Archive for accreting protostars

ESO/ALMA imaging of planet formation in an Earth-like orbit

Posted in astronomy with tags , , , on April 2, 2016 by Tim Kendall
TW Hydrae: ESO/ALMA
(phys.org) ALMA‘s best image of a protoplanetary disc to date. This picture of the nearby young star TW Hydrae reveals the classic rings and gaps that signify planets are in formation in this system. Credit: S. Andrews (Harvard-Smithsonian CfA); B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO). The star TW Hydrae is a popular target of study for astronomers because of its proximity to Earth and its status as an infant (or T Tauri) star about 10 million years old. Its distance has been recently re-calculated to be as close as 38 pc. The star itself is slightly less massive than the Sun, spectral type K8IVe (as given in an excellent recent review of young stars in nearby stellar associations here). It also has a face-on orientation as seen from Earth, giving astronomers a rare view of the complete protoplanetary disc around the star.

ALMA TW Hya central regions

This is the inner region of the TW Hydrae protoplanetary disk as imaged by ALMA. The image has a resolution of 1 AU (Astronomical Unit, the distance from the Earth to the Sun in our own Solar System). This new ALMA image reveals a gap in the disk at 1 AU, suggesting that a planet with the same orbit as Earth is forming there. Credit: S. Andrews (Harvard-Smithsonian CfA); B. Saxton (NRAO/AUI/NSF); ALMA (ESO/NAOJ/NRAO). The paper “Ringed Substructure and a Gap at 1 AU in the Nearest Protoplanetary Disk”, by S.M. Andrews et al., appearing in the Astrophysical Journal Letters (pdf copy via ESO). These recent observations represent a huge breakthrough in direct imaging at the resolutions required and are very suggestive evidence for the existence of Earth-like planets in nearby interstellar space. From the abstract:
We present long-baseline Atacama Large Millimeter/submillimeter Array (ALMA) observations of the 870 μm continuum emission from the nearest gas-rich protoplanetary disk, around TW Hya, that trace millimeter-sized particles down to spatial scales as small as 1 AU (20 milliarcseconds). These data reveal a series of concentric ring-shaped substructures in the form of bright zones and narrow dark annuli (1-6 AU) with modest contrasts (5-30%). We associate these features with concentrations of solids that have had their inward radial drift slowed or stopped, presumably at local gas pressure maxima. No significant non-axisymmetric structures are detected. Some of the observed features occur near temperatures that may be associated with the condensation fronts of major volatile species, but the relatively small brightness contrasts may also be a consequence of magnetized disk evolution (the so-called zonal flows). Other features, particularly a narrow dark annulus located only 1 AU from the star, could indicate interactions between the disk and young planets. These data signal that ordered substructures on ~AU scales can be common, fundamental factors in disk evolution, and that high resolution microwave imaging can help characterize them during the epoch of planet formation.

Update on the ongoing search for the proposed “Planet Nine”, from Scientific American: The article highlights the research of Fienga et al., (2016) using the Cassini spacecraft data to pinpoint the planet. The planet is likely sub-Jovian, ten Earth masses, eccentric, e ~ 0.6, distant but not that distant, ~ 700 AU, and possibly located in the region of the sky in the direction of the southern constellation of Cetus, with true anomaly 117.8°±11°. I predict that it will be found soon, and there is as good a chance of finding it by its own internal heat, in millimeter data, as by reflected light in the visible part of the spectrum.

Young multiple system DI Chamaeleontis observed by Hubble/ACS

Posted in astronomy with tags , , on November 6, 2015 by Tim Kendall

Smoke ring for a halo

Credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt

(Phys.org) Two stars shine through the centre of a ring of cascading dust in this image taken by the NASA/ESA Hubble Space Telescope. The star system is named DI Cha, and while only two stars are apparent, it is actually a quadruple system containing two sets of binary stars. As this is a relatively young star system it is surrounded by dust. The young stars are molding the dust into a wispy wrap. The host of this alluring interaction between dust and star is the Chamaeleon I dark cloud—one of three such clouds that comprise a large star-forming region known as the Chamaeleon Complex. DI Cha’s juvenility is not remarkable within this region. In fact, the entire system is among not only the youngest but also the closest collections of newly formed stars to be found and so provides an ideal target for studies of star formation.

The Orion Nebula from Spitzer

Posted in astronomy with tags , , on May 23, 2013 by Tim Kendall

A colony of hot, young stars is stirring up the cosmic scene in this new picture from NASA's Spitzer Space Telescope.
Image credit: NASA/JPL/California Institute of Technology
Orion-constellation-map

I have looked at Orion in many recent posts. The Orion molecular cloud complex extends several degrees on the sky roughly centred on M42 and M43, shown in the main image. The complex contains many other well-known objects including M78, the Flame Nebula, and the famous Becklin-Neugebauer object, a protostar and one of the first finds of infrared astronomy, detected in 1966. The location on the sky of the three Messier objects is shown (left), as is the young O9.5V star sigma Orionis, which is associated with a young cluster known for containing planetary mass objects. The star itself is now known to be photoevaporating a nearby (1200 AU) dust cloud.