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Meteorite accumulation at Victoria Crater.
Credit: Image courtesy of University of Stirling
The lack of liquid water on the surface of Mars today has been demonstrated by new evidence in the form of meteorites on the Red Planet examined by an international team of planetary scientists.
In a study led by the University of Stirling, an international team of researchers has found the lack of rust on the meteorites indicates that Mars is incredibly dry, and has been that way for millions of years.
The discovery, published in Nature Communications, provides vital insight into the planet’s current environment and shows how difficult it would be for life to exist on Mars today.
Mars is a primary target in the search for life outside Earth, and liquid water is the most important pre-requisite for life.
Dr Christian Schröder, Lecturer in Environmental Science and Planetary Exploration at the University of Stirling and Science Team Collaborator for the Mars Exploration Rover Opportunity mission, said:
“Evidence shows that more than 3 billion years ago Mars was wet and habitable. However, this latest research reaffirms just how dry the environment is today. For life to exist in the areas we investigated, it would need to find pockets far beneath the surface, located away from the dryness and radiation present on the ground.”
A study published last year, which used data from the Curiosity Rover investigating Gale crater on Mars, suggested that very salty liquid water might be able to condense in the top layers of Martian soil overnight.
“But, as our data show, this moisture is much less than the moisture present even in the driest places on Earth,” explains Dr Schröder.
Using data from the Mars Exploration Rover Opportunity, the scientists examined a cluster of meteorites at Meridiani Planum — a plain just south of the planet’s equator and at a similar latitude to Gale crater.
Dr Schröder and his team have for the first time calculated a chemical weathering rate for Mars, in this case how long it takes for rust to form from the metallic iron present in meteorites.
This chemical weathering process depends on the presence of water. It takes at least 10 and possibly up to 10,000 times longer on Mars to reach the same levels of rust formation than in the driest deserts on Earth and points to the present-day extreme aridity that has persisted on Mars for millions of years.
Christian Schröder, Phil A. Bland, Matthew P. Golombek, James W. Ashley, Nicholas H. Warner, John A. Grant. Amazonian chemical weathering rate derived from stony meteorite finds at Meridiani Planum on Mars. Nature Communications, 2016; 7: 13459 DOI: 10.1038/ncomms13459 | 0.814006 | 3.859702 |
1. What kind of orbits do comets have?
- Highly elliptical.
2. Describe the tail of a comet.
- Points away from sun
- Two types:
- Straight ion tail
- Blue coloured
- Ionised carbon monoxide.
- Ionised by solar wind
- Dust Tail
- Lighter coloured
- Produced by radiation pressures pushing particles out of the nucleus
- Reflects sunlight
Click here for an interactive demonstration of comet tails.
3. Name two categories of comets.
- Short period
- < 200 years.
- Originate from Kuiper Belt.
- e.g. Halley’s comet.
- Giotto probe 1986.
- Long period
- Originate fro Ort Cloud.
- Paths clockwise or anticlockwise.
- Orbits highly inclined to the ecliptic.
- Originate vast distances from the sun.
- e.g. Hale-Bopp.
4. What is the Kuiper Belt?
- Where short period comets originate.
- Disc shaped region of icy bodies.
- Beyond Neptune.
- 30-50 AU from Sun.
5. What is the Ort Cloud?
- Where long period comets originate.
- Spherical region of Cometary nuclei.
- Roughly 50,000 AU from sun.
6. What is the difference between a meteoroid and a meteorite?
- A meteoroid is a small rocky irregular lump in the solar system.
- Any rock between micrometres and several meters can be catagorised as a meteoroid
- Anything bigger than 10m is an asteroid
- When a meteoroid enters the earth’s atmosphere it turns into a meteor.
- If it survives and impacts the ground it is termed a meteorite.
7. Name three origins of meteoroids.
- Broken fragments of colliding asteroids.
- Impacts with the surface of the moon or Mars.
- The dust tails of comets.
8. How fast can a meteoroid’s orbit be?
9. What is a Meteoroid shower?
- They can be a dramatic increase in the number of meteors observed when the earth passes through a meteoroid stream left by a comet.
- This is a meteor shower.
10. What causes meteors to appear as light streaks in the sky?
- When a Meteoroid enters the earth’s atmosphere it becomes a meteor.
- Friction between a meteor and the surrounding air produce heat and light and can be seen as light streaks in the night sky.
11. What is a fireball?
- Meteors with a bright magnitude of -3 or less.
12. What is the radiant?
- A point in the night sky from which meteors appear to diverge from.
13. Describe the classification of meteorites.
- Stony Iron
14. How do we name meteor showers?
- Named after the constellation in which the radiant is found.
15. Name 4 annual meteor showers and when they occur.
- Occurs in the constellation of Perseus
- Occurs in August
- Occurs in Leo
- In Gemini
- In December.
- In January
16. What is the definition of an NEO?
- A near Earth object is an asteroid or comet who’s trajectory might bring them closer to earth than 0.3 AU
17. What is a PHO?
- An object that has an orbit that brings them closer to earth than 0.05AU.
18. Give examples of collisions between astronomical bodies in the solar system.
- The Moon
- Arizona (Barringer Crater)
- Chicxulub crater (Mexico)
- Believed to have caused extinction of dinosaurs.
- Unusual Rotations
- Venus rotates backwards
- Uranus rotates sideways.
- Apollo mission
- Evidence moon was part of earth
- Giant Impact Hypothesis.
- Evidence moon was part of earth
- Comet Shoemaker-levy
- Collided with Jupiter
- Astronomers around the world witnessed this.
- Tunguska Event
- Explosion of comet/ asteroid in the sky
19. Why do we need to monitor PHO’s?
- Because if one hits us that is powerful enough, it could have catastrophic consequences for life on Earth especially if the PHO’s are larger than 1km.
20. What is the Torino Scale? | 0.883122 | 3.792552 |
When the Hubble Space Telescope photographed the apparent exoplanet Fomalhaut b in 2008, it was regarded as the first visible light image obtained of a planet orbiting another star. The breakthrough was announced by a research team led by Paul Kalas of the University of California, Berkeley. The planet was estimated to be approximately the size of Saturn, but no more than three times Jupiter’s mass, or perhaps smaller than Saturn according to some other studies, and might even have rings. It resides within a debris ring which encircles the star Fomalhaut, about 25 light-years away.
Another team at Princeton, however, has just announced that they believe the original findings are in error, and that the planet is actually a dust cloud, based on new observations by the Spitzer Space Telescope. Their paper has just been accepted by the Astrophysical Journal.
According to the abstract:
The nearby A4-type star Fomalhaut hosts a debris belt in the form of an eccentric ring, which is thought to be caused by dynamical influence from a giant planet companion. In 2008, a detection of a point-source inside the inner edge of the ring was reported and was interpreted as a direct image of the planet, named Fomalhaut b. The detection was made at ~600–800 nm, but no corresponding signatures were found in the near-infrared range, where the bulk emission of such a planet should be expected. Here we present deep observations of Fomalhaut with Spitzer/IRAC at 4.5 µm, using a novel PSF subtraction technique based on ADI and LOCI, in order to substantially improve the Spitzer contrast at small separations. The results provide more than an order of magnitude improvement in the upper flux limit of Fomalhaut b and exclude the possibility that any flux from a giant planet surface contributes to the observed flux at visible wavelengths. This renders any direct connection between the observed light source and the dynamically inferred giant planet highly unlikely. We discuss several possible interpretations of the total body of observations of the Fomalhaut system, and find that the interpretation that best matches the available data for the observed source is scattered light from transient or semi-transient dust cloud.
Kalas has responded to the new study, saying that they considered the dust cloud possibility but ruled it out for various reasons. For one thing, Spitzer lacks the light sensitivity to detect a Saturn-sized planet, and bright rings could also explain the optical characteristics observed. He says, “We welcome the new Spitzer data, but we don’t really agree with this interpretation.”
The Princeton team, interestingly, thinks that there may be a real planet orbiting Fomalhaut, but still hiding from detection. From the paper:
In particular, we find that there is almost certainly no direct flux from a planet contributing to the visible-light signature. This, in combination with the existing body of data for the Fomalhaut system, strongly implies that the dynamically inferred giant planet companion and the visible-light point source are physically unrelated. This in turn implies that the ‘real’ Fomalhaut b still hides in the system. Although we do find a tentative point source in our images that could in principle correspond to this object, its significance is too low to distinguish whether it is real or not at this point.
A resolution to the debate may come from the James Webb Space Telescope, scheduled to launch in 2018.
Of course it will be disappointing if Fomalhaut b does turn out to not be a planet after all, but let’s not forget that thousands of other ones are being discovered and confirmed. There may occasionally be hits-and-misses, but so far the planetary hunt overall has been nothing short of a home run…
The paper is available here. | 0.833964 | 4.011767 |
SAN DIEGO (KGTV) — San Diego State University astronomers played a role in the recent discovery of a third planet within the Kepler-47 planetary system.
A team of researchers, led by astronomers from SDSU, discovered a new Neptune-size planet orbiting the system's two suns between two previously discovered planets.
The planet, named Kepler-47d, was discovered using a method called, "transit method," according to to university. The method measures a level of brightness to help detect masses.
"If the orbital plane of the planet is aligned edge-on as seen from Earth, the planet can pass in front of the host stars, leading to a measurable decrease in the observed brightness," a release from the school describes.
Previously, the planet's signal was too weak to detect.
“We saw a hint of a third planet back in 2012, but with only one transit we needed more data to be sure,” SDSU astronomer Jerome Orosz, the paper’s lead author, said in the release. “With an additional transit, the planet’s orbital period could be determined, and we were then able to uncover more transits that were hidden in the noise in the earlier data.”
Kepler-47d is about seven times the size of Earth and takes 87 days to orbit around its suns.
“We certainly didn’t expect it to be the largest planet in the system. This was almost shocking,” said William Welsh, SDSU astronomer and the study’s co-author.
The entire Kepler-47 system itself is interesting as well. With two suns, it's the only known multi-planet circumbinary system. The system is extremely compact and would fit inside the orbit of Earth. It's located about 3340 light-years away in the direction of constellation Cygnus. | 0.824258 | 3.295167 |
ann15085 — Kunngjøring
ESO Telescopes Observe Swift Satellite’s 1000th Gamma-ray Burst
6. november 2015
On 27 October 2015, at 22:40 GMT, the NASA/ASI/UKSA Swift satellite discovered its 1000th gamma-ray burst (GRB). This landmark event was subsequently observed and characterised by ESO telescopes at the La Silla Paranal Observatory in northern Chile, which revealed that this GRB was an especially interesting object.
Gamma-ray bursts are intense flashes of gamma radiation that occur randomly throughout the distant Universe. They are thought to be caused by an extremely energetic stellar explosion and believed to signal the birth of a new black hole.
Swift is dedicated to searching the skies for these mysterious and fascinating events and, after more than ten vigilant years, the satellite has now discovered its 1000th GRB. GRB 151027B occurred on 27 October 2015, in the direction of the constellation of Eridanus (The River) .
ESO telescopes have a long and successful tradition of performing follow-up observations of GRB events (eso0318 and eso0533), and they did not falter for this milestone. The Gamma-Ray Burst Optical/Near-Infrared Detector (GROND) mounted on the MPG/ESO 2.2-metre telescope at the La Silla Observatory and the X-shooter spectrograph on the Very Large Telescope (VLT) at ESO’s Paranal Observatory began observations as soon as the GRB became visible from Chile — around five hours after its detection .
By splitting the faint and rapidly fading light from GRBs up into their component colours the X-shooter spectrograph is one of the most powerful tools in existence for probing their nature. More than half of all distance measurements of GRBs since X-shooter started operations were made with this instrument.
The ESO observations revealed that the GRB 151027B explosion occurred when the Universe was just 1.5 billion years old (10% of its present age) and its light had travelled for 12.3 billion years before reaching the Earth. This result was announced just three hours after the data were taken and eight hours after the GRB was first detected by Swift. Further analysis also allowed astronomers to determine that the galaxy in which GRB 151027B occurred has an unusually high abundance of heavier chemical elements.
These intriguing conclusions from GRB 151027B demonstrate the success of the partnership between the Swift mission and ESO’s telescopes, which have provided critical follow-up observations for hundreds of gamma-ray bursts. The X-shooter and GROND instruments have been systematically observing these elusive events from the Atacama Desert since 2009 and 2007, respectively, providing valuable insights into the most powerful explosions in the Universe.
The X-shooter/GRB collaboration consists of: L.A. Antonelli (INAF/OA Roma), M. Arabsalmani (ESO), Z. Cano (Univ. Iceland), L. Christensen (DARK/NBI Copenhagen), S. Covino (INAF/OA Brera), A. De Cia (ESO), P. D'Avanzo (INAF/OA Brera), V. D'Elia (INAF/OA Roma and ASI/ASDC), F. Fiore (INAF/OA Roma), H. Flores (Paris Obs./GEPI), M. Friis (Univ. Iceland), J. P. U. Fynbo (DARK/NBI Copenhagen), P. Goldoni (APC/Irfu - CEA), A. Gomboc (Univ. Nova Gorica), P. Groot (Nijmegen), O. E. Hartoog (Amsterdam), F. Hammer (Paris Obs./GEPI), J. Hjorth (DARK/NBI Copenhagen), P. Jakobsson (Univ. Iceland), J. Japelj (INAF/OA Trieste), L. Kaper (API/Amsterdam), T. Krühler (MPE, Munich), C. Ledoux (ESO, Santiago), A. J. Levan (Univ. Warwick), G. Leloudas (Weizmann and DARK/NBI Copenhagen), E. Maiorano (INAF/IASF Bologna), D. Malesani (DARK/NBI Copenhagen), A. Melandri (INAF/OA Brera), B. Milvang-Jensen (DARK/NBI Copenhagen), P. Møller (ESO), E. Palazzi (INAF/IASF Bologna), D. A. Perley (DARK/NBI Copenhagen), E. Pian (SNS Pisa), S. Piranomonte (INAF/OA Roma), G. Pugliese (API/Amsterdam), R. Sánchez-Ramírez (IAA-CSIC, Granada), S. Savaglio (University of Calabria), P. Schady (MPE), J. Schaye (Leiden), S. Schulze (Pontificia Universidad Católica de Chile and MAS), J. Selsing (DARK/NBI Copenhagen), J. Sollerman (OKC Stockholm), M. Sparre (MPA, Heidelberg), G. Tagliaferri (INAF/OA Brera), N. R. Tanvir (Univ. Leicester), C. C. Thöne (IAA-CSIC, Granada), A. de Ugarte Postigo (IAA-CSIC Granada), S. D. Vergani (CNRS, Paris Obs./GEPI), P. M. Vreeswijk (WIS), D. J. Watson (DARK/NBI Copenhagen), K. Wiersema (Univ. Leicester), R. A. M. J. Wijers (API/Amsterdam) and D. Xu (NAOC, Beijing).
The GROND collaboration consists of: P. Afonso (American River College), J. Bolmer (MPE), C. Delvaux (MPE), J. Elliott (CfA), R. Filgas (Techn. Univ. Prague), J. Graham (MPE), J. Greiner (MPE), D.A. Kann (TLS Tautenburg), S. Klose (TLS Tautenburg), F. Knust (MPE), T. Krühler (MPE), A. Nicuesa Guelbenzu (TLS Tautenburg), P. Schady (MPE), S. Schmidl (TLS Tautenburg), T. Schweyer (MPE), M. Tanga (MPE), K. Varela (MPE) and P. Wiseman (MPE).
Dark Cosmology Centre
Niels Bohr Institute
Tel: +45 3532 5983
Max-Planck Institut für extraterrestrische Physik
Tel: +49 89 30000 3847
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591 | 0.86878 | 3.886064 |
In Quest of the Cosmic Origins of Silver
6 September 2012
Source: European Southern Observatory/ESO
In the quest for the cosmic origins of heavy elements, Heidelberg scientist Dr. Camilla Hansen has established that silver can only have materialised during the explosion of clearly defined types of star. These are different from the kind of stars producing gold when they explode. The evidence for this comes from the measurement of various high-mass stars with the help of which the stepwise evolution of the components of all matter can be reconstructed. The findings from the investigations conducted by Dr. Hansen of Heidelberg University’s Centre for Astronomy (ZAH) in conjunction with other scientists in Germany and fellow astronomers in Japan and Sweden have been published in the journal „Astronomy & Astrophysics”.
The lightweight elements hydrogen, helium and traces of lithium came into being a few minutes after the Big Bang. All heavier elements materialised later in the interior of stars or during star explosions, with each generation of stars contributing a little to enriching the universe with chemical elements. The elements a star can generate in its lifetime depend largely on its mass. At the end of their lives, stars about ten times the size of our sun explode as so-called supernovae, producing elements sometimes heavier than iron that are released by the explosion. Depending on how heavy the star originally was, silver and gold can also materialise in this way.
When various stars of the same mass explode, the ratio of elements generated and hurled out into the universe is identical. This constant relation is perpetuated in the subsequent generations of stars forming from the remnants of their predecessors. The investigations by Dr. Hansen and her associated scientists have now demonstrated that the amount of silver in the stars measured is completely independent of the amounts of other heavy elements like gold. These observations indicate clearly for the first time that during a supernova silver takes shape in an entirely different fusion process from that in which gold forms. Accordingly, the scientists contend that silver cannot have originated together with gold. The elements must have materialised from stars of different masses.
“This is the first incontrovertible evidence for a special fusion process taking place during the explosion of a star,” says Dr. Hansen. “Up to now this had been mere speculation. After this discovery, we must now use simulations of these processes in supernova explosions to investigate more precisely when the conditions for the formation of silver are present. That way we can find out how heavy the stars were that could produce silver during their dramatic demise.”
Note to news desks:
Digital pictures are available from the Press Office.
C.J. Hansen, F. Primas, H. Hartman, K.-L. Kratz. S. Wanajo, B. Leibundgut, K. Farouqi, O. Hallmann, N. Christlieb, H. Nilsson: Silver and palladium help unveil the nature of a second r-process. Astronomy & Astrophysics (September 2012), doi: 10.1051/0004-6361/201118643
Dr. Camilla Juul Hansen
Heidelberg University’s Centre for Astronomy (ZAH)
Phone +49 6221 54-1785
Communications and Marketing
Phone: +49 6221 542311 | 0.84586 | 3.855789 |
The Voyager missions were able to reach the outer planets because they used planet-sized gravity engines. The rocket that nudged them out of Earth’s gravity was a fraction of their power.
The only fuel these gravitational engines required was the initial angular momentum of the solar system left over from when it formed, so it was free and ready to use — Voyagers didn’t even have to bring it with them.
However the engines only work literally when the planets align — a Grand Tour of the solar system’s gas giants was possible only in 1977 and technology available to do it was only available for 1977.
I like the idea of learning via analogy, so, what can we use personally from the alignment of the planets and the Voyager missions?
It is rare to find and realize a preplanned, multistage trajectory of success
The more complex and amazing, the less likely. For the complex interactions that determine your personal life trajectory, these are rare and take much planning. Don’t expect them but never discount that planning ahead can lead to great things.
A Grand Idea can attract Grand Efforts
It takes many people working together to realize a single trajectory. This applies to spacecraft and personal success. Doing it alone is not realistic or best use of reality. The realization that the Grand Tour trajectory even existed was that of one graduate student, and 11,000 person years of effort were ultimately invested in building Voyagers and seeing them through the Tour. In a way the trajectory of serendipity and effort was as grand and unique as that defined by the solar system’s alignment.
Take advantage of the gravity wells and momentum in your environment
The real boost in your success comes not from your own engines but by heading where the opportunity is — follow the attractive forces and gain momentum from other’s momentum. While you are there, learn as much as you can.
Stick to something
Voyager missions are in their 40th year. The Grand Tour is their reason for existence, with long intervals of silence and steady preparation, grand moments of excitement and discovery — a story of stories
Voyagers were effectively many spacecraft coexisting in the same hull, ready to take over for one another, and in many cases this saved the mission. The math is this — with two redundant systems of 10% failure probability each, the total system can be 10 time more reliable than without redundancy. Have a backup plan if failure is not an option.
Voyagers were the first spacecraft with upgradable operating software. New tricks like data compression, workarounds for hardware failures were all used to rescue the mission from the unexpected. Stay flexible and open minded and grow beyond what you are now.
Have an audience
If Voyager had simply stored all its images and data on its internal tape, it would have been a failure. The goal was to learn and discover and share. An audience for efforts justify the effort and focus it — it keeps you coming back to the task when other motivations have faded.
Don’t overpromise, when you can overachieve
Voyagers were advertised as Jupiter-Saturn missions with an option for Uranus and Neptune encounters. Ever since then, JPL and other spacecraft mission designers have carefully divided efforts between what is the Mission and what is the Bonus. The mission is what you promise, the Bonus is what you strive for.
What you are doing can inspire as much as where you are going
The gold-anodized phonograph assembled by Drake, the Sagans and others and attached to the Voyagers contained examples of the best of humanity — photos, music, and greetings. It is one of the most well remembered outcomes of the mission, and was achieved before launch, and has a near-zero chance of mission success. What it did was show us how we would introduce ourselves as Human. The takeaway is that your efforts are really yours — other people might be capable of the same thing or greater, but why you did something is purely personal and what matters most.
More reading and resources
Book: The Interstellar Age by Jim Bell | 0.86875 | 3.470875 |
The Venus Twilight Experiment
Refraction and scattering phenomena during the transit of Venus on June 5-6, 2012
Planetary transits are a powerful method for discovering and characterizing exoplanets, but no transits can be seen in more details than those involving our own Solar System members, such as the transits of Venus and Mercury in front of the Sun.
|A. and S. Rondi - June 8, 2004 |
During and around Venus transits, in particular, interesting phenomena occurs, related to physical and chemical properties of its atmosphere. During ingress and egress a bright and thin luminous arc (the "aureole") is observable, appearing around the circumference of Venus disk which is partially outside the solar limb. This peculiar aspect of the planet has been observed for the first time in 1761 and then in all the subsequent transits, with varying intensity and aspect. Farther away from the Sun, the aureole - due to light refraction - disappears and Venus shines from the light diffused by droplets dispersed above its thick cloud deck.
We are establishing an international collaboration for deploying specialized instruments in the transit visibility area. We also realy upon the collaboration of observers that will use professional instruments at several sites. The multi-wavelength data will be interpreted thanks to a numerical model capable of reproducing the observations.
Our final aims are a better characterization of these twilight phenomena
and - in turn - an improved undestarding of the atmosphere of Venus, jointly with the observations obtained by Venus Express, the probe now orbiting the planet.
keywords: Venus transit 2012, Venus aureole, twilight phenomena, twilight experiment, Venus Express, Venus atmosphere, coronagraph, coronography, cytherograph, planetary transits | 0.830061 | 3.683673 |
Jupiter has been high overhead at sunset for several months, a brilliant light that's easy to spot even when the sky is still bright at dusk; but it's now moving quickly to the west as Earth speeds ahead of Jupiter's more stately march around the Sun.
Galileo, the scientist, discovered the Galilean satellites of Jupiter four hundred years ago next month, while Galileo, the mission, arrived at Jupiter to study those moons in situ fourteen years ago Sunday.
On Planetary Radio's "Questions and Answers" I answered this question: "I read that Uranus got its tilt when it was hit by another object. What does it mean for a ball of gas to be hit -- wouldn't another object just pass through it?"
As New Horizons continues its journey (it's now approaching the orbital distance of Saturn, though it's very far from that planet in space), the mission is taking advantage of the recent experience with the Jupiter flyby to plan out the science operations for the Pluto-Charon encounter.
A year after its launch on January 19, 2006, New Horizons is fast closing in on Jupiter, the first target on its near decade-long journey. On February 28 the spacecraft will approach to within 2.3 million kilometers (1.4 million miles) of Jupiter before speeding along on to its way to the edge of the solar system. | 0.876406 | 3.177113 |
AVAST gentle reader: mild SPOILER(S) and graphic depictions of shattered satellites ahead!
We recently had a chance to catch Oblivion, the first summer blockbuster of the season. The flick delivers on the fast-paced Sci-Fi action as Tom Cruise saves the planet from an invasion of Tom Cruise clones.
But the movie does pose an interesting astronomical question: what if the Earth had no large moon? In the movie, aliens destroy the Earth’s moon, presumably to throw our planet into chaos. You’d think we’d already be outclassed by the very definition of a species that could accomplish such a feat, but there you go.
Would the elimination of the Moon throw our planet into immediate chaos as depicted in the film? What if we never had a large moon in the first place? And what has our nearest natural neighbor in space done for us lately, anyway?
Earth is unique among rocky or terrestrial planets in that it has a relatively large moon. The Moon ranks 5th in diameter to other solar system satellites. It is 27% the diameter of our planet, but only just a little over 1/80th in terms of mass.
Clearly, the Moon has played a role in the evolution of life on Earth, although how necessary it was isn’t entirely clear. Periodic flooding via tides would have provided an initial impetus to natural selection, driving life to colonize the land. Many creatures such as sea turtles take advantage of the Full Moon as a signal to nest and breed, although life is certainly resilient enough to find alternative methods.
The 2000 book Rare Earth by Peter Ward and Donald Brownlee cites the presence of a large moon as just one of the key ingredients necessary in the story of the evolution of life on Earth. A Moon-less Earth is also just one of the alternative astronomical scenarios cited by Arthur Upgreen in his 2005 book Many Skies.
Contrary to its depiction on film, the loss of the Moon wouldn’t throw the Earth into immediate chaos, though the long term changes could be catastrophic. For example, no study has ever conclusively linked the Moon to the effective prediction of terrestrial volcanism and earthquakes, though many have tried. (Yes, we know about the 2003 Taiwanese study, which found a VERY weak statistical signal).
All of that angular momentum in the Earth-Moon system would still have to go somewhere. Our Moon is slowly “braking” the rotation of the Earth to the tune of about 1 second roughly every 67,000 years. We also know via bouncing laser beams off of retro-reflectors left by Apollo astronauts that the Moon is receding from us by about 3.8 cm a year. The fragments of the Moon would still retain its angular momentum, even partially shattered state as depicted in the film.
The most familiar effect the Moon has on Earth is its influence on oceanic tides. With the loss of our Moon, the Sun would become the dominant factor in producing tides, albeit a much weaker one.
But the biggest role the Moon plays is in the stabilization of the Earth’s spin axis over long scale periods of time.
Milankovitch cycles play a long term role in fluctuations in climate on the Earth. This is the result of changes in the eccentricity, obliquity and precession of the Earth’s axis and orbit. For example, perihelion, or our closest point to the Sun, currently falls in January in the middle of the northern hemisphere winter in the current epoch. The tilt of the Earth’s axis is the biggest driver of the seasons, and this varies from 22.1° to 24.5° and back (this is known as the change in obliquity) over a span of 41,000 years. We’re currently at a value of 23.4° and decreasing.
But without a large moon to dampen the change in obliquity, much wider and unpredictable swings would occur. For example, the rotational axis of Mars has varied over a span of 13 to 40 degrees over the last 10 to 20 million years. This long-term stability is a prime benefit that we enjoy in having a large moon .
Perhaps some astronomers would even welcome an alien invasion fleet intent on destroying the Moon. Its light polluting influence makes most deep sky imagers pack it in and visit the family on the week surrounding the Full Moon.
But I have but two words in defense of saving our natural satellite: No eclipses.
We currently occupy an envious position in time and space where total solar and lunar eclipses can occur. In fact, Earth is currently the only planet in our solar system from which you can see the Moon snugly fit in front of the Sun during a total lunar eclipse. It’s 1/400th the size of the Sun, which is also very close to 400 times as distant as the Moon. This situation is almost certainly a rarity in our galaxy; perhaps if alien invaders did show up, we could win ‘em over not by sending a nuclear-armed Tom Cruise after ‘em, but selling them on eclipse tours…
And a receding Moon also means that in approximately 1.4 billion years, the final total solar eclipse as seen from the Earth will occur. Conversely, the Moon was closer and appeared larger earlier in Earth’s history. About just under a billion years ago, the first brief annular eclipse similar to the one occurring next week on May 10th would have occurred. In the current epoch, annular eclipses constitute 33.2% of solar eclipses with total solar eclipses becoming ever rarer at 26.7%. (The remainder are hybrids and partials).
If the Moon was a necessary ingredient for life to take hold on Earth, then we may be a very rare occurrence in the universe indeed. The current theory for the formation of the Moon involves the Earth getting “wacked” by a Mars-sized body dubbed Theia early in its history. This would explain the relatively low density of our Moon compared to the Earth.
Oblivion isn’t the only science fiction to posit a moon-less Earth. Fans of 1970’s sci-fi will remember the TV series Space: 1999 which proposed an even more unlikely scenario of the Moon being “blown out of orbit” by a nuclear disaster. Of course, just how they managed to meet new alien civilizations every week was never explained, but hey, it was the 1970’s…
Oblivion did have one more glaring space science goof. Plutonium used for space travel and weaponized Plutonium are two different isotopes. It would not be possible (though it was a convenient plot device) to turn an nuclear-powered RTG such as one used on Mars to power the Curiosity rover into an explosive weapon.
But perhaps the greatest gift our Moon has to offer is its lessons to us as a species. The motion of the Moon provided early astronomers with a great lesson in Celestial Mechanics 101. Newton would have had a much tougher time deciphering the laws of motion and gravity were it not for the example provided by the Moon. Plus, it makes a great stepping stone for solar system exploration. Curse it or love it, the Moon is our celestial companion… let the sci-fi alien baddies be jealous! | 0.84883 | 3.183966 |
After researchers surveyed data from the Kepler mission tasked with identifying possibly habitable planets outside our solar system they found that 6% of red dwarfs – the most common type of planets – are within this zone. This new adjustment would mean that the nearest Earth-like planet might lie just 13 light years away.
Astronomers at the Harvard-Smithsonian Center for Astrophysics (CfA) first took a look at the entire Kepler catalog of 158,000 target stars to identify all the red dwarfs. Then a more refined method was used to assess the stars’ temperature and size, an analysis that showed that these were generally smaller and cooler than previously thought.
An exoplanet is discovered and has its properties determined based on its transient orbit in plane with its parent star. This implies that the exoplanet’s size and properties are the same time determined based on its host star, since they’re based relative to the star’s properties. Thus, cooler dwarf stars means cooler planets and a tighter habitable zone.
“We thought we would have to search vast distances to find an Earth-like planet. Now we realize another Earth is probably in our own backyard, waiting to be spotted,” said Harvard astronomer and lead author Courtney Dressing (CfA).
A new Earth might be closer to us than thought
Red dwarfs make up three out of every four stars in our galaxy for a total of at least 75 billion. The astronomers involved in the present study identified 95 planetary candidates orbiting such red dwarf stars. Upon closer inspection most of them didn’t fit the right size and temperature requirements needed for them to be considered Earth-like, though. Three candidate planets, however, were considered both warm and Earth-sized. This would statistically imply that some 6% of all red dwarfs should have an Earth-like planet orbiting.
“We now know the rate of occurrence of habitable planets around the most common stars in our galaxy,” said co-author David Charbonneau (CfA). “That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought.”
It so has it that our solar system is located in a cloud of red dwarfs, which is why more than 75% of all neighboring stars are red dwarfs. With this new analysis in play, this all adds up implying that the nearest Earth-like planet might lie just 13 light years away.
Actually locating an Earth-like planet, with all its perks, would require an analysis of its atmosphere, something not possible with today’s technology. Once with the deployment of massive space telescopes like the James Webb Space Telescope or ground based telescope arrays like the Giant Magellan Telescope probing a distant world’s chemistry will be possible – expect some of humanity’s greatest discoveries to be made once this happens.
The three habitable-zone planetary candidates identified in this study are Kepler Object of Interest (KOI) 1422.02, which is 90 percent the size of Earth in a 20-day orbit; KOI 2626.01, 1.4 times the size of Earth in a 38-day orbit; and KOI 854.01, 1.7 times the size of Earth in a 56-day orbit. All three are located about 300 to 600 light-years away and orbit stars with temperatures between 5,700 and 5,900 degrees Fahrenheit. (For comparison, our Sun’s surface is 10,000 degrees F.)
Dressing presented her findings today in a press conference at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass.
source: press release | 0.935564 | 3.948707 |
WINSTON-SALEM, N.C. -- Where there is smoke, there is fire. And when a galaxy smokes, supernovas are usually involved, or so astronomers thought.
But now, in a stunning picture that reveals a distant galaxy entangled in a vast web of dust clouds, astronomers are rethinking how galaxies "pollute" their surrounding halos, ejecting dark clouds thousands of light years in extent and collectively capable of enmeshing entire galaxies.
"It's a lot cloudier than we expected in to be," said Blair D. Savage, a University of Wisconsin-Madison astronomer who, with graduate student Christopher Howk, captured the image of the galaxy NGC 891 with the WIYN Telescope, a state-of-the-art telescope operated by a consortium of universities and the National Optical Astronomy Observatories (NOAO) atop Kitt Peak, Ariz. NOAO is an arm of the National Science Foundation (NSF).
Situated 30 million light years from Earth, NGC 891 is a spiral galaxy like the Milky Way, yet its orientation is such that from Earth its central plane can be viewed edge-on. Using the 3.5 meter WIYN Telescope, which has a wide field of view, the Wisconsin astronomers discovered a galaxy-enveloping network of dust clouds that seem to emanate from many regions of the galaxy disk.
"What we found," said Savage "was a highly polluted atmosphere of this galaxy. The hundreds of clouds are irregularly distributed and have a wide variety of shapes and extents" with some found as far as 5,000 light years above the galaxy's central disk.
The galactic dust clouds are composed mostly of hydrogen, helium and a very small, solid grain of carbon and silicate dust. Astronomers think the extensive clouds of dust that permeate the space between stars within galaxies is, literally, stardust, the ejected remains of stars that died long ago in peaceful and violent events known as supernovas.
It was long believed -- and it may still be the case -- that supernova events, heating galactic space to temperatures of a million degrees or more, propelled some dust in chimney-like fashion up into the outer reaches or halos of galaxies. But finding a massive network of dust clouds in the halo of the galaxy was a surprise, said Savage, because it was believed the fragile interstellar dust grains would be consumed by the hot gases produced in violent supernova explosions.
The discovery of networks of clouds interwoven throughout the galactic halo of NGC 891 suggests that the picture is more complicated, or that other, gentler kinds of processes may be at work, said Howk.
"If the ejection process was just supernova-driven, we might expect to see just a few galactic chimneys" where dust in hot, over-pressurized regions is funneled up from the plane of the galaxy, Howk said. In fact, in some places the dust clouds appear isolated, while in other places they connect with active regions of the galaxy in chimney- like structures.
One possible explanation for the widespread distribution of the dust clouds, said Savage, is that the dust is also carried high into the halo by the gentle pressure of starlight. A similar process involving the pressure of sunlight produces the beautiful tails of dust observed to extend from comets as they orbit the sun.
The existence of the clouds in the halo of NGC 891, at the least, provides astronomers with a completely new way of studying the flow of matter from the disks into the halos of spiral galaxies, said Savage.
The telescope used to make the discovery, known as WIYN, is one of a new generation of ground-based telescopes making important fundamental contributions to understanding space and the objects that populate it. WIYN is operated by a consortium of universities including the University of Wisconsin-Madison, Indiana and Yale Universities, and the National Optical Astronomical Observatories, an arm of the National Science Foundation charged with managing and operating the suite of telescopes situated on Kitt Peak.
Contact: Blair D. Savage
Or: Christopher Howk
Editor's note: Images of the NGC 891 galaxy are posted at | 0.849721 | 4.022489 |
Astronomers have located an object in space that’s over nine billion miles from the sun, putting it three times farther away than Pluto — that’s 103 times farther from the Sun than Earth — making it the most distant body yet to be discovered in our solar system.
Designated V774104, it’s a dwarf planet about 300-600 miles in size. The object’s orbit is yet to be determined, and due to its distance from the sun it could potentially be a part of the Oort Cloud.
The Oort Cloud, a hypothetical sphere of comets and other icy bodies located a full light-year from the sun, is believed to represent the end of the sun’s gravitational influence. Objects within the Oort Cloud have eccentric orbits that cannot be definitively explained by the known structure of the solar system.
If V774104 ends up proven to orbit inward closer to the sun, it could be classified with objects whose paths are explained by gravitational interaction with Neptune (Trans-Neptunian Objects), like Pluto, in the Kuiper Belt — a debris field that stretches from the orbit of Neptune out to about 4.6 billion miles from the Sun. On the other hand, if it never comes closer, it would end up in a class with objects like Sedna.
Sedna, at almost eight billion miles from the Sun, is too distant to be affected by the gravity of Neptune. However, it’s still close enough to the sun to possibly not be a part of the Oort Cloud. In this case, V774104 would join Sedna as a potential “inner Oort Cloud object.”
V774104 replaces Eris, a Trans-Neptunian dwarf planet with a moon (Dysnomia) that orbits the Sun, as the known most distant object of the solar system. | 0.86779 | 3.634362 |
In 2013, the Cherenkov Telescope Array (CTA) was established with the intention of building the world’s largest and most sensitive high-energy gamma ray observatory. Consisting of over 1350 scientists from 210 research institutes in 32 countries, this observatory will use 100 telescopes across the northern and southern hemispheres to explore the high-energy Universe.
Key to their efforts is a prototype dual-mirror Schwarzschild-Couder telescope, known as the Astrofisica con Specchi a Tecnologia Replicante Italiana (ASTRI). Since it was first created in 2014, this prototype has been undergoing tests at the Serra La Nave Observing Station on Mount Etna, Sicily. And as of October of 2016, it passed its most important test to date, demonstrating a constant point-spread function across its full field of view.
The ASTRI telescope is essentially a revolutionary kind of Imaging Atmospheric Cherenkov Telescope (IACT). These ground-based telescopes are used by astronomers to detect cosmic high-energy gamma rays. These rays are produced by the most energetic objects in the universe (i.e. pulsars, supernovae, regions around black holes), and are only detectable because of the Cherenkov Effect, which they undergo once they pass into our atmosphere.
This effect occurs when particles of light achieve speeds greater than the phase velocity of light in their particular medium. In this case, the effect is produced when light particles pass from the vacuum of space into our atmosphere, temporarily exceeding the speed of light in air and producing a glow in the blue to UV range. In the case of very-high-energy gamma rays, indirect observations of this Cherenkov radiation is the only way to detect them.
Typically, Cherenkov telescopes use a mirror to collect light and focus it on a camera. The ASTRI telescope is something quite different, in that it is based on the Schwarzschild-Couder model. As Giovanni Pareschi, an astronomer at the INAF-Brera Astronomical Observatory and the principal investigator of the ASTRI project, told Universe Today via email:
“The ASTRI telescope for the first time is based on a two mirror imaging configuration (while in general Cherenkov telescopes work with in single mirror configuration, i.e. just a big primary mirror with the camera put in the Newtonian focus and a f-number close to 1). ASTRI is a prototype of the telescopes of the Small Size Telescope sub-array of the CTA Observatory. The sub-array is devoted to detect the gamma rays with the highest energy (up to 100 Tev). In order to properly work, the sub-array has to be based on a large number of telescopes (70 units) with a distance from each other of a 250 m distributed and with a large field (10 deg x 10 deg) of view with a constant angular resolution of a few arc minutes across the field of view.
This idea for such a telescope was first proposed in 1905 by German astronomer Karl Schwarzschild, but remained dormant for almost a century since it was deemed too difficult and too expensive to construct. It was not until 2007 that it was considered as a viable means for creating a new type of IACT. And in 2014, the INAF-Brera Astronomical Observatory commissioned the first of its kind to be built.
“[W]e have for the first time adopted a two reflection design based on the Schwarzschild-Couder configuration never realized before (also for telescopes operating in the visible band),” added Pareschi. “This configuration allows us to optimize the angular resolution across the field of view and to use focal plane cameras of small dimensions (thanks to this property, we could use new solid-state technology based Silicon photomultiplier sensors instead of the “old” classical photomultiplier tubes used so far in Cherenkov astronomy).”
These advantages, and the advances they allow for, will make ASTRI telescope approximately ten times more sensitive than current instruments. And with this latest test – which demonstrating a constant point-spread function of a few arc minutes over a large field of view of 10 degrees – the team behind it now has proof that it will work. As Pareschi explained:
“The test demonstrated for the first time that a telescope based on the Schwarzschild-Couder configuration correctly works and that a two-mirror configuration can be adopted for making Cherenkov telescopes for gamma ray astronomy. In addition, the ASTRI prototype has been completely characterized and validated from the opto-mechanical point of view, demonstrating that we can now proceed with the construction of the Small-Sized Telescopes (SSTs) of the array based on the ASTRI design.”
With this important test complete, the INAF-Brera team hopes to spend the next few months prepping the telescope. This will include mounting the Cherenkov camera onto the prototype and testing its gamma-ray performance. Then they will start to produce the first set of ASTRI telescopes to create a mini-array, which will serve as a precursor to the planned CTA sub-array that is scheduled to be built in Chile.
Once the camera is tested and mounted, the ASTRI team will conduct their first observations of gamma-rays at very high energies. These observations will allow scientists to determine the direction of gamma-ray photons that are the result of celestial sources, such as neutron stars, pulsars, supernovae, and black holes, tracing them back to their respective sources.
And with the planned construction of 100 SSTs to be spread out over the northern and southern hemispheres, the CTA array will outnumber all other telescopes in the world. The wide coverage and large number of these telescopes, spread over a wide area, will improve astronomers chances of detecting very high-energy gamma rays as they pass into our atmosphere.
Further Reading: CTA
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Kolkata, April 22 (IANS) Thrilled at the detection of the elusive gravitational waves a century after Albert Einstein’s prediction and the first observation of collision of two black holes at the Interferometer Gravitational-wave Observatory (LIGO), two young US-based Indian researchers working on the project say the waves act as a sixth sense for humans to comprehend the universe.
In fact, these “ripples in the curvature of space and time” will provide information on the cosmos that wouldn’t have been possible by peering through any kind of telescope, say Karan P. Jani and Nancy Aggarwal, who are elated at the prospect of India getting a third LIGO (observatory) and being at the forefront of new-age astrophysics.
Last month, India and the US signed an agreement for a new LIGO project in India during Prime Minister Narendra Modi’s visit to Washington. The agreement was signed between India’s Department of Atomic Energy and the US’ National Science Foundation (NSF).
The prime minister also met Indian student scientists, including Aggarwal and Jani, associated with the LIGO project.
“Gravitational waves are a completely new way of seeing the universe. It’s like humans can now perceive the sixth sense beyond the five, to comprehend the universe,” Jani, a fourth year PhD researcher in astrophysics at the Georgia Institute of Technology, told IANS via email.
The gravitational waves were detected on September 14, 2015, by both of the twin LIGO detectors, located in Livingston, Louisiana, and Hanford, Washington. The LIGO Observatories are funded by the NSF and were conceived, built, and are operated by Caltech and the Massachusetts Institute of Technology (MIT).
Physicists have concluded that the detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.
Jani and Aggarwal explained the detectors led to “direct observation of existence of black holes as also a direct observation of mergers of two black holes into a bigger black hole.”
“The energy released during collision was 50 times more than all the stars in the universe combined at that instance,” added Jani, whose work involves simulating black holes on supercomputers and searching for massive black hole collisions in LIGO data.
The breakthrough was made by the LIGO Scientific Collaboration (LSC) (which includes the GEO Collaboration and the Australian Consortium for Interferometric Gravitational Astronomy) and the Virgo Collaboration using data from the two LIGO detectors.
The LSC currently includes over 1,000 members from 90 institutes and 16 countries. India is the third highest right now in terms of membership.
At the heart of the mammoth hunting game to catch the unicorn are tools called interferometers which work by merging two or more sources of light to create an interference pattern that can be measured and analyzed.
“It is a four km light interferometer… in fact LIGO is the most precise measurement ever done. This means a lot of technology research has to be done to make LIGO,” Aggarwal, a fourth year Ph D student at MIT LIGO Lab, told IANS via email.
Aggarwal is studying quantum mechanics to improve the precision of gravitational wave detectors and is glad that the starting of the LIGO India project opens up a new opportunity for her to work in her native country.
“A lot of technological developments that were made for LIGO have found independent applications in science as well as industry and LIGO India will create a lot of opportunities for Indian scientists and engineers and improve the general scientific and technological environment,” Aggarwal emphasised.
They hope to “share the discovery with a larger audience”, a request put in by Modi during their meeting.
“During our meeting, the prime minister said he would like the LIGO scientists to make frequent India trips to popularize the science in colleges in India. We also talked about physics outreach in India for school children, the importance of hands-on demos and the importance of learning material in languages other than English,” Aggarwal informed.
“Also, due to the participation, the travelling of Indian scientists abroad and international scientists to India will definitely strengthen the international relations for India,” she said. | 0.835851 | 3.711855 |
A supernova remnant is the structure resulting from the explosion of a star in a supernova. The supernova remnant is bounded by an expanding shock wave, consists of ejected material expanding from the explosion, the interstellar material it sweeps up and shocks along the way. There are two common routes to a supernova: either a massive star may run out of fuel, ceasing to generate fusion energy in its core, collapsing inward under the force of its own gravity to form a neutron star or a black hole. In either case, the resulting supernova explosion expels much or all of the stellar material with velocities as much as 10% the speed of light; these speeds are supersonic, so a strong shock wave forms ahead of the ejecta. That heats the upstream plasma up to temperatures well above millions of K; the shock continuously slows down over time as it sweeps up the ambient medium, but it can expand over hundreds or thousands of years and over tens of parsecs before its speed falls below the local sound speed.
One of the best observed young supernova remnants was formed by SN 1987A, a supernova in the Large Magellanic Cloud, observed in February 1987. Other well-known supernova remnants include the Crab Nebula; the youngest known remnant in our galaxy is G1.9+0.3, discovered in the galactic center. An SNR passes through the following stages as it expands: Free expansion of the ejecta, until they sweep up their own weight in circumstellar or interstellar medium; this can last tens to a few hundred years depending on the density of the surrounding gas. Sweeping up of a shell of shocked circumstellar and interstellar gas; this begins the Sedov-Taylor phase. Strong X-ray emission traces the strong shock waves and hot shocked gas. Cooling of the shell, to form a thin, dense shell surrounding the hot interior; this is the pressure-driven snowplow phase. The shell can be seen in optical emission from recombining ionized hydrogen and ionized oxygen atoms. Cooling of the interior; the dense shell continues to expand from its own momentum.
This stage is best seen in the radio emission from neutral hydrogen atoms. Merging with the surrounding interstellar medium; when the supernova remnant slows to the speed of the random velocities in the surrounding medium, after 30,000 years, it will merge into the general turbulent flow, contributing its remaining kinetic energy to the turbulence. There are three types of supernova remnant: Shell-like, such as Cassiopeia A Composite, in which a shell contains a central pulsar wind nebula, such as G11.2-0.3 or G21.5-0.9. Mixed-morphology remnants, in which central thermal X-ray emission is seen, enclosed by a radio shell; the thermal X-rays are from swept-up interstellar material, rather than supernova ejecta. Examples of this class include the SNRs W28 and W44. Remnants which could only be created by higher ejection energies than a standard supernova are called hypernova remnants, after the high-energy hypernova explosion, assumed to have created them. Supernova remnants are considered the major source of galactic cosmic rays.
The connection between cosmic rays and supernovas was first suggested by Walter Baade and Fritz Zwicky in 1934. Vitaly Ginzburg and Sergei Syrovatskii in 1964 remarked that if the efficiency of cosmic ray acceleration in supernova remnants is about 10 percent, the cosmic ray losses of the Milky Way are compensated; this hypothesis is supported by a specific mechanism called "shock wave acceleration" based on Enrico Fermi's ideas, still under development. Indeed, Enrico Fermi proposed in 1949 a model for the acceleration of cosmic rays through particle collisions with magnetic clouds in the interstellar medium; this process, known as the "Second Order Fermi Mechanism", increases particle energy during head-on collisions, resulting in a steady gain in energy. A model to produce Fermi Acceleration was generated by a powerful shock front moving through space. Particles that cross the front of the shock can gain significant increases in energy; this became known as the "First Order Fermi Mechanism".
Supernova remnants can provide the energetic shock fronts required to generate ultra-high energy cosmic rays. Observation of the SN 1006 remnant in the X-ray has shown synchrotron emission consistent with it being a source of cosmic rays. However, for energies higher than about 1018 eV a different mechanism is required as supernova remnants cannot provide sufficient energy, it is still unclear. The future telescope CTA will help to answer this question. List of All Known Galactic and Extragalactic Supernovae on the Open Supernova Catalog Galactic SNR Catalogue Chandra observations of supernova remnants: catalog, photo album, selected picks 2MASS images of Supernova Remnants NASA: Introduction to Supernova Remnants NASA's Imagine: Supernova Remnants Afterlife of a Supernova on UniverseToday.com Supernova remnant on arxiv.org Supernova Remnants, SEDS
Daniel B. Short is an American politician, he is a Republican member of the Delaware House of Representatives, representing District 39. He was elected in 2006 to replace retiring Republican Tina Fallon in the House, after having lost a race for the Delaware Senate in the previous election, he has served as the House Minority Leader since January 2013, was the minority whip. He served as a city council member and mayor of Seaford, Delaware, he earned an associate degree from the University of Delaware. In 2004, Short challenged incumbent Democrat Robert Venables Sr. for a seat in the Delaware Senate but lost the general election. In 2006, Short ran for a seat in the Delaware House and won the general election with 3,370 votes against Democratic nominee Richard Sternberg. In 2008, Short won the general election with 5,185 votes against Democratic nominee Jerry Semper, who had qualified and received votes as the Working Families Party candidate. In 2010, Short was unopposed for the general election.
In 2012, Short won the Republican primary with 1,046 votes, was unopposed for the general election, winning 6,191 votes. In 2014, Short won the general election with 3,977 votes against Libertarian nominee James W. Brittingham. In 2016, Short won the general election with 6,643 votes in a rematch against Libertarian nominee James W. Brittingham. In 2018, Short was unopposed in the general election. Official page at the Delaware General Assembly Campaign site Profile at Vote Smart
Robert Henderson is a Canadian politician, elected to the Legislative Assembly of Prince Edward Island in the 2007 provincial election. He is a member of the Liberal Party, he is the son of former MP George Henderson. In October 2011, Henderson was appointed to the Executive Council of Prince Edward Island as Minister of Tourism and Culture. Henderson continued to serve as Minister of Tourism when Wade MacLauchlan took over as premier in February 2015, but was left out when MacLauchlan shuffled the cabinet following the 2015 election. On January 7, 2016, Henderson returned to cabinet as Minister of Wellness. On January 10, 2018, Henderson was moved to Minister of Fisheries. Robert Henderson | 0.81975 | 4.166223 |
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Bode’s law, also called Titius-Bode law, empirical rule giving the approximate distances of planets from the Sun. It was first announced in 1766 by the German astronomer Johann Daniel Titius but was popularized only from 1772 by his countryman Johann Elert Bode. Once suspected to have some significance regarding the formation of the solar system, Bode’s law is now generally regarded as a numerological curiosity with no known justification.
One way to state Bode’s law begins with the sequence 0, 3, 6, 12, 24,…, in which each number after 3 is twice the previous one. To each number is added 4, and each result is divided by 10. Of the first seven answers—0.4, 0.7, 1.0, 1.6, 2.8, 5.2, 10.0—six of them (2.8 being the exception) closely approximate the distances from the Sun, expressed in astronomical units (AU; the mean Sun-Earth distance), of the six planets known when Titius devised the rule: Mercury, Venus, Earth, Mars, Jupiter, and Saturn. At about 2.8 AU from the Sun, between Mars and Jupiter, the asteroids were later discovered, beginning with Ceres in 1801. The rule also was found to hold for the seventh planet, Uranus (discovered 1781), which lies at about 19 AU, but it failed to predict accurately the distance of the eighth planet, Neptune (1846), and that of Pluto, which was regarded as the ninth planet when it was discovered (1930). For a discussion of the roles that Bode’s law played in early asteroid discoveries and the search for planets in the outer solar system, see the articles asteroid and Neptune.
