NASA Astronomy Picture of the Day
April 24, 2024
Dragon's Egg Bipolar Emission Nebula
How did a star form this beautiful nebula? In the middle of emission nebula NGC 6164 is an unusually massive star. The central star has been compared to an oyster's pearl and an egg protected by the mythical sky dragons of Ara. The star, visible in the center of the featured image and catalogued as HD 148937, is so hot that the ultraviolet light it emits heats up gas that surrounds it. That gas was likely thrown off from the star previously, possibly the result of a gravitational interaction with a looping stellar companion. Expelled material might have been channeled by the magnetic field of the massive star, in all creating the symmetric shape of the bipolar nebula. NGC 6164 spans about four light years and is located about 3,600 light years away toward the southern constellation Norma.
https://apod.nasa.gov/apod/astropix.html?
New NASA technology captures images of ancient lake reemergence from space: 'Developing one of the most detailed and comprehensive views of the planet'
April 23, 2024 at 7:00 PM PDT
A satellite launched in 2022 is providing images and unparalleled data about an ephemeral lake.
The NASA-backed initiative highlights a partnership between the United States and France that can "fill the data gap" with the Surface Water and Ocean Topography satellite, Phys.org reported.
In August, when record rain began falling in California to reverse a yearslong drought, a temporary lake, known as Lake Manly, reemerged in Death Valley. SWOT has been photographing the area and measuring water depths.
In the ice age, Badwater Basin featured a 700-foot-deep lake, which has been extinct for 10,000 years and is now salt flats. It is the lowest point in North America at 282 feet below sea level.
"This is a really cool example of how SWOT can track how unique lake systems work," said Tamlin Pavelsky, NASA freshwater science lead for SWOT.
Lake Manly, which has reappeared before, expanded to about six miles long and three miles wide after more record rain in February. Over weeks of measurement, its depth ranged from less than 1.5 feet to about three feet, according to researchers who used water level data from SWOT and land elevation information from the U.S. Geological Survey, per Phys.org.
SWOT's greatest strength, however, may be in the maps it is building of Earth's waters. Thanks to the Ka-band Radar Interferometer — a boom with two antennas separated by 33 feet — the satellite sends radar pulses toward surface water, "developing one of the most detailed and comprehensive views of the planet's oceans and freshwater lakes and rivers."
This is especially important as rising temperatures and water rights issues create problems for lakes all over the world, including some in the vicinity of Death Valley. The concern is that, despite temporary relief, these critical resources may never recover if they dry up. On the other hand, wet climates may only get more rainfall.
"Strong winds are enough to move the freshwater body a couple of miles, as happened from Feb. 29 to March 2," Phys.org reported. "Since there isn't typically water in Badwater Basin, researchers don't have permanent instruments in place for studying water in this area. SWOT can fill the data gap for when places like this, and others around the world, become inundated."
Phys.org noted that the data is also being used to help scientists and engineers understand how the satellite works.
"We've never flown a Ka-band radar like the KaRIn instrument on a satellite before," Pavelsky said.
https://www.yahoo.com/tech/nasa-technology-captures-images-ancient-020000894.html
NASA’s CloudSat Ends Mission Peering Into the Heart of Clouds
APR 23, 2024
Over the course of nearly two decades, its powerful radar provided never-before-seen details of clouds and helped advance global weather and climate predictions.
CloudSat, a NASA mission that peered into hurricanes, tallied global snowfall rates, and achieved other weather and climate firsts, has ended its operations. Originally proposed as a 22-month mission, the spacecraft was recently decommissioned after almost 18 years observing the vertical structure and ice/water content of clouds.
As planned, the spacecraft — having reached the end of its lifespan and no longer able to make regular observations — was lowered into an orbit last month that will result in its eventual disintegration in the atmosphere.
When launched in 2006, the mission’s Cloud Profiling Radar was the first-ever 94 GHz wavelength (W-band) radar to fly in space. A thousand times more sensitive than typical ground-based weather radars, it yielded a new vision of clouds — not as flat images on a screen but as 3D slices of atmosphere bristling with ice and rain.
For the first time, scientists could observe clouds and precipitation together, said Graeme Stephens, the mission’s principal investigator at NASA’s Jet Propulsion Laboratory in Southern California. “Without clouds, humans wouldn’t exist, because they provide the freshwater that life as we know it requires,” he said. “We sometimes refer to them as clever little devils because of their confounding properties. Clouds have been an enigma in terms of predicting climate change.”
Clouds have long held many secrets. Before CloudSat, we didn’t know how often clouds produce rain and snow on a global basis. Since its launch, we’ve also come a long way in understanding how clouds are able to cool and heat the atmosphere and surface, as well as how they can cause aircraft icing.
CloudSat data has informed thousands of research publications and continues to help scientists make key discoveries, including how much ice and water clouds contain globally and how, by trapping heat in the atmosphere, clouds accelerate the melting of ice in Greenland and at the poles.
Weathering the Storm
Over the years, CloudSat flew over powerful storm systems with names like Maria, Harvey, and Sandy, peeking beneath their swirling canopies of cirrus clouds. Its Cloud Profiling Radar excelled at penetrating cloud layers to help scientists explore how and why tropical cyclones intensify.
Across the life of CloudSat, several potentially mission-ending issues occurred related to the spacecraft’s battery and to the reaction wheels used to control the satellite’s orientation. The CloudSat team developed unique solutions, including “hibernating” the spacecraft during nondaylight portions of each orbit to conserve power, and orienting it with fewer reaction wheels. Their solutions allowed operations to continue until the Cloud Profiling Radar was permanently turned off in December 2023.
