NASA Voyager 2 Could Be Nearing Interstellar Space

NASA - Voyager 1 & 2 Mission patch.

Oct. 5, 2018

NASA's Voyager 2 probe, currently on a journey toward interstellar space, has detected an increase in cosmic rays that originate outside our solar system. Launched in 1977, Voyager 2 is a little less than 11 billion miles (about 17.7 billion kilometers) from Earth, or more than 118 times the distance from Earth to the Sun.

Since 2007 the probe has been traveling through the outermost layer of the heliosphere -- the vast bubble around the Sun and the planets dominated by solar material and magnetic fields. Voyager scientists have been watching for the spacecraft to reach the outer boundary of the heliosphere, known as the heliopause. Once Voyager 2 exits the heliosphere, it will become the second human-made object, after Voyager 1, to enter interstellar space.

Since late August, the Cosmic Ray Subsystem instrument on Voyager 2 has measured about a 5 percent increase in the rate of cosmic rays hitting the spacecraft compared to early August. The probe's Low-Energy Charged Particle instrument has detected a similar increase in higher-energy cosmic rays.

Cosmic rays are fast-moving particles that originate outside the solar system. Some of these cosmic rays are blocked by the heliosphere, so mission planners expect that Voyager 2 will measure an increase in the rate of cosmic rays as it approaches and crosses the boundary of the heliosphere.

Image above: This graphic shows the position of the Voyager 1 and Voyager 2 probes relative to the heliosphere, a protective bubble created by the Sun that extends well past the orbit of Pluto. Voyager 1 crossed the heliopause, or the edge of the heliosphere, in 2012. Voyager 2 is still in the heliosheath, or the outermost part of the heliosphere. Image Credits: NASA/JPL-Caltech.

In May 2012, Voyager 1 experienced an increase in the rate of cosmic rays similar to what Voyager 2 is now detecting. That was about three months before Voyager 1 crossed the heliopause and entered interstellar space.

However, Voyager team members note that the increase in cosmic rays is not a definitive sign that the probe is about to cross the heliopause. Voyager 2 is in a different location in the heliosheath -- the outer region of the heliosphere -- than Voyager 1 had been, and possible differences in these locations means Voyager 2 may experience a different exit timeline than Voyager 1.

The fact that Voyager 2 may be approaching the heliopause six years after Voyager 1 is also relevant, because the heliopause moves inward and outward during the Sun's 11-year activity cycle. Solar activity refers to emissions from the Sun, including solar flares and eruptions of material called coronal mass ejections. During the 11-year solar cycle, the Sun reaches both a maximum and a minimum level of activity.

Voyager 2. Animation Credit: NASA

"We're seeing a change in the environment around Voyager 2, there's no doubt about that," said Voyager Project Scientist Ed Stone, based at Caltech in Pasadena. "We're going to learn a lot in the coming months, but we still don't know when we'll reach the heliopause. We're not there yet -- that's one thing I can say with confidence."

The Voyager spacecraft were built by NASA's Jet Propulsion Laboratory in Pasadena, California, which continues to operate both. JPL is a division of Caltech. The Voyager missions are a part of the NASA Heliophysics System Observatory, managed by the Heliophysics Division of the Science Mission Directorate in Washington.

For more information about the Voyager spacecraft, visit:

https://www.nasa.gov/voyager

https://voyager.jpl.nasa.gov

Images (mentioned), Text, Credits: NASA/Tony Greicius/Karen Fox/JPL/Calla Cofield/Jia-Rui Cook.

Greetings, Orbiter.ch

Space Station Science Highlights: Week of October 1, 2018

ISS - Expedition 57 Mission patch.

Oct. 5, 2018

It was a busy week aboard the International Space Station as Expedition 56 Commander Drew Feustel and Flight Engineer Ricky Arnold of NASA, along with Flight Engineer and Soyuz Commander Oleg Artemyev of the Russian space agency Roscosmos returned to Earth. With their departure comes the start of Expedition 57 and a new space station commander.

Image above: NASA astronauts Drew Feustel and Ricky Arnold, along with Oleg Artemyev of Roscosmos returned aboard the 54S Soyuz spacecraft. Image Credit: NASA.

Feustel, Expedition 56 Commander, handed off the station command to Alexander Gerst of the European Space Agency during a Change of Command Ceremony on Wednesday.

In addition to all of the crew excitement, science was being conducted in the areas of human research, technology development, plant biology and more.

Learn more about the science happening on station below:

Blood and Saliva samples collected for ambient return

Protecting crew health is important as NASA prepares for long duration, deep-space missions. Functional Immune studies previously uninvestigated areas of the body’s immune response and if spaceflight alters a crew member’s susceptibility to disease.

The immune system is a complex weaving of biological structures and processes. Decreased activity in just one piece can cause changes in disease risk within the human body. Studies have shown in microgravity there are immune system modifications. This may create an environment where, in some crew members, rashes, unusual allergies and latent virus reactivation may present themselves.

This week, crew members collected saliva and blood samples for an ambient return aboard the 54S Soyuz spacecraft.

Read more about the investigation here: https://www.nasa.gov/mission_pages/station/research/news/functional_immune

Japanese satellite prepares for upcoming deployments

The JEM Small Satellite Orbital Deployer (J-SSOD) provides a novel, safe, small satellite launching capability to the space station. The J-SSOD is a unique satellite launcher, handled by the Japanese Experiment Module Remote Manipulator System (JEMRMS), which provides containment and deployment mechanisms for several individual small satellites.

Animation above: The J-SSOD-10 was installed onto the MPEP in preparation for this weekend’s satellite deployments. Animation Credit: NASA.

This week, the crew installed the J-SSOD-10 onto the Multipurpose Experiment Platform (MPEP) in preparation for this weekend’s satellite deployments.

Arabidopsis plants thinned to allow for more growth

Understanding how plants grow and thrive in harsh environments, both on Earth and in space, is important for advancements in agriculture. The Advanced Plant Habitat Facility (Plant Habitat) is a fully automated facility used to conduct plant bioscience research and provides a large, enclosed, environmentally controlled chamber aboard the space station.

Image above: NASA astronaut Serena M. Auñón-Chancellor thinned the Arabidopsis plants, growing as a part of the Plant Habitat-1 investigation, contained within the Advanced Plant Habitat. Image Credit: NASA.

The crew performed plant thinning as a part of the Plant Habitat-1 investigation. In this activity, the young Arabidopsis plants, small flowering plants related to cabbage and mustard, were thinned. This gives the remaining plants a better chance to continue their growth.

