Jul 30 2015

From The Space Library

Release 15-159 NASA Selects Proposals to Study Neutron Stars, Black Holes and More

NASA has selected five proposals submitted to its Explorers Program to conduct focused scientific investigations and develop instruments that fill the scientific gaps between the agency’s larger missions.

The selected proposals, three Astrophysics Small Explorer missions and two Explorer Missions of Opportunity, will study polarized X-ray emissions from neutron star-black hole binary systems, the exponential expansion of space in the early universe, galaxies in the early universe, and star formation in our Milky Way galaxy.

“The Explorers Program brings out some of the most creative ideas for missions to help unravel the mysteries of the Universe,” said John Grunsfeld, NASA’s Associate Administrator for Science at NASA Headquarters, in Washington. “The program has resulted in great missions that have returned transformational science, and these selections promise to continue that tradition.”

The proposals were selected based on potential science value and feasibility of development plans. One of each mission type will be selected by 2017, after concept studies and detailed evaluations, to proceed with construction and launch, the earliest of which could be launched by 2020. Small Explorer mission costs are capped at $125 million each, excluding the launch vehicle, and Mission of Opportunity costs are capped at $65 million each.

Each Astrophysics Small Explorer mission will receive $1 million to conduct an 11-month mission concept study. The selected proposals are:

SPHEREx: An All-Sky Near-Infrared Spectral Survey

• James Bock, principal investigator at the California Institute of Technology in Pasadena, California
• SPHEREx will perform an all-sky near infrared spectral survey to probe the origin of our Universe; explore the origin and evolution of galaxies, and explore whether planets around other stars could harbor life.

Imaging X-ray Polarimetry Explorer (IXPE)

• Martin Weisskopf, principal investigator at NASA’s Marshall Space Flight Center in Huntsville, Alabama
• IXPE uses X-ray polarimetry, which is the measurement and interpretation of the polarization of electromagnetic waves, to improve our understanding of how X-ray emission is produced in objects such as neutron stars, pulsar wind nebulae, and stellar and supermassive black holes.

Polarimeter for Relativistic Astrophysical X-ray Sources (PRAXyS)

• Keith Jahoda, principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland
• PRAXyS uses X-ray polarimetry to characterize the geometry and behavior of X-ray sources including super-massive black holes, pulsars, magnetars and supernovae.

Missions of Opportunity will receive $250,000 to conduct an eleven-month implementation concept study. The selected proposals are:

GUSTO: Gal/Xgal U/LDB Spectroscopic/Stratospheric THz Observatory

• Christopher Walker, principal investigator at the University of Arizona in Tucson
• GUSTO is a balloon-borne observatory of high-frequency radio emissions from our Milky Way galaxy and a nearby companion galaxy, the Large Magellanic Cloud, to study the life cycle of interstellar material.

U.S. Participation in the LiteBIRD Cosmic Microwave Background Polarization Survey

• Adrian Lee, principal investigator at the University of California in Berkeley
• The Japanese LiteBIRD mission with U.S. contributions to the payload will map polarized fluctuations in the Cosmic Microwave Background, or the leftover thermal radiation from the Big Bang, to search for the signature of gravitational waves from inflation, potentially shedding light on the universe a fraction of a second after the Big Bang.

The Explorers Program is the oldest continuous NASA program designed to provide frequent, low-cost access to space using principal investigator-led space science investigations relevant to the Science Mission Directorate’s astrophysics and heliophysics programs. Since the Explorer 1 launch in 1958, which discovered the Earth’s radiation belts, the Explorers Program has launched more than 90 missions, including the Uhuru and Cosmic Background Explorer (COBE) missions that led to Nobel prizes for their investigators.

The program is managed by Goddard for NASA's Science Mission Directorate, which conducts a wide variety of research and scientific exploration programs for Earth studies, space weather, the solar system and universe.

Release 15-160 NASA's Spitzer Confirms Closest Rocky Exoplanet

Using NASA's Spitzer Space Telescope, astronomers have confirmed the discovery of the nearest rocky planet outside our solar system, larger than Earth and a potential gold mine of science data.

