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Have you ever experienced a meteor shower?

Here is one of the most famous pictures from the Moon -- but digitally reversed.

How did a round star create this square nebula?

To the eye,

Perseid Outburst at Westmeath Lookout

Famed in festival, story, and song the best known

Have you ever seen a gigantic jet?

Catch one of the most active small bodies in the solar system during a rare superoutburst.

The post Comet 29P Undergoes Brightest Outburst in Recent Years appeared first on Sky & Telescope.

Is there anywhere in the Universe where we can escape from radiation? Certainly not here on Earth. And not in space itself, which is filled with diffuse radiation in the form of gamma rays and neutrinos. Scientists have struggled to explain where all those gamma rays and neutrinos come from. A trio of researchers is proposing a source for all that radiation in a new paper: resting black holes.

Supermassive Black Holes (SMBH) likely reside in the center of every large galaxy like the Milky Way. When those SMBHs are actively accreting matter they can spew out a lot of radiation across the entire spectrum, from radio waves to gamma rays. When that happens they’re called active galactic nuclei. But what about SMBHs that are quiet?

A new study says even quiescent SMBHs are emitting gamma rays and neutrinos. The discovery helps explain why the Universe is awash in energetic particles.

The title of the paper is “Soft gamma rays from low accreting supermassive black holes and connection to energetic neutrinos.” It’s published in the journal Nature Communications, and the lead author is Shigeo Kimura from Tohoku University in Sendai, Japan.

Active galaxy nuclei like this one spew out a lot of radiation. Astronomers think some of the Universe’s diffuse radiation comes from more sedate black holes. Credit: NASA/Dana Berry, SkyWorks Digital

Neutrinos are nearly massless subatomic particles and are electrically neutral, which is where they get their name. As a result, their gravitational interaction is near zero, and they don’t interact with the strong nuclear force either. They’re extremely difficult to detect, and they’re passing through your body right now.

Gamma rays, on the other hand, are not difficult to detect. They’re the most energetic photons in the Universe and you definitely don’t want any passing through your body. They’re released in atomic bomb detonations, among other things. Space-based detectors have found gamma rays with voltages in the gigaelectron range. If electron volt ranges aren’t your thing, just think of them as more energetic than visible light by orders of magnitude.

So scientists know a lot about both neutrinos and gamma rays, they just aren’t sure where they all come from. This research might have the answer. “The Universe is filled with a diffuse background of MeV gamma-rays and PeV neutrinos, whose origins are unknown. Here, we propose a scenario that can account for both backgrounds simultaneously,” the authors write.

Scientists think they know where powerful background gamma-rays in the gigaelectron volt (GeV) to teraelectron (TeV) volt ranges come from. They come from AGNs and probably star-forming galaxies. But the source of softer gamma-rays, those in the megaelectron volt (MeV) ranges are unknown. Same with many neutrinos.

This paper shows that low luminosity galactic nuclei could account for both the neutrinos and the gamma rays.

Computer simulation of plasma near a black hole. Credit: Hotaka Shiokawa / EHT

A black hole’s enormous mass and gravitational pull draws matter toward it. It forms an accretion disk of swirling matter, and eventually, the matter falls into the black hole. When that happens an enormous amount of gravitational energy is released. That energy heats up gas around the hole and creates plasma. In this case, the low-accreting black hole has insufficient cooling and the plasma’s temperature can reach tens of billions of degrees Celsius.

What happens is the plasma energizes protons to an extreme degree. They can be 10,000 times more energetic than what the Large Hadron Collider (LHC) can achieve, and the LHC is our most powerful particle accelerator. As these high-speed protons interact with matter and radiation, they produce neutrinos. This can account for the higher energy range neutrinos detected in space.

A similar mechanism produces gamma-rays. As the electrons reach extremely high temperatures, they become efficient producers of gamma-rays in the MeV range through a process called Comptonization.

This image from the study shows how mellow SMBHs can produce diffuse neutrinos and gamma rays that flood the Universe. Image Credit: Shigeo S. Kimura.

So the high-temperature plasma around quiet black holes can produce neutrinos and gamma-rays. Even though these types of black holes are dim and difficult to see, there are a lot of them. It’s reasonable to think they could account for background radiation in the form of gamma-rays and neutrinos.

