Herschel Space Observatory

The Herschel Space Observatory was launched on May 14th 2009 by the European Space Agency. It reached its orbit around the second Lagrangian point (L2), 1.5 million km from the Earth within 2 months where it is now in a Lissajous orbit (stable orbit around a Lagrangian point). Its purpose is to observe the "cool universe" by collecting infrared radiation from from the coldest objects and dust-obscured objects. From this information answers as to how the first 'primordial' galaxies formed and the process of galactic evolution, esp. that of our own, will hopefully be gained. Tracing how molecules conducive to life form, such as water, is another of its objectives.

It houses the largest cassegrain telescope ever launched which incorporates the largest space-based mirror to date, 3.5m in diameter. As is hinted at in this article posted by UCR Phys111 Blog the mirrors utilised by astronomers must be extremely accurate. In this case the mirror, created from silicon carbide, can deviate from perfect smoothness by less than one micron.

Looking deeper...

There are three main instruments incorporated into Herschel:

1) The Photo detecting Array Camera and Spectrometer (PACS)

2) Spectral and Photometric Imaging Receiver (SPIRE)

3) Heterodyne Instrument for the Far Infrared (HIFI)

Herschel's instruments have been designed to study the electromagnetic spectrum in the range of 55 to 670um. They are focussed on investigating the evolution of galaxies, and star formation and interactions with the interstellar medium. Also, investigations of the chemical composition of celestial bodies in our solar system are being carried out. The last of the four focuses of Herschel's investigations is studying the formation of molecules including water throughout the universe.

These instruments must be maintained at an extremely low temperature of 2K. That's even colder than the vacuum in space! This can only be achieved using liquid helium which boils away, limiting the lifespan of Herschel to approximately 3 years.

Why was Herschel launched?

The Herschel Observatory, located in space, suffers from no atmospheric distortions and thus there is no need to account for "seeing" effects in any data or images taken. Being outside the atmosphere, Herschel can also observe the universe in the infrared wavelengths which are almost entirely blocked out on the surface due to absorption by the water molecules. (These water molecules also emit infrared radiation creating further interference.)

The discoveries

The wide scope of wavelengths at which it can collect data allows it to bridge the observation gap between previous space-based telescopes and ground-based radio telescopes. Since it began collecting data, it has discovered a previously unknown stage of stellar formation as well as evidence of the presence of molecular oxygen in space. Additionally, measurements of deuterium content in comets suggests that the majority of Earth's water could have come from comet impacts.