Thursday, July 24, 2014

Hubble's Search for Planets with Water

For today's blog posting I decided to check in with the Hubble Mission to see what is new.  Astronomers using the Hubble Space Telescope have gone looking for water vapor in the atmospheres of three planets orbiting stars similar to the Sun — and have come up nearly dry. The planets spectroscopically surveyed have only one-tenth to one one-thousandth the amount of water predicted by standard planet-formation theories.


The above illustration shows what scientists believe the gas giant planet HD 209458b (unofficially named Osiris) looks like.  The solar system in which this planet is located is 150 light-years away in the constellation Pegasus. This is a "hot Jupiter" class planet. Estimated to be 220 times the mass of Earth. The planet's atmosphere is a seething 2,150 degrees Fahrenheit. It orbits very closely to its bright sun like star, and the orbit is tilted edge-on to Earth. This makes the planet an ideal candidate for the Hubble Space Telescope to be used to make precise measurements of the chemical composition of the giant's atmosphere as starlight filters though it. To the surprise of astronomers, they have found much less water vapor in the atmosphere than standard planet-formation models predict. Since water is a necessary prerequisite for life as we know it,.the search for water-bearing terrestrial worlds may be more challenging than thought. Scientists may have to revisit their theories of planet formation.

This graph compares observations with modeled infrared spectra of three hot-Jupiter-class exoplanets that were spectroscopically observed with the Hubble Space Telescope. The red curve in each case is the best-fit model spectrum for the detection of water vapor absorption in the planetary atmosphere. The blue circles and error bars show the processed and analyzed data from Hubble's spectroscopic observations.

NASA, ESA, N. Madhusudhan (University of Cambridge), and A. Feild and G. Bacon (STScI)

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