Meteor Activity Outlook for June 25-July 1, 2016

by Robert Lunsford – American Meteor Society

The June Bootids (JBO) are usually a very weak shower that occasionally produces outbursts. Nothing out of the ordinary is expected this year but with the moon out of the way so viewing for unusual activity is warranted. These meteors are best seen from June 23-25, with maximum activity occurring on the 23rd. At maximum the radiant is located at 14:56 (224) +48. This position lies in northwestern Bootes, 15 degrees east of the second magnitude star known as Alkaid (Eta Ursae Majoris). This radiant is best placed in the evening sky just as the sky becomes dark. Observers in the northern hemisphere have a distinct advantage over those located south of the equator as the radiant lies much higher in the evening sky. No matter your location, little activity is expected from this source. With an entry velocity of 13 km/sec., the average June Bootid meteor would be of very slow velocity.

skywatch

During this period the moon reaches its last quarter phase on Monday June 27th. At this time the moon will lie 90 degrees west of the sun and will rise between midnight and 0100 local daylight saving time for most sites located in mid-northern latitudes. The half-illuminated moon will interfere with meteor observing, but to a much lesser degree than when near its full phase. Toward the end of the period the waning crescent moon will rise during the late morning hours allowing  most of the night to be free of lunar glare. The estimated total hourly meteor rates for evening observers this week is near 2 for observers located in the northern hemisphere and 3 for observers located in tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 4 as seen from mid-northern latitudes (45N) and 6 as seen from tropical southern locations (25S).

Morning rates are reduced during this period due to interfering moonlight. The actual rate  s will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brightest meteors will be visible from such locations.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning June 25/26. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky.

A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at the edge and not the center. Vi  ewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.

These sources of meteoric activity are expected to be active this week.

The f Ophiuchids (FOP) were discovered by Sirko Molau and Juergen Rendtel using video data from the IMO network of cameras. These meteors are only active on 3 nights centered on June 30th. Maximum actually occurs on June 29th when the radiant is located at 17:40 (265) +08. This area of the sky is located in central Ophiuchus, 3 degrees north of the 3rd magnitude star known as Celbalrai (beta Ophiuchi). The radiant is best placed near midnight LDT when it lies on the meridian and is highest in the sky. Rates of less than 1 per hour are expected, even at maximum. With an entry velocity of 17 km/sec., the average f Ophiuchid meteor would be of very slow velocity.

The center of the large Anthelion (ANT) radiant is currently located at 19:08 (287) -22. This position lies in central Sagittarius, just south of the the twin stars known as pi and omicron Sagittarii.  Due to the large size of this radiant, Anthelion activity may also appear from the nearby constellations of Scutum, Serpens Caput, southern Aquila, and western Capricornus as well as Sagittarius. This radiant is best placed near 0100 local daylight saving (LDST), when it lies on the meridian and is located highest in the sky. Hourly rates at this time should be near 2 as seen from mid-northern latitudes and 3 as seen from tropical southern latitudes. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.

The Sigma Capricornids (SA) were discovered by Zdenek Sekanina and are active for a month lasting from June 19 through July 24. Maximum occurs on June 27th when the radiant is located at 20:24 (306) -07. This area of the sky is actually located in southeastern Aquila, five degrees north of the naked eye double star Algiedi (Alpha Capricornii). The radiant is best placed near 0300 LDT when it lies on the meridian and is highest in the sky. Rates at this time should be near one per hour no matter your location. With an entry velocity of 42 km/sec., the average Sigma Capricornid meteor would be of medium velocity. This velocity is significantly faster than the stronger Alpha Capricornids, which appear from the same general area of the sky during the second half of July.

The Pi Piscids (PPS) were discovered by Dr. Peter Brown in his meteoroid stream survey using the Canadian Meteor Orbit Radar. This shower was later verified by Dr. Peter Jenniskens and David Holman using data from the CAMS network in northern California. These meteors are active from June 11 through July 25 with maximum activity occurring on July 1st. The current position of the radiant is 00:44 (011) +23. This position actually lies in southeastern Andromeda, 2 degrees west of the 4th magnitude star known as eta Andromedae. Rates are currently expected to be less than 1 per hour no matter your location. Rates will increase to near 2 per hour at maximum. With an entry velocity of 68 km/sec., the average Pi Piscid meteor would be of swift speed.

