Kategorie: Exoplaneten

US astronomers say the Hubble Space Telescope has allowed them to study for the first time the atmospheric structure of a planet orbiting another star. Hubble discovered a dense upper layer of hot hydrogen gas where the super-hot planet’s atmosphere is bleeding into space. The planet, designated HD 209458b, is unlike any world in our solar system. Researchers say it orbits so close to its star and becomes so hot that its gas is streaming into space, making the planet appear to have a comet-like tail. The new research reveals the layer in the planet’s upper atmosphere where the gas becomes so heated it escapes, like steam rising from a boiler.
https://hubblesite.org/contents/news-releases/2007/news-2007-07.html

Astronomers believe they might be able to find intelligent extraterrestrial life using a Low Frequency Demonstrator of the Mileura Wilde-Field Array now under construction in Australia. The „eavesdropping“ would be looking for unintentional signals from planets within about 30 light-years of us.

Eavesdropping on the Universe

Observations from NASA’s Spitzer Space Telescope show that gas giants either form within the first 10 million years of a sun-like star’s life, or not at all. The study offers new evidence that gas-giant planets must form early in a star’s history. The lifespan of sun-like stars is about 10 billion years. Ilaria Pascucci of the University of Arizona Steward Observatory in Tucson led a team of astronomers who conducted the most comprehensive search for gas around 15 different sun-like stars, most with ages ranging from 3 million to 30 million years. The scientists used Spitzer’s heat-seeking infrared eyes to search for warm gas in the inner portions of star systems, an area comparable to the zone between Earth and Jupiter in our own solar system. In addition, team member Michael Meyer of the UA Steward Observatory and their colleagues probed for cold gas in the outer regions of these star systems with the Arizona Radio Observatory’s 10-meter Submillimeter Telescope (SMT) on Mount Graham, Arizona. The outer zones of these star systems are analogous to the region around Saturn’s orbit and beyond in our own solar system. All of the stars in the study – including those as young as a few million years – have less than 10 percent of Jupiter’s mass in gas swirling around them. This indicates that gas giant planets like Jupiter and Saturn have already formed in these young solar system analogs – or they never will.

https://news.arizona.edu/story/gas-giants-jump-planet-formation-early

https://www.spitzer.caltech.edu/news/ssc2007-02-gas-giants-form-quickly

Hubble observed a „blizzard“ of particles in a disk around a young star, revealing the process by which planets grow from tiny dust grains. The particles are as fluffy as snowflakes and are roughly ten times larger than typical interstellar dust grains. They were detected in a disk encircling the 12-million-year-old star AU Microscopii. The star is 32 light-years away in the southern constellation of Microscopium.
https://hubblesite.org/contents/news-releases/2007/news-2007-02.html

The COROT space telescope, designed to search for planets not much bigger than Earth, launched into space at 1423 GMT on Wednesday from the Baikonur cosmodrome in Kazakhstan. The mission is expected to provide a better understanding of planets smaller than Saturn, of which only a small number of examples are known so far. The vast majority of the more than 200 extrasolar planets found to date have been detected from the ground by watching for the slight gravitational tug they exert on their parent stars, called the radial velocity technique. Most of these planets are similar in mass to Jupiter or even heavier, because these „gas giants“ are the easiest to detect. But the new telescope, called COnvection ROtation and planetary Transits (COROT), will be able to detect much smaller planets. The COROT mission is led by France’s Centre National d’Etudes Spatiales (CNES) with participation from the European Space Agency (ESA). COROT will start its scientific observing campaign around the end of January 2007, after mission managers have tested its instruments to make sure everything is working properly. The entire mission is scheduled to last two-and-a-half years.

COROT on its way

On December 27, 2006, COROT is to be launched into space on a unique astronomy mission: its twin goals are to detect exoplanets orbiting around other stars and to probe the mysteries of stellar interiors as never before. COROT is a European mission led by the French National Space Agency CNES.

Europe looks forward to COROT launch

An asteroid has been ripped to shreds and vaporized after straying too close to a hot white dwarf star, observations suggest. The asteroid was probably flung towards the white dwarf by the gravity of one or more unseen planets. The evidence comes in the form of a hot ring of metallic vapour around a white dwarf called SDSS 1228+1040. Researchers led by Boris Gänsicke of the University of Warwick, UK, found signs of the disc in light spectra from the white dwarf acquired by the Sloan Digital Sky Survey’s 2.5-metre telescope at Apache Point, New Mexico, US, the 4.2-metre William Herschel Telescope on the Canary Islands, and by Caltech’s orbiting Galaxy Evolution Explorer (GALEX). The spectra indicate that a disc containing calcium, magnesium, and iron gas is orbiting the white dwarf at a distance 100 times closer than Mercury’s orbit around the Sun. At this distance, intense radiation from the white dwarf heats the gas to 5000 K. The spectra also shows that the white dwarf’s atmosphere is enriched in magnesium. That indicates material from the disc is falling onto the star, since the star’s own surface gravity is so great that its own heavy elements should have already sunk towards its centre and out of sight.

A gaseous metal disk around a white dwarf

Using the Canada-France-Hawaii telescope, an international team of researchers has just discovered a magnetic field on Tau Bootis, a star orbited by a giant planet on a close-in orbit: the first ever detection of this kind!

Tau Bootis magnetic Field

The Spitzer Space Telescope has revealed that a Jupiter-like gas giant planet circling very close to its sun is always as hot as fire on one side, and potentially as cold as ice on the other.
https://www.nasa.gov/vision/universe/starsgalaxies/spitzer-20061012.html

The Hubble Space Telescope turned its gaze towards a relatively nearby Jupiter-sized world recently. The planet orbits the Sun-like star Epsilon Eridani, which is located only 10,5 light-years away. This makes the planet so close that it could be directly observable by Hubble and large ground-based observatories. The best opportunity will come in 2007, when the planet makes its closest approach to its parent star, and the reflected light should make it observable with our best instruments.
Hubble Observations Confirm that Planets Form from Disks Around Stars