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Webb Telescope observes a globular cluster sparkling with separate stars – Phys.org

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Image of the globular cluster M92 captured by the James Webb Space Telescope’s NIRCam instrument. The black strip in the center is a chip gap, the result of the separation between NIRCam’s two long-wavelength detectors. The gap covers the dense center of the cluster, which is too bright to capture at the same time as the fainter, less dense outskirts of the cluster. This image is a composite of four exposures using four different filters: F090W (0.9 microns in wavelength) is shown in blue; F150W (1.5 microns) in cyan; F277W (2.77 microns) in yellow; and F444W (4.44 microns) in red. The image is about 5 arcminutes (39 light-years) across. Credit: NASA, ESA, CSA, A. Pagan (STScI).

On June 20, 2022, the James Webb Space Telescope spent just over one hour staring at Messier 92 (M92), a globular cluster 27,000 light-years away in the Milky Way halo. The observation—among the very first science observations undertaken by Webb—is part of Early Release Science (ERS) program 1334, one of 13 ERS programs designed to help astronomers understand how to use Webb and make the most of its scientific capabilities.

NASA spoke with Matteo Correnti from the Italian Space Agency; Alessandro Savino from the University of California, Berkeley; Roger Cohen from Rutgers University; and Andy Dolphin from Raytheon Technologies to find out more about Webb’s observations of M92 and how the team is using the data to help other astronomers. (Last November, Kristen McQuinn talked with NASA about her work on the dwarf galaxy WLM, which is also part of this program.)

Tell us about this ERS program. What are you trying to accomplish?

Alessandro Savino: This particular program is focused on resolved stellar populations. These are large groups of stars like M92 that are very nearby—close enough that Webb can single out the individual stars in the system. Scientifically, observations like these are very exciting because it is from our cosmic neighborhood that we learn a lot of the physics of stars and galaxies that we can translate to objects that we see much farther away.

Matteo Correnti: We’re also trying to understand the telescope better. This project has been instrumental for improving the calibration (making sure all of the measurements are as accurate as possible), for improving the data for other astronomers and other similar projects.

Why did you decide to look at M92 in particular?

Savino: Globular clusters like M92 are very important for our understanding of stellar evolution. For decades they have been a primary benchmark for understanding how stars work, how stars evolve. M92 is a classic globular cluster. It’s close by; we understand it relatively well; it’s one of our references in studies of stellar evolution and stellar systems.

Correnti: Another reason M92 is important is because it is one of the oldest in the Milky Way, if not the oldest one. We think M92 is between 12 and 13 billion years old. It contains some of the oldest stars that we can find, or at least that we can resolve and characterize well. We can use nearby clusters like this as tracers of the very ancient universe.

Roger Cohen: We also chose M92 because it is very dense: There are a lot of stars packed together very closely. (The center of the cluster is thousands of times denser than the region around the sun.) Looking at M92 allows us to test how Webb performs in this particular regime, where we need to make measurements of stars that are very close together.

What are the characteristics of a globular cluster that make it useful for studying how stars evolve?

Andy Dolphin: One of the main things is that the bulk of the stars in M92 would have formed at roughly the same time and with roughly the same mix of elements, but with a wide range of masses. So we can get a really good survey of this particular population of stars.

Savino: Also, since the stars all belong to the same object (the same globular cluster, M92), we know they are all about the same distance away from us. That helps us a lot because we know that differences in brightness between the different stars must be intrinsic, instead of just related to how far away they are. It makes the comparison with models much, much easier.

Webb Observes a Globular Cluster Sparkling with Separate Stars
Detail of the globular cluster M92 captured by Webb’s NIRCam instrument. This field of view covers the lower left quarter of the right half of the full image. Globular clusters are dense masses of tightly packed stars that all formed around the same time. In M92, there are about 300,000 stars packed into a ball about 100 light-years across. The night sky of a planet in the middle of M92 would shine with thousands of stars that appear thousands of times brighter than those in our own sky. The image shows stars at different distances from the center, which helps astronomers understand the motion of stars in the cluster, and the physics of that motion. Credit: NASA, ESA, CSA, A. Pagan (STScI).

