vendredi 26 juin 2020

Cassidy and Behnken Conclude Spacewalk to Replace Batteries

ISS - Expedition 63 Mission patch / EVA - Extra Vehicular Activities patch.

June 26, 2020

Image above: NASA Astronauts Chris Cassidy and Bob Behnken during spacewalk to replace batteries to upgrade the power supply capability. Image Credits: NASA TV/ISS HD Live Now/ Aerospace/Roland Berga.

NASA astronauts Chris Cassidy and Robert Behnken concluded their spacewalk at 1:39 p.m. EDT, after six hours and seven minutes. The two NASA astronauts completed all the work planned for this first of four spacewalks to replace batteries that provide power for the station’s solar arrays on the starboard truss of the complex as well as initial tasks originally planned for the second scheduled spacewalk next Wednesday. The new batteries provide an improved and more efficient power capacity for operations.

The spacewalkers removed five of six aging nickel-hydrogen batteries for one of two power channels for the starboard 6 (S6) truss, installed two of three new lithium-ion batteries, and installed two of three associated adapter plates that are used to complete the power circuit to the new batteries. Mission control reports that the two new batteries are working.

Image above: NASA Astronauts Chris Cassidy and Bob Behnken during spacewalk to replace batteries to upgrade the power supply capability. Image Credit: NASA TV.

Cassidy and Behnken are scheduled to complete the upgrade to this initial power channel in a second spacewalk on July 1, during which they will install one more lithium-ion battery and one more adapter plate and remove the sixth nickel-hydrogen battery that will no longer be used.

This was the seventh spacewalk for both each astronaut. Cassidy now has spent a total of 37 hours and 21 minutes spacewalking, and Behnken has spent a total of 43 hours and 40 minutes spacewalking.

Image above: NASA Astronauts Chris Cassidy and Bob Behnken during spacewalk to replace batteries to upgrade the power supply capability. Image Credits: NASA TV/ISS HD Live Now/ Aerospace/Roland Berga.

Space station crew members have conducted 228 spacewalks in support of assembly and maintenance of the orbiting laboratory. Spacewalkers have now spent a total of 59 days, 18 hours, and 33 minutes working outside the station.

Related links:

Expedition 63:

Commercial Crew Program:

Space Station Research and Technology:

International Space Station (ISS):

Images (mentioned), Text, Credits: NASA/Norah Moran/ Aerospace/Roland Berga.

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Space Station Science Highlights: Week of June 22, 2020

ISS - Expedition 63 Mission patch.

June 26, 2020

Crew members aboard the International Space Station conducted research on liquid phase sintering in space, measuring neutron radiation aboard the station, and the properties of wet foam during the week of June 22.

Image above: This image of Earth taken from the space station shows a Saharan dust cloud that has blown over the Atlantic Ocean nearing the Caribbean Sea. The Progress 74 resupply ship from Russia is in the left foreground. Image Credit: NASA.

Now in its 20th year of continuous human presence, the space station provides a platform for long-duration research in microgravity and for learning to live and work in space. NASA’s Commercial Crew Program, once again launching astronauts on American rockets and spacecraft from American soil, increases the crew time available for science on the orbiting lab.

Here are details on some of the microgravity investigations currently taking place:

Sintering space exploration materials

Image above: NASA astronaut Doug Hurley works on operations for the Electrolysis Measurement investigation, which examines the influence of gravity on electrolytic gas evolution. Animation Credit: NASA.

The crew exchanged cartridges to run the Materials Science Laboratory Sample Cartridge Assembly-Gravitational Effects on Distortion in Sintering (MSL SCA-GEDS-German) investigation. Sintering is the process of heating different materials to compress their particles together. Liquid phase sintering is a way to fabricate materials for a wide range of applications such as tools and automotive engine parts. In the future, the process could be used for in-space fabrication and repair, making replacement components from metal powder during extraterrestrial exploration, and fabricating structures on the Moon using lunar regolith. This experiment focuses on forecasting density, size, shape, and properties for liquid phase sintered bodies in different gravity conditions.

Image above: Example of a liquid phase sintered tungsten alloy. The MSL SCA-GEDS-German investigation looks at forecasting density, size, shape, and properties for liquid phase sintered bodies in different gravity conditions. Image Credit: San Diego State University.

Rating radiation risk

Neutrons produced when cosmic rays strike the atoms of a spacecraft or the human body can pose a risk to the health of astronauts. An investigation from the Canadian Space Agency, Radi-N2 Neutron Field Study (Radi-N2), characterizes the neutron radiation environment aboard the space station using eight bubble detectors that measure only this type of radiation. During the week, crew members deployed detectors for the investigation, which are attached at fixed locations inside the space station and carried by a crew member.

Radi-N2 follows a previous investigation, RaDI-N, to help reveal the sources of neutron exposure and support development of appropriate protective measures for future spaceflights.

Watching bubbles grow and rearrange

Image above: Image from a run of the Electrolysis Measurement investigation examining the influence of gravity on electrolytic gas evolution. The process passes an electric current through a substance to separate out gases in the form of bubbles and could be used in microfluidic devices to produce oxygen in spacecraft and future human habitations on the Moon and Mars. Image Credit: NASA.

Solid and liquid foams are used in everything from detergents to food products, medicine, oil cleanup, and firefighting. On Earth, it is difficult to study foams because gravity quickly breaks them down, but that problem goes away in microgravity. Using the Fluid Science Laboratory (FSL), a multiuser facility designed by the ESA (European Space Agency) for conducting fluid physics research in microgravity, FSL Soft Matter Dynamics - Hydrodynamics of Wet Foams (FOAM) studies bubble size and rearrangement dynamics for wet or liquid foams. A better understanding of those properties could help industry improve processes using foams. During the week, crew members exchanged sample containers for the ESA investigation.

Other investigations on which the crew performed work:

- Capillary forces, the interaction of a liquid with the solid sides of a narrow tube that acts to draw the fluid up the tube, act even in the absence of gravity. Capillary Driven Microfluidics examines capillary flow in small devices to improve understanding of how it works in microgravity. Microfluidic devices could be used to develop more portable, robust, and affordable medical diagnostic tools to protect the health of astronauts on future long-term missions.

- Electrolytic Gas Evolution Under Microgravity (Electrolysis Measurement) examines the influence of gravity on electrolytic gas evolution. This process, which uses electrodes to pass an electric current through a substance and separate out gases in the form of bubbles, could be used in microfluidic devices to produce oxygen in spacecraft and future human habitations on the Moon and Mars.

- Acoustic Diagnostics, an investigation sponsored by ESA (European Space Agency), tests the hearing of crew members before, during, and after flight to assess possible adverse effects of noise and the microgravity environment of the space station.