But this is just a proposed mechanism. There’s no conclusive proof yet. Where will that come from?

Most of our gamma-ray detectors aren’t tuned to the MeV frequency. They’re tuned to higher energy levels. What’s needed is what the authors call a “multimessenger” detector. That’s a detector that detects both gamma-rays and neutrinos at the same time, in the right energy ranges. Proposed missions like e-ASTROGAM, the All-sky Medium Energy Gamma-ray Observatory (AMEGO), and the Gamma-Ray and AntiMatter Survey (GRAMS) should help.

More:

• Press Release: Gamma Rays and Neutrinos from Mellow Supermassive Black Holes
• Research: Soft gamma rays from low accreting supermassive black holes and connection to energetic neutrinos
• Universe Today: Finally an Answer to why Gamma Rays are Coming From Seemingly Empty Space

The post Even the Quiet Supermassive Black Holes are Blasting out Neutrinos and Gamma Rays appeared first on Universe Today.

Earth has a new eye in orbit to monitor our changing planet.  

Landsat 9 launched on September 27, 2021 continuing the Landsat family of satellite’s nearly 50-year tradition of making critical observations to help with energy and water management, forest monitoring, human and environmental health, urban planning, disaster recovery and agriculture.

And… liftoff! ?

The #Landsat 9 satellite has lifted off from the Vandenberg Space Force Base in California aboard a @ULALaunch Atlas V rocket at 2:12pm ET. pic.twitter.com/O6YXhtf7kT

— NASA (@NASA) September 27, 2021

The mission launched from Vandenberg Space Force Base in California, on board an Atlas V rocket. The payload and booster reached orbit about 16 minutes after launch, and Landsat 9 separated from the rocket about an hour later, joining Landsat 8 – which has been in orbit since 2013 – along with the rest of NASA’s Earth-observing fleet.

Landsat is a joint mission between NASA and the U.S. Geological Survey (USGS). The first Landsat launched in 1972.

“The Landsat mission is like no other,” said Karen St. Germain, director of the Earth Science Division at NASA Headquarters. “For nearly 50 years, Landsat satellites observed our home planet, providing an unparalleled record of how its surface has changed over timescales from days to decades. Through this partnership with USGS, we’ve been able to provide continuous and timely data for users ranging from farmers to resource managers and scientists. This data can help us understand, predict, and plan for the future in a changing climate.”

Landsat 9 is now making its way to its final orbital altitude of 438 miles (705 kilometers). It will be in a near-polar, Sun-synchronous orbit.

 Combining the power of both Landsat 8 and 9, the two satellites can now photograph the entire Earth every eight days. Scientists and researchers use the images to monitor phenomena including agricultural productivity, forest extent and health, water quality, coral reef habitat health, and glacier dynamics. 

But anyone can look at or use the images, as Landsat data from over the years are available to view and download at this USGS website. You can also see other images of Earth from orbit at the NASA Earth Observatory website.

Landsat imagery is used to monitor natural disasters, such as these comparison images showing before and after images of flooding of the Ohio and Mississippi Rivers in 2011. Credit: NASA/USGS.

“[This] successful launch is a major milestone in the nearly 50-year joint partnership between USGS and NASA who, for decades, have partnered to collect valuable scientific information and use that data to shape policy with the utmost scientific integrity,” said Secretary of the Interior Deb Haaland. “As the impacts of the climate crisis intensify in the United States and across the globe, Landsat 9 will provide data and imagery to help make science-based decisions on key issues including water use, wildfire impacts, coral reef degradation, glacier and ice-shelf retreat, and tropical deforestation.”

Landsat 9 has two instruments on board: the Operational Land Imager 2 (OLI-2) and the Thermal Infrared Sensor 2 (TIRS-2). Working together, the two instruments can measure 11 wavelengths of light reflected or radiated off Earth’s surface, in the visible spectrum as well as other wavelengths beyond what our eyes can see. As the satellite orbits, these instruments will capture scenes across a swath of 115 miles (185 kilometers). Each pixel in these images represents an area about 98 feet (30 meters) across, about the size of a baseball infield. At that high a resolution, NASA says that resource managers will be able to identify most crop fields in the United States.