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physical science: New discoveriesThe sequence, called Bode’s law (or the Titius-Bode law), is given by 0 + 4 = 4, 3 + 4 = 7, 3 × 2 + 4 = 10, 3 × 4 + 4 = 16, and so on, yielding additional values of 28, 52, and 100. If…
astronomy: Herschel and the new planet…at distance 192 (where the Titius-Bode sequence predicted 196) seemed an uncanny confirmation of the law.…
astronomy: Precise calculations and observations…the rough validity of the Titius-Bode law to make their calculations easier. Adams predicted a place in the zodiac where astronomers should look, but at first he could not get the English astronomical community to tackle the job. Le Verrier had better luck, for his prediction was taken up immediately… | 0.879317 | 3.613261 |
It was a bright speck in the night. On April 27, something caught the eyes of astronomers poring through data gathered by the Pan-STARRS Observatory in Hawaii: a previously unknown space rock, and one that was very, very close to Earth.
Coincidentally, the alert came as a rather large asteroid (called 1998 OR2) was making its closest approach to Earth. That space rock, which was discovered decades ago, is about 2.5 miles (4 kilometers) wide. On April 28, it flew by Earth at a range of about 3.9 million miles (6.3 million km), about 16 times the distance from Earth to the moon. That distance is pretty bland for Earth flybys; it was the asteroid's size that made the event intriguing.
The Pan-STARRS observation, it turned out, represented the opposite combination of characteristics: a small asteroid and a close shave of a flyby. The initial sighting sent planetary defense experts around the world into a flurry of activity because the first hour of observations suggested the space rock, now dubbed 2020 HS7, had a 10% chance of colliding with Earth.
Within an hour, other observatories around the world were also on the case, tracking the object. And as scientists gathered more measurements, their concerns dissipated: the object was going to pass safely by Earth. These observations also showed that the object was just 13 to 26 feet (4 to 8 meters) wide, suggesting that even if it had collided with Earth, it would simply burn up in the planet's thick atmosphere.
"Small asteroids like 2020 HS7 safely pass by Earth a few times per month," NASA's Planetary Defense Officer Lindley Johnson said in a statement released on April 28. "It poses no threat to our planet, and even if it were on a collision path with Earth it is small enough that it would be disintegrated by our Earth's atmosphere."
Still, it was an impressively close flyby: According to the European Space Agency (ESA), 2020 HS7 passed by 26,550 miles (42,735 km) away from the center of the Earth and just 750 miles (1,200 km) from the nearest satellite in geostationary orbit, one of the more distant rings of satellites surrounding Earth. The space rock passed below the satellite and left it undamaged.
According to ESA, the flyby is one of the 50 closest on record, making it rather more interesting to scientists than the much-publicized (and more distant) flyby of the larger rock 1998 OR2 the same week.
Both flybys show the way planetary defense systems are designed to work: First, identify as many asteroids as possible, starting with the largest. Then, track them long enough to plot their orbits. The more data scientists can gather, the more accurate those orbits become, hence the downgrade from 10% chance of impact to a safe miss.
If more observations instead show the impact probability increasing, alert systems are enacted to prepare areas at risk and evaluate potential mitigation approaches — but those systems weren't necessary for 2020 HS7.
- It's time to get serious about asteroid threats, NASA chief says
- What if an asteroid was going to hit Earth? NASA will make believe this week
- NASA wants a new space telescope to protect us all from dangerous asteroids | 0.876498 | 3.765834 |
Permian–Triassic extinction event
The Permian–Triassic (P–Tr) extinction event, colloquially known as the Great Dying, the End Permian or the Great Permian Extinction, occurred about 252 Ma (million years) ago, forming the boundary between the Permian and Triassic geologic periods, as well as the Paleozoic and Mesozoic eras. It is the Earth's most severe known extinction event, with up to 96% of all marine species and 70% of terrestrial vertebrate species becoming extinct. It is the only known mass extinction of insects. Some 57% of all families and 83% of all genera became extinct. Because so much biodiversity was lost, the recovery of life on Earth took significantly longer than after any other extinction event, possibly up to 10 million years.
There is evidence for one to three distinct pulses, or phases, of extinction. Suggested mechanisms for the latter include one or more large bolide impact events, massive volcanism, coal or gas fires and explosions from the Siberian Traps, and a runaway greenhouse effect triggered by sudden release of methane from the sea floor due to methane clathrate dissociation or methane-producing microbes known as methanogens; possible contributing gradual changes include sea-level change, increasing anoxia, increasing aridity, and a shift in ocean circulation driven by climate change.
Dating the extinction
Until 2000, it was thought that rock sequences spanning the Permian–Triassic boundary were too few and contained too many gaps for scientists to reliably determine its details.
However, it is now possible to date the extinction with remarkable precision. U-Pb zircon dates from five volcanic ash beds from the Global Stratotype Section and Point for the Permian-Triassic boundary at Meishan, China, establish a high-resolution age model for the extinction – allowing exploration of the links between global environmental perturbation, carbon cycle disruption, mass extinction, and recovery at millennial timescales. The extinction occurred between 251.941 ± 0.037 and 251.880 ± 0.031 Ma, a duration of 60 ± 48 ka. A large (approximately 0.9%), abrupt global decrease in the ratio of the stable isotope 13
C to that of 12
C, coincides with this extinction, and is sometimes used to identify the Permian–Triassic boundary in rocks that are unsuitable for radiometric dating. Further evidence for environmental change around the P–Tr boundary suggests an 8 °C (14 °F) rise in temperature, and an increase in CO
2 levels by ppm (by contrast, the concentration immediately before the industrial revolution was 2000 ppm.) 280 There is also evidence of increased ultraviolet radiation reaching the earth, causing the mutation of plant spores.
It has been suggested that the Permian–Triassic boundary is associated with a sharp increase in the abundance of marine and terrestrial fungi, caused by the sharp increase in the amount of dead plants and animals fed upon by the fungi. For a while this "fungal spike" was used by some paleontologists to identify the Permian–Triassic boundary in rocks that are unsuitable for radiometric dating or lack suitable index fossils, but even the proposers of the fungal spike hypothesis pointed out that "fungal spikes" may have been a repeating phenomenon created by the post-extinction ecosystem in the earliest Triassic. The very idea of a fungal spike has been criticized on several grounds, including: Reduviasporonites, the most common supposed fungal spore, was actually a fossilized alga; the spike did not appear worldwide; and in many places it did not fall on the Permian–Triassic boundary. The algae, which were misidentified as fungal spores, may even represent a transition to a lake-dominated Triassic world rather than an earliest Triassic zone of death and decay in some terrestrial fossil beds. Newer chemical evidence agrees better with a fungal origin for Reduviasporonites, diluting these critiques.
Uncertainty exists regarding the duration of the overall extinction and about the timing and duration of various groups' extinctions within the greater process. Some evidence suggests that there were multiple extinction pulses or that the extinction was spread out over a few million years, with a sharp peak in the last million years of the Permian. Statistical analyses of some highly fossiliferous strata in Meishan, Zhejiang Province in southeastern China, suggest that the main extinction was clustered around one peak. Recent research shows that different groups became extinct at different times; for example, while difficult to date absolutely, ostracod and brachiopod extinctions were separated by 670 to 1170 thousand years. In a well-preserved sequence in east Greenland, the decline of animals is concentrated in a period 10 to thousand years long, with plants taking several hundred thousand additional years to show the full impact of the event. 60 An older theory, still supported in some recent papers, is that there were two major extinction pulses 9.4 million years apart, separated by a period of extinctions well above the background level, and that the final extinction killed off only about 80% of marine species alive at that time while the other losses occurred during the first pulse or the interval between pulses. According to this theory one of these extinction pulses occurred at the end of the Guadalupian epoch of the Permian. For example, all but one of the surviving dinocephalian genera died out at the end of the Guadalupian, as did the Verbeekinidae, a family of large-size fusuline foraminifera. The impact of the end-Guadalupian extinction on marine organisms appears to have varied between locations and between taxonomic groups—brachiopods and corals had severe losses.
|Marine extinctions||Genera extinct||Notes|
|Eurypterids||100%||May have become extinct shortly before the P–Tr boundary|
|Trilobites||100%||In decline since the Devonian; only 2 genera living before the extinction|
|Brachiopods||96%||Orthids and productids died out|
|Bryozoans||79%||Fenestrates, trepostomes, and cryptostomes died out|
|Acanthodians||100%||In decline since the Devonian, with only one living family|
|Anthozoans||96%||Tabulate and rugose corals died out|
|Blastoids||100%||May have become extinct shortly before the P–Tr boundary|
|Crinoids||98%||Inadunates and camerates died out|
|Foraminiferans||97%||Fusulinids died out, but were almost extinct before the catastrophe|
Marine invertebrates suffered the greatest losses during the P–Tr extinction. Evidence of this was found in samples from south China sections at the P–Tr boundary. Here, 286 out of 329 marine invertebrate genera disappear within the final 2 sedimentary zones containing conodonts from the Permian. The decrease in diversity was probably caused by a sharp increase in extinctions, rather than a decrease in speciation.
The extinction primarily affected organisms with calcium carbonate skeletons, especially those reliant on stable CO2 levels to produce their skeletons. These organisms were susceptible to the effects of the ocean acidification that resulted from increased atmospheric CO2.
Among benthic organisms, the extinction event multiplied background extinction rates, and therefore caused most damage to taxa that had a high background extinction rate (by implication, taxa with a high turnover). The extinction rate of marine organisms was catastrophic.
Surviving marine invertebrate groups include: articulate brachiopods (those with a hinge), which have suffered a slow decline in numbers since the P–Tr extinction; the Ceratitida order of ammonites; and crinoids ("sea lilies"), which very nearly became extinct but later became abundant and diverse.
The groups with the highest survival rates generally had active control of circulation, elaborate gas exchange mechanisms, and light calcification; more heavily calcified organisms with simpler breathing apparatus were the worst hit. In the case of the brachiopods at least, surviving taxa were generally small, rare members of a diverse community.
The ammonoids, which had been in a long-term decline for the 30 million years since the Roadian (middle Permian), suffered a selective extinction pulse 10 million years before the main event, at the end of the Capitanian stage. In this preliminary extinction, which greatly reduced disparity, that is the range of different ecological guilds, environmental factors were apparently responsible. Diversity and disparity fell further until the P–Tr boundary; the extinction here was non-selective, consistent with a catastrophic initiator. During the Triassic, diversity rose rapidly, but disparity remained low.
The range of morphospace occupied by the ammonoids, that is the range of possible forms, shape or structure, became more restricted as the Permian progressed. Just a few million years into the Triassic, the original range of ammonoid structures was once again reoccupied, but the parameters were now shared differently among clades.
The Permian had great diversity in insect and other invertebrate species, including the largest insects ever to have existed. The end-Permian is the only known mass extinction of insects, with eight or nine insect orders becoming extinct and ten more greatly reduced in diversity. Palaeodictyopteroids (insects with piercing and sucking mouthparts) began to decline during the mid-Permian; these extinctions have been linked to a change in flora. The greatest decline occurred in the Late Permian and was probably not directly caused by weather-related floral transitions.
Most fossil insect groups found after the Permian–Triassic boundary differ significantly from those that lived prior to the P–Tr extinction. With the exception of the Glosselytrodea, Miomoptera, and Protorthoptera, Paleozoic insect groups have not been discovered in deposits dating to after the P–Tr boundary. The caloneurodeans, monurans, paleodictyopteroids, protelytropterans, and protodonates became extinct by the end of the Permian. In well-documented Late Triassic deposits, fossils overwhelmingly consist of modern fossil insect groups.
Plant ecosystem response
The geological record of terrestrial plants is sparse and based mostly on pollen and spore studies. Interestingly, plants are relatively immune to mass extinction, with the impact of all the major mass extinctions "insignificant" at a family level. Even the reduction observed in species diversity (of 50%) may be mostly due to taphonomic processes. However, a massive rearrangement of ecosystems does occur, with plant abundances and distributions changing profoundly and all the forests virtually disappearing; the Palaeozoic flora scarcely survived this extinction.
At the P–Tr boundary, the dominant floral groups changed, with many groups of land plants entering abrupt decline, such as Cordaites (gymnosperms) and Glossopteris (seed ferns). Dominant gymnosperm genera were replaced post-boundary by lycophytes—extant lycophytes are recolonizers of disturbed areas.
Palynological or pollen studies from East Greenland of sedimentary rock strata laid down during the extinction period indicate dense gymnosperm woodlands before the event. At the same time that marine invertebrate macrofauna declined, these large woodlands died out and were followed by a rise in diversity of smaller herbaceous plants including Lycopodiophyta, both Selaginellales and Isoetales. Later, other groups of gymnosperms again become dominant but again suffered major die offs. These cyclical flora shifts occurred a few times over the course of the extinction period and afterwards. These fluctuations of the dominant flora between woody and herbaceous taxa indicate chronic environmental stress resulting in a loss of most large woodland plant species. The successions and extinctions of plant communities do not coincide with the shift in δ13C values, but occurred many years after. The recovery of gymnosperm forests took 4–5 million years.
No coal deposits are known from the Early Triassic, and those in the Middle Triassic are thin and low-grade. This "coal gap" has been explained in many ways. It has been suggested that new, more aggressive fungi, insects and vertebrates evolved, and killed vast numbers of trees. These decomposers themselves suffered heavy losses of species during the extinction, and are not considered a likely cause of the coal gap. It could simply be that all coal forming plants were rendered extinct by the P–Tr extinction, and that it took 10 million years for a new suite of plants to adapt to the moist, acid conditions of peat bogs. On the other hand, abiotic factors (not caused by organisms), such as decreased rainfall or increased input of clastic sediments, may also be to blame. Finally, it is also true that there are very few sediments of any type known from the Early Triassic, and the lack of coal may simply reflect this scarcity. This opens the possibility that coal-producing ecosystems may have responded to the changed conditions by relocating, perhaps to areas where we have no sedimentary record for the Early Triassic. For example, in eastern Australia a cold climate had been the norm for a long period of time, with a peat mire ecosystem adapted to these conditions. Approximately 95% of these peat-producing plants went locally extinct at the P–Tr boundary; Interestingly, coal deposits in Australia and Antarctica disappear significantly before the P–Tr boundary.
There is enough evidence to indicate that over two-thirds of terrestrial labyrinthodont amphibians, sauropsid ("reptile") and therapsid ("proto-mammal") families became extinct. Large herbivores suffered the heaviest losses.
All Permian anapsid reptiles died out except the procolophonids (although testudines have morphologically anapsid skulls, they are now thought to have separately evolved from diapsid ancestors). Pelycosaurs died out before the end of the Permian. Too few Permian diapsid fossils have been found to support any conclusion about the effect of the Permian extinction on diapsids (the "reptile" group from which lizards, snakes, crocodilians, and dinosaurs [including birds] evolved).
Even the groups that survived suffered extremely heavy losses of species, and some terrestrial vertebrate groups very nearly became extinct at the end-Permian. Some of the surviving groups did not persist for long past this period, while others that barely survived went on to produce diverse and long-lasting lineages. Yet it took 30 million years for the terrestrial vertebrate fauna to fully recover both numerically and ecologically.
Possible explanations of these patterns
An analysis of marine fossils from the Permian's final Changhsingian stage found that marine organisms with low tolerance for hypercapnia (high concentration of carbon dioxide) had high extinction rates, while the most tolerant organisms had very slight losses.
The most vulnerable marine organisms were those that produced calcareous hard parts (i.e., from calcium carbonate) and had low metabolic rates and weak respiratory systems—notably calcareous sponges, rugose and tabulate corals, calcite-depositing brachiopods, bryozoans, and echinoderms; about 81% of such genera became extinct. Close relatives without calcareous hard parts suffered only minor losses, for example sea anemones, from which modern corals evolved. Animals with high metabolic rates, well-developed respiratory systems, and non-calcareous hard parts had negligible losses—except for conodonts, in which 33% of genera died out.
This pattern is consistent with what is known about the effects of hypoxia, a shortage but not a total absence of oxygen. However, hypoxia cannot have been the only killing mechanism for marine organisms. Nearly all of the continental shelf waters would have had to become severely hypoxic to account for the magnitude of the extinction, but such a catastrophe would make it difficult to explain the very selective pattern of the extinction. Models of the Late Permian and Early Triassic atmospheres show a significant but protracted decline in atmospheric oxygen levels, with no acceleration near the P–Tr boundary. Minimum atmospheric oxygen levels in the Early Triassic are never less than present day levels—the decline in oxygen levels does not match the temporal pattern of the extinction.
Marine organisms are more sensitive to changes in CO2 (carbon dioxide) levels than are terrestrial organisms for a variety of reasons. CO2 is 28 times more soluble in water than is oxygen. Marine animals normally function with lower concentrations of CO2 in their bodies than land animals, as the removal of CO2 in air-breathing animals is impeded by the need for the gas to pass through the respiratory system's membranes (lungs' alveolus, tracheae, and the like), even when CO2 diffuses more easily than oxygen. In marine organisms, relatively modest but sustained increases in CO2 concentrations hamper the synthesis of proteins, reduce fertilization rates, and produce deformities in calcareous hard parts. In addition, an increase in CO2 concentration is inevitably linked to ocean acidification, consistent with the preferential extinction of heavily calcified taxa and other signals in the rock record that suggest a more acidic ocean. The decrease in ocean pH is calculated to be up to 0.7 units.
It is difficult to analyze extinction and survival rates of land organisms in detail, because few terrestrial fossil beds span the Permian–Triassic boundary. Triassic insects are very different from those of the Permian, but a gap in the insect fossil record spans approximately 15 million years from the late Permian to early Triassic. The best-known record of vertebrate changes across the Permian–Triassic boundary occurs in the Karoo Supergroup of South Africa, but statistical analyses have so far not produced clear conclusions. However, analysis of the fossil river deposits of the floodplains indicate a shift from meandering to braided river patterns, indicating an abrupt drying of the climate. The climate change may have taken as little as 100,000 years, prompting the extinction of the unique Glossopteris flora and its herbivores, followed by the carnivorous guild. End-Permian extinctions did not occur at an instantaneous time horizon; particularly, floral extinction was delayed in time
Earlier analyses indicated that life on Earth recovered quickly after the Permian extinctions, but this was mostly in the form of disaster taxa, opportunist organisms such as the hardy Lystrosaurus. Research published in 2006 indicates that the specialized animals that formed complex ecosystems, with high biodiversity, complex food webs and a variety of niches, took much longer to recover. It is thought that this long recovery was due to the successive waves of extinction, which inhibited recovery, and prolonged environmental stress to organisms, which continued into the Early Triassic. Research indicates that recovery did not begin until the start of the mid-Triassic, 4 to 6 million years after the extinction; and some writers estimate that the recovery was not complete until Ma after the P–Tr extinction, i.e. in the 30late Triassic.
A study published in the journal Science found that during the Great Extinction the oceans' surface temperatures reached 40 °C (104 °F), which explains why recovery took so long: it was simply too hot for life to survive. Of course, not all of the Earth's surface was 40°, and if it was simply too hot for life to survive then nothing would have survived. Perhaps anoxia provides another aspect of what delayed the recovery.
During the early Triassic (4 to 6 million years after the P–Tr extinction), the plant biomass was insufficient to form coal deposits, which implies a limited food mass for herbivores. River patterns in the Karoo changed from meandering to braided, indicating that vegetation there was very sparse for a long time.
Each major segment of the early Triassic ecosystem—plant and animal, marine and terrestrial—was dominated by a small number of genera, which appeared virtually worldwide, for example: the herbivorous therapsid Lystrosaurus (which accounted for about 90% of early Triassic land vertebrates) and the bivalves Claraia, Eumorphotis, Unionites and Promylina. A healthy ecosystem has a much larger number of genera, each living in a few preferred types of habitat.
Disaster taxa took advantage of the devastated ecosystems and enjoyed a temporary population boom and increase in their territory. Microconchids are the dominant component of otherwise impoverished Early Triassic encrusting assemblages. For example: Lingula (a brachiopod); stromatolites, which had been confined to marginal environments since the Ordovician; Pleuromeia (a small, weedy plant); Dicroidium (a seed fern).
Changes in marine ecosystems
Prior to the extinction, about two-thirds of marine animals were sessile and attached to the sea floor but, during the Mesozoic, only about half of the marine animals were sessile while the rest were free-living. Analysis of marine fossils from the period indicated a decrease in the abundance of sessile epifaunal suspension feeders such as brachiopods and sea lilies and an increase in more complex mobile species such as snails, sea urchins and crabs.
Before the Permian mass extinction event, both complex and simple marine ecosystems were equally common; after the recovery from the mass extinction, the complex communities outnumbered the simple communities by nearly three to one, and the increase in predation pressure led to the Mesozoic Marine Revolution.
Bivalves were fairly rare before the P–Tr extinction but became numerous and diverse in the Triassic, and one group, the rudist clams, became the Mesozoic's main reef-builders. Some researchers think much of this change happened in the 5 million years between the two major extinction pulses.
Crinoids ("sea lilies") suffered a selective extinction, resulting in a decrease in the variety of their forms. Their ensuing adaptive radiation was brisk, and resulted in forms possessing flexible arms becoming widespread; motility, predominantly a response to predation pressure, also became far more prevalent.
Lystrosaurus, a pig-sized herbivorous dicynodont therapsid, constituted as much as 90% of some earliest Triassic land vertebrate fauna. Smaller carnivorous cynodont therapsids also survived, including the ancestors of mammals. In the Karoo region of southern Africa, the therocephalians Tetracynodon, Moschorhinus and Ictidosuchoides survived, but do not appear to have been abundant in the Triassic.
Archosaurs (which included the ancestors of dinosaurs and crocodilians) were initially rarer than therapsids, but they began to displace therapsids in the mid-Triassic. In the mid to late Triassic, the dinosaurs evolved from one group of archosaurs, and went on to dominate terrestrial ecosystems during the Jurassic and Cretaceous. This "Triassic Takeover" may have contributed to the evolution of mammals by forcing the surviving therapsids and their mammaliform successors to live as small, mainly nocturnal insectivores; nocturnal life probably forced at least the mammaliforms to develop fur and higher metabolic rates, while losing part of the differential color-sensitive retinal receptors reptilians and birds preserved.
Some temnospondyl amphibians made a relatively quick recovery, in spite of nearly becoming extinct. Mastodonsaurus and trematosaurians were the main aquatic and semiaquatic predators during most of the Triassic, some preying on tetrapods and others on fish.
Land vertebrates took an unusually long time to recover from the P–Tr extinction; Palaeontologist Michael Benton estimated the recovery was not complete until million years after the extinction, i.e. not until the Late Triassic, in which dinosaurs, 30pterosaurs, crocodiles, archosaurs, amphibians, and mammaliforms were abundant and diverse.
Pinpointing the exact cause or causes of the Permian–Triassic extinction event is difficult, mostly because the catastrophe occurred over 250 million years ago, and since then much of the evidence that would have pointed to the cause has been destroyed by now or is concealed deep within the Earth under many layers of rock. The sea floor is also completely recycled every 200 million years by the ongoing process of plate tectonics and seafloor spreading, leaving no useful indications beneath the ocean.
Scientists have accumulated a fairly significant amount of evidence for causes, and several mechanisms have been proposed for the extinction event. The proposals include both catastrophic and gradual processes (similar to those theorized for the Cretaceous–Paleogene extinction event).
- The catastrophic group includes one or more large bolide impact events, increased volcanism, and sudden release of methane from the sea floor, either due to dissociation of methane hydrate deposits or metabolism of organic carbon deposits by methanogenic microbes.
- The gradual group includes sea level change, increasing anoxia, and increasing aridity.
Any hypothesis about the cause must explain the selectivity of the event, which affected organisms with calcium carbonate skeletons most severely; the long period (4 to 6 million years) before recovery started, and the minimal extent of biological mineralization (despite inorganic carbonates being deposited) once the recovery began.
Evidence that an impact event may have caused the Cretaceous–Paleogene extinction event (Cretaceous-Tertiary) has led to speculation that similar impacts may have been the cause of other extinction events, including the P–Tr extinction, and thus to a search for evidence of impacts at the times of other extinctions and for large impact craters of the appropriate age.
Reported evidence for an impact event from the P–Tr boundary level includes rare grains of shocked quartz in Australia and Antarctica; fullerenes trapping extraterrestrial noble gases; meteorite fragments in Antarctica; and grains rich in iron, nickel and silicon, which may have been created by an impact. However, the accuracy of most of these claims has been challenged. Quartz from Graphite Peak in Antarctica, for example, once considered "shocked", has been re-examined by optical and transmission electron microscopy. The observed features were concluded to be not due to shock, but rather to plastic deformation, consistent with formation in a tectonic environment such as volcanism.
An impact crater on the sea floor would be evidence of a possible cause of the P–Tr extinction, but such a crater would by now have disappeared. As 70% of the Earth's surface is currently sea, an asteroid or comet fragment is now perhaps more than twice as likely to hit ocean as it is to hit land. However, Earth has no ocean-floor crust more than 200 million years old because the "conveyor belt" process of seafloor spreading and subduction destroys it within that time. Craters produced by very large impacts may be masked by extensive flood basalting from below after the crust is punctured or weakened. Subduction should not, however, be entirely accepted as an explanation of why no firm evidence can be found: as with the K-T event, an ejecta blanket stratum rich in siderophilic elements (such as iridium) would be expected to be seen in formations from the time.
One attraction of large impact theories is that theoretically they could trigger other cause-considered extinction-paralleling phenomena, such as the Siberian Traps eruptions (see below) as being either an impact site or the antipode of an impact site. The abruptness of an impact also explains why more species did not rapidly evolve to survive, as would be expected if the Permian-Triassic event had been slower and less global than a meteorite impact.
Possible impact sites
Several possible impact craters have been proposed as the site of an impact causing the P–Tr extinction, including the Bedout structure off the northwest coast of Australia and the hypothesized Wilkes Land crater of East Antarctica. In each case, the idea that an impact was responsible has not been proven and has been widely criticized. In the case of Wilkes Land, the age of this sub-ice geophysical feature is very uncertain – it may be later than the Permian–Triassic extinction.
The 40 km (25 mi) Araguainha crater in Brazil has been most recently dated to 254.7 ± 2.5 million years ago, overlapping with estimates for the Permo-Triassic boundary. Much of the local rock was oil shale. The estimated energy released by the Araguainha impact is insufficient to be a direct cause of the global mass extinction, but the colossal local earth tremors would have released huge amounts of oil and gas from the shattered rock. The resulting sudden global warming might have precipitated the Permian–Triassic extinction event.
The final stages of the Permian had two flood basalt events. A small one, the Emeishan Traps in China, occurred at the same time as the end-Guadalupian extinction pulse, in an area close to the equator at the time. The flood basalt eruptions that produced the Siberian Traps constituted one of the largest known volcanic events on Earth and covered over 2,000,000 square kilometres (770,000 sq mi) with lava. The date of the Siberian Traps eruptions and the extinction event are in good agreement.
The Emeishan and Siberian Traps eruptions may have caused dust clouds and acid aerosols, which would have blocked out sunlight and thus disrupted photosynthesis both on land and in the photic zone of the ocean, causing food chains to collapse. The eruptions may also have caused acid rain when the aerosols washed out of the atmosphere. That may have killed land plants and molluscs and planktonic organisms which had calcium carbonate shells. The eruptions would also have emitted carbon dioxide, causing global warming. When all of the dust clouds and aerosols washed out of the atmosphere, the excess carbon dioxide would have remained and the warming would have proceeded without any mitigating effects.
The Siberian Traps had unusual features that made them even more dangerous. Pure flood basalts produce fluid, low-viscosity lava and do not hurl debris into the atmosphere. It appears, however, that 20% of the output of the Siberian Traps eruptions was pyroclastic (consisted of ash and other debris thrown high into the atmosphere), increasing the short-term cooling effect. The basalt lava erupted or intruded into carbonate rocks and into sediments that were in the process of forming large coal beds, both of which would have emitted large amounts of carbon dioxide, leading to stronger global warming after the dust and aerosols settled.
In January 2011, a team, led by Stephen Grasby of the Geological Survey of Canada—Calgary, reported evidence that volcanism caused massive coal beds to ignite, possibly releasing more than 3 trillion tons of carbon. The team found ash deposits in deep rock layers near what is now Buchanan Lake. According to their article, "coal ash dispersed by the explosive Siberian Trap eruption would be expected to have an associated release of toxic elements in impacted water bodies where fly ash slurries developed.... Mafic megascale eruptions are long-lived events that would allow significant build-up of global ash clouds." In a statement, Grasby said, "In addition to these volcanoes causing fires through coal, the ash it spewed was highly toxic and was released in the land and water, potentially contributing to the worst extinction event in earth history." In 2013, QY Tang reported the total amounts of important volatiles emitted from the Siberian Traps are 8.5 × 107 Tg CO2, 4.4 × 106 Tg CO, 7.0 × 106 Tg H2S and 6.8 × 107 Tg SO2, the data support a popular notion that the end-Permian mass extinction on the Earth was caused by the emission of enormous amounts of volatiles from the Siberian Traps into the atmosphere.
Methane hydrate gasification
Scientists have found worldwide evidence of a swift decrease of about 1% in the 13C/12C isotope ratio in carbonate rocks from the end-Permian. This is the first, largest, and most rapid of a series of negative and positive excursions (decreases and increases in 13C/12C ratio) that continues until the isotope ratio abruptly stabilised in the middle Triassic, followed soon afterwards by the recovery of calcifying life forms (organisms that use calcium carbonate to build hard parts such as shells).
- Gases from volcanic eruptions have a 13C/12C ratio about 0.5 to 0.8% below standard (δ13C about −0.5 to −0.8%), but an assessment made in 1995 concluded that the amount required to produce a reduction of about 1.0% worldwide requires eruptions greater by orders of magnitude than any for which evidence has been found. (However, this analysis addressed only CO2 produced by the magma itself, not from interactions with carbon bearing sediments, as later proposed.)
- A reduction in organic activity would extract 12C more slowly from the environment and leave more of it to be incorporated into sediments, thus reducing the 13C/12C ratio. Biochemical processes preferentially use the lighter isotopes since chemical reactions are ultimately driven by electromagnetic forces between atoms and lighter isotopes respond more quickly to these forces, but a study of a smaller drop of 0.3 to 0.4% in 13C/12C (δ13C −3 to −4 ‰) at the Paleocene-Eocene Thermal Maximum (PETM) concluded that even transferring all the organic carbon (in organisms, soils, and dissolved in the ocean) into sediments would be insufficient: even such a large burial of material rich in 12C would not have produced the 'smaller' drop in the 13C/12C ratio of the rocks around the PETM.
- Buried sedimentary organic matter has a 13C/12C ratio 2.0 to 2.5% below normal (δ13C −2.0 to −2.5%). Theoretically, if the sea level fell sharply, shallow marine sediments would be exposed to oxidization. But 6500–8400 gigatons (1 gigaton = 109 metric tons) of organic carbon would have to be oxidized and returned to the ocean-atmosphere system within less than a few hundred thousand years to reduce the 13C/12C ratio by 1.0%, which is not thought to be a realistic possibility. Moreover, sea levels were rising rather than falling at the time of the extinction.
- Rather than a sudden decline in sea level, intermittent periods of ocean-bottom hyperoxia and anoxia (high-oxygen and low- or zero-oxygen conditions) may have caused the 13C/12C ratio fluctuations in the Early Triassic; and global anoxia may have been responsible for the end-Permian blip. The continents of the end-Permian and early Triassic were more clustered in the tropics than they are now, and large tropical rivers would have dumped sediment into smaller, partially enclosed ocean basins at low latitudes. Such conditions favor oxic and anoxic episodes; oxic/anoxic conditions would result in a rapid release/burial, respectively, of large amounts of organic carbon, which has a low 13C/12C ratio because biochemical processes use the lighter isotopes more. That or another organic-based reason may have been responsible for both that and a late Proterozoic/Cambrian pattern of fluctuating 13C/12C ratios.
Other hypotheses include mass oceanic poisoning releasing vast amounts of CO2 and a long-term reorganisation of the global carbon cycle.
Prior to consideration of the inclusion of roasting carbonate sediments by volcanism, the only proposed mechanism sufficient to cause a global 1% reduction in the 13C/12C ratio was the release of methane from methane clathrates,. Carbon-cycle models confirm that it would have had enough effect to produce the observed reduction. Methane clathrates, also known as methane hydrates, consist of methane molecules trapped in cages of water molecules. The methane, produced by methanogens (microscopic single-celled organisms), has a 13C/12C ratio about 6.0% below normal (δ13C −6.0%). At the right combination of pressure and temperature, it gets trapped in clathrates fairly close to the surface of permafrost and in much larger quantities at continental margins (continental shelves and the deeper seabed close to them). Oceanic methane hydrates are usually found buried in sediments where the seawater is at least 300 m (980 ft) deep. They can be found up to about 2,000 m (6,600 ft) below the sea floor, but usually only about 1,100 m (3,600 ft) below the sea floor.
The area covered by lava from the Siberian Traps eruptions is about twice as large as was originally thought, and most of the additional area was shallow sea at the time. The seabed probably contained methane hydrate deposits, and the lava caused the deposits to dissociate, releasing vast quantities of methane. A vast release of methane might cause significant global warming since methane is a very powerful greenhouse gas. Strong evidence suggests the global temperatures increased by about 6 °C (10.8 °F) near the equator and therefore by more at higher latitudes: a sharp decrease in oxygen isotope ratios (18O/16O); the extinction of Glossopteris flora (Glossopteris and plants that grew in the same areas), which needed a cold climate, with its replacement by floras typical of lower paleolatitudes.
However, the pattern of isotope shifts expected to result from a massive release of methane does not match the patterns seen throughout the early Triassic. Not only would such a cause require the release of five times as much methane as postulated for the PETM, but would it also have to be reburied at an unrealistically high rate to account for the rapid increases in the 13C/12C ratio (episodes of high positive δ13C) throughout the early Triassic before it was released again several times.
Evidence for widespread ocean anoxia (severe deficiency of oxygen) and euxinia (presence of hydrogen sulfide) is found from the Late Permian to the Early Triassic. Throughout most of the Tethys and Panthalassic Oceans, evidence for anoxia, including fine laminations in sediments, small pyrite framboids, high uranium/thorium ratios, and biomarkers for green sulfur bacteria, appear at the extinction event. However, in some sites, including Meishan, China, and eastern Greenland, evidence for anoxia precedes the extinction. Biomarkers for green sulfur bacteria, such as isorenieratane, the diagenetic product of isorenieratene, are widely used as indicators of photic zone euxinia because green sulfur bacteria require both sunlight and hydrogen sulfide to survive. Their abundance in sediments from the P-T boundary indicates hydrogen sulfide was present even in shallow waters.
This spread of toxic, oxygen-depleted water would have been devastating for marine life, producing widespread die-offs. Models of ocean chemistry show that anoxia and euxinia would have been closely associated with hypercapnia (high levels of carbon dioxide). This suggests that poisoning from hydrogen sulfide, anoxia, and hypercapnia acted together as a killing mechanism. Hypercapnia best explains the selectivity of the extinction, but anoxia and euxinia probably contributed to the high mortality of the event. The persistence of anoxia through the Early Triassic may explain the slow recovery of marine life after the extinction. Models also show that anoxic events can cause catastrophic hydrogen sulfide emissions into the atmosphere (see below).
The sequence of events leading to anoxic oceans may have been triggered by carbon dioxide emissions from the eruption of the Siberian Traps. In that scenario, warming from the enhanced greenhouse effect would reduce the solubility of oxygen in seawater, causing the concentration of oxygen to decline. Increased weathering of the continents due to warming and the acceleration of the water cycle would increase the riverine flux of phosphate to the ocean. The phosphate would have supported greater primary productivity in the surface oceans. The increase in organic matter production would have caused more organic matter to sink into the deep ocean, where its respiration would further decrease oxygen concentrations. Once anoxia became established, it would have been sustained by a positive feedback loop because deep water anoxia tends to increase the recycling efficiency of phosphate, leading to even higher productivity.
Hydrogen sulfide emissions
A severe anoxic event at the end of the Permian would have allowed sulfate-reducing bacteria to thrive, causing the production of large amounts of hydrogen sulfide in the anoxic ocean. Upwelling of this water may have released massive hydrogen sulfide emissions into the atmosphere and would poison terrestrial plants and animals and severely weaken the ozone layer, exposing much of the life that remained to fatal levels of UV radiation. Indeed, biomarker evidence for anaerobic photosynthesis by Chlorobiaceae (green sulfur bacteria) from the Late-Permian into the Early Triassic indicates that hydrogen sulfide did upwell into shallow waters because these bacteria are restricted to the photic zone and use sulfide as an electron donor.
The hypothesis has the advantage of explaining the mass extinction of plants, which would have added to the methane levels and should otherwise have thrived in an atmosphere with a high level of carbon dioxide. Fossil spores from the end-Permian further support the theory: many show deformities that could have been caused by ultraviolet radiation, which would have been more intense after hydrogen sulfide emissions weakened the ozone layer.
The supercontinent Pangaea
About halfway through the Permian (in the Kungurian age of the Permian's Cisuralian epoch), all the continents joined to form the supercontinent Pangaea, surrounded by the superocean Panthalassa, although blocks that are now parts of Asia did not join the supercontinent until very late in the Permian. The configuration severely decreased the extent of shallow aquatic environments, the most productive part of the seas, and it exposed formerly isolated organisms of the rich continental shelves to competition from invaders. Pangaea's formation would also have altered both oceanic circulation and atmospheric weather patterns, creating seasonal monsoons near the coasts and an arid climate in the vast continental interior.
Marine life suffered very high but not catastrophic rates of extinction after the formation of Pangaea (see the diagram "Marine genus biodiversity" at the top of this article), almost as high as in some of the "Big Five" mass extinctions. The formation of Pangaea seems not to have caused a significant rise in extinction levels on land, and, in fact, most of the advance of the therapsids and increase in their diversity seems to have occurred in the late Permian, after Pangaea was almost complete. Thus, it seems likely that Pangaea initiated a long period of increased marine extinctions but was not directly responsible for the "Great Dying" and the end of the Permian.
A hypothesis published in 2014 posits that a genus of anaerobic methanogenic archaea known as Methanosarcina was responsible for the event. Three lines of evidence suggest that these microbes acquired a new metabolic pathway via gene transfer at about that time, enabling them to efficiently metabolize acetate into methane. That would have led to their exponential reproduction, allowing them to rapidly consume vast deposits of organic carbon that had accumulated in the marine sediment. The result would have been a sharp buildup of methane and carbon dioxide in the Earth's oceans and atmosphere, in a manner that may be consistent with the 13C/12C isotopic record. Massive volcanism facilitated this process by releasing large amounts of nickel, a scarce metal which is a cofactor for an enzymes involved in producing methane. On the other hand, in the canonical Meishan sections, the Nickel concentration increases somewhat after the δ13C concentrations have begun to fall.
Combination of causes
Possible causes supported by strong evidence appear to describe a sequence of catastrophes, each worse than the last: the Siberian Traps eruptions were bad enough alone, but because they occurred near coal beds and the continental shelf, they also triggered very large releases of carbon dioxide and methane. The resultant global warming may have caused perhaps the most severe anoxic event in the oceans' history: according to this theory, the oceans became so anoxic, anaerobic sulfur-reducing organisms dominated the chemistry of the oceans and caused massive emissions of toxic hydrogen sulfide.
However, there may be some weak links in this chain of events: the changes in the 13C/12C ratio expected to result from a massive release of methane do not match the patterns seen throughout the early Triassic; and the types of oceanic thermohaline circulation that may have existed at the end of the Permian are not likely to have supported deep-sea anoxia.
- Extinction events
- List of unconfirmed impact craters on Earth – for unconfirmed craters similar to or larger than Chicxulub
- Siberian traps
- Wilkes Land crater
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West Lafayette, Indiana - Astronomers have identified two planets outside our solar system, known as exoplanets, that could support life. The planets, which orbit Teegarden’s star, are unlikely to have intense solar flares or other dangerous activity that could prevent life there. The findings were published in the journal Astronomy and Astrophysics.
We haven’t actually seen these planets, but their existence was inferred based on data that suggests they’re there. However, this could change as high-powered telescopes are being developed around the world.
Briony Horgan, an assistant professor of earth, atmospheric and planetary sciences at Purdue University, researches the geologic processes that shaped the moon and Mars. She is a participating scientist on NASA's Mars Science Laboratory rover mission and a co-investigator on NASA’s upcoming Mars 2020 rover mission, the first step toward bringing samples back from the planet.
“There are two special things about these planets. First, they’re just about the same size as Earth, which means they can hold on to their atmosphere for long periods of time. Smaller planets like Mars don’t have enough gravity to hold onto their atmosphere, which is why Mars is the cold and barren planet it is today,” Horgan said. “Second, they’re at just the right distance from their host star. They receive about the same amount of light and heat that Earth does, meaning they can support liquid water on their surface. We call this distance from the star the ‘habitable zone.’”
“These planets were detected because astronomers saw that their gravity was tugging on their host star and moving it around slightly. So we know their mass and how far they are from the star they orbit, but we don't know their diameters, and more work will be needed to figure out exactly how big they are. Exoplanets are exciting to find, but they’re also hard to study because they’re so small and dim compared to their stars.” | 0.89347 | 3.482518 |
Around 800 scientists from around the world met at the European Planetary Science Congress in Riga this week to present the latest findings on our home planet and Solar System.
Here, we present some of our favourite stories from this year’s conference.
European lunar lander location revealed
Images of the Moon taken by NASA’s Lunar Reconnaissance Orbiter have enabled the pinpointing of the impact location of ESA’s SMART-1 lunar spacecraft
(P Stooke/B Foing et al 2017/ NASA/GSFC/Arizona State University)
A lunar scientist has been able to pinpoint the final resting place of SMART-1, the first lunar mission by the European Space Agency which purposely impacted on the surface of the Moon 11 years ago.
At the time of the impact, the Canada-France-Hawaii Telescope was able to locate a flash caused by the impact of the spacecraft, but its exact location was not known.
The location is now confirmed as 34.262° south and 46.193° west.
It was discovered by Dr Phil Stooke of Western University, Ontario, Canada using images captured by NASA’s Lunar Reconnaissance Orbiter.
They show a gouge in the surface about 4m by 20m.
“SMART-1 had a hard, grazing and bouncing landing at two kilometres per second on the surface of the Moon,” says ESA SMART-1 Project Scientist, Bernard Foing.
“There were no other spacecraft in orbit at the time to give a close-up view of the impact, and finding the precise location became a ‘cold case’ for more than 10 years.
The next steps will be to send a robotic investigator to examine the remains of the SMART-1 spacecraft body and ‘wings’ of the solar arrays.”
Martian comet encounter complicated by solar winds
An image by the Hubble Space Telescope of Comet C/2013 A1 (Siding Spring), which made a close pass by Mars on 19 october 2015.
Credit: NASA, ESA, and J.-Y. Li (Planetary Science Institute)
Studies of the effects of a comet that made a close encounter with Mars have been complicated because of a wave of electrically charged particles that blasted out from the Sun at about the same time.
Comet C/2013 A1 (Siding Spring) passed 140,000 km from Mars on 19 October 2014, depositing debris in the Martian atmosphere.
Space agencies around the world coordinated spacecraft to observe what became the largest meteor shower in recorded history.
But analysis of the event has been complicated because of a powerful coronal mass ejection (CME) from the Sun that occurred 44 hours before the comet arrived.
Data from ESA’s Mars Express mission, NASA’s MAVEN and Mars Odyssey orbiters indicates showers of energetic oxygen ions and dust rained on Mars during the time the planet was engulfed by the comet’s outer atmosphere (its coma).
These ions were accelerated by a powerful ‘solar wind’ of charged particles and delivered into the Red Planet’s atmosphere.
But the amount of ionised water interacting with the Martian atmosphere was smaller than expected.
Analysis suggests that most of the ionised water from the comet was actually carried away by the solar wind, rather than dropping into Mars’s atmosphere.
Diamonds are a geologist’s best friend
A cathode luminiscence image of a polished diamond plate, revealing the diamond’s growth history. Analysis of diamonds has suggested they may have been created relatively recently, in geological terms.
Credit: Michael Gress
Earth may have produced diamonds more recently than thought, according to a study of the Venetia mine in South Africa.
The study suggests that some volcanic events on Earth may still be able to create the kind of hot conditions that were thought to only have existed early in the history of our planet, before it cooled.
Researchers from the Vrije Universiteit Amsterdam studied 26 diamonds that were formed under extreme conditions in Earth’s mantle.
They found two groups, one of which displayed geologically ‘young’ diamonds.
Nine have an age of about 3 billion years and are linked to volcanism caused by the breakup of an old continent.
But ten are dated at just over a billion years old, correlating with a volcanic event in Zimbabwe that occurred 1.1 billion years ago.
Craters proven to be of extra-terrestrial origin
The seabed relief of the Neugrund crater area. Is this the best preserved submarine crater we know of?
Credit: Sten Suuroja
Analysis of craters in the Baltic region has given scientists insights into the impacts that created them.
In Põlva County, Estonia, studies of Illumetsa, a pair of small craters, revealed small pieces of charcoaled tree fragments buried about 60 cm around the rim.
Carbon dating puts the formation of the craters at about 7,170 and 7,000 years ago, suggesting they both formed from a meteorite impact.
“Until now, the two craters had not been firmly proven to be of extraterrestrial origin: neither remnants of the projectile nor other identification criteria had been found up to this point,” says Dr Anna Losiak of the Polish Academy of Sciences in Warsaw.
Another study, this time of the Neugrund crater at the bottom of the sea in the Gulf of Finland, revealed it to have been formed 535 million years ago.
The projectile was about a kilometer in diameter and hit the sea where the depth was about 100 metres.
It was then buried under sediment and remained concealed until the Ice Age.
It could be the best preserved example of an undersea crater in the world.
Attack of the nano-spaceprobes
An artist’s concept of one of 50 nano-spacecraft that could visit over 300 asteroids in just over three years.
A fleet of spaceships could soon be leaving Earth to explore the asteroid belt.
A new project suggests sending 50 nano-spacecraft, powered by electric solar wind sails, to fly as close as 1,000 km from an asteroid to capture images and spectroscopic data.
Once the spacecraft have visited up to seven different asteroids, they would then return with their data to Earth.
“Asteroids are very diverse and, to date, we’ve only seen a small number at close range.
To understand them better, we need to study a large number in situ.
The only way to do this affordably is by using small spacecraft,” says Pekka Janhunen from the Finnish Meteorological Institute.
Bigger is better for planetary atmospheres
An artist’s impression of an exoplanetary system. Size, not mass, could be a key factor in whether a planet’s atmosphere can be detected.
It is size, rather than mass, that counts when it comes to exoplanet atmospheres.
This is the conclusion of a survey of 30 hot Jupiters that looked for gasses around the planets.
It found strong signs of an atmosphere around 16, all of which had water vapour in their atmosphere.
The survey found that the larger the planet was, the more likely it was to have an atmosphere, regardless of its mass, implying that gravitational pull has only a minor effect on the evolution of a planet’s atmosphere.
“30 exoplanet atmospheres is a great step forward compared to the handful of planets observed years ago, but not yet big-data.
We are working at launching dedicated space missions in the next decade to bring this number up to hundreds or even thousands,” says Giovanna Tinetti from University College London.
The devil’s in the dust
Samples of a dust devil are captured during field campaign ‘Morocco 2016’. The samples are still under analysis.
Credit: Jan Raack/Dennis Reiss.
Dust devils – swirling columns of dust and sand – could transport fine particles for thousands of kilometres on both Mars and Earth, according to a study by Dr Jan Raack of the Open University and an international team of scientists.
The vortices are often seen in the deserts of both planets, lifting particles of dust high into the atmosphere.
A study of dust devils on Earth found that around two thirds of the particles kicked up by a dust devil remain in the atmosphere after the phenomenon has stopped.
This amount of dust is large enough that it could impact the planet’s climate and weather.
However, dust devils on Earth are affected by the water in the atmosphere.
On a planet as arid as Mars, it’s thought that even more dust could remain suspended and have a much larger impact on the planet’s weather. | 0.909992 | 3.334409 |
Chandra data reveal a ring of bright X-ray sources encircling the galaxy, which are thought to contain either black holes or neutron stars. Image credit: X-ray: NASA/CXC/INAF/A. Wolter et al; Optical: NASA/STScI
Astronomers have used NASA’s Chandra X-ray Observatory to discover a ring of black holes or neutron stars in a galaxy 300 million light years from Earth. This ring, while not wielding power over Middle Earth, may help scientists better understand what happens when galaxies smash into one another in catastrophic impacts.
In the new composite image shown above of the galaxy AM 0644-741 (AM 0644 for short), X-rays from Chandra (purple) have been combined with optical data from NASA’s Hubble Space Telescope (red, green, and blue). The Chandra data reveal the presence of very bright X-ray sources, most likely binary systems powered by either a stellar-mass black hole or neutron star, in a remarkable ring. The results are reported in a new paper led by Anna Wolter from INAF-Osservatorio Astronomico di Brera in Milano, Italy.
Where did the ring of black holes or neutron stars in AM 0644 come from? Astronomers think that it was created when one galaxy was pulled into another galaxy by the force of ... | 0.803288 | 3.44087 |
The big science event in August was the total eclipse of the Sun which will traverse the mainland US on August 21. It’s an amazing, awe-inspiring event, no doubt, and it gives astronomers and other scientists some well-deserved attention from the media.
But the eclipse also had an unintended consequence: it has figurately and literally overshadowed (pun intended) the 40th anniversary of the launch of the twin Voyager spacecraft on their “grand tour” of the outer planets – Jupiter Saturn, Uranus, and Neptune – due to a fortunate planetary alignment which occurs only once every 176 years.
Both spacecraft have travelled far beyond their original objectives. Voyager 2 was launched from Cape Canaveral on Aug. 20, 1977 and is now almost 11 billion miles (18 billion km) distant, while Voyager 1 followed a few weeks later and is now actually ahead of Voyager 2 at 13 billion miles (21 billion km). It is the world's only craft to reach interstellar space, although Voyager 2 is expected to cross that boundary during the next few years, Figure 1 .
The concept of the paired Voyager spacecraft mission was to undertake a grand tour of the four large planets, a trajectory made possible due to a rare planetary alignment worked out by complex astrophysics “mechanics.” (Image courtesy of NASA/JPL)
Both are still transmitting weakly (at low rates, of course) working surprisingly well far beyond their design life, Figure 2 . In addition to instrumentation, each Voyager carries a 12-inch, gold-plated copper phonograph record (remember, there were no CDs or MP3s back then) containing messages from Earth: Beethoven's Fifth, chirping crickets, a baby's cry, a kiss, wind and rain, a thunderous moon rocket launch, African pygmy songs, Solomon Island panpipes, a Peruvian wedding song and greetings in dozens of languages. There are also more than 100 electronic images on each record showing 20th -century life, traffic jams and all.
The Voyagers packed a lot of instrumentation into their limited payload, and the instrumentation of the period was far larger, more power hungry, and less sophisticated than what we now routinely use.(Image courtesy of NASA/JPL)
The mission has been managed by the Jet Propulsion Laboratory since its inception, and in some cases, three generations of staffers have been on the project. There are so many amazing aspects to the paired mission that it is hard to know where to start or which to cite. Obviously, the components on these spacecraft are ancient and crude by our standards and mostly analog, but they have certainly done well.
The list of what is still operating is impressive, Figure 3 . Many functions and tasks which we now routinely assign to low-power microcontrollers had to be implemented with discrete digital logic and components. Nor could designers use the “latest, greatest” just-released components, either; they had to restrict themselves only to ones with a solid, verified track record. There wasn’t much detailed understanding on the challenges of space travel either, such as solar-heating effects, long periods of extreme cold, or cosmic radiation.
Powerful design tools we assume available such as CAD, simulation, BOM management, and project tracking, simply didn’t exist or were also crude. It’s a tribute to the designers, engineers, and scientists that they did so much with what they had, and did not say “we can’t do it, we don’t have the tools yet.” They made it happen with what they had, the only environment they knew.
