New research, August 28 - September 3, 2017

A selection of new climate related research articles is shown below.

Climate change

1. Continuously Amplified Warming in the Alaskan Arctic: Implications for Estimating Global Warming Hiatus

"Focusing on the "hiatus" period 1998-2012 as identified by the Intergovernmental Panel on Climate Change (IPCC) report, the SAT has increased at 0.45 °C/decade, which captures more than 90% of the regional trend for 1951-2012. We suggest that sparse in-situ measurements are responsible for underestimation of the SAT change in the gridded datasets."

2. Extreme warming in the Kara Sea and Barents Sea during the winter period 2000 to 2016

"The maximum warming occurs north of Novaya Zemlya in the Kara Sea and Barents Sea between March 2003-2012 and is responsible for up to 20°C increase. Land-based observations confirm the increase but do not cover the maximum regions that are located over the ocean and sea-ice."

3. Tropical semi-arid regions expanding over temperate latitudes under climate change

"We show that a global expansion of this climatic domain has already started according to climate observations in the twentieth century (about + 13% of surface increase, i.e. from 6 to 7% of the global land surface). Models project that this expansion will continue throughout the twenty-first century, whatever the scenario..."

4. Representation of mid-latitude North American coastal storm activity by six global reanalyses

"All reanalyses are found to successfully represent most aspects of mid-latitude North American coastal strong storm activity, annually and seasonally, along both coasts. Nevertheless, ERA-Interim, MERRA, and CFSR provide the better representations of mid-latitude North American coastal strong storm activity, with ERA-Interim performing best overall."

5. Is Nitrogen the Next Carbon?

"The increased use of nitrogen has been critical for increased crop yields and protein production needed to keep pace with the growing world population. However, similar to carbon, the release of fixed nitrogen into the natural environment is linked to adverse consequences at local, regional, and global scales. Anthropogenic contributions of fixed nitrogen continue to grow relative to the natural budget, with uncertain consequences."

6. Annual and seasonal tornado activity in the United States and the global wind oscillation

"Combined, these analyses suggest that seasons with more low atmospheric angular momentum days, or phase 2, 3, and 4 days, tend to have greater tornado activity than those with fewer days, and that this relationship is most evident in winter and spring."

7. Assessing climate change impacts on extreme weather events: the case for an alternative (Bayesian) approach

"Using a simple conceptual model for the occurrence of extreme weather events, we show that if the objective is to minimize forecast error, an alternative approach wherein likelihoods of impact are continually updated as data become available is preferable. Using a simple “proof-of-concept,” we show that such an approach will, under rather general assumptions, yield more accurate forecasts."

8. Trends in extreme temperature indices in Huang-Huai-Hai River Basin of China during 1961–2014

9. Is the choice of statistical paradigm critical in extreme event attribution studies?

10. How will precipitation change in extratropical cyclones as the planet warms? Insights from a large initial condition climate model ensemble

11. Improved Sea Ice Forecasting Through Spatiotemporal Bias Correction

12. New methodology to estimate Arctic sea ice concentration from SMOS combining brightness temperature differences in a maximum-likelihood estimator

13. Modulation of the seasonal cycle of Antarctic sea ice extent related to the Southern Annular Mode

14. Lake dynamics and its relationship to climate change on the Tibetan Plateau over the last four decades

15. On the short-term grounding zone dynamics of Pine Island glacier, West Antarctica observed with COSMO-SkyMed interferometric data

16. The weakened intensity of atmospheric quasi-biweekly oscillation over the western North Pacific during late summer around the late 1990s

17. Causal Pathways for Temperature Predictability from Snow Depth

18. Spatial patterns of summer speedup on south-central Alaska glaciers

19. Increased Ocean Heat Convergence into the High Latitudes with CO2-Doubling Enhances Polar-Amplified Warming

20. Consistently estimating internal climate variability from climate-model simulations

21. Comparison of climatic trends and variability among glacierized environments in the Western Himalayas

Climate change impacts

22. Seasonal temperature is associated with Parkinson’s disease prescriptions: an ecological study

"The prescribed LED was 4.2% greater in January and 4.5% lower in July. Statistical analysis showed that temperature was associated with the prescription of Parkinson medications. Our results suggest seasonality exists in Parkinson’s disease symptoms and this may be related to temperature."

23. The effects of hot nights on mortality in Barcelona, Spain

"The estimated associations for both exposure variables and mortality shows a relationship with high and medium values that persist significantly up to a lag of 1–2 days. In mortality due to natural causes, an increase of 1.1% per 10% (CI95% 0.6–1.5) for hot night hours and 5.8% per each 10° (CI95% 3.5–8.2%) for hot night degrees is observed."

24. Leap-frog in slow-motion: divergent responses of tree species and life stages to climatic warming in Great Basin sub-alpine forests

"Bristlecone pine juveniles establishing above treeline share some environmental associations with bristlecone adults. Limber pine above-treeline juveniles, in contrast, are prevalent across environmental conditions and share few environmental associations with limber pine adults. Strikingly, limber pine is establishing above treeline throughout the region without regard to site characteristic such as soil type, slope, aspect, or soil texture. Though limber pine is often rare at treeline where it coexists with bristlecone pine, limber pine juveniles dominate above treeline even on calcareous soils that are core bristlecone pine habitat. Limber pine is successfully “leap-frogging” over bristlecone pine, probably because of its strong dispersal advantage and broader tolerances for establishment."

25. Ocean acidification alters zooplankton communities and increases top-down pressure of a cubozoan predator

"Specifically, we show that in the combined presence of OA and a cubozoan predator, populations of the most abundant member of the zooplankton community (calanoid copepods) were reduced 27% more than it would be predicted based on the effects of these stressors in isolation, suggesting that OA increases the susceptibility of plankton to predation. Our results indicate that the ecological consequences of OA may be greater than predicted from single-species experiments, and highlight the need to understand future marine global change from a community perspective."

26. Future reef growth can mitigate physical impacts of sea-level rise on atoll islands

"Comparatively, vertical reef accretion in response to SLR will prevent any significant increase in shoreline wave energy and mitigate wave driven flooding volume by 72%."

