Institute of Astronomy

Astronomy News

Haze heats Pluto’s atmosphere yet explains its cold temperature

16 November 2017 - 9:44am

Haze heats Pluto’s atmosphere yet explains its cold temperature

Nature 551, 7680 (2017). doi:10.1038/nature24465

Authors: Xi Zhang, Darrell F. Strobel & Hiroshi Imanaka

Pluto’s atmosphere is cold and hazy. Recent observations have shown it to be much colder than predicted theoretically, suggesting an unknown cooling mechanism. Atmospheric gas molecules, particularly water vapour, have been proposed as a coolant; however, because Pluto’s thermal structure is expected to be in radiative–conductive equilibrium, the required water vapour would need to be supersaturated by many orders of magnitude under thermodynamic equilibrium conditions. Here we report that atmospheric hazes, rather than gases, can explain Pluto’s temperature profile. We find that haze particles have substantially larger solar heating and thermal cooling rates than gas molecules, dominating the atmospheric radiative balance from the ground to an altitude of 700 kilometres, above which heat conduction maintains an isothermal atmosphere. We conclude that Pluto’s atmosphere is unique among Solar System planetary atmospheres, as its radiative energy equilibrium is controlled primarily by haze particles instead of gas molecules. We predict that Pluto is therefore several orders of magnitude brighter at mid-infrared wavelengths than previously thought—a brightness that could be detected by future telescopes.

Planetary science: Haze cools Pluto's atmosphere

16 November 2017 - 9:44am

Planetary science: Haze cools Pluto's atmosphere

Nature 551, 7680 (2017). doi:10.1038/551302a

Authors: Robert A. West

Modelling suggests that Pluto's atmospheric temperature is regulated by haze, unlike the other planetary bodies in the Solar System. The finding has implications for our understanding of exoplanetary atmospheres. See Letter p.352

We found our galactic twin 180 million light years away

16 November 2017 - 9:43am

Astronomers have spotted a trio of galaxies that look remarkably like the giant spiral of the Milky Way and its two brightest companions, the Magellanic Clouds

We’ve just found a nearby exoplanet that could be right for life

16 November 2017 - 9:42am

A newly discovered nearby world is probably close in size and temperature to Earth. This exoplanet might be able to host life because of its unusually calm star

Free-fall experiment could test if gravity is a quantum force

16 November 2017 - 9:42am

The effort to reconcile general relativity with quantum mechanics always hits one snag: gravity. An experiment could finally tell us if it is a quantum force

A layer of haze keeps Pluto’s atmosphere extremely cold

16 November 2017 - 9:41am

Pluto is far from the sun, so astronomers expect its atmosphere to be cold, but it's colder than predicted. Now we know that soot sends the sun’s heat back into space

Closest Temperate World Orbiting Quiet Star Discovered

16 November 2017 - 9:39am
A temperate Earth-sized planet has been discovered only 11 light-years from the Solar System by a team using ESO’s unique planet-hunting HARPS instrument. The new world has the designation Ross 128 b and is now the second-closest temperate planet to be detected after Proxima b. It is also the closest planet to be discovered orbiting an inactive red dwarf star, which may increase the likelihood that this planet could potentially sustain life. Ross 128 b will be a prime target for ESO’s Extremely Large Telescope, which will be able to search for biomarkers in the planet's atmosphere.

How do you find a star cluster? Easy, simply count the stars

16 November 2017 - 9:37am

It's the perfect meeting of old and new. Astronomers have combined the latest data from ESA's Gaia mission with a simple analysis technique from the 18th century to discover a massive star cluster that had previously escaped detection. Now, subsequent investigations are helping reveal the star-forming history of our Galaxy, the Milky Way.

Nearby planet is prime target in search for life

16 November 2017 - 9:36am

Astronomers have found a cool, Earth-sized planet that's relatively close to our Solar System.

New NASA Mission Concept Aimed at Studying Why Planets Lose their Atmospheres

15 November 2017 - 9:48am
Portal origin URL: New NASA Mission Concept Aimed at Studying Why Planets Lose their AtmospheresPortal origin nid: 413250Published: Tuesday, November 14, 2017 - 10:46Featured (stick to top of list): noPortal text teaser: A team of NASA scientists want to use Earth as a laboratory to understand how planets lose their atmospheres and has proposed a mission that the agency recently selected as one of five for further consideration as a possible NASA Explorer mission.Portal image: This artist’s rendition shows MEME-X’s dual spacecraft as they observe the aurora from an altitude like that of the ISS.Science Categories: Sun

Webb's first space targets chosen

14 November 2017 - 9:14am

Gas giant Jupiter, organic molecules in star-forming clouds and baby galaxies in the distant Universe are among the first targets for which data will be immediately available from the James Webb Space Telescope once it begins casting its powerful gaze on the Universe in 2019.