Even after 40 years, JPL reports that some of the instrumentation packages are still turned on and available – truly astounding.(Image courtesy of NASA/JPL)
There’s more to the Voyager story than the spacecraft themselves, of course. There’s the challenge of providing power, produced by thermoelectric (thermocouple) generators (TEGs) heated by the decay of radioactive material. Although not efficient (around 10 to 20 percent, depending on various factors) they have a long-life and are reliable, as there is no chemical aspect to break down.
There’s also the challenge of tracking ad communicating with the Voyagers at such distances, given their weak output and limited antenna size. Both the Earth-based and the spacecraft receivers are dealing with SNRs so low we can’t believe any sort of acceptable data rate and BER are possible, yet there is a link. And how many engineers can accept a working on project where the one-way propagation delay is measured in hours, now at about 20 hours for Voyager 1 and 16 hours for Voyager 2)?
There’s also a fascinating but little-known prequel story to the Voyager missions. Even with the rare planetary alignment, the journey would have not been possible without the benefit of a gravity slingshot, in which the gravitational pull of a planet is used to accelerate the spacecraft on its journey beyond that planet. This is now a routine undertaking, and is even occasionally used to slow a spacecraft down into a desired path while minimizing fuel consumption. The slingshot would not have been possible without the work of Michael Minovitch, a UCLA graduate student who had a summer job at JPL, Reference 1 . In 1961, he conceived of the slingshot and worked out the details as an after-hours, “on his own” project; you can read a scanned pdf of his project paper explaining the concept and the planetary mechanics at Reference 2 . It, too, is a throwback in time, as it is done on a typewriter (what’s that?), the drawings are done by hand, and the special characters (mostly Greek, plus others) are hand-written into the text and figures!
In addition to the interesting mission information and perspectives at the JPL web site (see References 3 through 6 ), there’s a well-written book proving a lengthy but fascinating look at the dual missions, “Voyager: seeking newer worlds in the third great age of discovery,” by Stephen J. Pyne. It’s worth checking out.
Have you followed the Voyager missions? Could you work on a project with such a long life to “completion”, so many periods of “nothingness”, and one-way path delays of tens of hours?
- IEEE Engineering360
- ”A Method for Determining Interplanetary Free-Fall Reconnaissance Trajectories”, Jet Propulsion Laboratory, Technical Memo #312-130, Michael Minovitch
- ”A Once-in-a-Lifetime Alignment”, Jet Propulsion Laboratory.
- Two Voyagers Taught Us How to Listen to Space, Jet Propulsion Laboratory
- “Mission Status”, Jet Propulsion Laboratory
- “Voyager at 40: Keep Reaching for the Stars”, Jet Propulsion Laboratory
Also of interest | 0.867649 | 3.467957 |
Sunset or sundown, is the daily disappearance of the Sun below the western horizon as a result of Earth’s rotation.
The time of sunset is defined in astronomy as the moment when the trailing edge of the Sun’s disk disappears below the horizon. Near to the horizon, atmospheric refraction causes the ray path of light from the Sun to be distorted to such an extent that geometrically the Sun’s disk is already about one diameter below the horizon when sunset is observed.
The spinning Earth lit by the Sun as seen from far above the North Pole. All along the terminator, the rays from the sun hit Earth horizontally, neglecting any atmospheric effects and Earth’s orbital motion.
Sunset is distinct from dusk, which is the time when the sky becomes completely dark (apart from artificial light). This occurs when the Sun is about 18 degrees below the horizon. The period between sunset and dusk is called twilight.
Locations north of the Arctic Circle and south of the Antarctic Circle experience no sunset or sunrise on at least one day of the year, when the polar day or the polar night persists continuously for 24 hours.
Sunset creates unique atmospheric conditions such as the often intense orange and red colors of the Sun and the surrounding sky.
The time of sunset varies throughout the year, and is determined by the viewer’s position on Earth, specified by longitude and latitude, and elevation. Small daily changes and noticeable semi-annual changes in the timing of sunsets are driven by the axial tilt of Earth, daily rotation of the Earth, the planet’s movement in its annual elliptical orbit around the Sun, and the Earth and Moon’s paired revolutions around each other. During winter and spring, the days get longer and sunsets occur later every day until the day of the latest sunset, which occurs after the summer solstice. In the Northern Hemisphere, the latest sunset occurs late in June or in early July, but not on the summer solstice of June 21. This date depends on the viewer’s latitude (connected with the Earth’s slower movement around the aphelion around July 4). Likewise, the earliest sunset does not occur on the winter solstice, but rather about two weeks earlier, again depending on the viewer’s latitude. In the Northern Hemisphere, it occurs in early December or late November (influenced by the Earth’s faster movement near its perihelion, which occurs around January 3).
Likewise, the same phenomenon exists in the Southern Hemisphere, but with the respective dates reversed, with the earliest sunsets occurring some time before June 21 in winter, and latest sunsets occurring some time after December 21 in summer, again depending on one’s southern latitude. For a few weeks surrounding both solstices, both sunrise and sunset get slightly later each day. Even on the equator, sunrise and sunset shift several minutes back and forth through the year, along with solar noon. These effects are plotted by an analemma.
Neglecting atmospheric refraction and the Sun’s non-zero size, whenever and wherever sunset occurs, it is always in the northwest quadrant from the March equinox to the September equinox, and in the southwest quadrant from the September equinox to the March equinox. Sunsets occur almost exactly due west on the equinoxes for all viewers on Earth. Exact calculations of the azimuths of sunset on other dates are complex, but they can be estimated with reasonable accuracy by using the analemma.
As sunrise and sunset are calculated from the leading and trailing edges of the Sun, respectively, and not the center, the duration of a day time is slightly longer than night time (by about 10 minutes, as seen from temperate latitudes). Further, because the light from the Sun is refracted as it passes through the Earth’s atmosphere, the Sun is still visible after it is geometrically below the horizon. Refraction also affects the apparent shape of the Sun when it is very close to the horizon. It makes things appear higher in the sky than they really are. Light from the bottom edge of the Sun’s disk is refracted more than light from the top, since refraction increases as the angle of elevation decreases. This raises the apparent position of the bottom edge more than the top, reducing the apparent height of the solar disk. Its width is unaltered, so the disk appears wider than it is high. (In reality, the Sun is almost exactly spherical.) The Sun also appears larger on the horizon, an optical illusion, similar to the moon illusion.
Locations north of the Arctic Circle and south of the Antarctic Circle experience no sunset or sunrise at least one day of the year, when the polar day or the polar night persist continuously for 24 hours. | 0.852213 | 3.990085 |
The fifth planet from the sun is a
huge ball of gas so massive it could hold all the other planets put together. What we can see of the
planet are bands of the highest clouds in a thick atmosphere of hydrogen and helium. Traces of
other gases produce the bright bands of color.
The Red Spot
Jupiter's most familiar feature is
swirling mass of clouds that are higher and cooler than surrounding ones. Called the Great
Red Spot, it has been likened to a great
hurricane and is caused by tremendous winds that develop above the rapidly spinning planet. Winds blow counterclockwise
around this disturbance at about 250
miles per hour. Hurricanes on Earth rarely generate winds over 180 miles an hour.
The Red Spot is twice the size of
Earth and has been raging for at least 300 years. It is one of several storms on Jupiter.
At Jupiter's center is a core of
rock many times the mass of Earth. But the bulk of the planet is a thick gaseous murk that
appears smeared through a telescope because
the planet moves so rapidly beneath. Jupiter's rapid rotation causes it to bulge, making the diameter 7 percent greater
at the equator than at the poles.
Jupiter has thin, barely perceptible
rings and at least 16 satellites. The four largest-- Io, Europa, Ganymede and Callisto --
are called the Galilean moons.
They orbit in the same plane and are
all visible in a telescope.
Jupiter: ruler of
the roman gods, also jove
Jupiter was believed by
Mesopotamians to be a wandering star placed in the heavens by a god to watch over the night sky.
In 1610, Galileo Galilei used a 20x telescope
to observe three "stars" around Jupiter. Over several nights he observed these "stars," but each
night they were in different positions, leading to his conclusion that they were bodies orbiting
the giant planet.
In 1994, astronomers around the
world watched as the fragments of comet Shoemaker-Levy
9 struck Jupiter -- an event that had been forecast. This image shows a bright cloud more than 8,600 miles in
diameter caused by the impact.
You could stuff 1,300 Earths into
подготовки данной работы были использованы материалы с сайта http://englishtopic.narod.ru/ | 0.847698 | 3.229213 |
SOFIA flies during the day with the door to its main instrument open.
(Image: © NASA/Jim Ross)
NASA’s Stratospheric Observatory For Infrared Astronomy (SOFIA) is a stargazing platform unlike any other.
SOFIA observes nebulae and galaxies in a variety of “colors” of infrared light. It may not boast as large a mirror as some of its ground-based relatives, and it doesn’t enjoy the complete freedom from Earth’s atmosphere that the Spitzer Space Telescope does, but SOFIA’s ability to capture a wide range of wavelengths and distinguish between fine shades of colors make it an observatory unrivaled in the astronomical world. The fact that SOFIA lives on an airplane also makes it pretty remarkable, as it has made observations from above a dozen countries spanning both hemispheres.
“This observatory allows us access to a part of the universe that otherwise we cannot study from any other facility,” said Naseem Rangwala, an astrophysicist at NASA Ames Research Center and principal investigator of the SOFIA observing program.
SOFIA in the sky
Taking over from the Kuiper Airborne Observatory, NASA’s previous high-flying infrared eye, SOFIA has been watching the skies since 2010 and is scheduled to operate until the early 2030s. The observatory takes the form of a compact Boeing 747, retrofitted specifically for this purpose. The aircraft makes about four flights each week, cruising for 10 hours at a time between 40,000 and 44,000 feet (12,000 and 13,000 meters), putting it above more than 99% of the infrared-scattering water vapor in Earth’s atmosphere. For most of the year SOFIA operates from California, but it also makes trips to New Zealand for Southern Hemisphere stargazing, as well as to Germany, whose space agency developed three of the platform’s eight instruments.
A large door toward the rear of the craft opens to reveal a 8.9-foot (2.7 m), nearly 20-ton mirror, which swivels nimbly to maintain a fixed lock on its celestial marks while the plane bobs and vibrates.
“One of the things I like best is just watching the telescope,” said Michael Person, a planetary scientist at the Massachusetts Institute of Technology who uses SOFIA to study planetary atmospheres. “Eventually you realize the telescope is perfectly still as it must be to be pointing at the target, and it’s the plane and you and everything else that’s jostling and moving around.”
Seats have been stripped from the main cabin to transform it into a control room, with table-mounted consoles for instrument operators, data analysts and visiting scientists. The flight crew and navigators hang out on an upper level, and the front of the plane retains its seats for takeoff, landing and enjoying the view. “In the Southern Hemisphere, you get to see the lights of the aurora,” Rangwala said. “It’s an amazing experience.”
What makes SOFIA special
Portable, cutting-edge observatories don’t come cheap. SOFIA cost $85.2 million to run in 2017, putting it close to the Hubble Space Telescope as one of NASA’s priciest programs (although DLR, the German space agency, shoulders 20% of SOFIA’s cost). But the missions the telescopes work on couldn’t be more different.
Once a telescope arrives in space, that’s typically the end of its development. SOFIA, however, which returns to the ground every day, can add new instruments and upgrade old ones without launching a single rocket.
In 2015, the German Aerospace Center upgraded its German Receiver for Astronomy at Terahertz Frequencies (GREAT) instrument aboard SOFIA. With the new hardware, researchers were able to identify in deep space molecules of helium hydride — the type of molecules long thought to have participated in the universe’s earliest chemical reactions. “This molecule was predicted by theorists for decades,” Rangwala said. “We finally found it.”
Then last year SOFIA’s High-Resolution Airborne Wideband Camera Plus (HAWC ) came online, allowing researchers to image magnetic fields and study the role they play in star creation.
Another unique characteristic of SOFIA is its range. Some telescopes specialize in a few particular colors of infrared light. Others, like the upcoming James Webb Space Telescope, are powerful but narrowly focused on a small spot of space. SOFIA, however, can do it all. Its instruments span much of the infrared spectrum from a few microns to hundreds. Stars burn brightly enough to emit visible light, but in this other swath of the spectrum SOFIA can pick out dimmer, cooler objects from galaxies to nebulae to dust clouds, similar to how infrared goggles can discern people and animals at night. The telescope can also tell one shade from another with rare precision — an important ability for spotting the fingerprints of individual molecules.
SOFIA’s scientific contributions
The astronomical community has fully embraced the platform’s unique résumé of skills. For instance, Michael Person, a research scientist at MIT, used SOFIA to observe Pluto in the summer of 2015. He and his colleagues have been studying the dwarf planet’s atmosphere for 20 years through an eclipse-like phenomenon called occultation — when Pluto moves in front of a star, casting a shadow out into space. At that moment, starlight passes through Pluto’s atmosphere, and any telescope that finds itself in Pluto’s diminutive shadow can extract some information about the gases that surround the dwarf planet.
Most occultation shadows fall over the ocean, though, and even if they don’t, their path across the Earth is tough to predict. But SOFIA can overcome both of those challenges. In June of 2015, Person found himself on board the aircraft, fielding calls from MIT with final predictions and updating the navigators, who tweaked the flight plan in real time to chase Pluto’s shadow across the Pacific Ocean. “At the last minute we can reposition [SOFIA] in a way you can’t just quickly move a telescope on the ground,” Person said.
The team’s improvising paid off. By observing Pluto’s atmosphere in two colors, they were able to help settle a long-standing debate about whether the dwarf planet’s fuzziness indicated haze or heat. Two weeks later, the New Horizons probe flew by Pluto and confirmed their findings: Pluto was hazy. “It was basically the ideal experiment,” Person said.
Recently, SOFIA has embarked on two legacy programs — both require observations spanning many hours. One aims to study groups of stars of different sizes to determine whether their bubbles and shockwaves make it easier or harder for other stars to form nearby.
The other is targeting a large tract of the center of the Milky Way about the size of four full moons. Despite an abundance of star ingredients, something seems to be stopping stellar birth in this region, and researchers hope more detailed images will help them figure out what.
Even as the more powerful James Webb Space Telescope comes online, Rangwala emphasized that SOFIA’s complementary nature will make it an even more valuable part of NASA’s fleet of astronomical hardware. Such sweeping maps of the Milky Way will be essential for helping the much more narrowly focused space telescope get its bearings, she said. “If the [JWST] wants to know where to point, [SOFIA] will be one of the most precise instruments for pointing.”
Have a news tip, correction or comment? Let us know at [email protected]. | 0.835944 | 3.709011 |
Exploring a new world is always a lot more interesting than the business of getting there. Each destination is different, after all Mars isn't Jupiter which isn't Enceladus which isn't the sun. But as for the spaceships themselves? No so much that's unfamiliar: a collection of engines and thrusters and instruments and a lot of explosive fuel.
That, at least, has been the rule. But that rule has changed thanks to the Dawn spacecraft. You may never have heard of Dawn, and if you haven't, you're not alone. In a solar system full of dazzling bodies, its destination is nothing more glamorous than an asteroid two of them, actually. And as a descendant of a long line of spacecraft designed to fly very, very fast, Dawn flies very, very slowly or at least it accelerates that way. But that very pokiness is part of its genius, and the dazzling new stream of pictures and other data now pouring back from the first half of Dawn's journey is proving that the NASA engineers knew just what they were doing.
Dawn was launched in 2007, on a slow journey to the asteroid Vesta and later, to its bigger sister Ceres. Vesta is the second largest body in the asteroid belt about 360 mi. (578 km) across, or roughly the size of Arizona. When the Delta rocket that blasted Dawn into space and then out of Earth orbit was spent and discarded, the craft was moving at an impressive 25,000 mph (40,000 k/h) clip fast, certainly, but more speed still would be needed to get the ship out to the asteroid belt, into orbit around Vesta, then out of orbit and onto Ceres. All that flying and maneuvering takes a lot of fuel, which can add weight and drive up mission costs.
The answer: replace chemical fuel with light xenon gas about 270 liters of it, which is small by spacecraft standards and then use that fuel very sparingly. The key to that was ion propulsion technology, which is just as cool as it sounds. Two large solar panels, measuring 65 ft. (19.7 m) from one tip to the other, gather power from the sun and then ionize the xenon, accelerating it through the engine's exhaust and providing thrust. Any old noble gas would do for this job helium, neon, argon, krypton but the xenon ion is the most massive of the group, as atoms go, and thus creates more thrust.
Of course, just as "massive" is a relative term, so is "more thrust." The stream of xenon ions coming from the engine bell produces a thrust of just 91 millinewtons, or about the force a piece of paper exerts on your hand when you pick it up. That's a little bit shy of, say, the 7.5 million lbs. (3.4 million kg) of thrust the Saturn V produced when it blasted off the pad.
But physics plays a long game. Not only is ion propulsion economical, burning less than 3 milligram (.0001 oz) of fuel per second, the featherweight thrust it produces is cumulative. The engine burns more or less constantly on its outward trip stopping only for eight hrs. once a week so that the ship's main antenna can be aligned toward Earth for a status report. Still, even such constant thrusting adds only 15 mph (24 k/h) per day, or zero to 60 in four days, not exactly flooring it. Over the course of 67 days, however, that adds up to an additional 1,000 mph. That's a lot in a journey through the solar system, since spacecraft don't typically make a straightahead, as-the-crow-flies trip to a destination, but rather go into orbit around the sun and then gently add velocity so they spiral out to where they're going.
"Over the course of years we sculpted the orbit," says Marc Rayman Dawn's chief engineer and mission director. "By the time we got to Vesta we were essentially in the same orbit as the asteroid, approaching it at a relative speed of 60 mph."
That was back in August, when Rayman's team tweaked the ion thrusters so that the spacecraft could descend into orbit around the asteroid. Dawn is now barnstorming Vesta, flying at a very low altitude of 130 mi. (210 km) and the images it's returned have been suitably extraordinary revealing bright surface material splattered around craters from long ago meteor strikes, and less-disturbed stretches of more pristine landscape. This provides clues to the asteroid's interior and about the primal forces that shaped it 4.5 billion years ago.
"One of the things that's cool about Dawn is that we're exploring uncharted worlds," says Rayman. "We say that Vesta has a diameter that's roughly equivalent to Arizona's, but remember it's a three dimensional body and we're orbiting it. So overall we're studying an area twice the size of California."
And compared to the next destination, even that's small. Ceres, the largest object in the asteroid belt, is 590 mi. (950 km) across and should have an even more variegated surface. Dawn will arrive there in Feb. of 2015 and spend 5 months studying the asteroid up close. By then, the mission is scheduled to be bought to a close, its funding if not the spacecraft's fuel expended. Whatever Dawn discovers about Ceres and Vesta, however, it's already proven the larger point that after half a century of blast-and-go spacecraft, we now have a second decidedly more elegant way to get around. | 0.852288 | 3.599717 |
Published on Dec 15, 2018
This weekend, the comet known as 46P/Wirtanen will make one of the 10 closest comet flybys of Earth in 70 years, and you may even be able to see it without a telescope. Comet Wirtanen has already been visible in small amateur telescopes, binoculars and cameras. At the moment it is glowing like a 4th magnitude star, barely visible to the unaided eye. On the nights of closest approach, 46P/Wirtanen can be found in the constellation Taurus. A good time to look is just before midnight when the Bull is climbing high in the southern sky. http://spaceweather.com/ http://spaceweather.com/archive.php?v... Clear Skies Everyone! Although the approach will be a distant 7.1 million miles (11.4 million kilometers, or 30 lunar distances) from Earth, it's still a fairly rare opportunity. "This will be the closest comet Wirtanen has come to Earth for centuries and the closest it will come to Earth for centuries," said Paul Chodas, manager of the Center for Near-Earth Object Studies at NASA's Jet Propulsion Laboratory in Pasadena, California. What's more, Chodas said, "This could be one of the brightest comets in years, offering astronomers an important opportunity to study a comet up close with ground-based telescopes, both optical and radar." NASA-sponsored ground, air and space-based observatories getting in on the action include NASA's Goldstone Solar System Radar in California; the NASA Infrared Telescope Facility on Maunakea, Hawaii; the Hubble, Chandra, Swift and Spitzer space telescopes; and an airborne observatory known as the Stratospheric Observatory for Infrared Astronomy (SOFIA). The comet will even pass through the observing field of the Transiting Exoplanet Survey Satellite (TESS). https://www.nasa.gov/feature/jpl/see-... http://wirtanen.astro.umd.edu/46P/46P... http://wirtanen.astro.umd.edu/46P/46P... http://wirtanen.astro.umd.edu/46P/46P... | 0.90636 | 3.021971 |
Our own galaxy is on a collision course with Andromeda. Will it hurt?
No, the stars (and planets orbiting) residing in each galaxy are too far from each other to collide or really interact in any way. Perhaps in the inner regions of the galaxies (around the central nucleus) some may disturb one another to a great extent, but out were Sol resides between spiral arms there is no danger from collisions. Only the interstellar dust and gas from both galaxies would collide, resulting in some spectacular light-works or even nova. This would take place over thousands of years.
Define "hurt". The galaxies themselves will be shredded by gravitational interactions before recoalescing into an elliptical, but the individual stars and planets will mostly survive intact. There will be a huge burst of star formation that will increase the chances of being in close proximity when supernovae take place, and some star systems may be ejected into intergalactic space (Which would be a lousy place for a civilization to find itself, bad enough when stars are "just" a few light-years apart, try interstellar travel when the nearest star is hundreds of light-years away.), some might get thrown into the central supermassive black holes at the center of each galaxy. Infalling material will trigger a quasar outburst from the central sbh which would fry any systems in the path of the jets. As far as Humanity and Earth goes, the Sun will be its death throes by then so it's a moot point anyway. Either we have the technology to avoid danger or we'll be long, long extinct.
Recent data suggests that the Milky way is more massive than Andromeda, which previously(to my knowledge) it had been Milky way was larger while Andromeda was more massive. Collisions between stars are extremely unlikely, though are possible . And obviously the super-massive black-holes will eventually collide. Some simulations show we will become an elliptical galaxy whiles others show we will remain a disk galaxy with new arms and trails as some systems are thrown either out of the galaxy system(s) or thrown on extreme elliptical orbits extending out towards the equivalent of a galactic "ort cloud" before beginning their journey back.
I think you have the basic mechanisms correct. The way the natural systems play out. This is a science fiction and futurism forum so there is no need for natural.
The collision with Andromeda is likely to be slightly before the red giant branch phase, 4 billion vs 5 billion years. Earth would depopulate in around 1.1 billion years if there is no sunshade or moving of the planet.
The red giant branch (RGB) and asymptotic giant branch (AGB) phases of the Sun will be its most energetic. The scale of the Dyson Sphere will increase by 3 orders of magnitude. The RGB stage will last over a billion years. AGB stars eject large parts of their mass naturally. Starlifting becomes much easier. Some people like the idea of starlifting before entering the RGB. In that case the timing would change. If the Sun should eject around 0.4 to 0.5 solar masses of material.
This is not a bad thing for a civilization trying to colonize other galaxies. For a K0 civilization like us now it would be fatal. Kind of like the frog launched by NASA in 2013. For an organized K3 it is an ideal propulsion system. You guide stars through a gravitational keyhole where the tidal force is lower than the surface gravity.
I assume by "system" you mean a planet in solar system like Earth is. The jets are ionized material so they should respond to magnetic field. Of course Earth and the Sun's magnetic field would be overwhelmed a long distance from an active galactic nucleus. We can do much stronger magnetic fields. Allowing a huge supply of energy and momentum to fly into deep space unused would seam wasteful.
A K3 civilization could avoid that. The big collision cannot be avoided but passing stars can kick each other towards assigned destinations. If you line stars up for direct impact you can change course by shifting over 1 solar radii. I am not sure if elliptical are a good or bad development though.
Either way it is an opportunity to rearrange everything. The Dyson spheres around stars or free flying swarms can ram scoop the interstellar medium. Loose stars can be gathered into clusters. Clusters that are becoming too dense can use passing stars to energize their cores. Binary system can use passing stars to boost orbital distance.
High velocity direct collisions almost never happen naturally outside of dense clusters. Astronomers disregard that possibility and assume all mergers spiral down. If we can aim the stars all options are open. Imagine a white dwarf star on a hyperbolic orbit that passing through the radiative zone of the Sun. The white dwarf should helium flash on the way through.
I have uncovered some new information on this event that might interest all of you. According to new calculations based on data pulled by the famous GAIA satellite, the Milky Way/Andromeda collision will occur in 'only' 3.9 billion years, instead of the long-touted 4.5 billion years. You can read more about this newest revelation HERE.
Not to be a buzz kill, but this sounds wrong. Quasars are indeed dangerous to biology, but much like supernova, one would need to be fairly close to a planet with life in order to seriously affect it. A danger-radius of about 10000 light years sound about right for a quasar. In any case, this is a moot point, since although the new, and lamely-named Milkdromeda galaxy that is the result of this collision may in fact produce a quasar - this is nothing new. The Milky Way last became a quasar ~6 million years ago, and we're still here to tell the tale (literally, early man may have seen the quasar when it occurred). The bottom line is that a planet with life would need to be in the galactic-core region to be seriously damaged.
6 million years ago, which is essentially a split second ago on astronomical time scales, the earth was/is in a nice quiet part of a barred spiral galaxy. Humans (or our ancestors) were limited to the planet earth. When the Milky Way and Andromeda collide what ever life that descends from us may populate every nook and cranny of our galaxy. The collision will destroy this nice barred spiral and for a time what galaxy exists will be quite irregular. A quasar going off in barred spiral isn't going to hit much because its going to be pointed 90 degrees away from the galactic plane. A quasar(possibly two quasars for a time), going off in an irregular galaxy that is almost entirely populated with life could easily blow off the atmosphere someone's planet.
Again, I must point out that distance is a key factor here. A quasar going off won't saturate the entire galaxy with deadly radiation when it goes off, whether or not the surrounding stars are in an irregular galaxy. The core regions would be the most effected, and as of yet we don't know whether or not those places can support life. Also, the assumption here was that the galaxy was not filled to the brim with life. If it were, than the game is very different. If intelligent life has colonized every part of the galaxy, then it has had plenty of time to prepare for the looming quasar event and/or prevent it from happening (if they are advanced enough). | 0.858071 | 3.701762 |
“nightynight, sleep tight, don’t let the thought that your smaller than a speck of dust on billion mile beach concern you”
Astronomers have discovered that the black holes at the center of some galaxies are strangely aligned with other black holes across billions of light years in distance. The remarkable discovery implies the makings of an interstellar cosmic web. If true, the revelation could reveal many secrets of the universe.
gee, as i’ve said for decades, any true singularity (ie, Einsteinian “zero size, infinite mass”, not the “of course everything goes around the Earth, this new bit we just made up this arvo to add to our math proves it” “quantum”) “IS” every other true singularity, in the way that every matched resonant quartz crystal is “the same” as every other matched resonant quartz crystal, true singularities “link” because they are all “at the same place”, ie, as deep into the space-time fabric as they can possibly be, they ARE the “meniscus” of “light-speed as zero”, the “needle-point” at the end of the space/time “thread” of matter & energy…
or, to elaborate a little, a true singularity (“black hole”) of zero size & infinite mass is still inclusive of the inverse square law of gravity, ie, if you are measuring matter that you claim is travelling at light speed (neutrinos etc for example) & you are get readings of less than infinite mass &/or greater than zero size, then your “ug have rock, ug brain surgeon” measuring equipment is innaccurate & you are merely measuring the object’s event horizon or (more likely) an even further from gravitational center area, also, as that body’s infinite mass means that gravitational acceleration (eg, Earth gravity, 9.8 meters per second squared) is actually getting closer to light speed the closer any approaching matter “falling” towards it is, therefore meaning that any matter in its vicinity is also “gaining mass” as it nears that true singularity’s event horizon/gravitational effect zone, thus increasing the apparent “size” of that effect zone, as each “nearing infinite mass” particle then affects any other matter out from its own increasing mass, then that matter increases mass also as the apparent “event horizon” or “hawking radiation” area expands exponentially via that same inverse square law, like a shell of matter becoming energy, but gaining mass interim to that point where it enters the “near” light speed, “near” infinite mass “exo-gravity” event horizon “expansion” #dothemath
“ps, don’t take newton too seriously though, Einstein covers it much better, just that newton is “dumbed down” enough for y’all”
of course one “down” side (see what i did there) to a true singularity causing any matter approaching it to accelerate towards light speed & hence increase in gravitational mass is that those particles then also gravitationally affect other particles around them in the same way, ie, as if a train picked up every carriage it passed from every line & siding along the way but whilst still accelerating, ie, a hyperbolic exponential of mass increase, volume decrease, & the result that the entire proximity then becomes part of that true singularity, as the inverse square of all the slightly below lightspeed, slightly above zero size particles still has perceptible range in a cumulative fashion, until everything is “back” in one zero sized place, at “zero” (ie, “light”) speed & thus capaple of broaching the “meniscus” & exit Einsteinien space-time to re-become the “tachyon” in its exoverse environment, possibly causing a “twang-back”, possibly not (& thus requiring the next “multiverse” to be “stitched” from scratch as mentioned.), & i mean EVERYTHING, the total collapse of everything in your sphere of existance into a zero sized point. &, theoretically, depending on any potential “critical mass” effect, could happen anywhere between now, lunchtime thursday, or a billion & a half years, ie, impossible to ascertain with current technology’s “ug have rock, ug brain surgeon” “tools”.
ok, now, let’s rev it up some, step back & look at the universe as you see it, then picture all those galaxies as “ameboids”, or even as “cells” in an organism so huge you can only see the tiny bit of its “bloodstream” that you’re entire galaxy is a mere virus or amoeba or corpuscle or whatever in, & that ALL the “expansion” of that universe is no more than those constituent “micro-organisms” fleeing from an INTENSELY “hungry” true singularity at the “center” (ie, as deep in the lightspeed “meniscus” as is possible, the ABSOLUTE “down” of this space-time continuum) in at least a survival mode reflex (think of nerve cells “retreating” from painfull stimulii such as fire, ice etc, or of insects, animals etc, fleeing areas before earthquakes), or even an intelligent manner (if a tiny amount of chemical, electrical & subatomic interactions such as your chimp selves can consider itself remotely sentient then how much greater would be the possible intellect of all those same components at galactic size), in which case, uh, you might have cause for concern somewhat sooner, because if you’re actively destroying a part of that creature’s bio-system, with your continued “static” from ripping & bombing your Planet to pieces to rip out its electrically conductive veins etc, you may be noticeably slowing down its escape, & as with any fox with its leg in a hindering trap might chew its own leg off before the trapper arrives, or any organism with a disease will rally its antibodies, it could sacrifice the area causing that disruptive & detrimental to its survival in a number of ways, anything actually from bombardment with rocks to exploding your sun, you just can’t really tell with anything that “different”… nightynight, sleep tight, don’t let the thought that your smaller than a speck of dust on billion mile beach concern you.
Newton’s law of gravity describes a force that decreases with the SQUARE of the distance. | 0.828371 | 3.810903 |
F. González-Galindo, F. Forget, M. Angelats I Coll, and M. A. López-Valverde. The Martian upper atmosphere. Lecture Notes and Essays in Astrophysics, 3:151-162, 2008. [ bib | ADS link ]
The most relevant aspects of the Martian atmosphere are presented in this paper, focusing on the almost unexplored upper atmosphere. We summarize the most recent observations concerning this region, as well as the numerical models used to its study. Special attention is devoted to the only ground-to-exosphere General Circulation Model existing today for Mars, the LMD-MGCM. The model and its extension to the thermosphere are described and the strategies used for its validation are shortly discussed. Finally, we briefly present some comparisons between the results of the model and the observations by different spacecrafts.
J. L. Fastook, J. W. Head, D. R. Marchant, and F. Forget. Tropical mountain glaciers on Mars: Altitude-dependence of ice accumulation, accumulation conditions, formation times, glacier dynamics, and implications for planetary spin-axis/orbital history. Icarus, 198:305-317, 2008. [ bib | DOI | ADS link ]
Fan-shaped deposits up to 166,000 km in area are found on the northwest flanks of the huge Tharsis Montes volcanoes in the tropics of Mars. Recent spacecraft data have confirmed earlier hypotheses that these lobate deposits are glacial in origin. Increased knowledge of polar-latitude terrestrial glacial analogs in the Antarctic Dry Valleys has been used to show that the lobate deposits are the remnants of cold-based glaciers that formed in the extremely cold, hyper-arid climate of Mars. Mars atmospheric general circulation models (GCM) show that these glaciers could form during periods of high obliquity when upwelling and adiabatic cooling of moist air favor deposition of snow on the northwest flanks of the Tharsis Montes. We present a simulation of the Tharsis Montes ice sheets produced by a static accumulation pattern based on the GCM results and compare this with the nature and extent of the geologic deposits. We use the fundamental differences between the atmospheric snow accumulation environments (mass balance) on Earth and Mars, geological observations and ice-sheet models to show that two equilibrium lines should characterize ice-sheet mass balance on Mars, and that glacial accumulation should be favored on the flanks of large volcanoes, not on their summits as seen on Earth. Predicted accumulation rates from such a parameterization, together with sample spin-axis obliquity histories, are used to show that obliquity in excess of 45deg and multiple 120,000 year obliquity cycles are necessary to produce the observed deposits. Our results indicate that the formation of these deposits required multiple successive stages of advance and retreat before their full extent could be reached, and thus imply that spin-axis obliquity remained at these high values for millions of years during the Late Amazonian period of Mars history. Spin-axis obliquity is one of the main factors in the distribution and intensity of solar insolation, and thus in determining the climate history of Mars. Unfortunately, reconstruction of past climate history is inhibited by the fact that the chaotic nature of the solution makes the calculation of orbital histories unreliable prior to about 20 Ma ago. We show, however, that the geological record, combined with glacial modeling, can be used to provide insight into the nature of the spin-axis/orbital history of Mars in the Late Amazonian, and to begin to establish data points for the geologically based reconstruction of the climate and orbital history of Mars.
A. Crespin, S. Lebonnois, S. Vinatier, B. Bézard, A. Coustenis, N. A. Teanby, R. K. Achterberg, P. Rannou, and F. Hourdin. Diagnostics of Titan's stratospheric dynamics using Cassini/CIRS data and the 2-dimensional IPSL circulation model. Icarus, 197:556-571, 2008. [ bib | DOI | ADS link ]
The dynamics of Titan's stratosphere is discussed in this study, based on a comparison between observations by the CIRS instrument on board the Cassini spacecraft, and results of the 2-dimensional circulation model developed at the Institute Pierre-Simon Laplace, available at http://www.lmd.jussieu.fr/titanDbase [Rannou, P., Lebonnois, S., Hourdin, F., Luz, D., 2005. Adv. Space Res. 36, 2194-2198]. The comparison aims at both evaluating the model's capabilities and interpreting the observations concerning: (1) dynamical and thermal structure using temperature retrievals from Cassini/CIRS and the vertical profile of zonal wind at the Huygens landing site obtained by Huygens/DWE; and (2) vertical and latitudinal profiles of stratospheric gases deduced from Cassini/CIRS data. The modeled thermal structure is similar to that inferred from observations (Cassini/CIRS and Earth-based observations). However, the upper stratosphere (above 0.05 mbar) is systematically too hot in the 2D-CM, and therefore the stratopause region is not well represented. This bias may be related to the haze structure and to misrepresented radiative effects in this region, such as the cooling effect of hydrogen cyanide (HCN). The 2D-CM produces a strong atmospheric superrotation, with zonal winds reaching 200 m s -1 at high winter latitudes between 200 and 300 km altitude (0.1-1 mbar). The modeled zonal winds are in good agreement with retrieved wind fields from occultation observations, Cassini/CIRS and Huygens/DWE. Changes to the thermal structure are coupled to changes in the meridional circulation and polar vortex extension, and therefore affect chemical distributions, especially in winter polar regions. When a higher altitude haze production source is used, the resulting modeled meridional circulation is weaker and the vertical and horizontal mixing due to the polar vortex is less extended in latitude. There is an overall good agreement between modeled chemical distributions and observations in equatorial regions. The difference in observed vertical gradients of C 2H 2 and HCN may be an indicator of the relative strength of circulation and chemical loss of HCN. The negative vertical gradient of ethylene in the low stratosphere at 15deg S, cannot be modeled with simple 1-dimensional models, where a strong photochemical sink in the middle stratosphere would be necessary. It is explained here by dynamical advection from the winter pole towards the equator in the low stratosphere and by the fact that ethylene does not condense. Near the winter pole (80deg N), some compounds (C 4H 2, C 3H 4) exhibit an (interior) minimum in the observed abundance vertical profiles, whereas 2D-CM profiles are well mixed all along the atmospheric column. This minimum can be a diagnostic of the strength of the meridional circulation, and of the spatial extension of the winter polar vortex where strong descending motions are present. In the summer hemisphere, observed stratospheric abundances are uniform in latitude, whereas the model maintains a residual enrichment over the summer pole from the spring cell due to a secondary meridional overturning between 1 and 50 mbar, at latitudes south of 40-50deg S. The strength, as well as spatial and temporal extensions of this structure are a difficulty, that may be linked to possible misrepresentation of horizontally mixing processes, due to the restricted 2-dimensional nature of the model. This restriction should also be kept in mind as a possible source of other discrepancies.
M. Giuranna, D. Grassi, V. Formisano, L. Montabone, F. Forget, and L. Zasova. PFS/MEX observations of the condensing CO 2 south polar cap of Mars. Icarus, 197:386-402, 2008. [ bib | DOI | ADS link ]
The condensing CO 2 south polar cap of Mars and the mechanisms of the CO 2 ice accumulation have been studied through the analysis of spectra acquired by the Planetary Fourier Spectrometer (PFS) during the first two years of ESA's Mars Express (MEX) mission. This dataset spans more than half a martian year, from Ls330deg to Ls194deg, and includes the southern fall season which is found to be extremely important for the study of the residual south polar cap asymmetry. The cap expands symmetrically and with constant speed during the fall season. The maximum extension occurs sometime in the 80deg-90deg Ls range, when the cap edges are as low as -40deg latitude. Inside Hellas and Argyre basins, frost can be stable at lower latitudes due to the higher pressure values, causing the seasonal cap to be asymmetric. Within the seasonal range considered in this paper, the cap edge recession rate is approximately half the rate at which the cap edge expanded. The longitudinal asymmetries reduce during the cap retreat, and disappear around Ls145deg. Two different mechanisms are responsible for CO 2 ice accumulation during the fall season, especially in the 50deg-70deg Ls range. Here, CO 2 condensation in the atmosphere, and thus precipitation, is allowed exclusively in the western hemisphere, and particularly in the longitudinal corridor of the perennial cap. In the eastern hemisphere, the cap consists mainly of CO 2 frost deposits, as a consequence of direct vapor deposition. The differences in the nature of the surface ice deposits are the main cause for the residual south polar cap asymmetry. Results from selected PFS orbits have also been compared with the results provided by the martian general circulation model (GCM) of the Laboratoire de Météorologie dynamique (LMD) in Paris, with the aim of putting the observations in the context of the global circulation. This first attempt of cross-validation between PFS measurements and the LMD GCM on the one hand confirms the interpretation of the observations, and on the other hand shows that the climate modeling during the southern polar night on Mars is extremely sensitive to the dynamical forcing.
T. Cavalié, F. Billebaud, T. Encrenaz, M. Dobrijevic, J. Brillet, F. Forget, and E. Lellouch. Vertical temperature profile and mesospheric winds retrieval on Mars from CO ;millimeter observations. Comparison with general circulation model predictions. Astronomy Astrophysics, 489:795-809, 2008. [ bib | DOI | ADS link ]
Aims: We have recorded high spectral resolution spectra and derived precise atmospheric temperature profiles and wind velocities in the atmosphere of Mars. We have compared observations of the planetary mean thermal profile and mesospheric wind velocities on the disk, obtained with our millimetric observations of CO rotational lines, to predictions from the Laboratoire de Météorologie Dynamique (LMD) Mars General Circulation Model, as provided through the Mars Climate Database (MCD) numerical tool. <BR />Methods: We observed the atmosphere of Mars at CO(1-0) and CO(2-1) wavelengths with the IRAM 30-m antenna in June 2001 and November 2005. We retrieved the mean thermal profile of the planet from high and low spectral resolution data with an inversion method detailed here. High spectral resolution spectra were used to derive mesospheric wind velocities on the planetary disk. We also report here the use of 13CO(2-1) line core shifts to measure wind velocities at 40 km. <BR />Results: Neither the Mars Year 24 (MY24) nor the Dust Storm scenario from the Mars Climate Database (MCD) provides satisfactory fits to the 2001 and 2005 data when retrieving the thermal profiles. The Warm scenario only provides good fits for altitudes lower than 30 km. The atmosphere is warmer than predicted up to 60 km and then becomes colder. Dust loading could be the reason for this mismatch. The MCD MY24 scenario predicts a thermal inversion layer between 40 and 60 km, which is not retrieved from the high spectral resolution data. Our results are generally in agreement with other observations from 10 to 40 km in altitude, but our results obtained from the high spectral resolution spectra differ in the 40-70 km layer, where the instruments are the most sensitive. The wind velocities we retrieve from our 12CO observations confirm MCD predictions for 2001 and 2005. Velocities obtained from 13CO observations are consistent with MCD predictions in 2001, but are lower than predicted in 2005.
C. F. Wilson, S. Guerlet, P. G. J. Irwin, C. C. C. Tsang, F. W. Taylor, R. W. Carlson, P. Drossart, and G. Piccioni. Evidence for anomalous cloud particles at the poles of Venus. Journal of Geophysical Research (Planets), 113:E00B13, 2008. [ bib | DOI | ADS link ]
An analysis of near-infrared emissions on the nightside of Venus observed by the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) instrument on board Venus Express reveals anomalous cloud particles in the polar regions of Venus. These anomalous particles are found within the centers of polar vortices at both poles and are either larger or different in composition from those elsewhere in the planet. We find no persistent latitudinal variation in cloud properties at low to midlatitudes, nor do we find asymmetry between the southern and northern hemispheres. These findings arise from analysis of the relative brightness of 1.74 and 2.30 μm infrared radiation thermally emitted from the deep atmosphere of Venus. Larger cloud particles cause relatively more attenuation at 2.30 μm than at 1.74 μm, so we use a “size parameter,” m = (I 1.74mum)/(I 2.30mum)0.53, as a proxy for particle size. This methodology follows that of Carlson et al. (1993), supported by new radiative transfer modeling.
V. De La Haye, J. H. Waite, T. E. Cravens, I. P. Robertson, and S. Lebonnois. Coupled ion and neutral rotating model of Titan's upper atmosphere. Icarus, 197:110-136, 2008. [ bib | DOI | ADS link ]
A one-dimensional composition model of Titan's upper atmosphere is constructed, coupling 36 neutral species and 47 ions. Energy inputs from the Sun and from Saturn's magnetosphere and updated temperature and eddy coefficient parameters are taken into account. A rotating technique at constant latitude and varying local-time is proposed to account for the diurnal variation of solar inputs. The contributions of photodissocation, neutral chemistry, ion-neutral chemistry, and electron recombination to neutral production are presented as a function of altitude and local time. Local time-dependent mixing ratio and density profiles are presented in the context of the T and T Cassini data and are compared in detail to previous models. An independent and simplified ion and neutral scheme (19-species) is also proposed for future 3D-purposes. The model results demonstrate that a complete understanding of the chemistry of Titan's upper atmosphere requires an understanding of the coupled ion and neutral chemistry. In particular, the ionospheric chemistry makes significant contributions to production rates of several important neutral species.
A. Spiga, H. Teitelbaum, and V. Zeitlin. Identification of the sources of inertia-gravity waves in the Andes Cordillera region. Annales Geophysicae, 26:2551-2568, 2008. [ bib | DOI | ADS link ]
Four major sources of inertia-gravity waves are known in the Earth atmosphere: upper-tropospheric jet-streams, lower-tropospheric fronts, convection and topography. The Andes Cordillera region is an area where all of these major sources are potentially present. By combining ECMWF and NCEP-NCAR reanalysis, satellite and radiosoundings data and mesoscale WRF simulations in the Andes Cordillera region, we were able to identify the cases where, respectively, the jet-stream source, the convective source and the topography source are predominantly in action. We retrieve emitted wave parameters for each case, compare them, and analyse possible emission mechanisms. The WRF mesoscale model shows very good performance in reproducing the inertia-gravity waves identified in the data analysis, and assessing their likely sources.
F. Lefèvre, J.-L. Bertaux, R. T. Clancy, T. Encrenaz, K. Fast, F. Forget, S. Lebonnois, F. Montmessin, and S. Perrier. Heterogeneous chemistry in the atmosphere of Mars. Nature, 454:971-975, 2008. [ bib | DOI | ADS link ]
Hydrogen radicals are produced in the martian atmosphere by the photolysis of water vapour and subsequently initiate catalytic cycles that recycle carbon dioxide from its photolysis product carbon monoxide. These processes provide a qualitative explanation for the stability of the atmosphere of Mars, which contains 95 per cent carbon dioxide. Balancing carbon dioxide production and loss based on our current understanding of the gas-phase chemistry in the martian atmosphere has, however, proven to be difficult. Interactions between gaseous chemical species and ice cloud particles have been shown to be key factors in the loss of polar ozone observed in the Earth's stratosphere, and may significantly perturb the chemistry of the Earth's upper troposphere. Water-ice clouds are also commonly observed in the atmosphere of Mars and it has been suggested previously that heterogeneous chemistry could have an important impact on the composition of the martian atmosphere. Here we use a state-of-the-art general circulation model together with new observations of the martian ozone layer to show that model simulations that include chemical reactions occurring on ice clouds lead to much improved quantitative agreement with observed martian ozone levels in comparison with model simulations based on gas-phase chemistry alone. Ozone is readily destroyed by hydrogen radicals and is therefore a sensitive tracer of the chemistry that regulates the atmosphere of Mars. Our results suggest that heterogeneous chemistry on ice clouds plays an important role in controlling the stability and composition of the martian atmosphere.
A. Spiga and F. Forget. Fast and accurate estimation of solar irradiance on Martian slopes. Geophysical Research Letters, 35:L15201, 2008. [ bib | DOI | ADS link ]
A general parameterization is proposed in this study to calculate, in a Mars-like dusty atmosphere, the solar irradiance reaching an inclined surface, assuming the value in the horizontal case is known. Complete Monte-Carlo radiative transfer calculations, using the Ockert-Bell et al. (1997) dust optical properties, enable the validation of the method for Mars. The total shortwave flux reaching the surface is composed of three contributions: direct incoming flux, reflected flux by surrounding terrains, and scattered flux by the atmospheric dust. The main difficulty is the parameterization of the latter component. We show that the scattered flux reaching the slope can be expressed by a physically-based simple formula involving one empirical coupling matrix and two vectors accounting for the scattering properties and the geometrical settings. The final result is a computationally efficient parameterization, with an accuracy in most cases better than 5 W.m-2. Such a fast and accurate method to calculate solar irradiance on Martian slopes (should they be topographical surfaces or solar panels) is of particular interest in a wide range of applications, such as remote-sensing measurements, geological and meteorological models, and Mars exploration missions design.
A. Sánchez-Lavega, R. Hueso, G. Piccioni, P. Drossart, J. Peralta, S. Pérez-Hoyos, C. F. Wilson, F. W. Taylor, K. H. Baines, D. Luz, S. Erard, and S. Lebonnois. Variable winds on Venus mapped in three dimensions. Geophysical Research Letters, 35:L13204, 2008. [ bib | DOI | ADS link ]
We present zonal and meridional wind measurements at three altitude levels within the cloud layers of Venus from cloud tracking using images taken with the VIRTIS instrument on board Venus Express. At low latitudes, zonal winds in the Southern hemisphere are nearly constant with latitude with westward velocities of 105 ms-1 at cloud-tops (altitude ˜ 66 km) and 60-70 ms-1 at the cloud-base (altitude ˜ 47 km). At high latitudes, zonal wind speeds decrease linearly with latitude with no detectable vertical wind shear (values lower than 15 ms-1), indicating the possibility of a vertically coherent vortex structure. Meridional winds at the cloud-tops are poleward with peak speed of 10 ms-1 at 55deg S but below the cloud tops and averaged over the South hemisphere are found to be smaller than 5 ms-1. We also report the detection at subpolar latitudes of wind variability due to the solar tide.
T. Encrenaz, T. K. Greathouse, M. J. Richter, B. Bézard, T. Fouchet, F. Lefèvre, F. Montmessin, F. Forget, S. Lebonnois, and S. K. Atreya. Simultaneous mapping of H 2O and H 2O 2 on Mars from infrared high-resolution imaging spectroscopy. Icarus, 195:547-556, 2008. [ bib | DOI | ADS link ]
New maps of martian water vapor and hydrogen peroxide have been obtained in November-December 2005, using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infra Red Telescope facility (IRTF) at Mauna Kea Observatory. The solar longitude L was 332deg (end of southern summer). Data have been obtained at 1235-1243 cm -1, with a spectral resolution of 0.016 cm -1 ( R=8×10). The mean water vapor mixing ratio in the region [0deg-55deg S; 345deg-45deg W], at the evening limb, is 15050 ppm (corresponding to a column density of 8.32.8 pr-μm). The mean water vapor abundance derived from our measurements is in global overall agreement with the TES and Mars Express results, as well as the GCM models, however its spatial distribution looks different from the GCM predictions, with evidence for an enhancement at low latitudes toward the evening side. The inferred mean H 2O 2 abundance is 1510 ppb, which is significantly lower than the June 2003 result [Encrenaz, T., Bézard, B., Greathouse, T.K., Richter, M.J., Lacy, J.H., Atreya, S.K., Wong, A.S., Lebonnois, S., Lefèvre, F., Forget, F., 2004. Icarus 170, 424-429] and lower than expected from the photochemical models, taking in account the change in season. Its spatial distribution shows some similarities with the map predicted by the GCM but the discrepancy in the H 2O 2 abundance remains to be understood and modeled.
T. Encrenaz, T. Fouchet, R. Melchiorri, P. Drossart, B. Gondet, Y. Langevin, J.-P. Bibring, F. Forget, L. Maltagliati, D. Titov, and V. Formisano. A study of the Martian water vapor over Hellas using OMEGA and PFS aboard Mars Express. Astronomy Astrophysics, 484:547-553, 2008. [ bib | DOI | ADS link ]
We used the OMEGA imaging spectrometer aboard Mars Express to study the evolution of the water vapor abundance over the Hellas basin, as a function of the seasonal cycle. The H2O column density is found to range from very low values (between southern fall and winter) up to more than 15 pr-μm during southern spring and summer. The general behavior is consistent with the expected seasonal cycle of water vapor on Mars, as previously observed by TES and modeled. In particular, the maximum water vapor content is observed around the southern solstice, and is significantly less than its northern couterpart. However, there is a noticeable discrepancy around the northern spring equinox (Ls = 330-60deg), where the observed H2O column densities are significantly lower than the values predicted by the GCM. Our data show an abrupt enhancement of the water vapor column density (from 3 to 16 pr-μm) on a timescale of 3 days, for Ls = 251-254deg. Such an increase, not predicted by the GCM, was also occasionally observed by TES over Hellas during previous martian years at the same season; however, its origin remains to be understood.
