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Prospects for X-ray astronomy from the lunar surface

Prospects for X-ray astronomy from the lunar surface. Steven Sembay. Co-I of the EPIC-MOS X-ray camera on XMM-Newton. Jenny Carter , Michael Collier, George Fraser and Steve Snowden Department of Physics and Astronomy, University of Leicester, Leicester, UK.

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Prospects for X-ray astronomy from the lunar surface

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  1. Prospects for X-ray astronomy from the lunar surface Steven Sembay Co-I of the EPIC-MOS X-ray camera on XMM-Newton Jenny Carter, Michael Collier, George Fraser and Steve Snowden Department of Physics and Astronomy, University of Leicester, Leicester, UK. Laboratory for Geospace Physics, NASA/GSFC, Greenbelt, USA. X-ray Astrophysics Laboratory, NASA/GSFC, Greenbelt, USA.

  2. XMM: 1999-? ~0.5 m2 XEUS: 2020+? ~5 m2 Why would you place an X-ray telescope on the lunar surface? What would be its scientific goals? What design would you employ?

  3. Speculative 21st Century High Throughput (>100 m2) Lunar X-ray Observatory c.f. Gorenstein, P. 1990, High throughput X-ray telescope on a lunar base, in “Astrophysics from the Moon; Proceedings of the Workshop”, AIP, 207, 382 Science Goals include: Large scale structure of the universe to z>=2 through survey of cluster Fe emission Evolution of accretion disk in AGN to z>=2 through study of Fe fluoresence line

  4. Lunar X-ray Observatory (LXO) on a more practical scale…. X-ray telescopes which are small instrument packages that can be delivered via an astronaut program or on a soft lander… i.e. one part of a much larger scientific payload.

  5. Science Goals of an LXO: Primary: Study of solar wind interaction with the lunar atmosphere and the terrestrial magnetosheath via soft X-ray emission from the solar wind charge exchange (SWCX) process Secondary: All-sky monitor for extra-solar system transient objects

  6. Porter et al. in prep SWCX Mechanism: Heavy solar wind ion in collision with neutral target atom or molecule Aq+ + B → A(q-1)+* + B+ A(q-1)+*→ A(q-1) + hν Process first detected in X-ray emission from comets: Rosat/HRI Image GSFC/MPE A soft X-ray spectrum of the SWCX spectrum from a comet taken with Suzaku demonstrates the need for spectral resolution to distinguish the different constituents of the (variable) solar wind.

  7. Lunar-Based Soft X-ray Science Objectives: • Sites of SWCX emission: • Comets • Planetary atmospheres…including the lunar atmosphere • Geocoronal neutrals at the terrestrial magnetosheath • Inter-stellar neutral atoms within the heliosphere and at the heliospheric boundary

  8. The soft X-ray sky: diffuse emission Soft X-ray background (0.1<E<1.5 keV) has substantial structure from contributions from beyond Solar System sources, namely… Unresolved background from AGN Extended Galactic Halo at 106.5 K Irregular distribution from 106 K plasma in lower Galactic Halo The Local Hot Bubble, a 106 K plasma filling a cavity in the Galactic disk surrounding the Sun. Only in the last decade (from ~1997) has strong/variable emission due to SWCX from terrestrial and inter-planetary sources been recognised as a significant contribution in measurements of the diffuse X-ray background.

  9. Correlation of Soft X-ray Flux (ROSAT) with Solar Wind Correlation of the strength of the solar wind and the strength of the soft X-ray emission as seen by ROSAT (1990’s) in low Earth orbit. ROSAT Long Term Enhancements (LTE) in background attributed to SWCX with interplanetary and geocoronal neutrals. This correlation allows remote sensing of the strength of the solar wind using soft X-ray fluxes as a proxy.

  10. XMM-EPIC detection of SWCX during observation of Hubble Deep Field North Snowden, Collier and Kuntz, 2004, ApJ, 610, 1182

  11. The Moon is located in a prime spot to study SWCX A Lunar X-ray Observatory properly placed on the Moon will be able to observe soft X-ray emission from the interaction of the solar wind with both the lunar atmosphere and the magnetosheath.

