Spitzer Sees Crystal 'Rain' in Outer Clouds of Infant Star

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Spitzer Sees Crystal 'Rain' in Outer Clouds of Infant Star

Post by bystander » Fri May 27, 2011 1:25 am

Spitzer Sees Crystal 'Rain' in Outer Clouds of Infant Star
NASA JPL-Caltech Spitzer | 2011 May 26
Image
Stars Adorn Orion's Sword
Credit: NASA/JPL-Caltech/T. Megeath (Univ of Toledo)
Image
Cosmic Fountain of Crystal Rain
Credit: NASA/JPL-Caltech/T. Pyle (SSC)
Tiny crystals of a green mineral called olivine are falling down like rain on a burgeoning star, according to observations from NASA's Spitzer Space Telescope.

This is the first time such crystals have been observed in the dusty clouds of gas that collapse around forming stars. Astronomers are still debating how the crystals got there, but the most likely culprits are jets of gas blasting away from the embryonic star.

"You need temperatures as hot as lava to make these crystals," said Tom Megeath of the University of Toledo in Ohio. He is the principal investigator of the research and the second author of a new study appearing in Astrophysical Journal Letters. "We propose that the crystals were cooked up near the surface of the forming star, then carried up into the surrounding cloud where temperatures are much colder, and ultimately fell down again like glitter."

Spitzer's infrared detectors spotted the crystal rain around a distant, sun-like embryonic star, or protostar, referred to as HOPS-68, in the constellation Orion.

The crystals are in the form of forsterite. They belong to the olivine family of silicate minerals and can be found everywhere from a periodot gemstone to the green sand beaches of Hawaii to remote galaxies. NASA's Stardust and Deep Impact missions both detected the crystals in their close-up studies of comets.

"If you could somehow transport yourself inside this protostar's collapsing gas cloud, it would be very dark," said Charles Poteet, lead author of the new study, also from the University of Toledo. "But the tiny crystals might catch whatever light is present, resulting in a green sparkle against a black, dusty backdrop."
Forsterite crystals were spotted before in the swirling, planet-forming disks that surround young stars. The discovery of the crystals in the outer collapsing cloud of a proto-star is surprising because of the cloud's colder temperatures, about minus 280 degrees Fahrenheit (minus 170 degrees Celsius). This led the team of astronomers to speculate the jets may in fact be transporting the cooked-up crystals to the chilly outer cloud.

The findings might also explain why comets, which form in the frigid outskirts of our solar system, contain the same type of crystals. Comets are born in regions where water is frozen, much colder than the searing temperatures needed to form the crystals, approximately 1,300 degrees Fahrenheit (700 degrees Celsius). The leading theory on how comets acquired the crystals is that materials in our young solar system mingled together in a planet-forming disk. In this scenario, materials that formed near the sun, such as the crystals, eventually migrated out to the outer, cooler regions of the solar system.

Poteet and his colleagues say this scenario could still be true but speculate that jets might have lifted crystals into the collapsing cloud of gas surrounding our early sun before raining onto the outer regions of our forming solar system. Eventually, the crystals would have been frozen into comets.

The Herschel Space Observatory, a European Space Agency-led mission with important NASA contributions, also participated in the study by characterizing the forming star.

"Infrared telescopes such as Spitzer and now Herschel are providing an exciting picture of how all the ingredients of the cosmic stew that makes planetary systems are blended together," said Bill Danchi, senior astrophysicist and program scientist at NASA Headquarters in Washington.

The Spitzer observations were made before it used up its liquid coolant in May 2009 and began its warm mission.
A Spitzer Infrared Spectrograph Detection of Crystalline Silicates in a Protostellar Envelope - CA Poteet et al
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SAO: Measuring the Clumpiness of Proto-Planetary Disks

Post by bystander » Sat Jul 16, 2011 4:52 pm

Measuring the Clumpiness of Proto-Planetary Disks
Smithsonian Astrophysical Observatory
Weekly Science Update | 2011 May 27
The process of star formation, once thought to involve just the simple coalescence of material under the influence of gravity, actually entails a complex series of stages, with the youngest stars assembling circumstellar disks of material (possibly preplanetary in nature) for example. Understanding these early stages has been difficult for astronomers, in part because because they take place in nurseries heavily obscured by dust. Nevertheless, they are critically important to an understanding of how our young solar system and its planets were born and evolved.

The Spitzer Space Telescope and its IRAC infrared camera have enabled astronomers during the past few years to discover and study large numbers young stellar objects ("YSOs") in star forming clouds of gas and dust. Its sensitive infrared images can penetrate most of the dusty veil and pinpoint the many faint stars, cool and red, that are between about one and ten million years old, or sometimes younger.

In a new study of the time variability of YSOs, CfA astronomers Joe Hora and Jan Forbrich, together with a large team of collaborators, used IRAC to conduct a timed series of observations (81 snapshots over 40 days) of YSOs in the Orion nebula. They discovered that 70% of the YSOs thought to have disks around them vary in time, with variations that fall roughly into four categories: periodic, flaring, irregular, and narrow flux dips. These latter cases, called "dippers," are suspected of being caused by clumps of dust in the circumstellar disk that happen to pass across the line-of-sight to the star as the disk rotates; they may also be due to a warp in the rotating disk that crosses the line-of-sight. With additional observations, including some from ground-based telescopes, the scientists plan to confirm and model the nature of these clumps, as well as to explain more specifically each of the other types of variability on a case-by-case basis.
Ysovar: The First Sensitive, Wide-area, Mid-infrared Photometric Monitoring of the Orion Nebula Cluster - M Morales-Calderón et al << Previous Science Update
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor