Distant Star Moved by Tides

Recently, the scientific Journal Nature published an interesting theory online. Astronomers believe that the surface area of a distant star is influenced by the gravity of a huge alien planet. Earth’s moon is responsible for the tides that we observe here on Earth and equally, so the astronomers argue, the surface of a star is influenced by the gravity of the planets that encircle it.

It has been suggested that the planet, which orbits the star WASP 18 in the constellation Phoenix, would induce huge tides in its star. It has ten times the mass of Jupiter (which in turn has the mass of about 318 earths) and is so close to the star that it orbits it in less than a day.

WASP 18 is situated about 100 parsecs (i.e. 3.26 light years or 31 trillion kilometres) away from our sun. The alien planet was first observed when scientist noticed that the star would dim periodically, hinting towards a giant object passing between us and WASP 18. The planet’s existence was then confirmed by detecting Doppler shifts in the light emitted from the star reaching us.

A Doppler shift is the change of the frequency of a wave (here light) due to the Doppler effect caused by a nearby object to the observed phenomenon (in this case the huge alien planet). This phenomenon is used to determine distances in the galaxy as well as measuring gravitational phenomena in distant stars and galaxies.

However, the planet’s orbit posed an enigma. Planets that lie so close to a star would change their orbit from an ellipse to a circle. But the Doppler shift observed hinted towards an elliptical orbit of the giant planet.

However, Arras et al. argued that the gravity of the planet causes huge tides on the star’s surface, causing the observed change in the light path. Thus, the planet actually has a circular orbit.

Last year, another group of astronomers reported that planetary tides were causing the star HAT-P-7 to bulge, causing its brightness to change depending on which side of the star was being observed. However, if Arras’ team is correct, WASP 18 is the first time that astronomers have actually observed a star’s surface rising and falling in response to the gravitation of an orbiting planet. Arras’ team calculated the speed of the tidal rise and fall with 30 meters per second. These are tsunamis of completely different ball parks than those seen on earth. However, the surface of a star is hot burning plasma and not water, with a temperature of thousands of degrees.

Arras, P., Burkart, J., Quataert, E. & Weinberg, N. N. Preprint at http://arxiv.org/abs/1107.6005 (2011)

Hellier, C. et al. Nature 460, 1098-1100 (2009).

Image reproduced from www.nature.com

Sunscreen Expert Launches Free iPhone App

Leading suncare expert, La Roche-Posay, has developed a free mobile iPhone app, My UV Alert, designed to promote sun safe behaviour and encourage the British public to act responsibly in the sun by advising users on the latest UV levels and weather forecast.

My UV Alert uses Met Office weather forecast data to give you the most accurate forecast available.

Available through the ‘iTunes App Store’ and compatible with the Apple iPhone, iPad and iPod Touch,  My UV Alert highlights the potential damaging effects of UVA and UVB rays on the skin and provides users with personalised suncare advice.

The new pioneering app aims to help in the battle against Melanoma and raise awareness of the damaging effects of UVA and UVB rays to skin.

Here are some of the features available on My UV Alert:-

UV profile – answer a short set of questions to determine your skin type and discover your personal UV risk level.

Push alerts – receive location specific notifications on the UV level in your area, tailored to your skin type.  The alerts will advise when UV levels are high and remind you to apply and re-apply sun protection.

Sun protection tips and advice – practical tips and advice to keep skin protected from UV rays, and how to stay safe when spending time outdoors whilst in the UK.

Weather forecast – find out the latest weather forecast in your area.

UV level warning – find out the latest UV level warning in your area.

Share option – access links that allow you to pass the app and advice on to friends and family.

Store locator – to help find the five nearest stockists of leading suncare range, La Roche-Posay Anthelios XL

My UV Alert showcases further information about the La Roche-Posay Anthelios XL range, which offers the highest sun protection from both UVB and UVA rays. The range comes in a variety of formulas for different skin types and is suitable for even the most sensitive of skins. La Roche-Posay is one of the most recommended sunscreens by British dermatologists.

Jane Toner, Marketing Manager for La Roche-Posay states:
“Two thirds of the nation (62%) still does not apply the recommended amount of sun protection. We hope that the My UV Alert iPhone app will help to educate people that UVA and UVB rays can cause both ageing and skin cancer”.

My UV Alert will also highlight the importance of wearing a good quality, broad-spectrum sunscreen all year round, as even when it isn’t sunny or warm outside, UVA and UVB rays can still cause damage to the skin.

To download the My UV Alert iPhone app, search for “My UV Alert” on the iTunes App Store or click here.

Images courtesy of iTunes / La Roche-Posay