zoe hackshaw

🔭🧪🌏👇

The evolution of the spatial distribution of GES stars with different infall orbital energies. Please see the paper for the full caption.

Published in #MNRAS: "From order to chaos: the blurred out metallicity gradient of the Gaia-Enceladus/Sausage progenito", Carrillo et al. This is Fig. 4: please visit academic.oup.com/mnras/articl... to read the paper. @royalastrosoc.bsky.social @academic.oup.com

Top panel: two-dimensional number density of a sample of giants in Gaia DR3 crossmatched with APOGEE DR17 that spanned a Galactocentric range of 4-16 kpc (see text for details). The red dashed lines delimit the thick disc/bridge/low-α regions used to derive the kinematic properties in Table 2, while the excluded region for this derivation is shaded red. Middle panel: two-dimensional number density of star disc particles, as identif ied by GMM, in the [Mg/Fe] vs. [Fe/H] plane. Green, blue and purple mark the contours containing 90% of the high-α, bridge and low-α disc stars, respectively. Bottom panel: Mean age distribution of disc stars in the same plane, with the black contour enclosing the region containing 90% of the star particles in the disc. The last two panels show disc star particles at z ∼ 0.1.

Nicole’s second paper shows a Milky Way–mass FIRE-2 galaxy forms an α-bimodality without major mergers or strong radial migration! Dilution events and inside-out growth open the gap, hinting the Galaxy’s chemical split may stem from quiet evolution. arxiv.org/abs/2512.14897 🔭☄️

Thank you!!

Congratulations @theastrozo.bsky.social, on your paper!
It's always great to see a Gaia Data-related paper.
With the PISI team dedicated to it, this means a lot to us at UNIDIA.
It is especially meaningful here, given that P. Panuzzo, the main author and discoverer of BH3, is part of the team.

🥳 🔭 🧪 #astrosci

We find no chemical peculiarities in BH3*.

The chemical "normalcy” of this star is consistent with both formation theories for Gaia BH3, including dynamical capture and isolated binary evolution.

Many more systems of this kind are anticipated to be discovered with the coming release of Gaia DR4!

We show the observed spectrum of BH3* in black points with a synthetic spectrum fit to [Th/Fe] = 0.25 (pink) and a ±0.1 dex region around our fit (purple). A Th abundance of [Th/Fe]= −∞ is shown with the blue dashed line. We then fix an age of 13.4 Gyr (found with isochrones) and the H. Schatz et al. (2002) production ratio to solve for the [Th/Fe] needed, resulting in [Th/Fe] = 1.14 (green). We show that the Th abundance found using the probable age and production ratio cannot conceivably fit our observed data.

Some heavy elements decay on cosmological timescales. We use our upper limit on Th and Eu detection to try to age this star.

We get an age of 22.8 billion years. Considering the universe is about 13.6 billion yr old, this is pretty unlikely!

Sources for error include model assumptions (see paper)

The r-process pattern plot for BH3* (pink stars). Two scaled solar abundances are shown in gray (M. Asplund et al. 2009) and green (K. Lodders et al. 2025). The abundances from BH3* generally follow the universal pattern of the r-process and thorium is denoted as an upper limit with a black arrow.

It's pretty rare to encounter r-proc elements in metal-poor stars - only ~15% of halo stars are r-rpoc enhanced!

There is only 1 ED-2 star with an Eu abundance, but no chemical peculiarities there either.

Now for the last bit of this project: nuclear cosmo chronometry

Left: The observed spectrum of BH3* in black points, with a synthetic spectrum fit to an Eu abundance of [Eu/Fe] = 0.57 in pink and a ±0.1 dex region around this abundance (purple). Middle: The observed spectrum of the red giant in Gaia BH3 in black points, with a synthetic spectrum fit to a Th abundance of [Th/Fe] = 0.25 in pink and a ±0.1 dex region around this abundance (purple). This highlights the possibility of a Th detection at this line. Right: Observed spectrum (black points) compared to a synthesized spectrum with [U/Fe] ∼ −∞ (pink). Gray curves show synthetic spectra from [U/Fe] = −0.75 to 1.75 in 0.1 dex steps in the top panel, and the range of differences from the observed spectrum and synthetic spectra are shown in green in the bottom panel. No uranium feature is clearly detected. The nearby Fe I line at 3859.91 Å appears saturated, complicating the measurement of the U II 3859 Å line.

Now for the REALLY weird stuff, the heaviest elements. We try to derive rapid-neutron capture element abundances (r-proc), and we find that this star is mildly r-proc enhanced!

You can tell by the Eu abundance of [Eu/Fe] = 0.57. We report an upper limit for Th of [Th/Fe] < 0.25 but ... no Uranium😕

We repeat this for all of the elements we derived.

In all panels, we are looking to see how well the chemical abundances of Gaia BH3* (pink star) agree with other ED-2 stars (Dodd et al. 2025; pink squares).

No peculiarities so far in the light, alpha, Fe-peak or light n-cap elements!

