07/03/2026
Sad još s Verom Rubin u Čileu, gledamo nebo kao nikad prije, a Rubin i zapaža tisuće promjena svakodnevno i bilježi i vremenom će pregledati i zabilježiti cijelo nebo.
Webb g***a sve u drugoj frekvi, infracrvenoj i zato:
James Webb Space Telescope vidi puno dalje zato što promatra infracrveno zračenje (infrared), a ne vidljivu svjetlost kao klasični teleskopi.
Frekvencije / valne duljine
Webb radi otprilike u području:
0.6 – 28 mikrometara (µm) valne duljine
to odgovara frekvencijama približno 10¹³ – 5×10¹⁴ Hz
To pokriva:
bliski infracrveni dio (near-infrared)
srednji infracrveni dio (mid-infrared)
Zašto tako vidi dalje
Tri glavna razloga:
Crveni pomak (redshift)
Svjetlost iz vrlo udaljenih galaksija rastezanjem svemira prelazi iz vidljivog u infracrveno područje.
Probijanje kroz kozmičku prašinu
Infracrvene valne duljine lakše prolaze kroz oblake plina i prašine, gdje nastaju zvijezde.
Hladni objekti zrače infracrveno
Planeti, protozvijezde i mnoge strukture svemira emitiraju najviše upravo u infracrvenom spektru.
Kako dobivamo “normalne slike”
Detektori na Webbu mjere intenzitet infracrvene svjetlosti u različitim filtrima.
Znanstvenici zatim:
svakoj infracrvenoj valnoj duljini dodijele vidljivu boju
kombiniraju ih u false-color sliku
Zato JWST fotografije izgledaju spektakularno — to su prevedene infracrvene informacije u vidljivi spektar.
Zašto tako daleko i kako točno:
How the James Webb Space Telescope can see almost to the beginning of the Universe
One of the reasons the James Webb Space Telescope is such a revolutionary instrument is that it observes the Universe primarily in infrared light, not visible light.
When the first galaxies formed, their light was mostly emitted in ultraviolet and visible wavelengths. But during the 13+ billion years it takes that light to reach us, the expansion of the Universe stretches those wavelengths — a phenomenon known as redshift.
So the light that originally left those galaxies as ultraviolet or visible light arrives today shifted into the infrared. That’s exactly the range Webb is designed to observe.
There is also the simple but mind-bending fact that looking far away means looking back in time. If a galaxy is 13 billion light-years away, the light we see today actually left that galaxy 13 billion years ago. In other words, Webb is literally showing us what the Universe looked like when it was only a few hundred million years old.
Some of the galaxies Webb has already detected have redshifts around z ≈ 13–15, which means we are seeing them when the Universe was only 300–400 million years old — roughly 2–3% of its current age.
But to detect that extremely faint infrared light, Webb itself must be incredibly cold. If the telescope were warm, its own heat would glow in infrared and completely blind its detectors.
That’s why Webb carries its enormous five-layer sunshield, about the size of a tennis court. It permanently blocks light and heat from the Sun, Earth and Moon, cooling the telescope passively down to about 40 Kelvin (−233°C).
One of its instruments, MIRI (Mid-Infrared Instrument), has to go even colder — about 7 Kelvin (−266°C) — and uses a special cryocooler system to reach those temperatures.
Combined with Webb’s 6.5-meter segmented mirror and extremely sensitive infrared detectors (NIRCam, NIRSpec and MIRI), the telescope can capture unimaginably faint signals that have travelled across the Universe for more than 13 billion years.
Webb also uses another cosmic trick: gravitational lensing. Massive galaxy clusters bend space-time and act like natural magnifying glasses, allowing Webb to detect galaxies that would otherwise be far too faint.
The result is something that still feels almost unreal: images filled with galaxies whose light began its journey near the dawn of the Universe itself.