27. Climate change and Population Growth Impacts on Surface water Supply and Demand of Addis Ababa, Ethiopia

28. The relationship between extreme weather events and crop losses in central Taiwan

29. Spatial distributions of Southern Ocean mesozooplankton communities have been resilient to long-term surface warming

30. Long-term Ecological Changes in Marine Mammals Driven by Recent Warming in Northwestern Alaska

31. Characteristics of meteorological drought pattern and risk analysis for maize production in Xinjiang, Northwest China

32. County-level climate change information to support decision-making on working lands

33. Alterations in microbial community composition with increasing fCO2: a mesocosm study in the eastern Baltic Sea

34. Metabolic compensation constrains the temperature dependence of gross primary production

35. Phenology of a dipterocarp forest with seasonal drought: insights into the origin of general flowering

36. Modeling Arctic sea-ice algae: Physical drivers of spatial distribution and algae phenology

37. Evaluating the classical versus an emerging conceptual model of peatland methane dynamics

38. Patterns and biases of climate-change threats in the IUCN Red List

39. Heat stress mortality and desired adaptation responses of healthcare system in Poland

40. Quantifying climate change induced threats to wetland fisheries: a stakeholder-driven approach

Climate change mitigation

41. Does the world have low-carbon bioenergy potential from the dedicated use of land?

ABSTRACT: "While some studies find no room for the dedicated use of land for bioenergy because of growing food needs, other studies estimate large bioenergy potentials, even at levels greater than total existing human plant harvest. Analyzing this second category of studies, we find they have in various ways counted the carbon benefits of using land for biofuels but ignored the costs. Basic carbon opportunity cost calculations per hectare explain why alternative uses of any available land are likely to do more to hold down climate change. Because we find that solar power can provide at least 100 times more useable energy per hectare on three quarters of the world's land, any “surplus” land could also provide the same energy and mitigate climate ~ 100 times more if 1% were devoted to solar and the rest to carbon storage. Review of large bioenergy potential estimates from recent IAMs shows that they depend on many contingencies for carbon benefits, can impose many biodiversity and food costs, and are more predictions of what bioenergy might be in idealized than plausible, future scenarios. At least at this time, policy should not support bioenergy from energy crops and other dedicated uses of land."

42. Who Wins from Emissions Trading? Evidence from California

"Importantly, conditional on race and ethnicity, we find that higher income areas receive larger reductions in pollution under cap-and-trade. Furthermore, conditional on income (or poverty rates), we find that Blacks benefit while Hispanics lose relative to whites under RECLAIM."

43. Climate change and the re-evaluation of cost-benefit analysis

"In this essay, I discuss the shortcomings of CBA framed by its historical development and argue that its relatively recent application to climate change has contributed to growth in the literature re-evaluating its normative foundations."

44. The Value of Energy Efficiency and the Role of Expected Heating Costs

"Results suggest that heating cost considerations are less relevant than previously thought."

45. Some problems in storing renewable energy

46. Improving building energy efficiency in India: State-level analysis of building energy efficiency policies

47. The withdrawal of the U.S. from the Paris Agreement and its impact on global climate change governance

Other papers

48. On the impacts of computing daily temperatures as the average of the daily minimum and maximum temperatures

"Our results show that the calculation of daily temperature based on the average of minimum and maximum daily readings leads to an overestimation of the daily values of ~ 10+ % when focusing on extremes and values above (below) high (low) thresholds. Moreover, the effects of the data processing method on trend estimation are generally small, even though the use of the daily minimum and maximum readings reduces the power of trend detection (~ 5–10% fewer trends detected in comparison with the reference data)."

from Skeptical Science http://ift.tt/2wV92py

A selection of new climate related research articles is shown below.

Climate change

1. Continuously Amplified Warming in the Alaskan Arctic: Implications for Estimating Global Warming Hiatus

"Focusing on the "hiatus" period 1998-2012 as identified by the Intergovernmental Panel on Climate Change (IPCC) report, the SAT has increased at 0.45 °C/decade, which captures more than 90% of the regional trend for 1951-2012. We suggest that sparse in-situ measurements are responsible for underestimation of the SAT change in the gridded datasets."

2. Extreme warming in the Kara Sea and Barents Sea during the winter period 2000 to 2016

"The maximum warming occurs north of Novaya Zemlya in the Kara Sea and Barents Sea between March 2003-2012 and is responsible for up to 20°C increase. Land-based observations confirm the increase but do not cover the maximum regions that are located over the ocean and sea-ice."

3. Tropical semi-arid regions expanding over temperate latitudes under climate change

"We show that a global expansion of this climatic domain has already started according to climate observations in the twentieth century (about + 13% of surface increase, i.e. from 6 to 7% of the global land surface). Models project that this expansion will continue throughout the twenty-first century, whatever the scenario..."

4. Representation of mid-latitude North American coastal storm activity by six global reanalyses

"All reanalyses are found to successfully represent most aspects of mid-latitude North American coastal strong storm activity, annually and seasonally, along both coasts. Nevertheless, ERA-Interim, MERRA, and CFSR provide the better representations of mid-latitude North American coastal strong storm activity, with ERA-Interim performing best overall."

5. Is Nitrogen the Next Carbon?

"The increased use of nitrogen has been critical for increased crop yields and protein production needed to keep pace with the growing world population. However, similar to carbon, the release of fixed nitrogen into the natural environment is linked to adverse consequences at local, regional, and global scales. Anthropogenic contributions of fixed nitrogen continue to grow relative to the natural budget, with uncertain consequences."

6. Annual and seasonal tornado activity in the United States and the global wind oscillation

"Combined, these analyses suggest that seasons with more low atmospheric angular momentum days, or phase 2, 3, and 4 days, tend to have greater tornado activity than those with fewer days, and that this relationship is most evident in winter and spring."

7. Assessing climate change impacts on extreme weather events: the case for an alternative (Bayesian) approach

"Using a simple conceptual model for the occurrence of extreme weather events, we show that if the objective is to minimize forecast error, an alternative approach wherein likelihoods of impact are continually updated as data become available is preferable. Using a simple “proof-of-concept,” we show that such an approach will, under rather general assumptions, yield more accurate forecasts."

8. Trends in extreme temperature indices in Huang-Huai-Hai River Basin of China during 1961–2014

9. Is the choice of statistical paradigm critical in extreme event attribution studies?

10. How will precipitation change in extratropical cyclones as the planet warms? Insights from a large initial condition climate model ensemble

11. Improved Sea Ice Forecasting Through Spatiotemporal Bias Correction

12. New methodology to estimate Arctic sea ice concentration from SMOS combining brightness temperature differences in a maximum-likelihood estimator

13. Modulation of the seasonal cycle of Antarctic sea ice extent related to the Southern Annular Mode

14. Lake dynamics and its relationship to climate change on the Tibetan Plateau over the last four decades

15. On the short-term grounding zone dynamics of Pine Island glacier, West Antarctica observed with COSMO-SkyMed interferometric data

16. The weakened intensity of atmospheric quasi-biweekly oscillation over the western North Pacific during late summer around the late 1990s

17. Causal Pathways for Temperature Predictability from Snow Depth

18. Spatial patterns of summer speedup on south-central Alaska glaciers

19. Increased Ocean Heat Convergence into the High Latitudes with CO2-Doubling Enhances Polar-Amplified Warming

20. Consistently estimating internal climate variability from climate-model simulations

21. Comparison of climatic trends and variability among glacierized environments in the Western Himalayas

Climate change impacts

22. Seasonal temperature is associated with Parkinson’s disease prescriptions: an ecological study

"The prescribed LED was 4.2% greater in January and 4.5% lower in July. Statistical analysis showed that temperature was associated with the prescription of Parkinson medications. Our results suggest seasonality exists in Parkinson’s disease symptoms and this may be related to temperature."