Dubbed HD 219134b, this exoplanet, which orbits too close to its star to sustain life, is a mere 21 light-years away. While the planet itself can't be seen directly, even by telescopes, the star it orbits is visible to the naked eye in dark skies in the Cassiopeia constellation, near the North Star.

HD 219134b is also the closest exoplanet to Earth to be detected transiting, or crossing in front of, its star and, therefore, perfect for extensive research.

"Transiting exoplanets are worth their weight in gold because they can be extensively characterized," said Michael Werner, the project scientist for the Spitzer mission at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California. "This exoplanet will be one of the most studied for decades to come."

The planet, initially discovered using HARPS-North instrument on the Italian 3.6-meter Galileo National Telescope in the Canary Islands, is the subject of a study accepted for publication in the journal Astronomy & Astrophysics.

Study lead author Ati Motalebi of the Geneva Observatory in Switzerland said she believes the planet is the ideal target for NASA’s James Webb Space Telescope in 2018.

"Webb and future large, ground-based observatories are sure to point at it and examine it in detail,” Motalebi said.

Only a small fraction of exoplanets can be detected transiting their stars due to their relative orientation to Earth. When the orientation is just right, the planet’s orbit places it between its star and Earth, dimming the detectable light of its star. It’s this dimming of the star that is actually captured by observatories such as Spitzer, and can reveal not only the size of the planet but also clues about its composition.

"Most of the known planets are hundreds of light-years away. This one is practically a next-door neighbor," said astronomer and study co-author Lars A. Buchhave of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts. For reference, the closest known planet is GJ674b at 14.8 light-years away; its composition is unknown.

HD 219134b was first sighted by the HARPS-North instrument and a method called the radial velocity technique, in which a planet's mass and orbit can be measured by the tug it exerts on its host star. The planet was determined to have a mass 4.5 times that of Earth, and a speedy three-day orbit around its star.

Spitzer followed up on the finding, discovering the planet transits its star. Infrared measurements from Spitzer revealed the planet's size, about 1.6 times that of Earth. Combining the size and mass gives it a density of 3.5 ounces per cubic inch (six grams per cubic centimeter) -- confirming HD 219134b is a rocky planet.

Now that astronomers know HD 219134b transits its star, scientists will be scrambling to observe it from the ground and space. The goal is to tease chemical information out of the dimming starlight as the planet passes before it. If the planet has an atmosphere, chemicals in it can imprint patterns in the observed starlight.

Rocky planets such as this one, with bigger-than-Earth proportions, belong to a growing class of planets termed super-Earths.

"Thanks to NASA's Kepler mission, we know super-Earths are ubiquitous in our galaxy, but we still know very little about them," said co-author Michael Gillon of the University of Liege in Belgium, lead scientist for the Spitzer detection of the transit. "Now we have a local specimen to study in greater detail. It can be considered a kind of Rosetta Stone for the study of super-Earths."

Further observations with HARPS-North also revealed three more planets in the same star system, farther than HD 219134b. Two are relatively small and not too far from the star. Small, tightly packed multi-planet systems are completely different from our own solar system, but, like super-Earths, are being found in increasing numbers.

JPL manages the Spitzer mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology (Caltech) in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company in Littleton, Colorado. Data are archived at the Infrared Science Archive, housed at Caltech’s Infrared Processing and Analysis Center.

Release 15-162 California “Rain Debt” Equal to Average Full Year of Precipitation

A new NASA study has concluded California accumulated a debt of about 20 inches of precipitation between 2012 and 2015 -- the average amount expected to fall in the state in a single year. The deficit was driven primarily by a lack of air currents moving inland from the Pacific Ocean that are rich in water vapor.

In an average year, 20 to 50 percent of California's precipitation comes from relatively few, but extreme events called atmospheric rivers that move from over the Pacific Ocean to the California coast.

"When they say that an atmospheric river makes landfall, it's almost like a hurricane, without the winds. They cause extreme precipitation," said study lead author Andrey Savtchenko at NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Savtchenko and his colleagues examined data from 17 years of satellite observations and 36 years of combined observations and model data to understand how precipitation has varied in California since 1979. The results were published Thursday in Journal of Geophysical Research – Atmospheres, a journal of the American Geophysical Union.

