X-Ray observations of an extrasolar planetary system

Oct 22, 2010
A computer simulation of the magnetic field strengths of a star that has been affected by the presence of a hot planetary companion orbiting nearby, as seen from above. Credit: Pillitteri et al. 2010

(PhysOrg.com) -- The majority of extra-solar planets (about 278 of them) are more massive than Jupiter. About 20% of this majority group orbit their stars at a distances of less than one-tenth of an astronomical unit (one AU is the average distance of the Earth from the sun, and in our solar system Mercury is four-tenths of an AU from the sun).

These are heated to atmospheric temperatures of thousands of degrees by the close proximity of the star, and so have been nicknamed "hot Jupiters." Astronomers are working to better understand hot Jupiters because they are so common, and because their formation and development are likely to shed light more generally on planetary processes.

Stars emit X-rays from their hot outer atmospheres (the "corona") as strong magnetic fields from the stellar surface heat the gas. SAO astronomers Ignazio Pillitteri, Scott Wolk, Ofer Cohen, Vinay Kashyap, and Heather Knutson, together with two colleagues, studied the possible effects of such an X-ray environment on a nearby hot Jupiter. The X-rays might, for example, significantly heat the planet's atmosphere, accelerate the loss of its gases, alter the chemistry, or otherwise influence its atmosphere's properties.

The scientists used the XMM-Newton satellite to observe a known hot Jupiter system located about sixty-three light-years away; the is slightly less massive and much younger than the sun. This particular hot Jupiter transits its star (that is, passes directly across our line-of-sight to the star). They monitored two episodes of the X-ray emission from the star, each during the planet's passage across its face and during its passage behind the star; during one episode they witnessed some flare activity on the star.

The team then modeled the possible magnetic interactions between the planet and star, finding generally good agreement between theory and observation. This enabled them to conclude that magnetic interactions between the planet and the star can distort the star's coronal structure, and also can enhance the magnetic field in the space between them. Additional observations are needed to probe some of the more complex questions, but the results so far provide new insight into the heating of hot Jupiters. They also caution that age estimates of based on their coronal activity could be suspect if hot Jupiters are present.

Explore further: Millisecond pulsars clearly demonstrate that pulsars are neutron stars

Related Stories

'Hot Jupiter' planets unlikely to have moons

Aug 23, 2010

(PhysOrg.com) -- Planets of the major type so far found outside our solar system are unlikely to have moons, according to new research reported in the August 20 issue of The Astrophysical Journal Letters.

X-Ray Emission from Young Stars

Feb 05, 2010

(PhysOrg.com) -- The star TW Hydrae is located about 150 light-years from earth in the direction of the constellation of Hydrae, the Water Snake. This star is relatively young -- at about 10 million years ...

Early exit for hot Jupiter due to deadly tides

Sep 10, 2010

(PhysOrg.com) -- Bad news for planet hunters: most of the "hot Jupiters" that astronomers have been searching for in star clusters were likely destroyed long ago by their stars. In a paper accepted for publication ...

Recommended for you

How small can galaxies be?

22 hours ago

Yesterday I talked about just how small a star can be, so today let's explore just how small a galaxy can be. Our Milky Way galaxy is about 100,000 light years across, and contains about 200 billion stars. Th ...

The coolest stars

23 hours ago

One way that stars are categorized is by temperature. Since the temperature of a star can determine its visual color, this category scheme is known as spectral type. The main categories of spectral type are ...

Simulations reveal an unusual death for ancient stars

Sep 29, 2014

(Phys.org) —Certain primordial stars—those 55,000 and 56,000 times the mass of our Sun, or solar masses—may have died unusually. In death, these objects—among the Universe's first-generation of stars—would ...

User comments : 0