Learn more about the Plant Habitat here: https://www.nasa.gov/mission_pages/station/research/Giving_Roots_and_Shoots_Their_Space_APH

Other work was done on these investigations:

- BEST seeks to advance use of sequencing DNA and RNA in space: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7687

- Food Acceptability examines changes in how food appeals to crew members during their time aboard the station. Acceptability of food – whether crew members like and actually eat something – may directly affect crew caloric intake and associated nutritional benefits: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7562

- The Sally Ride EarthKAM program allows students to remotely control a digital camera mounted on the space station and use it to take photographs of coastlines, mountain ranges and other features and phenomena. The images are posted online where the public and participating classrooms can view Earth from the station’s unique vantage point: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=87

- The Life Sciences Glovebox (LSG) is a sealed work area that accommodates life science and technology investigations in a workbench-type environment. Due to its larger size, two crew members can work in the LSG simultaneously: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=7676

- MATISS investigates the antibacterial properties of materials in space for possible application in future spacecraft: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7333

- MobiPV aims to improve the efficiency of activity execution by giving crewmembers a wireless set of wearable, portable devices that utilize voice navigation and a direct audio/video link to ground experts: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1818

- Meteor is a visible spectroscopy instrument used to observe meteors in Earth orbit: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1174

Space to Ground: Hello, Goodbye: 10/05/2018

Related links:

Expedition 57: https://www.nasa.gov/mission_pages/station/expeditions/expedition57/index.html

Functional Immune: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=2011

JEM Small Satellite Orbital Deployer (J-SSOD): https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=883

Plant Habitat: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=2036

Plant Habitat-1: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=2032

Spot the Station: https://spotthestation.nasa.gov/

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Animation (mentioned), Video (NASA), Text, Credits: NASA/Erling Holm/Yuri Guinart-Ramirez, Lead Increment Scientist Expeditions 55 & 56.

Best regards, Orbiter.ch

Sentinel-2 maps Indonesia earthquake

ESA - Sentinel 2 Mission logo.

5 October 2018

A 7.5-magnitude earthquake and tsunami hit Indonesia on 28 September, destroying homes and hundreds of lives. As the death toll continues to rise, the effects of this natural disaster are far-reaching, with hundreds of thousands of people seeking access food, water and shelter in the aftermath of this tragedy.

Fault line land movement

Satellite data can be used to support international disaster risk management efforts, such as those in Indonesia. One of the ways in which ESA is contributing to this area is through leading a range of activities in the framework of the Committee on Earth Observation Satellites (CEOS) Working Group on Disasters.

In particular, the Geohazards Office, led by the French Geological Survey (BRGM) liaises with practitioners on the exploitation of Earth observation processing services to support hazard mapping and risk assessment. This is in the spirit of the International Forum on Satellite Earth Observation and Geohazards.

BRGM experts have generated displacement maps using Copernicus Sentinel-2 acquisitions from 17 September and 2 October.

Displacement map

Thematic experts from the Corinth Rift Laboratory in Greece have generated similar results using the Cloud processing platform GEP, which has been designed to rapidly provide automated measurements.

As shown in the images, the earthquake triggered deformations of several metres and a tsunami. Around 1400 people are reported to have lost their lives, hundreds have been hospitalized and many more thousands are thought to have been displaced. It has been estimated that up to 1.5 million people will be affected by these events.

The Vice-President of the country, Jusuf Kalla, has said that the final death toll could reach the thousands. The International Charter Space and Major Disasters was triggered by the Asian Disaster Reduction Centre on 29 September for this event. International collaboration is in place to organise Earth observation-based disaster response activities.

Displacement data

Scientific products such as the map created by BRGM are helping us to better understand hazards. Beyond this example it is foreseen that Earth observation data will also be useful for supporting recovery, rehabilitation and reconstruction activities in Indonesia.

Related links:

Sentinel-2: http://www.esa.int/Our_Activities/Observing_the_Earth/Copernicus/Sentinel-2

Sentinel data access: https://scihub.copernicus.eu/

International Charter: https://disasterscharter.org/

Disasters charter Indonesia earthquake activation: https://disasterscharter.org/web/guest/activations/-/article/earthquake-in-indonesia-activation-587-?DanaTimeoutCtx=600001

Geohazards: https://geohazards-tep.eo.esa.int/

Satellite Earth Observation for Geohazard Risk Management: http://esamultimedia.esa.int/docs/EarthObservation/Geohazards/esa-geo-hzrd-2012.pdf

Animation, Images, Text, Credits: ESA/contains modified Copernicus Sentinel data (2018), processed by ESA, CC BY-SA 3.0 IGO/processed by the Corinth Rift Laboratory/processed by the French Geological Survey (BRGM).

Greetings, Orbiter.ch

ICESat-2 Laser Fires for 1st Time, Measures Antarctic Height

NASA - ICESat-2 Mission patch.

Oct. 5, 2018

The laser instrument that launched into orbit last month aboard NASA’s Ice, Cloud and land Elevation Satellite-2 (ICESat-2) fired for the first time Sept. 30. With each of its 10,000 pulses per second, the instrument is sending 300 trillion green photons of light to the ground and measuring the travel time of the few that return: the method behind ICESat-2’s mission to monitor Earth’s changing ice. By the morning of Oct. 3, the satellite returned its first height measurements across the Antarctic ice sheet.

“We were all waiting with bated breath for the lasers to turn on and to see those first photons return,” said Donya Douglas-Bradshaw, the project manager for ICESat-2’s sole instrument, called the Advanced Topographic Laser Altimeter System, or ATLAS. “Seeing everything work together in concert is incredibly exciting. There are a lot of moving parts and this is the demonstration that it’s all working together.”

ICESat-2 launched on Sept. 15 to precisely measure heights and how they change over time. It does this by timing how long it takes individual photons to leave the satellite, reflect off the surface, and return to receiver telescope on the satellite. The ATLAS instrument can time photons with a precision of less than a billionth of a second, which allows the mission to detect small changes in the planet’s ice sheets, glaciers and sea ice.

Photon Jump

Video above: Pho, a plucky bright green photon of light, must travel from a NASA spacecraft down to Earth and back again to help complete a crucial science mission in this educational short film. The animation was created and produced by media art students from the Savannah College of Art in Design in Georgia, in collaboration with ICESat-2. Video Credits: NASA/Goddard/Savannah College of Art and Design et al.

Once ICESat-2 was in space, the ATLAS team waited to turn on the lasers for about two weeks to allow any Earthly contaminants or gases to dissipate.

“It’s very critical when you fire the lasers that you don’t have contaminants because you could damage the optics,” Douglas-Bradshaw said. “Fourteen days is well beyond the time needed for that, but we wanted to be safe.”

During those two weeks, the ICESat-2 operations team turned on and tested the various systems and subsystems of the spacecraft and instrument, and fired thrusters to start placing the satellite in its final polar orbit, approximately 310 miles (500 kilometers) above Earth.