- Plasma Kristall-4 (PK-4), a collaboration between the ESA (European Space Agency) and the Russian Federal Space Agency (Roscosmos), studies complex plasmas, low temperature gaseous mixtures of ionized gas, neutral gas, and micron-sized particles. The particles can become highly charged and interact with each other, leading to self-organized structures called plasma crystals.

Space to Ground: Channeling Energy: 06/26/2020

Related link:

Expedition 63:

Commercial Crew Program:


Radi-N2 Neutron Field Study (Radi-N2):



Spot the Station:

ISS National Lab:

Space Station Research and Technology:

International Space Station (ISS):

Images (mentioned), Animation (mentioned), Video (NASA), Text, Credits: NASA/Michael Johnson/John Love, Lead Increment Scientist Expedition 63.

Best regards,

NASA-NOAA’s Suomi NPP Satellite Analyzes Saharan Dust Aerosol Blanket

NOAA & NASA - Suomi NPP Mission patch.

June 26, 2020

Dust storms from Africa’s Saharan Desert traveling across the Atlantic Ocean are nothing new, but the current dust storm has been quite expansive and NASA satellites have provided a look at the massive June plume. NASA-NOAA’s Suomi NPP satellite showed the blanket of dust had moved over the Gulf of Mexico and extended into Central America and over part of the eastern Pacific Ocean.

Image above: This June 24, 2020 image is from the Suomi NPP OMPS aerosol index. The dust plume moved over the Yucatan Peninsula and up through the Gulf of Mexico. The largest and thickest part of the plume is visible over the eastern and central Atlantic. Image Credits: NASA/NOAA, Colin Seftor.

NASA uses satellites and other resources to track aerosol particles made of desert dust, smoke, and volcanic ash. The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard Suomi NPP provided a visible image while the Ozone Mapping and Profiling Suite (OMPS) Nadir-Mapper (NM) instrument aboard the Suomi-NPP satellite provided absorbing aerosol index values. The OMPS index indicates the presence of light absorbing aerosol particles (ultraviolet (UV)-absorbing particles in the air) such as desert dust. The absorbing aerosol index is related to both the thickness and height of the aerosol layer.

The Absorbing Aerosol Index is useful for identifying and tracking the long-range transport of volcanic ash from volcanic eruptions, smoke from wildfires or biomass burning events and dust from desert dust storms. These aerosol particals can even be tracked over clouds and areas covered by snow and ice.

Image above: This image is a composite of the OMPS aerosol index and the VIIRS visible image both from NASA/NOAA’s Suomi NPP satellite on June 24. The image shows the dust plume moved over the Yucatan Peninsula and up through the Gulf of Mexico. Image Credits: NASA/NOAA, Colin Seftor.

Colin Seftor, an atmospheric scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md., created imagery from the Suomi NPP OMPS absorbing aerosol index and visible imagery from the VIIRS instrument He said that on June 23 and 24 the dust plume had moved completely over Mexico’s Yucatan Peninsula, up through the Gulf of Mexico and into southern Texas. “At that point, the situation becomes more complicated because the absorbing aerosol index signal seen further north into Texas, Oklahoma, Nebraska, etc., is probably a mix of dust and smoke from the numerous fires burning in the southwest U.S. You can also see that the dust traveled over Central America and out into the Eastern Pacific Ocean.”

On June 25, an animation that combined OMPS aerosol index and VIIRS visible imagery from NASA/NOAA’s Suomi NPP satellite was created at NASA Goddard showing the movement the Saharan dust cloud from June 15 to 25, 2020,. The animation showed the dust plume streamed from Africa’s west coast over the Atlantic into the Caribbean Sea and up through the Gulf of Mexico over some of the Gulf states.

Aerosol particles absorb and scatter incoming sunlight, which reduces visibility and increases the optical depth. Aerosol particles have an effect on human health, weather and the climate. Aerosol particles are produced from many events including human activities such as pollution from factories and natural processes such as smoke from fires, dust from dust storms, sea salt from breaking waves, and volcanic ash from volcanoes. Aerosol particles compromise human health when inhaled by people with asthma or other respiratory illnesses. Aerosol particles also affect weather and climate by cooling or warming the earth as well as enhancing or preventing cloud formation.

Image above: This "true-color" composite image of the Saharan Dust plume was captured by the VIIRS instrument aboard NASA/NOAA’s Suomi NPP satellite on June 24, 2020. The bright streaks seen at regular intervals are due to sun glint off of the ocean surface. Image Credits: NASA/NOAA, Colin Seftor.

On June 18, NASA’s Earth Observatory noted the thickest parts of the plume appeared to stretch about 2,500 kilometers (1,500 miles) across the Atlantic Ocean. By June 24, the plume extended over 5,000 miles.

Dust from Africa can affect air quality as far away as North and South America if it is mixed down to ground level. But dust can also play an important ecological role, such as, fertilizing soils in the Amazon and building beaches in the Caribbean. The dry, warm, and windy conditions associated with Saharan Air Layer outbreaks from Africa can also suppress the formation and intensification of tropical cyclones.

Suomi NPP satellite. Image Credits: NOAA/NASA

“While Saharan dust transport across the ocean to the Americas is not uncommon, the size and strength of this particular event is quite unusual,” Seftor said. “Also, if you look off the coast of Africa you can see yet another large cloud coming off the continent, continuing to feed the long chain of dust traveling across the Atlantic.”

Animated GIFs of the dust storm's activity:

This animation shows the aerosols in the Saharan dust plume from June 15 to 25, 2020. It was created from the Suomi NPP OMPS aerosol index. The dust plume moved from Africa’s west coast over the Atlantic Ocean into the Caribbean Sea and up through the Gulf of Mexico. The largest and thickest part of the plume is visible over the eastern and central Atlantic. Animation Credits: NASA/NOAA, Colin Seftor.

This "true-color" composite animation of visible satellite imagery shows the movement of the Saharan Dust plume from June 15 to 25, 2020. It was captured by the VIIRS instrument aboard NASA/NOAA’s Suomi NPP satellite. The bright streaks seen at regular intervals are due to sun glint off the ocean surface. Image Credits: NASA/NOAA, Colin Seftor.

This animation of the progression Saharan dust cloud across the Atlantic Ocean from June 15 to 25, 2020 combines OMPS aerosol index and VIIRS visible imagery from NASA/NOAA’s Suomi NPP satellite. The dust plume moved from Africa’s west coast over the Atlantic into the Caribbean Sea and up through the Gulf of Mexico. The largest and thickest part of the plume is visible over the eastern and central Atlantic Ocean. Animation Credits: NASA/NOAA, Colin Seftor.

