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NASA’s DART Mission Also Changed Didymos’ Orbit Around Sun

NASA’s Double Asteroid Redirection Test (DART) spacecraft impacted the asteroid moonlet Dimorphos, which orbits the larger asteroid Didymos, in September 2022. The purpose of this mission was to test the kinetic impactor method, a potential strategy to alter the orbit of asteroids so they don’t pose a threat to Earth. The test was a success, as images taken by the Italian Space Agency’s LICIACube (which traveled alongside the DART mission) after the impact showed. Combined with Earth-based observations, these confirmed that the moonlet’s orbit changed noticeably.

According to a recent update from NASA, DART”s impact also altered the orbit of both asteroids around the Sun. Since Didymos and Dimorphos are part of a binary system and orbit each other around a shared center of mass, changes to one asteroid affect the other. As an international team of researchers described in a study that appeared in the journal Science Advances, observations revealed that asteroids’ 770-day orbital period around the Sun changed by a fraction of a second post-impact. This marks the first time a human-made object has altered the path of a celestial body around the Sun.

When DART struck Dimorphos, follow-up observations showed that the moonlet’s orbit was shortened by 33 minutes. The impact also produced a cloud of rocky debris that carried its own momentum away from the asteroid. This imparted momentum to the asteroid, known as a momentum enhancement factor, in addition to the impact alone. According to the new study, the momentum enhancement factor from DART’s impact was about two, meaning the debris doubled the force imparted by the spacecraft alone. This is what led to Didymos’ orbit being altered by 0.15 seconds.

*This LICIACube image, taken moments after impact on Sept. 26th, 2022, shows rocky debris fanning out from Dimorphos. Credit: ASI/NASA*

Thomas Statler, the lead scientist for Solar System small bodies at NASA Headquarters, said in a NASA press release:

This is a tiny change to the orbit, but given enough time, even a tiny change can grow to a significant deflection. The team’s amazingly precise measurement again validates kinetic impact as a technique for defending Earth against asteroid hazards and shows how a binary asteroid might be deflected by impacting just one member of the pair.

To demonstrate that DART had a detectable influence on both asteroids, the researchers needed to measure Didymos’ orbit with extreme precision. To do this, the team combined radar and other ground-based observations and tracked how the asteroid passed in front of background stars (aka stellar occultations). This was challenging because tracking stellar occultations requires precise timing and being in the right location. For this, the team relied on volunteer astronomers around the globe who recorded 22 stellar occultations between October 2022 and March 2025. Said study co-lead Steve Chesley, a senior research scientist at JPL:

When combined with years of existing ground-based observations, these stellar occultation observations became key in helping us calculate how DART had changed Didymos’ orbit. This work is highly weather-dependent and often requires travel to remote regions with no guarantee of success. This result would not have been possible without the dedication of dozens of volunteer occultation observers around the world. This technique allowed the team to obtain extremely precise measurements of the asteroid’s speed, shape, and position.

*The above infographic shows the current orbit of Dimorphos around Didymos, and its projected orbit following the impact of DART. Credit: NASA/Johns Hopkins APL*

“The change in the binary system’s orbital speed was about 11.7 microns per second, or 1.7 inches per hour. Over time, such a small change in an asteroid’s motion can make the difference between a hazardous object hitting or missing our planet,” added Rahil Makadia of the University of Illinois Urbana-Champaign and the lead author on the paper. However, NASA and the ESA have both determined that the modification to Didymos’ orbit does not make it a threat to Earth. Studying changes in Didymos’ motion also helped the researchers calculate the densities of both asteroids, which revealed that Dimorphos is slightly less dense.