T. Fouchet, S. Guerlet, D. F. Strobel, A. A. Simon-Miller, B. Bézard, and F. M. Flasar. An equatorial oscillation in Saturn's middle atmosphere. Nature, 453:200-202, 2008. [ bib | DOI | ADS link ]
The middle atmospheres of planets are driven by a combination of radiative heating and cooling, mean meridional motions, and vertically propagating waves (which originate in the deep troposphere). It is very difficult to model these effects and, therefore, observations are essential to advancing our understanding of atmospheres. The equatorial stratospheres of Earth and Jupiter oscillate quasi-periodically on timescales of about two and four years, respectively, driven by wave-induced momentum transport. On Venus and Titan, waves originating from surface-atmosphere interaction and inertial instability are thought to drive the atmosphere to rotate more rapidly than the surface (superrotation). However, the relevant wave modes have not yet been precisely identified. Here we report infrared observations showing that Saturn has an equatorial oscillation like those found on Earth and Jupiter, as well as a mid-latitude subsidence that may be associated with the equatorial motion. The latitudinal extent of Saturn's oscillation shows that it obeys the same basic physics as do those on Earth and Jupiter. Future highly resolved observations of the temperature profile together with modelling of these three different atmospheres will allow us determine the wave mode, the wavelength and the wave amplitude that lead to middle atmosphere oscillation.
Y. Sekine, S. Lebonnois, H. Imanaka, T. Matsui, E. L. O. Bakes, C. P. McKay, B. N. Khare, and S. Sugita. The role of organic haze in Titan's atmospheric chemistry. II. Effect of heterogeneous reaction to the hydrogen budget and chemical composition of the atmosphere. Icarus, 194:201-211, 2008. [ bib | DOI | ADS link ]
One of the key components controlling the chemical composition and climatology of Titan's atmosphere is the removal of reactive atomic hydrogen from the atmosphere. A proposed process of the removal of atomic hydrogen is the heterogeneous reaction with organic aerosol. In this study, we investigate the effect of heterogeneous reactions in Titan's atmospheric chemistry using new measurements of the heterogeneous reaction rate [Sekine, Y., Imanaka, H., Matsui, T., Khare, B.N., Bakes, E.L.O., McKay, C.P., Sugita, S., 2008. Icarus 194, 186-200] in a one-dimensional photochemical model. Our results indicate that 60-75% of the atomic hydrogen in the stratosphere and mesosphere are consumed by the heterogeneous reactions. This result implies that the heterogeneous reactions on the aerosol surface may predominantly remove atomic hydrogen in Titan's stratosphere and mesosphere. The results of our calculation also indicate that a low concentration of atomic hydrogen enhances the concentrations of unsaturated complex organics, such as C 4H 2 and phenyl radical, by more than two orders in magnitude around 400 km in altitude. Such an increase in unsaturated species may induce efficient haze production in Titan's mesosphere and upper stratosphere. These results imply a positive feedback mechanism in haze production in Titan's atmosphere. The increase in haze production would affect the chemical composition of the atmosphere, which might induce further haze production. Such a positive feedback could tend to dampen the loss and supply cycles of CH 4 due to an episodic CH 4 release into Titan's atmosphere.
L. Maltagliati, D. V. Titov, T. Encrenaz, R. Melchiorri, F. Forget, M. Garcia-Comas, H. U. Keller, Y. Langevin, and J.-P. Bibring. Observations of atmospheric water vapor above the Tharsis volcanoes on Mars with the OMEGA/MEx imaging spectrometer. Icarus, 194:53-64, 2008. [ bib | DOI | ADS link ]
The OMEGA imaging spectrometer onboard the Mars Express spacecraft is particularly well suited to study in detail specific regions of Mars, thanks to its high spatial resolution and its high signal-to-noise ratio. We investigate the behavior of atmospheric water vapor over the four big volcanoes located on the Tharsis plateau (Olympus, Ascraeus, Pavonis and Arsia Mons) using the 2.6 μm band, which is the strongest and most sensitive H 2O band in the OMEGA spectral range. Our data sample covers the end of MY26 and the whole MY27, with gaps only in the late northern spring and in northern autumn. The most striking result of our retrievals is the increase of water vapor mixing ratio from the valley to the summit of volcanoes. Corresponding column density is often almost constant, despite a factor of 5 decrease in air mass from the bottom to the top. This peculiar water enrichment on the volcanoes is present in 75% of the orbits in our sample. The seasonal distribution of such enrichment hints at a seasonal dependence, with a minimum during the northern summer and a maximum around the northern spring equinox. The enrichment possibly also has a diurnal trend, being the orbits with a high degree of enrichment concentrated in the early morning. However, the season and the solar time of the observations, due to the motion of the spacecraft, are correlated, then the two dependences cannot be clearly disentangled. Several orbits exhibit also spatially localized enrichment structures, usually ring- or crescent-shaped. We retrieve also the height of the saturation level over the volcanoes. The results show a strong minimum around the aphelion season, due to the low temperatures, while it raises quickly before and after this period. The enrichment is possibly generated by the local circulation characteristic of the volcano region, which can transport upslope significant quantities of water vapor. The low altitude of the saturation level during the early summer can then hinder the transport of water during this season. The influence of the coupling between atmosphere and surface, due mainly to the action of the regoliths, can also contribute partially to the observed phenomenon.
R. M. Haberle, F. Forget, A. Colaprete, J. Schaeffer, W. V. Boynton, N. J. Kelly, and M. A. Chamberlain. The effect of ground ice on the Martian seasonal CO 2 cycle. Planetary and Space Science, 56:251-255, 2008. [ bib | DOI | ADS link ]
The mostly carbon dioxide (CO 2) atmosphere of Mars condenses and sublimes in the polar regions, giving rise to the familiar waxing and waning of its polar caps. The signature of this seasonal CO 2 cycle has been detected in surface pressure measurements from the Viking and Pathfinder landers. The amount of CO 2 that condenses during fall and winter is controlled by the net polar energy loss, which is dominated by emitted infrared radiation from the cap itself. However, models of the CO 2 cycle match the surface pressure data only if the emitted radiation is artificially suppressed suggesting that they are missing a heat source. Here we show that the missing heat source is the conducted energy coming from soil that contains water ice very close to the surface. The presence of ice significantly increases the thermal conductivity of the ground such that more of the solar energy absorbed at the surface during summer is conducted downward into the ground where it is stored and released back to the surface during fall and winter thereby retarding the CO 2 condensation rate. The reduction in the condensation rate is very sensitive to the depth of the soil/ice interface, which our models suggest is about 8 cm in the Northern Hemisphere and 11 cm in the Southern Hemisphere. This is consistent with the detection of significant amounts of polar ground ice by the Mars Odyssey Gamma Ray Spectrometer and provides an independent means for assessing how close to the surface the ice must be. Our results also provide an accurate determination of the global annual mean size of the atmosphere and cap CO 2 reservoirs, which are, respectively, 6.1 and 0.9 hPa. They also indicate that general circulation models will need to account for the effect of ground ice in their simulations of the seasonal CO 2 cycle.
S. Lebonnois. The atmospheres of Mars, Venus and Titan: observed and modelled structures. Acoustical Society of America Journal, 123:3400, 2008. [ bib | DOI | ADS link ] | 0.906512 | 3.828232 |
In this photograph of the Sun, the coolest areas—the sunspots—are shown lightest The star we call the Sun lies at the centre of the Solar System, an array of objects of various sizes that move around, or orbit, it. These are: the eight major planets (in order of distance from the Sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune), their moons, dwarf planets, the asteroids, comets, meteoroids and vast amounts of gas and dust. The Sun’s massive size, compared to the rest of its family, gives it the gravitational pull that keeps all the planets and other objects in perpetual orbit.
The planets orbit the Sun in the same anticlockwise direction and in elliptical paths (oval, rather than perfectly circular). Seven of the planets, and most of their moons, all travel roughly on the same plane. Mercury is the exception: it has a slightly tilted orbit. Pluto, now classified as a dwarf planet, lies in the Kuiper Belt, a vast region beyond the orbit of Neptune, the outermost planet. Pluto's orbit is significantly more tilted and elliptical than the true planets.
The planets' orbits around the Sun are shown here as different colour paths. All the planets move in an anticlockwise direction....Read More >>The planets' orbits around the Sun are shown here as different colour paths. All the planets move in an anticlockwise direction. The extremely extended elliptical path of a comet—Halley's comet—is shown in white.This diagram shows the relative distances of the planets from the Sun.
The region between the Kuiper Belt and the Oort Cloud, called the Scattered Disc, is still almost completely unknown.
Find the answer | 0.855243 | 3.320071 |
That's what we have to say about this incredible new photo of Pluto's north pole that NASA just released:
The New Horizons spacecraft took this high-resolution shot as it approached the icy world on July 14, 2015.
We're only seeing it now because the robot has a small antenna and is speeding away from our solar system at about 32,000 mph. In fact, it could take until the end of 2016 to transmit all of the photos it took before, during, and after its fly-by.
But this photo isn't just pretty. It's revealing more weird truths about little ol' Pluto, which is technically classified as a dwarf planet — not a full-on planet, like Earth or diminutive Mercury. (Alan Stern, New Horizons' lead scientist, calls this demotion "bulls--t.")
"Pluto's north pole is criss-crossed by crazy rugged canyons and is covered in heavy methane snows," Stern told Tech Insider in an email. "The color of the snow varies from a yellowy hue near the pole to lighter grey-blue away from it."
The yellow tint on the surface (note: not NASA's highlighting) might indicate older methane snow that's been pummeled over the millennia by solar and cosmic radiation. The blue-gray color might be younger methane snow that's seen less exposure.
To see what Stern is referring to, let's zoom in to the top-left part of the north pole:
You can really start to make out those crazy canyons, craters, plateaus, and shades of radiation-blasted methane snow.
In fact, NASA says these kinds of features are so unusual they are "not seen elsewhere on Pluto."
The space agency provided this highlighted version to mark a few things they see as rather odd:
The green squiggly lines to the east and the west of Pluto's north pole are narrow canyons. That yellow patch is a very large canyon, at 45 miles wide, with a "winding valley" running through the middle (shown in blue).
NASA notes the walls of these gullies are very crumbled and degraded, which suggests they're incredibly ancient — unlike many larger patches of Pluto, which are "younger" and thought to be about 10 million years old. (NASA hasn't yet estimated how old the features are that it highlighted.)
Contrast that to the Grand Canyon, a geologic feature on a very dynamic planet (aka Earth) that is somewhere between 6 million and 70 million years old.
So what does it all mean?
Primarily, that Pluto is getting weirder with each new photo scientists glimpse.
For one, it has a strange mix of very ancient and also very young features. Second, it's not some static frozen ice ball; it was and possibly still is a very active, dynamic place. The canyons, for example, may have been formed by tectonic plate-like movement millions of years ago.
There's also this, Stern wrote: "Buried in those polar images are bound to be clues to Pluto's past climates!" Basically, Pluto may have also had a very busy atmosphere — even though its very thin and wispy right now.
That's pretty dynamic for a tiny planet that's minus-387 degrees Celsius and has no running water or other liquid.
We can't wait to see what else New Horizons' photos of Pluto reveal as they're beamed back to Earth.
And we're also looking forward to the spacecraft's next never-before-visited target: a tiny frozen rock in the Kuiper Belt called 2014 MU69. It's so ancient, it might represent some of the solar system's earliest building materials from 4.6 billion years ago. | 0.842137 | 3.470895 |
Crescent ♊ Gemini
Moon phase on 22 July 2041 Monday is Waning Crescent, 24 days old Moon is in Taurus.Share this page: twitter facebook linkedin
Previous main lunar phase is the Last Quarter before 2 days on 20 July 2041 at 09:13.
Moon rises after midnight to early morning and sets in the afternoon. It is visible in the early morning low to the east.
Lunar disc appears visually 0.3% narrower than solar disc. Moon and Sun apparent angular diameters are ∠1884" and ∠1889".
Next Full Moon is the Sturgeon Moon of August 2041 after 20 days on 12 August 2041 at 02:04.
There is low ocean tide on this date. Sun and Moon gravitational forces are not aligned, but meet at big angle, so their combined tidal force is weak.
The Moon is 24 days old. Earth's natural satellite is moving from the second to the final part of current synodic month. This is lunation 513 of Meeus index or 1466 from Brown series.
Length of current 513 lunation is 29 days, 13 hours and 45 minutes. It is 1 hour and 29 minutes shorter than next lunation 514 length.
Length of current synodic month is 1 hour and 1 minute longer than the mean length of synodic month, but it is still 6 hours and 2 minutes shorter, compared to 21st century longest.
This New Moon true anomaly is ∠123.4°. At beginning of next synodic month true anomaly will be ∠152.5°. The length of upcoming synodic months will keep increasing since the true anomaly gets closer to the value of New Moon at point of apogee (∠180°).
7 days after point of perigee on 15 July 2041 at 09:14 in ♒ Aquarius. The lunar orbit is getting wider, while the Moon is moving outward the Earth. It will keep this direction for the next 8 days, until it get to the point of next apogee on 30 July 2041 at 20:07 in ♍ Virgo.
Moon is 380 498 km (236 430 mi) away from Earth on this date. Moon moves farther next 8 days until apogee, when Earth-Moon distance will reach 406 212 km (252 408 mi).
1 day after its ascending node on 21 July 2041 at 10:19 in ♉ Taurus, the Moon is following the northern part of its orbit for the next 13 days, until it will cross the ecliptic from North to South in descending node on 4 August 2041 at 23:33 in ♏ Scorpio.
1 day after beginning of current draconic month in ♉ Taurus, the Moon is moving from the beginning to the first part of it.
9 days after previous South standstill on 12 July 2041 at 18:19 in ♐ Sagittarius, when Moon has reached southern declination of ∠-27.311°. Next 3 days the lunar orbit moves northward to face North declination of ∠27.332° in the next northern standstill on 25 July 2041 at 16:19 in ♋ Cancer.
After 5 days on 28 July 2041 at 01:02 in ♌ Leo, the Moon will be in New Moon geocentric conjunction with the Sun and this alignment forms next Sun-Moon-Earth syzygy. | 0.83659 | 3.219447 |
When baby planets melt: Searching for the histories of planetesimals
Let's start at the beginning. Before humans, before Earth, before any of the planets existed, there were baby planets—planetesimals. Coalesced from dust exploded outward by the solar nebula, these blobs of material were just a few kilometers in diameter. Soon, they too aggregated due to gravity to form the rocky planets in the innermost part of the solar system, leaving the early details about these planetesimals to the imagination.
Their mysterious identity is complicated by the fact that Mercury, Venus, Earth, and Mars are all different in chemical composition. Like a blender mixing the ingredients in a cake, Earth has undergone some rearrangement, largely due to volcanism and plate tectonics that shift elements into and out of the interior, that further obscures information about what the original ingredients might have been, and their proportions.
Now, a pair of MIT scientists in the Department of Earth, Atmospheric and Planetary Sciences (EAPS) have revealed some key information about those planetesimals by recreating in a laboratory the first magmas these objects might have produced in the solar system's infancy. And it turns out, there's physical evidence of these magmas in meteorites, adding validation to their claims.
"This formation and differentiation of these planetesimals is kind of an important step in how you make the inner terrestrial planets, and we're really just starting to unlock that story," says R R Schrock Professor of Geology Timothy Grove, senior author on the study, published in a trilogy of papers in the journals Geochimica et Cosmochimica Acta and Meteoritics and Planetary Science.
Tiny pieces of evidence of the solar system's planetary building blocks exist to this day in meteorites, which all fit into two major categories. Chondrites are made of original material and are the most common type. Achondrites come from parent bodies that have experienced some sort of modification—and understanding those modifications helps explain the processes that form and grow planets.
Ureilites, the second most abundant group of achondrites, were the original subject of this investigation. But quickly, the researchers realized their findings could also be applied elsewhere.
Thanks to a series of experiments designed to correct errors in past techniques, Grove and lead author Max Collinet Ph.D. '19 uncovered a new angle. "We really came from wanting to understand something about a small group of meteorites that might seem obscure to a lot of people," says Collinet of his doctoral research. "But then when we did those experiments, we realized that the melts we were producing have a lot of implications to a lot of other planetary building blocks."
This includes the origin of the most abundant type of achondritic meteorites, called eucrites, presumed to come from Vesta, the second-largest body in the asteroid belt. This was because in 1970, an MIT researcher discovered that Vesta was made of the same type of basaltic rock. "We had all these basaltic lavas from the surface of Vesta, and basically everyone assumed that's what happens when you melt these bodies," explains Grove. But recently, other studies have overturned this hypothesis, leaving the question: What were the earliest melts formed in planetesimals?
Making tiny planets
"What we realized is that we did not really know at all what the composition was of those first magmas that were produced in any planetesimal, let alone the one that we were interested in—the parent body of ureilites," says Collinet of the results from their new experimental methods.
In past studies, by using a typical experimental "open system" setup that maintained the low oxygen levels expected inside a planetesimal, much of the highly reactive alkali elements—sodium and potassium—could escape.
Grove and Collinet had to work together to carry out the experiments using a unique device at MIT that kept the system "closed" and retained all alkalis. They loaded a tiny metal capsule a few millimeters square with the same chemical elements that might be present in a planetesimal and subjected it to conditions of low oxygen, rock-melting temperatures, and pressures expected in the relatively small bodies' interiors. Once those conditions were met, the sample's magma was frozen—as recorded in their methods—by "whacking" the machine with a wrench to ensure their capsule popped free, dropping to room temperature quickly.
Analyzing the magma, cooled into a glass, was tricky. Because they were looking for the onset of melting, the pools inside the samples were quite small. It took a few adjustments to their procedures to get all the tiny pools to combine into one larger pocket. Once they were able to measure the samples, the pair were shocked at the implications of what they found.
"We had no idea that we were going to produce this stuff. It was completely unanticipated," Grove marvels. "This stuff" was an alkali-rich granite—a light-colored, silica-rich composition like you might see on a kitchen countertop, on the opposite end of the rock-type spectrum from the alkali-poor, silica-poor basalts on Vesta—like those formed from lava in Hawaii.
"Collinet and Grove show that previous ideas about the compositions of the earliest melts in our solar system, ~4.6 billion years ago, may have been incorrect because the record of early processes has been obscured by geological activity in more recent times," says Cyrena Goodrich, a senior research scientist at the Lunar and Planetary Institute in the Universities Space Research Association, who was not involved in the research. "These results will have applications to a wide range of topics in geology and planetary sciences and will substantially influence future work."
These surprising results almost nearly matched melts measured in many natural meteorite samples. Additionally, the pair had learned something about the mysterious alkalis missing from the rocky planets and the differences between Earth, Mars, Venus and Mercury.
Reimagining the beginning
Previously, it was assumed dissimilarities between the terrestrial planets came about during the initial scattering of elements in the solar nebula and related to how those elements condensed from gases into solids.
"Now we have another way," says Grove. With the melts hosting a lot of the alkalis, it would only take some method of melt removal to leave the residual planetesimals depleted in potassium and sodium.
The next step will be to determine just how these melts could be extracted from the planetesimals' interiors, given that the drivers of magma movement in Earth would likely not be the same in these planetary bodies. In fact, migration of elements in early planets, such as the formation of metal cores, is a wide area of unknown that the pair of scientists are eager to continue exploring.
Due to the inability to observe what actually happened in the establishment of the solar system, the surprises exposed by this study are a significant step. "We bring new clues into how the nebula created these bodies," summarizes Collinet, who is now a postdoc in Germany, working on understanding the layers beneath Mars' outer crust. From a tiny capsule in a lab on the MIT campus or a microscopic droplet of melt in a meteorite, it is possible to reveal insight into the birth of a vast planet.
This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching. | 0.877065 | 3.932757 |
Photos of the Carnegie DTM flag flying on top of the brigatine Carnegie in 1928 [left] and on the International Space Station in 2016 [right]. Photos courtesy DTM Archives and Robert S. Kimbrough/NASA ISS
I hope 2018 is finding you well. The spring edition of our Carnegie Observatories newsletter highlights some major discoveries that have mostly come from our astronomy and planetary science colleagues at Carnegie’s Department of Terrestrial Magnetism in Washington, D.C., and involved scientists and instrument builders here in Pasadena. I wanted to take this opportunity to tell you more about the impressive research being done at DTM.
DTM was founded in 1904 to map the Earth’s geomagnetic field—a hot research topic at the time, which was largely accomplished by 1929. Since then, the department has evolved, but its goal of understanding the Earth and its place in the universe has remained the same. Today, it is home to astronomers and astrophysicists, geophysicists and geochemists, and cosmochemists and planetary scientists.
Some of Carnegie’s most-historic luminaries hailed from DTM, such as National Medal of Science recipient Vera Rubin, whose work with Kent Ford on spiral galaxies confirmed the existence of dark matter.
What’s more, our DTM colleagues share the telescopes and instruments at Carnegie’s Las Campanas Observatory in Chile with us—using them to make many exciting discoveries every year.
Our cross-country colleagues are always busy with work that spans the breadth of planetary science from Earth’s Moon, to our own Solar System, to exoplanets around distant stars. But this winter, they have been particularly productive.
Staff scientist Alycia Weinberger and postdoctoral researcher Meredith MacGregor made big news earlier this month with an announcement of a massive solar flare from Proxima Centauri, the closest star to our own Sun, which raises questions about the habitability of our Solar System’s nearest exoplanetary neighbor, Proxima b.
Also in the planetary realm, Johanna Teske, a postdoc shared by DTM and the Observatories, used the Planet Finding Spectrograph on Carnegie’s 6.5-meter Magellan II telescope to reveal that a star about 100 light years away, GJ 9827, hosts what may be one of the most massive and dense super-Earth planets detected to date.
Too small to sustain the hydrogen fusion process that fuels stars, brown dwarfs are a favorite research topic of planetary scientists. Because they are free-floating, their atmospheric properties are much easier to study without being overwhelmed by the light of a central star. Postdoc Jonathan Gagné led a team that pinpointed the temperature in the cooling-off process when a brown dwarf undergoes a major atmospheric shift.
Our planetary science colleagues don’t just look beyond the boundaries of our own Solar System, however. Some, like postdoc Miki Nakajima, study the formation and evolution of our own Moon. Her latest models show that even though the Moon’s chemistry is turning out to be wetter than previously thought, this doesn’t preclude its formation from a collision between proto-Earth and another object 4.4 to 4.5 billion years ago.
With so much recent impressive work from Carnegie’s DTM, and more to come on the horizon, I wanted to share the scope of work that can be accomplished using our shared Carnegie facilities and knowledge base.
Thank you as always for your support of and interest in Carnegie.
Dr. John Mulchaey
Crawford H. Greenewalt Chair and Director
Photo of Vera Rubin by Mark Godfrey
Illustration of Proxima Cen flare by Roberto Molar Candanosa / Carnegie Institution for Science, NASA/SDO, NASA/JPL | 0.882185 | 3.329099 |
A new documentary airing on the Discovery Channel tomorrow (Feb. 20), looks at the construction of NASA's James Webb Space Telescope, and its place in a long line of universe-changing instruments.
"Telescope," a one-hour documentary, features interviews with many of the scientists involved with the James Webb Space Telescope (JWST), and footage taken at NASA's Goddard Spaceflight Center, where the movie's director, Nathaniel Kahn, has been filming and doing research for about two years.
The documentary succeeds in a task that is often taken for granted in science-oriented communications: It generates excitement in its audience. Viewers who may not have heard of JWST prior to viewing the film will likely walk away with a newly ignited curiosity about this massive telescope, what it might reveal about the cosmos and how it might change humanity's view of our place in the universe. [Photos of Hubble's Successor, the James Webb Space Telescope]
The impact of telescopes
"It's hard to predict the impact that [JWST] will have [on astronomy], because I think it's going to be so big," Amber Straughn, an astrophysicist at NASA Goddard, told Space.com.
Straughn, who is interviewed in "Telescope," is an extragalactic physicist, which means that she studies how stars and black holes form in distant galaxies. JWST, which is scheduled to launch in 2018, will help scientists study the very first galaxies to ever form in the universe, Straughn said.
Scientists will often talk about the "impact" that a new instrument will have on science, or even on all of humanity. But illustrating that point and convincing an audience that it is true can be extremely difficult, either because the answer is long and complex, and takes time to sink in, or because the "impact" isn't necessarily relevant to the viewer.
"Telescope" succeeds in showing that the use of telescopes has affected all of humanity, not just scientists, by changing what we know about the universe and our place in it.
"People take for granted that [the telescope], more than any other instrument in the history of innovation, has changed our sense of ourselves," Kahn told Space.com in an interview. "And it's done it not once, but many, many times."
Examples of this that are brought up in the film include the fact that telescopes played a critical role in showing humans that the Earth is not the center of the universe (or even the solar system). It wasn't until the 20th century that scientists had telescopes powerful enough to reveal the presence of other galaxies, providing the first real grasp of just how mind-bogglingly huge the universe is. It was telescopes that revealed evidence of the Big Bang, which at least partly answered the question, "Where did we come from?" or at least, "How long have we been here?" It was telescopes that revealed the presence of planets around other stars, and telescopes that may answer the question, "Are we alone?"
"The history of telescopes is to teach us that we're not that special. It makes us less and less special every time we look at the universe and we learn there's much more out there than we thought before," Jason Kalirai, a project scientist for JWST says in the documentary.
Many documentaries cover this territory, but the central point can get lost amid too much additional information about the science or history of these events. "Telescope" doesn't bite off more than it can chew, or more than a "general" audience can swallow. While going over this telescopic history, it weaves in information about JWST, and illustrates how it will be another rung on this ladder from which humans can better see the size of the universe and their place in it.
Are we alone?
The aspect of JWST's science plan that has just about everyone on the edge of his or her seat is the study of exoplanets, and specifically, their atmospheres. JWST is an important part of the journey toward answering the question, "Are we alone?" and it will do amazing things. But I do harbor some concern that the documentary overhypes JWST's exoplanet-studying abilities, especially whether or not it could identify signs of life on an exoplanet. Astrophysicist Sara Seager says in the film that for JWST to detect signs of life on an exoplanet (which depends partly on what the telescope can do and partly on what is out there for it to find), is like "winning the lottery five times." To be clear, that is an effective "No," and viewers shouldn't misunderstand those odds. On the other hand, maybe there's nothing wrong with playing the lottery once in a while; maybe hoping for extreme odds is even essential in order for people to willingly invest in major projects like this one.
Thankfully, JWST has much higher odds for what it will accomplish in other scientific pursuits, such as studying the very first galaxies to form in the universe. Because the light from the most distant galaxies in the universe takes billions of years to reach Earth, scientists see those galaxies as they looked billions of years ago — meaning that in some cases, the scientists will be able to see the very first galaxies in the universe, just as they were in the very early stages of their formation.
"The goal of studying those early galaxies is to sort of put together a picture or a story over time," Straughn told Space.com. "You're trying to progressively see how galaxies change over time. … We know that the earliest galaxies must be different from galaxies in the present-day universe."
Only hydrogen and helium (plus very small traces of a few other elements) existed in the early universe, so the first stars must have been made purely of hydrogen and helium. What kind of impact would that have had on how those galaxies looked and how they evolved?
"That epic of the first stars and galaxies is really what we're after with JWST," Straughn said.
But that's just the tip of the iceberg.
"The really great thing about telescopes like Webb is that they're such general-purpose observatories," Straughn said. "It's an observatory that will cover the entire breadth of the universe, from our own cosmic backyard of the solar system, all the way out to the most distant things that we can't even see yet."
The segments featuring people like Straughn, who speaks passionately and excitedly about JWST, are another strong point of "Telescope," and another element of science documentaries that can be taken for granted.
"As a documentary filmmaker, what you look for is people who are able to talk about what they know about, but who are also able to convey their humanity," Kahn told Space.com. Referring to the scientists he interviewed for the documentary, Kahn said, "Their passion [for] their subject and their life study is so infectious and so wonderful. When you start to probe that part of the scientists' minds and hearts, you suddenly open up this wellspring of marvelous drama, which is very exciting from a filmmaking standpoint to get at. Too often, science programming is trying to get all the information in — which is terribly important, we have to get that, too — but sometimes the emotion of the scientists themselves doesn't make it."
Kahn is an amateur telescope maker, and he got to know Matt Mountain because of his homemade telescope. Mountain, among other things, is the telescope scientist for JWST, and he is featured prominently in the film. Kahn began filming at Goddard two years ago, he said. During that time, he received some funding from the Northrop Grumman Foundation (Northrop Grumman is NASA's primary contractor for building JWST). Kahn began development of the documentary with Discovery channel about a year ago, a Discovery representative said.
"Telescope" is a well-done promotion for JWST that will convey to just about any viewer the reasons why people, not just scientists, should be excited about this instrument. While it is not an in-depth look at the science, technology or history of JWST, it does discuss the many, many ways that the mission could fail — for example, the telescope has to unfold from its cramped payload fairing, unfurling like a butterfly emerging from a cocoon. If any part of that unfolding process goes wrong, the telescope could be effectively useless. In addition, it orbits too far from home to be repaired by a space shuttle mission (if there were still any space shuttles). And the documentary does not pursue this question any further: What would it mean for NASA if an overbudget, multibillion-dollar project did not operate optimally, or not at all?
But those are heavy questions, and the consequences of a mission failure are best-explored when the potential benefits of the mission are fully understood as well. As I've said before in this essay, the ability to fully convey the potential awesomeness that JWST could beam down to Earth is not always easy. If "Telescope" seems like a simple look at this mission, it's because sometimes the simplest things take the most care to convey.
"I think to reach out into the dark and to discover things, one has to take risks," Kahn said. "I think that that's what great nations do, and what great scientists do: take risks. So of course it’s a high-stakes mission. But nothing dared, nothing gained.
"I think that it is missions like this that teach us to be bold, Kahn said. "Observing these people working together — it's given me courage, really honestly, in my own life. It's given me courage to be bold. Because I think that when you see people willing to spend years of their lives to build something that pushes the limits of what is possible, it's infectious. It's not enough to just get by. It's not enough to do what you did before. You have to push the limit of what you yourself are capable of," Kahn said.
"Telescope" will air on the Discovery Channel on Saturday, Feb. 20, at 9 p.m./8 p.m. Central. Check local listings. | 0.835479 | 3.100863 |
Don’t miss the upcoming supermoon on Monday, November 14. It will be the closest full moon to Earth since 1948 and we won’t see another supermoon like this until 2034.
The moon’s orbit around Earth is slightly elliptical so sometimes it is closer and sometimes it’s farther away. When the moon is full as it makes its closest pass to Earth it is known as a supermoon. At perigree — the point at which the moon is closest to Earth — the moon can be as much as 14 percent closer to Earth than at apogee, when the moon is farthest from our planet. The full moon appears that much larger in diameter and because it is larger shines 30 percent more moonlight onto the Earth.
The moon is a familiar sight, but the days leading up to Monday, November 14, promise a spectacular supermoon show. When a full moon makes its closest pass to Earth in its orbit it appears up to 14 percent bigger and 30 percent brighter, making it a supermoon. This month’s is especially ‘super’ for two reasons: it is the only supermoon this year to be completely full, and it is the closest moon to Earth since 1948. The moon won’t be this super again until 2034!
The biggest and brightest moon for observers in the United States will be on Monday morning just before dawn. On Monday, November 14, the moon is at perigee at 6:22 a.m. EST and “opposite” the sun for the full moon at 8:52 a.m. EST (after moonset for most of the US).
If you’re not an early riser, no worries. “I’ve been telling people to go out at night on either Sunday or Monday night to see the supermoon,” said Noah Petro, deputy project scientist for NASA’s Lunar Reconnaissance Orbiter (LRO) mission. “The difference in distance from one night to the next will be very subtle, so if it’s cloudy on Sunday, go out on Monday. Any time after sunset should be fine. Since the moon is full, it’ll rise at nearly the same time as sunset, so I’d suggest that you head outside after sunset, or once it’s dark and the moon is a bit higher in the sky. You don’t have to stay up all night to see it, unless you really want to!”
This is actually the second of three supermoons in a row, so if the clouds don’t cooperate for you this weekend, you will have another chance next month to see the last supermoon of 2016 on December 14.
Nothing beats a bright and beautiful “supermoon.” Except maybe, three supermoons! 2016 ends with a trio of full moons at their closest points to Earth.
NASA scientists have studied the moon for decades. A better understanding of our moon helps scientists infer what is happening on other planets and objects in the solar system. “The moon is the Rosetta Stone by which we understand the rest of the solar system,” Petro said.
LRO has been mapping the moon’s surface and capturing high resolution images for more than seven years. Extensive mapping of the moon aids scientists in understanding our planet’s history, as well as that of planetary objects beyond the Earth-moon system.
“Because we have the Apollo samples, we can tie what we see from orbit to those surface samples and make inferences about what has happened to the moon throughout its lifetime,” Petro said. “The samples tell us how old certain lunar surfaces are, and based on the number of impact craters on those surfaces, we can estimate the ages of the rest of the moon. Furthermore, we can then apply those models to estimate the ages of surface on other planets in our solar system — all by studying the moon!” | 0.851749 | 3.349227 |
As a team of researchers led by a Boston University astrophysicist unveils a new model of our heliosphere, we learn how many possibilities are up there in our Solar System. Scientists had long debated the shape of the heliosphere, stating it resembles more a comet than a sphere.
First, there was the 2015 research that utilized a new computer model and information from the Voyager 1. Back then, a collaboration between the Boston University Center for Space Physics and the University of Maryland, explained that the heliosphere has a crescent shape, resembling a “croissant.” From such a statement, it began the most recent survey, promising more detailed results.
The Weird Shape of the Solar System’s Heliosphere Magnetic Field
After the “croissant” shape statement, another vision of the heliosphere has been released by the Cassini spacecraft. Cassini scientists timed the particles echoing off the edge of the heliosphere and correlated them with ions measured by the Voyager 2.
They assumed that the heliosphere is pretty much round and symmetrical. So, the comet-like pattern or the croissant concept doesn’t match at all. It seems the heliosphere is resembling a beach ball a lot, dismissing the idea that assumed for over 55 years that the protective bubble had a comet tail.
NASA’s New Horizons space probe, which is now examing the space beyond Pluto, has unveiled lots of data on the magnetic field of the heliosphere. For example, those particles become around hundreds or nearly thousands of times hotter than t regular solar wind carried away ions.
By modeling the temperature, velocity, and density of the groups of particles separately got some results. They have noticed the particles’ outsized influence on the heliosphere’s magnetic field in the Solar System. Avi Loeb from the Harvard University stated: “If we want to understand our environment, we’d better understand all the way through this heliosphere.” | 0.875011 | 3.534058 |
Hot on the heels of detecting the two highest-energy neutrinos ever observed, scientists working with a mammoth particle detector buried in ice near the South Pole unveiled preliminary data showing that they also registered the signal of 26 additional high-energy neutrinos. The newfound neutrinos are somewhat less energetic than the two record-setters but nonetheless appear to carry more energy than would be expected if created by cosmic rays hitting the atmosphere—a prodigious source of neutrinos raining down on Earth. The particles thus may point to unknown energetic astrophysical processes deeper in the cosmos.
“The result right now is very preliminary,” cautions Nathan Whitehorn of the University of Wisconsin–Madison, who described the new data May 15 during a symposium in Madison on particle astrophysics. “We’re not totally certain right now that it’s from an astrophysical source.” But it is difficult to explain the number and energy of the detected particles by invoking known processes within the solar system. “If this does in fact hold up with more data, and this does turn out to be an astrophysical source, then we’ll be able to address some questions in ways that were totally inaccessible before,” Whitehorn adds.
IceCube physicists are working to understand the origins of high-energy cosmic rays—charged particles from space that strike Earth—which may bear on the origins of the neutrinos as well. “Basically everything you could think of that would make cosmic rays would make neutrinos at the same time,” Whitehorn says. In contrast to neutrinos produced locally when cosmic rays strike the atmosphere, astrophysical neutrinos would originate at the same source as the cosmic rays themselves.
The IceCube Neutrino Observatory makes up for the renowned slipperiness of neutrinos, the lightweight fundamental particles that rarely interact with atoms of matter, by casting a wide net. IceCube consists of more than 5,000 light sensors, buried at depths of up to two kilometers, embedded in enough Antarctic ice to fill several hundred thousand Olympic swimming pools. In such a large volume, one neutrino of the many streaming constantly through space, our bodies and even solid rock occasionally bumps against an atom in the ice, which produces a tiny flash of light.
The properties of the light emitted by a neutrino strike in the IceCube detector, such as the light pattern registered by the sensor array (Is it bloblike or streaky?) as well as the travel direction of the particle (Was it downward from the sky, or upward through Earth?) can reveal which of three known flavors of neutrino was involved and where it came from. Therein lies a key advantage of neutrino astronomy—unlike charged cosmic rays, whose trajectories bend and twist through the cosmos under the influence of magnetic fields, neutral particles such as neutrinos trace straight back to their sources.
From known processes in the atmosphere, researchers expected to register about 10.6 particles over two years with energies measured in the tens or hundreds of tera–electron volts (trillions of electron volts). The 28 detected particles—including the two extremely high-energy particles announced in April—thus indicate an additional neutrino source that has not been accounted for.
So IceCube physicist Naoko Kurahashi Neilson, also of U.W.–Madison, traced the arrival directions of the newfound energetic particles to look for clues to their origins. “What I tried to do is figure out if they point back to anything that might correspond with cosmic-ray production,” she says. But perhaps because there were relatively few particles to work with, no strong patterns emerged. “Because we have a lot of events compared to before, but still not many, it’s hard to say,” she adds. “My conclusion was that there are no identifiable sources at this time.”
The researchers used screening techniques to ferret out impostor particles and limit the background noise from atmospheric neutrinos, such as treating the edge of the detector as a red-flag region. A charged particle such as a muon from the atmosphere would light up sensors at the periphery of the IceCube detector as it enters, whereas a neutrino would penetrate cleanly and trigger sensors deep inside the ice. “You don’t want things that have come into the detector, you want things that start in the detector,” says IceCube physicist Claudio Kopper of U.W.–Madison. Nevertheless, proving that the neutrinos indeed originated in high-energy cosmic processes will take time. “The search is always for the source, and we haven’t found that yet,” Kopper says. “That would be the smoking gun.” | 0.826319 | 4.156104 |
Astronomers using the Atacama Large Millimeter Array (ALMA) have accomplished something even the Hubble Space Telescope is unable to do. By taking advantage of a naturally occurring phenomenon, this networked radio telescope has generated a high-resolution image of a galaxy on the other side of the universe and allowed astronomers to characterize the star forming activity going on within.
The galaxy in question is known as HATLAS J090311.6+003906, sometimes more simply called SDP.81. It’s more than 12 billion light years away, dating it to the very early universe. The Hubble Space Telescope can make out the basic structure of this galaxy, but ALMA was able to tease out much more detail thanks to an effect known as gravitational lensing. It just so happens that a very massive galaxy sits between SDP.81 and Earth, and this distorts the light being emitted by SDP.81.
Because the two galaxies are almost perfectly aligned relative to Earth, the light from SDP.81 is bent into what’s known as an Einstein Ring. You can see above how this makes the galaxy appear as two arcs around the lensing object. The fact that the core of SDP.81 is completely obscured from view also indicates that the foreground galaxy is quite massive indeed. It is estimated the supermassive black hole in its center is on the order of 200-300 million solar masses. The lensing galaxy is a much more modest 4 billion light years away.
ALMA operates as a sophisticated interferometer, an instrument that can superimpose multiple electromagnetic signals on top of each other. All the individual antennas in the array work in concert to collect light and operate effectively as a very large virtual telescope. That means the new images of SDP.81 have about six times the resolution of the latest generation Hubble Space Telescope infrared imaging equipment.
Multiple teams of astronomers were involved in analyzing the images produced by ALMA, and the result is a model that corrects for the lensing effects that reconstructs the composition of the magnified galaxy. The structures of most interest are so-called molecular clouds that are known to be regions of intense star formation. The ALMA data can reveal clumps of galactic matter as small as 200 light years in diameter, fine enough to identify star forming regions, which has never been possible at such a distance (and thus so far in the past).
Astronomers were also able to determine things like the mass and rotational characteristics of SDP.81. According to the data, there is a lot of star forming activity in there, and it’s probably going to shoot upward in the future (which oddly enough is technically the past). The gas in SDP.81 is unstable, and parts of it are collapsing inward, which could lead to new star forming regions. Perhaps this led to the rise and eventual collapse of uncountable civilizations eons before our sun sparked into existence. | 0.85969 | 4.094432 |
This large “flying V” is actually two distinct objects — a pair of interacting galaxies known as IC 2184. Both the galaxies are seen almost edge-on in the large, faint northern constellation of Camelopardalis (The Giraffe), and can be seen as bright streaks of light surrounded by the ghostly shapes of their tidal tails.
These tidal tails are thin, elongated streams of gas, dust and stars that extend away from a galaxy into space. They occur when galaxies gravitationally interact with one another, and material is sheared from the outer edges of each body and flung out into space in opposite directions, forming two tails. They almost always appear curved, so when they are seen to be relatively straight, as in this image, it is clear that we are viewing the galaxies side-on.
Also visible in this image are bursts of bright blue, pinpointing hot regions where the stars from both galaxies have begun to crash together during the merger.
The image consists of visible and infrared observations from Hubble’s Wide Field and Planetary Camera 2. | 0.87451 | 3.596521 |
Our galaxy may hold 100M complex-life-supporting planets:
The number of planets in the Milky Way galaxy which could harbor complex life may be as high as 100 million, Washington State University astrobiologist Dirk Schulze-Makuch writes in a column posted this week on the Air & Space/Smithsonian magazine website.
The estimate, which assumes an average of one planet per star in the Milky Way, is drawn from a study believed to be the first quantitative assessment of the number of worlds in our galaxy that could harbor life above the microbial level.
Schulze-Makuch said the study is significant because it is the first to rely on observable data from actual planetary bodies beyond the solar system, rather than making educated guesses about the frequency of life on other worlds based on hypothetical assumptions.
The research was published recently in the journal Challenges by a group of scientists that includes Louis Irwin, of the University of Texas at El Paso; Alberto Fairen of Cornell University; Abel Mendez of the Planetary Habitability Laboratory at the University of Puerto Rico at Arecibo; and Schulze-Makuch.
The researchers surveyed the growing list of more than 1,000 known planets outside the solar system. Using a formula that considers planetary density, temperature, substrate (liquid, solid or gas), chemistry, distance from its central star and age, they computed a “Biological Complexity Index (BCI),” which rates planets on a scale of 0 to 1.0 according to the number and degree of characteristics assumed to be important for supporting various forms of multicellular life.
“The BCI calculation revealed that 1 to 2 percent of exoplanets showed a BCI rating higher than Europa, a moon of Jupiter thought to have a subsurface global ocean which could harbor different forms of life,” writes Schulze-Makuch. “Based on an estimate of 10 billion stars in the Milky Way Galaxy, and assuming an average of one planet per star, this yields the figure of 100 million. Some scientists believe the number could be 10 times higher.”
He emphasizes that the study should not be taken as an indication that complex life actually exists on as many as 100 million planets, but rather that the figure is the best estimate to date of the number of planets in our galaxy likely to exhibit conditions supportive to such life.
“Also, it should be understood that complex life doesn’t mean intelligent life or even animal life, although it doesn’t rule either out,” Schulze-Makuch said. “It means simply that organisms larger and more complex than microbes could exist in a number of different forms, quite likely forming stable food webs like those found in ecosystems on Earth.
“Despite the large absolute number of planets that could harbor complex life, the Milky Way is so vast that, statistically, planets with high BCI values are very far apart,” Schulze-Makuch writes. “One of the closest and most promising extrasolar systems, known as Gliese 581, has possibly two planets with the apparent capacity to host complex biospheres, yet the distance from the Sun to Gliese 581 is about 20 light years.”
And most planets with a high BCI are much farther away, he said.
If the 100 million planets that the team says have the theoretical capacity for hosting complex life were randomly distributed across the galaxy, Schulze-Makuch said they would lie about 24 light years apart, assuming equal stellar density. And he estimates the distance between planets with intelligent life would likely be significantly farther.
“On the one hand it seems highly unlikely that we are alone,” he writes in the article. “On the other hand, we are likely so far away from life at our level of complexity, that a meeting with such alien forms might be improbable for the foreseeable future.” | 0.837393 | 3.395965 |
How It Worked
Like a highly-sensitive and extremely precise compass, Cassini’s Dual Technique Magnetometer, or MAG, recorded the direction and strength of magnetic fields around the spacecraft.
How We Used It
As Cassini orbited Saturn, the magnetometer recorded the varying strength and direction of the planet’s magnetic field in different locations. This helps scientists learn about the interiors of Saturn and its moons, along with the planet's magnetosphere -- the giant region of space around the planet influenced by its magnetic field. Scientists used MAG data to produce 3-D models of the magnetosphere and to shed light on how the planet's magnetic influence affects the rings, moons, dust and gas within.
Whether in New Delhi or New Jersey, a compass needle will point toward Earth’s magnetic north pole, which is not quite in the same spot as the geographical north pole. Magnetic north is one of two opposing points in a magnetic field, which is produced by a “dynamo” -- fluid movement of molten iron around the planet’s core -- and reaches far into space.
Scientists know far less about Saturn’s magnetic field than they do about Earth’s because to study a magnetic field, you must be within that magnetic field. The Magnetometer, also known as MAG, was aboard the Cassini spacecraft for that reason.
Saturn’s core is a giant ball of unknowns, largely because it’s impossible for even the burliest robotic spacecraft to reach. Lurking below thousands of miles of broiling gases and crushing liquids, Saturn’s deep interior is likely made of hydrogen and helium that’s been forced, by the crushing mass of the planet, into a metallic liquid form. And like Earth’s iron-core dynamo, because currents are swirling within this metallic fluid, it produces a magnetic field.
Early observations gave scientists the first hint at one of the greatest finds of the entire mission -- a liquid water ocean below the frozen surface of Saturn’s moon Enceladus.
After Cassini arrived at Saturn in 2004, the spacecraft orbited in and out of the planet’s magnetosphere, and the MAG instrument measured its strength and direction. "Our instrument is like a very sophisticated magnetic compass traveling through space," says Dr. Nick Achilleos, a science planner and operations engineer working on the magnetometer. "Measuring Saturn's internal magnetic field often shows signatures of the boundaries which separate Saturn's magnetosphere from the solar wind -- these hold information about how Saturn's magnetosphere is continually changing in size and shape."
Because magnetometers are sensitive to magnetic fields produced by spacecraft, Cassini’s magnetometers were installed on a 36-foot (11 meter) non-metal arm called a “mag boom” to get them as far away from the spacecraft as was practical. The mag boom was folded up to fit into the launch vehicle and then unfolded about two years after launch.
The MAG instrument’s two magnetometers were even placed at different distances from the rest of the spacecraft so that their readings can be compared; this helped scientists distinguish Saturn’s magnetic field from any produced by the spacecraft. The vector/scalar helium magnetometer was at the end of the boom, and the fluxgate magnetometer was about halfway along its length.
A Magnetic Oddball
The magnetometers had complementary skills. Both could measure the magnitude and direction of magnetic fields in the spacecraft’s vicinity, but the vector/scalar magnetometer had a second mode in which it detected strength only. The flux gate magnetometer, on the other hand, could detect a range of magnetic strength nearly three times greater than the vector/scalar helium magnetometer.
Cassini’s MAG instrument confirmed that Saturn’s magnetic field is different from that of any other planet in the solar system -- its magnetic poles actually match its axis of rotation. On Earth and Jupiter, for example, magnetic north wanders away from the planet’s rotation axis by about 10 degrees, meaning that if you could see Jupiter’s or Earth’s magnetic field from space, it would appear to wobble like a hula hoop as the planet spins. Saturn’s magnetic north pole, however, is essentially in line with the planet’s axis of rotation, and it would appear to spin smoothly with no wobble. Given this orderly situation, MAG might be expected to observe a steady signal of strength and direction. But that’s not what MAG actually found at Saturn.
MAG detected a signal in Saturn’s magnetic field that repeats every 10 hours and 47 minutes. The periodic signal, called a “periodicity,” suggested that Saturn’s magnetic field isn’t really and truly aligned with the planet’s axis of rotation (what scientists call being "axisymmetric"), even though it would otherwise appear to be so. “If the field was really symmetric, you wouldn’t see periodicities,” said Marcia Burton, a magnetosphere and plasma investigation scientist at NASA’s Jet Propulsion Laboratory who works with the MAG team.
Further, a planet’s magnetic field shouldn’t be aligned with its axis of spin in the first place (according to something called Cowling anti-dynamo theory). “Physics says that it can’t happen, that it should eventually decay,” Burton said. Scientists expected Cassini to find some sort of explanation for that, Burton said. “But it’s a puzzle we still haven’t solved.”
Scientists also expected to find anomalies -- places where a magnetic field is locally distorted or twisted such that it no longer lines up with the planet’s overall magnetic field. But MAG didn't observe any such anomalies. “None that we’ve been able to detect,” Burton said. “The magnetic field is really just north-south around Saturn.”
Puzzles aside, the MAG instrument made first-time measurements of the magnetic state of Saturn’s moon Titan and its atmosphere. It also studied how Titan interacts with the outer fringes of Saturn's magnetosphere and solar wind. (Titan’s orbit sometimes carries it briefly outside of Saturn’s magnetic bubble). Saturn’s rings and dust even interact with Saturn’s magnetic environment, which MAG observed as well.
MAG was a keystone for several of Cassini’s other instruments. “It provides the context for all of the other plasma data we collect,” Burton said.
A Remarkable World
MAG also observed how Titan and Saturn’s icy moons interact with Saturn’s magnetosphere. Some of those early observations gave scientists the first hint at one of the greatest finds of the entire mission -- a liquid water ocean below the frozen surface of Saturn’s moon Enceladus.
Cassini had been in Saturn orbit for less than a year when, in February of 2005, it flew by Enceladus for the first time. MAG saw Saturn’s magnetic field bending around the south pole of Enceladus in a shape that wasn't symmetrical. This turned out to be the first definitive detection of the plume that sprays from the moon's internal ocean. Other magnetometer observations showed that the field was interacting with excited, or ionized, water vapor molecules.
“The magnetometer was really the first to detect the plume,” Burton said. Scientists later found that the plume of water particles was coming from jets at the surface of Enceladus. And further observations from the spacecraft’s dozen or so instruments led scientists to conclude that the moon has an ocean below its surface, making it one of a handful of worlds in our solar system known to harbor liquid water seas.
At a Glance
- Mass: 3.00 kg
- Average Operating Power: 3.10 W
- Average Data Rate: 3.60 kilobits/s | 0.805652 | 4.060971 |
Spring is an exciting time of year for amateur astronomers. Not only is the weather getting warmer, but it signals the start of the Messier marathon. In one single night, observers can see all 110 celestial delights on Charles Messier’s list.
Charles Messier was an 18th-century French astronomer who loved to hunt for comets. As he hunted for comets, he would spot a fuzzy object that did not move against the background of stars, like comets did. This upset Charles, so he started a list of these “comet impostors.” He designated the objects with “M codes.” He discovered the first object, in 1758, in the constellation Taurus, the Bull. It was cataloged M1, which is the Crab Nebula, the only supernova remnant on the list. All but two items on the list are deep sky objects, which are found outside of our solar system. Because Charles used a variety of small telescopes, he was able to catalog only the large, bright objects. Today’s observers need only a medium sized telescope to run the Messier marathon.
The objects on the list are not distributed evenly throughout the sky. With the uneven distribution, none of the targets are in the area between Pisces and Aquarius. The sun moves between these two constellations in late March through early April allowing amateur astronomers to view all Messier objects in one night.
Tips for running the Messier marathon: It’s best to pick a moonless night, within a day or two of the new moon. New moon occurs on March 24 and again on April 22. Pick a night that is forecasted to be clear all night and find a location away from city lights with an open sky view, especially to the west and southeast. Also, have a bad weather backup date. As long as you have a 3-inch, or larger, telescope you should see all the cataloged objects.
Have your game plan in place. Research Messier marathon phone apps and marathon order lists, to create your observational plan. There is a search order list in the March edition of Astronomy magazine. You will need to start as soon as twilight fades. Start with the objects that are only in the sky a few minutes after sunset and finish with the ones that rise a couple minutes before the sun. Dress for the weather and take plenty of snacks. The best part of the marathon is having fun and enjoying a night out under the stars. It’s even better with a group of fellow observers coming together for the marathon. I’ve never completed the Messier marathon, but it certainly is on my bucket list!