Image above: Illustration of ICESat-2. Image Credits: NASA's Goddard Space Flight Center.

Before the laser was even turned on, however, the team eagerly awaited another milestone, Douglas-Bradshaw said. The door that protected the telescope and detector elements during launch had to be opened. The team had two chances to release one of two spring-loaded pins to open the door. This was successfully accomplished on Sept. 29.

The following day, it was the laser’s turn. The engineering team had been working with the operations team that controls the instrument on orbit, so the commands were ready to go — first turning on the laser itself, waiting for it to warm up, and then issuing commands to put it in fire mode.

The laser energy levels jumped up, and the device that starts ATLAS’s sophisticated stopwatch was active — two different, independent indicators that the laser was firing away.

“We were all incredibly excited and happy, everyone was taking pictures of the screens showing data plots,” Douglas-Bradshaw said. “Someone noted: ‘Now we have a mission, now we have an instrument.”

Three days later, the ICESat-2 team had the first segment of height data, taken as the satellite flew over Antarctica.

Image above: A visualization of ICESat-2 data, called a photon cloud, shows the first set of height measurements from the satellite, taken as it orbited over the Antarctic ice sheet. Each blue dot represents a photon detected by the ATLAS instrument. This photon cloud shows the elevation measured by photons in the middle of the ice sheet, following along 6.2 miles (10 kilometers) of the satellite’s ground track, from left to right. The speckled dots are background photons from sunlight, but the thick blue line is actually a concentration of dots that represent laser photons that returned to the ICESat-2 satellite. Image Credits: NASA's Goddard Space Flight Center.

Computer programmers were up all night analyzing the latitude, longitude and elevation represented by each photon that returned to the ATLAS instrument — and by 6 a.m., Tom Neumann, ICESat-2 deputy project scientist, was texting screenshots of the height data to the rest of the team.

“It was awesome,” Neumann said. “Having it in space, and not just simulating data on the ground, is amazing. This is real light that went from ATLAS to Earth and back again.”

When scientists analyze the preliminary ICESat-2 data, they examine what is called a “photon cloud,” or a plot of each photon that ATLAS detects. Many of the points on a photon cloud are from background photons — natural sunlight reflected off Earth in the exact same wavelength as the laser photons. But with the help of computer programs that analyze the data, scientists can extract the signal from the noise and identify height of the ground below.

The first photon cloud generated by ICESat-2 shows a stretch of elevation measurements from East Antarctica, passing close to the South Pole at a latitude of 88 degrees south, then continuing between Thwaites Glacier and Pine Island Glacier in West Antarctica.

NASA - Laser Focus: The Receiver

Video above: Opto-Mechanical Engineer Tyler Evans explains how the photons that bounce back from Earth are received and filtered by the ATLAS telescope. ATLAS is the primary instrument on board the ICESat-2 spacecraft, which measures the height of Earth's features. Video Credits: NASA's Goddard Space Flight Center.

Next up for ICESat-2 is a suite of procedures to optimize the instrument, Neumann said, including tests to ensure the laser is pointing at the precisely correct angle and lasing at the precisely correct wavelength to allow as many photons as possible to hit the detector.

“It will take a couple of additional weeks,” he said, “but about one month after launch we’ll hopefully start getting back some excellent science-quality data.”

ICESat-2 launched from Vandenberg Air Force Base on the final United Launch Alliance Delta II rocket. The spacecraft was built by Northrop Grumman, which also controls the observatory from their Mission Operations Center in Dulles, Virginia.

For more information on ICESat-2, visit:

    http://icesat-2.gsfc.nasa.gov
    http://www.nasa.gov/icesat-2

Images (mentioned), Videos (mentioned), Text, Credits: NASA/Rob Garner/Goddard Space Flight Center, by Kate Ramsayer.

Greetings, Orbiter.ch

Tracing the Universe: X-ray survey supports standard cosmological model

ESA - XMM-Newton Mission patch.

05 October 2018

Scanning the sky for X-ray sources, ESA's XMM-Newton X-ray observatory has been busy with the XXL Survey, its largest observational programme to date. The second batch of data from the survey has just been released, including information on 365 galaxy clusters, which trace the large-scale structure of the Universe and its evolution through time, and on 26 000 active galactic nuclei (AGN).

Image above: The 365 galaxy clusters of the XXL Survey – X-ray view. Image Credits: ESA/XMM-Newton/XXL Survey.

By examining two large regions of the sky at great sensitivity, this is the first X-ray survey to detect enough galaxy clusters and AGN in contiguous volumes of space to make it possible for scientists to map the distribution of these objects out to the distant Universe in unprecedented detail. The results are compatible with expectations from the currently-accepted cosmological model.

X-rays are produced in some of the most energetic processes in the Universe, but because they are blocked by Earth's atmosphere, they can only be observed from space. When X-ray telescopes observe the extragalactic Universe, they basically see two sources: the hot gas pervading clusters of galaxies, and Active Galactic Nuclei (AGN) – bright, compact regions at the centres of some galaxies where a supermassive black hole is accreting the surrounding matter.

ESA's XMM-Newton is one of the most powerful X-ray telescopes ever placed in orbit. Over the last eight years, it has spent 2000 hours measuring X-ray radiation as part of the XXL Survey, which searched for galaxy clusters and AGN by scanning two areas of seemingly-empty sky each measuring 25 square degrees (as a reference, the full moon measures about half a degree across).

The first set of XXL data was released in 2015; it included 100 of the brightest galaxy clusters and 1000 AGN. This month, a new data catalogue was published containing an astonishing 365 clusters and 26 000 AGN. The first results using this data are published in a special issue of Astronomy & Astrophysics: https://www.aanda.org/component/toc/?task=topic&id=927

The survey mapped X-ray clusters so distant that the light left them when the Universe was just half of its present age, and AGN that are even further away. Some of the observed sources are so far-flung that XMM-Newton received no more than 50 X-ray photons from them, making it challenging to tell whether they are clusters or AGN.

Image above: Multi-wavelength view of galaxy cluster XLSSC006. Image Credits: ESA/XMM-Newton (X-rays); CFHT (optical); XXL Survey.

"It was relatively easy to find galaxy clusters and AGN, because they are the only extragalactic objects visible in X-ray light," explains Marguerite Pierre from CEA Saclay, France.

"But we had to use several other telescopes collecting light at many different wavelengths, as well as extensive computing facilities, to gather more information about each source, including pinning down their nature and distance."

Matter in the Universe is not evenly distributed but forms a cosmic web of filaments shaped by gravity, with galaxy clusters found at their intersections. Galaxy clusters are the largest bound entities in the Universe – they trace the highest density peaks in its large-scale structure, making them a powerful tool for answering questions about cosmology.

