NASA Astronomy Picture of the Day

December 4, 2024

Driveway Analemma

Does the Sun return to the same spot on the sky every day? No. A more visual answer is an analemma, a composite of sky images taken at the same time and from the same place over a year. At completion, you can see that the Sun makes a figure 8 on the sky. The featured unusual analemma does not, however, picture the Sun directly: it was created by looking in the opposite direction. All that was required was noting where the shadow of an edge of a house was in the driveway every clear day at the same time. Starting in March in Falcon, Colorado, USA, the photographer methodically marked the shadow's 1 pm location. In one frame you can even see the photographer himself. Although this analemma will be completed in 2025, you can start drawing your own driveway analemma using no fancy equipment as soon as today.

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

https://youtu.be/7QB_MOemCqs?si=pB3Vm5kyTRFrNWdB

NASA astronaut Don Pettit is one of the best photographers to have boarded the ISS. Here are some of his most stunning images

December 4, 2024 at 5:53 am

Among many other things, astronauts onboard the International Space Station are in the enviable position of being able to capture incredible photographs that no-one on Earth can.

Those who live and work aboard the Space Station can capture countries and continents floating by; approaching supply ships; spacewalks in action; aurorae, stars, planets and other celestial wonders from the vantage point of Earth orbit.

One such astronaut who has been making waves with his incredible images is NASA's Don Pettit.

Dr. Donald Pettit has logged over 370 days in space and over 13 spacewalk hours.

For his most recent 6-month stint, he launched to the International Space Station on a Soyuz spacecraft on 11 September 2024.

Astronauts have multiple tasks on board the Space Station, from keeping physically active and exploring the effects of spaceflight on the human body, to conducting science experiments in weightlessness.

But Pettit is perhaps most well-known to those of us back on Earth for being one heck of a photographer.

He made headlines In October when he and fellow NASA astronaut Mathew Dominick captured an image of Comet C/2023 A3 from the Space Station.

The same month he captured an image of the October 2024 aurora display from space.

Pettit is clearly no photographic lightweight.

He's even been known to do his own image processing, including stacking star trails images as a way of effectively increasing the exposure capabilities of the cameras on the ISS.

Here are some of Pettit's best photographs from the International Space Station, so far…

cont.

https://www.skyatnightmagazine.com/astrophotography/nasa-astronaut-don-pettit-best-images-of-space

https://x.com/astro_Pettit

Views of Starship Flight 6 from International Space Station

Dec 3, 2024

While orbiting approximately 250 miles above Earth, external cameras aboard the International Space Station captured the sixth test flight of SpaceX’s Starship after liftoff at 4 p.m. CST on Tuesday, Nov. 19.

For Artemis III, the first crewed return to the Moon in over 50 years, NASA is working with SpaceX to develop Starship as a lunar lander.

Prior to the crewed Artemis III mission, SpaceX will perform an uncrewed landing demonstration mission on the Moon.

https://www.youtube.com/watch?v=QtsmOAhauNo

Antarctica’s icy peninsula turns green as temperatures rise

December 04, 2024

The icy landscapes of the Antarctic Peninsula are becoming greener, with vegetation spreading across the once predominantly frozen terrain.

During the past 38 years, the area covered by plants has increased more than tenfold, according to satellite imagery from NASA.

Between 1986 and 2021, vegetation expanded from 0.33 square miles to 4.61 square miles, with significant growth accelerating after 2016.

The greening trend is attributed to rising temperatures, which have made the Antarctic Peninsula one of the fastest-warming regions on Earth.

“This trend echoes a wider pattern of greening in cold-climate ecosystems in response to recent warming,” the researchers wrote.

The study, led by Tom Roland from the University of Exeter and Olly Bartlett from the University of Hertfordshire, highlights how this transformation could impact the peninsula's ecology, potentially opening the door for invasive plant species.

NASA’s Landsat data reveals that much of the new vegetation comprises mosses, which dominate the landscape at elevations below 1,000 feet.

Field studies have shown that moss accumulation is accelerating, particularly on the western side of the peninsula and the South Shetland Islands.

“The rate of greening itself is quite striking, especially in the last few years,” Olly Bartlett noted.

