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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

“Cosmic Neutrinos Can be Absorbed by Planet Earth”

 Scientists using the IceCube Observatory located near the South Pole have discovered that neutrinos can be absorbed by our Planet Earth. With almost no mass and no charge, these particles rarely interact with matter. Yet tens of trillions of neutrinos pass through our bodies every second.  Previous theories predicted that at high energies, neutrinos can be expected to interact with matter and be absorbed by the Earth instead of passing through the planet.  “We knew that lower-energy neutrinos pass through just about anything, but although we had expected higher-energy neutrinos to be different, no previous experiments had been able to demonstrate convincingly that higher-energy neutrinos could be stopped by anything,” said Penn State Professor Doug Cowen. “However, the neutrino does have a tiny probability to interact, and this probability increases with energy. That probability is what scientists call the neutrino cross section.”  The new measurements recorded by IceCube determined the neutrino cross section energies to be about 6.3 TeV and 980 TeV, energy levels significantly higher than previously measured.

Read more about this fascinating story at: http://www.newsoftheuniverse.com/2017/11/cosmic-neutrinos-can-be-absorbed-by.html

New observations and modeling by a NASA-led team can help scientists understand a fast and furious jet stream high above Jupiter’s equator. This jet has a counterpart on Earth that seems to influence the transport of ozone, water vapor and pollution in the upper atmosphere, as well as the production of hurricanes. Credits: NASA’s Goddard Space Flight Center/Scientific Visualization Studio/Dan Gallagher

(NASA)  NASA Solves How a Jupiter Jet Stream Shifts into Reverse

Speeding through the atmosphere high above Jupiter’s equator is an east–west jet stream that reverses course on a schedule almost as predictable as a Tokyo train’s. Now, a NASA-led team has identified which type of wave forces this jet to change direction.

Similar equatorial jet streams have been identified on Saturn and on Earth, where a rare disruption of the usual wind pattern complicated weather forecasts in early 2016. The new study combines modeling of Jupiter’s atmosphere with detailed observations made over the course of five years from NASA’s Infrared Telescope Facility, or IRTF, in Hawai’i. The findings could help scientists better understand the dynamic atmosphere of Jupiter and other planets, including those beyond our solar system.

Earth’s equatorial jet stream was discovered after observers saw debris from the 1883 eruption of the Krakatoa volcano being carried by a westward wind in the stratosphere, the region of the atmosphere where modern airplanes achieve cruising altitude. Later, weather balloons documented an eastward wind in the stratosphere. Scientists eventually determined that these winds reversed course regularly and that both cases were part of the same phenomenon.

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