Herschel discovers galaxy merger in the very early Universe

14 November 2017 - 9:13am

What seemed at first like a rare instance of a huge, ancient galaxy revealed itself to be an even rarer pair of extremely massive galaxies, seen on the brink of merging when the Universe was only a billion years old.

Neptune’s other moons were normal until Triton crashed the party

14 November 2017 - 9:12am

Neptune’s moons are unlike anything in the solar system, thanks to Triton barrelling in and laying waste to the moons that were there before it

Should we seed life through the cosmos using laser-driven ships?

14 November 2017 - 9:11am

Our galaxy may have billions of habitable worlds. A proposal to spread life says we should use giant lasers and light sails to send microbes out to them

Neptune’s other moons were normal until Triton crashed the party

13 November 2017 - 9:32am

Neptune’s moons are unlike anything in the solar system, thanks to Triton barrelling in and laying waste to the moons that were there before it

Venus and Jupiter conjunction: Sky-watchers witness dawn display

13 November 2017 - 9:29am

Enthusiasts were up before dawn for best UK views of the two brightest planets appearing together.

Giant star smash-up may have made the biggest neutron star ever

10 November 2017 - 9:26am

The collision that produced recent gravitational waves may have left behind the biggest neutron star ever seen. But it might have collapsed into a black hole

Tracking the first interstellar asteroid back to its home star

10 November 2017 - 9:24am

Last month, astronomers saw the first asteroid from outside our solar system speed by. Now, they're tracing its orbit back to find out where it came from

Observations of a Comet’s First Passage Through the Solar System Reveal Unexpected Secrets

10 November 2017 - 9:23am
Portal origin URL: Observations of a Comet’s First Passage Through the Solar System Reveal Unexpected Secrets Portal origin nid: 413023Published: Thursday, November 9, 2017 - 11:58Featured (stick to top of list): noPortal text teaser: Researchers onboard NASA’s flying observatory examined a new comet as it made its first approach through our solar system.Portal image: Artist’s depiction of Comet C/2012 K1 (also called Pan-STARRS) and its coma during its first approach into the solar system.Science Categories: Universe

Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star

9 November 2017 - 9:40am

Energetic eruptions leading to a peculiar hydrogen-rich explosion of a massive star

Nature 551, 7679 (2017). doi:10.1038/nature24030

Authors: Iair Arcavi, D. Andrew Howell, Daniel Kasen, Lars Bildsten, Griffin Hosseinzadeh, Curtis McCully, Zheng Chuen Wong, Sarah Rebekah Katz, Avishay Gal-Yam, Jesper Sollerman, Francesco Taddia, Giorgos Leloudas, Christoffer Fremling, Peter E. Nugent, Assaf Horesh, Kunal Mooley, Clare Rumsey, S. Bradley Cenko, Melissa L. Graham, Daniel A. Perley, Ehud Nakar, Nir J. Shaviv, Omer Bromberg, Ken J. Shen, Eran O. Ofek, Yi Cao, Xiaofeng Wang, Fang Huang, Liming Rui, Tianmeng Zhang, Wenxiong Li, Zhitong Li, Jujia Zhang, Stefano Valenti, David Guevel, Benjamin Shappee, Christopher S. Kochanek, Thomas W.-S. Holoien, Alexei V. Filippenko, Rob Fender, Anders Nyholm, Ofer Yaron, Mansi M. Kasliwal, Mark Sullivan, Nadja Blagorodnova, Richard S. Walters, Ragnhild Lunnan, Danny Khazov, Igor Andreoni, Russ R. Laher, Nick Konidaris, Przemek Wozniak & Brian Bue

Every supernova so far observed has been considered to be the terminal explosion of a star. Moreover, all supernovae with absorption lines in their spectra show those lines decreasing in velocity over time, as the ejecta expand and thin, revealing slower-moving material that was previously hidden. In addition, every supernova that exhibits the absorption lines of hydrogen has one main light-curve peak, or a plateau in luminosity, lasting approximately 100 days before declining. Here we report observations of iPTF14hls, an event that has spectra identical to a hydrogen-rich core-collapse supernova, but characteristics that differ extensively from those of known supernovae. The light curve has at least five peaks and remains bright for more than 600 days; the absorption lines show little to no decrease in velocity; and the radius of the line-forming region is more than an order of magnitude bigger than the radius of the photosphere derived from the continuum emission. These characteristics are consistent with a shell of several tens of solar masses ejected by the progenitor star at supernova-level energies a few hundred days before a terminal explosion. Another possible eruption was recorded at the same position in 1954. Multiple energetic pre-supernova eruptions are expected to occur in stars of 95 to 130 solar masses, which experience the pulsational pair instability. That model, however, does not account for the continued presence of hydrogen, or the energetics observed here. Another mechanism for the violent ejection of mass in massive stars may be required.