Space explained
M64 and the Infrared: dust Revealing Stars like Autumn Leaves
The cold air that heralds autumn stages colors and lights on very different scales.
In brief
Arctic plant color change and re-emitted light from dust in M64 are two examples of how multi-band observations reveal hidden processes: chlorophyll loss unveils terrestrial pigments, dust in the galaxy reveals newborn stars.
Key points
- Tundra leaves begin to change in early September and peak in mid-month.
- The color period in the northernmost regions can last a week or less.
- The Webb MIRI instrument sees M64’s dust as red emission in the mid-infrared.
- In M64 the inner and outer gas rotate in opposite directions, likely indicating a past merger.
- Repeated observations across bands reveal hidden processes both on Earth and in space.
The cold air that heralds autumn stages colors and lights on very different scales. Those colors and lights appear on the Nunavut tundras and in the dusty arms of the galaxy M64. Two observations share the same perspective: satellite images that capture the rapid change of leaves, and space images that reveal how dust hides and feeds newborn stars. The central subject is M64. The comparison with terrestrial signals helps to understand transformation mechanisms and the value of repeated observations over time.
When color fades and other pigments emerge
In the Coppermine River valley, images taken on 6 September and 27 July 2026 show the transition from green vegetation to red and yellow tones. Typical species are willows, birches, blueberries and other low tundra plants that begin the seasonal change already in early September. The color change in this region begins in early September and reaches its peak in mid-month. Scientists describe this time window as among the earliest on the North American continent. Satellite observations and a seven-year analysis indicate that the northernmost areas often have a very brief period of intense color. That period sometimes lasts a week or less.
The chemical reason is simple and visible. With falling temperatures and shorter daylight hours, plants reduce production of chlorophyll, which gives green. Without chlorophyll, carotenoids that appear yellow and anthocyanins that reflect red light emerge. The decline of chlorophyll leaves room for previously masked pigments. The citizen scientists involved in the GLOBE phenology campaign can observe and record these changes. These data build long-term databases useful for comparing how plants respond to climatic or seasonal variations.
Repeated images over time make it possible to capture the duration and intensity of the phenomenon.
Dust that glows: how Webb reads the galaxy M64
The galaxy M64 is also called the Black Eye Galaxy for the dark band of dust in front of the nucleus. This galaxy shows that where one telescope sees darkness, another sees emission. The James Webb Space Telescope uses the MIRI instrument, the Mid-InfraRed Instrument, to intercept dust that absorbs light. The dust re-emits the light as infrared radiation and in MIRI images it appears red. The dust in M64 absorbs and re-emits light, making otherwise hidden regions visible. This re-emitted light reveals regions where young stars form that in optical bands appear as pink patches in Hubble images.
MIRI also helps read the galaxy’s dynamics. In M64 the inner and outer gas rotate in opposite directions and where these “currents” meet, compression generates new star formation. Astronomers believe this opposing motion is likely the sign of a merger with a smaller galaxy. The history of M64 includes a collision that altered its evolution. Mid-infrared observations provide information on structure, motion and dust composition, key elements for reconstructing the dynamic past.
Where light seemed to be missing, the dust tells a story of birth.
Comparing scales and methods for reading transformations
The Coppermine images and those of M64 share an observational principle: repeating measurements in different bands changes the story you can read. Satellites like Landsat 9 show seasonal changes in a tundra over a few days. In that tundra the color period can last less than a week. Similarly, Webb reveals structures hidden by dust that are dark in optical but glow in the infrared. Observing at multiple wavelengths is the key to understanding rapid and hidden transformations. The comparison also highlights limits and opportunities. From the few-day window on the tundra come signals sensitive to climate. From infrared dust maps come traces of galactic mergers.
Both cases derive value from repeated campaigns and widespread participation: terrestrial phenology benefits from civic and satellite observations over years. Modern astronomy combines Hubble and Webb to decipher different layers of emission. These practices allow inferences about processes occurring on very different timescales. They share the same principle: the loss or masking of one signal reveals another. An open question remains about how the timings of both phenomena will change with progressing climate change and with new, more sensitive observations.
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