The structure and evolution of the Universe is described by a set of cosmological parameters, which include the density of its various components and the rate that it is expanding. Currently, we know the value of many of these parameters fairly well, but large samples of cosmic tracers at a variety of distances are required to more accurately describe the underlying structure of the Universe. The ultimate goal of the XXL Survey is to provide an extensive, well-characterised catalogue of clusters that can be used to constrain the cosmological parameters.

ESA's Planck satellite determined values for cosmological parameters by studying the cosmic microwave background, which is information from the very early Universe. After estimating these parameters using the latest data from the XXL Survey – which is based on information from the more recent Universe – scientists compared their findings against the Planck values.

XMM-Newton. Image Credit: ESA

"Although we didn't find as many galaxy clusters as predicted by the Planck cosmological model, we obtained a distribution of clusters and AGN that is compatible with the currently favoured cosmological model, which resorts to Einstein's cosmological constant as an explanation for the accelerated expansion of the Universe, rather than invoking even more exotic possibilities," explains Marguerite Pierre.

"We can already improve on the Planck estimate for the cosmological constant, even though our analysis has only been carried out on half of the XXL cluster sample; we will spend the next couple of years analysing the rest of the data with the aim of refining the cosmological constraints."

It is more difficult to estimate values for the cosmological parameters using AGN, as their properties are affected by many external influences. Scientists have instead been using the AGN data from the XXL Survey to understand more about how black holes form and evolve.

Thanks to XXL, this is the first time that scientists have been able to measure the three-dimensional clustering effect of distant X-ray clusters and AGN on very large scales. They can now finally see where the AGN are located within the large-scale structure of the Universe indicated by the galaxy clusters.

The results confirm that XMM-Newton is a powerful survey machine. They also pave the way for the final cosmological analysis of this survey, which will provide independent constraints on the cosmological parameters to unravel more mysteries of the Universe.

Image above: The 365 galaxy clusters of the XXL Survey – Optical view. Image Credits: CFHT Legacy Survey/CTIO/XXL Survey.

The cosmic web will be probed further by ESA's future Euclid satellite, which will observe light emitted up to 10 billion years ago. Euclid will see a huge number of sources, as it will detect optical and infrared light; with its large surveyed area and rich multi-wavelength coverage, the XXL data will serve as a reference for these observations.

Observations by XMM-Newton have also raised new questions about the physics of galaxy clusters, which will be investigated in greater detail by ESA's next X-ray mission, Athena. Due to launch in 2031, Athena will be far more sensitive than its predecessor. While XMM-Newton can observe clusters at a variety of distances from us, probing different epochs in the Universe's history, Athena will observe clusters so distant that their light left them as they were forming, telling us even more about the way these gigantic structures take shape and evolve.

In the meantime, scientists in the XXL collaboration plan to process the remaining observations and review data using improved processing techniques. The final XXL data release containing even more X-ray sources, as well as the complete cosmological analysis, is foreseen for 2021.

"It is very exciting that data from this space telescope is contributing to our understanding of the evolution of the Universe," concludes Norbert Schartel, XMM-Newton Project Scientist at ESA. "This was made possible thanks to the collaboration between a huge number of institutions across many different countries."

Notes for Editors:

The results are presented in a series of 20 papers by the XXL Survey collaboration, published in a special issue of Astronomy & Astrophysics: https://www.aanda.org/component/toc/?task=topic&id=927

The European Space Agency's X-ray Multi-Mirror Mission, XMM-Newton, was launched in December 1999. The largest scientific satellite to have been built in Europe, it is also one of the most sensitive X-ray observatories ever flown. More than 170 wafer-thin, cylindrical mirrors direct incoming radiation into three high-throughput X-ray telescopes. XMM-Newton's orbit takes it almost a third of the way to the Moon, allowing for long, uninterrupted views of celestial objects.

XXL is an international project based around an XMM Very Large Programme surveying two 25 square degree extragalactic fields at a depth of about 5 × 10^-15 erg cm^-2 s^-1 in the 0.5-2 keV band for point-like sources. Multi-band information and spectroscopic follow-up of the X-ray sources are obtained through a number of survey programmes.

Besides XMM-Newton, the study is based on data from the following telescopes and astronomical facilities: the European Southern Observatory (ESO) in Chile; the Canada-France-Hawaii Telescope in Hawaii, USA; the William Herschel Telescope on La Palma, Canary Islands, Spain; the Anglo-Australian Telescope at the Siding Spring Observatory, Australia; the Blanco telescope at the Cerro Tololo Inter-American Observatory in Chile; the Giant Metrewave Radio Telescope near Pune, India; the Australia Telescope Compact Array at the Paul Wild Observatory, Australia; and NASA's Spitzer Space Telescope.

The study also relies on extensive calculations performed at the computing centres of IN2P3/CNRS, France, of the University of Geneva, Switzerland, of the Laboratoire d'Astrophysique de Marseille, France, and of the INAF-IASF in Milan, Italy.

Related links:

ESA's Planck satellite: http://sci.esa.int/planck

ESA's future Euclid satellite: http://sci.esa.int/euclid

ESA's next X-ray mission, Athena: http://sci.esa.int/athena

ESA's XMM-Newton: http://sci.esa.int/xmm-newton/

Images (mentioned), Text, Credit: ESA.

Best regards, Orbiter.ch

Groundbreaking Science Emerges from Ultra-Close Orbits of Saturn

NASA - Cassini Mission to Saturn patch.

Oct. 4, 2018

New research emerging from the final orbits of NASA's Cassini spacecraft represents a huge leap forward in our understanding of the Saturn system -- especially the mysterious, never-before-explored region between the planet and its rings. Some preconceived ideas are turning out to be wrong while new questions are being raised.

Image Above: Illustration: NASA's Cassini spacecraft in orbit around Saturn. Image Credits: NASA/JPL-Caltech.

Six teams of researchers are publishing their work Oct. 5 in the journal Science, based on findings from Cassini's Grand Finale. That's when, as the spacecraft was running out of fuel, the mission team steered Cassini spectacularly close to Saturn in 22 orbits before deliberately vaporizing it in a final plunge into the atmosphere in September 2017.

Knowing Cassini's days were numbered, its mission team went for gold. The spacecraft flew where it was never designed to fly. For the first time, it probed Saturn's magnetized environment, flew through icy, rocky ring particles and sniffed the atmosphere in the 1,200-mile-wide (2,000-kilometer-wide) gap between the rings and the cloud tops. Not only did the flight path push the spacecraft to its limits, the new findings illustrate how powerful and agile the instruments were.

Image above: Illustration: NASA's Cassini spacecraft dives between Saturn and its innermost rings, as part of the mission's Grand Finale. Image Credits: NASA/JPL-Caltech.

