Affelia is based at DIAS (Dublin Institute of Advanced Studies) Dunsink Observatory in Dublin, but is known to OAS members when she worked at the Royal Observatory in Greenwich. She uses measurements taken by space telescopes such as ESA-XMM-Newton (170 wafer-thin cylindrical mirrors spread over three detectors) and Juno (JADE and JEDI detectors) to study the X-ray emissions of outer planets in our Solar System.
The typical targets for X-ray astronomy are Active Galaxy Nuclei, distant pulsars and deep field exposures into beginnings of the universe, but Affelia is using X-rays to study our own solar system.[It is worth noting the deep field exposures over 81days has shown over 5000 significant black holes and are now giving clues as to how they grew.]
The main source of X-rays in the Solar system are from the Sun via the solar wind, with planets reflecting ‘X-ray photons’ as florescence or from X-rays being captured in the magnetospheres and accelerated into the ‘polar regions’ so as to produce ’X-ray photons’ as dramatic aurorae in their atmospheres.
Mercury does produce ‘X-ray photons’ as its magnetic field bends the electro-magnetic radiation from the Sun onto its surface. Pluto has produced some 5 or 6 ‘X-ray photons’ on telescope detectors. So far we have not seen anything from Neptune, but
that maybe due to instrument sensitivity. There are ‘charge exchange’ events involving comets, as X-rays knock out electrons around Chromium atoms and produce X-ray photons. Jupiter is Affelia’s main research target, with pixelated images from ISA-XMM, but she references information from Einstein observatory HEAO-2 (1978), ROSAT
(1990), Chandra (1999) and NuSTAR SMEX-11 (2012). Basically, she looks at the Jupiter
Aurorae and the fluorescence from Jovian moons.
The Jupiter magnetosphere is 20,000 times stronger than the Earth and if it could be viewed in the sky, it would appear 6x the size of the full moon and stretching back to Saturn, so billions of kms!!
The Jovian moon ‘Io’ is very close to Jupiter and expels 1000 kgs of matter per second, which eventually becomes plasma and is caught in the Jovian magnetosphere. There are weak aurorae (JADE detector) where one electron is removed from an atom by the X-ray to produce ionisation, but there are strong aurorae (JEDI detector) where maybe seven electrons have been removed from an oxygen atom, leaving only one electron. Affelia has to take into account that aurorae can be disrupted by Io’s orbit and volcanic activity, plus Jupiter’s very fast spin rate, at 10 hours, which can ‘snap’ the magnetic lines.
There are spectral lines (from specific elements) from the X-ray Photon detectors on ISA-XMM and then a fuller general graph using some interpolation. Affelia has shown that the activity of the Sun is the bigger influence of output, but also Io (termed Iogenic influence) and other processes including the tilt of the planet and atmospheric issues. Affelia looks at infrared, UV images to confirm her findings. She is partly trying to analyse via fluorescence the chemical composition of Jupiter and more specifically its moons, as well as understanding magnetospheres from the aurorae.
Affelia talked about Saturn. The rings do show florescence, especially as they are made of water ice and so they found Oxygen VII (using JEDI), which are oxygen atoms that have lost seven of its eight electrons. She also mentioned using the X-rays from the Crab Nebula (rather than the Sun) to look at Triton (around Saturn) using the Chandra telescope. It was determined that Triton’s shadow on the detector was larger than expected and so the Triton atmosphere has to be thicker!
Uranus was detected in 2021 using old data from 2002 via the ACIS observation (onboard Chandra). They counted X-ray photons from the planet and found there were five using a grid pattern overlaid on the results!! The Chandra detector could be used to determine where these X-ray photons came from and more importantly that Uranus appears brighter than it should be and this process will require further research and understanding. Recently, the ISA-XMM telescope looked at Uranus for 35 hours and effectively 100 hours of data across its three detectors, which did see a handful of X-ray photons but this data is yet to be analysed.
The Earth does give off X-ray related Aurorae and it was discovered by the ESA integral mission (2002), which was spotted it by accident in 2015, when the Earth came into the field of view. Affelia is worried about the Chandra budget cuts announced by NASA early April this year. She would like to see more X-ray detectors on new telescopes (obviously) and is collaborating with other astrophysicists working in the different electromagnetic spectrums; aside from working with the other three worldwide scientists specialising
is X-raying the solar system.
Article courtesy of Simon Smollett