This supports the theory that it formed from rocky debris shed by a rapidly spinning Didymos that eventually clumped together to form a “rubble pile” asteroid. Although Didymos is not a Potentially Hazardous Object (PHO), meaning it poses no collision threat to Earth, the success of the DART mission demonstrates the effectiveness of the kinetic impactor method. The first step, however, is to detect PHOs far enough in advance that a kinetic impactor can be sent to rendezvous with them. This is the purpose behind NASA’s Near-Earth Object (NEO) Surveyor mission: a next-generation space survey telescope, and the first to be built for planetary defense.

Further Reading: NASA

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Parents charged in Murrieta house fire that killed their two daughters

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Authorities have arrested the parents of two young girls who died in a Murrieta house fire last year that burned several structures and killed multiple animals.

Stacey Hales, 46, and Adam Keenan, 43, from Murrieta were arrested Friday and booked on multiple charges connected to the fire that started in the early hours of Dec. 20.

According to the Murrieta Police Department, officers responded to a residential structure fire at 41690 Knight Drive and found a mobile home, carport, three vehicles, two outbuildings and a large pine tree engulfed in flames. Firefighters extinguished the fire after about 45 minutes.

The couple’s daughters, 11-year-old Abagail Keenan and 12-year-old Emma Keenan, were found dead inside the home, along with several household pets. Hales and Keenan were hospitalized after the fire.

Investigators determined that Hales and Keenan were “criminally responsible for the fire,” according to police.

Hales, who is free on $160,000 bail, faces two counts of reckless burning causing death, two counts of reckless burning of an inhabited structure, two counts of child endangerment and one count of animal cruelty. She is also facing a sentence enhancement, according to police.

Keenan was charged with two counts of child endangerment and one count of being under the influence of a controlled substance. His next court appearance is scheduled for March 17, according to booking records.

In the days following the tragedy, a family friend created a GoFundMe page to help Hales cover funeral costs for the girls. The fundraiser reached $54,000 by Dec. 22, according to a previous Times report, and later raised more than $113,000, KTLA reported.

The beneficiary of the funds was Hales’ brother, Scott Nalder. The page has since been removed.

Murrieta police encourage anyone with information about the investigation to contact Det. Velazquez at (951) 461-6340. Information may also be provided anonymously through the department’s website.

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The Republican pollster Kristen Soltis Anderson joins E.J. Dionne Jr. and Robert Siegel to discuss Trump’s falling approval rating and what it portends for November.

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A Glorious Spiral of Star Formation

To understand how stars form, astronomers need to watch the process play out in galaxies. That simple fact is behind PHANGS, the Physics at High Angular resolution in Nearby GalaxieS survey. It’s a large-scale, multiwavelength, multitelescope survey of dozens of nearby spiral galaxies. Its targets are galaxies close enough that star-forming features like giant molecular clouds (GMCs), HII regions, and stellar clusters can be resolved.

PHANGS started years ago with observations from telescopes like ALMA and the Hubble. When the JWST was launched, it participated as well. The core question that PHANGS is addressing is simple: How exactly does gas become stars, and how does stellar feedback modulate the process?

PHANGS has generated catalogs of data that’s been cited in more than 150 scientific papers. It’s been a huge success for astronomers who study stellar formation and feedback. But it’s also generated a collection of gorgeous images, many of which have been featured as a Picture of the Week (POTW), Astronomy Picture of the Day (APOD), as well as other featured images, and even an ESA/Hubble calendar. There’s also a postage stamp featuring the JWST’s image of NGC 628.

The JWST’s image of the spiral galaxy NGC 628 is featured in a US Postal Service stamp. Image Credit: NASA, ESA, Canadian Space Agency, and Space Telescope Science Institute. US Postal Service.

The JWST has made an important contribution to PHANGS. It’s kind of like the missing link in the survey, because it can see inside dust better than other telescopes. That means it can see earlier stages of star formation than its comrades.

But as Universe Today readers know, the telescope’s portraits of spiral galaxies are delicious as stand alone images, even without the scientific context. We were all excited by the galactic portraits the JWST gifted us in 2023. They placed Nature’s creative glory on a pedestal where it belongs.