23. The effects of hot nights on mortality in Barcelona, Spain

"The estimated associations for both exposure variables and mortality shows a relationship with high and medium values that persist significantly up to a lag of 1–2 days. In mortality due to natural causes, an increase of 1.1% per 10% (CI95% 0.6–1.5) for hot night hours and 5.8% per each 10° (CI95% 3.5–8.2%) for hot night degrees is observed."

24. Leap-frog in slow-motion: divergent responses of tree species and life stages to climatic warming in Great Basin sub-alpine forests

"Bristlecone pine juveniles establishing above treeline share some environmental associations with bristlecone adults. Limber pine above-treeline juveniles, in contrast, are prevalent across environmental conditions and share few environmental associations with limber pine adults. Strikingly, limber pine is establishing above treeline throughout the region without regard to site characteristic such as soil type, slope, aspect, or soil texture. Though limber pine is often rare at treeline where it coexists with bristlecone pine, limber pine juveniles dominate above treeline even on calcareous soils that are core bristlecone pine habitat. Limber pine is successfully “leap-frogging” over bristlecone pine, probably because of its strong dispersal advantage and broader tolerances for establishment."

25. Ocean acidification alters zooplankton communities and increases top-down pressure of a cubozoan predator

"Specifically, we show that in the combined presence of OA and a cubozoan predator, populations of the most abundant member of the zooplankton community (calanoid copepods) were reduced 27% more than it would be predicted based on the effects of these stressors in isolation, suggesting that OA increases the susceptibility of plankton to predation. Our results indicate that the ecological consequences of OA may be greater than predicted from single-species experiments, and highlight the need to understand future marine global change from a community perspective."

26. Future reef growth can mitigate physical impacts of sea-level rise on atoll islands

"Comparatively, vertical reef accretion in response to SLR will prevent any significant increase in shoreline wave energy and mitigate wave driven flooding volume by 72%."

27. Climate change and Population Growth Impacts on Surface water Supply and Demand of Addis Ababa, Ethiopia

28. The relationship between extreme weather events and crop losses in central Taiwan

29. Spatial distributions of Southern Ocean mesozooplankton communities have been resilient to long-term surface warming

30. Long-term Ecological Changes in Marine Mammals Driven by Recent Warming in Northwestern Alaska

31. Characteristics of meteorological drought pattern and risk analysis for maize production in Xinjiang, Northwest China

32. County-level climate change information to support decision-making on working lands

33. Alterations in microbial community composition with increasing fCO2: a mesocosm study in the eastern Baltic Sea

34. Metabolic compensation constrains the temperature dependence of gross primary production

35. Phenology of a dipterocarp forest with seasonal drought: insights into the origin of general flowering

36. Modeling Arctic sea-ice algae: Physical drivers of spatial distribution and algae phenology

37. Evaluating the classical versus an emerging conceptual model of peatland methane dynamics

38. Patterns and biases of climate-change threats in the IUCN Red List

39. Heat stress mortality and desired adaptation responses of healthcare system in Poland

40. Quantifying climate change induced threats to wetland fisheries: a stakeholder-driven approach

Climate change mitigation

41. Does the world have low-carbon bioenergy potential from the dedicated use of land?

ABSTRACT: "While some studies find no room for the dedicated use of land for bioenergy because of growing food needs, other studies estimate large bioenergy potentials, even at levels greater than total existing human plant harvest. Analyzing this second category of studies, we find they have in various ways counted the carbon benefits of using land for biofuels but ignored the costs. Basic carbon opportunity cost calculations per hectare explain why alternative uses of any available land are likely to do more to hold down climate change. Because we find that solar power can provide at least 100 times more useable energy per hectare on three quarters of the world's land, any “surplus” land could also provide the same energy and mitigate climate ~ 100 times more if 1% were devoted to solar and the rest to carbon storage. Review of large bioenergy potential estimates from recent IAMs shows that they depend on many contingencies for carbon benefits, can impose many biodiversity and food costs, and are more predictions of what bioenergy might be in idealized than plausible, future scenarios. At least at this time, policy should not support bioenergy from energy crops and other dedicated uses of land."

42. Who Wins from Emissions Trading? Evidence from California

"Importantly, conditional on race and ethnicity, we find that higher income areas receive larger reductions in pollution under cap-and-trade. Furthermore, conditional on income (or poverty rates), we find that Blacks benefit while Hispanics lose relative to whites under RECLAIM."

43. Climate change and the re-evaluation of cost-benefit analysis

"In this essay, I discuss the shortcomings of CBA framed by its historical development and argue that its relatively recent application to climate change has contributed to growth in the literature re-evaluating its normative foundations."

44. The Value of Energy Efficiency and the Role of Expected Heating Costs

"Results suggest that heating cost considerations are less relevant than previously thought."

45. Some problems in storing renewable energy

46. Improving building energy efficiency in India: State-level analysis of building energy efficiency policies

47. The withdrawal of the U.S. from the Paris Agreement and its impact on global climate change governance

Other papers

48. On the impacts of computing daily temperatures as the average of the daily minimum and maximum temperatures

"Our results show that the calculation of daily temperature based on the average of minimum and maximum daily readings leads to an overestimation of the daily values of ~ 10+ % when focusing on extremes and values above (below) high (low) thresholds. Moreover, the effects of the data processing method on trend estimation are generally small, even though the use of the daily minimum and maximum readings reduces the power of trend detection (~ 5–10% fewer trends detected in comparison with the reference data)."

from Skeptical Science http://ift.tt/2wV92py

Pluto craft wakes from hibernation today

This image shows New Horizons’ current position along its full planned trajectory. The green segment of the line shows where New Horizons has traveled since launch; the red indicates the spacecraft’s future path. Positions of stars with magnitude 12 or brighter are shown from this perspective, which is slightly above the orbital plane of the planets. Via Johns Hopkins’ page Where is New Horizons?

NASA’s New Horizons spacecraft – which visited Pluto in July, 2015 – was placed in hibernation on April 7, 2017. The craft is set to be awoken today (September 11, 2017). In the meantime, the science and mission operations teams have been developing detailed command loads for New Horizon’s next encounter, a nine-day flyby of the Kuiper Belt object 2014 MU69 on New Year’s Day, 2019. Among other things, the mission has now set the flight plan and the distance for closest approach, aiming to come three times closer to MU69 than it famously flew past Pluto in 2015.