The Astronomy Club of Akron is hosting a Messier marathon on Saturday, April 25th, beginning at 8:30. The Astronomy Club of Akron’s observatory is located at 5031 Manchester Road, Akron, Ohio.
Night Sky for March
PLANETS AND THE MOON Venus continues to blaze brightly, magnitude -4.3, in the western sky and sets three hours after sundown. Because Venus is so easy to spot, it will guide you to the planet, Uranus. The two will be close together in early March. On March 8, Venus passes 2 degrees north of Uranus. Then, Venus reaches greatest elongation on March 24 and sets four hours after sunset and pairs with the Crescent Moon on the 26 and 27. By March 29, the Moon, the V-shaped Hyades star cluster, the Pleiades and Venus lie in a 17-degree wide circle. Venus ends the month 3 degrees from the lovely Pleiades and makes a spectacular site in binoculars. Telescope views of Venus, through March, show the planet going from 62 percent lit to 47 percent lit. The predawn planet show featuring Jupiter, Saturn and Mars grows more striking with a gathering of the Moon on March 18. The extraordinary morning planet show continues with the conjunction of Mars and Jupiter on March 20 and the conjunction of Mars and Saturn on March 31. March 31 also features the most compact threesome of the bright outer planets. Mercury joins our other three predawn planets and will be more difficult object to locate in the predawn east-southeastern sky. Binoculars will help locate Mercury.
CONSTELLATIONS The most magnificent picture in our stars, Orion, the Hunter, continues to march westward through March. Facing, southwest, look for the three stars in a line, which make up the belt of Orion. The bright red-orange star up and to the left of the belt is Betelgeuse. The bright blue-white star down and to the right of the belt is Rigel. Draw a line up from the belt to a red, orange star, Aldebaran, which is the eye of Taurus, the Bull. The sideways V shape is the face of Taurus. Above Taurus, the small cluster of stars is the Pleiades or Seven Sisters. Making a counterclockwise loop from the Pleiades, the next bright star is Capella. Continuing down, the two stars you see are Gemini, the Twins.
Turning to the opposite part of the sky or north, the Big Dipper is swinging higher in the sky. Following the two stars at the end of the cup to the next bright star, is Polaris, or the North Star. The constellation Cassiopeia is to the left of Polaris and resembles a sideways letter ‘M”. Head back to the cup of the Big Dipper. Locate the flat part of the cup. Look to the right for the shape of a backwards question mark. This is the head of Leo, the Lion. Towards the end of March, arc off the handle of the Big Dipper to the bright yellow, orange star Arcturus.
BINOCULAR HIGHLIGHTS Facing wests, you will see the small cluster of stars, the Pleiades or the Seven Sisters. The Pleiades is a beautiful open star cluster. Head to Orion, the Hunter. Scan below the three stars of Orion’s belt. You will see fuzzy area with bright stars. This is the Orion Nebula, a hydrogen gas cloud where new stars are forming. For a challenge, scan between Leo and Gemini. There you will find the Beehive Star Cluster.
For further night sky details, maps and audio, visit my website, www.starrytrails.com.
Visit the Hoover Price Planetarium
The Hoover-Price Planetarium will present our seasonal “The Universe at Large”, along with a look at the night sky at 1:00 on Saturdays, and on Sundays at 2:00. The Planetarium seats 65, and admission is included with admission to the Museum. Children must be 5 years or older to attend, and the First Monday of the month program at 2:00 is for adults. The Planetarium is located inside the McKinley Presidential Library & Museum, 800 McKinley Monument Drive, N.W., in Canton, Ohio. For more information please call the Museum at 330-455-7043. | 0.925562 | 3.430686 |
June 04, 2012
Venus will transit the Sun on June 5, 2012.
Venus and Earth describe a unique orbital configuration with respect to the Sun. The resonance between the two planets is readily apparent when a plot of their movements is made over the course of eight years.
Every couple of centuries, the two planets are in close enough alignment that Venus crosses the face of the Sun twice in eight years. Between that pair of crossings, there is a gap of 121.5 years, then two transits in eight years, then a gap of 105.5 years, then two transits, then a gap of 121.5 years, and so on. Why this odd time interval?
Beginning with a transit alignment, as Venus and Earth orbit the Sun, Venus laps Earth in its orbit after 1.6 Earth years, or 2.6 Venusian years. The fifth time that Venus catches up with Earth, after eight years, they are back at their starting point again. The reason there is no transit every eight years is that the orbit of Venus is inclined to the plane of the ecliptic, taking it slightly above or below a line-of-sight with Earth.
After five Venus-Earth conjunctions, they are also slightly clockwise from their starting positions. It takes 105.5 and 121.5 years for them to regress to their eight year transit pairs and shift from June to December. In 2117, Venus will perform during early December.
Thus, Venus is in near resonance with Earth. In order for an exact orbital resonance to exist, Venus would have to revolve in 243.16 days, but its actual period is 243.01 days. This close alignment suggests that it might be moving out of a resonant pattern that once was more precise.
One factor besides gravity that might contribute to its face-to-face dance with Earth is that Venus has a long ion tail that extends outward for more than 45 million kilometers. During inferior conjunction, that electrically charged structure can interact with our magnetosphere. What if that electrical connection was much stronger in the past?
Venus is evidently a young planet, since it retains a dense, hot atmosphere. It also retains some of the cometary characteristics that were probably visible to ancient civilizations. Electric Universe theorist Wal Thornhill writes:
“Venus, with its cometary tail, is evidently still discharging strongly today after a recent cometary past noted globally by ancient witnesses. Venus was described variously as a ‘hairy star’ or ‘bearded star’ and a stupendous prodigy in the sky. Today, Venus’ comet tail operates in the dark discharge mode and is invisible. It can only be detected by magnetometers and charged particle detectors.”
Venus is supposed to have condensed out of the same primordial cloud as the rest of the planets in the Solar System billions of years ago. Most planetary scientists agree that it has been as it is for at least 300 million years. That means the surface of Venus has been subjected to chemical erosion for hundreds of millions of years.
Why is there no sign of any significant erosion? The Russian Venera landing craft discovered that the surface of Venus is bare rock, with a little debris inside the cracks. This is a significant anomaly for which no one has offered a theory. If its entire surface has been renovated in the last 300 million years, what caused that to happen?
Once, perhaps as little as 5000 years ago, the planets were seen as veritable gods, with tremendous powers and chaotic aspects. Those godlike luminaries cast violent energies upon each other and upon Earth: boiling seas, melting mountain ranges, raising sky high tornadoes of fire, and hurling lightning bolts sufficient to vaporize any human work.
The planet-gods did not revolve in the stately orbits we see today. Instead, they encroached on each other, looming large and then retreating, only to rush together in conflict again. During those encounters, Venus and Earth exchanged gigantic outbursts of electric discharge. In those bolts of interplanetary lightning they formed an electromagnetic bond. It was probably then that the orbital resonance that both planets share came into existence.
As time passes, the intimate relationship once shared by Gaea and Aphrodite is beginning to fade. The long ion tail of Venus that continues to brush Earth with its faint electric tickle indicates that it is still in a state of discharge as it slowly regains equilibrium with the Solar System’s overall balance. The past appearance of Venus as a terrifying comet with fire-like tendrils and monstrous features has been detailed elsewhere in these pages. For now, let it be said that the goddess is sleeping, and in her slumber we are drifting apart.
Editor’s note: The link to a plot of the Venus-Earth relationship is from A Little Book of Coincidence by John Martineau | 0.90001 | 3.862436 |
Ancient peoples left traces of their astronomic observations, the origins of which remain mysterious. It seems impossible that they could have seen or understood certain cosmic phenomena without the technological means we have today. For instance, how could the Dogon people from Mali have observed and built their whole cosmogony around a star, Sirius, which they named Sigui Tolo? This star is in fact a binary star, made of Sirius A and Sirius B, the two of which appear aligned on the same axis only once every sixty years. It is likewise according to a sixty-year rhythm that the Dogon celebrate the sigui festival—the “invention of speech and death.”
How could they have known? How could they have known about the “white dwarf” Sirius B—which they named “the companion of Sigui Tolo”—and its sixty-year revolutionary cycle, when the small star could only be observed through telescopes for the first time at the end of the nineteenth century?
From the concept of the infinitely large in Mesopotamian sciences to the concept of the infinitely small in the works of ancient Greeks, such as those by Democritus, the common denominator of all these civilizations is without a doubt the fact that their logical sciences did not exclude intuitive imagination.
On the altar of human knowledge, on each side of which stand sciences and arts, mathematics and arts are opposites. I am referring here to artistic creation in its endless and unexpected aspect: the perpetual and illogical movement that determines its development. A biological, physical, or historical phenomenon can be explained, but it is impossible to write the equation that would explain why the human mind has always sought, and will always seek, to enhance perception and emotion. Metaphorical formulas can be developed, but what endlessly changes the nature and purpose of art can never be logically explained and anticipated, as it belongs to parameters that cannot be observed a priori. Even if unsolved equations do also exist, it is impossible to build a mathematic reasoning to structure the unstructurable that leads to the unexpected, where neither causality nor effects are understandable.
It is always surprising to see in Wolfgang Amadeus Mozart’s scores that there is no trace of marks or redactions. Emotion results from an unexpected juxtaposition of cognitive functions that, when gathered together in a certain moment and space, can activate the senses. This kind of bio-communication system can be mathematically interpreted, but the emotions generated from new shapes and concepts cannot be reduced to rational explanation.
What is important about Mozart’s scores isn’t so much the contrast between the virtuosic purity of the work and the “humanity” of making mistakes by nature, but rather that, in order for music to emerge from a human mind as already complete, the entire mathematical structure of the music must have existed beforehand—even before Mozart himself existed. Like mathematics, music is not invented, but discovered—Mozart would not invent a symphony, but would discover one that already existed somewhere, and would organize it in his mind over the course of a month or a year. Einstein discovered the theory of relativity, Higgs the boson particle. They didn’t invent them. Relativity and bosons existed already, and were waiting to be discovered.
Music’s structure can indeed be explained with mathematics, but what cannot be explained is the irrational origin of the urge that triggers the process through which it will move in a certain direction and then renew itself indefinitely. What is a masterpiece if not a mysterious coincidence, an immeasurable quantity of totally unexpected and paradoxical circumstances merging into a particular moment and space: point T? This phenomenon, rare in any artistic discipline, holds in itself the enigma of its unexpected and extra-human origin, making it endlessly fascinating. Among the billions of factors converging upon this one point, only one is fundamental: the factor of repair, or restoration. Why? Because repair translates from one space/time to another, and crucially as an improvement.
The omnipresence of repair in the universe is without a doubt the sole reason it is shared by both mathematics and art. It is a primary characteristic of human biological and cultural evolution. Without the process of repair, there would be nothing—neither chaos nor stability. Everything is guided by the determinist agency of repair.
I first perceived this phenomenon quite concretely through simple observation in the cultural and political fields and through many years of research on non-occidental tradition and occidental modernity. This led me to reconsider the totemic dimension of traditional cultures and their connections to the immaterial worlds of ancestors. I likewise reconsidered the cultures of modernity and their dogmatic connection with modernity’s motor: progress, which turns its back on the past, toward an ambivalent relation between the artistic avant-garde and the wars of the world.
Charles Darwin and Alfred Russel Wallace’s theory of the evolution of species, which articulated the natural selection necessary for any species to survive in its environment through a process of repair, helped my research to go beyond the concept of the “bricolage” of the savage mind so dear to Claude Lévi-Strauss. A discovery by the 2012 Nobel Prize in physics winner, Serge Haroche, opened my eyes to other horizons where repair is omnipresent: after trying for years to trap an elementary light particle between two mirrors, Haroche and his team could only capture the photon for a tenth of a second. After a tenth of a second, the photon disappears. Where does it go? No one knows. Why does it disappear? “Because nature isn’t perfect,” said Haroche. These two words together tackle a fascinating fundamental issue: the relationship between nature and imperfection.
Is that which the human mind misses or mistakes also imperfect? Is that which culture does not understand also imperfect? Extra-human phenomena belong to an order of things that surpasses us only to then tirelessly reappropriate what belongs to it, repairing a situation that, for a brief moment, suspends its power. This is because the human’s “imperfect” interpretation of nature has a virtual symmetry from nature’s point of view: the abnormality triggered by this experience. Therefore, from the perspective of the quantum order of things, it is this experience that is imperfect. Assuming the photon is as isolated as the abnormality, the quantum order of things repairs this fault by taking the particle back after a tenth of a second.
There are different explanations for this wave’s disappearance from our world, but what is certain is that, in order to reappear and be pieced together again somewhere else, the information that defines it must be stored somewhere. In the universe, black holes are the only known phenomena capable of making anything disappear completely, from matter to light, and their mass depends on the quantity of matter they swallow. But black holes are invisible to the naked eye; they can only be identified through the gravitational influence they exert over their environment (as astrophysicist Andrea Ghez recently observed with the Sagittarius A black hole at the center of our galaxy) or through a “mathematical journey” that makes it possible to approach its periphery, and ultimately its center: its singularity.
According to physicist Leonard Susskind, theoretician Stephen Hawking claimed in 1976 that black holes violate the fundamental principle in physics of the storage of information, because of the process of evaporation that leads to their progressive disappearance. “Hawking radiation” describes the process by which this information evaporates, leading to the progressive disappearance of the black hole. And yet, says Susskind, we should compare this with the concrete example of a computer, because the information stored in its hard drive can be erased, while in reality it is only released into the atmosphere as a quantity of energy absorbed by the molecules around it. This is to say that the information hasn’t totally disappeared. According to Susskind:
When a particle interacts with another one, it can be absorbed, reflected, or also disintegrate into several other particles. But its initial state (electrical charge, mass, impulsion, etc.) can be rebuilt from the product of its interactions. The information borne by this particle is, then, always kept.
This is a fundamental law of quantum physics, and perhaps even the most important law of classical physics as well. From Susskind’s “holographic principle” we now know that when a black hole swallows an object, it keeps the information that defines the object at its surface, or its event horizon. Susskind’s holographic principle gets its name from a process through which an image in three dimensions is built from details coded into a two-dimensional film. Similarly, the holographic principle stipulates that the horizon of a black hole contains the totality of the information included inside. The information contained in a black hole isn’t lost forever, but is rather coded on the surface of its horizon as data. As Susskind further explains:
The horizon would then keep all information borne by all the elements that gave birth to the black hole, but also of all the objects that, attracted by the force of gravity, have gone through the horizon. They would then be returned through photons produced during the evaporation process. Information associated to black holes would then be rejected in the Universe, even if in a blurred form. From then on, they should not be seen as devourers, but as some kind of information tanks.
Because of the accelerating circular movement on the black hole’s event horizon, a disk of accretion forms that works like a dynamo: the more it swallows, the more it turns, and the more it turns, the more it rejects energy. As a black hole attracts more matter, it rejects more of its elementary information. Try, for instance, filling a dog’s bowl using a fire hose. A huge quantity of water will spill out. The acceleration of the event horizon generates a massive and powerful electromagnetic loop that creates, on both sides of the black hole, two gigantic jets of gamma rays, together with electromagnetic eruptions and rejected gas.
What for decades seemed destructive is now clearly recognized by every astrophysicist as creative. Even Hawking admitted he made a mistake. Through Susskind’s theories and the phenomenon of rejection, it is now clear that black holes contribute to the formation of new stars and galaxies. This intermediary cataclysmic phenomenon in fact leads to a cosmic act of creation. It illustrates, at an extraordinary physical scale, a fundamental principle of creation: repair. From the death of a massive star exploding into a supernova, new stars are born.
Repair in the cultural sense of the word can apply to politics, the economy, art, and science, but it is above all on the continuum of extra-cultural activity. What we claim to control, for instance by gathering information with the intention of reusing it, is purely an imitation of fundamental physical phenomena structuring an order of things that precedes and will succeed us as well.
“Nothing is lost, nothing is created, everything transforms,” wrote chemist Antoine-Laurent de Lavoisier. It is not the universe that is a gigantic computer, but we who mimic it. The universe appears to us now as a gigantic fractal vortex swallowing itself and endlessly regenerating.
All images courtesy of the artist. | 0.805746 | 3.568289 |
One of the fundamental questions of mankind is what is the fate of the universe. Hopefully its a long way off. Astronomy has always factored into cosmology and it shouldn’t be any surprise that many of NASA’s probes have studied the factors that may determine our long term outcome. Working with ground based observatories and scientists around the world, recent information has been startling.
First you have to understand that the universe is expanding. Edwin Hubble, for whom the great orbiting observatory is named, discovered that objects at great distances from us are flying away from us with a speed that increases with their distance. If you can measure their speed — which astronomers due by seeing how much the light from an object is shifted to the red end of the spectrum — you can get an accurate indication of how far away they are. The conversion factor between red shift and distance is called the Hubble constant. Edwin Hubble worked in the early part of the 20th century, this is all old news, where are we headed?
One of the big debates in cosmology is whether or not the universe is open or closed. That is, will it expand forever with the stars getting farther and farther apart until the universe suffers what some have called a freezing death? Or at some point will the universe start contracting, headed back toward that density that existed at the beginning which has been called the big crunch (opposite of the big bang)? Turns out it is almost too close to call from the observations we could make from the ground.
But we started sending probes into space. For example the Hubble (the telescope, not the astronomer) has started measuring red-shift and distance much more precisely than we can on the ground. And we sent two probes to study the background radiation lingering from the Big Bang: COBE and WMAP. And they found . . . .that the speed at which the universe is expanding is . . . (drum roll) . . . accelerating!
How can that be? Shouldn’t gravity be slowing things down? Whew. The theoreticians went to work with the data. Turns out that Einstein had it right, except he thought he was wrong. He had put a constant in one of his equations — the Comological Constant — which he later said was his biggest blunder. Now, it seems it wasn’t a blunder at all. Something is making the universe expand faster as time goes on.
Scientists can’t see it, and they can’t measure it, but the only explanation they have for this phenomenon is dark energy. Dark energy must pervade every cubic inch of the universe but we have never detected it. It must cause this acceleration; that is the only possible explanation, so they say.
Whew. Talk about finding out what you didn’t expect. So the universe won’t end in the big freeze or the big crunch but will start expanding so fast that it will end in a big rip!
I wouldn’t worry any time soon. Likely long after we’re gone and long after the earth is baked to a cinder by a dying sun.
So why do we care? Other than the academic interest, that is?
Could we do something with dark energy? I mean, if we could get hold of it. Might get more miles per gallon than gasoline! We’ve just started to figure this out. Some smart person, knowing that it is there, will figure out how to harness it. | 0.810369 | 3.774939 |
Scientists have launched a bid to observe and understand mysterious flashes of light on the surface of the moon. The ‘transient luminous lunar phenomena’ occur several times a week and illuminate parts of the moon’s landscape for a brief period of time before disappearing.
Sometimes, a reverse effect which causes the lunar surface to darken has also been observed. Although there are several theories about the lunar mystery lights’ origins, they have not yet been fully explained. Now astronomers from Julius-Maximilians-Universität Würzburg (JMU) in Bavaria, Germany have set up a telescope which will use artificial intelligence to automatically detect the flashes. When a burst of light is spotted, the telescope will then collect video or photographs of the phenomena which will be studied to help scientists understand the flashes.
The so-called transient lunar phenomena have been known since the 1950s, but they have not been sufficiently systematically and long-term observed,’ said Hakan Kayal, professor of space technology. Kayal has a hypothesis about what’s causing the longer-lasting flashes and hopes to prove this theory. ‘Seismic activities were also observed on the moon,’ the professor added. ‘When the surface moves, gases that reflect sunlight could escape from the interior of the moon. This would explain the luminous phenomena, some of which last for hours.’ However, there is currently no explanation for the briefer flashes. ‘Science does not know exactly how these phenomena occur on the moon. But it has attempted to explain them: the impact of a meteor, for example, should cause a brief glow,’ the university said in a statement. ‘Such flashes could also occur when electrically charged particles of the solar wind react with moon dust.’ | 0.827238 | 3.49523 |
Black holes have so much gravity that even light can't escape from them. If we can't see them, and the suck up all electromagnetic radiation, then how can we find them?
To add to John Conde's answer. According to the NASA web page "Black Holes", detection of black holes can obviously not be performed by detection any form of electromagnetic radiation coming directly from it (hence, can not be 'seen').
The black hole is inferred by observing the interaction with surrounding matter, from the webpage:
We can, however, infer the presence of black holes and study them by detecting their effect on other matter nearby.
This also includes detection of x-ray radiation that radiates from matter accelerating towards the black hole. Although this seems contradictory to my first paragraph - it needs to be noted that this is not directly from the black hole, rather from the interaction with matter accelerating towards it.
There are many, many ways of doing this.
This is by far the most well known. It has been mentioned by the others, but I'll touch on it.
Light coming from distant bodies can be bent by gravity, creating a lens-like effect. This can lead to multiple or distorted images of the object (Multiple images give rise to Einstein rings and crosses).
So, if we observe a lensing effect in a region where there isn't any visible massive body, there's probably a black hole there. The alternative is that we are peering through the dark matter 'halo' which surrounds (and extends passed) the luminous components of every galaxy and galaxy cluster (See: Bullet Cluster). On small enough scales (i.e. - the central regions of galaxies), this is not really an issue.
(This is an artist's impression of a galaxy passing behind a BH)
Spinning black holes and other dynamical systems involving black holes emit gravitational waves. Projects like LIGO (and eventually, LISA) are able to detect these waves. One major candidate of interest for LIGO/VIRGO/LISA is the eventual collision of a binary black hole system.
Sometimes we have a black hole in a binary system with a star. In such a case, the star will orbit the common barycenter.
If we observe the star carefully, its light will be redshifted when it is moving away from us, and blueshifted when it is coming towards us. The variation in redshift suggests rotation, and in the absence of a visible second body, we can usually conclude that there's a black hole or neutron star there.
Salpeter-Zel'dovitch / Zel'dovitch-Novikov proposals
Going in to a bit of history here, Salpeter and Zel'dovitch independently proposed that we can identify black holes from shock waves in gas clouds. If a black hole passes a gas cloud, the gases in the cloud will be forced to accelerate. This will emit radiation (X-rays, mostly), which we can measure.
An improvement on this is the Zel'dovitch-Novikov proposal, which looks at black holes in a binary system with a star. Part of the solar winds from the star will be sucked in to the black hole. This abnormal acceleration of the winds will, again, lead to X-ray shock waves.
This method (more or less) led to the discovery of Cyg X-1
Cyg A is an example of this. Spinning black holes act like cosmic gyroscopes — they do not easily change their orientation.
In the following radio image of Cyg A, we see these faint gas jets emanating from the central spot:
These jets are hundreds of thousands of light years long — yet they are very straight. Discontinuous, but straight. Whatever object lies at the center, it must be able to maintain its orientation for very long.
That object is a spinning black hole.
Most quasars are thought to be powered by black holes. Many (if not all) of the candidate explanations for their behavior involve black holes with accretion disks, e.g. the Blandford-Znajek process.
A black hole can also be detected by how it bends light as various bodies move behind it. This phenomenon is called gravitational lensing, and is the most visually stunning prediction of Einstein's theory of General Relativity.
This image portrays the geometry of gravitational lensing. Light from luminous background objects are bent due to the warping of space-time in the presence of mass (here, the red dot could conceivably be the black hole in question):
Astronomers have discovered the existence of a super-massive black hole at the center of our very own Milky Way Galaxy, and has been dubbed Sagittarius A*.
Over a period of ten years, the trajectories of a small group of stars have been tracked, and the only explanation for their rapid movement is the existence of a highly compact object with the mass of about 4 million suns. Given the mass and distance scales involved, the conclusion is that it must be a black hole.
One way is by following Gamma Ray Bursts. When a black hole feeds on surrounding gas or swallows a star that got too close, they often emit gamma ray bursts which are very energetic and easy to spot (although they don't last long).
In the case of super massive blackholes, they are seemingly at the center of every medium and large galaxy. It makes where to look rather easy.
All 4 answers given prior to this one are very good and complete each other; finding an object orbiting your target object enables you to also calculate the mass of your target object.
Matter falling into a black hole is accelerated toward light speed. As it is accelerated, the matter breaks down into subatomic particles and hard radiation, that is, X-rays and gamma rays. A black hole itself is not visible, but the light (mostly X-rays, gamma rays) from infalling matter that is accelerated and broken up into particles is visible.
By looking toward the center of our galaxy, the Chandra X-ray space telescope has observed several black holes besides Sgr A*, indirectly, by catching the hard radiation of infalling matter flaring up as they swallow something; afterward, the black holes go dark again if there is nothing more to assimilate nearby;
Here you can see some of this flaring in the swarm of black holes near the center of our galaxy.
Methods to detect black holes (which are not really holes or singularities, as they do have mass, radius, rotation, charge and hence density, which varies with radius, see http://en.wikipedia.org/wiki/Schwarzschild_radius ).
to passively detect a (stellar or supermassive) black hole, look/wait for hard radiation flares, which occur sporadically, then follow up with observations to see if you caught a grb (gamma ray burst) from an actual black hole or just a white dwarf or neutron star doing a periodic nova;
to actively detect a black hole look for gravitational lensing, which is a continuous effect, or stars orbiting at a high speed around a seemingly empty point in space, such as S2 at 5000+km/sec, around Sgr A*
But there will be nothing left to see what caused it; better have some observations of that spot in the sky before it happens. | 0.848643 | 4.060408 |
I’m excited to announce that NASA has selected not one, but two possible missions to Venus as part of its studies for the next generation of robotic space probes.
I am beyond excited about this.
For as long as I can remember, Venus has been my favorite of the “Earth-like” planets in our solar system. This is due, in part, to its breathtaking spectacle in the night sky. If you are looking for something to wish upon, Venus will be the first “star” visible in the night sky for a few weeks. Right now, you can see it shining just after sunset in the southwestern sky. Just go outside right after dark and look to the south. You simply cannot miss it.
In fact, many folks mistake it for a supernova or alien spacecraft because its brightness is so shocking in the dim early night. But look through even a simple pair of binoculars, and you’ll see a cloudy surface half lit by the just-setting sun, which tells you that it is, in fact, a planet in our own solar system.
Venus is also very similar to Earth in both size and mass and only about 20% closer to the Sun. On the face of it, it seems as if Earth’s twin might be just a touch warmer than our home world. Up until the middle of the last century, some of the best minds on the planet imagined this cloud-enshrouded world as a jungle planet. I recall as a kid reading stories by Ray Bradbury about our own nearby Dagobah, and I while I haven’t asked him, I suspect George Lucas was inspired by the same stories.
Of course, the Soviet probes of the ’70s put that myth to bed. They discovered a hellish world with a surface temperature hot enough to melt lead and an atmospheric pressure similar to the bottom of the ocean.
It turns out Venus tells a cautionary tale of greenhouse warming. Early in its history, it may have been just a touch warmer than Earth and possibly even inhabited by early life forms. But this slightly warmer climate led the oceans to evaporate more quickly. All of that extra water vapor supercharged the atmospheric warming, leading to more evaporation and eventual loss of those early oceans. The lack of liquid water turned off the plate tectonics responsible for burying the carbon dioxide belched out by the very active volcanoes. As such, the planet just got hotter and hotter and hotter through a positive feedback that could not be stopped.
Today, Venus dissipates its interior heat by periodically burping molten rock across the entire surface, something that last happened over 700 million years ago. As such, we know next to nothing about early Venus beyond what our climate models can tell us, to the point that we are not even sure when Venus finally succumbed to its runaway greenhouse. It probably happened billions of years ago, but it could have happened anytime between then and the last volcanic resurfacing.
It’s the kind of stuff to make a scientist swoon.
Due to this hostile environment, Venus is chronically understudied. The reasons for this are many, but I’m of the opinion that Mars gets more interest because we can imagine eventually sending people to walk on its surface, allowing us to make a more compelling argument to the taxpayers.
If that’s the case, do I have a deal for you.
Due to Venus’ thick atmosphere, it would be possible to float a blimp in its upper reaches, where the temperature cools to nearly shirtsleeve weather. I imagine future respirator-clad “stratonauts” performing experiments like modern oceanographers, dropping experiments off the side of their semi-rigid dirigibles, and hauling up samples and other scientific data.
In the evening, they would retire to the blimp’s lounge, sipping cocktails while someone played the piano. Just like I imagine they do in those airships I read about in my steampunk novels.
In other words, science in the lap of luxury.
Of course, the current Phase A missions to study Venus won’t be looking into sending humans, instead focusing on short robotic excursions of the surface and orbital studies of the atmosphere. But I am very pleased to see Venus getting some much overdue love from NASA.
Still, for my money, you can keep your dust storms and frozen wastes of the red planet. Sign me up for a tour on one of Venus’ ships in the clouds! | 0.850666 | 3.548778 |
Can Astronomy Explain the Biblical Star of Bethlehem?
To understand the Star of Bethlehem, we need to think like the three wise men. Motivated by this “star in the east,” they first traveled to Jerusalem and told King Herod the prophecy that a new ruler of the people of Israel would be born. We also need to think like King Herod, who asked the wise men when the star had appeared, because he and his court, apparently, were unaware of any such star in the sky.
Puzzles for astronomy
These events present us with our first astronomy puzzle of the first Christmas: How could King Herod’s own advisors have been unaware of a star so bright and obvious that it could have led the wise men to Jerusalem?
Next, in order to reach Bethlehem, the wise men had to travel directly south from Jerusalem; somehow that “star in the east” “went before them, ‘til it came and stood over where the young child was.” Now we have our second first-Christmas astronomy puzzle: how can a star “in the east” guide our wise men to the south? The north star guides lost hikers to the north, so shouldn’t a star in the east have led the wise men to the east?
And we have yet a third first-Christmas astronomy puzzle: how does Matthew’s star move “before them,” like the taillights on the snowplow you might follow during a blizzard, and then stop and stand over the manger in Bethlehem, inside of which supposedly lies the infant Jesus?
What could the 'star in the east’ be?
The astronomer in me knows that no star can do these things, nor can a comet, or Jupiter, or a supernova, or a conjunction of planets or any other actual bright object in the nighttime sky. One can claim that Matthew’s words describe a miracle, something beyond the laws of physics. But Matthew chose his words carefully and wrote “star in the east” twice, which suggests that these words hold a specific importance for his readers.
Can we find any other explanation, consistent with Matthew’s words, that doesn’t require that the laws of physics be violated and that has something to do with astronomy? The answer, amazingly, is yes.
Astrological answers to astronomical puzzles
Astronomer Michael Molnar points out that “in the east” is a literal translation of the Greek phrase en te anatole , which was a technical term used in Greek mathematical astrology 2,000 years ago. It described, very specifically, a planet that would rise above the eastern horizon just before the sun would appear. Then, just moments after the planet rises, it disappears in the bright glare of the sun in the morning sky. Except for a brief moment, no one can see this “star in the east.”
We need a little bit of astronomy background here. In a human lifetime, virtually all the stars remain fixed in their places; the stars rise and set every night, but they do not move relative to each other. The stars in the Big Dipper appear year after year always in the same place. But the planets, the sun and the moon wander through the fixed stars; in fact, the word “planet” comes from the Greek word for wandering star. Though the planets, sun and moon move along approximately the same path through the background stars, they travel at different speeds, so they often lap each other. When the sun catches up with a planet, we can’t see the planet, but when the sun passes far enough beyond it, the planet reappears.
And now we need a little bit of astrology background. When the planet reappears again for the first time and rises in the morning sky just moments before the sun, for the first time in many months after having been hidden in the sun’s glare for those many months, that moment is known to astrologers as a heliacal rising. A heliacal rising, that special first reappearance of a planet, is what en te anatole referred to in ancient Greek astrology. In particular, the reappearance of a planet like Jupiter was thought by Greek astrologers to be symbolically significant for anyone born on that day.
Thus, the “star in the east” refers to an astronomical event with supposed astrological significance in the context of ancient Greek astrology.
What about the star parked directly above the first crèche? The word usually translated as “stood over” comes from the Greek word epano, which also had an important meaning in ancient astrology. It refers to a particular moment when a planet stops moving and changes apparent direction from westward to eastward motion. This occurs when the Earth, which orbits the sun more quickly than Mars or Jupiter or Saturn, catches up with, or laps, the other planet.
Together, a rare combination of astrological events (the right planet rising before the sun; the sun being in the right constellation of the zodiac; plus a number of other combinations of planetary positions considered important by astrologers) would have suggested to ancient Greek astrologers a regal horoscope and a royal birth.
Wise men looking to the skies
Molnar believes that the wise men were, in fact, very wise and mathematically adept astrologers. They also knew about the Old Testament prophecy that a new king would be born of the family of David. Most likely, they had been watching the heavens for years, waiting for alignments that would foretell the birth of this king. When they identified a powerful set of astrological portents, they decided the time was right to set out to find the prophesied leader.
Giotto Scrovegni’s Adoration of the Magi depicted the Star of Bethlehem as a comet.
If Matthew’s wise men actually undertook a journey to search for a newborn king, the bright star didn’t guide them; it only told them when to set out. And they wouldn’t have found an infant swaddled in a manger. After all, the baby was already eight months old by the time they decoded the astrological message they believed predicted the birth of a future king. The portent began on April 17 of 6 BC (with the heliacal rising of Jupiter that morning, followed, at noon, by its lunar occultation in the constellation Aries) and lasted until December 19 of 6 BC (when Jupiter stopped moving to the west, stood still briefly, and began moving to the east, as compared with the fixed background stars). By the earliest time the men could have arrived in Bethlehem, the baby Jesus would likely have been at least a toddler.
Matthew wrote to convince his readers that Jesus was the prophesied Messiah. Given the astrological clues embedded in his gospel, he must have believed the story of the Star of Bethlehem would be convincing evidence for many in his audience.
Top image: The Three Kings following the Start of Bethlehem ( public domain )
The article ‘ Can Astronomy Explain the Biblical Star of Bethlehem? ’ by David A Weintraub was originally published on The Conversation and has been republished under a Creative Commons license. | 0.871505 | 3.009605 |
Mouse over the image and scroll to zoom in and out, or use the blue buttons that appear in the lower right corner of the image.
The Monkey Head Nebula is a region of star birth located about 6,400 light-years away. It is also known as NGC 2174 and Sharpless Sh2-252.The nebula is a star-forming region that hosts dusty clouds silhouetted against glowing gas.
The prime source of energy in the nebula is the massive, hot star named HD 42088, which is outside the Hubble image field. This star has a mass 30 times that of the Sun and a surface temperature six times greater. Powerful ultraviolet radiation from the star causes the nebula to shine.
In 2014, astronomers using the NASA Hubble Space Telescope’s powerful infrared vision imaged a small portion of the nebula in the area of the monkey's "eye." Massive, newly formed stars near the center of the nebula (and toward the right in this image) are blasting away at dust. Ultraviolet light from these bright stars helps carve the dust into giant pillars. As interstellar dust particles are warmed from the radiation from the stars in the center of the nebula, they heat up and begin to glow at infrared wavelengths.
This image, released in celebration of Hubble’s 24th anniversary, demonstrates Hubble’s powerful infrared vision and offers a tantalizing hint of what scientists can expect from the James Webb Space Telescope. Learn more at HubbleSite's NewsCenter. | 0.845572 | 3.09252 |
Antikythera mechanism is an ancient Greek analogue computerand orrery used to predict astronomical positions and eclipses for calendrical and astrological purposes.Antikythera (/ˌæntᵻkᵻˈθiːrə/ ant-i-ki-theer-ə or /ˌæntᵻˈkɪθərə/ ant-i-kith-ə-rə) mechanism could also track the four-year cycle of athletic games which was similar, but not identical, to an Olympiad, the cycle of the ancient Olympic Games.
Found housed in a 340 millimetres (13 in) × 180 millimetres (7.1 in) × 90 millimetres (3.5 in) wooden box, the device is a complex clockwork mechanism composed of at least 30 meshing bronze gears. Using modern computer x-ray tomography and high resolution surface scanning, a team led by Mike Edmunds and Tony Freeth at Cardiff University peered inside fragments of the crust-encased mechanism and read the faintest inscriptions that once covered the outer casing of the machine.
Detailed imaging of the mechanism suggests it dates back to 150-100 BC and had 37 gear wheels enabling it to follow the movements of the moon and the sun through the zodiac, predict eclipses and even recreate the irregular orbit of the moon. The motion, known as the first lunar anomaly, was developed by the astronomer Hipparchus of Rhodes in the 2nd century BC, and he may have been consulted in the machine’s construction, the scientists speculate. Its remains were found as one lump later separated in three main fragments, which are now divided into 82 separate fragments after conservation works.
Four of these fragments contain gears, while inscriptions are found on many others. The largest gear is approximately 140 millimetres (5.5 in) in diameter and originally had 224 teeth.
After the knowledge of this technology was lost at some point in antiquity, technological works approaching its complexity and workmanship did not appear again until the development of mechanical astronomical clocks in Europe in the fourteenth century.
All known fragments of the Antikythera mechanism are kept at the National Archaeological Museum in Athens, along with a number of artistic reconstructions of how the mechanism may have looked
Discovery of The Antikythera Mechanism.The Antikythera mechanism was discovered in 45 metres (148 ft) of water in the Antikythera shipwreck off Point Glyphadia on the Greek island of Antikythera.
The wreck was found in April 1900 by a group of Greek sponge divers, who retrieved numerous large artefacts, including bronze and marble statues, pottery, unique glassware, jewellery, coins, and the mechanism.
All were transferred to the National Museum of Archaeology in Athens for storage and analysis.
Merely a lump of corroded bronze and wood at the time, the mechanism went unnoticed for two years while museum staff worked on piecing together more obvious statues.
The world’s first mechanical computer?
To archeologists, it was immediately apparent that the mechanism was some sort of clock, calendar, or calculating device. But they had no idea what it was for. For decades, they debated: Was the Antikythera a toy model of the planets? Or perhaps it was an early astrolabe (a device to calculate latitude)?
On 17 May 1902, archaeologist Valerios Stais found that one of the pieces of rock had a gear wheel embedded in it. Stais initially believed it was an astronomical clock, but most scholars considered the device to be prochronistic, too complex to have been constructed during the same period as the other pieces that had been discovered.
It is not known how the mechanism came to be on the cargo ship, but it has been suggested that it was being taken from Rhodes to Rome, together with other looted treasure, to support a triumphal parade being staged by Julius Caesar.
Origin of Antikythera Mechanism.
Generally referred to as the first known analogue computer, the quality and complexity of the mechanism’s manufacture suggests it has undiscovered predecessors made during the Hellenistic period. Its construction relied upon theories of astronomy and mathematics developed by Greek astronomers, and is estimated to have been created around the late second century BC.
In 1974, Derek de Solla Price concluded from gear settings and inscriptions on the mechanism’s faces that it was made about 87 BC and lost only a few years later. Jacques Cousteau and associates visited the wreck in 1976 and recovered coins dated to between 76 and 67 BC. Though its advanced state of corrosion has made it impossible to perform an accurate compositional analysis, it is believed the device was made of a low-tin bronze alloy (of approximately 95% copper, 5% tin). All its instructions are written in Koine Greek, and the consensus among scholars is that the mechanism was made in the Greek-speaking world.
In 2008, continued research by the Antikythera Mechanism Research Project suggested the concept for the mechanism may have originated in the colonies of Corinth, since they identified the calendar on the Metonic Spiral as coming from Corinth or one of its colonies in Northwest Greece or Sicily. Syracuse was a colony of Corinth and the home of Archimedes, which, so the Antikythera Mechanism Research project argued in 2008, might imply a connection with the school of Archimedes. However, it has recently been demonstrated that while the calendar on the Metonic Spiral belongs to Corinth or one of its colonies in Northwest Greece, it cannot be that of Syracuse. Another theory suggests that coins found by Jacques Cousteau in the 1970s at the wreck site date to the time of the device’s construction, and posits its origin may have been from the ancient Greek city of Pergamon, home of the Library of Pergamum. With its many scrolls of art and science, it was second in importance only to the Library of Alexandria during the Hellenistic period.
The ship carrying the device also contained vases in the Rhodian style, leading to a hypothesis the device was constructed at an academy founded by the Stoic philosopher Posidonius on that Greek island. A busy trading port in antiquity, Rhodes was also a centre of astronomy and mechanical engineering, home to the astronomer Hipparchus, active from about 140 BC to 120 BC. That the mechanism uses Hipparchus’s theory for the motion of the moon suggests the possibility he may have designed, or at least worked on it. Finally, the Rhodian hypothesis gains further support by the recent decipherment of the relatively minor Halieia games of Rhodes on the Games dial. In addition, it has recently been argued that the astronomical events on the Parapegma of the Antikythera Mechanism work best for latitudes in the range of 33.3-37.0 degrees north; Rhodes is located between the latitudes of 35.5 and 36.25 degrees north.
Cardiff University professor Michael Edmunds, who led a 2006 study of the mechanism, described the device as “just extraordinary, the only thing of its kind”, and said that its astronomy was “exactly right”. He regarded the Antikythera mechanism as “more valuable than the Mona Lisa”.
In 2014, a study by Carman and Evans argued for a new dating of approximately 200 BC based on identifying the start-up date on the Saros Dial as the astronomical lunar month that began shortly after the new moon of 28 April 205 BC.
Moreover, according to Carman and Evans, the Babylonian arithmetic style of prediction fits much better with the device’s predictive models than the traditional Greek trigonometric style.
A study by Paul Iversen published in 2017 reasons, on the basis of newly deciphered games on the Games dial as the Halieia of Rhodes and the calendar on the Metonic Spiral being that of Epirus, that the prototype for the device was indeed from Rhodes, but that this particular model was modified for a client from Epirus, in northwestern Greece, and was probably constructed soon before, or within a generation of, the shipwreck.
“Project overview” . The Antikythera Mechanism Research Project. Retrieved 1 July 2007. The Antikythera Mechanism is now understood to be dedicated to astronomical phenomena and operates as a complex mechanical ‘computer’ which tracks the cycles of the Solar System.
Jump up ^ Seaman, Bill; Rössler, Otto E. (1 January 2011). Neosentience: The Benevolence Engine . Intellect Books. p. 111. ISBN 978-1-84150-404-9. Retrieved 28 May 2013. Mike G. Edmunds and colleagues used imaging and high-resolution X-ray tomography to study fragments of the Antikythera Mechanism, a bronze mechanical analog computer thought to calculate astronomical positions
Jump up ^ Swedin, Eric G.; Ferro, David L. (24 October 2007). Computers: The Life Story of a Technology . JHU Press. p. 1. ISBN 978-0-8018-8774-1. Retrieved 28 May 2013. It was a mechanical computer for calculating lunar, solar, and stellar calendars.
Jump up ^ Paphitis, Nicholas (30 November 2006). “Experts: Fragments an Ancient Computer” . Washington Post. Imagine tossing a top-notch laptop into the sea, leaving scientists from a foreign culture to scratch their heads over its corroded remains centuries later. A Roman shipmaster inadvertently did something just like it 2,000 years ago off southern Greece, experts said late Thursday.
^ Jump up to: a b c d e f g h i j k l m n o p q r s Freeth, Tony; Bitsakis, Yanis; Moussas, Xenophon; Seiradakis, John. H.; Tselikas, A.; Mangou, H.; Zafeiropoulou, M.; Hadland, R.; et al. (30 November 2006). “Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism” (PDF). Nature. 444 (7119): 587–91. Bibcode:2006Natur.444..587F . doi:10.1038/nature05357 . PMID 17136087 . Retrieved 20 May 2014.
^ Jump up to: a b c d e f g h i j k l m n o p q r s t u Freeth, Tony; Jones, Alexander (2012). “The Cosmos in the Antikythera Mechanism” . Institute for the Study of the Ancient World. Retrieved 19 May 2014.
Jump up ^ Pinotsis, A. D. (30 August 2007). “The Antikythera mechanism: who was its creator and what was its use and purpose?” . Astronomical and Astrophysical Transactions. 26: 211–226. Bibcode:2007A&AT…26..211P . doi:10.1080/10556790601136925 . Retrieved 9 January 2015.
^ Jump up to: a b c d e f g h i j k l m n o p q r s Freeth, Tony; Jones, Alexander; Steele, John M.; Bitsakis, Yanis (31 July 2008). “Calendars with Olympiad display and eclipse prediction on the Antikythera Mechanism” (PDF). Nature. 454 (7204): 614–7. Bibcode:2008Natur.454..614F . doi:10.1038/nature07130 . PMID 18668103 . Retrieved 20 May 2014.
Jump up ^ Kaplan, Sarah (14 June 2016). “The World’s Oldest Computer Is Still Revealing Its Secrets” , The Washington Post. Retrieved 16 June 2016.
^ Jump up to: a b Paul Iversen, “The Calendar on the Antikythera Mechanism and the Corinthian Family of Calendars, Hesperia 86 (2017): 130 and note 4.
^ Jump up to: a b Sample, Ian. “Mysteries of computer from 65 BC are solved” . The Guardian. “This device is extraordinary, the only thing of its kind,” said Professor Edmunds. “The astronomy is exactly right … in terms of historic and scarcity value, I have to regard this mechanism as being more valuable than the Mona Lisa.” and “One of the remaining mysteries is why the Greek technology invented for the machine seemed to disappear.” | 0.876952 | 3.694065 |
This armillary sphere, with its interlocking rings illustrated the circles of the sun, moon, known planets, and important stars as well as the signs of the zodiac and is a model of the Ptolemaic or earth-centered cosmic system. Ironically, the globe was constructed in the same year that Nicholas Copernicus (1473-1543) published his revolutionary Copernican System with the sun as the center of the solar system.
The Purpose of the Armillary Sphere
A model demonstrates how something works. One of the first models ever made was the armillary sphere, supposedly a model of the universe. By moving the armillary rings, you could demonstrate how the planets moved. However, early models had the Earth at the center of the universe. Like any model, armillary spheres were “modified” or changed with new discoveries.
Early History of the Armillary Sphere
Some sources credit Greek philosopher Anaximander of Miletus (611-547 B. C.) with inventing the armillary sphere, others credit Greek astronomer Hipparchus (190 – 120 BC), and some credit the Chinese.
Armillary spheres first appeared in China during the Han Dynasty (206 B.C.-220 A.D.). One early Chinese armillary sphere can be traced to Zhang Heng, an astronomer in the Eastern Han Dynasty (25 A.D.-220 A.D.).
The exact origin of armillary spheres cannot be confirmed. However, during the Middle Ages armillary spheres became widespread and increased in sophistication.
By Jack Kramer
Gardens in geometric design were de rigueur before the 18th century. Enclosed by walls or hedges, each typically had a centrally placed ornamental feature where its paths met. Sculptures or fountains of all kinds usually filled this space.
Eventually an ornamental pedestal with a sundial became the popular centerpiece. For the manor house or mansion, sundials in the garden began to replace the usual statuary.
In the 18th century the armillary sundial became popular. It was favored because of its ornamental appearance in the garden. More sculpture than timepiece, it’s closely akin to the horological or time-telling sphere. The armillary dial is a sphere surrounded by rings (the word armillary comes from the Latin word for bracelet or hoop). These rings revolve around each other and about the Earth or the sun. They represent circles of celestial spheres. One ring serves as the equator. It’s pierced by an arrow—the Earth’s axis. | 0.816269 | 3.653199 |
What are the EU theory explanations and/or alternatives of the recent suggestion of geological evidence (and computer modelling) of at least two Mars tsunamis created by meteor impacts in a now missing Mars ocean?
Are they the result of what colossal event formed the Valles Marineris and perhaps other grand canyons on planets?
It has been proposed that ~3.4 billion years ago an ocean fed by enormous catastrophic floods covered most of the Martian northern lowlands. However, a persistent problem with this hypothesis is the lack of definitive paleoshoreline features. Here, based on geomorphic and thermal image mapping in the circum-Chryse and northwestern Arabia Terra regions of the northern plains, in combination with numerical analyses, we show evidence for two enormous tsunami events possibly triggered by bolide impacts, resulting in craters ~30 km in diameter and occurring perhaps a few million years apart.
The tsunamis produced widespread littoral landforms, including run-up water-ice-rich and bouldery lobes, which extended tens to hundreds of kilometers over gently sloping plains and boundary cratered highlands, as well as backwash channels where wave retreat occurred on highland-boundary surfaces. The ice-rich lobes formed in association with the younger tsunami, showing that their emplacement took place following a transition into a colder global climatic regime that occurred after the older tsunami event. We conclude that, on early Mars, tsunamis played a major role in generating and resurfacing coastal terrains.
Tsunami waves extensively resurfaced the shorelines of an early Martian ocean | Nature
Could it have been some other event that created large waves or movement and deposition of material?
Below are some summaries of what different Electric Universe theory investigators might suggest what processes took place.
If you think these are not correct or there are other alternative theories then please contact the site or post a message below.
Plasma Arc Blast Geology
Plasma Cosmology plasma arc welding.
Worlds in Collision scenario
An Immanuel Velikovsky based Worlds in Collision scenario interpretation could closely match the scientists announcement but with a much more recent time frame for the impacts/bolides to hit the Mars ocean.
Michael Steinbacher did suggest using Immanuel Velikovsky's ideas that material came into the Earths atmosphere and then an electrical process of aggregation/attraction and sorting of falling debris material created the Grand Canyon.
Steinbacher then suggested that this may be how the sort of similar shaped but scalable Mars Valles Marineris was created.
As possibly shown through Electric Universe geology videos using the EU experiments by Billy Yelverton (Mr2Tuff2).
God King Scenario
To gain some kind of idea of the apocalyptic events to have befallen Mars I have suggested in previous works that it would be like placing Earth in some kind of erratic cosmic washer-dryer for 3,000 years with the setting on melt! It has been tossed, shaken, stirred, boiled and set alight, all of which has transformed it from an Earth-like planet to a now virtually dry, barren, frozen world.
Extraterrestrial Sands book | Gary Gilligan
The Velikovsky/Ackerman scenario also suggests that Mars had its solid iron core pulled out through the Valles Marineris scar by vast electromagnetic forces and that the core become the planet Mercury. If Mars was a water world during that event then it would have created monstrous waves with enough energy to transport material.
Valles Marinas Thunderbolt scenario
Perhaps as a result of the events and processes that created the Valles Marineris, such as a massive electric discharge and/or plasma blast or EDM (electric discharge machining)?
The suggested shoreline debris and waveform area is made up of the lowlands of Chryse Planitiae and Acidalia Planitiae, with the highlands of Xanthe, Tempe and Arabia Terrae. These are found at the northern end of the Valles Marineris.
Transmutation of material in situ scenario?
Any large event not even on Mars could perhaps have caused it, or, whatever created not just the Valles Marineris but other electromagnetic geology such as Olympus Mons.
This could also have happened after any of the events mentioned here.
In one of Billy Yelverton's EU geology videos the experiment seems to show that water follows the electric current creating the rille, canyon, valley. If the Valles Marineris was carved by a plasma arc on a wet Mars and in a Martian sea then could the electrically pulled water with its sediment have come out in this area, like the delta shape the Chryse Planitiae and surrounding area could look like?
Combinations of the scenarios?
Could it have occurred by a combination of a couple or more of the scenarios?
Instead of looking or getting trapped into finding a one time process that can explain it completely it may have been a variety of these processes and could even be over different events and time periods. | 0.803166 | 3.834085 |
Polaris designated α Ursae Minoris, commonly the North Star or Pole Star, is the brightest star in the constellation of Ursa Minor. It is very close to the north celestial pole, making it the current northern pole star. The revised Hipparcos parallax gives a distance to Polaris of about 433 light-years (133 parsecs). Polaris is a triple star system, composed of the primary star, Polaris Aa (a yellow supergiant), in orbit with a smaller companion (Polaris Ab); the pair in orbit with Polaris B (discovered in August 1779 by William Herschel). The reason Polaris is so important is because the axis of Earth is pointed almost directly at it. During the course of the night, Polaris does not rise or set, but remains in very nearly the same spot above the northern horizon year-round while the other stars circle around it. So at any hour of the night, at any time of the year in the Northern Hemisphere, you can readily find Polaris and it is always found in a due northerly direction. If you were at the North Pole, the North Star would be directly overhead. | 0.848789 | 3.306911 |
A season is a period of the year that is distinguished by special climate conditions
A season is a period of the year that is distinguished by special climate conditions. The four seasons—spring, summer, fall, and winter—follow one another regularly. Each has its own light, temperature, and weather patterns that repeat yearly.