This mosaic shows 19 galaxies imaged in near- and mid-infrared light by the JWST as part of PHANGS. There’s so much beauty and detail it’s hard to digest it all. Image Credit: NASA, ESA, CSA, STScI, J. Lee (STScI), T. Williams (Oxford), PHANGS Team, E. Wheatley (STScI)

The latest ESA Picture of the Month features NGC 5134, a spiral galaxy about 65 million years away. The JWST captured in both near-infrared and mid-infrared light. MIRI, the telescope’s Mid-Infrared Instrument, captures the light emitted by warm dust in the galaxy. It shows the clumps and strands of gas woven throughout the galaxy. NIR, the Near-Infrared Instrument, captures the light from the clusters of stars that populate the spiral arms.

Galaxies like NGC 5134 feature a constant ebb and flow of gas. It’s almost like a vast circulatory system, where gas moves around and is recycled through heating and cooling phases by galactic feedback. Individual stars play an important role in this with their stellar winds and supernove explosions.

The billowing clouds of gas in the spiral arms is where most of the star forming action takes place. Populations of stars differ in different parts of the arms. To understand that, we have to understand something critical about spiral galaxies: the arms don’t rotate.

Even though they look like giant rotating pinwheels, that’s not what spiral galaxies are. The arms don’t rotate, only density waves do. The waves sweep through the galaxy, compressing gas and the arms respond to this by forming stars.

The inner edge of the arms is pre-stellar. There are few stars here yet and the region is traced by their CO emissions, captured by ALMA and the JWST. Some of the interstellar medium is becoming compressed and is visible as dark streaks.

Within each arm is the active star formation region. The compressed gas collapses to form hot young stars, and the region also contains ionized nebulae, stellar clusters, protostars, and clusters still embedded in thick dust, made visible by the JWST.

The trailing edge is where star formation has fallen off. This is where we find older OB stars, stars that are drifting away from their birth clusters, and supernovae remnants and bubbles.

Outside of the main arms is where we find intermediate stars like F, G, and K stars. It’s also home to older red giants and AGB stars, along with old open clusters and diffuse gas. There are very few giant molecular star-forming clouds here.

*The ESA’s Picture of the Month comes from the JWST and its effort to understand all the complexity involved in star formation. In the nearby spiral galaxy NGC 5134, gas is recycled through hot and cold phases as it moves around the galaxy. The gas is compressed inside the spiral arms, where hot young stars form. The spiral arms don’t actually move, rather density waves move through the galaxy’s matter in a spiral pattern. Image Credit: ESA/Webb, NASA & CSA, A. Leroy*

This JWST Picture of the Month comes from observing program GO 3707. It’s focused on how gas moves around in galaxies, which is clearly an important part of star formation. The JWST gathered important information relevant to star formation, including detailed information on star clusters, the shape and form of the clouds that stars form in, the links between gas and dust in the interstellar medium, and how energetic newly-formed stars shape their surroundings.

Most galaxies are beyond the reach of even the JWST. The telescope can capture images of them, but rich scientific detail is only available for closer ones like NGC 5134 and the other spirals in PHANGS. What researchers learn from nearby galaxies can be applied to galaxies well out of reach, including the ones that fill the background of this Picture of the Month.

What we learn from these galaxies also helps us understand our own Milky Way galaxy. In some ways, it’s more challenging to understand because we’re inside of it.

The Milky Way is also a spiral, as far as we can tell, though some of the details are fuzzy. The star formation process is the same here as it is elsewhere, and is shaped by the spiral density waves. If we had a telescope far enough away, the Milky Way would likely appear every bit as glorious as NGC 5134 does.

Maybe somewhere out there in the cosmic expanse, another intelligent species like us, lacking in wisdom but technologically advanced, is gazing at our galaxy right now. Maybe they’re celebrating the Milky Way as an example of Nature’s creative power.

Or maybe not.