Antarctica hosts a variety of mosses, liverworts, lichens, and fungi, but only two native species of flowering plants. As moss ecosystems expand, there is a growing concern that soil formation could facilitate the introduction of non-native species, posing a threat to the continent’s biodiversity.

The rapid environmental changes on the Antarctic Peninsula coincide with alarming ice loss. The Antarctic ice sheet is losing about 150 billion tons of ice annually, contributing to rising sea levels.

According to NASA, the rate of global sea level rise could double by 2100 if ice melt in Antarctica and Greenland continues at its current pace.

While the greening of Antarctica highlights the planet's shifting climate, it also raises questions about the future of its fragile ecosystems.

“We need to go to these places where we’re seeing the most distinctive changes and see what’s happening on the ground,” Tom Roland said.

https://tribune.com.pk/story/2513688/antarcticas-icy-peninsula-turns-green-as-temperatures-rise

Astronomers Discover Fourth Exoplanet in Kepler-51 System

Dec 3, 2024

Kepler-51 is located approximately 2,615 light-years away in the constellation of Cygnus.

Also known as KOI-620, this star was already known to host three Saturn-sized ‘super-puff’ exoplanets: Kepler-51b, c, and d.

First discovered by NASA’s Kepler space telescope in 2012, these worlds have orbital period ratios close to 1:2:3 (45 days, 85 days, and 130 days, respectively).

They are several times the mass of Earth, and have hydrogen/helium atmospheres.

“Super puff planets are very unusual in that they have very low mass and low density,” said Penn State astronomer Jessica Libby-Roberts.

“The three previously known planets that orbit the star, Kepler-51, are about the size of Saturn but only a few times the mass of Earth, resulting in a density like cotton candy.”

“We think they have tiny cores and huge atmospheres of hydrogen of helium, but how these strange planets formed and how their atmospheres haven’t been blown away by the intense radiation of their young star has remained a mystery.”

“We planned to use Webb to study one of these planets to help answer these questions, but now we have to explain a fourth low-mass planet in the system.”

To examine the evidence of the fourth planet in the system, Kepler-51e, the astronomers utilized an extensive transit timing data set spanning over 14 years from various facilities, including Webb, the Apache Point Observatory telescope and the Penn State Davey Lab telescope.

“We conducted what is called a ‘brute force’ search, testing out many different combinations of planet properties to find the four-planet model that explains all of the transit data gathered over the past 14 years,” said Osaka University astronomer Kento Masuda.

“We found that the signal is best explained if Kepler-51e has a mass similar to the other three planets and follows a fairly circular orbit of about 264 days — something we would expect based on other planetary systems.”

“Other possible solutions we found involve a more massive planet on a wider orbit, though we think these are less likely.”

It is unclear if Kepler-51e is also a super puff planet, because the researchers have not observed a transit of Kepler-51e and therefore cannot calculate its radius or density.

According to the team, a wide range of masses (<= Jupiter mass) and orbital periods (<=10 years) are possible for the planet.

“Super puff planets are fairly rare, and when they do occur, they tend to be the only one in a planetary system,” said Penn State astronomer Jessica Libby-Roberts.

“If trying to explain how three super puffs formed in one system wasn’t challenging enough, now we have to explain a fourth planet, whether it’s a super puff or not. And we can’t rule out additional planets in the system either.”

“Kepler-51e has an orbit slightly larger than Venus and is just inside the star’s habitable zone, so a lot more could be going on beyond that distance if we take the time to look.”

“Continuing to look at transit timing variations might help us discover planets that are further away from their stars and might aid in our search for planets that could potentially support life.”

https://www.sci.news/astronomy/kepler-51-system-fourth-exoplanet-13477.html

https://iopscience.iop.org/article/10.3847/1538-3881/ad83d3

Astronaut Suni Williams and Astrobee

Dec 03, 2024

In this picture from Nov. 15, 2024, Astronaut Suni Williams imitates the tentacle-like arms of the Astrobee robotic free-flyer in the foreground.

Astrobee robots help astronauts reduce time they spend on routine duties, leaving them to focus more on the things that only humans can do.

Working autonomously or via remote control by astronauts, flight controllers or researchers on the ground, the robots are designed to complete tasks such as taking inventory, documenting experiments conducted by astronauts with their built-in cameras or working together to move cargo throughout the station.

