Measuring Cosmic Rays At The Edge Of Space

Decade-long timelapse of M1: the Crab Nebula [OS][1920x1080]

NASA’s Webb Telescope to investigate mysterious brown dwarfs

Twinkle, twinkle, little star, how I wonder what you are. Astronomers are hopeful that the powerful infrared capability of NASA’s James Webb Space Telescope will resolve a puzzle as fundamental as stargazing itself – what IS that dim light in the sky? Brown dwarfs muddy a clear distinction between stars and planets, throwing established understanding of those bodies, and theories of their formation, into question.

Several research teams will use Webb to explore the mysterious nature of brown dwarfs, looking for insight into both star formation and exoplanet atmospheres, and the hazy territory in-between where the brown dwarf itself exists. Previous work with Hubble, Spitzer, and ALMA have shown that brown dwarfs can be up to 70 times more massive than gas giants like Jupiter, yet they do not have enough mass for their cores to burn nuclear fuel and radiate starlight.

Though brown dwarfs were theorized in the 1960s and confirmed in 1995, there is not an accepted explanation of how they form: like a star, by the contraction of gas, or like a planet, by the accretion of material in a protoplanetary disk? Some have a companion relationship with a star, while others drift alone in space.

At the Université de Montréal, Étienne Artigau leads a team that will use Webb to study a specific brown dwarf, labeled SIMP0136. It is a low-mass, young, isolated brown dwarf – one of the closest to our Sun – all of which make it fascinating for study, as it has many features of a planet without being too close to the blinding light of a star.

SIMP0136 was the object of a past scientific breakthrough by Artigau and his team, when they found evidence suggesting it has a cloudy atmosphere. He and his colleagues will use Webb’s spectroscopic instruments to learn more about the chemical elements and compounds in those clouds.

“Very accurate spectroscopic measurements are challenging to obtain from the ground in the infrared due to variable absorption in our own atmosphere, hence the need for space-based infrared observation. Also, Webb allows us to probe features, such as water absorption, that are inaccessible from the ground at this level of precision,” Artigau explains.

These observations could lay groundwork for future exoplanet exploration with Webb, including which worlds could support life. Webb’s infrared instruments will be capable of detecting the types of molecules in the atmospheres of exoplanets by seeing which elements are absorbing light as the planet passes in front of its star, a scientific technique known as transit spectroscopy.

“The brown dwarf SIMP0136 has the same temperature as various planets that will be observed in transit spectroscopy with Webb, and clouds are known to affect this type of measurement; our observations will help us better understand cloud decks in brown dwarfs and planet atmospheres in general,” Artigau says.

The search for low-mass, isolated brown dwarfs was one of the early science goals put forward for the Webb telescope in the 1990s, says astronomer Aleks Scholz of the University of St. Andrews.

Brown dwarfs have a lower mass than stars and do not “shine” but merely emit the dim afterglow of their birth, and so they are best seen in infrared light, which is why Webb will be such a valuable tool in this research.

Scholz, who also leads the Substellar Objects in Nearby Young Clusters (SONYC) project, will use Webb’s Near-Infrared Imager and Slitless Spectrograph (NIRISS) to study NGC 1333 in the constellation of Perseus. NGC 1333 is a stellar nursery that has also been found to harbor an unusually high number of brown dwarfs, some of them at the very low end of the mass range for such objects - in other words, not much heavier than Jupiter.

“In more than a decade of searching, our team has found it is very difficult to locate brown dwarfs that are less than five Jupiter-masses - the mass where star and planet formation overlap. That is a job for the Webb telescope,” Scholz says. “It has been a long wait for Webb, but we are very excited to get an opportunity to break new ground and potentially discover an entirely new type of planets, unbound, roaming the Galaxy like stars.”

Both of the projects led by Scholz and Artigau are making use of Guaranteed Time Observations (GTOs), observing time on the telescope that is granted to astronomers who have worked for years to prepare Webb’s scientific operations.

TOP IMAGE….Artist’s conception of a brown dwarf, featuring the cloudy atmosphere of a planet and the residual light of an almost-star. Credit NASA/ESA/JPL

LOWER IMAGE….Stellar cluster NGC 1333 is home to a large number of brown dwarfs. Astronomers will use Webb’s powerful infrared instruments to learn more about these dim cousins to the cluster’s bright newborn stars. Credit NASA/CXC/JPL

HH34 - Subaru Data + colors from DSS (2) Credit: Roberto colombari

Argyre Impact basin

Credits on photo

Sensor to monitor orbital debris outside space station

The International Space Station isn’t the only spacecraft orbiting the Earth. In fact, it is accompanied by the Hubble Space Telescope, satellites within the Earth Observing System, and more than 1,000 other operational spacecraft and CubeSats. In addition to spacecraft, bits of orbital debris - human-made objects no longer serving a purpose in space - are also in orbit.

With an estimated more than 100 million pieces of orbital debris measuring smaller than one centimeter currently in Earth’s orbit, they can be too small to track, but many are large enough to cause damage to operational spacecraft.

The space station has orbital debris shields in place to protect from debris less than 1.5 centimeters in size. Larger debris pieces are tracked by ground control, and if needed, the space station thrusters can be used to safely move station away from the debris.

The Space Debris Sensor (SDS) will monitor the small debris environment around the space station for two to three years, recording instances of debris between the sizes of .05mm to.5mm. Objects larger than 3 mm are monitored from the ground. It will launch to station in the trunk of a SpaceX Dragon during a resupply mission no earlier than Dec. 12.

Orbital debris as small as .3mm may pose a danger to human spaceflight and robotic missions.

“Debris this small has the potential to damage exposed thermal protection systems, spacesuits, windows and unshielded sensitive equipment,” said Joseph Hamilton, the project’s principal investigator. “On the space station, it can create sharp edges on handholds along the path of spacewalkers, which can also cause damage to the suits.”

Once it is mounted on the exterior of the Columbus module aboard the space station, the sensor will provide near-real-time impact detection and recording capabilities.

Using a three-layered acoustic system, the SDS characterizes the size, speed, direction and density of these small particles. The first two layers are meant to be penetrated by the debris. This dual-film system provides the time, location and speed of the debris, while the final layer - a Lexan backstop - provides the density of the object.

The first and second layers of the SDS are identical, equipped with acoustic sensors and .075mm wide resistive lines. If a piece of debris damages the first layer, it cuts through one or more of the resistive lines before impacting and going through the second layer. Finally, the debris hits the backstop plate.

Although the backstop won’t be used to return any of the collected samples, combined with the first two layers, it gives researchers valuable data about the debris that impacts the SDS while in orbit.

“The backstop has sensors to measure how hard it is hit to estimate the kinetic energy of the impacting object,” said Hamilton. “By combining this with velocity and size measurements from the first two layers, we hope to calculate the density of the object.”

The acoustic sensors within the first two layers measure the impact time and location using a simple triangulation algorithm. Finally, combining impact timing and location data provides impact and direction measurements of the debris.

Data gathered during the SDS investigation will help researchers map the entire orbital debris population and plan future sensors beyond the space station and low-Earth orbit, where the risk of damage from orbital debris is even higher to spacecraft.

“The orbital debris environment is constantly changing and needs to be continually monitored,” said Hamilton. “While the upper atmosphere causes debris in low orbits to decay, new launches and new events in space will add to the population.”