The c-Andromedids (CAN) was discovered by Sirko Molau and Juergen Rendtel using video data from the IMO network. Activity from this source is seen from June 26 though July 20 with maximum activity occurring on July 12. The radiant currently lies at 00:54 (013) +41, which places it in northern Andromeda, close to the faint star known as nu Andromedae. This position is also just 1 degree east of the naked eye Andromeda Galaxy. This area of the sky is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Observers in the northern hemisphere are better situated to view this activity as the radiant rises much higher in the sky before dawn as seen from northern latitudes. Current rates would be less than 1 per hour no matter your location. With an entry velocity of 60 km/sec., the average meteor from this source would be of swift velocity.

As seen from the mid-northern hemisphere (45N) one would expect to see approximately 6 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 1 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 9 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates during this period are reduced due to moonlight.

The June Bootids (JBO) are usually a very weak shower that occasionally produces outbursts. Nothing out of the ordinary is expected this year but with the moon out of the way so viewing for unusual activity is warranted. These meteors are best seen from June 23-25, with maximum activity occurring on the 23rd. At maximum the radiant is located at 14:56 (224) +48. This position lies in northwestern Bootes, 15 degrees east of the second magnitude star known as Alkaid (Eta Ursae Majoris). This radiant is best placed in the evening sky just as the sky becomes dark. Observers in the northern hemisphere have a distinct advantage over those located south of the equator as the radiant lies much higher in the evening sky. No matter your location, little activity is expected from this source. With an entry velocity of 13 km/sec., the average June Bootid meteor would be of very slow velocity.

During this period the moon reaches its last quarter phase on Monday June 27th. At this time the moon will lie 90 degrees west of the sun and will rise between midnight and 0100 local daylight saving time for most sites located in mid-northern latitudes. The half-illuminated moon will interfere with meteor observing, but to a much lesser degree than when near its full phase. Toward the end of the period the waning crescent moon will rise during the late morning hours allowing  most of the night to be free of lunar glare. The estimated total hourly meteor rates for evening observers this week is near 2 for observers located in the northern hemisphere and 3 for observers located in tropical southern locations (25S). For morning observers the estimated total hourly rates should be near 4 as seen from mid-northern latitudes (45N) and 6 as seen from tropical southern locations (25S).

Morning rates are reduced duri this period due to interfering moonlight. The actual rate  s will also depend on factors such as personal light and motion perception, local weather conditions, alertness and experience in watching meteor activity. Note that the hourly rates listed below are estimates as viewed from dark sky sites away from urban light sources. Observers viewing from urban areas will see less activity as only the brightest meteors will be visible from such locations.

The radiant (the area of the sky where meteors appear to shoot from) positions and rates listed below are exact for Saturday night/Sunday morning June 25/26. These positions do not change greatly day to day so the listed coordinates may be used during this entire period. Most star atlases (available at science stores and planetariums) will provide maps with grid lines of the celestial coordinates so that you may find out exactly where these positions are located in the sky.

A planisphere or computer planetarium program is also useful in showing the sky at any time of night on any date of the year. Activity from each radiant is best seen when it is positioned highest in the sky, either due north or south along the meridian, depending on your latitude. It must be remembered that meteor activity is rarely seen at the radiant position. Rather they shoot outwards from the radiant so it is best to center your field of view so that the radiant lies at the edge and not the center. Vi  ewing there will allow you to easily trace the path of each meteor back to the radiant (if it is a shower member) or in another direction if it is a sporadic. Meteor activity is not seen from radiants that are located far below the horizon. The positions below are listed in a west to east manner in order of right ascension (celestial longitude). The positions listed first are located further west therefore are accessible earlier in the night while those listed further down the list rise later in the night.

These sources of meteoric activity are expected to be active this week.