Earth orbiting satellites and missions, as of 2019. Credit: NASA

Further reading about the launch: NASA Earth Observatory, NASA blogs

The post Landsat 9 Joins a Fleet of Earth Observation Satellites appeared first on Universe Today.

North Korean state media declared the test of the Hwasong-8 a success, but outside experts are skeptical.

Black and Indigenous people and people of colour are more at risk from covid-19, and new modelling suggests that prioritising vaccines based on race or neighbourhood in addition to age could have led to fewer deaths

Black and Indigenous people and people of colour are more at risk from covid-19, and new modelling suggests that prioritising vaccines based on race or neighbourhood in addition to age could have led to fewer deaths

People aged 65 years or over who lost their homes in the 2011 Japan earthquake and tsunami typically saw an increase in their rate of cognitive decline

People aged 65 years or over who lost their homes in the 2011 Japan earthquake and tsunami typically saw an increase in their rate of cognitive decline

NASA astronaut Megan McArthur shared three photos of the massive Hurricane Sam as seen from the International Space Station.

The strange effects of red wine, plus origami clothes that expand to fit children as they grow and a satellite the width of a vegemite sandwich, in Feedback’s weird weekly round-up

There is a stem cell revolution on the way, but it isn't the regenerative medicine some people are pushing, say John E. J. Rasko and Carl Power

The search for water on Mars has consumed a lot of data collection and research time.  Underground lakes have been found and then discounted again.  Melted ice has been proposed and then dismissed again.  All this attention focuses on one of the most important resources available to any future Martian explorers.  Water is critical to human life and can also be split into two crucial components for rocket fuel.  So finding an easily accessible cache of it is a prerequisite to any serious human mission to the red planet that expects to return its crew back home.

A team from the Lunar and Planetary Institute (LPI) thinks they might have found easily accessible reservoirs of water ice at much more temperate latitudes than had been traditionally thought.  Finding any significant water source near the equator would be cause for celebration, as most large known water deposits are located near the poles, which is even more inhospitable to human exploration than the rest of the planet.  

UT video discussing in-situ resource utilization on Mars.

Such a reservoir is precisely what Dr. Germán Martínez of LPI and his team think they have found.  To do so, they used data collected by Mars Odyssey’s Neutron Spectrometer.  They looked at sub-surface hydrogen levels, which have been studied before. But their novel contribution was to notice a pattern.  

There was a spike in hydrogen levels in certain parts of the planet, particularly in Hellas Planitia and Utopia Rupes in the southern and northern hemispheres, respectively.  That spike happened to be seasonal, which pointed to a type of source scientists hadn’t been able to differentiate before.

Map of Mars highlighting significant seasonal variations in surface hydrogen levels.
Credit – G. Martinez et al.

Water ice could potentially be the cause of the seasonality.  The spectrometer’s measured hydrogen signal increased during the colder months, which indicates that water ice could be freezing in the subterranean regions Odyssey was monitoring. During warmer months, the ice would sublimate, carrying away the hydrogen and leading to a drop in Odyssey’s readings.

Another finding lends even more credence to the hypothesis that relatively accessible water ice is the cause of the signal.  Odyssey found other areas with high levels of hydrogen, but they did not show the seasonality that the readings at Hellas Planitia and Utopia Rupes did.  In these cases, the water is probably deeper underground, less susceptible to sublimation in warmer months, and therefore less accessible for use in exploration missions.

Figure from the research paper showing the distribution of hydrogen.
Credit – Martinez et al.

Those exploration missions could include robotic rovers, which would likely be necessary to confirm or deny the presence of easily accessible waters in these areas.  Other remote sensings efforts can be brought to bear in the meantime. If the LPI team’s hypothesis turns out to be accurate, that new information could be a game-changer for the location of any future crewed Martian mission.

Learn More:
EuroPlanet Society – Scientists use seasons to find water for future Mars astronauts
UT – Does Mars Have Seasons?
UT – Nothing Says Springtime on Mars Like Explosions of Sand
LPI – Missing Water on Mars May Be Stored in the Crust

Lead Image:
Image of Mars from Viking Orbiter.
Credit – NASA / JPL -Caltech / USGS

The post Mars has Seasons, and They Might Have Revealed Where it’s Hiding its Water appeared first on Universe Today.

China launched two missions on Monday within only a few hours of each other, and one has been declared lost.