Image credit: Laura Danly (STScI), C. Elise Albert (United States Naval Academy), Kip D. Kuntz (STSCI), NASA, ESA
Written by
Dr Parul Janagal
Dr Parul Janagal earned her PhD from the Indian Institute of Technology Indore, where she specialised in the study of emission mechanisms of radio pulsars. She now applies her knowledge of astrophysics at Blue Skies Space, fostering strategic collaborations.
When we think about space telescopes, giants like the Hubble Space Telescope (HST) or James Webb Space Telescope (JWST) often come to mind. However, the International Ultraviolet Explorer (IUE) has made profound scientific contributions, proving that smaller telescopes can also contribute to significant discoveries. Launched in 1978 through a collaboration between NASA, ESA, and the United Kingdom’s Science and Engineering Research Council, IUE was one of the first space telescopes explicitly designed for Ultraviolet (UV) observations [1].
Despite being initially planned for three years, it operated for 18 long years, making it one of the longest operational space observatories. IUE’s mission was straightforward yet ambitious: to capture the UV spectra from various celestial objects, providing data otherwise inaccessible from Earth due to its absorption by our atmosphere.
Since its launch, the data observed by IUE has played a pivotal role in advancing numerous areas of astronomical research and contributing to over 10,000 research papers. Among its many insights, IUE provided valuable data on the composition, structure, and dynamics of the interstellar medium (ISM) [2]. The UV data, combined with Infrared and optical data, helped derive an average extinction law for the diffused and dense regions of the ISM [3].
The short-wavelength spectrograph on board IUE played a crucial role in studying Jupiter’s polar auroras, making it the first observatory to definitively identify polar auroras on another planet [4]. IUE’s observations of Venus and Jupiter enriched our understanding of their atmospheric compositions and dynamics, illustrating the interaction between solar radiation and planetary atmospheres [5,6].
By observing comets like 1P/Halley, IUE illuminated the composition and behaviour of these celestial bodies, providing clues about the early solar system [7,8]. Observations conducted with the IUE spanned a diverse array of stellar objects, including binary star systems, hot massive stars, cool stars, etc., [9,10,11,12]. The IUE data was instrumental in unravelling the fascinating spectral changes that occur in late-type stars and early-type galaxies [13]. Additionally, observations of active galactic nuclei (AGN) and quasars using IUE significantly enriched our understanding of these energetic phenomena [14,15].
IUE’s accessible data and cost-effective nature democratised space research, involving a broader range of participants, including students and amateur astronomers. This allowed many to engage directly in groundbreaking research, fostering a new generation of scientists and demonstrating the potential of small telescopes in advancing our understanding of the universe. IUE’s 45-centimetre mirror may seem modest compared to the likes of JWST, but its scientific impact was monumental. Small telescopes like IUE demonstrate that cost-effective, agile missions can achieve significant scientific progress. These smaller missions can quickly adapt to new scientific questions, fill observational gaps, and complement larger telescopes by providing additional data.
Mauve, following in the footsteps of IUE, is poised to deliver novel insights. With modern technology and a refined focus on scientific objectives, Mauve exemplifies how small satellites can continue to make big impacts in the field of astronomy.
Figure 4 highlights the estimated light collection capabilities of both IUE and Mauve. The effective area of an instrument is the area of an ideal telescope with 100% efficiency in all its components (from the mirror to the detector chain) with the same “light capturing” capacity the real telescope being discussed (with all its inefficiencies, light-losses, etc.). One can notice the similar performance of “light capture” of IUE and Mauve, driven by Mauve’s much more effective detection chain, despite the difference in size of the respective satellites. This serves as a reminder that we are now in an era where small satellites with modern electronic components can be genuinely recognised for their scientific potential.
It is important to note that these facilities have unique scientific objectives and associated designs. Mauve is designed to study the spectral energy distribution evolution of bright targets, while IUE was geared towards higher-resolution spectral observations.
