Nature, Published online: 01 July 2020; doi:10.1038/s41586-020-2421-7

Observations of TOI-849b reveal a radius smaller than Neptune’s but a large mass of about 40 Earth masses, indicating that the planet is the remnant core of a gas giant.

Astronomers have found a previously unseen type of object circling a distant star.

Using the European Southern Observatory’s Very Large Telescope (VLT), astronomers have discovered the absence of an unstable massive star in a dwarf galaxy. Scientists think this could indicate that the star became less bright and partially obscured by dust. An alternative explanation is that the star collapsed into a black hole without producing a supernova. “If true,” says team leader and PhD student Andrew Allan of Trinity College Dublin, Ireland, “this would be the first direct detection of such a monster star ending its life in this manner.”

PROJECT

Broadband Mirror Coatings for Future NASA Observatory

SNAPSHOT

A team at GSFC is investigating techniques for creating highly reflective aluminum mirrors sensitive to the far-ultraviolet in addition to the infrared, optical, and visible wavelengths.

Left: Engineers in the GSFC coating lab. Left to right: Javier del Hoyo (GSFC), Emily Witt (U. of CO), and Nicholas Nell (U. of CO). Right: A coated primary mirror after it was taken from the chamber on the left. This mirror will be used on the Suborbital Imaging Spectrograph for Transition region Irradiance from Nearby Exoplanet (SISTINE) payload—a sounding rocket mission that will advance the Technology Readiness Level of these new mirror coatings (PI: Kevin France U. of CO)

The more reflective a telescope mirror is at far-ultraviolet (FUV) wavelengths, the better the images it can collect. Scientists and engineers at NASA Goddard Space Flight Center (GSFC) are able to produce telescope mirror coatings with the highest reflectance ever reported in the far-ultraviolet (FUV) spectral range. Now, they have developed a new type of mirror coating envisioned for use on the mirrors of the proposed successors to the James Webb Space Telescope—the Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) and the Habitable Exoplanet Imaging Mission (HabEx). These proposed missions would tackle a broad range of astrophysics studies, from the epoch of reionization, through galaxy formation and evolution, to star and planet formation.

The FUV spectral region is relevant to many aspects of NASA’s Cosmic Origin (COR) program. However, performing measurements in this wavelength range has historically been quite difficult for a number of technical reasons including poor mirror reflectance in the FUV range. Consequently, the universe has only been explored by a handful of NASA astronomy missions in this spectral range. The Far Ultraviolet Spectroscopic Explorer (FUSE) observing program was the most extensive by far, but it was limited by modest effective mirror area (20 cm2 below 100 nm and 55 cm2 above 102 nm) and modest spectral resolution (R~20,000). The average reflectivity of the mirror coatings on FUSE was 60% for the Aluminum + Lithium Fluoride (Al+LiF) coating and 30% for the Silicon carbide (SiC) coating.

Improved reflectivity in itself would bring enormous gains in throughput, and the benefits of more capable optical designs enabled by higher reflectivity would increase sensitivity. Aluminum is the metal with the broadest spectral coverage. In fact, pure aluminum mirrors are highly reflective over the spectral range proposed for LUVOIR and HabEx observations (90 to 5,000 nm). However, aluminum needs to be protected from naturally occurring oxides with a thin coating of transparent material.

Unfortunately, no one has developed a coating that effectively protects and maintains a mirror’s reflectivity in the 90- to 130-nm range, also known as the Lyman Ultraviolet range, a spectral regime rich in astronomical targets and spectral lines, including potentially habitable planets beyond our solar system. The low reflectivity of coatings in this range is one of the biggest constraints in FUV telescope and spectrograph design.

A team funded by NASA’s Science Mission Directorate and led by Manuel Quijada at GSFC is testing several new techniques and materials for creating and applying protective coatings that will produce highly reflective aluminum mirrors sensitive to the infrared, visual, and far-ultraviolet wavelengths.

Under several research grants from the Astrophysics Division’s Astrophysics Research and Analysis (APRA) program, Quijada’s team is planning to use xenon difluoride to apply a thin layer of aluminum trifluoride to an aluminum sample. Previous studies indicated that the use of xenon difluoride creates fluorine ions that tightly bind to the aluminum surface, preventing the oxidation that decreases reflectivity. The team is also investigating the use of two other thin-film deposition techniques — Ion-Assisted Physical Vapor Deposition and Atomic Layer Deposition — to apply thin films of aluminum trifluoride, which is environmentally stable compared with other coatings.

The LPPS is a facility unique to NRL. Based on e-beams, the LPPS allows the generation of very large area (>1m2), highly uniform, low temperature plasmas.

Quijada’s team is also working on a third approach, based on a partnership between GSFC and the Naval Research Laboratory (NRL) through a Strategic Astrophysics Technology (SAT) grant. This SAT project is aiming to develop aluminum-based broadband optical coatings using the NRL Large Area Plasma Processing System (LAPPS). This project is leveraging the improvements in FUV reflectivity that have been developed at GSFC involving aluminum test samples that are protected with a single Aluminum Fluoride (AlF3) dielectric overcoat. The goal is to produce large (1+ meter class) mirrors using the LAPPS reactor at NRL and their patented e-beam plasma system. The ultimate plan is to remove oxide from bare aluminum surfaces and passivate the surface (i.e., make it less reactive) using an aluminum tri-fluoride (AlF3) layer.

