1 of 14

Space News Update — December 11, 2018 —

Contents

In the News

Story 1:

NASA’s Voyager 2 Probe Enters Interstellar Space

Story 2:

NASA’s Newly Arrived OSIRIS-REx Spacecraft Already Discovers Water on Asteroid

Story 3:

Planning the New Horizons Exploration of Ultima Thule by Alan Stern, principal investigator of NASA's New Horizons mission

Departments

The Night Sky

ISS Sighting Opportunities

NASA-TV Highlights

Space Calendar

Food for Thought

Space Image of the Week

2 of 14

1. NASA’s Voyager 2 Probe Enters Interstellar Space

This illustration shows the position of NASA’s Voyager 1 and Voyager 2 probes, outside of the heliosphere, a protective

bubble created by the Sun that extends well past the orbit of Pluto. Credits: NASA/JPL-Caltech

For the second time in history, a human-made object has reached the space between the stars. NASA’s Voyager 2

probe now has exited the heliosphere – the protective bubble of particles and magnetic fields created by the Sun.

Comparing data from different instruments aboard the trailblazing spacecraft, mission scientists determined the

probe crossed the outer edge of the heliosphere on Nov. 5. This boundary, called the heliopause, is where the

tenuous, hot solar wind meets the cold, dense interstellar medium. Its twin, Voyager 1, crossed this boundary in

2012, but Voyager 2 carries a working instrument that will provide first-of-its-kind observations of the nature of this

gateway into interstellar space.

Voyager 2 now is slightly more than 11 billion miles (18 billion kilometers) from Earth. Mission operators still can

communicate with Voyager 2 as it enters this new phase of its journey, but information – moving at the speed of

light – takes about 16.5 hours to travel from the spacecraft to Earth. By comparison, light traveling from the Sun

takes about eight minutes to reach Earth.

The most compelling evidence of Voyager 2’s exit from the heliosphere came from its onboard Plasma Science

Experiment (PLS), an instrument that stopped working on Voyager 1 in 1980, long before that probe crossed the

heliopause. Until recently, the space surrounding Voyager 2 was filled predominantly with plasma flowing out from

our Sun. This outflow, called the solar wind, creates a bubble – the heliosphere – that envelopes the planets in our

solar system. The PLS uses the electrical current of the plasma to detect the speed, density, temperature, pressure

and flux of the solar wind. The PLS aboard Voyager 2 observed a steep decline in the speed of the solar wind

particles on Nov. 5. Since that date, the plasma instrument has observed no solar wind flow in the environment

around Voyager 2, which makes mission scientists confident the probe has left the heliosphere.

In addition to the plasma data, Voyager’s science team members have seen evidence from three other onboard

instruments – the cosmic ray subsystem, the low energy charged particle instrument and the magnetometer – that

is consistent with the conclusion that Voyager 2 has crossed the heliopause. Voyager’s team members are eager to

continue to study the data from these other onboard instruments to get a clearer picture of the environment

through which Voyager 2 is traveling.

3 of 14

“There is still a lot to learn about the region of interstellar space immediately beyond the heliopause,” said Ed

Stone, Voyager project scientist based at Caltech in Pasadena, California.

Together, the two Voyagers provide a detailed glimpse of how our heliosphere interacts with the constant

interstellar wind flowing from beyond. Their observations complement data from NASA’s Interstellar Boundary

Explorer (IBEX), a mission that is remotely sensing that boundary. NASA also is preparing an additional mission –

the upcoming Interstellar Mapping and Acceleration Probe (IMAP), due to launch in 2024 – to capitalize on the

Voyagers’ observations.

“Voyager has a very special place for us in our heliophysics fleet,” said Nicola Fox, director of the Heliophysics

Division at NASA Headquarters. “Our studies start at the Sun and extend out to everything the solar wind touches.

To have the Voyagers sending back information about the edge of the Sun’s influence gives us an unprecedented

glimpse of truly uncharted territory.”

