NASA Astronomy Picture of the Day

Feb 28, 2024

Shades of Night

How does the sky turn dark at night? In stages, and with different characteristic colors rising from the horizon. The featured image shows, left to right, increasingly late twilight times after sunset in 20 different vertical bands. The picture was taken last month in Syracuse, Sicily, Italy, in the direction opposite the Sun. On the far left is the pre-sunset upper sky. Toward the right, prominent bands include the Belt of Venus, the Blue Band, the Horizon Band, and the Red Band. As the dark shadow of the Earth rises, the colors in these bands are caused by direct sunlight reflecting from air and aerosols in the Earth's atmosphere, multiple reflections sometimes involving a reddened sunset, and refraction. In practice, these bands can be diffuse and hard to discern, and their colors can depend on colors near the setting Sun. Finally, the Sun completely sets and the sky becomes dark. Don't despair – the whole thing will happen in reverse when the Sun rises again in the morning.

https://apod.nasa.gov/apod/astropix.html?

Listen to the Universe: New NASA Sonifications and Documentary

FEB 28, 2024

Three new sonifications of images from NASA’s Chandra X-ray Observatory and other telescopes have been released in conjunction with a new documentary about the project that makes its debut on the NASA+ streaming platform.

Sonification is the process of translating data into sounds. In the case of Chandra and other telescopes, scientific data are collected from space as digital signals that are commonly turned into visual imagery. The sonification project takes these data through another step of mapping the information into sound.

The three new sonifications feature different objects observed by NASA telescopes.

The first is MSH 11-52, a supernova remnant blowing a spectacular cloud of energized particles resembling the shape of a human hand, seen in data from Chandra, NASA’s Imaging X-ray Polarimetry Explorer (IXPE), and ground-based optical data.

M74 is a spiral galaxy like our Milky Way and this sonification combines data taken with NASA’s James Webb and Hubble Space Telescopes as well as X-rays from Chandra.

The third object in this new sonification trio is nicknamed the Jellyfish Nebula, also known as IC 443. These data include X-rays from Chandra and the now-retired German ROSAT mission as well as radio data from NSF’s Very Large Array and optical data from the Digitized Sky Survey.

The new documentary, “Listen to the Universe,” now available on NASA+ (https://plus.nasa.gov/) explores how these sonifications are created and profiles the team that makes them possible.

Started in 2020, the NASA sonification project built off of other Chandra projects aimed at reaching blind and visually-impaired audiences. It has since shown to be meaningful to that community but also impacts much wider audiences, finding listeners through traditional and social media around the world.

“We are so excited to partner with NASA+, along with her collaborators at SYSTEMS Sounds, to help tell the story about NASA’s sonification project,” said Kimberly Arcand, Chandra’s Visualization and Emerging Technology Scientist, who leads the sonification efforts. “It’s wonderful to see how this project has grown and reached so many people.”

NASA+ is the agency’s new streaming platform, delivering video and other content about NASA to the public whenever and wherever they want to access it. The on-demand streaming service is available to download on most major platforms via the NASA App on iOS and Android mobile and tablet devices, as well as streaming media players Roku and Apple TV.

“Sonifications add a new dimension to stunning space imagery, and make those images accessible to the blind and low-vision community for the first time,” said Liz Landau, who leads multimedia efforts for NASA’s Astrophysics Division at NASA Headquarters, Washington, and oversaw production of the “Listen to the Universe” documentary. “I was honored to help tell the story of how Dr. Arcand and the System Sounds team make these unique sonic experiences and the broad impact those sonifications have had.”

More information about the NASA sonification project through Chandra, which is made in partnership with NASA’s Universe of Learning, can be found at https://chandra.si.edu/sound/

https://www.nasa.gov/missions/chandra/listen-to-the-universe-new-nasa-sonifications-and-documentary/

View Nova Explosion, ‘New’ Star in Northern Crown

February 27, 2024

A star system, located 3,000 light-years away from Earth, is predicted to become visible to the unaided eye soon. This could be a once-in-a-lifetime viewing opportunity as the nova outburst only occurs about every 80 years. T Coronae Borealis, or T CrB, last exploded in 1946 and astronomers believe it will do so again between February and September 2024.

