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"Farthest galaxy ever" HD1 is probably not what it seems

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An exciting potential discovery has recently rocked the world of astrophysics.

Artist’s logarithmic scale conception of the observable universe. The Solar System gives way to the Milky Way, which gives way to nearby galaxies which then give way to the large-scale structure and the hot, dense plasma of the Big Bang at the outskirts. Each line-of-sight that we can observe contains all of these epochs, but the quest for the most distant observed object will not be complete until we’ve mapped out the entire Universe.

(Credit: Pablo Carlos Budassi; Unmismoobjetivo/Wikimedia Commons)

This galaxy, HD1, was just announced as the youngest, most distant galaxy ever seen.

farthest galaxy

Shown here with purple arrows, this tiny red object, barely able to be seen without pointers to it, may represent the most distant object presently known in the Universe: HD1. However, its distance has yet to be definitively determined.

(Credit: Harikane et al.)

Possessing an age of 330 million years, it’s presently 33 billion light-years away: the farthest ever seen.

unreachable

The light from any galaxy that was emitted after the start of the hot Big Bang, 13.8 billion years ago, would have reached us by today so long as it’s within about 46.1 billion light-years at present. But the light from the earliest, most distant galaxies will be blocked by intervening matter and redshifted by the expanding Universe. Both represent severe challenges to detection, and pose cautionary tales against us drawing definitive conclusions about their distance without the proper, necessary data.

(Credit: F. Summers, A. Pagan, L. Hustak, G. Bacon, Z. Levay, and L. Frattere (STScI))

This could break the old record of GN-z11: 407 million years old and 32 billion light-years distant.

most distant

A section of the GOODS-N field, which contains the galaxy GN-z11, the most distant galaxy ever observed. At a redshift of 11.1, a distance of 32.1 billion light-years, and an inferred age of the Universe of 407 million light-years at the time this light was emitted, this is the farthest back we’ve ever seen a luminous object in the Universe. Hubble’s spectroscopic confirmation was key; without it, we should have remained skeptical.

(Credit: NASA, ESA, G. Bacon (STScI), A. Feild (STScI), P. Oesch (Yale))

If so, it’s a fascinating find: bright, luminous, and possibly home to the first truly pristine stars.

The very first stars and galaxies that form should be home to Population III stars: stars made out of only the elements that first formed during the hot Big Bang, which is 99.999999% hydrogen and helium exclusively. Such a population has never been seen or confirmed, but some are hopeful that HD1 will contain them.

(Credit: Pablo Carlos Budassi/Wikimedia Commons)

But there’s an excellent chance that HD1 is not the record-breaker it’s widely reported to be.

Although there are magnified, ultra-distant, very red and even infrared galaxies like the ones identified here in the Hubble eXtreme Deep Field, many of these candidate galaxies have turned out to be either intrinsically red and/or closer interlopers, not the ultra-distant objects we hoped they were. Without spectroscopic confirmation, fooling ourselves as to an object’s cosmic distance is an unfortunate, but commonplace occurrence.

(Credit: NASA, ESA, R. Bouwens and G. Illingsworth (UC, Santa Cruz))

Yes, it’s extremely red in color, missing all of its short-wavelength light.

farthest galaxy

This figure shows various photometric filters (top) and the images of HD1 that they do or do not reveal, as well as two different fits to the photometric data. Note that even though the high-redshift fit is superior, there is no spectroscopic confirmation of the galaxy HD1’s distance at all.

(Credit: Y. Harikane et al., ApJ, 2022)

Only the longest-wavelength photometric filters reveal the object at all.

farthest galaxy

Before a sufficient number of stars form, neutral atoms persist in the intergalactic medium of the Universe, where they are remarkably efficient at blocking ultraviolet and visible light starlight. Without spectroscopic confirmation, like we have for GN-z11 but not HD1, caution should be warranted.

(Credit: Harikane et al., NASA, EST and P. Oesch/Yale)

This is consistent with an object behind the “wall of neutral atoms” prior to reionization.

reionization

Schematic diagram of the Universe’s history, highlighting reionization. Before stars or galaxies formed, the Universe was full of light-blocking, neutral atoms. Most of the Universe doesn’t become reionized until 550 million years afterwards, with some regions achieving full reionization earlier and others later. The first major waves of reionization begin happening at around 250 million years of age, while a few fortunate stars may form just 50-to-100 million years after the Big Bang. With the right tools, like the James Webb Space Telescope, we may begin to reveal the earliest galaxies.

(Credit: S. G. Djorgovski et al., Caltech; Caltech Digital Media Center)

But only spectroscopy can determine a galaxy’s redshift with absolute certainty.

Only by breaking the light from a distant object up into its component wavelengths and by identifying the signature of atomic or ionic electron transitions that can be linked to a redshift, and hence, the expanding Universe, can a confident redshift (and hence, distance) be arrived at. That evidence is lacking for HD1 and HD2 today.

(Credit: Vesto Slipher, 1917, Proc. Amer. Phil. Soc.)

Multiple spectral lines, linked to quantum transitions, reveal how severely emitted light is redshifted by the expanding Universe.

expanding universe

This simplified animation shows how light redshifts and how distances between unbound objects change over time in the expanding Universe. Only by linking the wavelength of the emitted light to the observed light can the redshift truly be measured with confidence.

(Credit: Rob Knop)

For HD1, only one candidate line exists, and its detection significance is below the 5-σ threshold.

In the entirety of the spectra taken by our most powerful observatories, including ALMA, of galaxy HD1, only one tentative signature for a line emerges: for a doubly-ionized oxygen line. Its confidence does not rise to the “gold standard” required to announce a discovery.

(Credit: Y. Harikane et al., ApJ, 2022)

The “other” distant candidate, HD2, possesses no spectral lines at all.

The exposures in different photometric bands (top) of candidate galaxy HD2, along with two possible spectral fits (curves) to the data points (red). Note how although a high redshift (z = 12) solution is favored over a low redshift (z = 3.5) interpretation, both are possible, and the unambiguous signature from spectroscopy is not available.

(Credit: Y. Harikane et al., ApJ, 2022)

Until spectroscopic confirmation arrives, caution is mandated, as no distances can be decisively determined.

The full published spectrum of candidate galaxy HD1 shows no definitive spectral line detections at all. The red arrow corresponds to the candidate signal of a doubly ionized oxygen line. Without decisive data, we cannot responsibly conclude that this is, in fact, the farthest galaxy we’ve ever seen. It might not be anything like that at all.

(Credit: Y. Harikane et al., ApJ, 2022)

Mostly Mute Monday tells an astronomical story in images, visuals, and no more than 200 words. Talk less; smile more.

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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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