While the probes have left the heliosphere, Voyager 1 and Voyager 2 have not yet left the solar system, and won’t

be leaving anytime soon. The boundary of the solar system is considered to be beyond the outer edge of the Oort

Cloud, a collection of small objects that are still under the influence of the Sun’s gravity. The width of the Oort

Cloud is not known precisely, but it is estimated to begin at about 1,000 astronomical units (AU) from the Sun and

to extend to about 100,000 AU. One AU is the distance from the Sun to Earth. It will take about 300 years for

Voyager 2 to reach the inner edge of the Oort Cloud and possibly 30,000 years to fly beyond it.

The Voyager probes are powered using heat from the decay of radioactive material, contained in a device called a

radioisotope thermal generator (RTG). The power output of the RTGs diminishes by about four watts per year,

which means that various parts of the Voyagers, including the cameras on both spacecraft, have been turned off

over time to manage power.

Source: NASA Return to Contents

The set of graphs on the left illustrates the drop in electrical current detected in three directions by Voyager 2's plasma science experiment (PLS) to background levels. They are among the key

pieces of data that show that Voyager 2 entered interstellar space in November 2018. Credits:

NASA/JPL-Caltech/MIT

4 of 14

2. NASA’s Newly Arrived OSIRIS-REx Spacecraft Already Discovers Water

on Asteroid

This mosaic image of asteroid Bennu is composed of 12 PolyCam images collected on Dec. 2 by the OSIRIS-REx spacecraft from a range of 15 miles (24 km). Credits: NASA/Goddard/University of Arizona

Recently analyzed data from NASA’s Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer (OSIRIS-REx) mission has revealed water locked inside the clays that make up its scientific target, the

asteroid Bennu.

During the mission’s approach phase, between mid-August and early December, the spacecraft traveled 1.4

million miles (2.2 million km) on its journey from Earth to arrive at a location 12 miles (19 km) from Bennu on Dec. 3. During this time, the science team on Earth aimed three of the spacecraft’s instruments towards Bennu and began making the mission’s first scientific observations of the asteroid. OSIRIS-REx is NASA’s first asteroid

sample return mission.

Data obtained from the spacecraft’s two spectrometers, the OSIRIS-REx Visible and Infrared Spectrometer

(OVIRS) and the OSIRIS-REx Thermal Emission Spectrometer (OTES), reveal the presence of molecules that contain oxygen and hydrogen atoms bonded together, known as “hydroxyls.” The team suspects that these hydroxyl groups exist globally across the asteroid in water-bearing clay minerals, meaning that at some point,

Bennu’s rocky material interacted with water. While Bennu itself is too small to have ever hosted liquid water, the finding does indicate that liquid water was present at some time on Bennu’s parent body, a much larger asteroid.

“The presence of hydrated minerals across the asteroid confirms that Bennu, a remnant from early in the formation of the solar system, is an excellent specimen for the OSIRIS-REx mission to study the composition

5 of 14

of primitive volatiles and organics,” said Amy Simon, OVIRS deputy instrument scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “When samples of this material are returned by the mission to

Earth in 2023, scientists will receive a treasure trove of new information about the history and evolution of our solar system.”

Additionally, data obtained from the OSIRIS-REx Camera Suite (OCAMS) corroborate ground-based telescopic observations of Bennu and confirm the original model developed in 2013 by OSIRIS-REx Science Team Chief Michael Nolan and collaborators. That model closely predicted the asteroid’s actual shape, with Bennu’s

diameter, rotation rate, inclination, and overall shape presented almost exactly as projected.

One outlier from the predicted shape model is the size of the large boulder near Bennu’s south pole. The

ground-based shape model calculated this boulder to be at least 33 feet (10 meters) in height. Preliminary calculations from OCAMS observations show that the boulder is closer to 164 feet (50 meters) in height, with a width of approximately 180 feet (55 meters).

Bennu’s surface material is a mix of very rocky, boulder-filled regions and a few relatively smooth regions that lack boulders. However, the quantity of boulders on the surface is higher than expected. The team will make

further observations at closer ranges to more accurately assess where a sample can be taken on Bennu to later be returned to Earth.