The star system, normally magnitude +10, which is far too dim to see with the unaided eye, will jump to magnitude +2 during the event. This will be of similar brightness to the North Star, Polaris.

Once its brightness peaks, it should be visible to the unaided eye for several days and just over a week with binoculars before it dims again, possibly for another 80 years.

As we wait for the nova, become familiar with the constellation Corona Borealis, or the Northern Crown — a small, semicircular arc near Bootes and Hercules. This is where the outburst will appear as a “new” bright star.

This recurring nova is only one of five in our galaxy. This happens because T CrB is a binary system with a white dwarf and red giant. The stars are close enough that as the red giant becomes unstable from its increasing temperature and pressure and begins ejecting its outer layers, the white dwarf collects that matter onto its surface. The shallow dense atmosphere of the white dwarf eventually heats enough to cause a runaway thermonuclear reaction – which produces the nova we see from Earth.

https://blogs.nasa.gov/Watch_the_Skies/2024/02/27/view-nova-explosion-new-star-in-northern-crown/

https://science.nasa.gov/science-research/science-enabling-technology/the-cute-mission-innovative-design-enablesobservations-of-extreme-exoplanets-from-a-smallpackage/

The CUTE Mission: Innovative Design Enables Observations of Extreme Exoplanets from a Small Package

FEB 27, 2024

Of the approximately 5,500 exoplanets discovered to date, many have been found to orbit very close to their parent stars. These close-in planets provide a unique opportunity to observe in detail the phenomena critical to the development and evolution of our own solar system, including atmospheric mass loss and interactions with the host star. NASA’s Colorado Ultraviolet Transit Experiment (CUTE) mission, launched in September 2021, employed a new design that enabled exploration of these processes using a small spacecraft for the first time. CUTE provides unique spectral diagnostics that trace the escaping atmospheres of close-in, ultra-hot, giant planets. In addition, CUTE’s dedicated mission architecture enables the survey duration required to characterize atmospheric structure and variability on these worlds.

Atmospheric escape is a fundamental process that affects the structure, composition, and evolution of many planets. It has operated on all of the terrestrial planets in our solar system and likely drives the demographics of the short-period planet population characterized by NASA’s Kepler mission. In fact, atmospheric escape ultimately may be the determining factor when predicting the habitability of temperate, terrestrial exoplanets. Escaping exoplanet atmospheres were first observed in the hydrogen Lyman-alpha line (121nm) in 2003. However, contamination by neutral hydrogen in both the intervening interstellar medium and Earth’s upper atmosphere makes obtaining high-quality Lyman-alpha transit measurements for most exoplanets very challenging. By contrast, a host star’s near-ultraviolet (NUV; 250 – 350 nm) flux is two to three orders of magnitude higher than Lyman-alpha, and transit light curves can be measured against a smoother stellar surface intensity distribution.

This knowledge motivated a team led by Dr. Kevin France at the University of Colorado Laboratory for Atmospheric and Space Physics to design the CUTE mission (Fig 2). The team proposed the CUTE concept to NASA through the ROSES/Astrophysics Research and Analysis (APRA) Program in February 2016 and NASA funded the project in July 2017. The CUTE instrument pioneered use of two technologies on a small space mission: a novel, rectangular Cassegrain telescope (20cm × 8cm primary mirror) and a miniature, low-resolution spectrograph operating from approximately 250 – 330 nm. The rectangular telescope was fabricated to accommodate the unique instrument volume of the 6U CubeSat form factor, an adaptation that delivers approximately three times the collecting area of a traditional, circular aperture telescope. The compact spectrograph meets the spectral resolution requirements of the mission while using scaled down component technology adapted from the Hubble Space Telescope.

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This novel instrument design enables CUTE to measure NUV with similar precision as larger missions even in the more challenging thermal and pointing environment experienced by a CubeSat. In addition, the CUTE instrument’s NUV bandpass enables it to measure iron and magnesium ions from highly extended atmospheric layers that ground-based instruments cannot access. The CUTE science instrument is incorporated into a 6U Blue Canyon Technologies spacecraft bus that provides power, command and data handling, attitude control, and communications. This CubeSat platform enables CUTE to observe numerous transits of a given planet. The spectrogram from the CUTE instrument is recorded on a UV-optimized commercial off-the-shelf charge-coupled device (CCD), onboard data processing is performed, and data products are relayed to a ground station at the University of Colorado.

