are consistent with what would be expected from ordinary geometry if the Universe was not expanding, and are in contradiction with the drastic dimming of surface brightness predicted by the expanding Universe hypothesis.’

But Wikipedia says : ‘The Big Bang theory is the prevailing cosmological model for the early development of the universe. The key idea is that the universe is expanding.

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Hexagon found on Neptune?

Posted: May 19, 2014 by oldbrew in Astrophysics, solar system dynamics
Neptune - Earth comparison [credit: Wikipedia]

Neptune – Earth comparison [credit: Wikipedia]

Last year we had an interesting discussion here at the Talkshop on the topic of Saturn’s ‘polar hexagon’ which has been the subject of many photos and videos by the Cassini orbiter.

During the discussion Dr Carolyn Porco, a NASA scientist, dropped by to explain a few points about the properties of that phenomenon – images and comments here:

Stunning new image of Saturn’s polar hexagonal jet stream

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Image

High precision model of precession and nutation of the asteroids Ceres, Vesta, Eros, Steins, and Itokawa

A. Petit, J. Souchay and C. Lhotka

Observatoire de Paris and University of Rome

http://dx.doi.org/10.1051/0004-6361/201322905 (open access with registration)

“Abstract

Context. Several asteroids have recently been visited by spacecrafts that give us precious information and new constraints on their physical and rotational properties. In parallel, there are already several well-established theories to model the rotational motion of a rigid body, but accurate models of the rotational motion of asteroids have been poorly investigated so far. … “

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Big Bang  [credit: Wikipedia]

Big Bang
[credit: Wikipedia]


An orchestrated media blitz to push claims that ‘spectacular’ evidence of cosmic inflation had been detected by researchers could be turning sour only a few weeks later.

The story broke in a blaze of publicity – but before peer review:
‘First direct evidence for cosmic inflation announced’

Now it seems the BICEP2 results are looking a bit flabby according to one commentator close to the action.

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