“Our initial data show that the team picked the right asteroid as the target of the OSIRIS-REx mission. We

have not discovered any insurmountable issues at Bennu so far,” said Dante Lauretta, OSIRIS-REx principal investigator at the University of Arizona, Tucson. “The spacecraft is healthy and the science instruments are working better than required. It is time now for our adventure to begin.”

The mission currently is performing a preliminary survey of the asteroid, flying the spacecraft in passes over Bennu’s north pole, equator, and south pole at ranges as close as 4.4 miles (7 km) to better determine the

asteroid’s mass. The mission’s scientists and engineers must know the mass of the asteroid in order to design the spacecraft’s insertion into orbit because mass affects the asteroid’s gravitational pull on the spacecraft. Knowing Bennu’s mass will also help the science team understand the asteroid’s structure and composition.

This survey also provides the first opportunity for the OSIRIS-REx Laser Altimeter (OLA), an instrument contributed by the Canadian Space Agency, to make observations, now that the spacecraft is in proximity to

Bennu.

The spacecraft’s first orbital insertion is scheduled for Dec. 31, and OSIRIS-REx will remain in orbit until mid-

February 2019, when it exits to initiate another series of flybys for the next survey phase. During the first orbital phase, the spacecraft will orbit the asteroid at a range of 0.9 miles (1.4 km) to 1.24 miles (2.0 km) from the center of Bennu — setting new records for the smallest body ever orbited by a spacecraft and the

closest orbit of a planetary body by any spacecraft.

Goddard provides overall mission management, systems engineering and the safety and mission assurance for

OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space Systems in Denver built the spacecraft and is providing flight

operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the agency’s New Frontiers Program for the Science Mission Directorate in

Washington.

Source: NASA Return to Contents

6 of 14

3. Planning the New Horizons Exploration of Ultima Thule by Alan Stern, principal investigator of NASA's New Horizons mission

This illustration provides a "big picture" view of New Horizon's trajectory from Earth to the Kuiper belt and beyond.

NASA / JHU-APL / SWRI

As I wrote in this blog last month, NASA’s New Horizons spacecraft is on approach to conduct the first ever,

close exploration of a Kuiper Belt Object (KBO) on January 1, 2019. The time of closest approach will be 5:33

Universal Time (33 minutes past midnight on the U.S. east coast), with a planned closest approach distance of

3,500 kilometers (2,200 miles). Our KBO, 2014 MU69, was discovered in a dedicated Hubble Space Telescope

search for flyby targets that we conducted in 2014. After a naming contest, the mission team gave “MU69” the

nickname “Ultima Thule,” a Latin phrase appropriately meaning “a distant unknown region; the extreme limit

of discovery.”

The primary objectives of the flyby of Ultima are to map its surface features and composition, determine if it

has an atmosphere, and to search for any satellites or rings it might possess. New Horizons, which was

launched in 2006 and which made the first exploration of the Pluto system in 2015, carries seven powerful

scientific instruments to carry out this exploration. All will be used in the exploration of Ultima.

Meet the science instruments

Three of the payload instruments are optical devices. LORRI, the Long Range Reconnaissance Imager, is

comprised of a 20-cm diameter telescope that feeds a panchromatic CCD — a digital imaging device sensitive

to all visible wavelengths — and is the highest resolution imager aboard New Horizons. A second imager

named Ralph contains four CCDs with color filter channels and two CCDs for panchromatic imaging.

Importantly, Ralph also contains an infrared spectrometer that will be used to map the surface composition of

Ultima. The third optical instrument aboard New Horizons is Alice, an ultraviolet mapping spectrometer that

will be used to search for gases emitted from Ultima and determine their density and composition.

7 of 14

The other instruments aboard New Horizons are: SWAP and PEPSSI, both charged-particle spectrometers;

REX, a radio-science instrument that will be used to determine Ultima’s surface temperature and to measure

its radar reflectivity; and SDC, a student-built interplanetary-dust counter.