Hibernation reduced wear and tear on the spacecraft’s electronics, lowered operations costs and freed up NASA Deep Space Network tracking and communication resources for other missions. But New Horizons mission activity didn’t entirely stop during the hibernation period. While much of the craft is unpowered during hibernation, the onboard flight computer has continued to monitor system health and to broadcast a weekly beacon-status tone back to Earth. About once a month, the craft has sent home data on spacecraft health and safety. Onboard sequences sent in advance by mission controllers will eventually wake New Horizons to check out critical systems, gather new Kuiper Belt science data, and perform any necessary course corrections.

2014 MU69 will soon become the only Kuiper Belt object ever to be visited by a spacecraft. It’ll be the farthest planetary encounter in history – some one billion miles (1.5 billion km) beyond Pluto and more than four billion miles (6.5 billion km) from Earth. If all goes as planned, New Horizons will come to within just 2,175 miles (3,500 km) of MU69 at closest approach, peering down on it from celestial north. The alternate plan, to be employed in certain contingency situations such as the discovery of debris near MU69, would take New Horizons within 6,000 miles (10,000 km)— still closer than the 7,800-mile (12,500-km) flyby distance to Pluto.

Read more from NASA about New Horizons’ new flight plan and mission

Artist’s concept of New Horizons spacecraft flying by a possible binary 2014 MU69 on January 1, 2019. Early observations of MU69 hint at the Kuiper Belt object being either a binary orbiting pair or a contact (stuck together) pair of nearly like-sized bodies with diameters near 12 and 11 miles (20 and 18 km). Image via Carlos Hernandez/ NASA.

Bottom line: The New Horizons spacecraft – famous for visiting Pluto in 2015 – will wake from a 157-day hibernation on September 11, 2017. Mission controllers have filed a flight plan for the 2019 encounter with 2014 MU69.

from EarthSky http://ift.tt/2w1lS7e

This image shows New Horizons’ current position along its full planned trajectory. The green segment of the line shows where New Horizons has traveled since launch; the red indicates the spacecraft’s future path. Positions of stars with magnitude 12 or brighter are shown from this perspective, which is slightly above the orbital plane of the planets. Via Johns Hopkins’ page Where is New Horizons?

NASA’s New Horizons spacecraft – which visited Pluto in July, 2015 – was placed in hibernation on April 7, 2017. The craft is set to be awoken today (September 11, 2017). In the meantime, the science and mission operations teams have been developing detailed command loads for New Horizon’s next encounter, a nine-day flyby of the Kuiper Belt object 2014 MU69 on New Year’s Day, 2019. Among other things, the mission has now set the flight plan and the distance for closest approach, aiming to come three times closer to MU69 than it famously flew past Pluto in 2015.

Hibernation reduced wear and tear on the spacecraft’s electronics, lowered operations costs and freed up NASA Deep Space Network tracking and communication resources for other missions. But New Horizons mission activity didn’t entirely stop during the hibernation period. While much of the craft is unpowered during hibernation, the onboard flight computer has continued to monitor system health and to broadcast a weekly beacon-status tone back to Earth. About once a month, the craft has sent home data on spacecraft health and safety. Onboard sequences sent in advance by mission controllers will eventually wake New Horizons to check out critical systems, gather new Kuiper Belt science data, and perform any necessary course corrections.

2014 MU69 will soon become the only Kuiper Belt object ever to be visited by a spacecraft. It’ll be the farthest planetary encounter in history – some one billion miles (1.5 billion km) beyond Pluto and more than four billion miles (6.5 billion km) from Earth. If all goes as planned, New Horizons will come to within just 2,175 miles (3,500 km) of MU69 at closest approach, peering down on it from celestial north. The alternate plan, to be employed in certain contingency situations such as the discovery of debris near MU69, would take New Horizons within 6,000 miles (10,000 km)— still closer than the 7,800-mile (12,500-km) flyby distance to Pluto.

Read more from NASA about New Horizons’ new flight plan and mission

Artist’s concept of New Horizons spacecraft flying by a possible binary 2014 MU69 on January 1, 2019. Early observations of MU69 hint at the Kuiper Belt object being either a binary orbiting pair or a contact (stuck together) pair of nearly like-sized bodies with diameters near 12 and 11 miles (20 and 18 km). Image via Carlos Hernandez/ NASA.

Bottom line: The New Horizons spacecraft – famous for visiting Pluto in 2015 – will wake from a 157-day hibernation on September 11, 2017. Mission controllers have filed a flight plan for the 2019 encounter with 2014 MU69.

from EarthSky http://ift.tt/2w1lS7e

NASA ponders Saturn mission legacy

Saturn, backlit. Composite, made from images from Cassini while the craft was in Saturn’s shadow, on October 17, 2012, using infrared, red and violet spectral filters. Views like this one have been rare and precious, because the timing and spacecraft/planet/sun geometry has to be perfect. Previous to this image, Cassini captured a view like this in 2006. Via NASA JPL.

NASA statement via Preston Dyches at the Jet Propulsion Laboratory, Pasadena, California.

As the Cassini spacecraft nears the end of a long journey rich with scientific and technical accomplishments, it is already having a powerful influence on future exploration. In revealing that Saturn’s moon Enceladus has many of the ingredients needed for life, the mission has inspired a pivot to the exploration of ocean worlds that has been sweeping planetary science over the past decade. Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington, said:

Cassini has transformed our thinking in so many ways, but especially with regard to surprising places in the solar system where life could potentially gain a foothold. Congratulations to the entire Cassini team!

Onward to Europa

Jupiter’s moon Europa has been a prime target for future exploration since NASA’s Galileo mission, in the late 1990s, found strong evidence for a salty global ocean of liquid water beneath its icy crust. But the more recent revelation that a much smaller moon like Enceladus could also have not only liquid water, but also chemical energy that could potentially power biology, was staggering.

Many lessons learned during Cassini’s mission are being applied to planning NASA’s Europa Clipper mission, planned for launch in the 2020s. Europa Clipper will fly by the icy ocean moon dozens of times to investigate its potential habitability, using an orbital tour design derived from the way Cassini has explored Saturn. The Europa Clipper mission will orbit the giant planet — Jupiter in this case — using gravitational assists from its large moons to maneuver the spacecraft into repeated close encounters with Europa. This is similar to the way Cassini’s tour designers used the gravity of Saturn’s moon Titan to continually shape their spacecraft’s course.

In addition, many engineers and scientists from Cassini are serving on Europa Clipper and helping to develop its science investigations. For example, several members of the Cassini Ion and Neutral Mass Spectrometer and Cosmic Dust Analyzer teams are developing extremely sensitive, next-generation versions of their instruments for flight on Europa Clipper. What Cassini has learned about flying through the plume of material spraying from Enceladus will help inform planning for Europa Clipper, should plume activity be confirmed on Europa.

Returning to Saturn

Cassini also performed 127 close flybys of Saturn’s haze-enshrouded moon Titan, showing it to be a remarkably complex factory for organic chemicals — a natural laboratory for prebiotic chemistry. The mission investigated the cycling of liquid methane between clouds in its skies and great seas on its surface. By pulling back the veil on Titan, Cassini has ushered in a new era of extraterrestrial oceanography ­– plumbing the depths of alien seas — and delivered a fascinating example of earthlike processes occurring with chemistry and at temperatures markedly different from our home planet.