This star cluster has already been studied with the Hubble Space Telescope and other telescopes. What can we see with Webb that we have not seen already?

Cohen: One of the important differences between Webb and Hubble is that Webb operates at longer wavelengths, where very cool, low-mass stars give off most of their light. Webb is well-designed to observe very . We were actually able to reach down to the lowest mass stars—stars less than 0.1 times the mass of the sun. This is interesting because this is very close to the boundary where stars stop being stars. (Below this boundary are brown dwarfs, which are so low-mass that they’re not able to ignite hydrogen in their cores.)

Correnti: Webb is also a lot faster. To see the very faint low-mass stars with Hubble, you need hundreds of hours of telescope time. With Webb, it takes just a few hours.

Cohen: These observations weren’t actually designed to push very hard on the limits of the telescope. So it’s very encouraging to see that we were still able to detect such small, faint stars without trying really, really hard.

What’s so interesting about these low-mass stars?

Savino: First of all, they are the most numerous stars in the universe. Second, from a theoretical point of view, they are very interesting because they’ve always been very difficult to observe and characterize. Especially stars less than half the mass of the sun, where our current understanding of stellar models is a little more uncertain.

Correnti: Studying the light these emit can also help us better constrain the age of the globular cluster. That helps us better understand when different parts of the Milky Way (like the halo, where M92 is located) formed. And that has implications for our understanding of cosmic history.

It looks like there’s big gap in the middle of the image you captured. What is that and why is it there?

Dolphin: This image was made using Webb’s Near-Infrared Camera (NIRCam). NIRCam has two modules, with a “chip gap” between the two. The center of the cluster is extremely crowded, extremely bright. So that would have limited the usefulness of the data from that region. The position of these images overlaps nicely with Hubble data available already.

One of your main goals was to provide tools for other scientists. What are you particularly excited about?

Dolphin: One of the key resources we developed and have made available to the astronomical community is something called the DOLPHOT NIRCam module. This works with an existing piece of software used to automatically detect and measure the brightness of stars and other unresolved objects (things with a star-like appearance). This was developed for cameras on Hubble. Adding this module for NIRCam (as well as one for NIRISS, another of Webb’s instruments) allows astronomers the same analysis procedure they know from Hubble, with the additional benefit of now being able to analyze Hubble and Webb data in a single pass to get combined-telescope star catalogs.

Savino: This is a really big community service component. It’s helpful for everyone. It’s making analysis much easier.

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Webb Telescope observes a globular cluster sparkling with separate stars (2023, February 22)
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Las Vegas Aces Rookie Kate Martin Suffers Ankle Injury in Game Against Chicago Sky

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Las Vegas Aces rookie Kate Martin had to be helped off the floor and taken to the locker room after suffering an apparent ankle injury in the first quarter of Tuesday night’s game against the Chicago Sky.

Late in the first quarter, Martin was pushing the ball up the court when she appeared to twist her ankle and lost her balance. The rookie was in serious pain, lying on the floor before eventually being helped off. Her entire team came out in support, and although she managed to put some pressure on the leg, she was taken to the locker room for further evaluation.

Martin returned to the team’s bench late in the second quarter but was ruled out for the remainder of the game.

“Kate Martin is awesome. Kate Martin picks up things so quickly, she’s an amazing sponge,” Aces guard Kelsey Plum said of the rookie during the preseason. “I think (coach) Becky (Hammon) nicknamed her Kate ‘Money’ Martin. I think that’s gonna stick. And when I say ‘money,’ it’s not just about scoring and stuff, she’s just in the right place at the right time. She just makes people better. And that’s what Becky values, that’s what our coaching staff values and that’s why she’s gonna be a great asset to our team.”

Las Vegas selected Martin in the second round of the 2024 WNBA Draft. She was coming off the best season of her collegiate career at Iowa, where she averaged 13.1 points, 6.8 rebounds, and 2.3 assists per game during the 2023-24 campaign. Martin’s integration into the Aces organization has been seamless, with her quickly earning the respect and admiration of her teammates and coaches.

The team and fans alike are hoping for a speedy recovery for Martin, whose contributions have been vital to the Aces’ performance this season.