Suomi NPP (National Polar-orbiting Partnership):

Ozone Mapping and Profiling Suite (OMPS):

Images (mentioned), Animations (mentioned), Text, Credits: NASA/Lynn Jenner/GSFC, By Rob Gutro. 


Hubble Captures Galaxy on Edge

NASA - Hubble Space Telescope patch.

June 26, 2020

The galaxy known as NGC 5907 stretches wide across this image. Appearing as an elongated line of stars and dark dust, the galaxy is categorized as a spiral galaxy just like our own Milky Way. In this new image from the NASA/ESA Hubble Space Telescope, we don’t see the beautiful spiral arms because we are viewing it edge-on, like looking at the rim of a plate. It is for this reason that NGC 5907 is also known as the Knife Edge galaxy.

The Knife Edge galaxy is about 50 million light-years from Earth, lying in the northern constellation of Draco. Although not visible in this image, ghostly streams of stars on large arching loops extend into space, circling around the galaxy; they are believed to be remnants of a small dwarf galaxy, torn apart by the Knife Edge galaxy and merged with it over 4 billion years ago.

Hubble Space Telescope (HST)

For more information about Hubble, visit:

Text Credits: ESA (European Space Agency)/NASA/Rob Garner/Image, Animation Credits: ESA/Hubble & NASA, R. de Jong; Acknowledgment: Judy Schmidt (Geckzilla).


jeudi 25 juin 2020

Black Hole Collision May Have Exploded with Light

JPL - Jet Propulsion Laboratory logo.

June 26, 2020

Possible light flare observed from small black holes within the disk of a massive black hole 

Image above: Artist's concept of a supermassive black hole and its surrounding disk of gas. Embedded within this disk are two smaller black holes orbiting one another. Using data from the Zwicky Transient Facility (ZTF) at Palomar Observatory, researchers have identified a flare of light suspected to have come from one such binary pair soon after they merged into a larger black hole. The merger of the black holes would have caused them to move in one direction within the disk, plowing through the gas in such a way to create a light flare. The finding, while not confirmed, could amount to the first time that light has been seen from a coalescing pair of black holes. These merging black holes were first spotted on May 21, 2019, by the National Science Foundation's Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector, which picked up gravitational waves generated by the merger. Image Credits: Caltech/R. Hurt (IPAC).

When two black holes spiral around each other and ultimately collide, they send out ripples in space and time called gravitational waves. Because black holes do not give off light, these events are not expected to shine with any light waves, or electromagnetic radiation. But some theorists have come up with ways in which a black hole merger might explode with light. Now, for the first time, astronomers have seen evidence for one of these light-producing scenarios.

With the help of Caltech's Zwicky Transient Facility (ZTF), funded by the National Science Foundation (NSF) and located at Palomar Observatory near San Diego, the scientists have spotted what might be a flare of light from a pair of coalescing black holes. The black hole merger was first witnessed by the NSF's Laser Interferometer Gravitational-wave Observatory (LIGO) and the European Virgo detector on May 21, 2019, in an event called S190521g. As the black holes merged, jiggling space and time, they sent out gravitational waves.

While this was happening, ZTF was performing its robotic survey of the sky that captured all kinds of objects that flare, erupt, or otherwise vary in the night sky. One flare the survey caught, generated by a distant active supermassive black hole, or quasar, called J1249+3449, was pinpointed to the region of the gravitational-wave event S190521g.

"This supermassive black hole was burbling along for years before this more abrupt flare," says Matthew Graham, a research professor of astronomy at Caltech and the project scientist for ZTF. "The flare occurred on the right timescale, and in the right location, to be coincident with the gravitational-wave event. In our study, we conclude that the flare is likely the result of a black hole merger, but we cannot completely rule out other possibilities." Graham is lead author of the new study, published today, June 25, in the journal Physical Review Letters.

"ZTF was specifically designed to identify new, rare, and variable types of astronomical activity like this," says NSF Division of Astronomical Science Director Ralph Gaume. "NSF support of new technology continues to expand how we can track such events."

How do two merging black holes erupt with light? In the scenario outlined by Graham and his colleagues, two partner black holes were nestled within a disk surrounding a much larger black hole.

"At the center of most galaxies lurks a supermassive black hole. It's surrounded by a swarm of stars and dead stars, including black holes," says co-author K. E. Saavik Ford of the City University of New York (CUNY) Graduate Center, the Borough of Manhattan Community College (BMCC), and the American Museum of Natural History (AMNH). "These objects swarm like angry bees around the monstrous queen bee at the center. They can briefly find gravitational partners and pair up but usually lose their partners quickly to the mad dance. But in a supermassive black hole's disk, the flowing gas converts the mosh pit of the swarm to a classical minuet, organizing the black holes so they can pair up," she says.

Once the black holes merge, the new, now-larger black hole experiences a kick that sends it off in a random direction, and it plows through the gas in the disk. "It is the reaction of the gas to this speeding bullet that creates a bright flare, visible with telescopes," says co-author Barry McKernan, also of the CUNY Graduate Center, BMCC, and AMNH.

Such a flare is predicted to begin days to weeks after the initial splash of gravitational waves produced during the merger. In this case, ZTF did not catch the event right away, but when the scientists went back and looked through archival ZTF images months later, they found a signal that started days after the May 2019 gravitational-wave event. ZTF observed the flare slowly fade over the period of a month.

The scientists attempted to get a more detailed look at the light of the supermassive black hole, called a spectrum, but by the time they looked, the flare had already faded. A spectrum would have offered more support for the idea that the flare came from merging black holes within the disk of the supermassive black hole. However, the researchers say they were able to largely rule out other possible causes for the observed flare, including a supernova or a tidal disruption event, which occurs when a black hole essentially eats a star.

What is more, the team says it is not likely that the flare came from the usual rumblings of the supermassive black hole, which regularly feeds off its surrounding disk. Using the Catalina Real-Time Transient Survey, led by Caltech, they were able to assess the behavior of the black hole over the past 15 years, and found that its activity was relatively normal until May of 2019, when it suddenly intensified.

"Supermassive black holes like this one have flares all the time. They are not quiet objects, but the timing, size, and location of this flare was spectacular," says co-author Mansi Kasliwal (MS '07, PhD '11), an assistant professor of astronomy at Caltech. "The reason looking for flares like this is so important is that it helps enormously with astrophysics and cosmology questions. If we can do this again and detect light from the mergers of other black holes, then we can nail down the homes of these black holes and learn more about their origins."

The newly formed black hole should cause another flare in the next few years. The process of merging gave the object a kick that should cause it to enter the supermassive black hole's disk again, producing another flash of light that ZTF should be able to see.

