Why the Poles Matter

At first glance, the Sun’s poles seem calm compared to the active mid-latitudes around ±35°, where sunspots, solar flares, and coronal mass ejections (CMEs) dominate. But appearances are deceiving. The magnetic fields at the poles are vital to the Sun’s global dynamo process and may act as “seed fields” that shape the next solar cycle, defining the overall solar magnetic structure. Data from the Ulysses spacecraft showed that the fast solar wind originates mainly from vast coronal holes near the poles. Understanding these regions is therefore key to answering three of the most important questions in solar physics:

1. How does the solar dynamo operate and drive the magnetic cycle?

The Sun’s magnetic cycle is a repeating pattern that lasts about 11 years, marked by fluctuations in sunspot numbers and a complete reversal of the Sun’s magnetic poles. This process is driven by a complex dynamo mechanism powered by the Sun’s internal motion. Differential rotation produces magnetic activity, while meridional circulation carries magnetic flux toward the poles. However, decades of helioseismic studies have revealed conflicting information about how these flows behave deep inside the convection zone. Some evidence even points to poleward flows at the base of the zone, challenging traditional dynamo theories. Observations from high latitudes are needed to clarify these internal flow patterns and refine existing models.

2. What powers the fast solar wind?

The fast solar wind — a supersonic stream of charged particles — originates mainly in the Sun’s polar coronal holes and fills most of the heliosphere, shaping conditions in interplanetary space. Yet scientists still do not fully understand how it begins. Does it emerge from dense plumes inside the coronal holes, or from the more diffuse regions between them? Are magnetic reconnection events, wave interactions, or both responsible for accelerating the flow? Only direct imaging of the poles and in-situ measurements can resolve these long-standing questions.

3. How do space weather events spread through the solar system?

Space weather refers to changes in the solar wind and solar eruptions that disturb the space environment. Extreme events such as powerful flares and CMEs can trigger geomagnetic and ionospheric storms on Earth, creating dazzling auroras but also threatening satellites, communication systems, and power grids. To improve forecasts, researchers must follow how solar material and magnetic structures evolve across the Sun and through space, not just from the limited perspective of Earth’s orbital plane. Observing from outside the ecliptic would provide a crucial top-down view, helping scientists trace how CMEs and other disturbances travel through the solar system.

Past Efforts

Scientists have long recognized the importance of solar polar observations. The Ulysses mission, launched in 1990, was the first spacecraft to leave the ecliptic plane and sample the solar wind over the poles. Its in-situ instruments confirmed key properties of the fast solar wind but lacked imaging capability. More recently, the European Space Agency’s Solar Orbiter has been gradually moving out of the ecliptic plane and is expected to reach latitudes of around 34° in a few years. While this represents a remarkable progress, it still falls far short of the vantage needed for a true polar view.

A number of ambitious mission concepts have been proposed over the past decades, including the Solar Polar Imager (SPI), the POLAR Investigation of the Sun (POLARIS), the Solar Polar ORbit Telescope (SPORT), the Solaris mission, and the High Inclination Solar Mission (HISM). Some envisioned using advanced propulsion such as solar sails to reach high inclinations. Others relied on gravity assists to incrementally tilt their orbits. Each of these missions would carry both remote-sensing and in-situ instruments to image the Sun’s poles and measure key physical parameters above the poles.

The SPO Mission

The Solar Polar-orbit Observatory (SPO) is designed specifically to overcome the limitations of past and current missions. Scheduled for launch in January 2029, SPO will use a Jupiter gravity assist (JGA) to bend its trajectory out of the ecliptic plane. After several Earth flybys and a carefully planned encounter with Jupiter, the spacecraft will settle into a 1.5-year orbit with a perihelion of about 1 AU and an inclination of up to 75°. In its extended mission, SPO could climb to 80°, offering the most direct view of the poles ever achieved.

The 15-year lifetime of the mission (including an 7-year extended mission period) will allow it to cover both solar minimum and maximum, including the crucial period around 2035 when the next solar maximum and expected polar magnetic field reversal will occur. During the whole lifetime, SPO will repeatedly pass over both poles, with extended high-latitude observation windows lasting more than 1000 days.