Planning the encounter

Because Ultima is small — probably just 25 km (16 miles) or so in diameter — it will remain just a point of

light to New Horizons until about 2 days before the close flyby. However, in the final hours around closest

approach, New Horizons will be able to map Ultima at higher resolutions than we achieved at Pluto, because

we will fly by Ultima at a much closer range than we did at Pluto

We will obtain geologic mapping resolutions as high as 35 meters (110 feet) per pixel using LORRI. By

comparison, our highest resolution Pluto mapping was about 80 meters (260 feet) per pixel.

With the Ralph imager, we also plan to acquire color images of Ultima with resolutions as high as 330 meters

(0.2 miles) per pixel, and composition mapping at a resolution of 1.8 km (1.1 miles) per pixel. Stereo imaging

made on approach will map the surface topography of Ultima at about 80 meters (260 feet) per pixel. The first

detailed imagery of Ultima will be downlinked to Earth once the spacecraft has completed its main flyby

objectives late on January 1st, and will be released to the public after processing and image analysis on

January 2nd. More images, as well as spectra and other data sets, will be downlinked on January 2nd, 3rd,

and 4th — so get ready to learn a lot about Ultima in the first week of the new year! Then the spacecraft will

slip behind the Sun as seen from Earth and image transmissions will cease for 5 days until the spacecraft

reappears and can resume data transmissions.

This plan illustrates what the spacecraft will be up to in the days around the flyby. The bottom panel zooms in on the

hours right around closest approach and shows what instruments will be active and when.

NASA / JHU-APL / SWRI

The total data volume collected on the Ultima flyby will be close to 50 gigabits. Because New Horizons is so far

from Earth, about 6 billion km (4 billion miles), its data transmission speed is now only about 1,000 bits per

8 of 14

second. This limitation, and the fact that we share NASA’s Deep Space Network of tracking and communication

antennas with over a dozen other NASA missions, means that it will take 20 months or more, until late in

2020, to send all of the data about Ultima and its environment back to Earth.

Looking ahead

As you read these words, New Horizons is closing in on Ultima at a speed of nearly a million miles per day.

The main tasks onboard the spacecraft now are navigation imaging that drives course corrections to home in

on our aim point, and a three-week-long hazard search to determine if our close approach path is safe, or if

we must divert to a greater distance of 10,000 km (6,000 miles) to avoid hazards such as dust or moons. We

will make a final decision on the close approach distance on December 16th.

The flyby of Ultima will be orchestrated aboard New Horizons with a computer program called “command

sequence” that will be uploaded by radio and will begin 7 days prior to the flyby, on Christmas day. This

command sequence will direct all of the spacecraft and science instrument activities from then until 2 days

after closest approach.

Our science team just completed its final meeting before the flyby. We’ll assemble for science operations

beginning December 28th at our mission control, which is at the Johns Hopkins Applied Physics Laboratory in

Laurel, Maryland. We’ll be reporting results in press conferences and news releases every day from December

30th to January 4th. You can follow New Horizons on NASA TV, and on a variety of social media such as

Facebook and Twitter by just searching for “New Horizons”. Our mission web site is at http://pluto.jhuapl.edu.

I’ll blog here again the week before the flyby with an update on our hazard findings, our final selection of

approach distance, and late-breaking other details. Stay tuned!

This blog is part of a four-part series covering the Ultima Thule flyby. Click on the links below for the other

installments:

Part One: New Horizons on Approach to the First Exploration of a Kuiper Belt Object

Source: Sky and Telescope Return to Contents

9 of 14

The Night Sky

Tuesday, December 11

• Now you'll find Alpha and Beta Capricorni to the right of the Moon at nightfall.

• The Summer Triangle is sinking lower in the west, and Altair is the first of its stars to go (for mid-northern

observers). Start by spotting bright, zero-magnitude Vega in the northwest right after dark. The brightest star

above Vega is Deneb. Altair, the Triangle's third star, is farther to Vega's left or lower left. How late into the night,

and into the advancing season, can you keep Altair in view?

Wednesday, December 12

• The thick crescent Moon forms a roughly equilateral triangle, 20° or more on a side, with Mars to its upper left

and Fomalhaut to its lower left.