The Physical Review Letters paper, titled, "A Candidate Electromagnetic Counterpart to the Binary Black Hole Merger Gravitational Wave Event GW190521g," was funded by the NSF, NASA, the Heising-Simons Foundation, and the GROWTH (Global Relay of Observatories Watching Transients Happen) program. Other co-authors include: K. Burdge, S.G. Djorgovski, A.J. Drake, D. Duev, A.A. Mahabal, J. Belecki, R. Burruss, G. Helou, S.R. Kulkarni, F.J. Masci, T. Prince, D. Reiley, H. Rodriguez, B. Rusholme, R.M. Smith, all from Caltech; N.P. Ross of the University of Edinburgh; Daniel Stern of the Jet Propulsion Laboratory, managed by Caltech for NASA; M. Coughlin of the University of Minnesota; S. van Velzen of University of Maryland, College Park and New York University; E.C. Bellm of the University of Washington; S.B. Cenko of NASA Goddard Space Flight Center; V. Cunningham of University of Maryland, College Park; and M.T. Soumagnac of the Lawrence Berkeley National Laboratory and the Weizmann Institute of Science.

In addition to the NSF, ZTF is funded by an international collaboration of partners, with additional support from NASA, the Heising-Simons Foundation, members of the Space Innovation Council at Caltech, and Caltech itself.

Related links:

Caltech's Zwicky Transient Facility (ZTF):

National Science Foundation (NSF):

The Physical Review Letters paper:


Image (mentioned), Text, Credits: NASA/JPL/Written by Whitney Clavin.


NASA TV Broadcasts Battery Swap Spacewalk Friday

ISS - Expedition 63 Mission patch.

June 25, 2020

NASA astronauts Chris Cassidy and Robert Behnken are scheduled to depart the International Space Station’s Quest airlock Friday for a spacewalk to replace batteries to upgrade the power supply capability.

The duo will set their spacesuits to battery power about 7:35 a.m. EDT Friday, signifying the start of their spacewalk, which may last as long as seven hours. NASA will begin its live coverage on NASA Television and the agency’s website at 6 a.m.


Image above: Astronauts (from left) Chris Cassidy and Bob Behnken are pictured during previous spacewalks on earlier missions at the space station. Image Credit: NASA.

NASA posted a video providing an animation of the spacewalk activities to depict how they will be replacing existing nickel-hydrogen batteries on one of two power channels on the far starboard truss (S6 Truss) of the station with new lithium-ion batteries that arrived on a Japanese cargo ship last month.

They are scheduled for a second spacewalk to continue the work on Wednesday, July 1. The battery replacement work is the final series of power upgrade spacewalks that began in January 2017.

ISS maintenance spacewalk. Animation Credit: NASA

This will be the 228th spacewalk in support of space station assembly and maintenance. Cassidy will be extravehicular crew member 1, wearing the spacesuit with red stripes, while Behnken will be extravehicular crew member 2, wearing the spacesuit with no stripes. It will be the seventh spacewalk for each astronaut.

Related links:

Expedition 63:

Commercial Crew Program:

HTV-9 resupply ship:

Space Station Research and Technology:

International Space Station (ISS):

Image (mentioned), Animation (mentioned), Text, Credits: NASA/Mark Garcia.

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Hubble Watches the “Flapping” of Cosmic Bat Shadow

ESA - Hubble Space Telescope logo.

June 25, 2020

Bat Shadow (2018 Observation) Serpens Nebula, seen by HAWK-I

The young star HBC 672 is known by its nickname of Bat Shadow because of its wing-like shadow feature. The NASA/ESA Hubble Space Telescope has now observed a curious “flapping” motion in the shadow of the star’s disc for the first time. The star resides in a stellar nursery called the Serpens Nebula, about 1300 light-years away.

Serpens Nebula, seen by HAWK-I

The Hubble Space Telescope captured a striking observation of the fledgling star’s unseen, planet-forming disc in 2018. This disc casts a huge shadow across a more distant cloud in a star-forming region — like a fly wandering into the beam of a flashlight shining on a wall.

Wide-field view of the Serpens Nebula (ground-based image)

Now, astronomers have serendipitously observed the Bat Shadow’s “flapping”. This may have been caused by a planet pulling on the disc and warping it. “You have a star that is surrounded by a disc, and the disc is not like Saturn’s rings — it’s not flat. It’s puffed up. And so that means that the light from the star, if it goes straight up, can continue straight up — it’s not blocked by anything. But if it tries to go along the plane of the disc, it doesn’t get out, and it casts a shadow,” explained lead author Klaus Pontoppidan, an astronomer at the Space Telescope Science Institute (STScI) in Baltimore, USA, whose team have published these results [1].

The Bat Shadow's "Flapping"

This “flapping” finding was also a surprise. Pontoppidan and his team observed the shadow in several filters over a period of 13 months. When they combined the old and new images, the shadow appeared to have moved.

Hubble Space Telescope (HST)

The shadow is so large — about 200 times the diameter of our Solar System — that light doesn’t travel instantaneously across it. In fact, it takes about 45 days for the light to travel from the star out to the best defined edge of the shadow.

Zooming Into the Bat Shadow and its “Flapping”

Pontoppidan and his team calculate that a planet warping the disc would orbit its star in no fewer than 180 days. They estimate that it would be about the same distance from its star as Earth is from the Sun. Pontoppidan’s team also suggest the disc must be flared, with an angle that increases with distance — like a trumpet. This shape of its two peaks and two dips would explain the “flapping” of the shadow. The team also speculates that a planet is embedded in the disc, inclined to the disc’s plane. If it’s not a planet, a less likely explanation is a lower-mass stellar companion orbiting HBC 672 outside the plane of the disc. Pontoppidan and his team doubt this is the case, based on the thickness of the disc. There is also no current evidence for a binary companion.

Animation: The Bat Shadow’s “Flapping” Motion Explained

The disc is a circling structure of gas, dust, and rock, and is too small and too distant to be seen, even by Hubble. However, based on the projected shadow, scientists do know that its height-to-radius ratio is 1:5.


[1] The team’s paper appears in an upcoming edition of the Astrophysical Journal:

More information:

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

The international team of astronomers in this study consists of K. Pontoppidan, J. Green, T. Pauly, C. Salyk, and J. DePasquale.

These observations were conducted under Hubble observation programmes SNAP 14181 (PI: T. Megeath) and GO 15597 (M. Mutchler).


Images of Hubble:

Hubble’s 2018 observations of the Bat Shadow:

HubbleSite release:

Images, Animation, Text,  Credits: NASA, ESA, K. Pontoppidan/Bethany Downer/STScI/Klaus Pontoppidan/ESO/Digitized Sky Survey 2 (Acknowledgement: Davide De Martin)/Videos: ESA/Hubble, K. Pontoppidan, L. Calçada, M. Kornmesser/Music: Konstantino Polizois/ESA/Hubble, Digitized Sky Survey, L. Calçada, Nick Risinger ( Konstantino Polizois.