The SPO mission aims at breakthroughs on the three scientific questions mentioned above. To meet its ambitious objectives, SPO will carry a suite of several remote-sensing and in-situ instruments. Together, they will provide a comprehensive view of the Sun’s poles. The remote-sensing instruments include the Magnetic and Helioseismic Imager (MHI) to measure magnetic fields and plasma flows at the surface, the Extreme Ultraviolet Telescope (EUT) and the X-ray Imaging Telescope (XIT) to capture dynamic events in the solar upper atmosphere, the VISible-light CORonagraph (VISCOR) and the Very Large Angle CORonagraph (VLACOR) to track the solar corona and solar wind streams out to 45 solar radii (at 1 AU). The in-situ package includes a magnetometer and particle detectors to sample the solar wind and interplanetary magnetic field directly. By combining these observations, SPO will not only capture images of the poles for the first time but also connect them to the flows of plasma and magnetic energy that shape the heliosphere.

SPO will not operate in isolation. It is expected to work in concert with a growing fleet of solar missions. These include the STEREO Mission, the Hinode satellite, the Solar Dynamics Observatory (SDO), the Interface Region Imaging Spectrograph (IRIS), the Advanced Space-based Solar Observatory (ASO-S), the Solar Orbiter, the Aditya-L1 mission, the PUNCH mission, as well as the upcoming L5 missions (e.g., ESA’s Vigil mission and China’s LAVSO mission). Together, these assets will form an unprecedented observational network. SPO’s polar vantage will provide the missing piece, enabling nearly global 4π coverage of the Sun for the first time in human history.

Looking Ahead

The Sun is our nearest star, yet much about it remains unknown. The upcoming Solar Polar-orbit Observatory (SPO) mission is expected to change that by giving scientists an unprecedented look at the Sun’s polar regions. These areas, which have long been hidden from direct view, will soon be observed in detail, offering new insight into the forces that shape our star and sustain life on Earth.

The importance of SPO goes far beyond pure scientific curiosity. By improving knowledge of the solar dynamo, the mission could lead to more accurate predictions of the solar cycle and, in turn, more reliable space weather forecasts. Understanding how the fast solar wind forms and behaves will also refine models of the heliosphere, which is vital for spacecraft engineering and astronaut safety. Most significantly, advances in tracking solar activity could strengthen our ability to safeguard critical technologies, including navigation and communication satellites, aviation systems, and power grids on Earth.

OJ 287 is classified as a blazar, a type of active galaxy known for its intense energy and brightness. At its heart lies a supermassive black hole that draws in matter from nearby space and propels some of it outward in colossal plasma jets filled with radiation, heat, magnetic fields, and heavy particles. “We have never before observed a structure in the OJ 287 galaxy at the level of detail seen in the new image,” said Dr. Traianou, a postdoctoral researcher working with Dr. Roman Gold at Heidelberg University’s Interdisciplinary Center for Scientific Computing.

The image penetrates deeply into the galaxy’s center, revealing a sharply bent, ribbon-like jet structure and providing clues about the plasma’s composition and motion. Some areas reach temperatures of around ten trillion degrees Kelvin, showing just how much energy is being released near the black hole. The scientists also detected a new shock wave forming and colliding along the jet, which they linked to trillion-electron-volt energy levels observed in an unusual gamma-ray signal detected in 2017.

To obtain this remarkable view, the researchers used a ground-space radio interferometer that combined a radio telescope in Earth’s orbit (the ten-meter antenna of the RadioAstron mission aboard the Spektr-R satellite) with 27 ground-based observatories around the world. By linking signals from these observatories, they effectively created a virtual telescope five times wider than Earth’s diameter. The extraordinary resolution of the resulting image comes from measuring how light waves overlap, taking full advantage of the wave properties of light itself.

The interferometric image underpins the assumption that a binary supermassive black hole is located inside galaxy OJ 287. It also provides important information on how the movements of such black holes influence the form and orientation of the plasma jets emitted. “Its special properties make the galaxy an ideal candidate for further research into merging black holes and the associated gravitational waves,” states Efthalia Traianou.

Institutions from Germany, Italy, Russia, Spain, South Korea, and the US all contributed to the research. It was supported by various research and funding institutions. The research results were published in the journal Astronomy & Astrophysics.

“Supermassive dark stars are extremely bright, giant, yet puffy clouds made primarily out of hydrogen and helium, which are supported against gravitational collapse by the minute amounts of self-annihilating dark matter inside them,” Ilie said. Supermassive dark stars and their black hole remnants could be key to solving two recent astronomical puzzles: i. the larger than expected extremely bright, yet compact, very distant galaxies observed with JWST, and ii. the origin of the supermassive black holes powering the most distant quasars observed.