Many more Grand Finale science results are to come, but here are some of today's highlights:

- Complex organic compounds embedded in water nanograins rain down from Saturn's rings into its upper atmosphere. Scientists saw water and silicates, but they were surprised to see also methane, ammonia, carbon monoxide, nitrogen and carbon dioxide. The composition of the organics is different from that found on moon Enceladus -- and also different from that on moon Titan, meaning there are at least three distinct reservoirs of organic molecules in the Saturn system.

- For the first time, Cassini saw up close how rings interact with the planet and observed inner-ring particles and gases falling directly into the atmosphere. Some particles take on electric charges and spiral along magnetic-field lines, falling into Saturn at higher latitudes -- a phenomenon known as "ring rain." But scientists were surprised to see that others are dragged quickly into Saturn at the equator. And it's all falling out of the rings faster than scientists thought -- as much as 22,000 pounds (10,000 kilograms) of material per second.

- Scientists were surprised to see what the material looks like in the gap between the rings and Saturn's atmosphere. They knew that the particles throughout the rings ranged from large to small. But the sampling in the gap showed mostly tiny, nanometer-sized particles, like smoke, suggesting that some yet-unknown process is grinding up particles.

- Saturn and its rings are even more interconnected than scientists thought. Cassini revealed a previously unknown electric-current system that connects the rings to the top of Saturn's atmosphere.

- Scientists discovered a new radiation belt around Saturn, close to the planet and composed of energetic particles. They found that while the belt actually intersects with the innermost ring, the ring is so tenuous that it doesn’t block the belt from forming.

- Unlike every other planet with a magnetic field in our Solar System, Saturn's magnetic field is almost completely aligned with its spin axis. The new data shows a magnetic-field tilt of less than 0.0095 degrees. (Earth's magnetic field is tilted 11 degrees from its spin axis.) According to everything scientists know about how planetary magnetic fields are generated, Saturn should not have one. It's a mystery that physicists will be working to solve.

- Cassini flew above Saturn's magnetic poles, directly sampling regions where radio emissions are generated. The findings more than doubled the number of direct measurements of radio sources from the planet, one of the few non-terrestrial locations where scientists have been able to study a radio-generation mechanism that is believed to operate throughout the universe.

For the Cassini mission, the science rolling out from Grand Finale orbits more than justifies the calculated risk of diving into the gap -- skimming the upper atmosphere and skirting the edge of the inner rings, said Cassini Project Scientist Linda Spilker.

"Almost everything going on in that region turned out to be a surprise," Spilker said. "That was the importance of going there, to explore a place we'd never been before. And the expedition really paid off -- the data is tremendously exciting."

Analysis of Cassini data from the spacecraft's instruments will be ongoing for years to come, helping to paint a clearer picture of Saturn.

Image above: A few of the findings from Cassini's direct sampling: complex organics rain down from Saturn's rings; inner-ring particles take on electric charges and travel along magnetic-field lines; newly revealed electric-current system and radiation belt; and up-close measurement of Saturn's near-zero magnetic-field tilt. Image Credits: NASA/JPL-Caltech.

"Many mysteries remain, as we put together pieces of the puzzle," Spilker said. "Results from Cassini's final orbits turned out to be more interesting than we could have imagined." 

The papers published in Science are:

- "Chemical interactions between Saturn's atmosphere and its rings," by J.Hunter Waite, et.al.: http://science.sciencemag.org/cgi/doi/10.1126/science.aat2382

- "D-Ring dust falling into Saturn's equatorial ionosphere and upper atmosphere," by Donald Mitchell, et.al.: http://science.sciencemag.org/cgi/doi/10.1126/science.aat2236

- "In-situ collection of dust grains falling from Saturn's rings into its atmosphere," by Hsiang-Wen Hsu, et.al.: http://science.sciencemag.org/cgi/doi/10.1126/science.aat3185

- "A radiation belt of energetic protons located between Saturn and its rings," by Elias Roussos, Peter Kollmann, et.al.: http://science.sciencemag.org/cgi/doi/10.1126/science.aat1962

- "Saturn's magnetic field revealed by the Cassini Grand Finale," by Michele Dougherty, et.al.: http://science.sciencemag.org/cgi/doi/10.1126/science.aat5434

- "The low frequency source of Saturn's Kilometric Radiation (SKR)," by Laurent Lamy, et.al.: http://science.sciencemag.org/cgi/doi/10.1126/science.aat2027

On Oct. 4, as the Science publication embargo lifts, articles describing research complementary to these findings will post online in Geophysical Research Letters (GRL), a journal of the American Geophysical Union (AGU).

Image above: This illustration imagines the view from NASA's Cassini spacecraft during one of its final dives between Saturn and its innermost rings, as part of the mission's Grand Finale. Image Credits: NASA/JPL-Caltech.

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 in Washington. JPL designed, developed and assembled the Cassini orbiter. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the U.S. and several European countries.

For more information about Cassini, go to: https://www.nasa.gov/cassini and https://saturn.jpl.nasa.gov

Cassini instruments: https://saturn.jpl.nasa.gov/mission/spacecraft/cassini-orbiter/orbiterinstruments/

Geophysical Research Letters (GRL): https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)1944-8007.CASSINI_FINALE1

Images (mentioned), Text, Credits: NASA/Dwayne Brown/JoAnna Wendel/Tony Greicius/JPL/Gretchen McCartney.

Greetings, Orbiter.ch

Dive Into a 360-View of Hurricane Maria

NASA & JAXA - GPM Mission patch.

Oct. 4, 2018

Two days before Hurricane Maria devastated Puerto Rico, the NASA/JAXA Global Precipitation Measurement Core Observatory satellite captured a 3D view of the 2017 storm. At the time Maria was a category 1 hurricane. The 3-D view reveals the processes inside the hurricane that would fuel the storm’s intensification to a category 5 storm within 24 hours.

Dive Into a 360-View of Hurricane Maria. Animation Credit: NASA

For the first time in 360 degrees, this data visualization takes you inside the hurricane. The precipitation satellite has an advanced radar that measures both liquid and frozen water. The brightly colored dots show areas of rainfall, where green and yellow show low rates and red and purple show high rates. At the top of the hurricane, where temperatures are colder, blue and purple dots show light and heavy frozen precipitation. The colored areas below the dots show how much rain is falling at the surface.

Inside Hurricane Maria in 360°

Video above: For the first time in 360 degrees, this data visualization takes you inside Hurricane Maria. Video Credits: NASA's Goddard Space Flight Center.

As the visualization progresses, the dots transform into numbers, which are the observed millimeters of precipitation that fall in an hour. The rates in this storm vary from less than 0.5 mm/hr to more than 150 mm/hr. The visualization next transforms these precipitation rates into ellipsoids to show higher (wide, red or purple) or lower (spherical, green or yellow) rainfall rates and snowfall rates (purple to blue colors). In addition to rain and snowfall rates, the satellite can also measure the sizes of tiny precipitation particles and how they are distributed throughout the storm. Toward the end of the visualization, big drops are depicted in dark blue and small drops in light blue and white.