Figure 3. A multipanel plot showing the Li (left), C (middle), and Na (right) abundances of BH3* (pink star) compared to the dSph Sculptor (blue triangles; D. Geisler et al. 2005), the UFD Reticulum II (upside-down purple triangles; A. P. Ji et al. 2016), BH3*’s host halo stream ED-2 (pink squares; E. Dodd et al. 2025), the GC M15 (green crosses; J. S. Sobeck et al. 2011), and other MW halo stars (gray circles; I. U. Roederer et al. 2014b). In all of the panels, [X/Fe] is on the y-axis, with the exception of the first panel which shows lithium in terms of absolute abundance. The dashed line at 0 represents the solar abundance of [X/Fe]. The left panel shows the Spite plateau annotated in purple, illustrating that BH3* lies well below the Spite plateau at A(Li) ∼ 2.2 dex (F. Spite & M. Spite 1982). We separate dwarf stars (triangles) and giant stars (squares) in the left panel to show that metal-poor dwarf stars make up the Spite plateau and giant stars have largely undergone the burning of their lithium. So far, the abundances of Gaia BH3* seem to align with other ED-2 stars!

We plot the abundances of Gaia BH3* to ask the question, how similar does it look to its neighbors?

Gaia BH3 is in a halo stream called ED-2. We know that stars that are born together should look similar, so are there any chemical peculiarities in Gaia BH3*?

Looking at the light elements, no!

We derived 29 chemical abundances of this star. This system likely formed from one of the following scenarios:

- Isolated Binary Evolution -- these objects were born together

or

- Dynamical Capture -- these objects were unassociated then became bound later

Chemistry may help solve this!

This figure shows four representative areas of the spectrum obtained using the Tull Coudé spectrograph on the 2.7m telescope at McDonald Observatory. We show in the four representative panels Ca II H & K, Hβ, the Mg I triplet, and the CH G band.

The red giant in this system is metal-poor ([Fe/H] = -2.27), alpha rich, and slightly r-process enhanced.

I obtained ~45 hours of observations on this star using the 2.7m telescope at McDonald Observatory to produce the highest SNR spectrum to date and search for some of the most elusive elements🔭

Figure 1. Similar to Figure 3 from Gaia Collaboration et al. (2024), the radial velocity evolution of Gaia BH3. A blue line shows the radial velocity evolution predicted by the Gaia combined binary model and the Gaia RVS epoch data are shown in black. We combine our RV points spanning 11 nights into three epochs (purple stars). Our RV observations agree quite well with the expected radial velocity evolution.

A red giant star orbiting a black hole 33 times the mass of our Sun... why? ... HOW?

In my most recent paper, we try to answer this question using chemistry. Follow along on a Detailed Chemical Analysis of the Red Giant Orbiting Gaia BH3: From Lithium to
Thorium➡️

iopscience.iop.org/article/10.3...

Long-term nuclear waste warning messages - Wikipedia

Idk if this is helpful but it looks like the exact inverse of long term nuclear waste warning message (see message section!): en.wikipedia.org/wiki/Long-te...

It's Friday, and apparently bluesky is ready for this fun revelation:

Dinosaurs lived on the other side the Galaxy.

A stellar density map of a barred spiral galaxy viewed face-on. The image shows a dark background with a central bright, elongated feature (the bar) surrounded by fainter spiral arms. The color bar on the right indicates the log10 Stellar Density in units of solar mass per square parsec, ranging from 0 (black/dark) to 4 (white/bright). The x and y axes are labeled in kpc (kiloparsecs), spanning from -10 to 10. Overlaid on the image are several highlighted regions: a central white, bright feature is enclosed by a dashed cyan ellipse representing the full Bar region. A smaller, cyan dashed box labeled Inner-bar is located along the bar's major axis, excluding the ends. Two symmetrically placed, dashed teal boxes labeled Bar-ends are located near the extremities of the bar. This visualization highlights the key components of the galaxy's bar structure.

a NEW PAPER led the incomparable Dr. Elizabeth Iles (accepted by PASA) quantifies how astronomers might be biased in how they judge galactic bars

Turns out that male astronomers are consistently more optimistic than their peers when it comes to measuring length

arxiv.org/abs/2511.09908

#astro

High-stakes exams inflate a gender gap and contribute to systematic grading errors in one introductory physics series A study in introductory physics suggests high-stakes exams are causing a gender gap, rather than measuring it.

Proud of the work I published with @djphysicswebb.bsky.social . Gender Gap in intro physics is eliminated when employing retake exams because women do better on the FIRST try - suggesting exam STAKES (not differences in preparation/understanding) explain gender gap. 🧪 link.aps.org/doi/10.1103/...

This is why we fund scientists to study things like oyster slobber even if you don’t think it sounds important

‘Completely shattered.’ Changes to NSF’s graduate student fellowship spur outcry The announcement comes months later than usual, leaving many would-be applicants stranded

Science news article about 2nd year grad students being unceremoniously dropped from the GRFP eligibility with no explanation or warning:
www.science.org/content/arti...