Katherine Freese first proposed the idea of dark stars with Doug Spolyar and Paolo Gondolo, publishing their initial peer-reviewed paper on the concept in Physical Review Letters in 2008. That study outlined how dark stars might grow and eventually collapse into supermassive black holes in the early universe. In 2010, Freese, Ilie, Spolyar, and their collaborators expanded on the theory in The Astrophysical Journal, describing two possible processes that could allow dark stars to reach immense sizes and predicting that they could seed the black holes found in the earliest quasars known to exist.

Dark matter is thought to make up roughly a quarter of the universe, yet its nature remains one of science’s greatest mysteries. Researchers believe it is composed of a still-undetected type of elementary particle. Decades of experiments have searched for these particles, but so far without success. One leading possibility involves Weakly Interacting Massive Particles (WIMPs). When two WIMPs collide, they are expected to annihilate each other, releasing energy that could heat collapsing hydrogen clouds and cause them to shine as brilliant dark stars.

Conditions a few hundred million years after the Big Bang, within dense regions called dark matter halos, appear to have been ideal for forming such stars. These regions are also where the first generation of normal stars was expected to appear.

“For the first time we have identified spectroscopic supermassive dark star candidates in JWST, including the earliest objects at redshift 14, only 300 Myr after the Big Bang,” said Freese, the Jeff and Gail Kodosky Endowed Chair in Physics and director of the Weinberg Institute and Texas Center for Cosmology and Astroparticle Physics at UT Austin. “Weighing a million times as much as the Sun, such early dark stars are important not only in teaching us about dark matter but also as precursors to the early supermassive black holes seen in JWST that are otherwise so difficult to explain.”

In a 2023 PNAS study by Ilie, Paulin, and Freese, the first supermassive dark star candidates (JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0) were identified using photometric data from JWST’s NIRCam instrument. Since then, spectra from JWST’s NIRSpec instrument became available for those, and a few other extremely distant objects. The team, which now also includes Shafaat Mahmud analyzed the spectra and morphology of four of the most distant objects ever observed (including two candidates from the 2023 study): JADES-GS-z14-0, JADES-GS-z14-1, JADES-GS-13-0, and JADES-GS-z11-0 and found that each of them is consistent with a supermassive dark star interpretation.

JADES-GS-z14-1 is not resolved, meaning it is consistent with a point source, such as a very distant supermassive star would be. The other three are extremely compact, and can be modeled by supermassive dark stars powering a nebula (i.e. ionized H and He gas surrounding the star). Each of the four objects analyzed in this study is also consistent with a galaxy interpretation, as shown in the literature. Dark stars have a smoking gun signature, an absorption feature at 1640 Angstrom, due to the large amounts of singly ionized helium in their atmospheres. And in fact, one of the four objects analyzed shows signs of this feature.

“One of the most exciting moments during this research was when we found the 1640 Angstrom absorption dip in the spectrum of JADES-GS-z14-0. While the signal to noise ratio of this feature is relatively low (S/N~2), it is for the first time we found a potential smoking gun signature of a dark star. Which, in itself, is remarkable,” Ilie said.

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) measured the spectrum of the same object, revealing the presence of oxygen, via a nebular emission line. Researchers said that if both spectral features are confirmed, the object cannot be an isolated dark star, but rather may be a dark star embedded in a metal rich environment. This could be the outcome of a merger, where a dark matter halo hosting a dark star merges with a galaxy. Alternatively, dark stars and regular stars could have formed in the same host halo, as the researchers now realized it is possible.

The identification of supermassive dark stars would open up the possibility of learning about the dark matter particle based on the observed properties of those objects, and would establish a new field of astronomy: the study of dark matter-powered stars. This published PNAS research is a key step in this direction.

Funding Acknowledgments: This research was made possible by generous funding from the following agencies: Colgate University Research Council, The Picker Interdisciplinary Sciences Institute, the U.S. Department of Energy’s Office of High Energy Physics program, Swedish Research Council, LSST Discovery Alliance, the Brinson Foundation, the WoodNext Foundation, and the Research Corporation for Science Advancement Foundation.

Q: How would you summarize your study for a lay audience?

In short: We found that the defense protein “Resistin like molecule gamma” (Relmy), produced by neutrophils, punches holes into heart cells after a heart attack. This promotes dangerous, fast, and irregular heart rhythm and cell death in the heart.

The longer version: The most lethal complications of coronary artery disease are myocardial infarction (MI) and sudden cardiac death.

In MI, the blockage of a heart artery leads to insufficient oxygen supply to heart muscle cells (cardiomyocytes). This compromises their ability to maintain a stable rhythm and can give rise to a dangerous, unstable heart rhythms (arrhythmia) called ventricular tachycardia (VT) and ventricular fibrillation (VF).