Best regards,

This Hopping Robot Could Explore the Solar System's Icy Moons

JPL - Jet Propulsion Laboratory logo.

June 25, 2020

SPARROW, a steam-powered robotic concept, could one day take giant leaps over some of the most hazardous terrains known (and unknown) in the solar system.

Image above: Moons In this artist's concept, a SPARROW robot uses steam propulsion to hop away from its lander home base to explore an icy moon's surface.Image Credits: NASA/JPL-Caltech.

Steam locomotion may sound like an antiquated way to get around, but it might be getting a science fiction makeover as we expand our reach into the solar system.

A novel robotic concept being investigated at NASA's Jet Propulsion Laboratory in Southern California would use steam propulsion to hop across the sort of icy terrains found on Jupiter's moon Europa and Saturn's moon Enceladus. Both are thought to host vast subsurface oceans of salty water under a thick ice crust. But while that makes them fascinating destinations for scientific study, the little we know about their surfaces could also make navigating them especially challenging.

That's where the Steam Propelled Autonomous Retrieval Robot for Ocean Worlds, or SPARROW, comes in. About the size of a soccer ball, the robot consists of a system of thrusters, avionics and instruments encased in a protective spherical cage. To keep the environment pristine for study, SPARROW would run not on rocket fuel but on steam produced from melted ice, traveling primarily through the air via short thrusts. In the sort of low-gravity environment found on those distant icy moons, there'd be no atmospheric drag to slow it down, enabling hops of many miles over landscapes that other robots would have difficulty navigating.

Hopping Robot Concept to Explore Frozen Ocean Worlds

Video above: NASA is researching a hopping robot that can easily navigate the harsh glacier-like terrain on icy worlds in our solar system. And that's just the tip of the iceberg. NASA 360 takes a look at the NASA Innovative Advanced Concept (NIAC) called S.P.A.R.R.O.W., a revolutionary approach to exploring frozen ocean worlds. Video Credit: NASA 360.

"The terrain on Europa is likely highly complex," said Gareth Meirion-Griffith, JPL roboticist and the lead researcher of the concept. "It could be porous, it might be riddled with crevasses, there might be meters-high penitentes" - long blades of ice known to form at high latitudes on Earth - "that would stop most robots in their tracks. But SPARROW has total terrain agnosticism; it has complete freedom to travel across an otherwise inhospitable terrain."

Animation above: This computer simulation shows a group of SPARROW robots exploring an icy moon's surface. The results of such simulations help scientists determine the most efficient hopping distance. Animation Credits: NASA/JPL-Caltech.

The concept depends on a lander serving as the home base for SPARROW. It would mine the ice and melt it down before loading the water onto the hopping robot. SPARROW would then heat the water inside its engines, creating bursts of steam to give a boost off the surface. When low on fuel, the hopping bot would return to the lander for more, also dropping off any scientific samples for further analysis.

To maximize the science investigations that could be done, many SPARROWs could be sent together, swarming around a specific location or splitting up to explore as much alien terrain as possible.

In 2018, SPARROW was awarded Phase I funding by the NASA Innovative Advanced Concepts (NIAC) program, which nurtures visionary ideas that could, someday, be used in future space missions. Phase I studies explore the overall viability and advance the Technology Readiness Level (TRL). Eligible recipients of Phase I awards can propose a follow-on Phase II study.

For SPARROW, the NIAC Phase I funding allowed the development and testing of different water-based propellant systems that could be used to produce steam in the most efficient way. Additionally, the SPARROW team was able to better understand how the spherical robot might tumble when landing on chaotic icy terrain by using computer simulations, thereby identifying the most efficient angle of launch and speed of hop.

"From this, and related propulsion calculations, we were able to determine that a single long hop would be more efficient that several smaller hops," added Meirion-Griffith.

NIAC is funded by NASA's Space Technology Mission Directorate, which is responsible for developing the new cross-cutting technologies and capabilities needed by the agency.

Related links:

NASA Innovative Advanced Concepts:

Steam Propelled Autonomous Retrieval Robot for Ocean Worlds (SPARROW):

Image (mentioned), Video (mentioned), Animation (mentioned), Text, Credits: NASA/Clare Skelly/JPL/Ian J. O'Neill.


Space agencies join forces to produce global view of COVID-19 impacts

ESA - European Space Agency logo.

June 25, 2020

In an unprecedented collaboration, ESA, NASA and JAXA (Japan Aerospace Exploration Agency) have created a new tool that combines a wealth of data from Earth-observing satellites to monitor the worldwide impacts of COVID-19. This new online platform is now available to the public.

COVID-19 Earth Observation Dashboard

The new ‘COVID-19 Earth Observation Dashboard’ integrates multiple satellite data records from the three space agencies with analytical tools to allow users to track changes in air and water quality, climate change, economic activity and agriculture. The tri-agency platform gives the general public and policy-makers a unique platform to explore the short and long term impacts of the coronavirus lockdown.

 Air quality changes

ESA’s Director for Earth Observation, Josef Aschbacher, comments, “The coronavirus pandemic has brought on unprecedented challenges with severe societal consequences. Earlier this month, ESA and the European Commission created the ‘Rapid Action COVID-19 Earth observation’ initiative which allowed for a European platform to provide COVID-related information using Copernicus Sentinel satellite data.

“As the challenges we face from COVID-19 are global by nature, international collaboration among space agencies is key. Through this close cooperation, ESA, NASA and JAXA have created a new centralised platform. Through this, we are making sure that our Earth observation programmes deliver their full potential to society, and in doing so, are helping humanity navigate through this crisis with more accurate information at its disposal.”

Thomas Zurbuchen, Associate Administrator for NASA’s Science Mission Directorate, says, “Together NASA, ESA, and JAXA represent a great human asset: advanced Earth-observing instruments in space that are used every day to benefit society and advance knowledge about our home planet.

“When we began to see from space how changing patterns of human activity caused by the pandemic were having a visible impact on the planet, we knew that if we combined resources, we could bring a powerful new analytical tool to bear on this fast-moving crisis.”

The Earth observation dashboard allows users to explore and investigate how regional lockdowns and social distancing measures have affected Earth’s air, land and water.

COVID-19 Earth Observation Dashboard tutorial

Air quality changes, for example, were one of the first-noticed impacts of the restrictions put in place to reduce the spread of the coronavirus disease. Nitrogen dioxide, which is caused by fumes from sclerotic traffic, the burning of fossil fuels, as well as industrial activity, show up clearly in satellite data. The dashboard brings together new and historical nitrogen dioxide datasets for comparison, as well as targeted regional areas including Los Angeles, Tokyo, Beijing, Paris and Madrid.