Thursday, December 13

• The Mars-Moon-Fomalhaut triangle has narrowed since yesterday as the Moon moves eastward along its orbit.

• The Geminid meteor shower should be at its peak late tonight! In early evening the meteors will be few, but

those that do appear will be Earth-grazers skimming far across the top of the atmosphere. As the hours pass and

the shower's radiant (near Castor in Gemini) rises higher in the east, the meteors will become shorter and more

numerous — the most so from midnight to dawn.

This should be a good year for the Geminids. There’s not too much light from the Moon during the evening, and

then the Moon sets around 10 or 11 p.m., leaving the sky dark for the peak hours until dawn.

Layer up even more warmly than you imagine you'll need; think radiational cooling! Find a dark open spot with no

local lights to get in your eyes, lie back in a reclining lawn chair, and gaze up into the stars. Be patient. As your

eyes adapt to the dark, you may see a Geminid every minute or two on average as night grows late.

Friday, December 14

• In early evening, Mars shines above the Moon. Mars is about twice as big as the Moon in physical diameter, but

it's currently 425 times farther away.

Source: Sky and Telescope Return to Contents

10 of 14

ISS Sighting Opportunities (from Denver)

Date Visible Max Height Appears Disappears

Tue Dec 11, 5:58 PM 5 min 87° 10° above NW 28° above SE

Wed Dec 12, 5:06 PM 6 min 45° 10° above NW 11° above ESE

Wed Dec 12, 6:45 PM 2 min 17° 17° above SW 13° above SSW

Thu Dec 13, 5:51 PM 5 min 34° 12° above WNW 12° above SSE

Fri Dec 14, 4:59 PM 5 min 72° 19° above WNW 10° above SE

Sighting information for other cities can be found at NASA’s Satellite Sighting Information

NASA-TV Highlights (all times Eastern Time Zone)

December 11, Tuesday

10 a.m. – Coverage of Russian Spacewalk, scheduled to begin at 11:03 a.m. EST and will last around 6

hours (All Channels)

8 p.m. – Live from The Washington National Cathedral: The Smithsonian National Air and Space Museum

Presents “The Spirit of Apollo”—A Celebration of the 50th Anniversary of the Apollo 8 Mission to the Moon

(All Channels)

December 12, Wednesday

7:40 a.m. – German Media speak with International Space Station Commander Alexander Gerst of the

European Space Agency (All Channels)

(No earlier than) 3 p.m. – RS-25 Engine Test (All Channels)

10 a.m., 1 p.m. – Replay of The Smithsonian National Air and Space Museum Presents “The Spirit of

Apollo”—A Celebration of the 50th Anniversary of the Apollo 8 Mission to the Moon (All Channels)

3 p.m.-4 p.m. – International Space Station Expedition 59-60 Crew News Conference (All Channels)

8 p.m., 10 p.m. – Replay of the ISS Expedition 59-60 Crew News Conference (All Channels)

December 14, Friday

12 p.m. – SpaceCast Weekly (All Channels)

Watch NASA TV online by going to the NASA website. Return to Contents

11 of 14

Space Calendar

Dec 11 - Chang'e 4, Moon Orbit Insertion

Dec 11 - Colloquium: In Search for Most Ancient Asteroids to Tell Us the Story of the Origin of Our Solar System, Tucson, Arizona

Dec 11 - Hyperbolic Object A/2018 W1 Closest Approach To Earth (1.651 AU)

Dec 11 - Webinar: The IPCC Process and our Changing Oceans, Ecosystems and Human Communities

Dec 11-12 - International Workshop: Dark Matter and Stars, Lisbon, Portugal

Dec 12 - Comet 46P/Wirtanen Perihelion (1.055 AU)

Dec 12 - Asteroid 9617 Grahamchapman Closest Approach To Earth (1.000 AU)

Dec 12 - Asteroid 477 Italia Closest Approach To Earth (1.533 AU)

Dec 12 - Asteroid 12382 Niagara Falls Closest Approach To Earth (1.896 AU)