The f Ophiuchids (FOP) were discovered by Sirko Molau and Juergen Rendtel using video data from the IMO network of cameras. These meteors are only active on 3 nights centered on June 30th. Maximum actually occurs on June 29th when the radiant is located at 17:40 (265) +08. This area of the sky is located in central Ophiuchus, 3 degrees north of the 3rd magnitude star known as Celbalrai (beta Ophiuchi). The radiant is best placed near midnight LDT when it lies on the meridian and is highest in the sky. Rates of less than 1 per hour are expected, even at maximum. With an entry velocity of 17 km/sec., the average f Ophiuchid meteor would be of very slow velocity.

The center of the large Anthelion (ANT) radiant is currently located at 19:08 (287) -22. This position lies in central Sagittarius, just south of the the twin stars known as pi and omicron Sagittarii.  Due to the large size of this radiant, Anthelion activity may also appear from the nearby constellations of Scutum, Serpens Caput, southern Aquila, and western Capricornus as well as Sagittarius. This radiant is best placed near 0100 local daylight saving (LDST), when it lies on the meridian and is located highest in the sky. Hourly rates at this time should be near 2 as seen from mid-northern latitudes and 3 as seen from tropical southern latitudes. With an entry velocity of 30 km/sec., the average Anthelion meteor would be of slow velocity.

The Sigma Capricornids (SCA) were discovered by Zdenek Sekanina and are active for a month lasting from June 19 through July 24. Maximum occurs on June 27th when the radiant is located at 20:24 (306) -07. This area of the sky is actually located in southeastern Aquila, five degrees north of the naked eye double star Algiedi (Alpha Capricornii). The radiant is best placed near 0300 LDT when it lies on the meridian and is highest in the sky. Rates at this time should be near one per hour no matter your location. With an entry velocity of 42 km/sec., the average Sigma Capricornid meteor would be of medium velocity. This velocity is significantly faster than the stronger Alpha Capricornids, which appear from the same general area of the sky during the second half of July.

The Pi Piscids (PPS) were discovered by Dr. Peter Brown in his meteoroid stream survey using the Canadian Meteor Orbit Radar. This shower was later verified by Dr. Peter Jenniskens and David Holman using data from the CAMS network in northern California. These meteors are active from June 11 through July 25 with maximum activity occurring on July 1st. The current position of the radiant is 00:44 (011) +23. This position actually lies in southeastern Andromeda, 2 degrees west of the 4th magnitude star known as eta Andromedae. Rates are currently expected to be less than 1 per hour no matter your location. Rates will increase to near 2 per hour at maximum. With an entry velocity of 68 km/sec., the average Pi Piscid meteor would be of swift speed.

The c-Andromedids (CAN) was discovered by Sirko Molau and Juergen Rendtel using video data from the IMO network. Activity from this source is seen from June 26 though July 20 with maximum activity occurring on July 12. The radiant currently lies at 00:54 (013) +41, which places it in northern Andromeda, close to the faint star known as nu Andromedae. This position is also just 1 degree east of the naked eye Andromeda Galaxy. This area of the sky is best seen during the last dark hour before dawn when the radiant lies highest in a dark sky. Observers in the northern hemisphere are better situated to view this activity as the radiant rises much higher in the sky before dawn as seen from northern latitudes. Current rates would be less than 1 per hour no matter your location. With an entry velocity of 60 km/sec., the average meteor from this source would be of swift velocity.

As seen from the mid-norther hemisphere (45N) one would expect to see approximately 6 sporadic meteors per hour during the last hour before dawn as seen from rural observing sites. Evening rates would be near 1 per hour. As seen from the tropical southern latitudes (25S), morning rates would be near 9 per hour as seen from rural observing sites and 2 per hour during the evening hours. Locations between these two extremes would see activity between the listed figures. Evening rates during this period are reduced due to moonlight.

