Why neutrino astronomy won the 2026 Nobel Prize in Physics, and what skywatchers can see this October and November

Dr Smethurst says that from October 23 to 24, 2026, the Moon will swing past the planet Saturn, which can serve as a signpost for finding Saturn's yellowish point in the night sky.

By October 27 and into the morning of October 28, the just-past-full Moon will pass the Pleiades star cluster. She describes the Pleiades to the naked eye as a fuzzy miniature Big Dipper, and says binoculars or a telescope reveal the gas in the cluster and more individual stars. She suggests returning a few nights later, when the full Moon's glare is less dominant and the detail is easier to see from darker skies.

On November 2 and 3, the half Moon will pass Mars and Jupiter in the early morning sky. Dr Smethurst says Jupiter is the brighter of the two and Mars will look reddish to the eye. Because this is just before sunrise, viewers need to be up early, and the clock change in Europe means the viewing hour arrives an hour later than it otherwise would.

Venus rises high enough in early November to be seen in the morning sky. She calls it the brightest object in the night sky after the Moon. On the morning of November 7, a very thin crescent Moon will indicate Venus near the sunrise glow in the east, and the bright star Spica will also be nearby. As Venus climbs higher through November, with Mercury rising behind it lower in the sky, the so-called planet parade takes shape.

Dr Smethurst warns that viewers will see a lot of hype about the so-called planet parade, which some call a planetary alignment. She says it is genuinely cool that Jupiter, Mars and Venus, and possibly Mercury if the horizon is flat, can be seen together in the November mornings before sunrise.

She explains that the planets always appear roughly along one line in the sky whenever they are observed, because the solar system's objects orbit in roughly the same flat plane. In November, however, Jupiter and Mars will cluster close together high in the sky, bright Venus will sit nearer the horizon, and the fainter Mercury will be hard to spot below it. Most people will therefore see three planets, not a neat line.

Dr Smethurst says many people will cite November 18, when Mercury reaches its highest point above the horizon. But that height is still low, and trees and buildings will block many observers, so most people will not see it then. She suggests that any clear morning from early November is a good time to look.

Jupiter and reddish Mars move slowly closer together from Earth's perspective as they travel along their orbits, reaching their closest pass on November 15 before moving apart again. She says watching them draw closer over the preceding weeks makes the closest pass more rewarding.

On October 7, the European Space Agency and the International Astronomical Union signed an agreement to commit to developing technical solutions that keep the sky dark and quiet. Dr Smethurst notes that satellites are now often the first thing people see when they look up in the hours after sunset, and that the situation is noticeably worse than five years ago.

She explains that satellites reflect sunlight back to Earth, so growing numbers add light pollution that brightens the night sky. Satellites also streak across telescope images, and because they carry electronics that emit radio waves, they add interference to radio telescopes that study growing black holes or search for signs of technological life. She cites the 2026 Space Environment report, which shows a steep rise in launches: in 2025 alone, more than 300 launches put over 4,000 new satellites into orbit.

Under the agreement, ESA will develop materials that are less reflective, electronics that generate less radio noise, and models that let engineers predict how a satellite design will appear to ground telescopes so they can adapt it. Dr Smethurst says ESA is the first space agency to agree to this with the IAU's Center for the Protection of the Dark and Quiet Sky, and she hopes NASA will follow, especially since US space companies are among the largest contributors to the growing number of satellites.

Dr Smethurst describes the Extremely Large Telescope under construction in Chile, due to see first light in 2030. Its 39-metre mirror and six giant lasers, which correct for the blurring effect of Earth's atmosphere, are expected to give images 15 times sharper than Hubble and six times sharper than the James Webb Space Telescope, provided bright satellite streaks do not ruin the observations. She says this is a concern both for the public right to a dark sky and for professional astronomers.

Roman launched on August 30, 2026 and is travelling 150 million kilometres from Earth to its orbit around the Sun, where it will conduct science observations. Dr Smethurst describes Roman as NASA's next flagship observatory and the successor to Hubble, with a much wider field of view.

The telescope was launched out of focus, because the launch would shake it and there was no point sending it up in focus. Over the past month, NASA slowly brought it back into focus, using focus estimates from ground testing. The team found that conditions in space, such as temperature, gravity and humidity, differ from the lab, so it needed adjustment. It announced this month that it had moved one of the mirrors by about one-sixteenth of the diameter of a human hair, and that the telescope's performance is 30 percent better than before.

Dr Smethurst says she hopes Roman will release public images soon, and says she hopes this will happen before Christmas.

The 2026 Nobel Prize in Physics was awarded to Francis Halzen for decisive contributions to the IceCube Neutrino Observatory and the discovery of high-energy neutrinos of astrophysical origin. Dr Smethurst says he was honored for his role in the 2013 discovery of two extremely high-energy PeV neutrinos.

Neutrinos are tiny subatomic particles that barely interact with matter. Dr Smethurst says about 100 trillion pass through the body every second without being noticed, and most come from the Sun. The IceCube neutrinos were so energetic that they must have come from beyond the solar system. Since 2013, more high-energy neutrinos have been detected, but their astrophysical source is still unexplained.

Dr Smethurst says she finds it hard to accept that a Nobel Prize can be shared by at most three people when modern science relies on large collaborations, and she notes this year's prize went to a single person for the first time since 1992.