In the Northern Hemisphere, winter generally begins on December 21 or 22. This is the winter solstice, the day of the year with the shortest period of daylight. Summer begins on June 20 or 21, the summer solstice, which has the most daylight of any day in the year. Spring and fall, or autumn, begin on equinoxes, days that have equal amounts of daylight and darkness. The vernal, or spring, equinox falls on March 20 or 21, and the autumnal equinox is on September 22 or 23.
The seasons in the Northern Hemisphere are the opposite of those in the Southern Hemisphere. This means that in Argentina and Australia, winter begins in June. The winter solstice in the Southern Hemisphere is June 20 or 21, while the summer solstice, the longest day of the year, is December 21 or 22.
Seasons occur because Earth is tilted on its axis relative to the orbital plane, the invisible, flat disc where most objects in the solar system orbit the sun. Earth’s axis is an invisible line that runs through its center, from pole to pole. Earth rotates around its axis.
In June, when the Northern Hemisphere is tilted toward the sun, the sun’s rays hit it for a greater part of the day than in winter. This means it gets more hours of daylight. In December, when the Northern Hemisphere is tilted away from the sun, with fewer hours of daylight.
Seasons have an enormous influence on vegetation and plant growth. Winter typically has cold weather, little daylight, and limited plant growth. In spring, plants sprout, tree leaves unfurl, and flowers blossom. Summer is the warmest time of the year and has the most daylight, so plants grow quickly. In autumn, temperatures drop, and many trees lose their leaves.
The four-season year is typical only in the mid-latitudes. The mid-latitudes are places that are neither near the poles nor near the Equator. The farther north you go, the bigger the differences in the seasons. Helsinki, Finland, sees 18.5 hours of daylight in the middle of June. In mid-December, however, it is light for less than 6 hours. Athens, Greece, in southern Europe, has a smaller variation. It has 14.5 hours of daylight in June and 9.5 hours in December.
Places near the Equator experience little seasonal variation. They have about the same amount of daylight and darkness throughout the year. These places remain warm year-round. Near the Equator, regions typically have alternating rainy and dry seasons.
Polar regions experience seasonal variation, although they are generally colder than other places on Earth. Near the poles, the amount of daylight changes dramatically between summer and winter. In Barrow, Alaska, the northernmost city in the U.S., it stays light all day long between mid-May and early August. The city is in total darkness between mid-November and January.
Seasons are determined by the Earth’s exposure to the sun.
Illustration by Mary Crooks
Seasons in Alaska
Sometimes, seasons are determined by both natural and man-made activity. In the U.S. state of Alaska, people like to say there are three seasons: “winter, still winter, and construction season.”
A ritu is a season in the traditional Hindu calendar, used in parts of India. There are six ritu: vasanta (spring); grishma (summer); varsha (rainy or monsoon); sharat (autumn); hemant (pre-winter); and shishira (winter).
‘Tis the Season
The word ‘season’ can be used to signify a time of year when an activity or process is allowed to happen. Seasons can be natural, like hurricane season, which is the time of year when hurricanes are most likely to develop. Seasons can also be artificially created, like hunting season, which is the time of year a community allows people to hunt certain wild animals.
Meteorologists, scientists who study the weather, divide each of the seasons into three whole months. Spring begins March 1, summer June 1, autumn September 1, and winter December 1. | 0.825618 | 3.107581 |
Planet Earth doesn’t have ‘a temperature’, one figure that says it all. There are oceans, landmasses, ice, the atmosphere, day and night, and seasons. Also, the temperature of Earth never gets to equilibrium: just as it’s starting to warm up on the sunny-side, the sun gets ‘turned off’; and just as it’s starting to cool down on the night-side, the sun gets ‘turned on’. The ‘temperature of Earth’ is therefore as much of a contrived statistic as the GDP of a country. (If the Earth was in equilibrium, that is, if it absorbed and re-emitted the Sun’s radiation perfectly, as a ‘blackbody’, then its rotation would be irrelevant, and the temperature would be a constant 6 ⁰C. Mocking up the effects of Earth’s albedo brings the ‘blackbody’ temperature down to -18 ⁰C, and including greenhouse warming brings it back up to around 15 ⁰C.)
‘The climate’ is difficult to define: is it a trend over one decade, century, or millennium? What sized region is it defined for? Weather is very variable – how can we go from weather to climate? Furthermore, climate change on human timescales is a very small effect, and the empirical data needed for climate models have large ‘error’ bars. The models themselves have to make many assumptions, and sometimes lead to solutions that are unstable (small changes in the input data lead to large changes in the predictions).
However, despite the above, climate change, more specifically human-induced climate change, is a surprisingly simple idea.
The mathematician and philosopher, Bertrand Russell, summed up mankind’s activities as the rearrangement of matter on or near the Earth’s crust. Russell’s words need refining. The rearranging of matter is done in two different ways: by mechanical devices (such as levers), or by ‘heat-engines’ (such as muscle-power, or combustion engines). (Loosely speaking, anything that ‘farts’ is some sort of heat-engine.) A heat-engine consumes fuel and, by the Second Law of Thermodynamics, ‘always puts out some waste heat.’ Therefore, Russell’s summary should more accurately state: the activities of mankind can be summed up as the rearrangement of matter and the generation of heat. (By the way, ‘waste heat’ refers to direct heating and all other energy losses, not just the production of exhaust gases.)
The only way to reverse global warming is to change the interactions between the Earth and its surroundings…
There is still the question: is this generation of heat enough to cause climate change? Sceptics claim that the activities of people are completely swamped by the immense power of volcanoes, the variability of the Sun’s output, and other ‘natural’ effects. These effects are indeed immense, but note that life forms have affected Earth’s climate in the past (cf. cyanobacteria). Also, while the consequences of the behaviour of any one person are tiny, cumulatively there can be an influence. (In fact, monetarist economic models demand this – people are encouraged to buy things precisely because their individual behaviour affects the economy as a whole.) Finally, there is much evidence of mankind’s influence on the planet in ways not directly related to climate. For example, a ladle-full of seawater from any sea or ocean now always contains some detectable trace of plastic. Even where a material is introduced in miniscule amounts (on the planetary scale), there can be big effects. Witness the use and subsequent control of use of aerosols; this has changed the ozone layer, twice.
Sceptics also argue that natural ‘buffering’ mechanisms keep the Earth’s climate stable – yes, but not if pushed too far. How else has change happened in the past (Ice Ages, etc.)? (An analogy comes from dieting. Go on a weight-loss diet and your body thinks, “Aha, you’re on a fast, switch on the fasting survival-metabolism.” But if you go too far, you die.) If it wasn’t for the finality of it, the present era would be a moment for awe: science textbooks have talked of ‘the surroundings’ or ‘the environment’; now, for the first time, mankind is affecting ‘the surroundings.’
It is agreed that mankind does affect the microclimate (for example, cities are hotter than the surrounding areas) – but is not a whole climate made from microclimates knitted together?
In summary, it would be very surprising if humans were not affecting the climate. Affecting it how? By increasing the amount of global warming – this is what the Second Law of Thermodynamics tells us. According to this Law, so long as our activities concern the planet in isolation, there is nothing whatsoever that we can do to stop global warming (we can merely reduce its rate). The only way to reverse global warming is to change the interactions between the Earth and its surroundings; and this can only be done by reducing the net flux of Solar energy received, by reducing greenhouse gases and/or increasing the Earth’s albedo.
Headline image credit: Earth Atmosphere by NASA/ GSFC. Public Domain via Wikimedia Commons. | 0.821852 | 3.381861 |
By Mo Liu, IV Form
Smozaturn D3 — A Home in Alpha Centauri
In this Advanced Physics independent study unit, I decided to create a planet that is hypothetically habitable by humans in the nearest star system from our very own Solar System — Alpha Centauri. More specifically, the planet, which I have given the name Smozaturn D3, is rotating in set orbit around Proxima Centauri, the dimmest star among all three stars in the Alpha Centauri system, approximately 4.22 light years away. There are many factors that determine the habitability of a planet, including: the chemicals present on the planet, the construction of its atmosphere, and most importantly its distance from the star. Due to this complexity, there are theories like the Rare Earth Hypothesis that argues that complicated and biological life is a very improbable phenomenon and is likely to be extremely rare. However, there is an alternative view known as the principle of mediocrity that argues that the universe is friendly to complex life, since Earth is a tropical rocky planet in a common planetary system.
I personally believe in the existence of earth-like planets in and outside the Milky Way, and with the recent discovery of planets by the Kepler space telescope, astronomers are looking forward to finding potentially habitable worlds from about three-dozen candidates that Kepler has detected.
When we are searching for habitable worlds, one of the most basic criteria is that liquid water must be present, as we currently believe that liquid water is essential to all life. Considering this necessity, the range of the Circumstellar Habitable Zone has to be within the bounds where the planet receives enough radiant energy from its central star. That’s why we also call the CHZ the Goldilocks Zone — it has to be right in the middle, between the two extremes. Although there are many restrictions in identifying CHZs, and they are usually fractions of the size of their star systems, we are able to define the boundaries of a typical CHZ by considering the essential life-supporting elements. The inner edge of the zone is the distance from the star where the runaway greenhouse effect vaporizes all water in liquid form. These are the conditions on the surface of Venus. The outer edge of the zone would be the distance where the planet is so far away from the star that it could not be above the freezing point, no matter how much carbon dioxide is emitted in order to strengthen the greenhouse effect.
Smozaturn D3, like some of the other planets in space, is in thermal equilibrium with its surroundings, meaning that it is absorbing and radiating away energy at the same rate. Smozaturn D3 is also an ideal black body — it absorbs all incident radiation, and it has a functional structured atmosphere that allows it to stay in thermal equilibrium. After setting the initial conditions for my planet, I apply the equation of surface temperature using planet luminosity:
where L is the luminosity of the star and D the distance between the planet and the star. The luminosity of Proxima Centauri is 0.0017L⊙(solar luminosity), and the standard solar luminosity defined by the International Astronomical Union is 3.828×1026 W, therefore the luminosity of Proxima Centauri would be Lpc=6.5076×1023 W. Because the temperature has to be restricted to allow liquid water to exist, the inner bound temperature would be TI=373K and the outer bound temperature would be TO=273K. Plugging the numbers in, the inner bound distance from Proxima Centauri would be
(373K)4= (6.5076×1023 W)/DI2
DI=5.7982×106 km=3.8759×10-2 AU
(1AU=1.496×108 km, the estimated distance between the earth and the sun)
Similarly, the outer bound distance from Proxima Centauri would be
(273K)4= (6.5076×1023 W)/DO2
DO=1.0824×107 km=7.2354×10-2 AU
The distance between the two edges of the CHZ is 3.3595×10-2 AU, which tells us that the range of habitable zone in the Alpha Centauri star system is very small. According to the Vladilo et al. estimation in 2013, the Goldilocks zone in the solar system is within about 0.87 and1.18 AU from the sun, with Earth between the two extremes. Compared to the solar system data, Alpha Centauri’s CHZ is significantly closer to the central star, mainly because Proxima Centauri itself is only a fraction of the size of the sun. The radius of Proxima Centauri is 100,900 km, which is 0.145 R⊙(solar radius), and its mass is only 2.446×1029 kg, only 0.123 M⊙(solar mass). As I mentioned before, the luminosity of Proxima Centauri — the most important factor that determines thermal radiation — is only a small fraction of that of the sun. Smozaturn D3 would be right between the edges at the distance of 5.5557×10-2AU or 8.3112×106km away from Proxima Centauri.
Before I determine the atmosphere structure of Smozaturn D3, I set the radius of my planet to be 2.700×103 km and the gravitational acceleration to 13.5 m/s2. Besides having liquid water, the atmosphere of Smozaturn D3 must contain the essential volatiles that are necessary for life, such as carbon dioxide, oxygen, methane, and ammonia. I use the thermal escape limits of nitrogen and hydrogen to set the boundaries of the mass of Smozaturn D3 with my set radius and gravitational acceleration. If the atmosphere is able to hold gaseous nitrogen it would also be able to hold the heavier volatiles like carbon dioxide and oxygen. Using the same logic, if the planet is able to hold hydrogen, which is the most abundant and also the lightest element in the universe, the pressure would be so high that carbon dioxide and water would only exist in solid form at the surface level, and the planet would therefore be inhabitable. To calculate the mass of the planet using the equation
r = mMw/zTeq
We need to first calculate the equilibrium temperature of Smozaturn D3. The planet has a cross-sectional area of πRp2, and a surface area of 4πd2. When we divide the cross-sectional area by the surface area, we get the ratio of energy that the sphere receives.
πRp2/4πd2 = (Rp/2d)2
Because the energy received by the planet is the luminosity of the star, and because the star is an ideal emitter that radiates like a blackbody, in this particular case the luminosity of Proxima Centauri would be
Lpc = 4πRpc2σTpc4
The total amount of energy received by the planet would therefore be the product of luminosity and the ratio
E = 4πRpc2σTpc4 × (Rp/2d)2
But this equation predicts that the planet absorbs all the incident energy it receives, which is not usually not the case because of albedo expressed as A. Albedo is the ratio of reflected radiation upon the planet’s surface. Different materials have different albedo, and the Earth has an average albedo of 0.3. Smozaturn D3 has the same land structure as the Earth, so it would also have an albedo of about 0.3. If we take the albedo into account, the actual percentage of radiation received would then be 1- A. The energy that the planet absorbs would also be equal to the luminosity of the planet.
Lp = (1-A) × 4πRpc2σTpc4 × (Rp/2d)2 = 4πRp2σTp4
Tp4 = (1-A)Tpc4 (Rpc/2d)2
Tp= Tpc(1-A)1/4 (Rpc/2d)1/2
The surface temperature of Proxima Centauri, Tpc, is approximately 3042K; the albedo of Smozaturn D3 is 0.3, making (1-A) equal to 0.7; the equatorial radius of Proxima Centauri is equal to 1.009×105 km; and the distance from Smozaturn D3 to Proxima Centauri is 8.3112×106 km.
Tp= Tpc(1-A)1/4 (Rpc/2d)1/2
Tp = (3042)(.7)1/4(1.009×105/2(8.3112×106))1/2
Tp = 216.79K
The freezing point of water is at 273.15K, so if this was the mean surface temperature on Smozaturn D3, liquid water would not exist. There has to be something else to ensure the temperature is above the freezing point. The greenhouse effect traps the radiation from the planet’s surface and raises the temperature on Smozaturn D3 to around 300K. The Earth, having an actual equilibrium temperature of 260K, is habitable only because of the existence of greenhouse gases that raise the temperature.
Knowing the radius and the equilibrium temperature gives me the ability to calculate the mass of Smozaturn D3. Using the escape velocity of nitrogen and hydrogen, I can set the boundaries of a planets mass that would be theoretically habitable.
r = mMw/zTeq
where m and r are the mass and radius in Earth units(🜨); Mw is the atomic weight of nitrogen(14.0067g/mol) or hydrogen(1.008g/mol); z is a constant with the value of 2.000×10-2 mol/(gK); and Teq is the equilibrium temperature of Smozaturn D3 — 216.79K.
The smallest value would occur when the planet is just massive enough to hold nitrogen in its atmosphere. The radius of Smozaturn D3 is equal to 2.700×103 km, which is .423795R🜨(Earth radius).
r = m1MNw/zTeq
.423795R🜨 = m1(14.0067)/(2.000×10-2 × 216.79)
m1 = .423795R🜨/3.230476
m1 = .1312494M🜨
m1 = 7.8382×1023 kg
Similarly, the greatest value of mass would occur when the planet is massive enough and the gravitational force is so strong that it would hold gaseous hydrogen in its atmosphere, which means that the high pressure would make heavier volatiles like carbon dioxide solid.
r = m2MHw/zTeq
.423795R🜨 = m2(1.008)/(2.000×10-2 × 216.79)
m2 = .423795R🜨/.232483
m2 = 1.822907M🜨
m2 = 1.08864×1025 kg
Now that I have a range of masses, the atmospheric composition is the key to finding the exact value. If we look at the Earth’s atmosphere, nitrogen accounts for 78.09% of dry air, oxygen 20.95%, argon 0.93%, and many other gases like carbon dioxide, nitrous oxide, and methane are also present. Looking back at the Earth’s thermal equilibrium temperature, if it weren’t because of the greenhouse effect, there wouldn’t be any liquid water. In order for the temperature to rise, the Earth’s atmosphere must hold all essential chemicals involved in the greenhouse process. Some of the most crucial elements involved are water vapor, carbon dioxide, nitrous oxide, and methane, which are also present in the Earth’s atmosphere. Therefore, in order to make Smozaturn D3 an inhabitable planet, the essential elements of the greenhouse effect must be present. I set the atmosphere composition to be
4% carbon dioxide, nitrous oxide, methane
Then I computed a weighted average to determine the mass. Since about 80% of the chemicals are going to be heavy volatiles, the mass would be
m = 1/2(.8m1+.2m2)
m = 1/2(.8(7.8382×1023 kg)+.2(1.08864×1025 kg))
m = 1.402168×1024 kg
With the recent discovery of more than 1,200 exoplanets that Kepler telescope discovered just weeks earlier, we are constantly expanding our outermost reach of the cosmos to a greater limit. Among those 1,200 newly inducted planets, about three-dozen of them are in their own respective Goldilocks zones. Natalie Batalha, the mission scientist, said “calculation suggests tens of billions potentially habitable worlds”(The Guardian). It is hopeful that Kepler is going to add more exoplanets onto our list as it continues its journey through the cosmos, and we will soon discover a world that is habitable for complex life.
Smozaturn D3 Orbital and Physical Characteristics
Equatorial radius: 2.700×103 km
mass: 1.402168×1024 kg
surface area: 1.6965×104 km2
volume: 2.2902×107 km3
mean density: 6.1224×1016 kg/km3
surface gravity: 13.5m/s2
thermal equilibrium temperature: 216.79K
mean surface temperature: 279K
Atmosphere type: CO2-H2O-N2
structure: terrestrial, iron-rock
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Yuhas, A. (2016). More than 1,200 new planets discovered through Nasa’s Kepler space telescope. Retrieved May 19, 2016, from https://www.theguardian.com/science/2016/may/10/new-planets-discovered-nasa-kepler-space-telescope | 0.917223 | 3.890346 |
Aug 23, 2018
Before the space age, astronomers looked up at the night sky and saw points and patches of light.
With the aid of telescopes they could see more points and patches, and with the aid of spectroscopes they could discover what the points and patches were made of and how they moved. But the points and patches were few and far away. The universe appeared dark and empty.
Astronomers assumed that if they detected nothing, nothing was there. They conceived theories to explain how those points of light could be lumps of familiar solids, liquids, and gasses that persisted and moved in the darkness and emptiness. The theory of gravity explained how a cloud of hydrogen could squeeze itself together and heat up. The atomic theory explained how that hot hydrogen could start nuclear reactions and produce more heat. The kinetic theory of gasses explained how the pressure from the heat could balance the pressure from the gravity to create a star. The explanations fit together precisely into a theory of stellar evolution that described everything (or almost everything) seen in the dark and empty universe.
Then the space age extended our sense of sight to include the entire electromagnetic spectrum, from radio waves to gamma rays. It extended our sense of touch to the planets and asteroids and comets, even to the Sun. We stuck the fingers of our probes into the dark and empty spaces. Our sensory sampling of the universe was liberated from the limitations of our biological niche on the surface of a wet and rocky planet. We could sniff the solar wind, taste the rocks on Mars, and see the x-rays from the comets.
We discovered the universe is bursting with plasma, a state of matter almost unknown to our previous geocentric and anthropocentric condition. Plasma is often mistaken for a hot gas, but it doesn’t behave as familiar gasses do. Instead of merely expanding when heated, it pinches into filaments and cells and jets and donuts. It generates magnetic fields and microwave noise and x-ray bursts. It accelerates particles to relativistic velocities and polarizes radiation. It conducts electric currents and transmits power across large distances. It gathers matter from the surrounding space and separates it into shells of like composition.
Now the universe appears bright and full. Jupiter’s magnetosphere, shining in radio frequencies, looks twice the size of the sun or moon. Saturn’s magnetosphere appears a quarter the size of the sun. Venus looks like a monstrous comet whose tail sweeps by us every time it passes between Earth and Sun. Mars sparkles with x-rays.
The Veil Nebula stretches six times the width of the full moon. It’s glowing filaments corkscrew around each other to form a celestial caduceus. The Rosette Nebula covers six times the area of the full moon. Flaming tridents thrust out of incandescent undulations that wrap themselves into an interstellar Ouroborous.
The telescopic dot of a galaxy we call M49 is the invisible center of a cloud of radio emission connecting thousands of galaxies and filling a quarter of the sky. The cloud swirls into the north throwing out knots of x- ray brilliance like astronomical fireworks. The cloud also swirls into the southern sky, where another spray of brilliance erupts. On the other side of the sky swirls a similar cloud. Even the spaces between these glowing plasma cells are filled with the electromagnetic fields of Birkeland “transmission lines.”
We have stumbled into this bright and full universe with minds still adapted to dark and empty theories. We squint our imaginations and shade our thoughts with dogma. We try to adapt our dark and empty theories to these new sensory experiences.
The assumption that detecting nothing means nothing is there is the assumption of a man standing in a dark room: But when he moves, he detects the furniture with his shins. Space probes are the shins of astronomy: They have moved away from the Earth and away from biological senses. They have detected the electrical furniture in space by getting blasted with unexpected radiation and shocked with unforeseen currents. Moving vicariously through the dark spaces with technologically enhanced senses, astronomers who can’t see the light can feel the heat.
Space is not the only domain of experience that has appeared dark and empty. Ancient history, myths, art, and rituals contain much that is obscure. They describe fantastical objects. They depict images devoid of mundane designations. They seem to have little coherent relation to the world of our geocentric and anthropocentric senses.
Many modern social structures and behaviors appear irrational and senseless as well. Wars and oppressions trace their motivations into the shadows of the past. Institutions perpetuate arbitrary yet orderly traditions.
The shins of astronomy have also stumbled into the furniture in this social room. The patterns of human expression now appear to emanate from an archaic spectacle of plasma discharges not seen again until space probes detected them in other stars and plasma physicists reproduced them in laboratories. Our history looks back to an origin in a primordial experience of celestial plasma on Earth.
That experience was both traumatic and galvanic. It brought us both scotoma and lucidity, depravity and nobility. It may have been the genesis of consciousness. We have been obsessed to memorialize it in art and rituals and institutions. We have been compelled to repress it and to deny it but also to imitate it in battles and genocides. But we have also transformed it. Artistic imagination turned that experience of suprahuman events into human expression and meaningfulness. Scientific curiosity turned it into understandings of the nature of things, which empowered development of technologies. Economic inventiveness turned it into the production of wealth through trade and the division of labor. Political conation turned it into diplomacy, social organization, and statesmanship. Religious meditation turned it into spiritual enlightenment.
The space age brings us a vision not only of a cosmos bright with new senses and full of new phenomena but also a history bright with new sensibilities and full of new self-identity. Our ancestors, and therefore we, are neither the victims of dark ignorance nor the dupes of empty superstition but the creators of a developing lucidity and meaningfulness. We are not merely survivors, but heirs. Our opportunity and our responsibility is to invest the profits of the inherited dark and empty theories in new bright and full ventures. | 0.884821 | 4.014141 |
The Kuiper belt is strange. Most of this strangeness probably comes from the fact that we are only just beginning to uncover this mysterious region of the Solar System. Unlike the Oort Cloud which (possibly) lies beyond 3 × 1012 km away (over 20,000 AU, or a whopping 0.3 light years), we can actually observe the objects inside the Kuiper belt as, compared to the Oort Cloud, the Kuiper belt is on our interplanetary doorstep.
But that doesn’t mean it’s close. The Kuiper belt exists in a region of space 30–55 AU from the Sun; this is where Pluto lives (as Pluto itself is a “Kuiper belt object”, or KBO). As astronomical techniques become more advanced however, we are able to discover more KBOs in the zoo of icy-rocky bodies that live in this region.
Having just written about an oddball pair of “highly split” KBOs, I feel compelled to list my top five favourite KBOs. Here are my favourites, as some are really funny-lookin’ and others have some serious personal issues…
5. The identical twins: Antipholus and Antipholus
Having discussed this pair of attention-seeking misfits on Thursday, I’ll keep this brief. The guys at the Canada France Ecliptic Plane Survey (CFEPS) have been keeping an eye on this cubewano pair for seven years — as their name suggests, 2001 QW322 was discovered in 2001. However, what their name does not suggest is that 2001 QW322 is a binary asteroid (so I suppose they can be called 2001 QW322a and 2001 QW322b). But not being content with the “official” designation, the CFEPS astronomers have found a rather clever and descriptive name for the pair. Antipholus and Antipholus.
So why do they have the same name? Because as far as the Kuiper belt hunters can discern, 2001 QW322 “a” and “b” are almost exactly the same size. In fact, from luminosity measurements, astronomers have only measured a variation of 1-5% in the brightness of each. This means that they not only have the same dimensions (100 km in diameter), they also have very similar albedo (reflectiveness).
However, just because they are twins doesn’t make them good enough to be in this list (although it is impressive to find identical twins orbiting each other), it is the distance at which they are orbiting each other which is strange. They have an orbit separated by a whopping 125,000 km. This distance is so huge for two comparatively small objects, it takes Antipholus and Antipholus 25-30 years to complete one orbit. Apparently they have been this way for a billion years and are expected to last another billion. But eventually they will succumb to gravitational disruption and be separated forever.
4. The one with the identity crisis (and family problems): Pluto
Pluto has had a rough ride lately. Firstly, in 2006, the International Astronomical Union (IAU) controversially kicked Pluto out of the Planetary Rotary Club, demoting it to a “dwarf planet”. The IAU had its reasons, but the world was shocked and upset at the decision to change its status.
Pluto was Plutoed.
While Pluto slowly pottered through the Kuiper belt on its 258 year orbit of the Sun, the argument raged here on Earth as to what Pluto actually was. Many wanted Pluto to be re-instated as a planet, but there was a bigger body out there, the trans-Neptunian object (TNO) Eris, that is bigger than Pluto. At first Eris was called the “tenth planet” when it was identified in 2005, but quickly astronomers realised the term “planet” might not apply to the increasing number of “minor planets” in the Kuiper belt and beyond. Unfortunately, Pluto was in the firing line and the IAU made its decision. However, all was not lost. This year, a new class of dwarf planet was defined, named after the demoted ninth planet: the “Plutoid”.
The IAU defines a Plutoid as:
…celestial bodies in orbit around the Sun at a semimajor axis greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit. Satellites of plutoids are not plutoids themselves.
So is this the last we’ve heard of the “Pluto debate?” Probably not.
Although a whole class of objects have been designated as “Plutoids” (including Eris, Haumea, and Makemake) this will be of little comfort to Pluto. The dwarf planet may have an identity crisis, but it has another problem. It looks like Pluto’s two small moons, Nix and Hydra (orbiting at 48,700 kilometres and 64,800 kilometres from Pluto respectively), didn’t originate from the dwarf planet. Pluto’s kids are illegitimate (why do I feel Charon had something to do with this?).
3. The controversial potato: Haumea
Why is Haumea shaped like a potato? Although the dwarf planet has never been directly observed, its elongated shape has been calculated from its light curve. Haumea’s length is twice that of its width. It is believed that the KBO suffered a massive collision, causing it to spin rapidly and become deformed. According to the IAU rules, Haumea meets the criteria as being a dwarf planet (although it is not spherical, it has settled into hydrostatic equilibrium), a Plutoid and a KBO. As it’s orbiting beyond Neptune, it is also a TNO.
So far, so good. It looks strange. Is that it?
Actually, there has been a fair bit of controversy surrounding this little Plutoid. Two teams, one from the US and the other from Spain, claimed to have discovered Haumea at around the same time. In 2005, the Spanish team took credit, but allegations of fraud by the Spanish researchers overshadowed the discovery and delayed the official naming. Before the name “Haumea” (after an Hawaiian godess), it was called 2003 EL61, and it wasn’t officially named by the IAU until September this year. Haumea was only the second dwarf planet discovered since Pluto was discovered back in 1930.
2. It walks on walls: Drac
2008 KV42 has been nicknamed Drac for a very good reason. In the story of Dracula, the mythical vampire is known for his ability to walk on walls and 2008 KV42 is doing a similar thing. This strange KBO has an inclination of more than 90° from the ecliptic, meaning that when compared with all the planets and other KBOs, Drac appears to orbit the Sun in a retrograde motion (i.e. the wrong way).
Drac is approximately 50 km in diameter and isn’t thought to originate from the Kuiper belt, it probably came from a region of space much further away. Its extreme inclination (normally reserved for long period comets — although comets make a closer pass to the Sun; Drac only comes as close as the orbit of Uranus) indicates that it probably originated from a region either above or below the Solar System’s ecliptic plane (see Drac’s orbit above). This means it may have come from the inner Oort Cloud after being gravitationally disrupted by a passing star. It appears to have maintained its current orbit for hundreds of millions of years, although this might change in the future.
It seems possible that Drac is a “transition object”, a nomad from the Oort cloud that is gradually getting closer to the Sun. Perhaps its orbital trajectory will eventually make Drac swing through the inner Solar System in a few million years, before becoming a comet itself.
Perhaps Drac will spread its wings and become more “bat-like” during its transition from KBO to comet…
1. The kidnapped KBO: Triton
Remember the sad story about Pluto’s illegitimate children, Nix and Hydra? Well it seems the gas giant Neptune has a few paternity secrets of its own.
Usually the Kuiper belt is a comparatively stable and peaceful region of the Solar System. That is until one of the outlying gas giants, such as Uranus or Neptune steam past, causing all sorts of gravitational chaos. In fact, the orbital motion of Neptune dictates the orbits of many of the KBOs, nudging them into natural bands, or “resonances”. But it seems that Neptune has done more than influence the orbit of one large KBO, the gas giant stole it.
Astronomers have always known that Triton is a little strange. For starters, it has a retrograde orbit around Neptune. This is an indication that the 2700 km-diameter moon (40% larger than Pluto) didn’t originate in the same solar nebula Neptune was born in; meaning Triton didn’t come from the Neptunian system at all.
Secondly, Triton is very similar in composition and density to Pluto, suggesting that both Pluto and Triton may have evolved in a common location (i.e. the Kuiper belt). Thirdly, Neptune has very few moons (only 13) when compared to Saturn (~200), Jupiter (63) and Uranus (27), supporting the theory of Triton’s abduction by Neptune. The dwarf planet will have entered the Neptunian system with an extremely eccentric orbit taking Triton across the orbits of the other natural moons, disrupting and scattering them from Neptune. Eventually Triton settled into its present-day stable orbit, happily orbiting Neptune, watching the gas giant’s other natural-born satellites whizz past it, orbiting in the opposite direction.
So, Triton is my number one strange Kuiper belt object. It was once at home with all the other Plutoids, cubewanos, TNOs, comets and dwarf planets, but it was abducted by Neptune, never to return… | 0.883928 | 3.733454 |
NASA’s Magnetospheric Multiscale Mission is poised to give astronomers a unique look at magnetic reconnection.
On July 9, 2015 the four spacecraft of NASA’s Magnetospheric Multiscale, or MMS, mission began flying in a pyramid shape for the first time. The four-sided pyramid shape—called a tetrahedron—means that scientists’ observations will be spread out over three dimensions.
MMS will be gathering data to study a phenomenon called magnetic reconnection, which—along with many other places in the universe—happens when the magnetic field surrounding Earth connects and disconnects from the magnetic field carried by solar wind, realigning the very shape of Earth’s magnetic bubble and sending particles flying off at incredible speeds.
This tetrahedral formation is the result of years of discussion between scientists and orbital engineers to fashion feasible orbits that will yield the best possible observations. Such a pyramid is crucial to provide three-dimensional information about Earth’s space environment – if all four spacecraft moved in a line or a plane, MMS couldn’t observe the full shape of a structure as it flew through.
This video shows the dynamic orbit of the four MMS spacecraft. The flexible, pyramid-shaped formation allows MMS to collect the best possible three-dimensional data on magnetic reconnection. The orbit will be adjusted to eventually bring the four spacecraft to within about six miles of each other. Credits: NASA’s Goddard Space Flight Center
The other major feature of MMS’ orbit can be seen right in its name: multiscale. Because the four MMS spacecraft orbits can be changed individually, scientists can adjust the distance among the four spacecraft, allowing them to study magnetic reconnection on a variety of different spatial scales.
“You can think of the formation as a kind of meta-instrument,” said Conrad Schiff, orbital engineer for the MMS mission at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “Kind of like focusing a telescope, adjusting the scale of the MMS spacecraft formation brings different processes into focus.”
Schiff has been part of MMS orbit planning on and off since 1998, long before the mission launched in March 2015. Balancing research goals of the scientists with what is both engineering and economically feasible – more fuel for more maneuverability leads to more expensive launch vehicles, for example – is a conversation that goes on for years before a mission is even officially chosen, much less launched.
The MMS orbit for its first phase, will carry the spacecraft through the front of Earth’s magnetosphere – the magnetic bubble surrounding Earth – right at the boundary where it interacts with the constant wind of solar particles streaming in from the sun. Here, as the sun’s magnetic fields interact with those that surround Earth, explosive magnetic reconnection events are known to happen. Flying though these boundaries every day for over one year, the four spacecraft will zoom through magnetic reconnection events right as they occur.
“Its pyramid formation and extremely fast time resolution will offer the first ever three-dimensional observations down to the smallest scales of reconnection,” said Tom Moore, MMS Project Scientist at Goddard.
The orbital team also made sure that the MMS mission structure is flexible – at different separation distances, the mission can see processes at those all-important different scales. When magnetic reconnection occurs, the magnetic and electric fields in the area change extremely quickly. That leads to telltale behavior of flowing charged particles—which are naturally moved by magnetic and electric fields—that instruments on MMS are designed to measure. So, by looking at the behavior of different charged particles, like electrons and ions, the scientists can “see” what’s happening during magnetic reconnection.
Because ions are so much heavier than electrons – at least 1,800 times heavier – they are not as susceptible to being pushed or pulled by magnetic and electric fields. This means that an ion can travel much farther than an electron before it is drawn in by a magnetic or electric field. This difference means that studying magnetic reconnection happens at two scales – the larger ion scale, and the smaller electron scale. The scaling of the MMS formation will allow scientists to study both.
After its journey through the front of Earth’s magnetosphere, MMS will enter Phase 2, during which its orbit will steadily be enlarged, until it swings all the way out to 99,000 miles away from Earth. There it will move through an area of the magnetosphere behind Earth called the magnetotail – another area where magnetic reconnection is known to happen.
“We talk about the orbit of MMS as a whole and getting it to fly through the day and night side of the magnetosphere,” said Schiff. “But the fact is that each spacecraft is really on its own orbit. So we don’t just have to get a queen bee to fly through the right parts of the day side and night side, we have to keep the whole hive together.”
That means the team must think about not just how each spacecraft orbits Earth, but how it lies in formation with respect to the others – a job that will continue over the lifetime of the mission. When MMS was moved into its first tetrahedral formation in July 2015, the spacecraft were flying about 100 miles apart. The European Space Agency/NASA Cluster mission of four spacecraft had periods in which the spacecraft were that close, but MMS will move even closer. Over the course of the mission’s first phase, that spacing will drop in steps – first down to 40 miles, then 15, and then to just a little over six miles.
These distances will mark an orbital engineering triumph: so many spacecraft have never before flown so close together for an extended period of time. To accomplish this feat MMS makes use of another record-breaking engineering achievement. The spacecraft house the highest working GPS receivers ever flown. GPS—the familiar system you might use to drive to a new place—uses several satellites in orbit about 12,000 miles above Earth to triangulate one’s location. GPS has been used to track spacecraft in lower orbits, but MMS is the first mission to use GPS from above. For comparison, MMS’ flies at maximum height of about 48,000 miles—about four times the height of GPS satellites. As such, it carries extra sensitive GPS sensors in order to receive its signals from the satellites flying on the other side of Earth.
All this attention to orbit planning is of course for a single goal: to gather the best science observations possible.
“Moving MMS into its tetrahedron formation is a really huge milestone,” said Moore. “We are all incredibly excited to be getting on with the science analysis after years of anticipation!”
MMS is currently in commissioning – a phase when its systems and instruments are tested — and it will start official science observation in September 2015. MMS is the fourth NASA Solar Terrestrial Probes Program mission. Goddard built, integrated, and tested the four MMS spacecraft and is responsible for overall mission management and mission operations. The Southwest Research Institute in San Antonio, Texas, leads the Instrument Suite Science Team, with the University of New Hampshire leading the FIELDS instrument suite. Science operations planning and instrument command sequence development will be performed at the MMS Science Operations Center at the University of Colorado’s Laboratory for Atmospheric and Space Physics in Boulder. | 0.812151 | 3.889452 |
Scheduled to launch in late 2013, NASA’s MAVEN spacecraft will study the Martian upper atmosphere in detail, gathering information about relevant processes so scientists can infer how the planet’s atmosphere evolved.
When you navigate with a compass you can orient yourself thanks to Earth’s global magnetic field. But on Mars, if you were to walk around with a compass it would haphazardly point from one anomaly to another, because the Red Planet does not possess a global magnetosphere. Scientists think that this lack of a protective magnetic field may have allowed the solar wind to strip away the Martian atmosphere over billions of years, and now NASA’s MAVEN spacecraft will study this process in detail with its pair of ring core fluxgate magnetometers. Credit: NASA/Goddard/Dan Gallagher
When the Mars Atmosphere and Volatile Evolution (MAVEN) mission begins its journey to the Red Planet in 2013, it will carry a sensitive magnetic-field instrument built and tested by a team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Scheduled for launch in late 2013, MAVEN will be the first mission devoted to understanding the Martian upper atmosphere.
The goal of MAVEN is to determine the history of the loss of atmospheric gases to space through time, providing answers about Mars’ climate evolution.
By measuring the current rate of escape to space and gathering enough information about the relevant processes, scientists will be able to infer how the planet’s atmosphere evolved.
The trip to Mars takes 10 months, and MAVEN will go into orbit around the planet in September 2014.
The Goddard-built MAVEN magnetometer will be a sensitive tool investigating what remains of the Red Planet’s magnetic “shield.” It will play a key role in studying the planet’s atmosphere and interactions with solar wind, helping answer the question of why a planet once thought to have an abundance of liquid water became a frozen desert.
“The MAVEN magnetometer is key to unraveling the nature of the interactions between the solar wind and the planet,” said MAVEN principal investigator Bruce Jakosky from University of Colorado at Boulder’s Laboratory for Atmospheric and Space Physics (CU/LASP).
The magnetometer will measure the planet’s magnetic field through a series of coils, each containing a magnetic ring wrapped around a metal core. The sensors, known as “flux gates,” are driven in and out of saturation by applied magnetic fields.
If there is no ambient magnetic field, the sensors remain balanced. If there is an ambient field present, the sensors will go into saturation more quickly in one direction than the other. It’s the imbalance that reveals the presence of an ambient field.
“A magnetometer is like an electronic compass,” said Jack Connerney, mission co-investigator at Goddard. “But we measure the strength, as well as the direction, of the magnetic field.”
The importance of studying the planet’s magnetic field is rooted in the theory that Mars lost its global magnetic field billions of years ago, allowing the solar wind to strip the atmosphere and dry out the planet.
Unlike Earth’s global magnetic field, which surrounds the entire planet, Mars only has patches of magnetic field left in its crust. This can create pockets of atmosphere that are protected against solar wind and others that are left vulnerable.
By measuring sections of the planet’s magnetic field, the magnetometer could help scientists create a bigger picture of the planet’s overall atmosphere.
“The magnetometer helps us see where the atmosphere is protected by mini-magnetospheres and where it’s open to solar wind,” Connerney said. “We can study the solar wind impact and how efficient it is at stripping the atmosphere.”
The magnetometer is one of six instruments that make up the Particles and Fields Package, being assembled by team members at the University of California, Berkeley. The magnetometer works with the other instruments from this package to gather data throughout the course of the projected yearlong orbit around the planet.
The spacecraft will go into orbit and pass closely over the planet’s surface and then move further away to study solar wind beyond the planet’s influence.
The magnetometer is a very sensitive instrument, so engineers have to work to ensure the instrument doesn’t accidentally measure the spacecraft’s magnetic field instead of the one the planet produces.
“We have to go to great extremes to be sure that we have minimized any magnetic fields from the spacecraft,” Jakosky said. “We are working hard to build a very ‘magnetically clean’ spacecraft that will meet our needs with regard to the magnetometer.”
The MAVEN principal investigator comes from CU/LASP. The university provides science operations, is building science instruments, and leads education/public outreach. NASA Goddard manages the project and is building two of the science instruments for the mission. Lockheed Martin of Littleton, Colo., is building the spacecraft and is responsible for mission operations. The University of California at Berkeley Space Sciences Laboratory is building science instruments for the mission. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., provides navigation support, the Deep Space Network, and the Electra telecommunications relay hardware and operations.
Image: NASA/Goddard/Dan Gallagher | 0.834397 | 3.984287 |
Comets are the big “question marks” of observational astronomy. Some, such as Comet Hyakutake and the Great Daylight Comet of 1910 present themselves seemingly without warning and put on memorable displays. Others, such as the infamous Comet Kohoutek or Comet Elenin, fizzle and fail to perform up to expectations after a much anticipated round of media hype.
And then there’s the case of Comet C/2012 S1 ISON. Discovered on September 21st, 2012 by Artyom Novichonok and Vitali Nevski while conducting the International Scientific Optical Network (ISON) survey, Comet ISON has captivated public interest. The media loves a good comet, or at least the promise of one.
But will Comet ISON perform up to expectations? Recently, veteran comet hunter and observer John Bortle weighed in on a Sky & Telescope post and an email interview with Universe Today on what we might expect to see this fall.
Dozens of comets are discovered every year. Most amount to nothing – a handful, like this year’s comet 2011 L4 PanSTARRS or 2012 F6 Lemmon, may become interesting binocular objects.
Part of what alerted astronomers that Comet ISON may become something special was its extreme discovery distance of 6.7 astronomical units (A.U.s) meaning it should be an intrinsically bright object, coupled with its close approach of 0.012 A.U.s (1.1 million kilometres, accounting for the solar radius) from the surface of the Sun at perihelion.
Universe Today recently caught up with Mr. Bortle, who had the following to say above tentative prospects for Comet ISON in late 2013:
“Comets coming into the near-solar neighborhood from the Oort Cloud for the very first time tend to behave rather differently from most of their other icy brethren. They often will show considerable early activity while still far from the Sun, giving a false sense of their significance. Only when they have ventured to within about 1.5-2.0 astronomical units of the Sun do they begin to reveal their true intrinsic nature in the way of brightness and development. When discovered far from the Sun, this situation has misled astronomers time and again into announcing that a grandiose display is in the offing, only to have the comet ultimately turn out to be a general disappointment. There have been exception to this, but they are rare indeed.”
Comet ISON bears similar characteristics to many of the great sungrazing comets of the past. In the last few months, word has made rounds that Comet ISON may be underperforming, stagnating around magnitude +16 (10,000 times fainter than naked eye visibility) as it crosses the expanse of the asteroid belt between Jupiter and Mars.
Bortle, however, cautioned against writing off ISON just yet in a recent message board post. “With this comet’s exceedingly small perihelion distance, the ultimate situation is less clear.” He also continues to note that the prospects for ISON are “really difficult to predict at the moment,” but estimates that Comet ISON “will not actually attain naked eye brightness until just a week or two before perihelion passage.”
Regarding naked eye visibility of Comet ISON, Mr. Bortle also told Universe Today:
“In all probability this will not occur until around early to mid-November. It will not become any sort of impressive sight before disappearing into the morning twilight only a couple of weeks thereafter.”
And that’s the big question that may make the difference between a fine binocular comet and the touted “Comet of the Century…” Will this comet survive its perihelion passage on November 28th?
Concerning the comet’s perihelion passage, Mr. Bortle told Universe Today:
“This is currently a matter of some concern to me. Basing my answer on ISON’s apparent brightness when it was last seen before disappearing into the evening twilight recently suggests that it might be close in intrinsic brightness to the survival/non-survival level for such an extremely close encounter with the Sun. We will know much better once we can view ISON again in September.”
Comet Ikeya-Seki was another sungrazing comet that went on to become a splendid naked eye comet in 1965. The late 1880’s hosted a slew of memorable comets, including two long-tailed sungrazers, one each in 1880 and 1887.
In more recent times, Comet C/2011 W3 Lovejoy survived its December 16th, 2011 perihelion passage 140,000 kilometres from the surface of the Sun to become the surprise hit for southern hemisphere observers.
“IF” comet ISON breaks a negative magnitude, it’ll join the ranks on the top brightest comets since 1935. If it tops -10th magnitude, it’ll best Comet Ikeya-Seki at its maximum in 1965. The magic “brighter than a Full Moon” threshold sits right about at magnitude -12.5, but Bortle cautions that this peak brightness will only persist during the hours surrounding perihelion, when the comet will be very close to the Sun and difficult to see.
Mr. Bortle also voiced a concern to Universe Today that “the initial announcements by professional astronomers concerning ISON’s potential future brightness (“Brighter than the Full Moon”, etc.) were wildly excessive, as was the idea that the comet would be obvious to the general public in the daytime sky as it rounded the Sun in late November. This claim was totally unjustified from the word go.” Mr Bortle also warns that this may be “headed us down the exact same road as the Kohoutek fisaco of 1973/74.”
We’re currently losing Comet ISON behind the Sun as it crosses through the constellation Gemini, not return to morning skies until late August. The comet will cross the orbit of Mars in early October and should also cross the +10th magnitude threshold and become visible in binoculars and small telescopes around this date.
From October on in, things should get really interesting. Mr. Bortle predicts that the comet will “develop more slowly in the autumn sky than initially thought,” and won’t become a naked eye object until around November 10th or so. What this sort of lag might do to the internet pundits and prognosticators might be equally interesting to watch.
ISON will also track near some interesting morning objects as seen from Earth, including Mars (October 18th), Spica (November 18th), and Mercury & Saturn low in the dawn on November 26th. It will also have another famous comet nearby on November 25th (photo op!) short period Comet 2P Encke.
If Comet ISON survives perihelion, the true show could begin in early December. Comet ISON will re-emerge in the dawn skies, passing a pairing of Mercury and the very old crescent Moon on December 1st. Comet tails are even less predictable than comet magnitudes, but if Comet ISON is to unfurl a long photogenic tail, the weeks leading up to Christmas may be when it does it.
Mr. Bortle predicts a 10 to 15 degree long tail for a post-perihelion ISON as it passes through the constellation Ophiuchus into morning skies. It may become a “headless wonder” similar to the fan-shaped display put on by Comet 2011 L4 PanSTARRS earlier this spring. We’ve even seen models projecting a great fan-shaped dust tail seeming to “loop” around the Sun as seen from our Earthly vantage point!
All interesting conjecture to watch unfold as Comet ISON approaches perihelion this November. Hopefully, the hysteria that follows great cometary apparitions won’t reach a fevered pitch, though we’ve already had to put some early conspiracies to bed surrounding comet ISON.
Will ISON be the “Comet of the Century?” Watch this space… we’ll have more on the play-by-play action as it approaches!
-Read John Bortle’s predictions for Comet ISON in his recent Sky & Telescope post. | 0.809095 | 3.697307 |
Saturn will pass very close to the Sun in the sky as its orbit carries it around the far side of the solar system from the Earth.
At closest approach, Saturn will appear at a separation of only 1°54' from the Sun, making it totally unobservable for several weeks while it is lost in the Sun's glare.
At around the same time, Saturn will also be at its most distant from the Earth – receding to a distance of 10.93 AU – since the two planets will lie on opposite sides of the solar system.
If Saturn could be observed at this time, it would appear at its smallest and faintest on account of its large distance. It would measure 15.2 arcsec in diameter.
Over following weeks and months, Saturn will re-emerge to the west of the Sun, gradually becoming visible for ever-longer periods in the pre-dawn sky. After around six months, it will reach opposition, when it will be visible for virtually the whole night. A chart of the path of Saturn across the sky in 2014 can be found here, and a chart of its rising and setting times here.
The position of Saturn at the moment it passes solar conjunction will be:
|Object||Right Ascension||Declination||Constellation||Angular Size|
The coordinates above are given in J2000.0.
|The sky on 18 November 2014|
26 days old
All times shown in EST.
Never attempt to point a pair of binoculars or a telescope at an object close to the Sun. Doing so may result in immediate and permanent blindness.
The circumstances of this event were computed using the DE405 planetary ephemeris published by the Jet Propulsion Laboratory (JPL).
This event was automatically generated by searching the ephemeris for planetary alignments which are of interest to amateur astronomers, and the text above was generated based on an estimate of your location.
|18 Nov 2014||– Saturn at solar conjunction|
|22 May 2015||– Saturn at opposition|
|29 Nov 2015||– Saturn at solar conjunction|
|03 Jun 2016||– Saturn at opposition| | 0.866823 | 3.556024 |
Levels of methane on Mars have dropped following a spike detected by Nasa’s Curiosity Rover last week which fuelled discussions about the possibility of life.
The American space agency’s rover spotted its highest amount of the gas yet, though scientists cautioned that methane can also be created through interactions between rocks and water.
Planned operations were scrapped this weekend in favour of taking a second reading, showing that the amount of methane had dropped to background levels of one part per billion units by volume (ppbv), down from the 21 ppbv measured on Wednesday.
Nasa has therefore referred to it as a transient methane plume.
🔎 The game is afoot.
I'm continuing to investigate the Martian methane mystery. A follow-on investigation shows that this past week's methane levels have sharply decreased. https://t.co/fC6lDxATiM pic.twitter.com/4w7aVRa2Hk
— Curiosity Rover (@MarsCuriosity) June 25, 2019
This change matches up with previous highs and lows picked up by Curiosity’s Sample Analysis at Mars (SAM), an instrument tasked with analysing gases, although last week’s measurement is the highest concentration the mission has recorded since landing on the planet in August 2012.
“We did make the run again, the data just came back and in fact the methane plume went away,” Paul Mahaffy, principal investigator for SAM, said at a Nasa town hall event at the Astrobiology Science Conference on Monday.
Curiosity is not fitted with equipment to figure out the source of the methane, making it impossible to tell whether it is biological or geological.
Methane is destroyed by solar radiation within several hundred years when it enters the atmosphere, so it must have been released quite recently.
Despite this, there remains the possibility that the gas could have been trapped underground for millions or billions of years, and only just been released.
The @MarsCuriosity team conducted a follow-on methane experiment this weekend, and the results came down this morning: The plume of methane has largely vanished. The volume is now close to the background levels Curiosity sees all the time. More info: https://t.co/ABSrKk40n9 (1/3) pic.twitter.com/JPciYEVVED
— Thomas Zurbuchen (@Dr_ThomasZ) June 25, 2019
“The methane mystery continues,” said Ashwin Vasavada, Curiosity’s project scientist at Nasa’s Jet Propulsion Laboratory.
“We’re more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.”
Dr Mahaffy said they would continue to work with other missions on Mars, such as the European Space Agency’s Mars Express spacecraft and the Trace Gas Orbiter, to uncover any signs of life on the Red Planet. | 0.820871 | 3.048873 |
After just yesterday we wrote that Jupiter’s emblematic Giant Red Storm was quieting down, Neptune’s own giant storm is about to suffer the same fate.
Although not as famous and easily visible as the Great Red Spot, Neptune’s Great Dark Spot (creative names, I know) has its own remarkable history. Also an anticyclonic storm, the first Dark Spot was first observed in 1989 by NASA’s Voyager 2. It was big enough to cover the entire Atlantic, from the US to Europe’s West Coast, but unlike Jupiter’s storm, it had a much shorter lifespan. I say “the first” Dark Spot because, since its discovery in 1989, several others have appeared and disappeared, and the initial one is long gone. Hubble discovered two dark storms that appeared in the mid-1990s and then vanished. The current storm was first observed in 2015, but it’s already shrinking.