Reflectivity from: (a) unoxidized pure Al (black dashed line); (b) a coating generated by the fluorination process at NRL (blue solid line); (c) the HST primary mirror before launch (red dashed line).

The figure at left indicates that using this newly reconfigured LAPPS reactor yielded coatings with FUV reflectivity greater than 50% at 106 nm and reflectivity approximately equal to 90% at 120 nm (blue line) compared to the reflectivity of the Hubble Space Telescope (HST) mirrors prior to launch (red dashed line). Note that the coating used in the HST mirrors consisted of Al protected with magnesium difluoride (MgF2).

Preliminary studies on the passivation of thin aluminum films have already demonstrated the feasibility of the plasma process to effectively fluorinate the surface of small aluminum mirror samples without using highly corrosive hydrofluoric (HF) acid. The team is working to develop a process to treat an aluminum surface on a scale as large as 1 meter (m) in diameter. Successful completion of this effort would provide enhanced reflectors in the FUV spectral region (90-180nm), which would ultimately enable new scientific imaging capabilities for the LUVOIR and the HabEx missions.

PROJECT LEAD

Dr. Manuel A. Quijada, NASA Goddard Space Flight Center

SPONSORING ORGANIZATION

Astrophysics Research and Analysis (APRA) and Strategic Astrophysics Technology (SAT) Programs

Read more Technology Highlights

Master Image: 

Portal origin URL: NASA Spacecraft Helps Identify Solar Radiation Patterns That Expose the MoonPortal origin nid: 461859Published: Tuesday, June 30, 2020 - 10:00Featured (stick to top of list): noPortal text teaser: NASA mission helps scientists identify when the Moon is unprotected from charged particles in space.Portal image: Moon outside Earth's magnetotail

A huge star has disappeared - did it become a black hole?

An analysis of nine years’ worth of data from NASA’s Fermi craft opens the possibility of studying dark-matter particle models with gamma rays, as Edwin Cartlidge reports

Some of the ice on Mercury is created by chemical reactions triggered by the planet’s extreme daytime heat. That is according to Brant Jones and Thomas Orlando from the Georgia Institute of Technology and ASA’s Menelaos Sarantos

Study says surge in volcanic activity could not have caused Cretaceous/Paleogene extinction event

A 66m-year-old murder mystery has finally been solved, researchers say, revealing an enormous asteroid struck the killer blow for the dinosaurs.

The Cretaceous/Paleogene extinction event resulted in about 75% of plants and animals – including non-avian dinosaurs – being wiped out. But the driving cause of the catastrophe has been a topic of hot debate.

Continue reading...

Astronomers say big cool patches on the Betelgeuse star likely drove its surprise dimming last year.

Nature, Published online: 25 June 2020; doi:10.1038/d41586-020-01905-5

A nearby red dwarf doesn’t emit flares or harmful radiation — so its planets might have atmospheres.

Portal origin URL: NASA’s TESS, Spitzer Missions Discover a World Orbiting a Unique Young StarPortal origin nid: 462159Published: Wednesday, June 24, 2020 - 11:00Featured (stick to top of list): noPortal text teaser: Astronomers using data from NASA's TESS and retired Spitzer Space Telescope have discovered a planet as large as Neptune circling the young star orbiting AU Microscopii.Portal image: Illustration of AU Mic b and its red dwarf host star

Eyebrow: Citizen Science NewsBody: 

Disk Detective is back! Disk Detective is the NASA citizen science project that previously discovered “Peter Pan” disks as well discovered the youngest nearby disk around a brown dwarf. The project is relaunching with a new batch of 150,000 stars to analyze and looking to the public for help.

Link: Learn More

Eyebrow: Citizen Science NewsBody: 

On June 15, 2020, a citizen scientist spotted a never-before-seen comet in data from the Solar and Heliospheric Observatory, or SOHO — the 4,000th comet discovery in the spacecraft’s 25-year history.

Link: Learn More

The Sun’s magnetic field is generated by subsurface motions of the convecting plasma. The latitude at which the magnetic field emerges through the solar surface (as sunspots) drifts toward the equator over the course of the 11-year solar cycle. We use helioseismology to infer the meridional flow (in the latitudinal and radial directions) over two solar cycles covering 1996–2019. Two data sources are used, which agree during their overlap period of 2001–2011. The time-averaged meridional flow is shown to be a single cell in each hemisphere, carrying plasma toward the equator at the base of the convection zone with a speed of ~4 meters per second at 45° latitude. Our results support the flux-transport dynamo model, which explains the drift of sunspot-emergence latitudes through the meridional flow.

Mary Jackson was among the African-American women whose story was told in the film Hidden Figures.