Changes in carbon dioxide are also highlighted in the dashboard to monitor how global and local reactions to the pandemic have changed concentrations of this greenhouse gas. The dashboard allows for the short-term and long-term changes in carbon dioxide on a global scale, as well as observations in selected urban areas such as New York, San Francisco and Delhi.

The dashboard also presents targeted satellite observations of total suspended matter and chlorophyll concentrations in select coastal areas, harbours and semi-enclosed bays to assess what has produced these water quality changes, how widespread they may be, and how long they last. Long Island Sound, the North Adriatic, and Tokyo Bay are among the areas examined.

COVID-19 Earth Observation Dashboard demo

The COVID-19 Earth Observation Dashboard also provides observations of shipping activity in ports, parked cars and nighttime lights in urban areas to show how specific sectors of the economy have been affected. These data are presented in the dashboard to quantify changes in Los Angeles, the Port of Dunkirk, Beijing and several other locations.

The dashboard uses data from NASA's Aura and OCO-2 satellites, JAXA’s GOSAT and ALOS-2 satellites, the Sentinel missions from the European Copernicus programme led by the European Commission, as well as nightlight maps using data acquired by the US Suomi NPP satellite.

The dashboard will continue to be expanded with new data added over the following months and new sections will be added. The COVID-19 Earth Observation Dashboard is available here:

An introduction to the COVID-19 Earth Observation Dashboard

Follow the live webstream on ESA WebTV at 09:00 EDT (15:00 CEST), where speakers and experts from ESA, NASA and JAXA will give a demonstration of the platform:

Related links:

Observing the Earth:




Images, Animation, Videos, Text, Credits: ESA/NASA/JAXA.


mercredi 24 juin 2020

Electricity transmission reaches even higher intensities

CERN - European Organization for Nuclear Research logo.

June 24, 2020

A superconducting electrical transmission line developed for the High-Luminosity LHC has set a new intensity record

Image above: The innovative electrical transmission line, designed for the HL-LHC, has been undergoing tests since mid-June (Image: CERN).

Intensity is rising at CERN. In the superconducting equipment testing hall, an innovative transmission line has set a new record for the transport of electricity. The link, which is 60 metres long, has transported a total of 54 000 amperes (54 kA, or 27 kA in either direction). “It is the most powerful electrical transmission line built and operated to date!” says Amalia Ballarino, the designer and project leader.

The line has been developed for the High-Luminosity LHC (HL-LHC), the accelerator that will succeed the Large Hadron Collider (LHC) and is scheduled to start up at the end of 2027. Links like this one will connect the HL-LHC’s magnets to the power converters that supply them.

CERN - Electricity transmission reaches even higher intensities

Video above: Interview with Amalia Ballarino, the superconducting link project leader, during the insertion of the line into its cryostat in February 2020 (Video: CERN).

The secret to the new line’s power can be summarised in one word: superconductivity.

The line is composed of cables made of magnesium diboride (MgB2), which is a superconductor and therefore presents no resistance to the flow of the current and can transmit much higher intensities than traditional non-superconducting cables. On this occasion, the line transmitted an intensity 25 times greater than could have been achieved with copper cables of a similar diameter. Magnesium diboride has the added benefit that it can be used at 25 kelvins (-248 °C), a higher temperature than is needed for conventional superconductors. This superconductor is more stable and requires less cryogenic power. The superconducting cables that make up the innovative line are inserted into a flexible cryostat, in which helium gas circulates.

The strands of magnesium diboride of which the cables are made were developed by industry, under CERN’s supervision. The cable manufacturing process was designed at CERN, before industrial production began. As the strands of magnesium diboride are fragile, manufacturing the cables requires considerable expertise. The current is transmitted from the power supply at room temperature to the flexible link by ReBCO high-temperature superconducting (HTS) cables.

Image above: A team member connects the superconducting link cables before the electrical transmission tests begin (Image: CERN).

Last year, an initial prototype transmitted a 40 kA intensity over a distance of 60 metres. The link that is currently being tested is the forerunner of the final version that will be installed in the accelerator. It is composed of 19 cables that supply the various magnet circuits and could transmit intensities of up to 120 kA! “We started the power tests by connecting just four cables, two at 20 kA and two at 7 kA,” explains Amalia Ballarino. New records are therefore expected to be set in the coming months.

This new type of electrical transmission line has applications far beyond the realm of fundamental research. Links like these, which can transfer vast amounts of current within a small diameter, could be used to deliver electricity in big cities, for example, or to connect renewable energy sources to populated areas.


CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 23 Member States.

Related links:

High-Luminosity LHC (HL-LHC):

Large Hadron Collider (LHC):


For more information about European Organization for Nuclear Research (CERN), visit:

Images (mentioned), Video (mentioned), Text, Credits: CERN/Corinne Pralavorio.

Best regards,

NASA Extends Deep Space Atomic Clock Mission

NASA - SCaN Mission patch.

June 24, 2020

Smart phone apps provide nearly instantaneous navigation on Earth; the Deep Space Atomic Clock could do the same for future robotic and human explorers.

Animation above: A technology demonstration called the Deep Space Atomic Clock could enable far-flung probes to get around using a navigation system similar to the GPS-based system we use on Earth. Animation Credits: NASA/JPL-Caltech.

As the time when NASA will begin sending humans back to the Moon draws closer, crewed trips to Mars are an enticing next step. But future space explorers will need new tools when traveling to such distant destinations. The Deep Space Atomic Clock mission is testing a new navigation technology that could be used by both human and robotic explorers making their way around the Red Planet and other deep space destinations.

In less than a year of operations, the mission has passed its primary goal to become one of the most stable clocks to ever fly in space; it is now at least 10 times more stable than atomic clocks flown on GPS satellites. In order to keep testing the system, NASA has extended the mission through August 2021. The team will use the additional mission time to continue to improve the clock's stability, with a goal of becoming 50 times more stable than GPS atomic clocks.

Launched in June 2019 and managed by NASA's Jet Propulsion Laboratory in Southern California, the toaster-size Deep Space Atomic Clock is a payload on a commercial satellite. As a technology demonstration, its goal is to advance in-space capabilities by developing instruments, hardware, software or the like that doesn't currently exist. These demonstration missions must also show that new technologies can reliably operate in space. The goal is to eventually see such technologies incorporated into full-scale missions.

In the case of the Deep Space Atomic Clock, the aim is to enable deep space navigation systems that are more autonomous than what exists today. So spacecraft traveling beyond the Moon would have something similar to the GPS-based system that we use on Earth. To do that, the mission is focused on the clock's stability, or its ability to measure time consistently over long periods, while operating in the harsh space environment. The more stable a clock, the longer it can do its job without help from refrigerator-size atomic clocks on the ground.