We don’t really know that much about Neptune. The farthest planet from the Sun (sorry Pluto) remains largely a mystery, with most of our information coming from remote observations or from the Voyager days. The way it was discovered says a lot about this: Neptune was the first and only planet in our Solar System found by mathematical prediction rather than by empirical observation. Astronomers believe that Neptune has a solid rock core, a mantle consisting of water, ammonia and methane ices, and an atmosphere. The top of the atmosphere is covered by top clouds, while the rest consists of hydrogen, helium, and methane The Dark Spot is interesting because it allows astronomers to indirectly deduce certain aspects about Neptune’s atmosphere.
The Great Dark Spot is thought to represent a hole in the methane cloud deck of Neptune, generating large white clouds made of frozen methane. The dark spot itself might also contain hydrogen sulfide, a substance commonly found in crude petroleum, natural gas, volcanic gases, and hot springs.
It seems a bit strange if you think about it — why would white clouds, including ice, create a dark spot? Well, it isn’t that they’re necessarily dark, just that they’re less bright than the rest of the atmosphere. Joshua Tollefson from the University of California at Berkeley explained.
“The particles themselves are still highly reflective; they are just slightly darker than the particles in the surrounding atmosphere.”
But other than this, we don’t really know much about the nature of these storms. We don’t know why or how they form, and no missions other than Voyager and Hubble are able to visualize them.
“We have no evidence of how these vortices are formed or how fast they rotate,” said Agustín Sánchez-Lavega from the University of the Basque Country in Spain. “It is most likely that they arise from an instability in the sheared eastward and westward winds.”
Unlike Jupiter’s storms, Neptune’s storms don’t last as long. Neptune doesn’t have atmospheric conveyor belts, which keep the storm trapped, and it doesn’t have the proper atmospheric conditions to fuel the storm. So quite soon, the Dark Spot will fade away — but another one will eventually rise up to take its place.
“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect,” said Michael H. Wong of the University of California at Berkeley, referring to work by Ray LeBeau (now at St. Louis University) and Tim Dowling’s team at the University of Louisville. | 0.801207 | 3.93906 |
Scientists studying freshly fallen snow in Antarctica have uncovered a rare isotope of iron in the interstellar dust hidden inside it, suggesting the dust showed up recently. This discovery could give us crucial information about the history of stellar explosions in our galactic neighbourhood.
We know that cosmic dust is drifting down to Earth all the time, tiny bits of debris from the rough and tumble of star and planet formation, sometimes billions of years old. Antarctica is a great place to look for such dust, because it’s one of the most unspoilt regions on Earth, making it easier to find isotopes that didn’t originate on our own planet.
In this case, the isotope that researchers have pinpointed is the rare 60Fe (or iron-60), one of many radioactive variants of iron. Previously, the presence of this iron in deep-sea sediment and fossilised remains of bacteria has suggested one or more supernovae exploded in Earth’s vicinity between 3.2 and 1.7 million years ago.
The new study marks the first time interstellar iron-60 has been detected in recent Antarctic snow – the dust would have fallen from the skies within the last 20 years, the researchers say.
“I was personally very surprised, because it was only a hypothesis that there might be iron-60 and it was even more uncertain that the signal is strong enough to be detected,” nuclear physicist Dominik Koll from Australian National University told ScienceAlert.
“It was a very joyful moment when I saw the first iron-60 count appear in the data, because that means that our overall astrophysical picture might not be too wrong.”
That picture goes as follows: the Solar System is currently travelling through what’s known as the Local Interstellar Cloud (LIC), a pocket of dense interstellar medium that contains several cloudlets of interstellar dust.
If iron-60 has been deposited on Earth in recent years, that helps to validate the idea that our local galactic neighbourhood and its particular make-up of interstellar starstuff may have been shaped by exploding stars.
Further research should be able to tell us for sure. It could also help us to better pinpoint our location in the LIC, and how long the Solar System has been traversing it. “We would expect a sharp increase in flux of iron-60 around the time when the Solar System entered the LIC,” the team writes in their study.
The current study involved a highly sensitive mass spectrometry chemical analysis carried out on 500 kilograms (1,100 lbs) of snow shovelled up from Antarctica and carefully transported to Germany – to one of only two sites worldwide where this sort of analysis can be carried out.
“There are basically no stable iron or other elements abundant in Antarctica which helps a lot for the measurement of 60Fe/Fe ratios,” Koll told ScienceAlert. “The snow was taken by shovelling and was packed in storage boxes that were kept below 0°C to keep the snow frozen until it arrived in Munich.”
The researchers measured the ratios of other element isotopes in their sample, to make sure the iron isotope was truly interstellar in origin. This allowed them to rule out other possible origins closer to home, such as space rocks within our Solar System irradiated with cosmic rays, or even nuclear weapons tests.
The more we know about the timing and location of supernova explosions in our cosmic neighbourhood, the better we can understand the Universe around us – and the footprints it leaves down here on Earth.
“This is actually quite a profound thing,” astrophysicist Brian Fields from the University of Illinois at Urbana-Champaign, who was not involved with the research, told Science News.
“It’s telling us about the recent history of our whole neighbourhood in the galaxy and about the lives and deaths of massive stars.”
The research is due to be published in Physical Review Letters. | 0.86642 | 3.942117 |
Super star clusters are groups of hundreds of thousands of very young stars packed into an unbelievably small volume. They represent the most extreme environments in which stars and planets can form.
Until now, super star clusters were only known to exist very far away, mostly in pairs or groups of interacting galaxies. Now, however, a team of European astronomers have used ESO’s telescopes to uncover such a monster object within our own Galaxy, the Milky Way, almost, but not quite, in our own backyard!
The newly found massive structure is hidden behind a large cloud of dust and gas and this is why it took so long to unveil its true nature. It is known as “Westerlund 1” and is a thousand times closer than any other super star cluster known so far. It is close enough that astronomers may now probe its structure in some detail.
Westerlund 1 contains hundreds of very massive stars, some shining with a brilliance of almost one million suns and some two-thousand times larger than the Sun (as large as the orbit of Saturn)! Indeed, if the Sun were located at the heart of this remarkable cluster, our sky would be full of hundreds of stars as bright as the full Moon. Westerlund 1 is a most unique natural laboratory for the study of extreme stellar physics, helping astronomers to find out how the most massive stars in our Galaxy live and die.
From their observations, the astronomers conclude that this extreme cluster most probably contains no less than 100,000 times the mass of the Sun, and all of its stars are located within a region less than 6 light-years across. Westerlund 1 thus appears to be the most massive compact young cluster yet identified in the Milky Way Galaxy.
Super Star Clusters
Stars are generally born in small groups, mostly in so-called “open clusters” that typically contain a few hundred stars. From a wide range of observations, astronomers infer that the Sun itself was born in one such cluster, some 4,500 million years ago.
In some active (“starburst”) galaxies, scientists have observed violent episodes of star formation (see, for example, ESO Press Photo 31/04), leading to the development of super star clusters, each containing several million stars.
Such events were obviously common during the Milky Way’s childhood, more than 12,000 million years ago: the many galactic globular clusters – which are nearly as old as our Galaxy (e.g. ESO PR 20/04) – are indeed thought to be the remnants of early super star clusters.
All super star clusters so far observed in starburst galaxies are very distant. It is not possible to distinguish their individual stars, even with the most advanced technology. This dramatically complicates their study and astronomers have therefore long been eager to find such clusters in our neighbourhood in order to probe their structure in much more detail.
Now, a team of European astronomers has finally succeeded in doing so, using several of ESO’s telescopes at the La Silla observatory (Chile).
The open cluster Westerlund 1 is located in the Southern constellation Ara (the Altar constellation). It was discovered in 1961 from Australia by Swedish astronomer Bengt Westerlund, who later moved from there to become ESO Director in Chile (1970 – 74). This cluster is behind a huge interstellar cloud of gas and dust, which blocks most of its visible light. The dimming factor is more than 100,000 – and this is why it has taken so long to uncover the true nature of this particular cluster.
In 2001, the team of astronomers identified more than a dozen extremely hot and peculiar massive stars in the cluster, so-called “Wolf-Rayet” stars. They have since studied Westerlund 1 extensively with various ESO telescopes.
They used images from the Wide Field Imager (WFI) attached to the 2.2-m ESO/MPG as well as from the SUperb Seeing Imager 2 (SuSI2) camera on the ESO 3.5-m New Technology Telescope (NTT). From these observations, they were able to identify about 200 cluster member stars.
To establish the true nature of these stars, the astronomers then performed spectroscopic observations of about one quarter of them. For this, they used the Boller & Chivens spectrograph on the ESO 1.52-m telescope and the ESO Multi-Mode Instrument (EMMI) on the NTT.
An Exotic Zoo
These observations have revealed a large population of very bright and massive, quite extreme stars. Some would fill the solar system space within the orbit of Saturn (about 2,000 times larger than the Sun!), others are as bright as a million Suns.
Westerlund 1 is obviously a fantastic stellar zoo, with a most exotic population and a true astronomical bonanza. All stars identified are evolved and very massive, spanning the full range of stellar oddities from Wolf-Rayet stars, OB supergiants, Yellow Hypergiants (nearly as bright as a million Suns) and Luminous Blue Variables (similar to the exceptional Eta Carinae object – see ESO PR 31/03).
All stars so far analysed in Westerlund 1 weigh at least 30-40 times more than the Sun. Because such stars have a rather short life – astronomically speaking – Westerlund 1 must be very young. The astronomers determine an age somewhere between 3.5 and 5 million years. So, Westerlund 1 is clearly a “newborn” cluster in our Galaxy!
The Most Massive Cluster
Westerlund 1 is incredibly rich in monster stars – just as one example, it contains as many Yellow Hypergiants as were hitherto known in the entire Milky Way!
“If the Sun were located at the heart of Westerlund 1, the sky would be full of stars, many of them brighter than the full Moon”, comments Ignacio Negueruela of the Universidad de Alicante in Spain and member of the team.
The large quantity of very massive stars implies that Westerlund 1 must contain a huge number of stars. “In our Galaxy, explains Simon Clark of the University College London (UK) and one of the authors of this study, “there are more than 100 solar-like stars for every star weighing 10 times as much as the Sun. The fact that we see hundreds of massive stars in Westerlund 1 means that it probably contains close to half a million stars, but most of these are not bright enough to peer through the obscuring cloud of gas and dust”. This is ten times more than any other known young clusterin the Milky Way.
Westerlund 1 is presumably much more massive than the dense clusters of heavy stars present in the central region of our Galaxy, like the Arches and Quintuplet clusters. Further deep infrared observations will be required to confirm this.
This super star cluster now provides astronomers with a unique perspective towards one of the most extreme environments in the Universe. Westerlund 1 will certainly provide new opportunities in the long-standing quest for more and finer details about how stars, and especially massive ones, do form.
… and the Most Dense
The large number of stars in Westerlund 1 was not the only surprise awaiting Clark and his colleagues. From their observations, the team members also found that all these stars are packed into an amazingly small volume of space, indeed less than 6 light-years across. In fact, this is more or less comparable to the 4 light-year distance to the star nearest to the Sun, Proxima Centauri!
It is incredible: the concentration in Westerlund 1 is so high that the mean separation between stars is quite similar to the extent of the Solar System.
“With so many stars in such a small volume, some of them may collide”, envisages Simon Clark. “This could lead to the formation of an intermediate-mass black hole more massive than 100 solar masses. It may well be that such a monster has already formed at the core of Westerlund 1.”
The huge population of massive stars in Westerlund 1 suggests that it will have a very significant impact on its surroundings. The cluster contains so many massive stars that in a time span of less than 40 million years, it will be the site of more than 1,500 supernovae. A gigantic firework that may drive a fountain of galactic material!
Because Westerlund 1 is at a distance of only about 10,000 light-years, high-resolution cameras such as NAOS/CONICA on ESO’s Very Large Telescope can resolve its individual stars. Such observations are now starting to reveal smaller stars in Westerlund 1, including some that are less massive than the Sun. Astronomers will thus soon be able to study this exotic galactic zoo in great depth.
The research presented in this ESO Press Release will soon appear in the leading research journal Astronomy and Astrophysics (“On the massive stellar population of the Super Star Cluster Westerlund 1” by J.S. Clark and colleagues). The PDF file is available at the A&A web site. A second paper (“Further Wolf-Rayet stars in the starburst cluster Westerlund 1”, by Ignacio Negueruela and Simon Clark) will also soon be published in Astronomy and Astrophysics. It is available as astro-ph/0503303.
A Spanish press release issued by Universidad de Alicante is available on the web site of Ignacio Negueruela.
: The team is composed of Simon Clark (University College London, UK), Ignacio Negueruela (Universidad de Alicante, Spain), Paul Crowther (University of Sheffield, UK), Simon Goodwin (University of Wales, Cardiff, UK), Rens Waters (University of Amsterdam) and Sean Dougherty (Dominion Radio Astrophysical Observatory).
Original Source: ESO News Release | 0.923494 | 3.903447 |
Title: Reionization of the Milky Way, M31, and their satellites I: Reionization History and Star Formation
Authors: K. L. Dixon, I. T. Iliev, S. Gottlober, G. Yepes, A. Knebe, N. Libeskind, Y. Hoffman
First Author’s Institution: Astronomy Centre, Department of Physics & Astronomy, University of Sussex, Falmer, Brighton, UK
Status: Submitted to MNRAS, open access
There was a time in the universe when there were no stars. It was only after a long, dark 100 million years or so that the first stars—giant, blindingly bright monoliths a species apart from today’s stars—blinked on. As these stars blazed to life, they unleashed vast amounts of energetic ultraviolet (UV) photons. The universe at that time was filled mostly with cold hydrogen gas—cold enough to be in neutral form, single atoms of hydrogen. The UV photons unleashed by the stars changed this—they heated up the hydrogen gas and broke the atoms up into bare protons and electrons. This process was so efficient that the entire universe was reionized.
In what seems like a cosmic fluke, it appears that much of the UV photons may have come from small galaxies—those at least a thousand times less massive than the Milky Way, which we call “dwarf” galaxies. For despite their diminutive size, there were legions of them—easily a hundred, if not a thousand dwarfs for each Milky Way-mass galaxy. Thus although each dwarf produced far less UV than a larger, Milky Way type galaxy, their sheer numbers caused them to produce more UV combined than larger galaxies. Their prodigious UV output also ushered in their fall—reionization seems to have slowed or even halted star formation in dwarfs, possibly by heating up or even evaporating all the star-forming, cold gas within them.
Our own galactic neighborhood, also called the Local Group—the corner of the universe with our home galaxy, the Milky Way and our sister the Andromeda Galaxy (also known more arcanely as as M31), hosts dozens of dwarf galaxies that should have undergone precisely this. Thus the Local Group is a potentially illuminating place to look for clues as to how reionization affected star formation in dwarfs. But it’s not entirely clear what to search for. Would reionization produce dwarfs that completely stopped forming stars during reionization? Or those that only gradually kept forming stars? Should we expect stars in only the most massive dwarfs? We’re not sure.
To rescue us from this quandary are the authors of today’s paper. They took a simulation of the Local Group and an adjacent group of galaxies, the nearby Virgo Cluster, and modeled how reionization may have taken place. To take into account the fact that we don’t know how much stars and UV the dwarf galaxies produced, they ran their simulation four times, identical except for how much ionizing UV the dwarfs contributed. In the first, the dwarfs contributed nothing at all—only the largest galaxies produced stars and reionizing UV. In the second, dwarfs contributed only if they were fairly isolated, far from larger galaxies. In the third, the dwarfs also contributed when close to a larger galaxy, although with reduced output. The last simulation was identical to the third, except that the amount a dwarf’s UV output was reduced depended on its mass—more massive dwarfs were more efficient at generating UV than lower mass dwarfs.
What did they find? How early you reionized depends on how dense your corner of the universe is—Virgo, the most dense region between itself, the Milky Way, and M31, reionized first, and then was followed by M31, and then the the Milky Way, the least dense of them all. In addition, in all cases in which dwarfs contributed, Virgo, M31, and the Milky Way appeared to reionize mostly “inside out”—the galaxies within reionized themselves, and then their surroundings. Once reionization got underway in the Local Group, it quickly progressed (faster than the rest of the universe), but slowed when about half the gas was ionized. The rest of the gas was reionized externally: it picked up again when an ionizing front from outside the Group swept through (see Figure 1).
For the dwarfs, the authors found that the most massive ones generally reionized first, and that most satellites in the Local Group were ionized around the same time. But it appears difficult to determine when a Milky Way dwarf was ionized based on where it is today. In general, those that are closer to the Milky Way today appear to have formed most of their stars before reionization. Only about 20% of the dwarfs were able to form stars before reionization was complete—given that we see many low mass dwarfs that appear to have formed stars after reionization, this rules out scenarios in which dwarfs did not produce UV (and thus stars) after they came in close proximity to the Milky Way.
It’s clear that reionization was complex, that and a particular dwarf’s ability to form stars is dependent on details about its environment during reionization. Simulations that model this era of cosmic history in more detail (such as reionization due to supernovae) will help us better understand the role that dwarfs played in reionization, and how they were affected by it.
Cover image: Figure from today’s paper that shows how early the gas in the galactic neighborhood was reionized. Note that Virgo is brighter than the Local Group, indicating that the Virgo Cluster was reionized first. | 0.810235 | 4.031958 |
A Massive Meteor Impact On Jupiter
An amateur astronomer discovered something spectacular with a backyard telescope Wednesday when he recorded a bright flash on the surface of Jupiter. The biggest planet within the solar system routinely delivers stunning footage, like those snapped by NASA’s Juno spacecraft, however, the unexpected flash has astronomers excited at the possibility of a meteor impact.
Ethan Chappel pointed his telescope on the large gas planet at just the best time, catching the white spot noticed on the lower left facet of the planet within the above images on Aug. 7.
While it has but to be confirmed by a second observer, it seems like a large asteroid crashing into the gas giant planet. The flash is temporary and quickly fades away, boosting the idea that it was likely attributable to a collision.
SL9 is Comet Shoemaker-Levy 9, which famously crashed Jupiter in 1994. Hammel led the crew that used the Hubble Space Telescope to study the impact and how the planet’s gassy atmosphere responded.
Something remarkable to think about is that the apparent measurement of the flash is roughly the size of Earth, which is small next to the enormous gas planet. For reference, about three Earth could fit inside Jupiter’s Great Red Spot, which can also be visible.
Of course, this does not imply that whatever hit Jupiter was the size of a planet, just that the collision appears to have launched lots of explosive vitality. Telescope’s and Sky Bob King says, if confirmed, this could be the seventh recorded impression of Jupiter since Shoemaker-Levy. | 0.89606 | 3.179009 |
Supernovae are in the news this week, as two papers in the latest release from Nature provide fresh perspectives on stellar explosions old and new. The old one is Supernova 1987A, the closest one in the age of modern astronomy, which has recently undergone a brightening that indicates a key transition in its evolution has taken place. The new one is actually an entirely new category of supernova, represented by four examples. The output of this new category is heavily biased towards the blue end of the spectrum, it's ten times brighter than a Type Ia supernova, and we aren't sure what could possibly be powering it.
Some basic background on supernovae will make it easier to understand both stories. The initial collapse of a star creates a tremendous explosion, one heralded by the arrival of neutrinos and high-energy photons. But the fusion events that accompany the explosion also produce some unstable radioactive isotopes, such as nickel-56 and -57 and titanium-44. Both immediately after the explosion and for the following several years, the remnant of the supernova is primarily lit by energy released as these isotopes decay. Only after a few decades do other processes, primarily the interaction between the expanding shell of the explosion and the stellar environment, begin to dominate the light seen at the site of the supernova.
Supernova 1987A occurred during my second year in college, and my physics professor was so excited that he cancelled our expected lecture on Newtonian mechanics to spend an hour and a half describing why it was so exciting. That excitement was largely based on its proximity in the Large Magellanic Cloud, only 160,000 light years away, which was already close enough for detailed observations. Since then, observatories have gotten bigger and we got the Hubble Space Telescope up and working, so the situation has only improved, making SN1987A one of the best-studied supernovae around.
After about 1,500 days from the initial explosion, the supernova is expected to go into a steady decline as the half-life of 44Ti ensures that there's less and less energy being input into the remnant via radioactive decay. And observations show a decline in luminosity of the debris, which centered on the former site of the star. At about 5,000 days post-supernova (November of 2000), however, the predicted decline stopped, and the total luminosity started to rise again. By 8,000 days (April of 2009), the total luminosity was at or above where it was at 3,000 days, depending on the wavelength.
What's going on? Observations with the Hubble indicate that it's not the debris itself that is brightening. Instead, the added light comes from a ring of gas that was pushed out of the star's equator about 20,000 years ago (the ring is now about 1.3 light years across). The authors conclude that the brightening is the result of the first remnants of the supernova plowing into this ring, with the resulting collision generating X-rays that are lighting up more of the gas. This sort of behavior has been predicted for some time, but this represents the first time it has been observed.
Not everything in space is going quite according to predictions though. The fact that most supernovae are initially powered by the decay of some specific radioactive isotopes allows us to make very specific predictions about what the timing of luminosity should be. A survey of supernovae run at the Palomar Observatory has now identified four objects that don't fit the expected pattern. A study of the light that came off these events show that they all share common properties.
One of them is that their luminosity is heavily biased to the UV portion of the spectrum, and they're unusually bright. To get the luminosity from the decay of 56Ni, the explosion would have had to produce several solar masses of that alone. The decline in luminosity is also much faster than we'd expect based on half lives of the common isotopes. "These are therefore not radioactively powered events," the authors conclude. To be a product of the explosion itself would require what they term "an unrealistic total explosion energy."
Finally, the spectrum of the light seems to indicate the light is coming from material that is extremely hydrogen-poor, which rules out some form of a rapid collision analogous to the one observed in SN1987A.
So, just about all of our common expectations about supernovae aren't working out. The authors suggest two possible explanations. One is the explosion of a star of over 90 solar masses, which will often expel a hydrogen-poor shell shortly before dying. If the time difference between this expulsion and the explosion is short enough, debris will impact the shell days after the explosion itself, creating the effect seen here. The alternative is that the remains of the star are injecting energy into the debris. This could happen if these supernovae produced a rapidly spinning magnetar.
The Palomar team has identified four of these items in about two years of observations, so it's possible that we'll be able to spot a few more and get a better sense of what's happening. Otherwise, we may have to wait a bit to get lucky enough to observe one from a shorter distance. | 0.858088 | 3.993751 |
Everybody gets a moon! With the discovery of a small moon orbiting the third-largest dwarf planet, all the large objects that orbit beyond Neptune now have satellites.
Trans-Neptunian objects (TNOs) spend most or all of their orbits beyond Neptune. Last April, the dwarf planet Makemake became the ninth of the ten TNOs with diameters near or above 1,000 kilometres known to have a moon.
So when dwarf planet 2007 OR10 was found to be rotating more slowly than expected, it was suspected that a moon might be the culprit. To try to find it, John Stansberry at the Space Telescope Science Institute in Baltimore, Maryland, and his colleagues went back to the Hubble Space Telescope archives and found eight images of the world from 2009 and 2010.
“We basically just stretched the images a lot harder than the people who originally took the data, and there was a moon,” says Stansberry. The moon was in every image. The team presented these results at a planetary sciences meeting in October and now in a paper.
The discovery of moons around all the largest TNOs gives us a window, not just into the objects themselves, but also into our solar system’s history. TNOs are relics from the era of planet building, so they present an opportunity to peer into the past.
A moon of one’s own
The moons around each of these relatively small worlds probably formed when a large rock collided with the parent body and the debris coalesced in orbit. The fact that every large TNO has a moon points towards a crowded, chaotic past.
“Today, those objects are fairly rare and them hitting each other is improbable,” says Scott Sheppard at the Carnegie Institution for Science in Washington DC. “That means the environment there must have been much more dense: there must have been 10 or 100 times more objects out there in the past than there are now.”
Astronomers hope to take more images of 2007 OR10 to catch further glimpses of its satellite, as measuring the moon’s orbit can tell us more about the dwarf planet and the early solar system.
“Knowing the mass and density tells you something about how much rock and ice is in the interior, which can tell you things about the gas chemistry in the protosolar disc,” says Stansberry.
Journal reference: arXiv, DOI: arXiv.org/abs/1703.01407
More on these topics: | 0.879122 | 3.66724 |
A Maunakea telescope observing distant stars detected a stellar flare estimated to be 10 billion times more powerful than any solar flare from our sun.
The James Clerk Maxwell Telescope observed a powerful stellar flare — a burst of plasma and electromagnetic radiation — in November 2016 from a star 1,500 light-years from Earth, but the data was not found and analyzed until August of last year.
Solar flares are a not unusual phenomenon that are sporadically observed on our own sun.
“The average solar flares on our sun are pretty dramatic,” said astronomer Steve Mairs, lead investigator of the team that discovered the flare. “There are stories of telephone lines exploding because of flares in the past.”
However, Mairs said that because the 2016 stellar flare was detectable from so far away, the flare is thought to be unimaginably more powerful — releasing 10 billion times more energy — than any flare from our solar system’s star.
The discovery of the flare could lead to a better understanding about the process of stellar formation, Mairs said.
The flare emanated from a point in the Orion Nebula, which is the closest region of massive star formation to Earth, Mairs said. From this, Mairs said the source of the flare was likely a very young star in the process of forming.
Although the flare was discovered in 2016, it actually occurred approximately 1,500 years ago, with the light from the flare only reaching Earth three years ago. Despite this, Mairs said the star is still very young, cosmically speaking, as stars take more than 10 million years to fully form.
Mairs said the cause of the flare is speculated to be a powerful magnetic field funneling matter into the growing star. As the star formed, the magnetic field became distorted and briefly “snapped” and reconnected, releasing an extraordinary amount of energy.
Mairs said similar “snaps” have been observed in the past, but none at the scale of energy observed from the 2016 flare. The James Clerk Maxwell Telescope observes electromagnetic wavelengths of less than a millimeter; similar events in the past occurred at longer wavelengths, indicating less energy involved.
“One of the questions we have about star formation is ‘how do stars get all that mass?’” Mairs said. “Is it like a smooth process like a buffet, where you just get more and more matter as time goes by? Or does it happen in spurts, where you get a lot of mass at once and then nothing happens for a while, like a 12-course meal?”
The 2016 flare suggests star formation is more like a 12-course meal, Mairs said, and similar events might occur when stars “feast” on new matter.
The star that discharged the flare is thought to eventually become a star not too dissimilar from our own sun, Mairs said, aside from the fact that it exists in a binary system, revolving in tandem around a second star. However, Mairs assured that our star, a fully-developed star at roughly the center of its lifespan, is unlikely to produce a flare of any magnitude close to the 2016 flare.
Further investigation into similar events will hopefully lend further insights into star formation, Mairs said.
“We want to figure out how often this happens,” Mairs said. “We weren’t really looking for this one, we were just looking in the right direction.”
Email Michael Brestovansky at [email protected]. | 0.860268 | 4.036216 |
› In June 2015, Mars will pass almost directly behind the sun from Earth's perspective, a geometry called Mars solar conjunction.
› Mars solar conjunction happens about every 26 months.
› Because the sun disrupts radio transmissions between Earth and Mars during conjunction, communications are curtailed.
In June 2015, Mars will swing almost directly behind the sun from Earth's perspective, and this celestial geometry will lead to diminished communications with spacecraft at Mars.
The arrangement of the sun between Earth and Mars is called Mars solar conjunction. It occurs about every 26 months as the two planets travel in their sun-centered orbits. The sun disrupts radio communications between the planets during the conjunction period. To prevent spacecraft at Mars from receiving garbled commands that could be misinterpreted or even harmful, the operators of Mars orbiters and rovers temporarily stop sending any commands.
The teams running NASA's three active Mars orbiters and two Mars rovers will refrain from sending commands to their spacecraft from about June 7 to June 21. During that period, the sun will be within two degrees of Mars in Earth's sky. (Don't try to look, though, because looking at the sun is dangerous to the eyes.) The operators also will put restrictions on commanding -- such as using only reduced data rates or communicating only in an emergency -- during the days before and after that period.
Spacecraft will continue making some science observations during the conjunction period, though rovers will not do any driving or arm movements.
"Our overall approach is based on what we did for the solar conjunction two years ago, which worked well," said Nagin Cox, a systems engineer at NASA's Jet Propulsion Laboratory, Pasadena, California, who is leading conjunction planning for NASA's Curiosity Mars rover. "It is really helpful to have been through this before."
NASA's MAVEN spacecraft, which arrived in Mars orbit last September, will be experiencing its first solar conjunction. Its team has prepared thoroughly. MAVEN -- short for Mars Atmosphere and Volatile Evolution -- will continue monitoring the solar wind reaching Mars and making other measurements. "The data will be stored and transmitted back to us after communications are reestablished at the end of the solar conjunction period," said James Morrissey, MAVEN deputy project manager at NASA's Goddard Space Flight Center, Greenbelt, Maryland.
Transmissions from NASA's two other Mars orbiters -- Mars Odyssey and Mars Reconnaissance Orbiter -- will continue through the conjunction period, but some of those transmissions are not expected to reach Earth. Science data transmitted during conjunction will also remain stored aboard the orbiters, for reliable retransmission in late June. The active Mars rovers -- Curiosity and Opportunity -- will send limited data to orbiters throughout conjunction for relay to Earth during and after conjunction.
Mars Odyssey, which reached Mars in 2001, will be in its seventh solar conjunction. For Opportunity and Mars Reconnaissance Orbiter, the 2015 solar conjunction is the sixth and fifth, respectively.
In preparation for conjunction, orbiter and Curiosity mission teams have been clearing some science data from spacecraft memories to optimize availability of memory for storing science data during the conjunction period. Data that Opportunity collects and sends daily to orbiters will be kept on the orbiters for replay after conjunction. No conjunction-period data from Opportunity will be kept on the rover. Opportunity will operate during conjunction in a mode avoiding use of non-volatile flash memory, the type of memory that can retain data when the rover powers down overnight.
A video showing Mars solar conjunction geometry is at:
NASA's five current missions at Mars are preparing the way for human-crewed missions there in the 2030s and later, in NASA's Journey to Mars strategy.
NASA's Goddard Space Flight Center manages the MAVEN project for the principal investigator at the University of Colorado, Boulder, and for the NASA Science Mission Directorate, Washington. JPL, a division of the California Institute of Technology in Pasadena, manages the Odyssey, Reconnaissance Orbiter, Opportunity and Curiosity projects, and NASA's Mars Exploration Program, for the Science Mission Directorate. Lockheed Martin Space Systems, Denver, built all three NASA Mars orbiters. For more about NASA's Mars Exploration Program, visit:
News Media ContactGuy Webster
Jet Propulsion Laboratory, Pasadena, Calif. | 0.828673 | 3.512603 |
Scientists at Brown University wanted to find out. So, they did what any one of us would do and built an indoor asteroid cannon — with a lot of help from NASA.
The resulting study, published April 25 in the journal Science Advances, may sound ridiculous (or ridiculously awesome), but it aims to answer some of the most persistent questions in the science of planet formation. How did initially bone-dry planets get their water in the earliest days of the solar system? Why were traces of water discovered in the mantle of Earth’s parched moon or near the massive Tycho lunar crater? Can ancient, carbon-based asteroids work as a trans-galactic taxi service, shuttling little pools of water from one part of the cosmos to another?[When Space Attacks: The 6 Craziest Meteor Impacts]
If that latter theory is true, the math is not on its side. “Impact models tell us that [asteroids] should completely devolatilize at many of the impact speeds common in the solar system, meaning all the water they contain just boils off in the heat of the impact,” study co-author Peter Schultz, a professor in Brown’s Department of Earth, Environmental and Planetary Sciences, said in a statement. “But nature has a tendency to be more interesting than our models, which is why we need to do experiments.” | 0.90294 | 3.060085 |
to be unfit for such employment. There are no doubt reasons for this distinction, whether conclusive or not, but the classification is by no means above criticism, for within our own time Astronomy has been taken out of the category of the established or perfect sciences, and may be now cited as one of the best illustrations of a progressive science. Of course, there are established truths in Astronomy, and so there are in Chemistry and Physics, but Astronomy has now assumed a new character of progressiveness, and within the present generation it has surpassed all the other sciences in the rapidity and splendor of its advancement.
Not so many years ago it seemed as though astronomy were approaching, if it had not already reached, its final stage. The Sun and his family had been measured and weighed, the Moon tracked in all her motions, and the paths of comets determined. The younger Herschel had completed the survey of the heavens, which his father commenced, and, to all seeming, little remained to be ascertained about the universe. And yet, in the presence of the astronomy of our day, that of a few years ago looks crude and elementary. Newton made an epoch by bringing the movements of the planetary bodies under the demonstrated laws of terrestrial force; Kirchhoff and the spectroscopists have made a new era by subordinating stars, comets, and nebulae, to the laws of terrestrial chemistry. The recent physical explorations of the sun constitute one of the most thrilling chapters in all science. Nor have astronomers been content with the unquestioned acceptance of the older views respecting the planetary scheme. Not Ptolemy alone, or Hipparchus, Galileo, Kepler, and Newton, but even the elder and younger Herschel, would stand aghast at the change of opinion that has been wrought regarding the members of the solar system. Jupiter and Saturn, so long considered as merely large specimens of habitable worlds, have taken their place in a higher order of orbs, while satellites, formerly thought to be set as lights to illumine their primaries, have been raised almost to the dignity of planets. Even more surprising have been the discoveries made respecting comets and meteors, while modern inquiries have not stopped short of the domain of the so-called fixed stars, so that the whole scheme of the stellar universe begins to present a new aspect.
Astronomical science, in short, has been enlarged and reshaped in the nature and scope of its problems, and has entered into a new epoch in our own time which opens to us even a grander future than was disclosed either to Copernicus or to Newton.
As was quite unavoidable, this recent revolution or extension of the science has left behind the old teachers, and created a demand for new men, who can deal with the subject in its more novel and extended aspects. And, as supply follows demand in the intellectual as well as the commercial world, the expounders of the new dispensation | 0.848491 | 3.23129 |
A set of five newly identified exoplanets rotating close to the stars has been detailed in a new study.
The important part of the discovery is two potentially habitable super-Earth planets that are ideal nominees to analyze further as scientists are looking for life outside our Solar System, as per the research team.
Two planets dubbed GJ 180 d and GJ 229A c, weighting 7.5 and 7.9 times the size of Earth, respectively, are located at respective distances of 40 light-years and 19 light-years from our planet.
They both rotate around red dwarf stars, which, overall, is believed not to be a good sign for probable life. That is due to the fact that these kinds of stars use to be rather rough, scourge their vicinity with flare activity and radiation. However, this is not a definite downer, but it depends on the star because some are not so violent.
Is It Actually a Potentially Habitable Place?
A second big issue here is that red dwarfs are rather cooler than the majority of main-sequence stars. Therefore, their Goldilocks zone, where temperatures are useful to liquid water on the surface of a planet, is placed rather close to the star.
This, then, means that planets in that area are more susceptible to tidal locking, where one part of the object is always facing the star, and the other is not. This makes one part of the planet incredibly hot and stellar radiated in a continual manner, while the other side is held in cool darkness.
GJ 180 d has a rotating timeline of 106 days, and the team of researchers theorizes that this particular planet is sufficiently far from its star, Gliese 180, so it would not be tidally locked.
“GJ 180 d is the nearest temperate super-Earth to us that is not tidally locked to its star, which probably boosts its likelihood of being able to host and sustain life,” said astronomer Fabo Feng of the Carnegie Institution for Science.
In the meantime, GJ 229A c has a rotating period of 122 days, but its star, Gliese 229A, is bigger than Gliese 180, so this planet might be tidally locked.
The Black Sheep of the Universe
There is something else that’s pretty amazing about the star; more precisely, Gliese 229A is in a binary system with a brown dwarf star, Gliese 229B. These cosmic bodies are, at times, called ‘failed stars,’ which means they are too massive to be a planet but too small to merge hydrogen in their nucleus.
They take shape in an identical way the stars do, from the gravitational crash of a clump of gas, contrary to the slow accretion process that gives life to planets. However, it is not clear if they can host planets.
The planets were identified using an indirect method, known as radial velocity. Even though it may not seem so, planets rotating a star have a gravitational impact on that star, making it ‘wobble’ a bit as the planet pulls it.
Due to the fact that these particular systems are in close proximity, the scientists suggest that the next generation of advanced telescopes could ultimately provide them with direct images of these objects; therefore, helping them better understand whether the planet has an atmosphere or even water, and so on.
“Our discovery adds to the list of planets that can potentially be directly imaged by the next generation of telescopes,” Feng said. “Ultimately, we are working toward the goal of being able to determine if planets orbiting nearby stars host life.”
The paper has been published in The Astrophysical Journal Supplement Series.
Paula is an outstanding reporter for Henri Le Chat Noir, always finding new and interesting topics to bring to the portal. She mostly crafts Science and Technology news articles, covering everything one needs to know about those niches. Paula studied at Concordia University. | 0.835217 | 3.84447 |
The oldest solid material ever found on Earth has been discovered in a meteorite that fell in Australia nearly five decades ago. Researchers at the University of Chicago have been studying the material for about 30 years and recently determined that a sample was about 5 billion to 7 billion years old. Their findings been published in the peer-reviewed Proceedings of the National Academy of Sciences.
Meteorites can act like time capsules of the materials trapped within them. The material that the researchers examined are called presolar grains, or stardust, which are formed when a star dies. Stars are born when gas, dust and heat combine just right and can exist for millions or even billions of years before dying. When it dies, the presolar grains are ejected into space. Presolar grains are extremely rare, found in only about 5 percent of meteorites that have fallen to Earth.
A team of researchers from the U.S. and Switzerland analyzed 40 pre-solar grains contained in a portion of the Murchison meteorite, which fell in Murchison, Victoria in 1969. The researchers used a particular form (isotope) of the element neon – Ne-21 – to measure how long the grains had been exposed to cosmic rays in space. Based on the results, most of the grains had to be 4.6-4.9 billion years old, with the oldest dated around 7.5 billion years old.
Previously, the oldest pre-solar grain dated with neon isotopes was around 5.5 billion years old. For comparison, the Sun is 4.6 billion years old and the Earth is 4.5 billion. Philipp Heck, lead author of the study and associate professor at the University of Chicago, said, “It’s so exciting to look at the history of our galaxy. Stardust is the oldest material to reach Earth, and from it, we can learn about our parent stars, the origin of the carbon in our bodies [and] the origin of the oxygen we breathe. With stardust, we can trace that material back to the time before the sun.” | 0.842528 | 3.517533 |
When the Earth Had Two Moons
Cannibal Planets, Icy Giants, Dirty Comets, Dreadful Orbits, and the Origins of the Night Sky
An astonishing exploration of planet formation and the origins of life by one of the world’s most innovative planetary geologists.
In 1959, the Soviet probe Luna 3 took the first photos of the far side of the moon. Even in their poor resolution, the images stunned scientists: the far side is an enormous mountainous expanse, not the vast lava-plains seen from Earth. Subsequent missions have confirmed this in much greater detail.
How could this be, and what might it tell us about our own place in the universe? As it turns out, quite a lot.
Fourteen billion years ago, the universe exploded into being, creating galaxies and stars. Planets formed out of the leftover dust and gas that coalesced into larger and larger bodies orbiting around each star. In a sort of heavenly survival of the fittest, planetary bodies smashed into each other until solar systems emerged. Curiously, instead of being relatively similar in terms of composition, the planets in our solar system, and the comets, asteroids, satellites and rings, are bewitchingly distinct. So, too, the halves of our moon.
In When the Earth Had Two Moons, esteemed planetary geologist Erik Asphaug takes us on an exhilarating tour through the farthest reaches of time and our galaxy to find out why. Beautifully written and provocatively argued, When the Earth Had Two Moons is not only a mind-blowing astronomical tour but a profound inquiry into the nature of life here—and billions of miles from home. | 0.869693 | 3.301345 |
A group of researchers at the University of California, investigates how to harness the power of light to get to Mars after a journey of just 3 days. It sounds like science fiction, but the technology could become reality, NASA scientists says.
Using today’s technology, it will take about five months to reach the red planet, a cumbersome obstacle in traveling that implies many others impediments. But now, NASA may have come up with something. The key is photon propulsion (also called DEEP IN, or Directed Propulsion for Interstellar Exploration). So what is photonic propulsion exactly?
According to scientists, it is a technique that uses powerful laser that could push a spacecraft through space at incredible speeds — closer to the speed of light, or relativistic speed.
NASA scientist Professor Phillip Lubin and his team are working on the DEEP IN program and has presented his findings at the last NIAC Symposium (NASA Innovative Advanced Concepts).
We know how to get to relativistic speeds in the lab, we do it all the time,
There are recent advances that take this from science fiction to science reality. There’s no known reason why we cannot do this.
So, how this technology Works? The theory is simple. Despite not having any mass, photons or light particles have both energy and momentum that can be transformed into a “push”. So, we could use thrust of photons to propel objects like a spacecraft into space. Based on calculations, this technique could propel 100 kilograms robotic craft to Mars in just 3 days, Lubin said.
When they reflect off an object, that momentum is transferred into a little push. With a large, reflective sail, it’s possible to generate enough momentum to gradually accelerate a spacecraft,
With what spacecraft uses at present, burning rocket fuel is the only means to launch a rocket ship. Rocket fuel, however, can weigh down the spacecraft and it is more inefficient compared to electromagnetic acceleration.
On the other hand, the photonic propulsion uses a stream of photons that does not add mass to the spacecraft beyond the laser itself. The system can also be used to deflect hazardous space debris, as the authors wrote in the paper.
These systems can be propelled to speeds currently unimaginable with existing propulsion technologies. To do so requires a fundamental change in our thinking of both propulsion and in many cases what a spacecraft is,
the paper said.
However, this system would not be used for manned flights. “We are not proposing systems to send humans to interstellar distances.” Humans are extremely fragile and require a lot of support. Robotic missions are much better suited for interstellar exploration in the future.”
Within about 25 light-years of the Earth, there are actually quite a few potential exoplanets and habitable things to visit,
Lubin said at the NIAC symposium.
There are many targets to choose from.
DEEP IN has the potential to bring other stars into reach.
Exploring the nearest stars and exoplanets would be a profound voyage for humanity, one whose nonscientific implications would be enormous,
Lubin wrote on the topic.
It is time to begin this inevitable journey beyond our home. | 0.801836 | 3.660869 |
STARS, GALAXIES AND THE UNIVERSE Types of Telescopes Telescope literally means far seeing, from the Greek words tele meaning far and skopein meaning to see or to look. The word telescope most usually refers to optical telescopes that receive the visible wavelengths of light. There are also sophisticated telescopes that receive wavelengths from other parts of the electromagnetic spectrum, such as infrared and X-ray radiation. There are several types of optical telescopes. • Refracting telescopes receive light through a lens and the image is then viewed through an eyepiece. • Reflecting telescopes reflect light off a series of mirrors. The image is then viewed through the eyepiece. • Catadioptric telescopes use a combination of lenses and mirrors to gather light and focus the image for viewing. • Refracting (top image below) and reflecting (bottom image) optical telescopes are the most common. Unfortunately air pollution, generated light, and the atmosphere itself all interfere with the ability to clearly view the stars. • Our atmosphere makes stars look fuzzy. • Pollution and humidity make it difficult to see the stars. • Light pollution makes it more difficult to see distant lights from the skies. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
The best images from land-based optical telescopes, therefore, are from telescopes that are on mountaintops stationed far away from other human activity where the atmosphere is thinner and extraneous light does not obscure the view. Beyond Earth’s Atmosphere Because the atmosphere, even at high altitudes, refracts light from stars and planets, the best images come from telescopes outside the Earth’s atmosphere. Another physical reality is that some electromagnetic radiation cannot be detected on Earth. For example, X-ray telescopes must be outside the Earth’s atmosphere because the atmosphere blocks X-rays from reaching the Earth. The Chandra X- ray telescope, pictured here, is one example. To get the clearest view of the universe, one must get beyond Earth’s atmosphere and use space-based telescopes. It may be very surprising to discover that some of the most basic information about our universe has been discovered very recently using space- based telescopes. In 1990, the Hubble © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Space Telescope (named in honor of the great 20th century astronomer Edwin Hubble) was launched by NASA and has provided some of the most spectacular images of the universe ever seen. Despite a number of technical troubles, the Hubble telescope (shown in flight) has provided some of the most important images of stars, planets, and other phenomena in space. Characteristics of Stars From ancient times, observers of the sky have noticed that stars are different from one another. Some are brighter. Some are bluish. Some are red. Ancient astronomers attempted to categorize stars based on their brightness. Simply standing under the night sky and observing what they could see with their eyes, they would describe their characteristics and categorize them accordingly. One of the easiest characteristics to observe is the star’s brightness. Today we know that a star’s brightness depends in part on its distance from the Earth. How bright a star appears to look to any observer on Earth is called the star’s apparent magnitude. It is the apparent magnitude because the stars are all at different distances from the Earth. A star that is 100 light years away will appear to have a certain brightness. That same star, if it were 1,000 light years away, would appear to be less bright. On the other hand, if all stars were lined up at the same distance from the Earth, and then the individual brightness of each was measured, the measured brightness would be called the absolute magnitude. Stars have been classified based on a scientific basis since the 1800’s. Since then they have been classified based on the elements determined to be in the stars. The elements in stars are identified by an instrument called a spectrometer. The spectrometer breaks incoming light (electromagnetic radiation) into all the individual wavelengths contained in that light. Spectrometers produce light emission patterns. The light emission pattern produced by a spectrograph indicates which elements are present in a particular star. Based on such information, astronomers have discovered that there are a number of different types of stars in the universe. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
The Lives and Deaths of Stars The colors of stars give an indication as to the relative temperature of that star. Red stars are cooler. Blue stars are hotter. The colors also indicate the relative age of the star. Blue stars are extremely massive stars that rapidly consume their hydrogen. Consequently they are also extremely hot stars. They do not live long by comparison to other stars. When their hydrogen is gone, they expand and become red giants. A red giant is a star that has consumed all its hydrogen. After this occurs, its core shrinks and its surface expands. Such a star is very cool by comparison to other stars. A red giant is, therefore, an older star. If giant stars grow to be exceptionally large, they are referred to as supergiants. After a blue star has consumed its hydrogen, it can explode in a violent flash. Heavy elements like lead, gold, and silver are created by this explosion. This is literally the death of the star. Astronomers call this phenomenon a supernova. This NASA image (below) shows the remains of a supernova explosion. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Small, very hot stars that were once the center of younger stars are actually dying stars. They are known as white-dwarf stars. No nuclear fusion takes place in white-dwarf stars. They shine due to their residual heat. The oldest stars in the universe are red-dwarf stars. They are low mass stars and burn for an extremely long time. Sun compared to red-dwarf star There are yet other types of stars. For example, a neutron star is the remains of a massive star that has collapsed on itself. A neutron star that is spinning is known as a pulsar. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
As astronomers study stars, what they see may in reality no longer exist. Much of what we observe in the universe happened before the Earth and even our solar system formed. But it happened so far away that it has taken billions of years for the light to travel through space and reach the Earth. So what we see now occurred in real time millions, and in some cases billions, of years ago. Star Systems and Galaxies Stars do not just exist randomly throughout the universe. They are clustered in large groups. Large groups of stars in space are called galaxies. Our galaxy is called The Milky Way (pictured here). Astronomers estimate that there are from 200 billion to 400 billion stars in the Milky Way. Galaxies are defined based on their appearance. The Milky Way is a particular type of galaxy known as a spiral galaxy. A spiral galaxy is disc-shaped and has a spiral form, much like a hurricane. There are a variety of other galaxies that are described based on their shape such as irregular galaxies and elliptical galaxies. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
It is estimated that about 33% of the galaxies are large, rounded groupings of stars. There is little gas in these galaxies so new stars are not forming. These galaxies are known as elliptical galaxies. Within galaxies are groups of stars, gas clouds and other features. A gas cloud in a galaxy in which stars can form is called a nebula. NASA image of the Eagle Nebula There are groups of older stars that look like a ball of stars within galaxies. These groupings are known as open clusters. Astronomers believe that quasars are galaxies that are beginning to form. Astronomers know that quasars are very far away and, because they are so bright, must be among the most powerful sources of energy in the universe. The Expanding Universe. Is it? The Big Bang Theory postulates that the universe began with the massive explosion of space itself. If the universe began with an explosion centered in a particular place, it would be logical to conclude that the universe is expanding, that is, the material in the universe is continually moving away from its point of origin. There is quantitative evidence to support this theory. At one time, scientists believed that other galaxies are moving away from ours. More recently, however, very careful measurements have shown that all the galaxies are actually moving away from each other. It is thought that the universe will continue to expand like this until it gets colder and darker and then eventually “dies.” This is based on the assumption that there is not enough matter in the universe and therefore not enough gravitational pull to slow this expansion. In actuality, scientists don’t know for certain what the fate of the universe will be. It is also possible that there is so much matter in the universe that the gravitational pull between planets, stars, and other bodies will slow the expansion and eventually pull all matter together into a single mass. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com. | 0.850847 | 3.375405 |
Understanding Saturn, its rings, and its moons: The Cassini-Huygens Mission
The Cassini-Huygens spacecraft is a dual orbiter (Cassini) and lander (Huygens) currently orbiting Saturn. It launched from Cape Canaveral on October 15, 1997, entered orbit around Saturn on the July 1, 2004, and has been studying the Saturnian system ever since. After two mission extensions, and a grand total of almost 13 years orbiting the giant gas planet, Cassini-Huygens’ mission is now coming to a close. The European Space Agency (ESA) built and operated the Huygens lander, which flew with the Cassini orbiter out to Saturn. Over that time, it has become one of the most successful missions in NASA/ ESA history, redefining our understanding of Saturn, its rings, and its moons. As the mission enters its final phase, we look back over where it has been, and what it has accomplished.
Saturn is far away and difficult to get to; you can’t just fly directly at it. After launch in 1997, Cassini-Huygens performed gravity assist maneuvers at Venus in April 1998 and June 1999, Earth in August 1999, and then Jupiter in December 2000. Each gravity-assist gave the spacecraft an extra kick of velocity, so it could reach Saturn in just under 7 years of flight time. Captured by Saturn’s gravitational field, it officially entered into orbit on July 1, 2004. But even before becoming the first spacecraft to orbit Saturn, it had already taken pictures of asteroid 2685 Masursky, made a better characterization of Jupiter’s bands, and discovered two new Saturnian moons: Methone and Pallene.
One of the first things Cassini-Huygens did upon arrival at the Saturnian system was to study its largest moon, Titan. As a result of Saturn flybys by Pioneer 11 and the Voyager probes in the late 1970s and early 1980s, planetary scientists had already confirmed the presence of an atmosphere on Titan composed of nitrogen and methane. Coupled with observations by the Hubble Space Telescope in 1995, they were also confident the conditions were right for liquid methane to exist on the surface in large quantities, such as lakes or oceans. No other moon in the solar system has an atmosphere, and there is no other place with liquids on its surface than Earth. Because of this, Titan was made a scientific priority for the Cassini-Huygens mission.
Huygens landed on Titan on the January 14, 2005, the first spacecraft to land on a body in the outer solar system. It gathered and relayed data back to Cassini during descent and for approximately 90 minutes on the surface. Eventually Cassini went out of range, and not long after Huygen’s batteries failed. From the images related back, it appears Huygens landed on a surface with a mud-like consistency, however, there was no evidence of large bodies of liquid nearby. In subsequent flybys, Cassini confirmed that Titan does, in fact, have massive lakes of methane concentrated near the northern polar region. The combined efforts of Cassini and Huygens have shown there is a full methane cycle on Titan: it evaporates, rains, and freezes.