Image above: Visualization of the GPM Core Observatory and Partner Satellites. Image Credits: NASA/JAXA.

Looking at drop sizes and rainfall rates provides a key part of the equation in understanding hurricane intensity. Factors such as temperature, humidity, wind speed and clouds influence the size of precipitation particles, which in turn affects how much rain falls and how a storm grows. These advanced satellite measurements are critical for improving forecasts of how these powerful storms may intensify and where they may go.

Related links:

GPM (Global Precipitation Measurement): http://www.nasa.gov/mission_pages/GPM/main/index.html

Hurricanes: http://www.nasa.gov/mission_pages/hurricanes/main/index.html

Image (mentioned), Animation (mentioned), Video (mentioned), Text, Credits: NASA/Karl Hille/Earth Science News Team, by Ellen Gray.

Greetings, Orbiter.ch

Curiosity Rover to Temporarily Switch 'Brains'

NASA - Mars Science Laboratory (MSL) patch.

Oct. 4, 2018

Image above: A self-portrait of NASA's Curiosity rover taken on Sol 2082 (June 15, 2018). A Martian dust storm has reduced sunlight and visibility at the rover's location in Gale Crater. Image Credits: NASA/JPL-Caltech.

Engineers at NASA's Jet Propulsion Laboratory in Pasadena, California, this week commanded the agency's Curiosity rover to switch to its second computer. The switch will enable engineers to do a detailed diagnosis of a technical issue that has prevented the rover's active computer from storing science and some key engineering data since Sept. 15.

Like many NASA spacecraft, Curiosity was designed with two, redundant computers -- in this case, referred to as a Side-A and a Side-B computer -- so that it can continue operations if one experiences a glitch. After reviewing several options, JPL engineers recommended that the rover switch from Side B to Side A, the computer the rover used initially after landing.

The rover continues to send limited engineering data stored in short-term memory when it connects to a relay orbiter. It is otherwise healthy and receiving commands. But whatever is preventing Curiosity from storing science data in long-term memory is also preventing the storage of the rover's event records, a journal of all its actions that engineers need in order to make a diagnosis. The computer swap will allow data and event records to be stored on the Side-A computer.

Side A experienced hardware and software issues over five years ago on sol 200 of the mission, leaving the rover uncommandable and running down its battery. At that time, the team successfully switched to Side B. Engineers have since diagnosed and quarantined the part of Side A's memory that was affected so that computer is again available to support the mission.

"At this point, we're confident we'll be getting back to full operations, but it's too early to say how soon," said Steven Lee of JPL, Curiosity's deputy project manager. "We are operating on Side A starting today, but it could take us time to fully understand the root cause of the issue and devise workarounds for the memory on Side B.

"We spent the last week checking out Side A and preparing it for the swap," Lee said. "It's certainly possible to run the mission on the Side-A computer if we really need to. But our plan is to switch back to Side B as soon as we can fix the problem to utilize its larger memory size."

For more about Curiosity, visit: https://mars.nasa.gov/msl/

For more about NASA's Mars program, visit: https://mars.nasa.gov

Image (mentioned), Text, Credits: NASA/Tony Greicius/JPL/Andrew Good.

Greetings, Orbiter.ch

Green smoothies in space

ISS - International Space Station logo.

4 October 2018

The Artemiss experiment that ran on the International Space Station has shown that ESA can cultivate oxygen from plants in space. It is paving the way for more demonstrations of regenerative life-support technology, and astronauts get a green smoothie to boot.

Microalgae batch

Check, check, and check

Microalgae Arthrospira, commonly known as spirulina were launched to the Space Station in December 2017 where they recycled carbon dioxide into oxygen to produce edible proteins.

A liquid sample of spirulina was loaded into a photobioreactor, a cylinder bathed in light. Over the course of a month the microorganism converted the light into energy, producing oxygen as a by-product at the same speed as it would on Earth. Researchers now confirm that the biological process on Earth works the same in space.

Unloading a batch

Four photobioreactors ran in parallel while the oxygen and biomass produced by the spirulina was recorded. Extracting oxygen from the liquid posed a challenge, as liquids and gases do not naturally separate in weightlessness, but the novel bioreactor technology behind Artemiss performed well with accurate measurements.

The beauty of the Arthrospira microorganism is that it is edible if pure. Thanks to highly accurate computer models and subsequent experiment design, all the samples returned pure. The green smoothie-like product was safe to add to astronaut diets as a source of protein.

Round two

On its first round on the Space Station, researchers tested a batch of the microalgae, the next step is to run the experiment with a continuous supply of spirulina for three months.

The project is part of the Micro-Ecological Life Support System Alternative – Melissa –programme that is developing regenerative technologies for life support.

Employing a closed-loop concept, Melissa aims to recover food, water, and oxygen from organic waste such as carbon dioxide and minerals.

The programme covers many research, education, and technological activities such as the AstroPlant citizen science project that is collecting data on how plants grow in different environments.

The 5 compartments of the MELiSSA loop

Using a different approach, ESA’s Advanced Close Loop System arrived at the International Space Station last week and promises to recycle carbon dioxide into water.

Soon to join this Artemiss experiment is another technology precursor called Urinis that will look into recycling urine to provide nitrogen gas, plant nutrients, and water on the Space Station.

A decade of European science in space

In the meantime, future astronauts can count on getting their green smoothie in space too.

Related links:

AstroPlant: http://www.esa.int/Our_Activities/Human_Spaceflight/AstroPlant_citizen_science_for_growing_plants_in_space

ESA’s Advanced Close Loop System arrived at the International Space Station: http://www.esa.int/Our_Activities/Human_Spaceflight/International_Space_Station/Next-generation_life-support_system_heading_to_Space_Station

European space laboratory Columbus: http://www.esa.int/Our_Activities/Human_Spaceflight/Columbus

Experiment archive: http://eea.spaceflight.esa.int/

International Space Station Benefits for Humanity: http://www.esa.int/Our_Activities/Human_Spaceflight/International_Space_Station_Benefits_for_Humanity

Images, Text, Credits: ESA/NASA.

Greetings, Orbiter.ch

Expedition 56 Trio Undocks from ISS and landed safely on Earth

ROSCOSMOS - Soyuz MS-08 Mission patch.

October 4, 2018

Expedition 56 Commander Drew Feustel and Flight Engineer Ricky Arnold of NASA, along with Flight Engineer and Soyuz Commander Oleg Artemyev of the Russian space agency Roscosmos undocked from the International Space Station at 3:57 a.m. EDT to begin their trip home.