"We're extremely proud of what this mission has done already, and we're very excited that NASA thinks it's worthwhile for us to keep working on it," said Todd Ely, Deep Space Atomic Clock principal investigator and project manager at JPL. "This has been an extremely challenging project, but we're motivated by the idea that this technology could fundamentally transform deep space navigation."

Better Clocks in Space

The atomic clocks found on GPS satellites are the reason your smart phone navigation tools work almost instantaneously. Your phone receives a series of signals from several satellites (at least four are required for positioning to work). The GPS software on your phone then uses the timing of those signals to determine your position as well as how fast you're moving and in what direction. The atomic clocks on GPS satellites ensure the timing is accurate. To do this, the clocks need to be able to measure time precisely - down to less than a billionth of a second.

A similar process is used for spacecraft flying beyond the Moon: Navigators bounce signals between the robotic explorer and atomic clocks on Earth to determine the spacecraft's trajectory. But there are limitations to this system due to the immense distances involved. For example, light signals can sometimes take up to 20 minutes to journey from Earth to Mars, so navigators can't make last-minute changes to a spacecraft's path.

Image above:  The DSAC Demonstration Unit (shown mounted on a plate for easy transportation). Image Credits:JPL, CC BY.

Moreover, the atomic clocks on Earth-orbiting GPS satellites aren't stable enough to be used for autonomous navigation on a spacecraft traveling in deep space. Over time, their measurement of the length of a second will change very subtly, but enough to impact navigation. In fact, GPS satellites receive daily or twice-daily updates from more stable ground-based atomic clocks to correct this drift, which would be impractical for spacecraft at more distant destinations. And unfortunately, flying those ground-based clocks also isn't an option, not only because they are so large but because they aren't engineered to operate in space.

Evolution to Revolution

The Deep Space Atomic Clock mission set out to bring the stability of a ground-based atomic clock to one small enough and tough enough to fly in space. The team has now demonstrated that the clock drifts by less than a nanosecond after four days, which adds up to less than one millionth of a second after 10 years and one full second every 10 million years. That might seem small, but an error of one full second could result in miscalculating a spacecraft's position by hundreds of thousands of miles.

So far, the mission team has learned a tremendous amount about how their novel atomic clock design fares in space, including how it responds to increased doses of radiation (which varies at different points in space) and how to get the best performance out of the remotely operated clock.

"In the long run, this technology might be revolutionary," said Robert Tjoelker, co-investigator for the Deep Space Atomic Clock at JPL. "Just getting our clock into space and operating well is a big first step. Further refinements towards even longer life and higher stability are already in the works."

With additional development and testing, team members noted, the technology could be used for space navigation by the mid-2020s.

The Deep Space Atomic Clock is hosted on a spacecraft provided by General Atomics Electromagnetic Systems of Englewood, Colorado. It is sponsored by the Space Technology Mission Directorate's Technology Demonstration Missions program located at NASA's Marshall Space Flight Center in Huntsville, Alabama, and NASA's Space Communications and Navigation (SCaN) program within NASA's Human Exploration and Operations Mission Directorate. JPL manages the project.

For more information on the Deep Space Atomic Clock, visit:

Related links:

Technology Demonstration Missions program:

Space Communications and Navigation (SCaN):

Animation (mentioned), Image (mentioned), Text, Credits: NASA/JPL/Calla Cofield.


Crew Focusing on Science Today as Spacewalk Nears

ISS - Expedition 63 Mission patch.

June 24, 2020

The Expedition 63 crew lightened up on spacewalk preparations today and focused its attention on a variety of research hardware today. The International Space Station residents also brushed up on their medical emergency skills while tending a pair of resupply ships.

Following a day of spacesuit fit checks, the three NASA astronauts aboard the orbiting lab split up on Wednesday to keep space science moving along. Commander Chris Cassidy started the day servicing a science freezer that stores biological samples for analysis. During the afternoon, Cassidy checked on samples for a physics study with commercial applications taking place in the Fluid Science Laboratory rack.

Image above: NASA astronaut Chris Cassidy is pictured during a spacewalk in July of 2013 when he was an Expedition 36 Flight Engineer. Image Credit: NASA.

Flight Engineer Doug Hurley stowed hardware from a space bubbles study that was exploring new methods to deliver oxygen to spacecraft and medicine to humans. His fellow crewmate, Bob Behnken, was troubleshooting the TangoLab-2 science facility before packing gear inside Japan’s HTV-9 resupply ship.

The duo ended the day conducting a medical emergency drill in space. Hurley and Behnken practiced cardiopulmonary resuscitation (CPR) techniques, located medical equipment and coordinated communications with mission controllers.

Image above: On June 21, 2020, as the International Space Station orbited over Kazakhstan and into China, an external high-definition camera captured this picture of the solar eclipse shadowing a portion of the Asian continent. The eclipse was visible across broad sections of Africa, the Middle East and Asia. In the left foreground, is the H-II Transfer Vehicle-9 from JAXA, the Japan Aerospace Exploration Agency. Image Credit: NASA.

Hurley also joined cosmonaut Ivan Vagner in the morning and reviewed their responsibilities to assist Cassidy and Behnken during Friday’s spacewalk. Hurley and Vagner will help the astronauts in and out of their spacesuits and monitor the spacewalk scheduled to start about 7:35 a.m. EDT. NASA TV begins its live broadcast at 6 a.m.


Vagner then partnered up with veteran cosmonaut Anatoly Ivanishin for cargo operations inside Russia’s Progress 74 cargo craft. Ivanishin spent the rest of the day working on Russian science experiments and life support maintenance.

Related links:

Expedition 63:

Commercial Crew Program:

Fluid Science Laboratory:

Space bubbles study:


HTV-9 resupply ship:

Progress 74 cargo craft:

Space Station Research and Technology:

International Space Station (ISS):

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

Best regards,

NASA’s TESS, Spitzer Missions Discover a World Orbiting a Unique Young Star

NASA - Transiting Exoplanet Survey Satellite (TESS) logo.

June 24, 2020

For more than a decade, astronomers have searched for planets orbiting AU Microscopii, a nearby star still surrounded by a disk of debris left over from its formation. Now scientists using data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and retired Spitzer Space Telescope report the discovery of a planet about as large as Neptune that circles the young star in just over a week.

NASA’s TESS, Spitzer Missions Discover World Orbiting Unique Young Star

Video above: NASA’s Transiting Exoplanet Survey Satellite (TESS) and retired Spitzer Space Telescope have found a young Neptune-size world orbiting AU Microscopii, a cool, nearby M-type dwarf star surrounded by a vast disk of debris. The discovery makes the system a touchstone for understanding how stars and planets form and evolve. Video Credits: NASA’s Goddard Space Flight Center.