In addition, the system serves as a research platform that can be outfitted and programmed to carry out experiments in microgravity – helping us to learn more about how robotics can benefit astronauts in space.

https://www.nasa.gov/image-article/astronaut-suni-williams-and-astrobee/

Patagonian Shelf Waters Abloo in austral spring, NASA Earth Observatory

Wednesday, December 4th 2024 - 06:11 UTC

An austral spring 2024, a phytoplankton bloom off the coast of Argentina painted the waters blue and green. Blooms are common in the region this time of year, but clouds often block the view from above.

However, clouds stayed hundreds of kilometers offshore on November 30, 2024, allowing the OCI (Ocean Color Instrument) on NASA’s PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite to capture this image of the colorful bloom in the South Atlantic Ocean.

Phytoplanktons are among the smallest organisms in the ocean. But when their populations explode, the blooms can span thousands of square kilometers, making them visible from space.

In this scene, the bloom stretches east to west over the Patagonian Shelf and extends over 1,000 kilometers (600 miles) north from the Falkland Islands.

Blooms in this region are stimulated by the ocean’s complex circulation patterns. For example, rising water along the Patagonian Shelf-break front carries nutrients to the surface, where phytoplanktons thrive in spring and summer sunlight.

Currents and eddies also stir the water horizontally, creating surface patterns that become even more visible in chlorophyll observations. Other nutrients can come from river sediment and windblown dust from Patagonia.

Without a physical sample, it’s not yet possible to identify the types of phytoplankton present in this image. Studies show that diatoms and dinoflagellates tend to be present here in the austral spring.

Diatoms, a microscopic form of algae, have silica shells and plenty of chlorophyll that can make the water appear green.

Coccolithophores, which have chalky calcium carbonate plates (coccoliths) that reflect light and make the water appear bright blue, tend to show up in summer.

Phytoplankton are the primary food source for zooplankton, shellfish, fish, and larger marine creatures.

With its intense phytoplankton blooms, the area around the Patagonian Shelf-break supports rich aquatic diversity and vast fisheries.

https://en.mercopress.com/2024/12/04/patagonian-shelf-waters-abloo-in-austral-spring-nasa-earth-observatory

Dramatic video shows bicycle tire-sized asteroid nearly hit Earth as ‘nice fireball in the sky’ illuminates Siberia

Dec. 3, 2024, 2:37 p.m. ET

An asteroid streaked past northern Siberia in the middle of the night Tuesday before burning up in Earth’s atmosphere, lighting up the skies with a blinding flash, dramatic video shows.

The relatively diminutive asteroid measured just 27 inches wide — about the diameter of a bicycle tire — and posed no danger to Earth, but was still enough to produce a “nice fireball in the sky” over the Siberian tundra around 4:15 a.m. local time, the European Space Agency wrote on X.

The asteroid, temporarily given the rolls-off-the-tongue name C0WEPC5, was a rare instance of what’s known as an “imminent impactor,” discovered at the Kitt Peak National Observatory near Tucson, Ariz. just hours before its dramatic appearance, Space.com reported.

C0WEPC5 is just the 11th imminent impactor ever discovered and the record-setting fourth this year alone.

Space agencies around the world continuously monitor the skies for asteroids and other celestial objects on a potential collision course with Earth.

On June 30, 1908, a much larger asteroid with a diameter of over 130 feet exploded over Siberia in what has since been named the Tunguska Event.

The impact site was not examined by scientists until 20 years later, when they discovered the asteroid carved a massive area of destruction of around 830 square miles, according to NASA.

In 2016, the United Nations enshrined the celestial happening with its own date, designating June 30 as International Asteroid Day to boost awareness of asteroids and space agencies’ efforts to discover them.

https://nypost.com/2024/12/03/us-news/asteroid-nearly-hits-earth-dramatically-illuminating-night-sky-over-siberia/

https://science.nasa.gov/solar-system/comets/nasa-led-team-links-comet-water-to-earths-oceans/

https://www.science.org/doi/10.1126/sciadv.adp2191

NASA-Led Team Links Comet Water to Earth’s Oceans

Dec 03, 2024

Researchers have found that water on Comet 67P/Churyumov–Gerasimenko has a similar molecular signature to the water in Earth’s oceans.