VT and VF are both serious arrhythmias that can lead to sudden cardiac arrest and death within minutes. In VT, the heart beats very rapidly, but in a coordinated rhythm. In VF, the rhythm is chaotic and uncoordinated.

Most arrhythmias occur within 48 hours after MI and coincide with massive immune cell infiltration into the heart tissue. We were interested in how these immune cells may promote arrhythmia.

We found neutrophils that get recruited into the infarct (the area of dead tissue resulting from the cutoff of oxygen supply) in large numbers upregulate the gene “Retnlg,” coding the protein resistin like molecule gamma (RELMy). We also found a comparable gene, “RETN,” in human infarcted heart tissue. When we removed this protein from neutrophils in mice, the arrhythmia burden after MI was reduced 12-fold.

Q: What question were you investigating?

We were investigating the question of how neutrophils, a specific kind of immune cell, promote ventricular arrhythmia (a dangerous fast irregular heartbeat) after heart attacks. Cardiomyocytes as the main actors in arrhythmia are very well studied, but if and how immune cells can promote arrythmia is less clear. This work is important because ventricular arrhythmia is the most lethal complication after myocardial infarction. We need to understand better what promotes arrythmia to help us develop new antiarrhythmic drugs.

Q: What methods or approach did you use?

We used a plethora of methods to figure this out. For an initial understanding about which proteins in neutrophils might be important, we used deposited data on gene expression generated by single cell and spatial RNA-sequencing from mice that underwent myocardial infarction. But we also used data from human studies to find similarities in human tissue.

We also relied on confocal and super-high resolution microscopy in isolated mouse heart muscle cells that were treated with the labeled protein. Further, we deployed in vitro assays such as a liposome model and cell culture techniques to investigate the mouse and the human version of the protein to find out if they work similar.

Q: What did you find?

We found that after MI in mouse models, neutrophils upregulatethe expression of “Retnlg,” the gene coding for RELMy. We also found that the human biological homolog “RETN,” the genecoding for Resistin, was higher expressed in human infarcted myocardial tissue compared to non-infarcted tissue, similar to mice.

We saw that deleting the gene from bone marrow derived cells (such as neutrophils) and deleting the gene from neutrophils specifically significantly reduced incidents of ventricular arrhythmia in the mouse models.

Q: What are the implications?

The implications are that immune cells play a crucial role in sudden death and arrhythmia.

We should think about treating both the myocardial infarction both by quick recanalization of the vessel to restore oxygenated blood supply and also by targeting immune cells to mitigate the arrhythmic effects of the injury.

When we understand the underlying mechanisms better, we can pursue therapeutic targets that go beyond the broad immune suppression that is used today.

If we can treat targets more specifically, we can reduce unwanted side effects and unravel the full potential of immune modulation in cardiovascular disease.

Q: What are the next steps?

The next steps are to find a way to neutralize the harmful protein and test if this can reduce VT burden and infarct size. First in the mouse models, but, we hope, eventually also in humans.

We should gather more evidence about the significance of this protein in human disease. It is also interesting to see these findings have implications for other diseases with neutrophil recruitment and activation.

Authorship: In addition to Nina Kumowski and Matthias Nahrendorf, Mass General Brigham authors include Steffen Pabel, Jana Grune, Noor Momin, Kyle I. Mentkowski, Yoshiko Iwamoto, Yi Zheng, I-Hsiu Lee, Fadi E. Pulous, Hana Seung, Alexandre Paccalet, Charlotte G. Muse, Kenneth K. Y. Ting, Paul Delgado, Andrew J. M. Lewis, Vaishali Kaushal, Antonia Kreso, Dennis Brown, Kamila Naxerova, Michael A. Moskowitz, and Maarten Hulsmans.

Funding: This work was supported by grants from the Leducq Foundation, the National Institutes of Health (NIH grants HL155097, HL149647, HL142494, HL176359, NS136068, DP2AR075321); the Deutsche Forschungsgemeinschaft (DFG) Walter Benjamin Programm (491497342 and 530157297); the British Heart Foundation (FS/ICRF/24/26111 and RE/18/3/342140), and the NIHR Oxford Biomedical Research Centre.