IUE’s legacy is a powerful reminder that small, focused missions can deliver deep scientific insights and significantly advance our understanding of the universe. As we look to the future, embracing the potential of small satellites will be crucial for continuous innovation and discovery, inspiring awe and wonder about the vastness of space.
References
[1] Boggess, A., “The IUE spacecraft and instrumentation”, Nature, vol. 275, no. 5679, pp. 372–377, 1978. doi:10.1038/275372a0.
[2] Grewing, M., “IUE observations of the interstellar medium.”, Nature, vol. 275, pp. 394–400, 1978. doi:10.1038/275394a0.
[3] Cardelli, J. A., Clayton, G. C., and Mathis, J. S., “The Relationship between Infrared, Optical, and Ultraviolet Extinction”, The Astrophysical Journal, vol. 345, IOP, p. 245, 1989. doi:10.1086/167900.
[4] Clarke, J. T., Moos, H. W., Atreya, S. K., and Lane, A. L., “Observations from earth orbit and variability of the polar aurora on Jupiter”, The Astrophysical Journal, vol. 241, IOP, pp. L179–L182, 1980. doi:10.1086/183386.
[5] Feldman, P. D., Moos, H. W., Clarke, J. T., and Lane, A. L., “Identification of the UV nightglow from Venus”, Nature, vol. 279, no. 5710, pp. 221–222, 1979. doi:10.1038/279221a0.
[6] Owen, T., “Observations of the spectrum of Jupiter from 1500 to 2000 A with the IUE”, The Astrophysical Journal, vol. 236, IOP, pp. L39–L42, 1980. doi:10.1086/183194.
[7] Feldman, P. D., “IUE Observations of Comet p/ Halley – Evolution of the Ultraviolet Spectrum Between 1985SEP and 1986JUL”, Astronomy and Astrophysics, vol. 187, p. 325, 1987.
[8] Weaver, H. A., Feldman, P. D., Festou, M., A’Hearn, M. F., and Keller, H. U., “IUE observations of faint comets”, Icarus, vol. 47, no. 3, pp. 449–463, 1981. doi:10.1016/0019-1035(81)90193-7.
[9] Linsky, J. L., “IUE observations of cool stars: alf Aur, HR 1099, lam and EPS Eri.”, Nature, vol. 275, pp. 389–394, 1978. doi:10.1038/275389a0.
[10] Heap, S. R., “IUE observations of hot stars: HZ 43, BD +75 325, NGC 6826, SS Cyg, eta Car.”, Nature, vol. 275, pp. 385–388, 1978. doi:10.1038/275385a0.
[11] Hack, M. and Selvelli, P. L., “IUE observations of the eclipsing binary Epsilon Aurigae”, Nature, vol. 276, no. 5686, pp. 376–378, 1978. doi:10.1038/276376a0.
[12] Gerbaldi, M., Megessier, C., and Morguleff, N., “The ultraviolet variation of the AP star 21 COM”, in The First Year of IUE, 1979, pp. 91–99.
[13] Bruzual A., G., “Spectral evolution of galaxies. I. Early-type systems.”, The Astrophysical Journal, vol. 273, IOP, pp. 105–127, 1983. doi:10.1086/161352.
[14] Penston, M. V., Clavel, J., Snijders, M. A. J., Boksenberg, A., and Fosbury, R. A. E., “Far ultraviolet line profiles in the Seyfert galaxy NGC 4151.”, Monthly Notices of the Royal Astronomical Society, vol. 189, OUP, pp. 45P–50, 1979. doi:10.1093/mnras/189.1.45P.
[15] Baldwin, J. A., Rees, M. J., Longair, M. S., and Perryman, M. A. C., “The Lα/Hβ/Pα ratio in the quasar PG 0026+129.”, The Astrophysical Journal, vol. 226, IOP, pp. L57–L59, 1978. doi:10.1086/182830.
[16] Kjeldseth-Moe, O., Van Hoosier, M.E., Bartoe, J.D.F., & Brueckner, G.E. 1976, “A Spectral Atlas of the Sun between 1175 and 2100 Angstroms”, US Naval Research Laboratory Report 8057