On March 11, NASA deployed Polarimeter to Unify the Corona and Heliosphere, or PUNCH for short. Three months later, the mission has finally produced its first scientific data—and it's breathtaking.
For context, PUNCH is a set of four satellites perched in a sun-synchronous polar orbit about 650 kilometers above the surface. Together, they are capable of capturing highly detailed images of a wide variety of phenomena associated with solar weather. Their instruments are particularly adept at recording coronal activity and solar wind dynamics—a very difficult phenomenon to observe.
But the main innovation of these four probes is that they have an extremely wide field of vision. It covers a large portion of the sky, well beyond the observation capabilities of all current coronagraphs like LASCO. The latter is one of the most powerful instruments in the world when it comes to capturing this type of phenomenon; but it is also very old, and its optics only cover a much narrower region in comparison.
A first series of breathtaking images
In practice, this means that PUNCH can track the propagation of many solar-related phenomena over a very long distance, with excellent resolution. And to see this, just look at the public footage of the mission, which was presented at the 246th meeting of the American Astronomical Society and spotted by ScienceAlert.
"I'd like to draw your attention to the white circle near the center of the field of view. This circle represents the field of view of LASCO, the largest coronagraph currently used to forecast space weather," explained astrophysicist and co-author Craig DeForest during his talk. A very telling detail that allows us to realize the enormous difference that exists between the performances of the two devices.
A new look at CMEs
DeForest's team used this enormous field of view to reveal a whole new perspective on a very important phenomenon in solar dynamics: Coronal Mass Ejections, or CMEs. These are events that occur when our star's magnetic field lines intertwine, break, and reconnect. This process releases an immense amount of energy that literally tears material from the star's corona, ejecting a very large number of charged particles. These particles cluster together in the form of a huge plasma bubble that can weigh up to several billion tons. Depending on their point of origin, these CMEs can sometimes head straight for Earth. If so, they appear to us as a halo, a sort of aureole that seems to grow around the Sun as the material approaches our planet at several hundred kilometers per second. And this is precisely what PUNCH managed to capture.
“This coronal ejection halo is something you’ve never seen before,” DeForest explains. “If you follow the scientific press, you’ve probably seen movies of coronal ejection halos. But you’ve never seen one 30 or 40 degrees from the Sun… here you’re seeing something literally sweeping across the entire sky of the inner solar system as it approaches Earth,” the researcher insists.
And the best part is, this is just the beginning. The four probes haven’t reached their final positions yet, and the instrument calibration process isn’t quite complete. This means that within a few months, PUNCH will be able to produce even more precise images. These will be incredibly valuable for researchers studying the Sun's dynamics and its influence on other celestial bodies, starting with Earth.
Monitoring the Sun: More Than Just Science
We know that CMEs can have a very tangible impact on our planet. When these gigantic plasma bubbles head towards Earth, they end up colliding with its magnetic field, which acts as a shield against these charged particles. This impact transfers some of the CME's energy to the magnetosphere, causing what is called a geomagnetic storm.
The weakest ones have no discernible effect, except for a few beautiful auroras. But beyond a certain threshold, these phenomena can also have much more annoying consequences, such as disruptions to navigation and communication systems. In the most extreme cases, these storms can generate a significant electric current in conductive materials.
And that's a big, big problem. In practice, this means that solar flares, and especially the most violent CMEs, are very dangerous for certain key elements of our technological ecosystem, starting with satellites that operate in an area more exposed to particles from space. In other words, exceptionally violent CMEs represent a major threat to our civilization, as evidenced by the famous example of the Carrington event.
An X-class solar flare caused a radio blackout on Earth
Beyond pure solar science, we also have a very concrete and practical reason to monitor the whims of the Sun. Thanks to PUNCH, we now have a new and very effective tool to do this, and we are already looking forward to discovering the superb images that it will undoubtedly bring back during its two-year mission.
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