Dec 12 - Colloquium: CSI Apollo - Recreating the Iconic Earthrise Photograph, Greenbelt, Maryland

Dec 12 - Colloquium: Searching for Helical Magnetic Fields in the Milky Way Galaxy, Sydney, Australia

Dec 12-14 - 9th Symposium on Large TPCs for Low-energy Rare Event Detection, Paris, France

Dec 12-14 - Workshop: The CMB in HD - The Low-noise High-resolution Frontier, New York, New York

Dec 12-14 - Aotearoa Fundamental Physics Workshop 2018: Observer-Dependent Entropy, Wellington, New Zealand

Dec 13 - VCLS 1/ CeREs/ ALBus/ CHOMPTT/ Da Vinci/ ISX (CP 11)/ NMTSat/ RSat-P/ Shields 1/ STF 1/ CubeSail 1 & 2/ TOMSat EagleScout (AeroCube 11A) & TOMSat R3 (AeroCube 11B)/ SHFT 1 Electron Launch

Dec 13 - Geminids Meteor Shower Peak

Dec 13 - Comet 253P/PANSTARRS Closest Approach To Earth (1.640 AU)

Dec 13 - Apollo Asteroid 2015 XX169 Near-Earth Flyby (0.043 AU)

Dec 13 - Asteroid 7273 Garyhuss Closest Approach To Earth (1.350 AU)

Dec 13 - Asteroid 3852 Glennford Closest Approach To Earth (1.773 AU)

Dec 14 - Comet 137P/Shoemaker-Levy Perihelion (1.929 AU)

Dec 14 - Comet 198P/ODAS Perihelion (2.006 AU)

Dec 14 - Amor Asteroid 2018 VS9 Near-Earth Flyby (0.083 AU)

Dec 14 - Asteroid 289586 Shackleton Closest Approach To Earth (1.394 AU)

Dec 14 - Royal Astronomical Society (RAS) Ordinary Meeting, London, United Kingdom

Dec 14 - Meeting: 30 Years of Planetary Astronomy with H3+, London, United Kingdom

Dec 14 - Meeting: A Centenary of Astrophysical Jet Studies - A Review of the Physics Driving the Observed Jet Structure, London, United Kingdom

Dec 14 - Lecture: Making Galaxies on a Supercomputer, Pasadena, California

Dec 14-18 - Workshop on Neutrino Physics and Astrophysics, Mumbai, India

Dec 15 - Ziyuan 2D/BNU-1/Tianyi MV-1 CZ-4B Launch

Dec 15 - Comet 171P/Spahr Closest Approach To Earth (0.858 AU)

Dec 15 - Apollo Asteroid 2018 VO9 Near-Earth Flyby (0.007 AU)

Dec 15 - Educators Workshop: Engineering a Journey to Mars, Downey, California

Source: JPL Space Calendar Return to Contents

12 of 14

Food for Thought

SwRi Solar Activity Research Provides Insight into Sun’s Past, Future

A team led by SwRI integrated a sunspot drawing made by Hevelius in 1644 (top) with images from NASA’s Solar

Dynamics Observatory to illustrate how widely varying telescopes and observation techniques can affect data. The team

integrated data from 700 observations to assess the reliability of historical data, to better understand the history of solar

activity. Image Courtesy of NASA/SDO/SwRI

Andrés Muñoz-Jaramillo of Southwest Research Institute and José Manuel Vaquero of University of

Extremadura have developed a new technique for looking at historic solar data to distinguish trustworthy

observations from those that should be used with care. This work is critical to understanding the Sun’s past

and future as well as whether solar activity plays a role in climate change.

“Scientists have been monitoring solar activity since Galileo made the first drawings in 1612 by counting

sunspots and groups of sunspots,” said SwRI’s Muñoz-Jaramillo, a senior research scientist who is first author

of a paper in Nature Astronomy outlining the research. “However, putting all observations in perspective is

quite challenging due to wide-ranging observation techniques and telescope magnifications used. We see

much more now and our understanding of what we see changes the way we count spots.”