Contradicting some recent results, this finding reopens the case that Jupiter-family comets like 67P could have helped deliver water to Earth.

Water was essential for life to form and flourish on Earth and it remains central for Earth life today.

While some water likely existed in the gas and dust from which our planet materialized around 4.6 billion years ago, much of the water would have vaporized because Earth formed close to the Sun’s intense heat.

How Earth ultimately became rich in liquid water has remained a source of debate for scientists.

Research has shown that some of Earth’s water originated through vapor vented from volcanoes; that vapor condensed and rained down on the oceans.

But scientists have found evidence that a substantial portion of our oceans came from the ice and minerals on asteroids, and possibly comets, that crashed into Earth.

A wave of comet and asteroid collisions with the solar system’s inner planets 4 billion years ago would have made this possible.

While the case connecting asteroid water to Earth’s is strong, the role of comets has puzzled scientists.

Several measurements of Jupiter-family comets — which contain primitive material from the early solar system and are thought to have formed beyond the orbit of Saturn — showed a strong link between their water and Earth’s.

This link was based on a key molecular signature scientists use to trace the origin of water across the solar system.

This signature is the ratio of deuterium (D) to regular hydrogen (H) in the water of any object, and it gives scientists clues about where that object formed.

Deuterium is a rare, heavier type — or isotope — of hydrogen. When compared to Earth’s water, this hydrogen ratio in comets and asteroids can reveal whether there’s a connection.

Because water with deuterium is more likely to form in cold environments, there’s a higher concentration of the isotope on objects that formed far from the Sun, such as comets, than in objects that formed closer to the Sun, like asteroids.

Measurements within the last couple of decades of deuterium in the water vapor of several other Jupiter-family comets showed similar levels to Earth’s water.

“It was really starting to look like these comets played a major role in delivering water to Earth,” said Kathleen Mandt, planetary scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Mandt led the research, published in Science Advances on Nov. 13, that revises the abundance of deuterium in 67P.

But in 2014, ESA’s (European Space Agency) Rosetta mission to 67P challenged the idea that Jupiter-family comets helped fill Earth’s water reservoir.

Scientists who analyzed Rosetta’s water measurements found the highest concentration of deuterium of any comet, and about three times more deuterium than there is in Earth’s oceans, which have about 1 deuterium atom for every 6,420 hydrogen atoms.

“It was a big surprise and it made us rethink everything,” Mandt said.

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Mandt’s team decided to use an advanced statistical-computation technique to automate the laborious process of isolating deuterium-rich water in more than 16,000 Rosetta measurements.

Rosetta made these measurements in the “coma” of gas and dust surrounding 67P. Mandt’s team, which included Rosetta scientists, was the first to analyze all of the European mission’s water measurements spanning the entire mission.

The researchers wanted to understand what physical processes caused the variability in the hydrogen isotope ratios measured at comets.

Lab studies and comet observations showed that cometary dust could affect the readings of the hydrogen ratio that scientists detect in comet vapor, which could change our understanding of where comet water comes from and how it compares to Earth’s water.

“So I was just curious if we could find evidence for that happening at 67P,” Mandt said. “And this is just one of those very rare cases where you propose a hypothesis and actually find it happening.”

Indeed, Mandt’s team found a clear connection between deuterium measurements in the coma of 67P and the amount of dust around the Rosetta spacecraft, showing that the measurements taken near the spacecraft in some parts of the coma may not be representative of the composition of a comet’s body.

As a comet moves in its orbit closer to the Sun, its surface warms up, causing gas to release from the surface, including dust with bits of water ice on it.

Water with deuterium sticks to dust grains more readily than regular water does, research suggests.

When the ice on these dust grains is released into the coma, this effect could make the comet appear to have more deuterium than it has.

Mandt and her team reported that by the time dust gets to the outer part of the coma, at least 75 miles from the comet body, it is dried out.

With the deuterium-rich water gone, a spacecraft can accurately measure the amount of deuterium coming from the comet body.

This finding, the paper authors say, has big implications not only for understanding comets’ role in delivering Earth’s water, but also for understanding comet observations that provide insight into the formation of the early solar system.

“This means there is a great opportunity to revisit our past observations and prepare for future ones so we can better account for the dust effects,” Mandt said.

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