In the decades following Cassini, scientists hope to return to the Saturn system to follow up on the mission’s many discoveries. Mission concepts under consideration include spacecraft to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology.

Giant Planet Atmospheres

Atmospheric probes to all four of the outer planets have long been a priority for the science community, and the most recent Planetary Science Decadal Survey continues to support interest in sending such a mission to Saturn. By directly sampling Saturn’s upper atmosphere during its last orbits and final plunge, Cassini is laying the groundwork for an eventual Saturn atmosphere probe.

Farther out in the solar system, scientists have long had their eyes set on exploring Uranus and Neptune. So far, each of these worlds has been visited by only one brief spacecraft flyby (Voyager 2, in 1986 and 1989, respectively). Collectively, Uranus and Neptune are referred to as “ice giant” planets, because they contain large amounts of materials (like water, ammonia and methane) that form ices in the cold depths of the outer solar system. This makes them fundamentally different from the gas giant planets, Jupiter and Saturn, which are almost all hydrogen and helium, and the inner, rocky planets like Earth or Mars. It’s not clear exactly how and where the ice giants formed, why their magnetic fields are strangely oriented, and what drives geologic activity on some of their moons. These mysteries make them scientifically important, and this importance is enhanced by the discovery that many planets around other stars appear to be similar to our own ice giants.

A variety of potential mission concepts are discussed in a recently completed study, delivered to NASA in preparation for the next Decadal Survey — including orbiters, flybys and probes that would dive into Uranus’ atmosphere to study its composition. Future missions to the ice giants might explore those worlds using an approach similar to Cassini’s mission.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

More information about Cassini:

http://ift.tt/2nVxm2X

http://ift.tt/1rJDu0Q

Via NASA

from EarthSky http://ift.tt/2wUMEeJ

Saturn, backlit. Composite, made from images from Cassini while the craft was in Saturn’s shadow, on October 17, 2012, using infrared, red and violet spectral filters. Views like this one have been rare and precious, because the timing and spacecraft/planet/sun geometry has to be perfect. Previous to this image, Cassini captured a view like this in 2006. Via NASA JPL.

NASA statement via Preston Dyches at the Jet Propulsion Laboratory, Pasadena, California.

As the Cassini spacecraft nears the end of a long journey rich with scientific and technical accomplishments, it is already having a powerful influence on future exploration. In revealing that Saturn’s moon Enceladus has many of the ingredients needed for life, the mission has inspired a pivot to the exploration of ocean worlds that has been sweeping planetary science over the past decade. Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate at Headquarters in Washington, said:

Cassini has transformed our thinking in so many ways, but especially with regard to surprising places in the solar system where life could potentially gain a foothold. Congratulations to the entire Cassini team!

Onward to Europa

Jupiter’s moon Europa has been a prime target for future exploration since NASA’s Galileo mission, in the late 1990s, found strong evidence for a salty global ocean of liquid water beneath its icy crust. But the more recent revelation that a much smaller moon like Enceladus could also have not only liquid water, but also chemical energy that could potentially power biology, was staggering.

Many lessons learned during Cassini’s mission are being applied to planning NASA’s Europa Clipper mission, planned for launch in the 2020s. Europa Clipper will fly by the icy ocean moon dozens of times to investigate its potential habitability, using an orbital tour design derived from the way Cassini has explored Saturn. The Europa Clipper mission will orbit the giant planet — Jupiter in this case — using gravitational assists from its large moons to maneuver the spacecraft into repeated close encounters with Europa. This is similar to the way Cassini’s tour designers used the gravity of Saturn’s moon Titan to continually shape their spacecraft’s course.

In addition, many engineers and scientists from Cassini are serving on Europa Clipper and helping to develop its science investigations. For example, several members of the Cassini Ion and Neutral Mass Spectrometer and Cosmic Dust Analyzer teams are developing extremely sensitive, next-generation versions of their instruments for flight on Europa Clipper. What Cassini has learned about flying through the plume of material spraying from Enceladus will help inform planning for Europa Clipper, should plume activity be confirmed on Europa.

Returning to Saturn

Cassini also performed 127 close flybys of Saturn’s haze-enshrouded moon Titan, showing it to be a remarkably complex factory for organic chemicals — a natural laboratory for prebiotic chemistry. The mission investigated the cycling of liquid methane between clouds in its skies and great seas on its surface. By pulling back the veil on Titan, Cassini has ushered in a new era of extraterrestrial oceanography ­– plumbing the depths of alien seas — and delivered a fascinating example of earthlike processes occurring with chemistry and at temperatures markedly different from our home planet.

In the decades following Cassini, scientists hope to return to the Saturn system to follow up on the mission’s many discoveries. Mission concepts under consideration include spacecraft to drift on the methane seas of Titan and fly through the Enceladus plume to collect and analyze samples for signs of biology.

Giant Planet Atmospheres

Atmospheric probes to all four of the outer planets have long been a priority for the science community, and the most recent Planetary Science Decadal Survey continues to support interest in sending such a mission to Saturn. By directly sampling Saturn’s upper atmosphere during its last orbits and final plunge, Cassini is laying the groundwork for an eventual Saturn atmosphere probe.

Farther out in the solar system, scientists have long had their eyes set on exploring Uranus and Neptune. So far, each of these worlds has been visited by only one brief spacecraft flyby (Voyager 2, in 1986 and 1989, respectively). Collectively, Uranus and Neptune are referred to as “ice giant” planets, because they contain large amounts of materials (like water, ammonia and methane) that form ices in the cold depths of the outer solar system. This makes them fundamentally different from the gas giant planets, Jupiter and Saturn, which are almost all hydrogen and helium, and the inner, rocky planets like Earth or Mars. It’s not clear exactly how and where the ice giants formed, why their magnetic fields are strangely oriented, and what drives geologic activity on some of their moons. These mysteries make them scientifically important, and this importance is enhanced by the discovery that many planets around other stars appear to be similar to our own ice giants.

A variety of potential mission concepts are discussed in a recently completed study, delivered to NASA in preparation for the next Decadal Survey — including orbiters, flybys and probes that would dive into Uranus’ atmosphere to study its composition. Future missions to the ice giants might explore those worlds using an approach similar to Cassini’s mission.

The Cassini-Huygens mission is a cooperative project of NASA, ESA (European Space Agency) and the Italian Space Agency. NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington. JPL designed, developed and assembled the Cassini orbiter.

More information about Cassini:

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Most detailed color images of Saturn’s rings, ever

View larger. | Saturn’s rings – acquired by Cassini spacecraft on July 6, 2017 – from a distance of 47,000 miles (76,000 km). Image scale about 2 miles (3 km) per pixel. Phase angle, or sun-ring-spacecraft angle, is 90 degrees. Via NASA PhotoJournal.