Dr Smethurst says she was initially surprised, given her astrophysics background, that the prize went to a detection with no astrophysical explanation yet. She notes the Nobel committee has often waited for confirmation, as with Peter Higgs, whose boson was recognised only after CERN detected it. Colleagues in particle and high-energy astrophysics, however, told her the award makes complete sense.

Dr Smethurst explains that the IceCube detection connects to the study of the highest-energy objects in the universe, such as supernovae, mergers of two neutron stars, and growing supermassive black holes with material spiralling in at great speed. The problem is that gamma rays from these sources interact with matter as they travel and convert their energy into electron and positron pairs, starting at around 10 TeV.

Dr Smethurst explains that a TeV is a trillion electron volts. The Large Hadron Collider at CERN reaches about 7 TeV, so energies around 10 TeV are beyond what current ground-based particle accelerators can produce. Gamma rays in that range are also not detected from space, because they are lost in interactions that produce electron and positron pairs instead.

Dr Smethurst says studying super-high-energy processes is still possible, because the same sources also produce cosmic rays, mainly protons accelerated to huge speeds. Cosmic rays were first detected in 1912 and studied in cloud chambers in 1927. When they strike the top of the atmosphere they produce showers of particles that ground detectors can measure, allowing their arrival direction and energy to be estimated.

The problem is that protons carry a positive charge, so magnetic fields deflect them as they travel. The direction at which they arrive may not match their origin, so they cannot be traced back to a specific object. She says the hope lies in neutrinos, which are also predicted to be produced alongside cosmic rays.

Dr Smethurst explains that neutrinos hardly interact with matter, having a very small cross-section, so the chance of colliding with anything is tiny. They are neutral, so magnetic and electric fields do not deflect them, and they do not interact via electromagnetism or the strong force. Dark matter was once proposed as a candidate for them, but simulations ruled that out.

Because neutrinos are unaffected along their path, a high-energy neutrino produced in the universe keeps its energy and direction. If one is detected on Earth, its energy and direction can be traced back to a specific object. Detection is hard, however: it requires a rare direct collision with ordinary matter that produces a flash of light.

Dr Smethurst says the odds are just below one high-energy neutrino per year for a detector one square kilometre in size, so a massive and very sensitive detector is needed. But such sensitivity also picks up high-energy cosmic rays hitting from above, so the detector must be shielded by burial deep underground or under the ocean. Instead, detectors look for neutrinos that have come from below, having passed through the Earth.

IceCube was built over one square kilometre and buried 2.5 kilometres under the Antarctic ice at the South Pole. Holes were drilled, boiling water poured in, and detectors lowered before the ice refroze. Earlier projects had struggled: DUMAND off Hawaii faced water pressure and salt corrosion, and AMANDA showed a detector was possible under Antarctic ice but its array was too small.

The IceCube detector built in 2013 made the important detection of two neutrinos with PeV energies, meaning over 1,000 TeV. Dr Smethurst says the jury is still out on what produces these very energetic neutrinos, though most people suspect blazars, which are growing supermassive black holes with jets pointing at Earth.

She notes that the existence of such high-energy neutrinos had been predicted for decades by cosmic ray science, which fits the typical theoretical prediction and award pattern. She then asks why Halzen alone received the prize among many IceCube collaborators. Halzen is a theoretical physicist who by his own admission has not been to the South Pole. Dr Smethurst says everyone she spoke to said IceCube would not exist without him: he made early predictions of neutrino production, calculated the detector size needed, proposed how the detector would register the flash of light, and led the campaign to raise money through proposals and government support.

According to the Nobel committee, Halzen's vision and scientific leadership made neutrino astronomy possible. When he learned he had won, he was travelling around Europe to drum up support for the next generation of neutrino detectors. Quoting him, Dr Smethurst says he was sitting in his hotel room writing a proposal, joking in one of the meetings that he hoped it would help get it funded.

Dr Smethurst says that setting aside the issues with the Nobel Prize, every colleague she spoke to in the field said no one is more deserving of the physics Nobel than Halzen.

Dr Smethurst recalls that the first fast radio burst was spotted in 2007. She says these are very short millisecond flashes that give off more energy in that burst than the Sun does in a full day. Her earlier video from 2018 counted 30 known bursts, and thousands are now known. The leading explanations are kilonovae from merging neutron stars, or magnetars, neutron stars with very strong magnetic fields.

In March 2024, the MeerKAT team using the MeerKAT telescope in South Africa detected a fast radio burst dubbed 2024304b. Its data suggested it was extremely distant, possibly the most distant one ever spotted, because the burst's position could be triangulated very precisely, yet the world's largest ground-based telescopes detected no galaxy or even star in that patch of sky.

Caleb and collaborators applied to use the James Webb Space Telescope to look for the galaxy, and found one at that position. They worked out that it lies 10.6 billion light-years away, so it is seen as it was when the universe was about 3 billion years old, near the peak of star formation. Most fast radio bursts found so far come from much closer galaxies.

Dr Smethurst argues that the burst is unlikely to come from a kilonova, because neutron star mergers take billions of years to occur and tend to happen in older galaxies, while this host is young, small and forming many new stars. A magnetar from a supernova is therefore the likeliest explanation, though she says this is uncertain, since the merger timing estimates could be wrong. She says more bursts found with MeerKAT would let astronomers census the host galaxies and clarify what produces them.