CUTE was launched as a secondary payload on NASA’s LANDSAT-9 mission on September 27, 2021 into a Sun-synchronous orbit with a 560 km apogee. CUTE deployed from the payload dispenser (Fig 3) approximately two hours after launch and then deployed its solar arrays. Spacecraft beacon signals were identified by the amateur radio community on the first orbit and communications were established with the ground station at the University of Colorado the following day. On-orbit commissioning of the spacecraft and instrument concluded in February 2022 and the mission has been conducting science operations since that time.

As of February 2024, CUTE is actively acquiring science and calibration data (Fig 4), and has observed between 6 and 11 transits of seven different exoplanetary systems. Data downlink efficiency is the primary factor limiting the number of targets observed over the course of the mission. CUTE light curves and transit spectroscopy are revealing extended NUV atmospheres on some planets (Fig 5) and potential time variability in the atmospheric transmission spectra of others. For example, observations of the ultra-hot exoplanet, Jupiter WASP-189b, indicate a highly extended atmosphere. Magnesium ions are observed to be gravitationally unbound from the planet, which is evidence for active escape of heavy elements in this system. CUTE data are being archived by the NASA Exoplanet Science Institute (NExScI).

CUTE successfully demonstrated the use of a non-circular telescope and miniature spectrograph design for small space missions, an approach that has been subsequently adopted by several NASA and international mission designs, including NASA’s new Monitoring Activity from Nearby sTars with uv Imaging and Spectroscopy (MANTIS) mission. CUTE’s demonstration of sub-1% NUV precision has shown that the precision achieved by large UV astronomy missions can also be achieved by a CubeSat. In addition, student training and early-career mentorship have been key ingredients to CUTE’s mission success. So far, over 20 early career students and professionals have trained and participated in CUTE activities—ranging from science to engineering to operations.

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Russian satellite narrowly avoids collision with US spacecraft, and NASA could do nothing to stop it

Feb 28, 2024

An active NASA spacecraft has survived a near-miss with a defunct Russian satellite in low Earth orbit.

NASA's Thermosphere Ionosphere Mesosphere Energetics and Dynamics (TIMED) mission spacecraft and Russia's Cosmos 2221 satellite were due to closely pass each other at around 1:30 am EST on Feb. 28, at an altitude of about 373 miles (600 kilometers), according to a statement released by NASA just an hour before the near-miss.

Had the two non-maneuverable satellites collided, it wouldn't have just doomed NASA's satellite — which monitors the effects of the sun on the Earth's atmosphere — but could have also potentially started a catastrophic collision cascade with other objects in orbit.

A collision could result in significant debris generation," NASA and the Department of Defense representatives wrote in the statement.

The potential scenario of a cascade of satellite debris in low Earth orbit (the area of space within 1,200 miles or 2,000 km of Earth) is called Kessler syndrome, and was popularly depicted in the 2013 film "Gravity."

Related: 5,000-pound European satellite burns up over Pacific Ocean after 30 years in orbit

Although a cascade of this kind has yet to happen, scientists are increasingly concerned that the growing number of satellites and space junk is making it more likely. Currently, the Department of Defense tracks the 30,000 largest debris pieces, but there are many more that are too small to be followed, according to NASA.

These smaller chunks are a threat both to satellites and the International Space Station, which in 2022 had to perform evasive maneuvers to dodge the junk generated by a Russian anti-satellite test.

Scientists are currently working on ways to fix Earth's space junk problem. For example, a team of Australian scientists proposed removing smaller junk from space by blasting it with a laser, while the European Space Agency (ESA) plans to launch a four-armed robot to grab individual items of space junk.

The ESA is hoping to use the mission, scheduled for 2025, as a test for a much wider-reaching operation performed by a fleet of robot cleaners.

ESA's director general Jan Wörner has also called for new rules to make companies and agencies that launch satellites responsible for tidying up their litter.

https://www.livescience.com/space/russian-satellite-narrowly-avoids-collision-with-us-spacecraft-and-nasa-could-do-nothing-to-stop-it