XMM-Newton is an X-ray observatory whose goal is to observe X-ray emissions in the universe to allow us to better understand how and why they are produced. Typical sources of X-rays are the accretion of matter onto black holes, binary systems that contain a neutron star and a black hole, supernova remnants and our own Sun.
RHEA software engineers work at the XMM-Newton Science Operations Centre making the mission’s data available to the global astronomy community. Since its launch more than 20 years ago, numerous scientific discoveries have been made using XMM-Newton data.
XMM-Newton mission timescale
Mission launch: 10 December 1999
Original mission length: 10 years
Current nominal mission end: 31 December 2025, but could continue beyond 2030
About the XMM-Newton mission
X-rays sit between ultraviolet and gamma radiation in the electromagnetic spectrum and are produced by highly energetic sources with temperatures above 1 million Kelvin. Fortunately for us, X-rays are not able to penetrate the atmosphere. However, that also means if we want to perform X-ray observations of the universe, we have to place our X-ray telescope outside Earth’s atmosphere.
The mission was initially named X-ray Multi-Mirror (XMM) from the nested multi-mirror design of its telescope, but was later renamed XMM-Newton in honour of Sir Isaac Newton, who is regarded as the founder of spectroscopy. (Its more formal name is the High-Throughput X-ray Spectroscopy Mission.) It was launched in 1999, nominally as a 10‑year mission, but was designed to perform well beyond this. Still operational more than 20 years later, XMM-Newton is the longest-lived ESA science mission.
As an observatory, XMM-Newton is ‘open’ to the X-ray astronomy community, who can apply for time slots to use XMM-Newton for observations of specific objects. Proposals are evaluated by a group of experts, who allocate observation time to those they select.
About XMM-Newton’s orbit
XMM-Newton’s orbit has always had a period of 48 hours but other orbital parameters have changed since launch:
- Initial perigee (nearest point to Earth): 7,000km
- Initial apogee (furthest point from Earth): 114,000km
- Subsequent perigee range: 6,000km to 22,000km
- Subsequent apogee range: 99,000km to 115,000km.
XMM-Newton’s scientific payload
XMM-Newton carries three types of scientific instruments:
- European Photon Imaging Camera (EPIC) – One EPIC is positioned at the prime focal point of each of the three telescopes. These are very sensitive to weak X-rays and capable of detecting extremely rapid variations in intensity down to less than one-thousandth of a second.
- Reflection Grating Spectrometer (RGS) – Two telescopes have a grating array that disperses 40% of the incoming X-rays to the RGS detector (and camera) at a secondary focus. These are used to determine which chemical element is responsible for the observed X-rays.
- Optical Monitor (OM) – A 30cm very sensitive optical/ultraviolet (UV) telescope. This monitors the same area of the sky as the X-ray telescope and provides complementary information on the sources of the observed X-rays.
After 20 years of operation, more than 6,000 scientific publications have used XMM-Newton data and there have been many notable scientific results. Here are just two examples of the discoveries made possible by XMM-Newton.
Discovery of the sources of gamma ray bursts (2002)
Back in 2001, the origin of gamma ray bursts (GRBs) was surrounded in mystery. It took the XMM-Newton observation of the afterglow of one particular event (GRB 01121) to conclude that in some cases the cause of the GRB was a supernova. Today we know GRBs come in two varieties: long (duration longer than 2 seconds) created by the death of massive stars (supernovae) and short, generated by the merger of two neutron stars.
XMM finds missing intergalactic material (2018)
According to the standard model of cosmology, only 5% of the matter in the universe is of the type we are familiar with (‘baryonic’ matter) while everything else is either Dark Matter or Dark Energy. But until relatively recently, half of the baryonic matter was ‘missing’. Thanks to XMM-Newton we are now closer to solving this puzzle. Observations of a distant quasar have shown that between us and the quasar there are huge reservoirs of material in the right amounts to account for the missing baryonic matter, confirming scientists’ suspicions.
XMM-Newton’s main technical challenges
X-rays are electromagnetic radiation, just like visible light. However, because of the high energy of X-ray photons, they cannot be manipulated the same way as visible light.
Lenses and mirrors used to manipulate visible radiation tend to work best when the incidence angle of the incoming radiation is high (close to 90˚). But at such high incidence angles, most materials either completely absorb or transmit X-rays, so we cannot get any reflections. In addition, the optical components would be damaged quickly because of the high energy of the absorbed photons.
The solution is to use very low incidence angles instead (less than 2˚). Telescopes using this principle are known as grazing incidence Wolter type I telescopes.
The three XMM-Newton telescopes each consist of 58 gold-coated, nested paraboloid mirrors. The large number of mirrors increases the effective area of the telescope. Each telescope weighs 500kg.
How RHEA is contributing to the XMM-Newton mission
The data gathered from XMM-Newton only has value when it is processed and analyzed. Over the years of the mission, RHEA has had two software engineers working at the XMM-Newton Science Operations Centre through which the data is made available to the global astronomy community.
Their contribution has had two main goals:
- Development and maintenance of software tools used to manage the observation proposals submitted by astronomers around the world and the scheduling tool to handle the proposals selected by the Time Allocation Committee.
- Participation in the definition of the data products made available to the X-ray astronomy community through the XMM-Newton Science Archive and development and maintenance of the data processing systems that generate those products from raw data.
Find out more
Read more about XMM-Newton:
- ESA XMM-Newton factsheet
- Discover the work of the XMM-Newton Science Operations Centre
- Ten discoveries – Examples of the range of discoveries about space using data from XMM-Newton
Main image: XMM-Newton in orbit around Earth © ESA/D. Ducros