NASA Astronomy Picture of the Day

Nov 5, 2023

Creature Aurora Over Norway

It was Halloween and the sky looked like a creature. Exactly which creature, the astrophotographer was unsure (but possibly you can suggest one). Exactly what caused this eerie apparition in 2013 was sure: one of the best auroral displays that year. This spectacular aurora had an unusually high degree of detail. Pictured here, the vivid green and purple auroral colors are caused by high atmospheric oxygen and nitrogen reacting to a burst of incoming electrons. Birch trees in Tromsø, Norway formed an also eerie foreground. Frequently, new photogenic auroras accompany new geomagnetic storms.

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

NASA’s Lucy Spacecraft Discovers 2nd Asteroid During Dinkinesh Flyby

On Nov. 1, NASA’s Lucy spacecraft flew by not just its first asteroid, but its first two. The first images returned by Lucy reveal that the small main belt asteroid Dinkinesh is actually a binary pair.

“Dinkinesh really did live up to its name; this is marvelous,” said Hal Levison, referring to the meaning of Dinkinesh in the Amharic language, “marvelous.” Levison is principal investigator for Lucy from the Boulder, Colorado, branch of the San-Antonio-based Southwest Research Institute. “When Lucy was originally selected for flight, we planned to fly by seven asteroids. With the addition of Dinkinesh, two Trojan moons, and now this satellite, we’ve turned it up to 11.”

In the weeks prior to the spacecraft’s encounter with Dinkinesh, the Lucy team had wondered if Dinkinesh might be a binary system, given how Lucy’s instruments were seeing the asteroid’s brightness changing with time. The first images from the encounter removed all doubt. Dinkinesh is a close binary. From a preliminary analysis of the first available images, the team estimates that the larger body is approximately 0.5 miles (790 m) at its widest, while the smaller is about 0.15 miles (220 m) in size.

This encounter primarily served as an in-flight test of the spacecraft, specifically focusing on testing the system that allows Lucy to autonomously track an asteroid as it flies past at 10,000 mph, referred to as the terminal tracking system.

“This is an awesome series of images. They indicate that the terminal tracking system worked as intended, even when the universe presented us with a more difficult target than we expected,” said Tom Kennedy, guidance and navigation engineer at Lockheed Martin in Littleton, Colorado. “It’s one thing to simulate, test, and practice. It’s another thing entirely to see it actually happen.”

While this encounter was carried out as an engineering test, the team’s scientists are excitedly poring over the data to glean insights into the nature of small asteroids.

“We knew this was going to be the smallest main belt asteroid ever seen up close,” said Keith Noll, Lucy project scientist from NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The fact that it is two makes it even more exciting. In some ways these asteroids look similar to the near-Earth asteroid binary Didymos and Dimorphos that DART saw, but there are some really interesting differences that we will be investigating.”

It will take up to a week for the team to downlink the remainder of the encounter data from the spacecraft. The team will use this data to evaluate the spacecraft’s behavior during the encounter and to prepare for the next close-up look at an asteroid, the main belt asteroid Donaldjohanson, in 2025. Lucy will then be well-prepared to encounter the mission’s main targets, the Jupiter Trojan asteroids, starting in 2027.

https://www.nasa.gov/image-article/nasas-lucy-spacecraft-discovers-2nd-asteroid-during-dinkinesh-flyby/

Scorching, Seven-Planet System Revealed by New Kepler Exoplanet List

NOV 02, 2023

A system of seven sweltering planets has been revealed by continued study of data from NASA’s retired Kepler space telescope: Each one is bathed in more radiant heat from their host star per area than any planet in our solar system. Also unlike any of our immediate neighbors, all seven planets in this system, named Kepler-385, are larger than Earth but smaller than Neptune. It is one of only a few planetary systems known to contain more than six verified planets or planet candidates. The Kepler-385 system is among the highlights of a new Kepler catalog that contains almost 4,400 planet candidates, including more than 700 multi-planet systems.

“We’ve assembled the most accurate list of Kepler planet candidates and their properties to date,” said Jack Lissauer, a research scientist at NASA’s Ames Research Center in California’s Silicon Valley and lead author on the paper presenting the new catalog. “NASA’s Kepler mission has discovered the majority of known exoplanets, and this new catalog will enable astronomers to learn more about their characteristics.”

At the center of the Kepler-385 system is a Sun-like star about 10% larger and 5% hotter than the Sun. The two inner planets, both slightly larger than Earth, are probably rocky and may have thin atmospheres. The other five planets are larger – each with a radius about twice the size of Earth’s – and expected to be enshrouded in thick atmospheres.

The ability to describe the properties of the Kepler-385 system in such detail is testament to the quality of this latest catalog of exoplanets. While the Kepler mission’s final catalogs focused on producing lists optimized to measure how common planets are around other stars, this study focuses on producing a comprehensive list that provides accurate information about each of the systems, making discoveries like Kepler-385 possible.

The new catalog uses improved measurements of stellar properties and calculates more accurately the path of each transiting planet across its host star. This combination illustrates that when a star hosts several transiting planets, they typically have more circular orbits than when a star hosts only one or two.

Kepler’s primary observations ceased in 2013 and were followed by the telescope’s extended mission, called K2, which continued until 2018. The data Kepler collected continues to reveal new discoveries about our galaxy. After the mission already showed us there are more planets than stars, this new study paints a more detailed picture of what each of those planets and their home systems look like, giving us a better view of the many worlds beyond our solar system.

The research article, “Updated Catalog of Kepler Planet Candidates: Focus on Accuracy and Orbital Periods” is forthcoming in The Journal of Planetary Science.

https://www.nasa.gov/general/scorching-seven-planet-system-revealed-by-new-kepler-exoplanet-list/