Cecilia Payne-Gaposchkin ✨ figured out what stars are made of ✨ when she was just 25. 🔭🧪

Her PhD thesis basically established the Harvard astro department — at a time when Harvard didn't officially allow woman students.

I wrote this little profile to mark the 100th anniversary of her thesis:

https://pubmed.ncbi.nlm.nih.gov/30922800/

Funding science is very important for a lot of reasons. One of those reasons is that you get papers like this

the semester is starting! here are some of my teaching resources online:

intro astronomy animations: zingale.github.io/astro_animat...

my computational astrophysics class: zingale.github.io/computationa...

my computational hydro text: open-astrophysics-bookshelf.github.io/numerical_ex...

#astro

finished project hail mary by andy weir! i loved it! &as someone that doesn’t consume astrophysical fiction ✨

“Do you believe in God? […] I think He was pretty awesome to make relativity a thing […] The faster you go, the less time you experience. It’s like He’s inviting us to explore the universe”

An infographic titled "How BIG are the BLACK HOLES we find with GRAVITATIONAL WAVES?" by @astronerdika. The graphic displays a range of black hole masses detected via gravitational waves, categorized by their size in solar masses (mass of the Sun) and represented with playful cat-like black hole illustrations. The categories from left to right are: 1. "<5 times the mass of the Sun" - Labeled "smol" - Very small black hole illustration represented by a curled up black cat - Arrow pointing left: "THIS WAY TO NEUTRON STARS" - Example: "Big component of GW230529 (~3.6 times the mass of the Sun)" 2. "~10 times the mass of the Sun" - Labeled "basic" - Slightly larger black hole cat illustration - Caption: "LOTS OF BLACK HOLES" 3. "~35–45 times the mass of the Sun" - Labeled "hefty" - Bigger black hole cat illustration - Continues the idea of a populated range 4. ">60 times the mass of the Sun" - Labeled "chonky" - Large black hole cat illustration - Caption: "FORBIDDEN TERRITORY? (can these even be made from the collapse of star cores?!)" - Example: "Components of GW190521 (~85 + ~66 times the mass of the Sun)" 5. ">100 times the mass of the Sun" - Labeled "oh lawd" - Very large, curled-up black hole cat illustration - Arrow pointing right: "THIS WAY TO INTERMEDIATE MASS BLACK HOLES" - Example: "Components of GW231123 (~137 + ~103 times the mass of the Sun)" Below the categories is a stylized black curve representing the inferred population of black holes detected by LIGO-Virgo-KAGRA. It rises sharply in the "basic" range and falls off toward the "hefty" and "chonky" ranges, with a note reading: "this curve is an artistic representation of the black hole population inferred by LIGO-Virgo-KAGRA." This infographic draws from the “Chonky Cat” meme.

Heard the latest news from the LIGO-Virgo-KAGRA collaboration? We detected the collision of the most massive pair of black holes so far: #GW231123 weighing in at ~137 + ~103 times the mass of the Sun!

So to celebrate, here’s a handy chart ✨

Just how chonky are these black holes? 🤔

Kickin’ It Into Overdrive With Stellar Escapees Follow along as we zoom through the stars with these hypervelocity stellar survivors and uncover their explosive origins.

From Mckenzie Ferrari: Follow along as we zoom through the stars with these hypervelocity stellar survivors and uncover their explosive origins. 🔭✨☄️
astrobites.org/2025/07/22/h...

Sloan Digital Sky Survey-V: Pioneering Panoptic Spectroscopy The Sloan Digital Sky Survey-V (SDSS-V) is pioneering panoptic spectroscopy: it is the first all-sky, multi-epoch, optical-to-infrared spectroscopic survey. SDSS-V is mapping the sky with multi-object...

Today is a big day for us: it's DATA RELEASE DAY!!! And to celebrate our nineteenth data release, we have not one, but two papers for you to read all about our data: we have a DR19 paper (arxiv.org/abs/2507.07093) and an SDSS-V Overview paper (arxiv.org/abs/2507.06989) #DR19

Looking for a single stellar ancestor: Mono-enriched stars in zoom-in simulations Today's bite explores if we'll be able to find a star that has formed from the gas enriched by only one stellar predecessor, an interesting way to probe what's actually happening in stellar nucleosynt...

From Caroline von Raesfeld: Today’s bite explores if we’ll be able to find a star that has formed from the gas enriched by only one stellar predecessor, an interesting way to probe what’s actually happening in stellar nucleosynthesis. 🔭✨☄️
astrobites.org/2025/07/08/l...

‘One of the true final frontiers’ — Sally Ride biopic highlights the struggle of gay astronauts The first US woman to fly in space said little about her personal life in public. A candid film discloses the pressures she endured.

NASA is erasing much of its progress towards inclusivity — a shameful change that goes against everything astronaut and astrophysicist Sally Ride worked for. My review of the new biopic SALLY, for @nature.com:

www.nature.com/articles/d41...

🧪🚀👩‍🚀🏳️‍🌈