Discovery of a pulsating star that hosts a giant planet

January 18, 2011, Universitat Autonoma de Barcelona

Recently published in an article of the Astronomy & Astrophysics journal, a group of Spanish researchers from the Institute of Space Sciences (IEEC-CSIC) at Universitat Autonoma de Barcelona has discovered, for the first time, a delta Scuti pulsating star that hosts a hot giant transiting planet. The study was carried out by the PhD student, Enrique Herrero, the researcher Dr. Juan Carlos Morales, the exoplanet expert, Dr. Ignasi Ribas, and the amateur astronomer, Mr. Ramón Naves.

WASP-33 (also known as HD15082) is hotter, more massive than the Sun (1.5 Msun) and is located at a distance of 378 light years away, in the constellation of Andromeda. It has the peculiarity of being a star that pulsates radially, like a balloon that inflates and deflates continuously, and non-radially, like the tides in Earth's oceans caused by the presence of the moon, which deforms the bodies of water between the poles and the equator.

This star hosts a giant planet, WASP-33b, that was detected in 2006 through the transiting method. The planet's mass is four times the mass of Jupiter and it orbits the star at such a high speed that it only takes 1.2 days to complete its orbit. This very short orbital period indicates its extreme proximity to the star, 0.02 astronomical units (AU) when Mercury, the closest planet to the Sun, is at 0.39 AU. This planet is quite particular because it has a retrograde orbit and, evenmore, its orbit is quite inclined in angle respect to the star's equator.

The study also suggests that the star's pulsations could be caused by the presence of the giant planet, something never seen before in any other planetary system. A small periodic signal, visible in the overall signal during the transit of the planet, called the attention of the researchers and through a thorough study, the pulsating modes of the star were determined and their possible relationship with the planet.

Apart from being a pioneering study in the field, it is noteworthy to mention that the observations have been obtained from professional and amateur observatories. For the first time in its recent activity history, the Montsec Astronomical Observatory (OAdM) has provided most of the observations used for this research. In addition, the amateur astronomer R. Naves, from the Montcabrer Observatory, has provided excellent data, revealing the great importance of Professional-Amateur collaborations in this field.

Therefore, the WASP-33 system represents a landmark in the world of exoplanets since it may provide vital information on pulsations modes that occur in , the effects of tides between stars and planets and the dynamical evolution of planetary systems.

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More information: 1 UA= 149.597.870 km

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5 / 5 (2) Jan 18, 2011
Ever since I first read about these gas giant exoplanets that are very close to their host stars, I've wondered how they can maintain their gaseous atmospheres against escape into space at such high temperatures. Over millions or billions of years since they came into existence, you'd think they'd have evaporated into nothingness under the constant influence of a close hot star.
not rated yet Jan 18, 2011
Well it also gets gas from it's stars atmosphere. Plus since it is so large it can retain it's atmospheric gas.
1 / 5 (1) Jan 18, 2011
If the gas giant has a strong magnetic field, shouldn't that be largely responsible for preserving it's atmosphere?
not rated yet Jan 19, 2011
I may have missed something, but I don't actually see a reference to it being a gas giant -- just 4 times bigger than jupiter. Could be a ball of rock. Or magma, at that distance.
1 / 5 (3) Jan 19, 2011
"located at a distance of 378 light years away, in the constellation of Andromeda"

Um, isn't the Andromeda galaxy 2.5 million light years away, not 378.... Or are they referencing an arm of the Milky Way?
not rated yet Jan 19, 2011
I may have missed something, but I don't actually see a reference to it being a gas giant -- just 4 times bigger than jupiter. Could be a ball of rock. Or magma, at that distance.

No, I just assumed it was a gas giant with the size reference to Jupiter. You're right: it isn't specified what it's composition is.

Um, isn't the Andromeda galaxy 2.5 million light years away, not 378...

You're right about the Andromeda galaxy. However, the article is talking about a planet in the Andromeda constellation.
not rated yet Jan 19, 2011
Terrible_Bohr, thanks. I'm unaccustomed to the sky location as a reference in articles.
5 / 5 (1) Jan 19, 2011
Earlier studies of WASP-33 (aka HD15082b)concluded that it is indeed a gas giant with a bloated radius 1.46 times that of Jupiter. The study noted that WASP-33 is the most strongly irradiated planet yet found and related to other known hot Jupiters. Several possibilities for its internal structure (rock-metal core, etc.) and evolutionary history wrt its orbit are briefly discussed:


The paper discussed in this article is available here:

not rated yet Jan 27, 2011
the planet's tide is like a finger stroking the rim of a wine glass -- the star -- to make it sing (vibrate).

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