The state as a whole can expect an average of about 20 inches of precipitation each year, with regional differences. But, the total amount can vary as much as 30 percent from year to year, according to the study.

In non-drought periods, wet years often alternate with dry years to balance out in the short term. However, from 2012 to 2014, California accumulated a deficit of almost 13 inches, and the 2014-2015 wet season increased the debt another seven inches, for a total 20 inches accumulated deficit during the course of three dry years.

The majority of that precipitation loss is attributed to a high-pressure system in the atmosphere over the eastern Pacific Ocean that has interfered with the formation of atmospheric rivers since 2011.

Atmospheric rivers occur all over the world. They are narrow, concentrated tendrils of water vapor that travel through the atmosphere similar to, and sometimes with, the winds of a jet stream. Like a jet stream, they typically travel from west to east. The ones destined for California originate over the tropical Pacific, where warm ocean water evaporates a lot of moisture into the air. The moisture-rich atmospheric rivers, informally known as the Pineapple Express, then break northward toward North America.

Earlier this year, a NASA research aircraft participated in the CalWater 2015 field campaign to improve understanding of when and how atmospheric rivers reach California.

Some of the water vapor rains out over the ocean, but the show really begins when an atmospheric river reaches land. Two reached California around Dec. 1 and 10, 2014, and brought more than three inches of rain, according to NASA's Tropical Rainfall Measuring Mission (TRMM)'s multi-satellite dataset. The inland terrain, particularly mountains, force the moist air to higher altitudes where lower pressure causes it to expand and cool. The cooler air condenses the concentrated pool of water vapor into torrential rains, or snowfall as happens over the Sierra Nevada Mountains, where water is stored in the snowpack until the spring melt just before the growing season.

The current drought isn't the first for California. Savtchenko and his colleagues recreated a climate record for 1979 to the present using the Modern-Era Retrospective Analysis for Research and Applications, or MERRA. Their efforts show that a 27.5 inch deficit of rain and snow occurred in the state between 1986 and 1994.

"Drought has happened here before. It will happen again, and some research groups have presented evidence it will happen more frequently as the planet warms," Savtchenko said. "But, even if the climate doesn’t change, are our demands for fresh water sustainable?"

The current drought has been notably severe because, since the late 1980s, California's population, industry and agriculture have experienced tremendous growth, with a correlating growth in their demand for water. Human consumption has depleted California's reservoirs and groundwater reserves, as shown by data from NASA's Gravity Recovery and Climate Experiment (GRACE) mission, leading to mandatory water rationing.

"The history of the American West is written in great decade-long droughts followed by multi-year wet periods," said climatologist Bill Patzert at NASA's Jet Propulsion Laboratory in Pasadena, California. He was not involved in the research. "Savtchenko and his team have shown how variable California rainfall is.”

According to Patzert, this study added nuance to how scientists may interpret the atmospheric conditions that cause atmospheric rivers and an El Niño's capacity to bust the drought. Since March, rising sea surface temperatures in the central equatorial Pacific have indicated the formation of El Niño conditions. El Niño conditions are often associated with higher rainfall to the western United States, but it’s not guaranteed.

Savtchenko and his colleagues show that El Niño contributes only six percent to California's precipitation variability and is one factor among other, more random effects that influence how much rainfall the state receives. While it’s more likely El Niño increases precipitation in California, it’s still possible it will have no, or even a drying, effect.

A strong El Niño that lasts through the rainy months, from November to March, is more likely to increase the amount of rain that reaches California, and Savtchenko noted the current El Niño is quickly strengthening.

The National Oceanic and Atmospheric Administration (NOAA), which monitors El Niño events, ranks it as the third strongest in the past 65 years for May and June. Still, it will likely take several years of higher than normal rain and snowfall to recover from the current drought.

"If this El Niño holds through winter, California’s chances to recoup some of the precipitation increase. Unfortunately, so do the chances of floods and landslides," Savtchenko said. “Most likely the effects would be felt in late 2015-2016.”