NASA said on September 7, 2017 that the images on this page are the highest-resolution (most detailed) color images of any part of Saturn’s rings, to date. The wonderful Cassini spacecraft, whose long-running mission at Saturn will end this week, acquired them, of course. What you’re seeing here is the sunlit side of Saturn’s rings, a portion of the inner-central part of the planet’s B Ring. NASA said:

The first image (Figure A, above) is a natural color composite, created using images taken with red, green and blue spectral filters. The pale tan color is generally not perceptible with the naked eye in telescope views, especially given that Saturn has a similar hue.

The material responsible for bestowing this color on the rings—which are mostly water ice and would otherwise appear white—is a matter of intense debate among ring scientists that will hopefully be settled by new in-situ observations before the end of Cassini’s mission.

The different ringlets seen here are part of what is called the ‘irregular structure’ of the B ring. Cassini radio occultations of the rings have shown that these features have extremely sharp boundaries on even smaller scales (radially, or along the direction outward from Saturn) than the camera can resolve here. Closer to Saturn, the irregular structures become fuzzier and more rounded, less opaque, and their color contrast diminishes.

The narrow ringlets in the middle of this scene are each about 25 miles (40 km) wide, and the broader bands at right are about 200 to 300 miles (300 to 500 km) across. It remains unclear exactly what causes the variable brightness of these ringlets and bands—the basic brightness of the ring particles themselves, shadowing on their surfaces, their absolute abundance, and how densely the particles are packed, may all play a role.

View larger. | This is a color-enhanced version of the image above, via NASA PhotoJournal.

Now look at the image above. It’s a good illustration of how space scientists try to tease information out of these images. The image is color-enhanced. NASA said:

Blue colors represent areas where the spectrum at visible wavelengths is less reddish (meaning the spectrum is flatter toward red wavelengths), while red colors represent areas that are spectrally redder (meaning the spectrum has a steeper spectrum toward red wavelengths). Observations from the Voyager mission and Cassini’s visual and infrared mapping spectrometer previously showed these color variations at lower resolution, but it was not known that such well-defined color contrasts would be this sharply defined down to the scale (radial scale) of a couple of miles or kilometers, as seen here.

Analysis of additional images from this observation, taken using infrared spectral filters sensitive to absorption of light by water ice, indicates that the areas that appear more visibly reddish in the color-enhanced version are also richer in water ice.

NASA has more to say; click here to read it.

Bottom line: Photos on this page are the highest-resolution (most detailed) color images of Saturn’s rings, ever, acquired by the Cassini spacecraft on July 6, 2017. We will miss Cassini, when its mission ends this week!

from EarthSky http://ift.tt/2gXVa4L

View larger. | Saturn’s rings – acquired by Cassini spacecraft on July 6, 2017 – from a distance of 47,000 miles (76,000 km). Image scale about 2 miles (3 km) per pixel. Phase angle, or sun-ring-spacecraft angle, is 90 degrees. Via NASA PhotoJournal.

NASA said on September 7, 2017 that the images on this page are the highest-resolution (most detailed) color images of any part of Saturn’s rings, to date. The wonderful Cassini spacecraft, whose long-running mission at Saturn will end this week, acquired them, of course. What you’re seeing here is the sunlit side of Saturn’s rings, a portion of the inner-central part of the planet’s B Ring. NASA said:

The first image (Figure A, above) is a natural color composite, created using images taken with red, green and blue spectral filters. The pale tan color is generally not perceptible with the naked eye in telescope views, especially given that Saturn has a similar hue.

The material responsible for bestowing this color on the rings—which are mostly water ice and would otherwise appear white—is a matter of intense debate among ring scientists that will hopefully be settled by new in-situ observations before the end of Cassini’s mission.

The different ringlets seen here are part of what is called the ‘irregular structure’ of the B ring. Cassini radio occultations of the rings have shown that these features have extremely sharp boundaries on even smaller scales (radially, or along the direction outward from Saturn) than the camera can resolve here. Closer to Saturn, the irregular structures become fuzzier and more rounded, less opaque, and their color contrast diminishes.

The narrow ringlets in the middle of this scene are each about 25 miles (40 km) wide, and the broader bands at right are about 200 to 300 miles (300 to 500 km) across. It remains unclear exactly what causes the variable brightness of these ringlets and bands—the basic brightness of the ring particles themselves, shadowing on their surfaces, their absolute abundance, and how densely the particles are packed, may all play a role.

View larger. | This is a color-enhanced version of the image above, via NASA PhotoJournal.

Now look at the image above. It’s a good illustration of how space scientists try to tease information out of these images. The image is color-enhanced. NASA said:

Blue colors represent areas where the spectrum at visible wavelengths is less reddish (meaning the spectrum is flatter toward red wavelengths), while red colors represent areas that are spectrally redder (meaning the spectrum has a steeper spectrum toward red wavelengths). Observations from the Voyager mission and Cassini’s visual and infrared mapping spectrometer previously showed these color variations at lower resolution, but it was not known that such well-defined color contrasts would be this sharply defined down to the scale (radial scale) of a couple of miles or kilometers, as seen here.

Analysis of additional images from this observation, taken using infrared spectral filters sensitive to absorption of light by water ice, indicates that the areas that appear more visibly reddish in the color-enhanced version are also richer in water ice.

NASA has more to say; click here to read it.

Bottom line: Photos on this page are the highest-resolution (most detailed) color images of Saturn’s rings, ever, acquired by the Cassini spacecraft on July 6, 2017. We will miss Cassini, when its mission ends this week!

from EarthSky http://ift.tt/2gXVa4L

Use Cassiopeia to find Andromeda galaxy

Tonight, try star-hopping to the Andromeda galaxy from the constellation Cassiopeia the Queen. In a dark sky, you might even spot this hazy patch of light with no optical aid, as the ancient stargazers did before the days of light pollution.

But what if you can’t find the Andromeda galaxy with the eyes alone? Some stargazers use binoculars and star-hop to the Andromeda galaxy via this W-shaped constellation.

View larger. Anthony Lynch Photography provided this beautiful shot of a Perseid meteor and the Andromeda galaxy. Thank you, Anthony!

Cassiopeia appears low in the northeast sky at nightfall and early evening, then swings upward as evening deepens into late night. In the wee hours after midnight, Cassiopeia is found high over Polaris, the North Star. Note that one half of the W is more deeply notched than the other half. This deeper V is your “arrow” in the sky, pointing to the Andromeda galaxy.

Remember, on a dark night, this galaxy looks like a faint smudge of light. Once you’ve found it with the unaided eye or binoculars, try with a telescope – if you have one. The Andromeda galaxy is the nearest large spiral galaxy to our Milky Way. It’s about 2.5 million light-years away, teeming with hundreds of billions of stars.