  12. Scanning of magnetosheath over the lunar orbit… FOV of an observatory on the lunar surface with a fixed look angle will sweep past the densest part of the magnetosheath each month. Configuration for observations during lunar night.

  13. Magnetosheath contribution…. A model of the strength of the magnetospheric SWCX emission as a function of position around the Earth (at origin) (Robertson & Cravens 2003).This is NOT a static picture: soft X-ray imaging can be used to study the dynamical interaction between the magnetosheath and the solar wind.

  14. Lunar atmosphere contribution…. Simulation of the soft X-ray emission as a function of Position in the lunar sky. (Trávniček et al. 2005) Suggests optimum location to provide greatest contrast is polar position with view zenith angle ~ 900

  15. Secondary (“Added Value”) Science Goals: An LXO as an all-sky-monitor to study time-domain astrophysics in the soft X-ray regime…

  16. RX J1242-11 Chandra/CXC/M.Weiss Secondary (“Added Value”) Science Goals: An LXO as an all-sky-monitor to study time-domain astrophysics in the soft X-ray regime…One example… Stellar Capture events by super-massive black holes in the centre of galaxies Soft X-ray flares lasting weeks-months L > 1043 erg s-1 Rate every ~ 104 – 105 years / galaxy Only handful detected so far by chance

  17. RX J1242-11 Chandra/CXC/M.Weiss Secondary (“Added Value”) Science Goals: An LXO as an all-sky-monitor to study time-domain astrophysics in the soft X-ray regime…One example… Statistics on the frequency and luminosity function of these events will give strong constraints on the mass distribution of SMBHs (with M < 108-9 Msolar) and the co-evolution of SMBHs with their host galaxies.

  18. Telescope proposal and design: Lunar X-ray Observatory (LXO)

  19. Program: Concept Studies for Lunar Sortie Science Opportunities solicitation within NASA Research Announcement: Research Opportunities in Space and Earth Sciences (ROSES) – 2006 Title of Investigation: Lunar-Based Soft X-ray Science PI: Michael Collier PI Institution: NASA/Goddard Space Flight Center Collaborators: Univ. of Kansas, Univ. of Leicester UK, Acad. Sci. Czech Rep. Current Status: NASA has budgeted ~$750K for 5-10 concept studies which are expected to take 6-9 months duration. Proposal has been submitted. Expect result spring 2007.

  20. LSSO concept similar to…. ALSEP: Apollo Lunar Surface Experiment Package Jim Lovell (CMDR Apollo 13) practising Apollo 16 experiments CentralStation RTG PassiveSeismicExperiment Image: www.myspacemuseum.com Image: en.wikipedia.com

  21. Lunar X-ray Observatory (LXO): example configuration Basic Constraints based on ALSEP experience: Mass < 40 kg Power < 75W • Mass < 40 kg (self-contained power system, i.e. solar cells + battery) • Mass < 20 kg (external PSU common to multiple experiments) • Power < 70W if actively cooled with Thermal Electric Cooler (TEC) • Power < 20-30W if passively cooled and operated during lunar night.

  22. Competing Technologies for LXO Detector

  23. Solid state detectors have sufficient energy resolution to spectrally resolve individual solar wind ions Competing Technologies for LXO Detector

  24. Slumped Microchannel Plate: Compact/Lightweight X-ray Optics MCP optic for LOBSTER ASM R = 70 cm (f = 37.5 cm) Single module fov = 300 x 300 Univ. of Leicester Eye structure of a Lobster

  25. LOBSTER optic designed for primary science goal as an ASM so optimises telescope grasp (fov x effective area) Eff. Area of nickel-coated glass MCP optic of varying focal lengths For LXO we would enhance soft X-ray sensitivity: f = 50 cm gives useful 90 x 90 fov in a compact form.

  26. Summary: • The moon is an ideal location for soft X-ray astrophysics, both for studying Solar System SWCX processes directly and for helping to decouple this emission from Cosmic astrophysical sources. • The LXO is practical (the technology is mature and well understood) and is relatively low cost because it is piggy-backing onto a larger program (NASA’s Vision for Space Exploration).

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