The team created a technique that takes all historic data gathered and digitized thus far and combines them

visually, to provide a complete picture of the data we have and where are we missing information. Roughly

every 11 years, the magnetic structure and activity of the Sun cycle between periods known as solar minimum

and solar maximum. During solar maximum, the Sun emits high levels of solar radiation, ejects large amounts

13 of 14

solar material and displays large numbers of intense sunspots, flares and other phenomena. During solar

minimum, this activity is muted. Changes on the Sun cause effects in space, in the atmosphere and on Earth’s

surface.

The Sun also experiences century-long variations, including periods of abnormally low solar activity called

grand minima. Maunder Minimum refers to a 70-year period between 1645 and 1715 when observations

revealed thousands of days without sunspots. The term was the title of a 1976 paper that first identified these

longer cycles, named for a husband-wife team of solar astronomers from the late 17th century. In contrast,

modern observations typically record hundreds of days without sunspots over similar periods of time.

“Scientists are investigating whether Maunder Minimum could serve as archetype of a grand minimum in

magnetic activity for the Sun and other stars,” Muñoz said. However, data prior to, during and after the

Maunder Minimum, is less reliable and lacks the precision and coverage of today’s measurements. Recent

reevaluations of sunspot observations have yielded a conflicted view on the evolution of solar activity over the

last 400 years.

“Due to our lack coverage we don’t know if the Sun took decades to recover from the Maunder Minimum to

the levels of solar activity we see today, or if it was quick as if a switch had been turned on,” Munoz said.

“There is currently a team of experts from all over the world working hard to find the best way of combining

these data. In the meantime, one has to be very careful when using historic sunspot data to study potential

links between the Sun and changes in terrestrial climate, given that these effects would be complex and

subtle. Our work uses historical data to provide context to users of these estimates that may not be aware of

their limitations.”

“Visualization of the challenges and limitations of the long-term sunspot number record” was published Dec.

10 in Nature Astronomy. This work is part of an international effort to reconstruct solar activity levels during

the last 400 years, led by the SILSO World Data Center and funded by the NASA Grand Challenge and Living

with a Star programs, and other Spanish institutions.

Source: Southwest Research Institute Return to Contents

ESA -- An Artificial Proba-2 View of the Solar

North Pole

This image extrapolates low-latitude Proba-2

observations of the Sun to reconstruct a view of the

star’s pole. While the poles cannot be seen directly,

when spacecraft observe the solar atmosphere they

gather data on everything along their line of sight, also

viewing the atmosphere extending around the disc of

the Sun (the apparent glow around the main disc of the

Sun, which also extends over the poles). Scientists can

use this to infer the appearance of the polar regions. In

order to estimate the properties of the solar

atmosphere over the poles, they continuously image the

main disc of the Sun and take small slivers of data from

the outer and upper regions of the star as it rotates,

compensating for the fact that the Sun does not rotate

at constant speeds at all latitudes. Over time, these

small arrays of data can be combined to approximate a

view of the pole, as shown in this view.

Credits: ESA/Royal Observatory of Belgium

14 of 14

Space Image of the Week

Earth Enveloped in Airglow Image Credit: NASA

Explanation: On October 7, 2018, an astronaut aboard the International Space Station (ISS) shot this photograph while orbiting at an altitude of more than 250 miles over Australia.

The orange hue enveloping Earth is known as airglow—diffuse bands of light that stretch 50 to 400 miles into

our atmosphere. The phenomenon typically occurs when molecules (mostly nitrogen and oxygen) are

energized by ultraviolet (UV) radiation from sunlight. To release that energy, atoms in the lower atmosphere

bump into each other and lose energy in the collision. The result is colorful airglow.

Airglow reveals some of the workings of the upper reaches of our atmosphere. It can help scientists learn

about the movement of particles near the interface of Earth and space, including the connections

between space weather and Earth weather. Satellites offer one way to study this dynamic zone. NASA’s

Ionospheric Connection Explorer (ICON) satellite will help scientists understand the physical processes at work

where Earth’s atmosphere interacts with near-Earth space.

Source: NASA Return to Contents