View larger. | Many people find the Andromeda galaxy from the two streams of stars extending from the Great Square (they are the constellation Andromeda). Or they find the galaxy via the constellation Cassiopeia. This photo via EarthSky Facebook friend Cattleya Flores Viray.

View larger. | Draw an imaginary line from the star Kappa Cassiopeiae (abbreviated Kappa) through the star Schedar, then go about 3 times the Kappa-Schedar distance to locate the Andromeda galaxy (Messier 31).

Bottom line: Some prefer the constellation Cassiopedia – which is easy to find, shaped like an M or W – as a jumping off point for locating the Andromeda galaxy.

More about M31: Great galaxy in Andromeda

Use the Great Square of Pegasus to find the Andromeda galaxy

Donate: Your support means the world to us

from EarthSky http://ift.tt/1vmtmYk

Tonight, try star-hopping to the Andromeda galaxy from the constellation Cassiopeia the Queen. In a dark sky, you might even spot this hazy patch of light with no optical aid, as the ancient stargazers did before the days of light pollution.

But what if you can’t find the Andromeda galaxy with the eyes alone? Some stargazers use binoculars and star-hop to the Andromeda galaxy via this W-shaped constellation.

View larger. Anthony Lynch Photography provided this beautiful shot of a Perseid meteor and the Andromeda galaxy. Thank you, Anthony!

Cassiopeia appears low in the northeast sky at nightfall and early evening, then swings upward as evening deepens into late night. In the wee hours after midnight, Cassiopeia is found high over Polaris, the North Star. Note that one half of the W is more deeply notched than the other half. This deeper V is your “arrow” in the sky, pointing to the Andromeda galaxy.

Remember, on a dark night, this galaxy looks like a faint smudge of light. Once you’ve found it with the unaided eye or binoculars, try with a telescope – if you have one. The Andromeda galaxy is the nearest large spiral galaxy to our Milky Way. It’s about 2.5 million light-years away, teeming with hundreds of billions of stars.

View larger. | Many people find the Andromeda galaxy from the two streams of stars extending from the Great Square (they are the constellation Andromeda). Or they find the galaxy via the constellation Cassiopeia. This photo via EarthSky Facebook friend Cattleya Flores Viray.

View larger. | Draw an imaginary line from the star Kappa Cassiopeiae (abbreviated Kappa) through the star Schedar, then go about 3 times the Kappa-Schedar distance to locate the Andromeda galaxy (Messier 31).

Bottom line: Some prefer the constellation Cassiopedia – which is easy to find, shaped like an M or W – as a jumping off point for locating the Andromeda galaxy.

More about M31: Great galaxy in Andromeda

Use the Great Square of Pegasus to find the Andromeda galaxy

Donate: Your support means the world to us

from EarthSky http://ift.tt/1vmtmYk

Ultraviolet light key to life search, too?

Artist’s concept of an other-worldly ocean on a distant exoplanet, under the light of a red sun, via CfA.

Our sun emits its own unique balance of “light,” a combination of different forms of radiation across most of the electromagnetic spectrum. It emits visible light, of course, and our eyes are most sensitive to that form of the sun’s radiation. And it also emits in the ultraviolet, which is the form of radiation we’re trying to block when we apply sunscreen. But some stars emit light primarily in the ultraviolet, or UV, part of the spectrum. Recent research from Harvard astronomers suggests that UV light might have played a critical role in the emergence of life on Earth. These astronomers believe it could be a key for where to look for life elsewhere in the universe, too.

Their study was published this summer in the peer-reviewed Astrophysical Journal and is available online.

Sukrit Ranjan of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts led the new study. It suggests that red dwarf stars – by far the most common sort of stars, and thought by some to be the best star systems in which to search for life – might not emit enough UV light to kick-start the biological processes most familiar to our planet. The statement from the Harvard astronomers pointed out:

For example, certain levels of UV might be necessary for the formation of ribonucleic acid, a molecule necessary for all forms of known life.

Ranjan further explained:

It would be like having a pile of wood and kindling and wanting to light a fire, but not having a match. Our research shows that the right amount of UV light might be one of the matches that gets life as we know it to ignite.

Red dwarf stars are smaller and less massive than our sun. Recently discovered planetary systems with potential habitable zones – zones at distances from their stars where liquid water can exist – include red dwarfs such as Proxima Centauri, TRAPPIST-1, and LHS 1140.

These scientists used computer models and the known properties of red dwarfs to estimate that the surface of rocky planets in the potentially habitable zones around red dwarfs would experience 100 to 1,000 times less of the ultraviolet light that may be important to the emergence of life than the young Earth would have. They said that chemistry that depends on UV light might shut down at such low levels, and even if it does proceed, it could operate at a much slower rate than on the young Earth, possibly delaying the advent of life.

And there’s another wrinkle in the question of life on exoplanets, related to UV radiation. Previous studies have shown that the red dwarf stars in systems such as TRAPPIST-1 might erupt with dramatic flares in UV. If the flares deliver too much energy, they might severely damage surrounding planets’ atmosphere, inhibiting life.

Ironically, these UV flares might also provide enough energy to compensate for the lower levels of UV light steadily produced by the star. Co-author Robin Wordsworth of the Harvard School of Engineering and Applied Science said:

It may be a matter of finding the sweet spot. There needs to be enough ultraviolet light to trigger the formation of life, but not so much that it erodes and removes the planet’s atmosphere.

Another co-author, Dimitar Sasselov, also of the CfA said:

We still have a lot of work to do in the laboratory and elsewhere to determine how factors, including UV, play into the question of life. Also, we need to determine whether life can form at much lower UV levels than we experience here on Earth.

Read more about this new study from CfA

Bottom line: Scientists at Harvard studied the role of ultraviolet, or UV, radiation in the possibility of life on other planets.

from EarthSky http://ift.tt/2xTT2lp

Artist’s concept of an other-worldly ocean on a distant exoplanet, under the light of a red sun, via CfA.

Our sun emits its own unique balance of “light,” a combination of different forms of radiation across most of the electromagnetic spectrum. It emits visible light, of course, and our eyes are most sensitive to that form of the sun’s radiation. And it also emits in the ultraviolet, which is the form of radiation we’re trying to block when we apply sunscreen. But some stars emit light primarily in the ultraviolet, or UV, part of the spectrum. Recent research from Harvard astronomers suggests that UV light might have played a critical role in the emergence of life on Earth. These astronomers believe it could be a key for where to look for life elsewhere in the universe, too.

Their study was published this summer in the peer-reviewed Astrophysical Journal and is available online.

Sukrit Ranjan of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts led the new study. It suggests that red dwarf stars – by far the most common sort of stars, and thought by some to be the best star systems in which to search for life – might not emit enough UV light to kick-start the biological processes most familiar to our planet. The statement from the Harvard astronomers pointed out:

For example, certain levels of UV might be necessary for the formation of ribonucleic acid, a molecule necessary for all forms of known life.