The system, known as AU Mic for short, provides a one-of-a-kind laboratory for studying how planets and their atmospheres form, evolve and interact with their stars.

“AU Mic is a young, nearby M dwarf star. It’s surrounded by a vast debris disk in which moving clumps of dust have been tracked, and now, thanks to TESS and Spitzer, it has a planet with a direct size measurement,” said Bryson Cale, a doctoral student at George Mason University in Fairfax, Virginia. “There is no other known system that checks all of these important boxes.”

The new planet, AU Mic b, is described in a paper co-authored by Cale and led by his advisor Peter Plavchan, an assistant professor of physics and astronomy at George Mason. Their report was published on Wednesday, June 24, in the journal Nature.

AU Mic b is featured in a new NASA poster available in English and Spanish, part of a Galaxy of Horrors series. The fun but informative series resulted from a collaboration of scientists and artists and was produced by NASA's Exoplanet Exploration Program Office.

Image above: Located less than 32 light-years from Earth, AU Microscopii is among the youngest planetary systems ever observed by astronomers, and its star throws vicious temper tantrums. You’ve heard of the “terrible twos”? Well, AU Mic is in the midst of its terrible 22 … millions! NASA celebrates this discovery with a new poster — based on real science — in its popular Galaxy of Horrors series. Image Credits: NASA-JPL/Caltech.

The system is located 31.9 light-years away in the southern constellation Microscopium. It’s part of a nearby collection of stars called the Beta Pictoris Moving Group, which takes its name from a bigger, hotter A-type star that harbors two planets and is likewise surrounded by a debris disk.

Although the systems have the same age, their planets are markedly different. The planet AU Mic b almost hugs its star, completing an orbit every 8.5 days. It weighs less than 58 times Earth’s mass, placing it in the category of Neptune-like worlds. Beta Pictoris b and c, however, are both at least 50 times more massive than AU Mic b and take 21 and 3.3 years, respectively, to orbit their star. 

“We think AU Mic b formed far from the star and migrated inward to its current orbit, something that can happen as planets interact gravitationally with a gas disk or with other planets,” said co-author Thomas Barclay, an associate research scientist at the University of Maryland, Baltimore County and an associate project scientist for TESS at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “By contrast, Beta Pictoris b’s orbit doesn’t appear to have migrated much at all. The differences between these similarly aged systems can tell us a lot about how planets form and migrate.”

Detecting planets around stars like AU Mic poses a particular challenge. These stormy stars possess strong magnetic fields and can be covered with starspots — cooler, darker and highly magnetic regions akin to sunspots — that frequently erupt powerful stellar flares. Both the spots and their flares contribute to the star’s brightness changes.

In July and August 2018, when TESS was observing AU Mic, the star produced numerous flares, some of which were more powerful than the strongest flares ever recorded on the Sun. The team performed a detailed analysis to remove these effects from the TESS data.

Transiting Exoplanet Survey Satellite (TESS). Animation Credit: NASA

When a planet crosses in front of its star from our perspective, an event called a transit, its passage causes a distinct dip in the star’s brightness. TESS monitors large swaths of the sky, called sectors, for 27 days at a time. During this long stare, the mission’s cameras regularly capture snapshots that allow scientists to track changes in stellar brightness.

Regular dips in a star’s brightness signal the possibility of a transiting planet. Usually, it takes at least two observed transits to recognize a planet’s presence.

“As luck would have it, the second of three TESS transits occurred when the spacecraft was near its closest point to Earth. At such times, TESS is not observing because it is busy downlinking all of the stored data,” said co-author Diana Dragomir, a research assistant professor at the University of New Mexico in Albuquerque. “To fill the gap, our team was granted observing time on Spitzer, which caught two additional transits in 2019 and enabled us to confirm the orbital period of AU Mic b.”

Spitzer was a multipurpose infrared observatory operating from 2003 until its decommissioning on Jan. 30, 2020. The mission proved especially adept at detecting and studying exoplanets around cool stars. Spitzer returned the AU Mic observations during its final year.

Because the amount of light blocked by a transit depends on the planet’s size and orbital distance, the TESS and Spitzer transits provide a direct measure of AU Mic b’s size. Analysis of these measurements show that the planet is about 8% larger than Neptune.

Observations from instruments on ground-based telescopes provide upper limits for the planet’s mass. As a planet orbits, its gravity tugs on its host star, which moves slightly in response. Sensitive instruments on large telescopes can detect the star’s radial velocity, its motion to-and-fro along our line of sight. Combining observations from the W. M. Keck Observatory and NASA’s InfraRed Telescope Facility in Hawaii and the European Southern Observatory in Chile, the team concluded that AU Mic b has a mass smaller than 58 Earths.

This discovery shows the power of TESS to provide new insights into well-studied stars like AU Mic, where more planets may be waiting to be found.

Image above: This illustration depicts one interpretation of the planet AU Mic b and its young red dwarf host star. The system lies about 32 light-years away in the southern constellation Microsopium. Image Credits: NASA's Goddard Space Flight Center/Chris Smith (USRA).

“There is an additional candidate transit event seen in the TESS data, and TESS will hopefully revisit AU Mic later this year in its extended mission,” Plavchan said. “We are continuing to monitor the star with precise radial velocity measurements, so stay tuned.”

For decades, AU Mic has intrigued astronomers as a possible home for planets thanks to its proximity, youth and bright debris disk. Now that TESS and Spitzer have found one there, the story comes full circle. AU Mic is a touchstone system, a nearby laboratory for understanding the formation and evolution of stars and planets that will be studied for decades to come.

TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA's Goddard Space Flight Center. Additional partners include Northrop Grumman, based in Falls Church, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; MIT’s Lincoln Laboratory; and the Space Telescope Science Institute in Baltimore. More than a dozen universities, research institutes and observatories worldwide are participants in the mission.

NASA's Jet Propulsion Laboratory (JPL) in Southern California managed the Spitzer mission for the agency's Science Mission Directorate in Washington. Spitzer science data continue to be analyzed by the science community via the Spitzer data archive located at the Infrared Science Archive housed at IPAC at Caltech in Pasadena. Science operations were conducted at the Spitzer Science Center at Caltech. Spacecraft operations were based at Lockheed Martin Space in Littleton, Colorado. Caltech manages JPL for NASA.

Related links:


NASA poster:

Galaxy of Horrors:

University of New Mexico:

W. M. Keck Observatory:

NASA’s InfraRed Telescope Facility:

European Southern Observatory (ESO):

Spitzer Space Telescope:

TESS (Transiting Exoplanet Survey Satellite):

Images (mentioned), Animation (mentioned), Video (mentioned), Text, Credits: NASA/Francis Reddy/GSFC/Claire Andreoli.