Disclosures: Nahrendorf has received funds or material research support from Alnylam, Biotronik, CSL Behring, GlycoMimetics, GSK, Medtronic, Novartis, and Pfizer, and has received consulting fees from Biogen, Gimv, IFM Therapeutics, Molecular Imaging, Sigilon, Verseau Therapeutics and Bitterroot. Matthias and Wirth are employees of the company Abberior Instruments America, which commercializes the MINFLUX technology. Lewis is on the advisory board of Abbott, AstraZeneca, and Novartis. Pabel is employed by the Novartis Institute of Biomedical Research. Hayat is a cofounder and shareholder of Sequantrix GmbH and has received research funding from Novo Nordisk and AskBio. The remaining authors declare no competing interests.

For more than two decades, finasteride has been prescribed to millions of men seeking to slow or reverse hair loss. Behind its cosmetic appeal, however, evidence has continued to emerge suggesting serious mental health consequences, including depression, anxiety, and in some cases, suicide.

Prof. Mayer Brezis of the Hebrew University of Jerusalem argues that both the medical community and regulators have repeatedly failed to protect the public by overlooking signs of psychiatric harm associated with the drug.

His review analyzed data from eight large studies published between 2017 and 2023. The findings show a clear trend: people who used finasteride were far more likely to experience mood disorders and suicidal thoughts than those who did not. This pattern appeared consistently across various national databases, including the FDA’s adverse event system and healthcare records from Sweden, Canada, and Israel.

“The evidence is no longer anecdotal,” said Prof. Brezis, a professor emeritus of medicine and public health. “We now see consistent patterns across diverse populations. And the consequences may have been tragic.”

The report estimates that hundreds of thousands of users may have suffered from finasteride-related depression, and that hundreds — possibly more — may have died by suicide. Originally approved by the FDA in 1997 for male pattern baldness, the drug has remained popular for its perceived safety and effectiveness, particularly among younger men. Critics say, however, that its risks were downplayed or ignored.

A Delayed Response, With a High Cost

Although the FDA recognized depression as a possible side effect in 2011 and added suicidal thoughts to the label in 2022, researchers had been warning of potential dangers as early as 2002. Internal FDA files from 2010, cited in Brezis’ review, contained entire sections redacted as “confidential,” including estimates of how many people might have been affected.

By 2011, only 18 suicides linked to finasteride had been reported to the FDA. Based on worldwide usage, Brezis concluded the actual number should have been in the thousands. “It wasn’t just underreporting,” Dr. Brezis wrote. “It was a systemic failure of pharmacovigilance.”

Unlike drugs used to treat obesity or psychiatric disorders, which are often closely monitored after approval, finasteride’s classification as a cosmetic treatment may have shielded it from deeper scrutiny. None of the data-mining studies referenced in the review were initiated by Merck, the company that developed the drug, nor were they commissioned by regulatory authorities.

A Cosmetic Drug With Life-Altering Risks

Brezis argues the drug’s classification as a non-essential, appearance-enhancing medication changes the risk calculus. “This wasn’t about life or death medical necessity,” he said. “This was about hair.”

The biological rationale is clear. Finasteride works by blocking the conversion of testosterone into dihydrotestosterone (DHT), but in doing so, it may also disrupt neurosteroids like allopregnanolone — linked to mood regulation in the brain. Animal studies have shown long-term effects on neuroinflammation and even changes in hippocampal structure.

For some patients, the consequences don’t end when the pills do. Reports of lingering symptoms — dubbed “post-finasteride syndrome” — include insomnia, panic attacks, cognitive dysfunction, and suicidal thoughts that persist months or even years after stopping treatment.

Regulatory Gaps, Corporate Silence

The report is especially scathing toward the FDA and Merck. Despite having access to millions of patient records and robust pharmacovigilance tools, neither party acted in time, Brezis argues. The industry’s silence was strategic, he suggests, driven by market pressures and legal liability — echoing past controversies like Merck’s handling of Vioxx.

“Nothing is more important to Organon than the safety of our medicines,” the company recently claimed in a public statement. Yet none of the safety studies cited were initiated by the manufacturer.

The FDA, meanwhile, took five years to respond to a citizen petition calling for a black-box warning. Its final decision? To add suicidal ideation to the label — but not as a formal warning.

What Now?

Brezis is calling for immediate changes in how drugs like finasteride are approved, monitored, and prescribed. His recommendations include suspending marketing of the drug for cosmetic purposes until safety is re-established, mandatory post-approval studies with strict enforcement, and systematic recording of drug histories in suicide investigations.

“For many, those changes come too late. The paper is dedicated to one such individual — a previously healthy man who took finasteride “just” to improve his hair. Within days, he spiraled into severe psychiatric distress. He never recovered. Months later, he took his own life.”