Ranjan further explained:

It would be like having a pile of wood and kindling and wanting to light a fire, but not having a match. Our research shows that the right amount of UV light might be one of the matches that gets life as we know it to ignite.

Red dwarf stars are smaller and less massive than our sun. Recently discovered planetary systems with potential habitable zones – zones at distances from their stars where liquid water can exist – include red dwarfs such as Proxima Centauri, TRAPPIST-1, and LHS 1140.

These scientists used computer models and the known properties of red dwarfs to estimate that the surface of rocky planets in the potentially habitable zones around red dwarfs would experience 100 to 1,000 times less of the ultraviolet light that may be important to the emergence of life than the young Earth would have. They said that chemistry that depends on UV light might shut down at such low levels, and even if it does proceed, it could operate at a much slower rate than on the young Earth, possibly delaying the advent of life.

And there’s another wrinkle in the question of life on exoplanets, related to UV radiation. Previous studies have shown that the red dwarf stars in systems such as TRAPPIST-1 might erupt with dramatic flares in UV. If the flares deliver too much energy, they might severely damage surrounding planets’ atmosphere, inhibiting life.

Ironically, these UV flares might also provide enough energy to compensate for the lower levels of UV light steadily produced by the star. Co-author Robin Wordsworth of the Harvard School of Engineering and Applied Science said:

It may be a matter of finding the sweet spot. There needs to be enough ultraviolet light to trigger the formation of life, but not so much that it erodes and removes the planet’s atmosphere.

Another co-author, Dimitar Sasselov, also of the CfA said:

We still have a lot of work to do in the laboratory and elsewhere to determine how factors, including UV, play into the question of life. Also, we need to determine whether life can form at much lower UV levels than we experience here on Earth.

Read more about this new study from CfA

Bottom line: Scientists at Harvard studied the role of ultraviolet, or UV, radiation in the possibility of life on other planets.

from EarthSky http://ift.tt/2xTT2lp

X-rays astronomers explore possible planet-hosting stars

Astronomers are using studies of the X-rays emitted by stars to learn more about how hospitable distant stars might be to life on other planets. A star’s X-ray emission mirrors its magnetic activity. In the early life of a star, this activity includes energetic radiation and eruptions that could impact surrounding planets and possibly keep life from gaining a foothold. In this study, researchers examined 24 stars like our sun. Each star was at least one billion years old. The X-ray data revealed that stars like our sun and its less massive cousins calm down “surprisingly quickly” after a turbulent youth. That’s good news for the possibility of life on distant planets.

A paper describing these results has been accepted for publication in the peer-reviewed Monthly Notices of the Royal Astronomical Society, and is available online.

Since X-rays don’t penetrate Earth’s atmosphere, the astronomers used two Earth-orbiting observatories – Chandra and XMM-Newton – to collect data about these stars.

Why are stars so very magnetically active when they are young? Young stars are rotating – or spinning on their axes – more rapidly than older stars. In their statement, the astronomers pointed out that a rotating star loses energy over time, and spins more slowly. As that happens, the magnetic activity level, along with the associated X-ray emission, drops. A September 6, 2017 statement from Chandra explained:

Although it is not certain why older stars settle down relatively quickly, astronomers have ideas they are exploring. One possibility is that the decrease in rate of spin of the older stars occurs more quickly than it does for the younger stars. Another possibility is that the X-ray brightness declines more quickly with time for older, more slowly rotating stars than it does for younger stars.

These astronomers also pointed out that – to understand how quickly stellar magnetic activity level changes over time – they needed accurate ages for many different stars. They said:

This is a difficult task, but new precise age estimates have recently become available from studies of the way that a star pulsates using NASA’s Kepler and ESA’s CoRoT missions. These new age estimates were used for most of the 24 stars studied here.

Artist’s illustration of a comparatively calm, older sunlike stars with an orbiting planet. The large dark area is a “coronal hole,” a phenomenon associated with relatively low levels of magnetic activity. The inset box shows the Chandra data of 1 of the 24 stars observed in this new study. It’s a 2-billion-year-old star called GJ 176, located 30 light years from Earth. Image via Chandra.

Bottom line: Astronomers recently used X-ray data from Chandra and XMM-Newton to study how quickly possible planet-hosting stars settle down after a turbulent youth. They found the stars settle “surprisingly quickly.”

Via Chandra

from EarthSky http://ift.tt/2wSjdeL

Astronomers are using studies of the X-rays emitted by stars to learn more about how hospitable distant stars might be to life on other planets. A star’s X-ray emission mirrors its magnetic activity. In the early life of a star, this activity includes energetic radiation and eruptions that could impact surrounding planets and possibly keep life from gaining a foothold. In this study, researchers examined 24 stars like our sun. Each star was at least one billion years old. The X-ray data revealed that stars like our sun and its less massive cousins calm down “surprisingly quickly” after a turbulent youth. That’s good news for the possibility of life on distant planets.

A paper describing these results has been accepted for publication in the peer-reviewed Monthly Notices of the Royal Astronomical Society, and is available online.

Since X-rays don’t penetrate Earth’s atmosphere, the astronomers used two Earth-orbiting observatories – Chandra and XMM-Newton – to collect data about these stars.

Why are stars so very magnetically active when they are young? Young stars are rotating – or spinning on their axes – more rapidly than older stars. In their statement, the astronomers pointed out that a rotating star loses energy over time, and spins more slowly. As that happens, the magnetic activity level, along with the associated X-ray emission, drops. A September 6, 2017 statement from Chandra explained:

Although it is not certain why older stars settle down relatively quickly, astronomers have ideas they are exploring. One possibility is that the decrease in rate of spin of the older stars occurs more quickly than it does for the younger stars. Another possibility is that the X-ray brightness declines more quickly with time for older, more slowly rotating stars than it does for younger stars.

These astronomers also pointed out that – to understand how quickly stellar magnetic activity level changes over time – they needed accurate ages for many different stars. They said:

This is a difficult task, but new precise age estimates have recently become available from studies of the way that a star pulsates using NASA’s Kepler and ESA’s CoRoT missions. These new age estimates were used for most of the 24 stars studied here.

Artist’s illustration of a comparatively calm, older sunlike stars with an orbiting planet. The large dark area is a “coronal hole,” a phenomenon associated with relatively low levels of magnetic activity. The inset box shows the Chandra data of 1 of the 24 stars observed in this new study. It’s a 2-billion-year-old star called GJ 176, located 30 light years from Earth. Image via Chandra.

Bottom line: Astronomers recently used X-ray data from Chandra and XMM-Newton to study how quickly possible planet-hosting stars settle down after a turbulent youth. They found the stars settle “surprisingly quickly.”

Via Chandra

from EarthSky http://ift.tt/2wSjdeL