BREAKING NEWS: New Study Reinforces Cyclical Magnetic Pole Reversals

It is important to understand there are scientifically identified varying forms of cyclical events, sometimes referred to as time-variable control parameters. As it is with the nature of scientific formulas and equations, it can be a bit complicated. Therefore, I will explain in a way that is reflective of schematics.

magnetic-field-earth

Specially related to Geophysics and Paleomagnetism, periods of magnetic reversals are basically defined in three forms of cycles. The reason for such variables, is unlike the study of solar cycles goes back only a few hundred years, the research related to Earth’s magnetic reversals covers billions of years. And to this researcher, it highlights Earth’s relationship to our galaxy Milky Way and beyond which I believe already shows cycles going back hundreds of thousands years, and at the rate of new research coming in, I believe new data will identify cyclical events related to our solar system going back to near the Big Bang.

http://www.dreamstime.com/stock-photo-earth-core-structure-to-scale-isolated-illustrated-geological-layers-according-black-elements-d-image-furnished-image38470080

One measurement of a magnetic reversal (MR) is defined as ‘below random’. The reason for this variable is the period between supercrons and clustering. This is because of the variance in convection between the Earth’s core and mantle. In simple terms, it is yet specifically identified as to the external cause of heating and cooling cycles of Earth’s core. Again, to this writer, it is a sure sign the convection process goes far beyond or Sun’s influence. Remember, the Sun’s magnetic field reversal has only a 22 year oscillation; which actually suggests it plays a small part related to Earth’s magnetic reversal. However, this does not mean the solar flux does not cause harmful effects to Earth and humans. During times of high solar activity, solar flares and cmes can pierce through the magnetic field. And during times of low solar activity, the lack of solar plasma allows the more harmful and damaging Galactic Cosmic Rays to enter our atmosphere which brings with it a blast of radiation.

liquid-core

A second measurement of a MR cycle is defined as ‘nearly periodic’. Again, this has to do with periods of Earth’s development such as the Paleozoic, Mesozoic, and Cenozoic eras. As the Earth’s inner core developed, of course this would have a developing influence on the convection process.

A third measurement of a MR cycle is defined as ‘time-dependent periodic’. This is to say, from the time of Earth’s fully developed inner core, there is a time-dependent cycle of magnetic fluctuation of a pre, during, and post reversal. The reason for the term “time-dependent” is directly related to the ebb and flow of mantle plumes. In other words, it is directly related to the heating and cooling of Earth’s core through the process of convection.

multipile magnetic fields ancient earth

Why is this important? Because it can be fully identified and measured. In other words, there will be signs and symptoms during the process. In fact, we are already seeing them. First the magnetic north pole will drift. It will continue and speed up over time and may go as far south as 40th degree parallel. Then in its final stages it will bounce back and forth between north and south, then finally and perhaps in a single day, flip completely.

More coming soon…………

 

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NASA Scientists Discover Unexpected Mineral On Mars

Scientists have discovered an unexpected mineral in a rock sample at Gale Crater on Mars, a finding that may alter our understanding of how the planet evolved.

nasa

NASA’s Mars Science Laboratory rover, Curiosity, has been exploring sedimentary rocks within Gale Crater since landing in August 2012. In July 2015, on Sol 1060 (the number of Martian days since landing), the rover collected powder drilled from rock at a location named “Buckskin.” Analyzing data from an X-ray diffraction instrument on the rover that identifies minerals, scientists detected significant amounts of a silica mineral called tridymite.

This detection was a surprise to the scientists, because tridymite is generally associated with silicic volcanism, which is known on Earth but was not thought to be important or even present on Mars.

The discovery of tridymite might induce scientists to rethink the volcanic history of Mars, suggesting that the planet once had explosive volcanoes that led to the presence of the mineral.

Scientists in the Astromaterials Research and Exploration Science (ARES) Division at NASA’s Johnson Space Center in Houston led the study. A paper on the team’s findings has been published in the Proceedings of the National Academy of Sciences.

“On Earth, tridymite is formed at high temperatures in an explosive process called silicic volcanism. Mount St. Helens, the active volcano in Washington State, and the Satsuma-Iwojima volcano in Japan are examples of such volcanoes. The combination of high silica content and extremely high temperatures in the volcanoes creates tridymite,” said Richard Morris, NASA planetary scientist at Johnson and lead author of the paper. “The tridymite was incorporated into ‘Lake Gale’ mudstone at Buckskin as sediment from erosion of silicic volcanic rocks.”