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Asteroid Apophis will visit Earth in 2029, and this European satellite will be along for the ride

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The European Space Agency is fast-tracking a new mission called Ramses, which will fly to near-Earth asteroid 99942 Apophis and join the space rock in 2029 when it comes very close to our planet — closer even than the region where geosynchronous satellites sit.

Ramses is short for Rapid Apophis Mission for Space Safety and, as its name suggests, is the next phase in humanity’s efforts to learn more about near-Earth asteroids (NEOs) and how we might deflect them should one ever be discovered on a collision course with planet Earth.

In order to launch in time to rendezvous with Apophis in February 2029, scientists at the European Space Agency have been given permission to start planning Ramses even before the multinational space agency officially adopts the mission. The sanctioning and appropriation of funding for the Ramses mission will hopefully take place at ESA’s Ministerial Council meeting (involving representatives from each of ESA’s member states) in November of 2025. To arrive at Apophis in February 2029, launch would have to take place in April 2028, the agency says.

This is a big deal because large asteroids don’t come this close to Earth very often. It is thus scientifically precious that, on April 13, 2029, Apophis will pass within 19,794 miles (31,860 kilometers) of Earth. For comparison, geosynchronous orbit is 22,236 miles (35,786 km) above Earth’s surface. Such close fly-bys by asteroids hundreds of meters across (Apophis is about 1,230 feet, or 375 meters, across) only occur on average once every 5,000 to 10,000 years. Miss this one, and we’ve got a long time to wait for the next.

When Apophis was discovered in 2004, it was for a short time the most dangerous asteroid known, being classified as having the potential to impact with Earth possibly in 2029, 2036, or 2068. Should an asteroid of its size strike Earth, it could gouge out a crater several kilometers across and devastate a country with shock waves, flash heating and earth tremors. If it crashed down in the ocean, it could send a towering tsunami to devastate coastlines in multiple countries.

Over time, as our knowledge of Apophis’ orbit became more refined, however, the risk of impact  greatly went down. Radar observations of the asteroid in March of 2021 reduced the uncertainty in Apophis’ orbit from hundreds of kilometers to just a few kilometers, finally removing any lingering worries about an impact — at least for the next 100 years. (Beyond 100 years, asteroid orbits can become too unpredictable to plot with any accuracy, but there’s currently no suggestion that an impact will occur after 100 years.) So, Earth is expected to be perfectly safe in 2029 when Apophis comes through. Still, scientists want to see how Apophis responds by coming so close to Earth and entering our planet’s gravitational field.

“There is still so much we have yet to learn about asteroids but, until now, we have had to travel deep into the solar system to study them and perform experiments ourselves to interact with their surface,” said Patrick Michel, who is the Director of Research at CNRS at Observatoire de la Côte d’Azur in Nice, France, in a statement. “Nature is bringing one to us and conducting the experiment itself. All we need to do is watch as Apophis is stretched and squeezed by strong tidal forces that may trigger landslides and other disturbances and reveal new material from beneath the surface.”

The Goldstone radar’s imagery of asteroid 99942 Apophis as it made its closest approach to Earth, in March 2021. (Image credit: NASA/JPL–Caltech/NSF/AUI/GBO)

By arriving at Apophis before the asteroid’s close encounter with Earth, and sticking with it throughout the flyby and beyond, Ramses will be in prime position to conduct before-and-after surveys to see how Apophis reacts to Earth. By looking for disturbances Earth’s gravitational tidal forces trigger on the asteroid’s surface, Ramses will be able to learn about Apophis’ internal structure, density, porosity and composition, all of which are characteristics that we would need to first understand before considering how best to deflect a similar asteroid were one ever found to be on a collision course with our world.

Besides assisting in protecting Earth, learning about Apophis will give scientists further insights into how similar asteroids formed in the early solar system, and, in the process, how  planets (including Earth) formed out of the same material.

One way we already know Earth will affect Apophis is by changing its orbit. Currently, Apophis is categorized as an Aten-type asteroid, which is what we call the class of near-Earth objects that have a shorter orbit around the sun than Earth does. Apophis currently gets as far as 0.92 astronomical units (137.6 million km, or 85.5 million miles) from the sun. However, our planet will give Apophis a gravitational nudge that will enlarge its orbit to 1.1 astronomical units (164.6 million km, or 102 million miles), such that its orbital period becomes longer than Earth’s.