“It’s part of who we are as a NASA family that we have dedicated and talented teams that can do things that have never before been done,” said Deborah Vane, CloudSat’s project manager at JPL. “We recovered from these anomalies with techniques that no one has ever used before.”
CloudSat was launched on April 28, 2006, in tandem with a lidar-carrying satellite called CALIPSO (short for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation). The two spacecraft joined an international constellation of weather- and climate-tracking satellites in Earth orbit.
Radar and lidar are considered “active” sensors because they direct beams of energy at Earth — radio waves in the case of CloudSat and laser light in the case of CALIPSO — and measure how the beams reflect off the clouds and fine particles (aerosols) in the atmosphere. Other orbiting science instruments use “passive” sensors that measure reflected sunlight or radiation emitted from Earth or clouds.
Orbiting less than a minute apart, CloudSat and CALIPSO circled the globe in Sun-synchronous orbits from the North to the South Pole, crossing the equator in the early afternoon and after midnight every day. Their overlapping radar-lidar footprint cut through the vertical structure of the atmosphere to study thin and thick clouds, as well as the layers of airborne particles such as dust, sea salt, ash, and soot that can influence cloud formation.
The influence of aerosols on clouds remains a key question for global warming projections. To explore this and other questions, the recently launched PACE satellite and future missions in NASA’s Earth System Observatory will build upon CloudSat’s and CALIPSO’s legacies for a new generation.
https://www.nasa.gov/missions/cloudsat/nasas-cloudsat-ends-mission-peering-into-the-heart-of-clouds/
Hubble Celebrates 34th Anniversary with a Look at the Little Dumbbell Nebula
APR 23, 2024
In celebration of the 34th anniversary of the launch of NASA's legendary Hubble Space Telescope on April 24, astronomers took a snapshot of the Little Dumbbell Nebula (also known as Messier 76, M76, or NGC 650/651) located 3,400 light-years away in the northern circumpolar constellation Perseus. The photogenic nebula is a favorite target of amateur astronomers.
M76 is classified as a planetary nebula, an expanding shell of glowing gases that were ejected from a dying red giant star. The star eventually collapses to an ultra-dense and hot white dwarf. A planetary nebula is unrelated to planets, but have that name because astronomers in the 1700s using low-power telescopes thought this type of object resembled a planet.
M76 is composed of a ring, seen edge-on as the central bar structure, and two lobes on either opening of the ring. Before the star burned out, it ejected the ring of gas and dust. The ring was probably sculpted by the effects of the star that once had a binary companion star. This sloughed off material created a thick disk of dust and gas along the plane of the companion's orbit. The hypothetical companion star isn't seen in the Hubble image, and so it could have been later swallowed by the central star. The disk would be forensic evidence for that stellar cannibalism.
The primary star is collapsing to form a white dwarf. It is one of the hottest stellar remnants known at a scorching 250,000 degrees Fahrenheit, 24 times our Sun's surface temperature. The sizzling white dwarf can be seen as a pinpoint in the center of the nebula. A star visible in projection beneath it is not part of the nebula.
Pinched off by the disk, two lobes of hot gas are escaping from the top and bottom of the "belt," along the star's rotation axis that is perpendicular to the disk. They are being propelled by the hurricane-like outflow of material from the dying star, tearing across space at two million miles per hour. That's fast enough to travel from Earth to the Moon in a little over seven minutes! This torrential "stellar wind" is plowing into cooler, slower-moving gas that was ejected at an earlier stage in the star's life, when it was a red giant. Ferocious ultraviolet radiation from the super-hot star is causing the gases to glow. The red color is from nitrogen, and blue is from oxygen.
Given our solar system is 4.6 billion years old, the entire nebula is a flash in the pan by cosmological timekeeping. It will vanish in about 15,000 years.
Hubble's Star Trekking
Since its launch in 1990 Hubble has made 1.6 million observations of over 53,000 astronomical objects. To date, the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute in Baltimore, Maryland holds 184 terabytes of processed data that is science-ready for astronomers around the world to use for research and analysis. Since 1990, 44,000 science papers have been published from Hubble observations. The space telescope is the most scientifically productive space astrophysics mission in NASA history. The demand for using Hubble is so high it is currently oversubscribed by a factor of six-to-one.
Most of Hubble's discoveries were not anticipated before launch, such as supermassive black holes, the atmospheres of exoplanets, gravitational lensing by dark matter, the presence of dark energy, and the abundance of planet formation among stars.
Hubble will continue research in those domains and capitalize on its unique ultraviolet-light capability on such topics as solar system phenomena, supernovae outbursts, composition of exoplanet atmospheres, and dynamic emission from galaxies. And Hubble investigations continue to benefit from its long baseline of observations of solar system objects, stellar variable phenomena and other exotic astrophysics of the cosmos.
NASA's James Webb Space Telescope was designed to be meant to be complementary to Hubble, and not a substitute. Future Hubble research also will take advantage of the opportunity for synergies with Webb, which observes the universe in infrared light. The combined wavelength coverage of the two space telescopes expands on groundbreaking research in such areas as protostellar disks, exoplanet composition, unusual supernovae, cores of galaxies and chemistry of the distant universe.
https://science.nasa.gov/missions/hubble/hubble-celebrates-34th-anniversary-with-little-dumbbell-nebula/