The paper also will stimulate scientists to re-examine the way tridymite forms. The authors examined terrestrial evidence that tridymite could form at low temperatures from geologically reasonable processes and not imply silicic volcanism. They found none. Researchers will need to look for ways that it could form at lower temperatures.

“I always tell fellow planetary scientists to expect the unexpected on Mars,” said Doug Ming, ARES chief scientist at Johnson and co-author of the paper. “The discovery of tridymite was completely unexpected. This discovery now begs the question of whether Mars experienced a much more violent and explosive volcanic history during the early evolution of the planet than previously thought.”

Hubble Confirms New Dark Spot On Neptune

New images obtained on May 16, 2016, by NASA’s Hubble Space Telescope confirm the presence of a dark vortex in the atmosphere of Neptune. Though similar features were seen during the Voyager 2 flyby of Neptune in 1989 and by the Hubble Space Telescope in 1994, this vortex is the first one observed on Neptune in the 21st century.

neptune

The discovery was announced on May 17, 2016, in a Central Bureau for Astronomical Telegrams (CBAT) electronic telegram by University of California at Berkeley research astronomer Mike Wong, who led the team that analyzed the Hubble data.

Neptune’s dark vortices are high-pressure systems and are usually accompanied by bright “companion clouds,” which are also now visible on the distant planet. The bright clouds form when the flow of ambient air is perturbed and diverted upward over the dark vortex, causing gases to likely freeze into methane ice crystals. “Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains,” Wong said. “And the companion clouds are similar to so-called orographic clouds that appear as pancake-shaped features lingering over mountains on Earth.”

Beginning in July 2015, bright clouds were again seen on Neptune by several observers, from amateurs to astronomers at the W. M. Keck Observatory in Hawaii. Astronomers suspected that these clouds might be bright companion clouds following an unseen dark vortex. Neptune’s dark vortices are typically only seen at blue wavelengths, and only Hubble has the high resolution required for seeing them on distant Neptune.

In September 2015, the Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble Space Telescope project that annually captures global maps of the outer planets, revealed a dark spot close to the location of the bright clouds, which had been tracked from the ground. By viewing the vortex a second time, the new Hubble images confirm that OPAL really detected a long-lived feature. The new data enabled the team to create a higher-quality map of the vortex and its surroundings.

Neptune’s dark vortices have exhibited surprising diversity over the years, in terms of size, shape, and stability (they meander in latitude, and sometimes speed up or slow down). They also come and go on much shorter timescales compared to similar anticyclones seen on Jupiter; large storms on Jupiter evolve over decades.

Planetary astronomers hope to better understand how dark vortices originate, what controls their drifts and oscillations, how they interact with the environment, and how they eventually dissipate, according to UC Berkeley doctoral student Joshua Tollefson, who was recently awarded a prestigious NASA Earth and Space Science Fellowship to study Neptune’s atmosphere. Measuring the evolution of the new dark vortex will extend knowledge of both the dark vortices themselves, as well as the structure and dynamics of the surrounding atmosphere.

The team, led by Wong, also included the OPAL team (Wong, Amy Simon, and Glenn Orton), UC Berkeley collaborators (Imke de Pater, Joshua Tollefson, and Katherine de Kleer), Heidi Hammel (AURA), Statia Luszcz-Cook (AMNH), Ricardo Hueso and Agustin Sánchez-Lavega (Universidad del Pais Vasco), Marc Delcroix (Société Astronomique de France), Larry Sromovsky and Patrick Fry (University of Wisconsin), and Christoph Baranec (University of Hawaii).

The Universe: Learning About The Future From The Distant Past

Our Universe came to life nearly 14 billion years ago in the Big Bang — a tremendously energetic fireball from which the cosmos has been expanding ever since. Today, space is filled with hundreds of billions of galaxies, including our solar system’s own galactic home, the Milky Way. But how exactly did the infant universe develop into its current state, and what does it tell us about our future?

universe

These are the fundamental questions “astrophysical archeologists” like Risa Wechsler want to answer. At the Kavli Institute for Particle Astrophysics and Cosmology (KIPAC) of Stanford and the Department of Energy’s SLAC National Accelerator Laboratory, her team combines experimental data with theory in computer simulations that dig deeply into cosmic history and trace back how matter particles clumped together to form larger and larger structures in the expanding universe.

