* Astronomy

A team of University of Hertfordshire astronomers led by Dr David Pinfield of the Centre for Astrophysics Research is leading a major new European collaboration to search for and study planets around other stars (extra-solar planets).
Funded with £2.75 million from the European Commission, this research and technology network will focus on the search for rocky planets around cool stars and the development of future space-based technology to study extra-solar planets.
Cool stars are much fainter than the Sun and are thus challenging to study, but they play a major role in astrophysics; they are the most common type of star in our Galaxy.

"This fast moving field is at the forefront of modern astrophysics, and is moving towards a goal of discovering terrestrial planets like the Earth around stars other than the Sun. Learning about the diverse range of planetary systems that exist around other stars allows us to better understand our own place in the universe, and will reveal the extent of possible habitats for life elsewhere" - Dr David Pinfield.

The project is built on the team's international collaboration with leading research institutes in the UK (UH and Cambridge), Spain (Canary Islands and Madrid), Germany (Munich) and Ukraine (Kiev), and the space engineering company Astrium (based in Stevenage).
Over its four year life-time (Dec 2008 - Nov 2012) the project will employ fifteen young doctoral and postdoctoral researchers to carry out new research, work with industry on technology development, and receive training through a range of science and technology activities.
The network will specifically pursue extra-solar planets that transit (pass in-front of their host star during their orbit) - currently an extremely active area of astronomy. For cool stars this technique is sensitive to smaller planets that could be warm rocky worlds.
By exploiting new survey facilities that are being led by Dr Pinfield and his network, they aim to improve their understanding of the broad nature of extra-solar planet populations, and explore new extra-solar planet territory around the coolest stars in our galaxy. Intersectorial activities will be carried out jointly at UH and Astrium, and will centre on the European Space Agency's Cosmic Vision 2015-2025 programme to implement the next generation of space-based observatories.

"The project will thus be looking to the future as well as focussing on the ongoing search for and study of planets around other stars" - Dr David Pinfield.

Source: University of Hertfordshire

Title: Transit timing effects due to an exomoon
Authors: David M. Kipping
(Version v2)

As the number of known exoplanets continues to grow, the question as to whether such bodies harbour satellite systems has become one of increasing interest. In this paper, we explore the transit timing effects that should be detectable due to an exomoon and predict a new observable. We first consider transit time variation (TTV), where we update the model to include the effects of orbital eccentricity. We draw two key conclusions: 1) In order to maintain Hill stability, the orbital frequency of the exomoon will always be higher than the sampling frequency. Therefore, the period of the exomoon cannot be reliably determined from TTV, only a set of harmonic frequencies. 2) The TTV amplitude is proportional to M_S a_S where M_S is the exomoon mass and a_S is the semi-major axis of the moon's orbit. Therefore, M_S and a_S cannot be separately determined. We go on to predict a new observable due to exomoons - transit duration variation (TDV). We derive the TDV amplitude and conclude that its amplitude is not only detectable, but the TDV signal will provide two robust advantages: 1) The TDV amplitude is proportional to M_S a_S^{-½} and therefore the ratio of TTV and TDV allows for a separate determination of M_S and a_S. 2) TDV has a 90 degrees phase difference to the TTV signal, making it an excellent complementary technique.

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This artist's animation shows first what a fiery hot star and its close-knit planetary companion might look like close up in visible light, then switches to infrared views. In visible light, a star shines brilliantly, overwhelming the little light that is reflected by its planet. In infrared, a star is less blinding, and its planet perks up with a fiery glow.
Astronomers using NASA's Spitzer Space Telescope took advantage of this fact to directly capture the infrared light of two previously detected planets orbiting stars outside our solar system. Their findings revealed the temperatures and orbits of the planets. Upcoming Spitzer observations using a variety of infrared wavelengths may provide more information about the planets' winds and atmospheric compositions.
In this animation, the colours represent real differences between the visible and infrared views of the system. The initial visible view shows what our eyes would see if we could witness the system close up. The hot star is yellow, because like our Sun, it is brightest in yellow wavelengths. The warm planet, on the other hand, is brightest in infrared light, which we can't see. Instead, we would see the glimmer of star light that the planet reflects.
In the second half of the animation, the colours reflect what our eyes might see if we could retune them to the invisible, infrared portion of the light spectrum. The hot star is less bright in infrared light than in visible and appears fainter. The warm planet peaks in infrared light, so is shown brighter. Their hues represent relative differences in temperature. Because the star is hotter than the planet, and because hotter objects give off more blue light than red, the star is depicted in blue, and the planet, red.
The overall look of the planet is inspired by theoretical models of hot, gas giant planets. These "hot Jupiters" are similar to Jupiter in composition and mass, but are expected to look quite different at such high temperatures. The models are courtesy of Drs. Curtis Cooper and Adam Showman of the University of Arizona, Tucson.

Credit: NASA/JPL-Caltech/R. Hurt (SSC)

Moons outside our Solar System with the potential to support life have just become much easier to detect, thanks to research by an astronomer at University College London (UCL).
David Kipping has found that such moons can be revealed by looking at wobbles in the velocity of the planets they orbit. His calculations, which appear in the Monthly Notices of the Royal Astronomical Society today, not only allow us to confirm if a planet has a satellite but to calculate its mass and distance from its host planet ­ factors that determine the likely habitability of a moon.

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