A better understanding of Enceladus is one of Cassini’s greatest contributions to our understanding of the solar system. Enceladus is an ice-moon, with a surface entirely covered with thick water ice. Close flybys of the moon by Cassini revealed massive geysers erupting large amounts of liquid water hundreds of kilometres into space from the south pole of the moon. Along with other measurements, this confirmed Enceladus also has a massive ocean of liquid water below its ice surface. In fact, there is more water on Enceladus than there is on Earth. Most recently, Cassini detected molecular hydrogen in the water plumes as the spacecraft flew through one of the active geysers. This is important, because the presence of molecular hydrogen indicates the water is reacting with rocks at the bottom of Enceladus’ ocean via hydrothermal processes (such as a hydrothermal vent). This firmly places Enceladus as one of the best locations to focus a search for life elsewhere in the solar system.
The Ring System
The rings of Saturn have been studied since Galileo pointed his telescope and called them “the ears of Saturn.” We now know they are composed of billions of chunks of water ice ranging in size from 1 cm to 10 m, stretching from about 8,000 km to 80,000 km from the cloud-tops of Saturn, while remaining only about 1 km thick. That’s impressively thin; relatively speaking, thinner than a piece of paper!
Under the scrutinous eyes of Cassini’s cameras, the rings have proven to be much more complex than originally realized. For example, while the Voyager probes discovered the Keeler Gap, a 42 kilometre gap within the A ring of Saturn, Cassini discovered the moon Daphnis within that gap. The gravitational effect of the moon not only creates the gap, but also creates beautiful ripple effects at the ring edges. It is likely that most of the gaps in the rings of Saturn, big or small, are created by tiny moonlets gravitationally carving out their orbit.
Cassini also has discovered multiple propeller-like features in the rings likely caused by even more small moonlets, similar to the way Daphnis creates ripples on either side of the Keeler Gap. The “Bleriot propeller,” named after the French aviator, is the largest of these features, and was recently imaged by Cassini during its Grand Finale phase.
While the list above is plentiful we have yet to start on Cassini’s work regarding Saturn itself. Cassini’s primary mission ended after 4 years, but was extended twice: once in 2008, the “Equinox Mission” and again in 2010, the “Solstice Mission.” Saturn’s orbit around the Sun takes about 30 Earth years; thus Cassini has observed the planet roughly half of its year. This has enabled long term observations of seasonal changes to the planet. For example: the hexagonal vortex at the north pole. Now, the hexagon itself was discovered by the Voyager probes in 1981; and, with the help of Cassini, researchers are still trying to figure out why the winds are turning at sharp angles. However, over the 13 years Cassini has been observing, the hexagon has changed colour from blue to gold. This is likely linked to the north pole receiving more sunlight and creating haze during the northern hemisphere’s summer solstice.
Cassini was also able to observe the semi-periodic white storm known as the Great White Spot. The spacecraft observed its emergence in December 2010, which slowly wrapped around the entire planet and then engulfed itself in August 2011. After Cassini made observations of its full cycles, scientists were able to propose a cause of the Great White Spot: before a storm can start again on Saturn, a large amount of cooling is required.
Cassini’s perhaps most famous image is entitled “The Day the Earth Smiled,” taken when Cassini had maneuvered itself into opposition, with the Sun and Cassini exactly opposite each other in the sky from Saturn’s point of view. The unique locale allowed Cassini to image Saturn backlit: by the Sun. Earth and its moon were caught in the shot, along with Mars, and a handful of other things. This was the third time in history that Earth had been imaged from the outer solar system.
The Grand Finale
Having been flying for almost 20 years, it’s hard to remember a time without Cassini and Huygens. Unfortunately, Cassini has a dwindling fuel supply that it uses to correct its orbit. If it were to run out, the spacecraft would effectively become “dead in the water.” However unlikely, a dead spacecraft could accidentally crash into the ice-moon Enceladus or the “early-Earth” Titan, and possibly contaminate those worlds with Earth bacteria. In order to conserve the pristine environments of those moons, the Cassini-Huygens staff have decided to end the mission by crashing it into Saturn itself, where it will burn up in the upper atmosphere. But before doing so, they have planned 22 orbits that pass through the gap between Saturn and its rings, a place no spacecraft has ever been. These orbits are set up to help answer questions such as, how much mass is in the rings of Saturn? And, what is the true rotation rate of Saturn? Fundamental questions that have gone unanswered. | 0.801558 | 3.918955 |
Exoplanets are almost old hat to astronomers, who by now have found more than1,000 such worlds beyond the solar system. The next frontier is exomoons—moons orbiting alien planets—which are much smaller, fainter and harder to find. Now astronomers say they may have found an oddball system of a planet and a moon floating free in the galaxy rather than orbiting a star.
The system showed up in a study using micro lensing, which looks for the bending of starlight due to the gravitational pull of an unseen object between a star and Earth. In this case the massive object might well be a planet and a moon. But the signal is not very clear, the researchers acknowledge, and could instead represent a dim star and a lightweight planet. “An alternate star-plus-planet model fits the data almost as well” as the planet-plus-moon explanation, the scientists reported in a paper that was posted this week on the preprint site arXiv. The study has not yet been peer-reviewed.
“I was excited by this paper,” says astronomer Jean Schneider of the Paris Observatory, who was not involved in the research. Exomoons have “become fashionable these days,” he adds, and are one of his personal “holy grails.” Schneider wrote a paper in 1999 on how to detect exomoons using an alternative method, called transiting. (The transit technique looks for the dimming of a star’s light caused when a planet or moon passes in front of the star from Earth’s perspective).
Now that astronomers know planets are common in the galaxy, exomoons, too, are likely to abound, scientists say. Yet they are exceedingly hard to find, due to their diminutive size and lack of brightness. The authors of the new paper, led by David Bennett of the University of Notre Dame, note that micro lensing is promising because it can detect moons beyond the close-in satellites that transit searches are best equipped to find. Regardless of whether the new system turns out to include a moon, “these results indicate the potential of micro lensing to detect exomoons,” the authors wrote.
Micro lensing is a type of gravitational lensing, an effect on light predicted by Albert Einstein’s general theory of relativity. According to Einstein’s theory, massive objects warp the spacetime in their vicinity, so that anything, even light, will take a curved path around them. When light from a background star travels past a massive object on its way to our telescopes, it manifests in bright circles of warped light called Einstein rings. If the massive object consists of two bodies, such as a planet and its moon, the circle will appear broken and bulgy in places. Sometimes the ring is too small to resolve the details, but the overall micro lensing effect can be calculated by the way the star’s overall brightness varies in time.
Bennett and his colleagues have identified a two-body system, which they designate MOA-2011-BLG-262, from micro lensing data collected at the Mount John University Observatory in New Zealand and the Mount Canopus Observatory in Tasmania. But the researchers cannot be sure which two bodies caused the brightness fluctuations. The explanation that best fits the data is a giant planet, about four times the mass of Jupiter, orbited by a moon weighing less than Earth. If that interpretation is correct, the planet and its moon would be relatively nearby, between 1,000 and 2,000 light-years from Earth, and would be adrift in the Milky Way rather than part of a system circling one of the galaxy’s stars. Scientists think such free-floating objects might be relatively common, because gravitational interactions between multiple planets in a system can eject one or more of the planets entirely, perhaps with a moon in tow.
Another possibility is that the researchers have detected a more distant system comprising a small star, around one tenth the mass of the sun, and a planet roughly 18 times as massive as Earth. This system would need to be much farther away to explain the micro lensing pattern.
Unfortunately, there is no chance for astronomers to take another peek at the object to confirm their suspicions, because it has moved out of alignment with the background star and now produces no lensing signal. This is “the most frustrating aspect” of the find, Schneider says, and is “common to all detections by micro lensing.”
On the bright side, he says, the discovery has brought numerous surprises. It has highlighted the potential of micro lensing at a time when most of the field is focusing on the transit method, and it has potentially revealed a free-floating system whereas astronomers have mainly been looking for moons orbiting planets around stars. “It forces us,” Schneider says, “to be always open-minded.” | 0.846992 | 3.92507 |
Mars at opposition, October 13, 2020
by Jeffrey L. Hunt
Mars reaches opposition on October 13, 2020, among the dim stars of southeastern Pisces. At opposition, Mars is biggest and brightest. Unlike some Internet memes, it is not as big as the moon. It shines as a bright star in the sky all night long.
Mars has captured our attention. It’s reddish appearance in the sky has cast it as a warrior in several cultures. After the inventions of larger telescopes, Mars brought the attention of many observers. Public announcements of possible civilizations there likely spurred the growth of science fiction writing and storytelling.
While Mars is close to Earth, it appears small even through a telescope. Through a telescope’s eyepiece, it appears as a red-ochre globe. A polar cap and some darker equatorial markings might be visible. At times, Mars surface cannot be seen when dust storms engulf the planet. For those with a telescope, Sky & Telescope’s Mars profiler shows what is visible on the surface on any date and time.
The Mars opposition occurs at the end of a span of 91 days, with the three Bright Outer Planets (Jupiter, Saturn, and Mars) passing their oppositions. Jupiter and Saturn are at their oppositions during a span of 6 days in July 2020.
Mars’ opposition occurs 72 days after it passes its orbital point closest to the sun (August 2, 2020), known as a planet’s perihelion, while the previous opposition occurred 49 days before perihelion (September 15, 2018). The July 27, 2018, event was called a “perihelic” opposition.
The accompanying charts show two perspectives of the planet’s motion from July 21, 2020, to January 5, 2021. The first chart shows the apparent motions of Mars as seen against the starry background in southeastern Pisces. The second chart shows the view of a section of Earth’s orbital path and Mars’ orbit as viewed from above the solar system.
In the notes in this article, the “m” numbers are measures of the planets’ and stars’ brightness. The lower the number, the brighter the celestial object. The sun has the lowest value (−26.5) on this scale. Afterall it is so bright it creates daytime on our planet and shines on the moon and other planets in its system. The planets’ brightness changes as their distances from Earth vary.
Each full digit numeric change on the magnitude scale equals a change of 2.5 times (2.512x). From the beginning of the sequence to its brightest, Mars brightness increases 25 times, a dramatic, but easily observed change of brightness. As we move away from Mars in start the new year, the planet’s brightness decreases about ten times from its brightest light. So, like an excellent golf score, the lower the number the brighter the “star.”
All Planets in Morning Sky
As the sequence opens, five naked eye planets are in the morning sky, along with Uranus, Neptune, and Pluto. At about 40 minutes before sunrise, the bright planets span nearly 168° of ecliptic longitude, stretching from horizon to horizon. Mercury (m = 0.4), a day before its greatest elongation, is quite low in the east-northeast. Use a binocular and find a clear horizon. Brilliant Venus (m = −4.6) is about 20° up in the east, to the lower left of Aldebaran. Mars (m = −0.9) is over 45° up in the south-southeast. Farther westward along the ecliptic, Saturn (m = 0.1) is about 10° up in the southwest. Bright Jupiter is 6.4° to Saturn’s lower right. Because Mercury is low in the sky, start looking for Jupiter about an hour before sunrise. Work your way eastward across the sky to find Mercury with a binocular 10-20 minutes later. I’ve seen Jupiter just a few degrees above the horizon without optical assistance. It might be possible to see all of them in the sky together.
Mars at Opposition
Here’s what to look for:
- July 21, 2020: This is the first day displayed on the charts. See the text above for a description of the menagerie of morning planets. Bright Mars (m = −0.9) is moving eastward against the starry background. As midnight approaches, the Red Planet is 5° up in the east.
- August 2: Mars (m = −1.1) is at perihelion, 1.38 AU from the sun, its closest point to the sun in its orbit. As midnight approaches, it is 10° up in the east.
- August 4: Mars (m = −1.2) passes 0.4° to the upper left of a star with the catalog name 89 Piscium (89 Psc, m = 5.1). The star is dim. Use a binocular to see Mars with the starfield.
- August 8: As midnight approaches the moon (19.5 days past the New phase, 73% illuminated) is 2.0° to the lower right of Mars (m = −1.3) that is about 13° in altitude in the east.
- August 22: Mars (m = −1.6) passes 0.5° to the upper left of Nu Piscium (ν Psc, m = 4.4). Four hours after sunset, Mars is nearly 18° in altitude in the east.
- September 5: Four hours after sunset, the moon (18.1d, 86%) – over 20° up in the east – is 0.7° below Mars (m = −1.9).
- September 9: Mars (m = −2.0) begins to retrograde; four hours after sunset, it is nearly 25° up in the east-southeast. See the first chart above Retrograde motion is an illusion. To early astronomers, this was the cosmological problem of the time. Those who thought Earth was at the center of all motion used a series of circles needed to get the planets to move westward compared to the starry background. For observers who thought all the planets revolved around the sun, Mars seems to move backwards when our faster moving planet catches, overtakes, and moves past the Red Planet. Mars and all objects in the solar system beyond it seem to back up for a period of time, then resume their eastward motion compared to the starry background as we move past. This is more obvious for the bright planets, especially Mars. The issue of Earth’s place in the solar system was not finalized until after the invention of the telescope and precision instruments were developed to measure our planet’s revolution around the sun.
For those with further interest, the variable star Mira (ο Cet) is predicted to reach its brightness. This paragraph describes more Mira’s brightness prediction and its location to Mars Predicted dates for the brightest phase range from mid-September to late in the month. The brightest magnitude is uncertain, ranging from 2.0 to 4.0. On September 15, Mira is about 12° to the lower left of Mars. For the latest observations of Mira’s brightness, check with the American Association of Variable Star Observers (https://www.aavso.org/).
- October 2: Three hours after sunset, Mars (m = −2.5) is 24° up in the east-southeast. The bright gibbous moon (15.7d, 98%) is 1.3° to the lower right of the planet.
- October 6: Earth and Mars (m = −2.6) are at their closest. The planet passes 0.4° to the lower right of Mu Piscium (μ Psc, m = 4.8). Use a binocular to see the dimmer star with Mars. Three hours after sunset, the Red Planet is over 25° in altitude in the east-southeast.
- October 13: Earth is between Mars and the sun. When the sun sets, Mars is rising in the eastern sky. Around midnight (about 1 a.m. during Daylight Saving Time), Mars is in the south. Mars sets in the western sky at sunrise. Mars and sun are opposite in the sky. Mars is at opposition, 1.43 AU from the sun and 0.419 AU from Earth. Three hours after sunset, the planet is over 30° up in the east-southeast.
- October 23: Mars (m = −2.4) passes 0.6° to the lower right of 80 Piscium (80 Psc, m = 5.5). Use a binocular to see the star with Mars. Two hours after sunset, Mars is over 25° in altitude in the east-southeast.
- October 29: Two hours after sunset, the bright moon (13.2d, 98%) is nearly 26° up in the east-southeast. Mars (m = −2.2) is 4.8° to the upper right of the gibbous moon.
- November 13: Mars’ (m = −1.7) retrograde ends. Mars begins to move eastward compared to the starry background. Two hours after sunset, the planet is nearly 40° up in the southeast.
- November 25: At the end of evening twilight, Mars (m = −1.3) is over 40° in altitude in the southeast. The moon (10.8d, 84%) is 5.1° to the lower left of Mars. (The end of twilight occurs about 100 minutes after sunset.)
- December 4: Mars (m = −1.0) passes 1.0° below Epsilon Piscium (ε Psc, m = 4.2). Use a binocular to track Mars compared to the dimmer starry background. At the end of evening twilight, Mars is over 45° in altitude in the southeast.
- December 12: Mars (m = −0.7) passes 0.6° above Zeta Piscium (ζ Psc, m = 5.2). Another dim star. You’ll likely need a binocular to see the star. At the end of evening twilight, find the Red Planet 50° up in the southeast.
- December 21: Forty-five minutes after sunset, Mars (m = −0.5) is nearly 48° up in the southeast. The half-full moon (7.3d, 50%), over 40° up in the south-southeast, is about 24° to the lower right of Mars. This is the evening of the once-every-generation Great Conjunction of Jupiter (m = −2.0) and Saturn (m = 0.6). The conjunction is about 14° in altitude above the southwest horizon. Mar and Jupiter are nearly 83° apart.
- December 23: At the end of evening twilight, Mars is 55° up in the south-southeast. The moon (9.3d, 69%) is 5.6° to the lower left of Mars.
- December 31: Mars (m = −0.2) passes 1.0° to the lower left of Pi Piscium (π Psc, m = 5.5). A binocular is needed to see the dim star and the planet together. At the end of evening twilight, Mars is nearly 60° in altitude in the south-southeast.
- January 5, 2021: This is the last day displayed on the charts. At the end of evening twilight, Mars (m = −0.1) is 60° in altitude in the south-southeast.
The sequence ends with Jupiter and Saturn approaching their solar conjunctions. The giant planetary pair is 15 days past the December 21, 2020, Great conjunction. Jupiter is 1.7° east of Saturn. During mid-twilight, Jupiter is about 6° up in the southwest. Along with Mercury, Jupiter and Saturn are less than 20° east of the sun. Mars is over 85° of ecliptic longitude from Jupiter. In the morning sky, Venus is about 5° up in the southeast during morning twilight. While the sun is between them, Venus is over 37° in ecliptic longitude from Jupiter.
What’s Next for Mars
Mars heads toward brighter starfields during 2021. During March, it passes the Pleiades and the Hyades, and moves between the Bull’s horns in mid-April. Mars strolls through the Beehive Cluster in late June, although the pair is low in the west-northwest during evening twilight. During mid-July, Venus passes Mars in the western evening sky. Later in the month, Mars passes Regulus with Venus higher in the sky, although the Mars – Regulus pair is very low in the sky during mid-twilight. Then, Mars makes a slow slide into evening twilight. It reaches its solar conjunction on October 7, 2021. The next opposition is December 7, 2022. Mars is farther away, 0.549 AU. This is followed by the January 15, 2025, opposition, when the Martian distance increases to 0.734 AU. | 0.885136 | 3.548204 |
But consider, for a moment, the following information regarding asteroids: In the previous 12 years—thanks to enhanced detection—the number of known near-Earth objects (NEOs) has grown from around 500 to upwards of 7000. Of those, approximately 20 percent are potentially hazardous to mankind, meaning that in the coming centuries, they conceivably could collide with the Earth.
Not exactly a cheery thought, is it? But there's more, says former astronaut and PM editorial advisor, Tom Jones, who recently co-chaired a NASA Advisory Council task force on the subject of defending our planet from such calamitous celestial bodies.
"Remember, there are probably a million near-Earth asteroids out there that can come all the way through the atmosphere should they strike us," Jones says. "Twenty percent of a million is 200,000. So we have 200,000 potentially city-busting near-earth asteroids out there, and we know of only a tiny fraction of them."
Shoot 'Em Up
With these frightening realities in mind, the eight-member Ad Hoc Task Force on Planetary Defense recommended ways in which NASA may address the threat of an NEO impact. Primary among them is establishing a Planetary Defense Coordination Office to begin in earnest the task of sifting through the options—strategies that currently include using a small spacecraft, called a gravity tractor, to pull an asteroid off-track; impacting it with a somewhat larger craft to knock it off course; and detonating a nuclear weapon near its surface to vaporize soil, propelling it in another direction.
But while a newly minted planetary defense office might conjure images of four-star generals huddled in mission control, readying the star fleet and a nuclear arsenal, its mandate is likely to be far more mundane.
"You won't need a rocket or a spacecraft on the ground, ready to go," Jones says. "That's never the case in any of these situations. You don't need a standing interceptor fleet, or defense missile forces. All you need is warning time. And you can construct what you need, decades in advance—if you're doing the search and warning in the right way."
That's because, in the words of task force member Don Yeomans—who manages the NASA Jet Propulsion Laboratory's Near-Earth Object Program Office—when it comes to preventing asteroid impacts, there are three key elements: "Find them early. Find them early. And the third thing is, find them early."
Search 'Em Out
The main priority, then, is to first improve our vision. Existing asteroid detection and tracking stations include the Goldstone Solar System Radar in California, the Arecibo telescope in Puerto Rico, and the International Astronomical Union's Minor Planet Center.
Increasing the rate of discovery requires upgrades: Collaborating with the Air Force's Pan-STARR Telescope in Hawaii and the proposed Large Synoptic Survey Telescope (LSST) would be a good start. The task force also advocates launching a new space-based telescope. For about the cost of a typical NASA planetary mission, around $500 million, a tailor-made telescope would survey space for as-yet-unknown NEOs, potentially eliminating the mystery of what else is up there (and headed for us) in its first five years of operation.
A better understanding of the threat, aided by earlier identification, will help government officials determine the most effective method for preventing a destructive event. "It's a matter of good public policy," Jones says. "Here's a natural disaster, which we have a solution for, and it's irresponsible to not invest in the modest insurance. We need to find out, first of all, what's out there."
To paraphrase a favorite metaphor of Apollo astronaut and task force co-chair Rusty Schweickart; for centuries humankind has stood in the batter's box, with eyes closed, while the solar system heaved high heat at us. Only recently did we open our eyes to face the chin music. Where before our blindness protected us, now we face a decision: duck or get hit? | 0.913395 | 3.443849 |
A massive star is born: Time-lapse movie shows that massive stars form like their smaller siblings
(PhysOrg.com) -- A team of astronomers led by Lynn D. Matthews at the MIT Haystack Observatory has discovered a disk of gas swirling close to a young massive star, which they say offers the first evidence that massive stars form similarly to smaller stars. Because massive stars are believed to be responsible for creating most of the chemical elements in the universe that are critical for the formation of Earth-like planets and life, understanding how they form may help unravel mysteries about the origins of life.
Until now, it had been difficult to prove how massive stars form because they are rare, form very quickly and tend to be enshrouded in dense, dusty material, making it hard to observe them. By using the National Science Foundation’s Very Long Baseline Array (VLBA) radio telescope to take images of the wavelengths of light emitted by a massive young star located 1,350 light years away in the Orion constellation, Matthews’ team has produced a high-resolution time-lapse movie that reveals a disk rotating around the star, known as Source I (when spoken, “Source Eye”).
“It is the first really ironclad confirmation that massive young stars are surrounded by orbiting accretion disks, and the first strong suggestion that these disks launch magnetically driven winds,” said University of California at Santa Cruz astronomy and astrophysics professor Mark Krumholz of the time-lapse movie, which is described in a paper published in the Jan. 1 issue of the Astrophysical Journal.
For almost 20 years, astronomers have known that low-mass stars form as a result of disk-mediated accretion, or from material formed from a structure rotating around a central body and driven by magnetic winds. But it had been impossible to confirm whether this was true for massive stars, which are eight to 100 times larger than low-mass stars. Without any hard data, theorists proposed many models for how massive stars might form, such as via collisions of smaller stars. “This work should rule out many of them,” Krumholz said of Matthews’ movie.
Piercing the Dusty Cloud
A network of 10 radio telescope dishes located across North America, the VLBA can be thought of as a virtual telescope 5,000 miles in diameter, according to Matthews. Used as a zoom lens to penetrate the dusty cloud surrounding the massive star, the VLBA captured images up to 1,000 times sharper than those previously obtained by other telescopes, including NASA’s Hubble Space Telescope.
By assembling 19 individual images of Source I taken by the VLBA at monthly intervals between March 2001 and December 2002, the high-resolution movie reveals thousands of masers, radio emitting gas clouds that can be thought of as naturally occurring lasers, located close to the massive star. According to Matthews, only three massive stars in the entire galaxy are known to have silicon monoxide masers. Because the silicon monoxide masers emit beams of intense radiation that can pierce the dusty material surrounding Source I, the scientists could probe the material close to the star and measure the motions of individual gas clumps.
By tracking the gas motions through space, the astronomers discovered the rotating accretion disk comprised of gas clumps orbiting the central star, as well as clumps moving away from it that appear to be caught in an outflowing wind. Such gas outflows help form stars by carrying momentum away from the system.
One interesting implication of the masers near Source I is that some gas particles appear to move away from the massive star along curved trajectories that wrap in a helix shape resembling Twizzlers candy. “To induce that kind of curvature, our observations seem to suggest, there is some role of magnetic fields during this process,” Matthews said.
To better understand this possible magnetic field, researchers plan to measure the polarization of the light from gas around the star, which will help them quantify its strength and geometry. The group would also like to extend the time span of the movie to several years to see the evolution of the material around the star over longer time scales.
“Full-motion movies are actually quite rare in astronomy,” Krumholz said. “With a few exceptions, most processes take place much too slowly for noticeable changes to occur over a human lifetime.”
Matthews’ team includes scientists from the Harvard-Smithsonian Center for Astrophysics, the National Radio Astronomy Observatory and the University of Illinois at Urbana-Champaign, Department of Physics. | 0.848145 | 3.88148 |
Tektites, are pieces of natural glass. Several natural glass types are found on the Earth. By outward appearance some tektites resemble obsidian the commonest of the natural glasses. Microscopically, tektites resemble glass more than obsidian in that they are almost completely devoid of any mineral crystals in their composition. The tektite glass is homogeneous in nature with the elements it contains dissolved and mixed.
Tektites have much less water in their composition than obsidians (often a thousand times less).
Tektites are thought to come from: With severa schools of thought over the last hundred years, basically today it distils down to the Earth through the impact of a meteorite or comet.
Terrestrial source theory: A simple, spherical splash-form Indochinite tektite The overwhelming consensus of Earth and planetary scientists is that tektites consist of terrestrial debris that was ejected during the formation of an impact crater. During the extreme conditions created by an hypervelocity meteorite impact, near-surface terrestrial sediments and rocks were either melted, vaporized, or some combination of these and ejected from an impact crater. After ejection from the impact crater, the material formed millimeter- to centimeter-sized bodies of molten material, which as they re-entered the atmosphere, rapidly cooled to form tektites that fell to Earth to create a layer of distal ejecta hundreds or thousands of kilometers away from the impact site.[
A moldavite tektite The terrestrial source for tektites is supported by well-documented evidence. The chemical and isotopic composition of tektites indicates that they are derived from the melting of silica-rich crustal and sedimentary rocks, which are not found on the Moon. In addition, some tektites contain relict mineral inclusions (quartz, zircon, rutile, chromite, and monazite) that are characteristic of terrestrial sediments and crustal and sedimentary source rocks. Also, three of the four tektite strewnfields have been linked by their age and chemical and isotopic composition to known impact craters. A number of different geochemical studies of tektites from the Australasian strewnfield concluded that these tektites consist of melted Jurassic sediments or sedimentary rocks that were weathered and deposited about 167 Ma ago. Their geochemistry suggests that the source of Australasian tektites is a single sedimentary formation with a narrow range of stratigraphic ages close to 170 Ma more or less. This effectively refutes multiple impact hypotheses.
Although it is widely accepted that the formation of and widespread distribution of tektites requires the intense (superheated) melting of near-surface sediments and rocks at the impact site and the following high-velocity ejection of this material from the impact crater, the exact processes involved remain poorly understood. One possible mechanism for the formation of tektites is by the jetting of highly shocked and superheated melt during the initial contact/compression stage of impact crater formation. Alternatively, various mechanisms involving the dispersal of shock-melted material by an expanding vapor plume, which is created by a hypervelocity impact, have been used to explain the formation of tektites. Any mechanism by which tektites are created must explain chemical data that suggest that parent material from which tektites were created came from near-surface rocks and sediments at an impact site. In addition, the scarcity of known strewn fields relative to the number of identified Impact craters indicate that very special and rarely met circumstances are required in order for tektites to be created by a meteorite impact.
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Scientists using the Herschel space observatory have made the first definitive detection of water vapor on the largest and roundest object in the asteroid belt, Ceres.
Plumes of water vapor are thought to shoot up periodically from Ceres when portions of its icy surface warm slightly. Ceres is classified as a dwarf planet, a solar system body bigger than an asteroid and smaller than a planet.
Herschel is a European Space Agency (ESA) mission with important NASA contributions.
“This is the first time water vapor has been unequivocally detected on Ceres or any other object in the asteroid belt and provides proof that Ceres has an icy surface and an atmosphere,” said Michael Küppers of ESA in Spain, lead author of a paper in the journal Nature.
The results come at the right time for NASA’s Dawn mission, which is on its way to Ceres now after spending more than a year orbiting the large asteroid Vesta. Dawn is scheduled to arrive at Ceres in the spring of 2015, where it will take the closest look ever at its surface.
“We’ve got a spacecraft on the way to Ceres, so we don’t have to wait long before getting more context on this intriguing result, right from the source itself,” said Carol Raymond, the deputy principal investigator for Dawn at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “Dawn will map the geology and chemistry of the surface in high resolution, revealing the processes that drive the outgassing activity.” | 0.815905 | 3.498963 |
Pluto is amazing scientists who had expected surprises, but no the kind of surprises that are coming from the new data.
NASA’s New Horizon’s probe has done more than just take a pretty shot of former planet Pluto — it’s also revealing some amazing new details about what was once considered our ninth planet.
After New Horizons blasted past Pluto on July 14, scientists expected to see some amazing things, but what they found was even more incredible than they expect: Pluto is a very active piece of rock in our solar system that has an evolving world and is not just a static piece of rock, according to a Globe and Mail report.
Alan Stern, the principal investigator for the mission, said that Pluto is a lot more complicated than expected, with images the indicate recent geological formations on it, and evidence that the cosmic rock has a very active interior.
Pluto has some similarities to Earth: it has a transparent atmosphere that is mostly composed of nitrogen gas. However, Pluto doesn’t have much gravity, which means the atmosphere is lost to space.
An internal source is likely to be the cause of what is seen, which would explain Pluto’s land forms and the fact that the surface doesn’t bare much evidence of craters, as you would expect of a planet that doesn’t have much activity and therefore would be bombarded by rocks hurtling at it from space.
Scientists therefore think there is a volatile layer underneath the surface of it that would result in vents and chasms. While no direct evidence has been found yet, that evidence may be coming soon.
The new pictures of Pluto are amazing, but perhaps the most interesting data will come from other sources: the spacecraft will be taking a look at the other side of Pluto as it flies by.
These results could come as soon as Friday, although it is expected that months will pass before scientists receive the full amount of data from New Horizons in order to get a complete picture of the planet. | 0.876361 | 3.141841 |
Why? Because we never pass up the opportunity to sling Sean Connery puns. Also, this lunar ash hole is actually pretty cool.
These images, above and below (of the ash hole, not Mr. Connery), were photographed by NASA's Lunar Reconnaissance Orbiter. More info here.
As Bad Astronomy's Phil Plait explains, craters on the Moon used to be a frequent topic of debate among astronomers. Were these bowl-shaped cavities the remnants of volcanos, or evidence of impact events?
The answer? Both, technically, but mostly impact events. That being said, evidence of volcanism does pop up from time to time. Case in point: this awesome photo of what Plait calls a lunar "ash hole," one that is actually indicative of volcanism and an impact event:
This odd-looking feature took me a few minutes to figure out, even after reading the description page. What you're seeing is an impact crater about 170 meters (185 yards) across – the whole image is 450 meters (500 yards) in width. But what's all that black stuff in the middle?
The picture inset here is an overview of the region (about 200 km across), and you can see the big blanket of darker material on the somewhat lighter lunar surface. The asterisk marks the location of the above picture. The dark stuff is pyroclastic – ash and other material that's been blown out of volcanic vents in what are called fire fountains. In this inset picture it looks dark, but when it was fresh it was even darker. Over the eons, blasting by subatomic particles in the solar wind – think of it as cosmic erosion – has lightened it. Either that, or nearby impacts blew lighter-colored material over it. | 0.808524 | 3.321696 |
Basic knowledge of atomic physics and quantum mechanics is required. When necessary, concepts of thermal and statistical physics will be discussed during the course.
All the light we see when we look up at the night sky comes either directly or indirectly from starlight. Understanding the physics of stars is therefore the basis of many aspects of astronomy: it is key to unravel the light of nearby and extremely distant galaxies. It also is an important factor in determining whether exo-planets can host life as we know it.
The main goal of this lecture series is to review the physical processes that determine the basic properties of stars. Topics that will be addressed include: nuclear energy production, energy and radiation transport, and the stellar structure equations. These will then be used to present models of the basic observable properties of stars such as mass, luminosity and surface temperature. These models also give a good understanding of the distribution of stars in the Hertzsprung-Russel diagram where for a collection of stars absolute magnitudes are plotted versus their observed colours. Also, we will review what happens when stars come at the end of their energy production. For massive stars we will study how supernova explosions lead to the formation of neutron stars and even black holes, while for less massive stars we will see that the final end products are white dwarfs. Finally, we will sketch some of the physical processes that lead to the formation of stars.
In this course, students will be trained in the following behaviour-oriented skills:
Problem solving (recognizing and analyzing problems, solution-oriented thinking)
Analytical skills (analytical thinking, abstraction, evidence)
Structured thinking (structure, modulated thinking, computational thinking, programming)
Written communication (writing skills, reporting, summarizing)
Critical thinking (asking questions, check assumptions)
Mode of instruction
Lectures and seminars
Computer problems and class assignments: 30%. Only if the average grade is higher than 5.0, students are allowed to take the written exam.
Written exam: 70%. See Examination schedules bachelor Astronomy
Lecture notes, additional readings and assignments will be provided via Blackboard. To have access, you need an ULCN account. More information:
- LeBlanc, F. (2010): An Introduction to Stellar Astrophysics, ISBN: 978-0-470-69956-0 required
Register via uSis. More information about signing up for classes and exams can be found here. Exchange and Study Abroad students, please see the Prospective students website for information on how to register. For a la carte and contract registration, please see the dedicated section on the Prospective students website. | 0.832 | 3.298628 |
For about 10 years, radio astronomers have been detecting mysterious milliseconds-long blasts of radio waves, called “fast radio bursts” (FRB).
While only 18 of these events have been detected so far, one FRB has been particularly intriguing as the signal has been sporadically repeating. First detected in November 2012, astronomers didn’t know if FRB 121102 originated from within the Milky Way galaxy or from across the Universe.
A concentrated search by multiple observatories around the world has now determined that the signals are coming from a dim dwarf galaxy about 2.5 billion light years from Earth. But astronomers are still uncertain about exactly what is creating these bursts.
“These radio flashes must have enormous amounts of energy to be visible from that distance,” said Shami Chatterjee from Cornell University, speaking at a press briefing at the American Astronomical Society meeting this week. Chatterjee and his colleagues have papers published today in Nature and Astrophysical Journal Letters.
The patch of the sky where the signal originated is in the constellation Auriga, and Chatterjee said the patch of the sky is arc minutes in diameter. “In that patch are hundreds of sources. Lots of stars, lots of galaxies, lots of stuff,” he said, which made the search difficult.
The Arecibo radio telescope, the observatory that originally detected the event, has a resolution of three arc minutes or about one-tenth of the moon’s diameter, so that was not precise enough to identify the source. Astronomers used the Very Large Array in New Mexico and the European Very Large Baseline Interferometer (VLBI) network, to help narrow the origin. But, said co-author Casey Law from the University of California Berkeley, that also created a lot of data to sort through.
“It was like trying to find a needle in a terabyte haystack,” he said. “It took a lot of algorithmic work to find it.”
Finally on August 23, 2016, the burst made itself extremely apparent with nine extremely bright bursts.
“We had struggled to be able to observe the faintest bursts we could,” Law said, “but suddenly here were nine of the brightest ones ever detected. This FRB was generous to us.”
The team was not only able to pinpoint it to the distant dwarf galaxy, co-author Jason Hessels from ASTRON/University of Amsterdam said they were also able to determine the bursts didn’t come from the center of the galaxy, but came from slightly off-center in the galaxy. That might indicate it didn’t originate from a central black hole. Upcoming observations with the Hubble Space Telescope might be able to pinpoint it even further.
What makes this source burst repeatedly?
“We don’t know yet what caused it or the physical mechanism that makes such bright and fast pulses,” said said Sarah Burke-Spolaor, from West Virginia University. “The FRB could be outflow from an active galactic nuclei (AGN) or it might be more familiar, such as a distant supernova remnant, or a neutron star.”
Burke-Spolaor added that they don’t know yet if all FRBs are created equal, as so far FRB 121102 is the only repeater. The team hopes there will be other examples detected.
“It may be a magnetar – a newborn neutron star with a huge magnetic field, inside a supernova remnant or a pulsar wind nebula – somehow producing these prodigious pulses,” said Chatterjee. “Or, it may be a combination of all these ideas – explaining why what we’re seeing may be somewhat rare.” | 0.880553 | 3.966133 |
According to data received from ESA’s Rosetta spacecraft, ESO’s New Technology Telescope, and NASA telescopes, strange asteroid Lutetia could be a real piece of the rock… the original material that formed the Earth, Venus and Mercury! By examining precious meteors which may have formed at the time of the inner Solar System, scientists have found matching properties which indicate a relationship. Independent Lutetia must have just moved its way out to join in the main asteroid belt…
A team of astronomers from French and North American universities have been hard at work studying asteroid Lutetia spectroscopically. Data sets from the OSIRIS camera on ESA’s Rosetta spacecraft, ESO’s New Technology Telescope (NTT) at the La Silla Observatory in Chile, and NASA’s Infrared Telescope Facility in Hawaii and Spitzer Space Telescope have been combined to give us a multi-wavelength look at this very different space rock. What they found was a very specific type of meteorite called an enstatite chondrite displayed similar content which matched Lutetia… and what is theorized as the material which dates back to the early Solar System. Chances are very good that enstatite chondrites are the same “stuff” which formed the rocky planets – Earth, Mars and Venus.
“But how did Lutetia escape from the inner Solar System and reach the main asteroid belt?” asks Pierre Vernazza (ESO), the lead author of the paper.
It’s a very good question considering that an estimated less than 2% of the material which formed in the same region of Earth migrated to the main asteroid belt. Within a few million years of formation, this type of “debris” had either been incorporated into the gelling planets or else larger pieces had escaped to a safer, more distant orbit from the Sun. At about 100 kilometers across, Lutetia may have been gravitationally influenced by a close pass to the rocky planets and then further affected by a young Jupiter.
“We think that such an ejection must have happened to Lutetia. It ended up as an interloper in the main asteroid belt and it has been preserved there for four billion years,” continues Pierre Vernazza.
Asteroid Lutetia is a “real looker” and has long been a source of speculation due to its unusual color and surface properties. Only 1% of the asteroids located in the main belt share its rare characteristics.
“Lutetia seems to be the largest, and one of the very few, remnants of such material in the main asteroid belt. For this reason, asteroids like Lutetia represent ideal targets for future sample return missions. We could then study in detail the origin of the rocky planets, including our Earth,” concludes Pierre Vernazza.
Original Story Source: ESO News Release. | 0.870233 | 3.706096 |
The Incredible Shrinking Mercury is Active After All
It’s small, it’s hot, and it’s shrinking. New NASA-funded research suggests that Mercury is contracting even today, joining Earth as a tectonically active planet.
Images obtained by NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft reveal previously undetected small fault scarps— cliff-like landforms that resemble stair steps. These scarps are small enough that scientists believe they must be geologically young, which means Mercury is still contracting and that Earth is not the only tectonically active planet in our solar system, as previously thought.
The findings are reported in a paper in the October issue of Nature Geoscience.
“The young age of the small scarps means that Mercury joins Earth as a tectonically active planet, with new faults likely forming today as Mercury’s interior continues to cool and the planet contracts,” said lead author Tom Watters, Smithsonian senior scientist at the National Air and Space Museum in Washington, D.C.
Large fault scarps on Mercury were first discovered in the flybys of Mariner 10 in the mid-1970s and confirmed by MESSENGER, which found the planet closest to the sun was shrinking. The large scarps were formed as Mercury’s interior cooled, causing the planet to contract and the crust to break and thrust upward along faults making cliffs up to hundreds of miles long and some more than a mile (over one-and-a-half kilometers) high.
In the last 18 months of the MESSENGER mission, the spacecraft’s altitude was lowered, which allowed the surface of Mercury to be seen at much higher resolution. These low-altitude images revealed small fault scarps that are orders of magnitude smaller than the larger scarps. The small scarps had to be very young, investigators say, to survive the steady bombardment of meteoroids and comets. They are comparable in scale to small, young lunar scarps that are evidence Earth’s moon is also shrinking.
This active faulting is consistent with the recent finding that Mercury’s global magnetic field has existed for billions of years and with the slow cooling of Mercury’s still hot outer core. It’s likely that the smallest of the terrestrial planets also experiences Mercury-quakes—something that may one day be confirmed by seismometers.
“This is why we explore,” said NASA Planetary Science Director Jim Green at Headquarters in Washington, D.C. “For years, scientists believed that Mercury’s tectonic activity was in the distant past. It’s exciting to consider that this small planet – not much larger than Earth’s moon – is active even today.”
Managed by the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, MESSENGER launched Aug. 3, 2004 and began orbiting Mercury March 18, 2011. The mission ended with a planned impact on the surface of Mercury on April 30, 2015. | 0.862666 | 3.547398 |
Small bodies are rocky and/or icy objects, ranging in size from a few meters to a few thousands of kilometers. They comprise near-Earth and main belt asteroids, Trojans, trans-Neptunian objects, Centaurs, comets, and a recently discovered category called the transitional objects. Their physical nature, distribution, formation, and evolution are fundamental to understand how the solar system formed and evolved and, ultimately, how planetary systems are formed in other stars.
Current and future space missions and observational efforts from both ground- and space-based telescopes provide a continuous improvement in the understanding of small bodies. They certainly provide information on the physical and chemical characteristics of the interior of these bodies e.g. thermal properties, surface composition, particle size, albedo. Observations also provide constraint to the theoretical models and numerical simulations that are meant to explain the formation and evolution of our Solar System.
The FSI has a clear link with observational efforts through a group of researchers with vast expertise in visible and near-infrared spectroscopy and photometry. Along their career, these astronomers have had access to a large collection of telescopes e.g the 10.4m Gran Telescopio Canarias, (Observatorio del Roque de los Muchachos), the two 8.1m telescopes at the Gemini Observatory (Mauna Kea, USA and Cerro Pachón, Chile), the 3.0m NASA IRTF (Mauna Kea) etc. They also have access to space telescopes as Hubble Space Telescope, Spitzer or the yet to be lunched, James Webb Space Telescope. | 0.864141 | 3.276753 |
In a footnote to the Jorge Luis Borges short story “The Library of Babel,” about a gigantic library that contains all books of a particular length composed using a particular alphabet, Borges distills the insight that animates the story: “It suffices that a book be possible for it to exist.” The number of fixed-length combinations of a small number of characters, while enormous, is not infinite, so a large enough library should, just by luck, have a very good chance of housing any conceivable book.
A similar statement can be made about the universe we live in. Just a few physical laws govern all its vastness, so if these laws allow for something to occur, there’s a good chance it will occur at some point in space and time. One illustration of this principle is the coldest region in the known universe, but before we get to it, let’s start with something more mundane: we are living in a universe-sized microwave oven.
A phenomenon discovered in 1963 called the cosmic microwave background, or CMB, is radiation left over from the Big Bang that permeates all of space. Its temperature is 2.7 Kelvin (about -455°F) and was higher in the past, so everything in the universe has been cooking at 2.7 K or hotter since the Big Bang. It seems to follow naturally that no place in the universe could be colder than this temperature, just as every part of a ham baking in a 450-degree oven will, eventually, heat up to 450 degrees.
In 1997, astronomers measured the temperature of gas escaping from the Boomerang Nebula, a giant cloud of gas and dust located about 5,000 light-years from Earth, and found it to be right around 1 K, less than half the absolute temperature of the CMB. This is the equivalent of opening up a 450-degree oven to find a chunk of dry ice.
The Boomerang Nebula’s unexpectedly low temperature is not a blow to the laws of physics but rather a striking example of nature’s inventiveness within the confines of those laws. And to explain the source of this cosmic cooling, it’s helpful to boomerang, er, to bring the discussion back to Earth and consider low-temperature experiments that take place daily in physics laboratories all over the world.
According to Guinness World Records, the coldest ambient temperature ever recorded on Earth is -129°F, or 183 K, measured in Vostok, Antarctica. By comparison, the temperature of liquid nitrogen, which is commonly available to scientists and costs about as much as milk, is about -321°F, or 77 K. How is it possible to make something so much colder than the coldest place on Earth?
The temperature of an object is a measure of the motional energy of its molecules, so to make something colder, its molecules must be slowed down by extracting energy. For a gas, a good way to extract energy is by making it push against a piston. This is how car engines work. We don’t normally notice that a car’s exhaust is much colder than the inside of the engine, but if it weren’t, the engine wouldn’t run. By repeatedly sending a gas through a piston-driven compression-and-expansion cycle, it can be continuously cooled until it condenses into a liquid. Such a process was first used in the late 19th century to liquify air, and is also used today to make liquid nitrogen.
Of course, there are no giant pistons floating around in outer space, but a piston isn’t the only thing an expanding gas can expend its heat energy on. It turns out that, under the proper conditions, an expanding gas will expend energy on itself.
Gas molecules have a weak attractive force, called the van der Waals force, pulling them together. For the distance between molecules to increase, as happens during expansion, energy must be used to overcome the van der Waals attraction and pull the molecules farther apart, just as it takes energy to stretch a rubber band. For a gas expanding in isolation, that energy comes from the motion of its molecules, causing it to cool.
So there we are: cooling upon expansion is the mechanism responsible for the Boomerang Nebula’s low temperature. The nebula is ejecting gas into surrounding space; this gas expands so rapidly that it cools at a faster rate than the CMB can heat it up, which has allowed it to reach a temperature of 1 K. From the size of the cold gas cloud and its expansion speed, it appears that this cosmic refrigerator has been running for at least 1,500 years.
Because the Boomerang Nebula’s cooling is governed by well-known principles, someone familiar with those principles could have predicted the effect. And it turns out that someone did predict it, several years before it was discovered. More than one person predicted it, actually, including one of its eventual discoverers, Raghvendra Sahai of the Jet Propulsion Laboratory in Pasadena, who was then able to confirm his predictions with observations. That, in the end, may be the deepest testament to the power of the universality of physical laws: someone can describe a situation allowed by known physics that has never been observed and reasonably expect to find it somewhere in the universe.
One final footnote: expansion cooling was also the technique used the first time a temperature colder than 2.7 K was achieved on Earth, by the Dutch physicist Heike Kamerlingh Onnes a century ago. So Kamerlingh Onnes unknowingly borrowed a cooling mechanism from an astrophysical phenomenon that hadn’t been observed (the Boomerang Nebula refrigerator) to surpass a fundamental temperature limit that hadn’t been discovered (the CMB oven). Whether one is a nebula or a man, the laws of nature delimit possibility in the same way.
Permission required for reprinting, reproducing, or other uses. | 0.801908 | 3.804192 |
Unusual supernova opens a rare window on the collapse of a star
An unusual supernova studied by multiple telescopes, including the SOAR telescope and other telescopes at the National Science Foundation's (NSF) Cerro Tololo Inter-American Observatory (CTIO) and NSF's Kitt Peak National Observatory (KPNO), is thought to herald the birth of a new black hole or neutron star, caught at the exact moment of its creation. Observations made with facilities ranging from X-rays to optical and radio wavelengths were used to understand this remarkable event. These multi-messenger observations give astronomers a rare glimpse into the physics at play during the creation of a black hole or neutron star.
A Mysterious Bright Glow
On June 16, 2018 a sky survey telescope in Hawai'i alerted the astronomical community to the sudden appearance of a new object in the sky. It was similar to a supernova, except that it brightened, and then faded, faster than a typical supernova, and was intrinsically brighter at its peak. A supernova (from nova meaning "new" star) is a sudden explosion of a massive star which has reached the end of its lifetime, leading to the formation of a black hole or neutron star. The transient object, assigned the designation AT2018cow, was immediately nicknamed "the Cow" based on the final 3 letters of its name. "The Cow" is located in a relatively nearby galaxy—only 200 million light years away from our own Milky Way galaxy in the direction of the constellation Hercules.
It Takes a Team
Immediately after receiving the alert, an international research team led by Raffaella Margutti (Northwestern University) leapt into action and began observing the unusual source across the electromagnetic spectrum—at X-ray, optical, infrared and radio wavelengths. Telescopes around the world contributed to the effort using spectroscopy to decode the nature of the source. Among the telescopes that contributed was the Southern Astrophysical Research Telescope (SOAR) in Chile whose instruments obtained spectra of the Cow. With spectra, which spread out the light in the form of a rainbow, astronomers could quickly confirm that matter was expanding from the object at up to 10% the speed of light.
Régis Cartier, who made the SOAR observations, said, "Almost from the very start I realized that this transient was special. It was fast, blue and bright, different from any supernova seen before. I dropped everything else I was working on to focus on understanding this event." In addition to the SOAR telescope, other telescopes at NSF's CTIO and KPNO imaged the object and contributed to a broader picture as the Cow faded away.
A Nearly Naked Cow
Because the collapsed star was surrounded by a relatively small amount of debris, the team was able to peer through the debris and get a glimpse of the object's "central engine." This rare event will help astronomers better understand the physics at play within the first moments of the creation of a black hole or neutron star. The results were presented today at this week's meeting of the American Astronomical Society in Seattle, Washington.
"We think that 'The Cow' is the formation of an accreting black hole or neutron star," said Giacomo Terreran (Northwestern University), who led the CTIO observations. "We know from theory that black holes and neutron stars form when a star dies, but we've never seen them right after they are born." This event may represent a new class of objects within the category known as fast luminous transients.
A Whole New World of Transients
Although a supernova like the Cow has never been seen before, Cartier expects that astronomers will detect larger numbers of such rare events in the future. Now that surveys are searching for sources that vary on a wider range of timescales, "we've already discovered a whole family of fast transients that we didn't know existed," noted Cartier.
The SOAR telescope is gearing up to help us understand these new events. Said Dr. Jay Elias, Director of SOAR, "The SOAR telescope was designed from the start to provide flexible instrument configurations, allowing it to respond quickly to events like this. There are many astronomical surveys observing interesting transient events, as well as other events, such as last year's kilonova detected by LIGO, which was also observed at SOAR. Very soon, there will be even more interesting transient events from the Large Synoptic Survey Telescope (LSST) and other large-scale survey telescopes." The LSST is a new telescope being built on the same mountaintop as the SOAR telescope with major funding from NSF: it will conduct a 10-year survey of the sky with special emphasis on transient events. | 0.86177 | 4.066284 |
Context. Understanding stellar activity in solar-type stars is crucial for the physics of stellar atmospheres as well as for ongoing exoplanet programmes. Aims. We aim to test how well we understand stellar activity using our own star, the Sun, as a test case. Methods. We performed a detailed study of the main optical activity indicators (Ca II H & K, Balmer lines, Na I D1 D2, and He I D3) measured for the Sun using the data provided by the HARPS-N solar-telescope feed at the Telescopio Nazionale Galileo. We made use of periodogram analyses to study solar rotation, and we used the pool variance technique to study the temporal evolution of active regions. The correlations between the different activity indicators as well as the correlations between activity indexes and the derived parameters from the cross-correlation technique are analysed. We also study the temporal evolution of these correlations and their possible relationship with indicators of inhomogeneities in the solar photosphere like sunspot number or radio flux values. Results. The value of the solar rotation period is found in all the activity indicators, with the only exception being Hδ. The derived values vary from 26.29 days (Hγ line) to 31.23 days (He I). From an analysis of sliding periodograms we find that in most of the activity indicators the spectral power is split into several “bands” of periods around 26 and 30 days. They might be explained by the migration of active regions between the equator and a latitude of ∼30°, spot evolution, or a combination of both effects. A typical lifetime of active regions of approximately ten rotation periods is inferred from the pooled variance diagrams, which is in agreement with previous works. We find that Hα, Hβ, Hγ, Hϵ, and He I show a significant correlation with the S index. Significant correlations between the contrast, bisector span, and the heliocentric radial velocity with the activity indexes are also found. We show that the full width at half maximum, the bisector, and the disc-integrated magnetic field correlate with the radial velocity variations. The correlation of the S index and Hα changes with time, increasing with larger sun spot numbers and solar irradiance. A similar tendency with the S index and radial velocity correlation is also present in the data. Conclusions. Our results are consistent with a scenario in which higher activity favours the correlation between the S index and the Hα activity indicators and between the S index and radial velocity variations. | 0.805888 | 3.853736 |
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