“Most of our calculations are done at KIPAC, and computing is a crucial aspect of the collaboration between SLAC and Stanford,” says Wechsler, who is an associate professor of physics and of particle physics and astrophysics.

Wechsler’s simulated journeys through spacetime use a variety of experimental data, including observations by the Dark Energy Survey (DES), which recently discovered a new set of ultra-faint companion galaxies of our Milky Way that are rich in what is known as dark matter. The gravitational pull from this invisible form of matter affects regular matter, which plays a crucial role in the formation and growth of galaxies.

Dark energy is another key ingredient shaping the universe: It inflates the universe like a balloon at an ever-increasing rate, but researchers don’t know much about what causes the acceleration.

Two future projects will give Wechsler and other researchers new clues about the mysterious energy. The Dark Energy Spectroscopic Instrument (DESI), whose science collaboration she is leading, will begin in 2018 to turn two-dimensional images of surveys like DES into a three-dimensional map of the universe. The Large Synoptic Survey Telescope (LSST), whose ultrasensitive 3,200-megapixel digital eye is being assembled at SLAC, will start a few years later to explore space more deeply than any telescope before.

“Looking at faraway galaxies means looking into the past and allows us to measure how the growth and distribution of galaxies were affected by dark energy at different points in time,” Wechsler says. “Over the past 10 years, we’ve made a lot of progress in refining our cosmological model, which describes many of the properties of today’s universe very well. Yet, if future data caused this model to break down, it would completely change our view of the universe.”

The current model suggests that the universe is fated to expand forever, turning into a darker and darker cosmos faster and faster, with galaxies growing farther and farther apart. But is this acceleration a constant or changing property of spacetime? Or could it possibly be a breakdown of our theory of gravity on the largest scales? More data will help researchers find an answer to these fundamental questions.

An Ocean Lies A Few Kilometers Beneath Saturn’s Moon Enceladus’s Icy Surface

With eruptions of ice and water vapor, and an ocean covered by an ice shell, Saturn’s moon Enceladus is one of the most fascinating in the Solar System, especially as interpretations of data provided by the Cassini spacecraft have been contradictory until now. An international team including researchers from the Laboratoire de Planétologie Géodynamique de Nantes (CNRS/Université de Nantes/Université d’Angers), Charles University in Prague, and the Royal Observatory of Belgium[recently proposed a new model that reconciles different data sets and shows that the ice shell at Enceladus’s south pole may be only a few kilometers thick.

enceladus

This suggests that there is a strong heat source in the interior of Enceladus, an additional factor supporting the possible emergence of life in its ocean.

The study has just been published online on the website of Geophysical Research Letters.

Initial interpretations of data from Cassini flybys of Enceladus estimated that the thickness of its ice shell ranged from 30 to 40 km at the south pole to 60 km at the equator. These models were unable to settle the question of whether or not its ocean extended beneath the entire ice shell. However, the discovery in 2015 of an oscillation in Enceladus’s rotation known as a libration, which is linked to tidal effects, suggests that it has a global ocean and a much thinner ice shell than predicted, with a mean thickness of around 20 km. Nonetheless, this thickness appeared to be inconsistent with other gravity and topography data.

In order to reconcile the different constraints, the researchers propose a new model in which the top two hundred meters of the ice shell acts like an elastic shell. According to this study, Enceladus is made up successively of a rocky core with a radius of 185 km, and an internal ocean approximately 45 km deep, isolated from the surface by an ice shell with a mean thickness of around 20 km, except at the south pole where it is thought to be less than 5 km thick. In this model, the ocean beneath the ice makes up 40% of the total volume of the moon, while its salt content is estimated to be similar to that of Earth’s oceans.

All this implies a new energy budget for Enceladus. Since a thinner ice shell retains less heat, the tidal effects caused by Saturn on the large fractures in the ice at the south pole are no longer enough to explain the strong heat flow affecting this region. The model therefore reinforces the idea that there is strong heat production in Enceladus’s deep interior that may power the hydrothermal vents on the ocean floor. Since complex organic molecules, whose precise composition remains unknown, have been detected in Enceladus’s jets, these conditions appear to be favorable to the emergence of life. The relative thinness of the ice shell at the south pole could also allow a future space exploration mission to gather data, in particular using radar, which would be far more reliable and easy to obtain than with the 40 km thick ice shell initially calculated.

Newborn Giant Planet Grazes Its Star

For the past 20 years, exoplanets known as ‘hot Jupiters’ have puzzled astronomers. These giant planets orbit 100 times closer to their host stars than Jupiter does to the Sun, which increases their surface temperatures. But how and when in their history did they migrate so close to their star? Now, an international team of astronomers has announced the discovery of a very young hot Jupiter orbiting in the immediate vicinity of a star that is barely two million years old — the stellar equivalent of a week-old infant. This first-ever evidence that hot Jupiters can appear at such an early stage represents a major step forward in our understanding of how planetary systems form and evolve.

planet

The work, led by researchers at the Institut de Recherche en Astrophysique et Planétologie (IRAP, CNRS/Université Toulouse III — Paul Sabatier)[1], in collaboration, amongst others[2], with colleagues at the Institut de Planétologie et d’Astrophysique de Grenoble (CNRS/Université Grenoble Alpes)[3], is published on 20 June 2016 in the journal Nature.

It was while monitoring a star barely two million years old called V830 Tau, located in the Taurus stellar nursery some 430 light years away, that an international team of astronomers discovered the youngest known hot Jupiter. The team observed the star for a month and a half and detected a regular fluctuation in the star’s velocity, revealing the presence of a planet almost as massive as Jupiter, orbiting its host star at a distance only one twentieth of that between the Earth and the Sun. The discovery shows for the first time that hot Jupiters can appear at a very early stage in the formation of planetary systems, and therefore have a major impact on their architecture.

In the Solar System, small rocky planets such as the Earth orbit near the Sun, whereas gas giants like Jupiter and Saturn are found much further out. Astronomers were therefore astonished when the first exoplanets detected turned out to be giants orbiting close to their host star. Theoretical work indicates that such planets can only form in the icy outer regions of the protoplanetary disk in which both the central star and its surrounding planets are born. Some, however, migrate inwards and yet avoid falling into their host star, thus becoming hot Jupiters.

Theoretical models predict that migration occurs either early in the lives of giant planets while still embedded within the protoplanetary disk, or else much later, once multiple planets are formed and interact, flinging some of them into the immediate vicinity of their star. Among the known hot Jupiters, some feature tilted or even backward orbits, suggesting that they were hurled towards their star by neighboring bodies. The discovery of a very young hot Jupiter thus confirms that early migration within the disk also applies to giant planets.

Detecting planets in orbit around very young stars proves to be a significant observational challenge, since such stars are monsters in comparison with our own Sun. This is because their intense magnetic activity interferes with the light emitted by the star to a far greater extent than a potential giant planet, even in a close orbit. One of the team’s achievements was to separate the signal caused by the star’s activity from the signal produced by the planet.

For this discovery, the team used the twin spectropolarimeters[4] ESPaDOnS and Narval, designed and built at IRAP. ESPaDOnS is mounted on the Canada-France-Hawaii Telescope (CFHT) on the summit of Maunakea, a dormant volcano on the Island of Hawaii. Narval is mounted on the Bernard Lyot telescope (TBL — OMP) atop the Pic du Midi in the French Pyrenees. The combined use of these two telescopes together with Hawaii’s Gemini telescope was essential for the required continuous monitoring of V830 Tau. SPIRou and SPIP, the next-generation infrared spectropolarimeters built at IRAP for the CFHT and TBL, scheduled for first light in 2017 and 2019 respectively, will offer vastly superior performance and make it possible to study the formation of new worlds with unprecedented sensitivity.