Image above: The Soyuz MS-08 spacecraft that is returning three Expedition 56 crew members back to Earth is pictured from a space station camera just before to undocking from the Poisk module. Image Credit: NASA TV.

Deorbit burn is scheduled for approximately 6:51 a.m., with landing in Kazakhstan targeted for 7:45 a.m. (5:45 p.m. Kazakhstan time).

Soyuz MS-08 undocking and departure

At the time of undocking, Expedition 57 will begin formally aboard the station, with Commander Alexander Gerst of ESA (European Space Agency), NASA’s Serena Aunon-Chancellor and Roscosmos cosmonaut Sergey Prokopyev comprising a three-person crew for one week.

Station Crew Back on Earth After 197 Days in Space

Three crew members who have been living and working aboard the International Space Station have landed safely in Kazakhstan.

Expedition 56 Commander Drew Feustel and Flight Engineer Ricky Arnold of NASA, along with Flight Engineer and Soyuz Commander Oleg Artemyev of the Russian space agency Roscosmos landed at 7:44 a.m. EDT (5:44 p.m. in Kazakhstan) southeast of the remote town of Dzhezkazgan in Kazakhstan.

Image above: The Soyuz MS-08 spacecraft that is carrying Expedition 55/56 crew members Ricky Arnold, Drew Feustel and Oleg Artemyev is pictured seconds away from landing under a parachute in Kazakhstan. Image Credit: NASA TV.

The crew completed hundreds of experiments during its 197-day expedition. Highlights included an investigation to study ultra-cold quantum gases using the first commercial European facility for microgravity research, and a system that uses surface forces to accomplish liquid-liquid separation.

The crew also welcomed five cargo spacecraft that delivered several tons of supplies and research experiments. The 14th SpaceX Dragon arrived in April, shortly after the three crew members did, bringing supplies and equipment, and the 15th Dragon arrived in July. The ninth Northrop Grumman Cygnus resupply spacecraft arrived in May before the end of Expedition 55. A Russian Progress completed a record rapid rendezvous of less than four hours in August. And, the seventh Japanese Konotouri cargo craft arrived just a week before the Expedition 56 trio departed for home.

Both Feustel and Arnold participated in dozens of educational events while in space as part of NASA’s Year of Education on Station, reaching more than 200,000 students in 29 states. Feustel now has logged more than 226 days in space on three spaceflights, and Arnold more than 209 days on two missions.

Soyuz MS-08 landing

The duo ventured outside the space station on three spacewalks to effect maintenance and upgrades during Expeditions 55 and 56. Their work included replacing and upgrading external cameras, including those that will facilitate the approach and docking of the Boeing Starliner and SpaceX Crew Dragon commercial crew spacecraft when they begin launching soon from American soil. The spacewalkers also replaced components of the space station’s cooling system and communications network, and installed new wireless communication antennas for external experiments. Feustel has accumulated 61 hours and 48 minutes over nine career spacewalks, and ranks third overall among American astronauts. Arnold has 32 hours and 4 minutes over five career spacewalks.

Artemyev conducted one spacewalk with fellow cosmonaut Sergey Prokopyev to manually launch four small technology satellites and install an experiment called Icarus onto the Russian segment of the space station. The spacewalk timed out at 7 hours and 46 minutes, the longest in Russian space program history. Artemyev now has spent 366 days in space on his two flights.

Expedition 57 continues station research and operations with a crew comprised of Serena Auñón-Chancellor of NASA, Alexander Gerst of ESA (European Space Agency) and Sergey Prokopyev of Roscosmos. Gerst assumed command of the station as Feustel prepared to depart.

NASA astronaut Nick Hague and Roscosmos cosmonaut Alexey Ovchinin are scheduled to launch Oct. 11 for a same-day arrival, increasing the crew size to five.

Related article:

Dragon delivers some ICE:
https://orbiterchspacenews.blogspot.com/2018/06/dragon-delivers-some-ice.html

Related links:

Expedition 57: https://www.nasa.gov/mission_pages/station/expeditions/expedition56/index.html

NASA’s Year of Education on Station: https://www.nasa.gov/audience/foreducators/stem-on-station/year-of-education.html

Icarus: https://directory.eoportal.org/web/eoportal/satellite-missions/i/iss-icarus

Ultra-cold quantum gases: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=7396

Commercial European facility: http://www.esa.int/Our_Activities/Human_Spaceflight/Research/Ice_Cubes_cool_new_commercial_opportunity_on_the_International_Space_Station

Liquid-liquid separation: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=7696

Commercial crew: http://www.nasa.gov/commercialcrew

Spacewalks: https://www.nasa.gov/mission_pages/station/spacewalks

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Videos, Text, Credits: NASA/Mark Garcia/NASA TV/SciNews.

Best regards, Orbiter.ch

U.S., German Astronauts Swapping Command Before Homecoming

ISS - Expedition 56 Mission patch.

October 3, 2018

A NASA astronaut will swap command of the International Space Station with a European Space Agency (ESA) astronaut Wednesday at 10:10 a.m. live on NASA TV. Expedition 56 Commander Drew Feustel will be handing the station “keys” over to German astronaut Alexander Gerst during the traditional change of command ceremony.

Image above: Expedition 56 Commander Drew Feustel (left) of NASA will hand over command of the station to German astronaut Alexander Gerst of ESA. Image Credit: NASA.

Expedition 57 officially starts Thursday at 3:57 a.m. EDT when Feustel and Flight Engineer Ricky Arnold undock in the Soyuz MS-08 spacecraft commanded by cosmonaut Oleg Artemyev. Gerst, ESA’s second astronaut to command the station, is remaining onboard to lead Expedition 57 Flight Engineers Serena Auñón-Chancellor and Sergey Prokopyev. The homebound trio will parachute to a landing in Kazakhstan at 7:45 a.m. (5:45 p.m. Kazakhstan time) just two orbits after undocking and 197 days in space.

Astronaut Nick Hague from NASA’s astronaut class of 2014 and veteran station cosmonaut Alexey Ovchinin will be the next crew to blast off to the space station. The duo will launch Oct. 11 from the Baikonur Cosmodrome and take a six hour ride to their new home in space.

Image above: The Creativity of Mother Nature. International Space Station Commander Alexander Gerst has a better view of our home planet than most. From aboard the orbital laboratory he sees Earth in all its beauty and said of this image of the west coast of southern Africa: "Not many artists in this world are as creative as Mother Nature." Image Credits: ESA/NASA-A.Gerst.

Amidst the crew departure activities today the station residents also worked space science and lab maintenance. Auñón-Chancellor worked on botany research inside the Plant Habitat located in the Columbus lab module. Gerst worked on hardware for the mobiPV study that is researching ways to increase productivity between astronauts and mission controllers. Departing astronauts Arnold and Feustel cleaned up their crew quarters.

