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exoplanets (4)

Galactic Armageddon...

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The planet, called WASP-12b, is so close to its sunlike star that it is superheated to nearly 2,800 degrees Fahrenheit and stretched into a football shape by enormous tidal forces. The atmosphere has ballooned to nearly three times Jupiter's radius and is spilling material onto the star. The planet is 40 percent more massive than Jupiter.

 

Topics: Astronomy, Astrophysics, Exoplanets, White Dwarfs


Some rocky exoplanets bear a striking resemblance to Earth, according to Alexandra Doyle, Edward Young and colleagues at the University of California at Los Angeles. The team used the properties of light coming from six white-dwarf stars to calculate how much oxygen, iron and other elements were present in planets that once orbited the stars. Their observations suggest that these planets – which were consumed by their stars long ago – have the same geophysical and geochemical properties as Earth. While astronomers are able to observe rocky exoplanets, working out what they are made of is difficult and this research provides important clues regarding the composition of these Earth-like objects.

White dwarfs are the ancient remnants of stars that had masses less than about 10 Suns. This means that most stars in the Milky Way will eventually become white dwarfs – including the Sun. Many white dwarfs would have had planets, which would have been consumed by the stars at some point in their stellar evolution. The atmosphere of a white dwarf is expected to comprise only the lightest elements – hydrogen and helium – so the presence of heavier substances in the stellar atmosphere such as magnesium, iron and oxygen means that the star has probably ingested rocky planets or asteroids.

 

Doomed exoplanets were much like Earth, Hamish Johnston, Physics World

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A Year of TESS...

 

Topics: Exoplanets, NASA, Planetary Science, Space Exploration, Star Trek


"Space: the final frontier. These are the voyages of the starship Enterprise. Her five-year mission: to explore strange new worlds. To seek out new life and new civilizations. To boldly go where no one has gone before." (Star Trek: The Captain's Oath)

“Kepler discovered the amazing result that, on average, every star system has a planet or planets around it. TESS takes the next step. If planets are everywhere, let’s find those orbiting bright, nearby stars because they’ll be the ones we can now follow up with existing ground and space-based telescopes, and the next generation of instruments for decades to come.” Padi Boyd, TESS project scientist, NASA GSFC

- HD 21749c, the first Earth-size planet the mission has found. The world orbits a K-class star with about 70 percent of the mass of the Sun, located 53 light years away in the constellation Reticulum, one of two planets identified in this system;

- A number of multi-planet systems, like that around L98-59, which includes a planet (L98-59b) between the size of Earth and Mars, the smallest yet found by TESS. Here the host star is an M-dwarf about a third the mass of the Sun, 35 light years away in the constellation Volans;

- Three exocomets identified in the Beta Pictoris system. A comet’s lightcurve differs significantly from that of a transiting planet because of the extended cometary tail. These discoveries demonstrate the ability of TESS to identify tiny objects around young, bright stars, and should lead to future exocomet detections that can supply information about planet formation;

- Six supernovae occurring in other galaxies, among them ASASSN-18rn, ASASSN-18tb and ATLAS18tne, found before ground-based surveys could identify them.

 

TESS: Concluding First Year of Observations, Paul Gilster, Centauri Dreams

#P4TC: TESS... August 2, 2018

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Brine Europa...

Salt-laden water welling up from below gives Europa’s fissures and cracks their distinctive color.
Credit: NASA, JPL-Caltech and SETI Institute

 

Topics: Astrobiology, Exoplanets, Planetary Exploration, SETI


The sea sloshing beneath the icy surface of Jupiter’s moon Europa just might be the best incubator for extraterrestrial life in our solar system. And yet it is concealed by the moon’s frozen outer shell—presenting a challenge for astrobiologists who would love nothing more than to peer inside. Luckily they can catch a partial glimpse by analyzing the flavor of the surface. And the results are salty.

A new study published this week in Science Advances suggests that sodium chloride—the stuff of table salt—exists on Europa’s surface. Because the exterior is essentially formed from frozen seawater, the finding suggests that Europa’s hidden sea is drenched in table salt—a crucial fact for constraining the possibilities for life on the alien world.

Not that scientists have tasted a slice of the distant moon. To analyze Europa’s composition, astronomers study the light emanating from its surface, splitting it into a rainbow-like spectrum to search for any telltale absorption or emission lines that reveal the world’s chemistry. There is just one problem: Ordinary table salt is white and thus gives off a featureless spectrum. But harsh radiation—which exists at Europa’s surface in abundance—just might add a dash of color. That much was realized in 2015 when two NASA planetary scientists Kevin Hand and Robert Carlson published a study suggesting the yellowish-brown gunk on Europa might be table salt baked by radiation. To reach that conclusion, Hand and Carlson re-created the conditions on Europa within vacuum chambers—or as Hand calls them, “stainless steel shiny objects that are humming and whizzing.” Next, they placed table salt into those chambers, lowered the pressures and temperatures to simulate Europa’s surface, and blasted the samples with an electron gun to simulate the intense radiation.

 

Water on Europa—with a Pinch of Salt, Shannon Hall, Scientific American

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Remnants...

An artist's impression of the planetesimal orbiting on a 2-hour period within the gaseous disc around SDSS J1228+1040 (by Mark Garlick).

 

Topics: Astronomy, Astrophysics, Exoplanets, Spectrograph, White Dwarfs


When the hydrogen fuel that keeps a star like our sun burning brightly is exhausted, the star expands into a red giant before collapsing into a hot, dense white dwarf. Although the stellar swelling engulfs nearby planets, theoretical models suggest that some planets and planetary cores up to hundreds of kilometers in diameter can survive the star’s death and fall into closer orbit. But identifying solid bodies around a dim stellar core is difficult. Now Christopher Manser (University of Warwick) and colleagues have used a new spectroscopic method to identify a planetesimal orbiting a white dwarf 400 light-years from our solar system.

Astronomers have discovered most exoplanets—including an asteroid-like body orbiting a white dwarf—via the transit method, identifying periodic dimming as an object passes in front of its host star. But the method requires a lucky geometry of the planetary system’s orbital plane relative to Earth. Manser and his team instead turned to short-cadence optical spectroscopy using data from the 10.4 m Gran Telescopio Canarias in Spain. They focused on one of just a few white dwarfs that, based on metal emission lines in the stellar and disk spectra, are suspected to be surrounded by disks of gas and dust. Minute-by-minute observations over several nights in 2017 and 2018 let the researchers deconstruct the light emanating from the disk and determine how much variation had occurred over a year.

 

A glimpse of a planetary system’s final stages, Rachel Berkowitz, Physics Today

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