The many eyes of ALMA
How does a radio-telescope really ‘see’? To find out, we’re taking a peek inside one of the Atacama Large Millimeter/submillimeter Array (ALMA) antennas for this Picture of the Week. ALMA, in which ESO is a partner, is based high up in the Chajnantor plateau in the Chilean Andes, and is comprised of 66 antennas — all used to observe the cool corners of the Universe.
First, light is collected by the large dish of an antenna, which is focussed onto the secondary reflector that we can see in the foreground. From there, it goes through one of the several circular windows seen at the centre of this image. Each window leads to a receiver –– a device that registers the light collected by the antenna. The ALMA antennas are equipped with 10 receivers each capturing light at different wavelengths, depending on what astronomers want to observe.
The light being captured has wavelengths of around a millimetre, which is longer than the wavelength of visible light. So, while the windows of the receivers look opaque to our eyes, they are transparent to the radiation that ALMA observes. But why are these windows needed at all?
The receivers need to be sealed inside a cryostat that cools them down to –269 ºC, just 4 degrees above absolute zero. This minimises the amount of heat they give off, which would otherwise hamper ALMA’s ability to detect the very faint radiation coming from cold cosmic objects, like clouds of gas and dust where new stars are formed.
S. Otarola/ESO
Kuvasta
| Tunnistus: | potw2517a |
| Tyyppi: | Valokuvallinen |
| Julkaisupäivä: | 28. huhtikuuta 2025 6:00 |
| Koko: | 4020 x 6036 px |
Kohteesta
| Nimi: | ALMA AOS |
| Tyyppi: | Unspecified : Technology : Observatory : Telescope |
| Kategoria: | ALMA |
Kuvaformaatit
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