Related links:

Expedition 56: https://www.nasa.gov/mission_pages/station/expeditions/expedition56/index.html

Expedition 57: https://www.nasa.gov/mission_pages/station/expeditions/expedition57/index.html

Plant Habitat: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Facility.html?#id=2036

MobiPV: https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=1818

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), text, Credits: NASA/Yvette Smith/Mark Garcia.

Best regards, Orbiter.ch

Parker Solar Probe Successfully Completes First Venus Flyby

NASA - Parker Solar Probe Mission patch.

October 3, 2018

On Oct. 3, Parker Solar Probe successfully completed its flyby of Venus at a distance of about 1,500 miles during the first Venus gravity assist of the mission. These gravity assists will help the spacecraft tighten its orbit closer and closer to the Sun over the course of the mission.

Image above: The orbit design for the Parker Solar Probe mission. Image Credits: NASA/Johns Hopkins APL.

Detailed data from the flyby will be assessed over the next few days. This data allows the flight operations team to prepare for the remaining six Venus gravity assists which will occur over the course of the seven-year mission.

 Parker Solar Probe- Venus Flyby

Related article:

Illuminating First Light Data from Parker Solar Probe:
https://orbiterchspacenews.blogspot.com/2018/09/illuminating-first-light-data-from.html

Parker Solar Probe: https://www.nasa.gov/parkersolarprobe/

Image (mentioned), Video, Text, Credits: NASA/Sarah Frazier.

Greetings, Orbiter.ch

Hubble finds compelling evidence for a moon outside the Solar System

ESA - Hubble Space Telescope logo.

3 October 2018

Neptune-sized moon orbits Jupiter-sized planet

Exomoon orbiting its planet (artist’s impression)

Using the NASA/ESA Hubble Space Telescope and older data from the Kepler Space Telescope two astronomers have found the first compelling evidence for a moon outside our own Solar System. The data indicate an exomoon the size of Neptune, in a stellar system 8000 light-years from Earth. The new results are presented in the journal Science Advances.

The hunt for exoplanets — planets outside our own Solar System — provided its first results only 30 years ago. While astronomers now find these planets on a regular basis, the search for moons orbiting exoplanets wasn’t successful — until today.

In 2017 NASA’s Kepler Space Telescope detected hints of an exomoon orbiting the planet Kepler-1625b. Now, two scientists from Columbia University in New York (USA) have used the incomparable capabilities of the NASA/ESA Hubble Space Telescope to study the star Kepler-1625, 8000 light-years away, and its planet in more detail. The new observations made with Hubble show compelling evidence for a large exomoon orbiting the only known planet of Kepler-1625. If confirmed, this would be the first discovery of a moon outside our Solar System.

The candidate moon, with the designation Kepler-1625b-i, is unusual because of its large size; it is comparable in diameter to the planet Neptune. Such gargantuan moons are unknown in our own Solar System. “This may yield new insights into the development of planetary systems and may cause astronomers to revisit theories of how moons form,” Alex Teachey, a graduate student who led the study, explained excitedly [1].

Hubble Space Telescope (HST)

Like its moon, Kepler-1625b is also bigger than its counterparts in the Solar System. The exoplanet is a gas giant, several times more massive than Jupiter [2]. It orbits its parent star at a distance similar to the distance between the Sun and Earth, which puts it — and its candidate moon — at the inner edge of the habitable zone of the star system [3].

To find evidence for the existence of the exomoon, the team observed the planet while it was in transit in front of its parent star, causing a dimming of the starlight. “We saw little deviations and wobbles in the light curve that caught our attention,” David Kipping, second author of the study, said.

The planet was observed by Hubble before and during its 19-hour-long transit. After the transit ended, Hubble detected a second and much smaller decrease in the star’s brightness approximately 3.5 hours later, consistent with the effect of a moon trailing the planet. “It was definitely a shocking moment to see that light curve — my heart started beating a little faster and I just kept looking at that signature,” David Kipping described his feelings. Unfortunately, the scheduled Hubble observations ended before the complete transit of the moon could be captured.

Transit of exoplanet and exomoon

In addition to this second dip in the light curve, Hubble provided compelling supporting evidence for the moon hypothesis by detecting the planet’s transit more than an hour earlier than predicted. This is consistent with a model of the system in which the planet and its moon orbit a common centre of gravity, causing the planet to wobble away from its predicted location [4].

In principle this anomaly could also be caused by the gravitational pull of a hypothetical second planet in the system, but the Kepler Space Telescope found no evidence for additional planets around the star during its four year mission. Still, further observations by Hubble are needed to fully confirm the existence of Kepler-1625b-i.

“If confirmed, Kepler-1625b-i will certainly provide an interesting puzzle for theorists to solve,” said Kipping. Teachey concluded: “It is an exciting reminder of how little we really know about distant planetary systems and the great spirit of discovery exoplanetary science embodies.”

Notes:

[1] The moons of Jupiter and Saturn likely formed through the agglomeration into a disc of material orbiting the planets, so it is possible that this exomoon also formed in a circumplanetary disc. Another possibility is that a passing object was captured by the planet’s gravity. Tidal forces between the two objects would rob momentum from the less massive companion and eventually pull it into a permanent orbit. There are no indications of tidal capture among our Solar System’s moons. In the case of the Earth–Moon system, an early collision with a larger body is hypothesised to have blasted off material that later coalesced into a moon. However, Kepler-1625b and its candidate moon are gaseous, not rocky, so such a collision would not have led to the condensation of a satellite.

[2] Despite its size, the mass of the candidate moon is estimated to be only 1.5 percent of the mass of its companion planet. This value is close to the mass ratio between Earth and the Moon.

[3] While both the planet and its candidate moon are within the habitable zone, where moderate temperatures allow for the existence of liquid water, both bodies are considered to be gaseous and therefore unsuitable for life as we know it.

[4] A distant observer watching the Earth and Moon transit the Sun would note similar anomalies in the timing of Earth’s transit.

More information:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The results were presented in the paper Evidence for a large exomoon orbiting Kepler-1625b in the journal Science Advances.

The team of astronomers in this study consists of Alex Teachey and David M. Kipping (Columbia University, New York, USA).

Links:

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

Hubblesite release: http://hubblesite.org/news_release/news/2018-45

Science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1817/heic1817a.pdf

NASA’s Kepler Space Telescope: https://www.nasa.gov/mission_pages/kepler/main/index.html

NASA/ESA Hubble Space Telescope (HST): https://www.spacetelescope.org/

Image, Animation, Text, Credits: NASA, ESA/Video Credits: Credit: ESA/Hubble, L. Calçada.

Greetings, Orbiter.ch