It will then be classed as an Apollo-type asteroid.

Ramses won’t be alone in tracking Apophis. NASA has repurposed their OSIRIS-REx mission, which returned a sample from another near-Earth asteroid, 101955 Bennu, in 2023. However, the spacecraft, renamed OSIRIS-APEX (Apophis Explorer), won’t arrive at the asteroid until April 23, 2029, ten days after the close encounter with Earth. OSIRIS-APEX will initially perform a flyby of Apophis at a distance of about 2,500 miles (4,000 km) from the object, then return in June that year to settle into orbit around Apophis for an 18-month mission.

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Furthermore, the European Space Agency still plans on launching its Hera spacecraft in October 2024 to follow-up on the DART mission to the double asteroid Didymos and Dimorphos. DART impacted the latter in a test of kinetic impactor capabilities for potentially changing a hazardous asteroid’s orbit around our planet. Hera will survey the binary asteroid system and observe the crater made by DART’s sacrifice to gain a better understanding of Dimorphos’ structure and composition post-impact, so that we can place the results in context.

The more near-Earth asteroids like Dimorphos and Apophis that we study, the greater that context becomes. Perhaps, one day, the understanding that we have gained from these missions will indeed save our planet.

 

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McMaster Astronomy grad student takes a star turn in Killarney Provincial Park

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Astronomy PhD candidate Veronika Dornan served as the astronomer in residence at Killarney Provincial Park. She’ll be back again in October when the nights are longer (and bug free). Dornan has delivered dozens of talks and shows at the W.J. McCallion Planetarium and in the community. (Photos by Veronika Dornan)

Veronika Dornan followed up the April 8 total solar eclipse with another awe-inspiring celestial moment.

This time, the astronomy PhD candidate wasn’t cheering alongside thousands of people at McMaster — she was alone with a telescope in the heart of Killarney Provincial Park just before midnight.

Dornan had the park’s telescope pointed at one of the hundreds of globular star clusters that make up the Milky Way. She was seeing light from thousands of stars that had travelled more than 10,000 years to reach the Earth.

This time there was no cheering: All she could say was a quiet “wow”.

Dornan drove five hours north to spend a week at Killarney Park as the astronomer in residence. part of an outreach program run by the park in collaboration with the Allan I. Carswell Observatory at York University.

Dornan applied because the program combines her two favourite things — astronomy and the great outdoors. While she’s a lifelong camper, hiker and canoeist, it was her first trip to Killarney.

Bruce Waters, who’s taught astronomy to the public since 1981 and co-founded Stars over Killarney, warned Dornan that once she went to the park, she wouldn’t want to go anywhere else.

The park lived up to the hype. Everywhere she looked was like a painting, something “a certain Group of Seven had already thought many times over.”

The dome telescopes at Killarney Provincial Park.

She spent her days hiking the Granite Ridge, Crack and Chikanishing trails and kayaking on George Lake.  At night, she went stargazing with campers — or at least tried to. The weather didn’t cooperate most evenings — instead of looking through the park’s two domed telescopes, Dornan improvised and gave talks in the amphitheatre beneath cloudy skies.

Dornan has delivered dozens of talks over the years in McMaster’s W.J. McCallion Planetarium and out in the community, but “it’s a bit more complicated when you’re talking about the stars while at the same time fighting for your life against swarms of bugs.”

When the campers called it a night and the clouds parted, Dornan spent hours observing the stars. “I seriously messed up my sleep schedule.”

She also gave astrophotography a try during her residency, capturing images of the Ring Nebula and the Great Hercules Cluster.

A star cluster image by Veronika Dornan

“People assume astronomers take their own photos. I needed quite a lot of guidance for how to take the images. It took a while to fiddle with the image properties, but I got my images.”

Dornan’s been invited back for another week-long residency in bug-free October, when longer nights offer more opportunities to explore and photograph the final frontier.

She’s aiming to defend her PhD thesis early next summer, then build a career that continues to combine research and outreach.

“Research leads to new discoveries which gives you exciting things to talk about. And if you’re not connecting with the public then what’s the point of doing research?”

 

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