Tag Archives: ALMA

The make-up and temperature of Uranus’s rings

The rings of Uranus

New radio images taken by the ground-based telescopes by the ALMA and VLT telescopes in Chile have allowed scientists to better determine the make-up and temperature of the rings of Uranus.

The image above is from their paper. From the caption:

Images of the Uranian ring system at 3.1 mm (ALMA Band 3; 97.5 GHz), 2.1 mm (ALMA Band 4; 144 GHz), 1.3 mm (ALMA Band 6; 233 GHz), and 18.7 μm (VLT VISIR; 100 THz)…The planet itself is masked since it is very bright compared to the rings.

From the article above:

The new images taken by the Atacama Large Millimeter/submillimeter Array (ALMA) and the Very Large Telescope (VLT) allowed the team for the first time to measure the temperature of the rings: a cool 77 Kelvin, or 77 degrees above absolute zero — the boiling temperature of liquid nitrogen and equivalent to 320 degrees below zero Fahrenheit.

The observations also confirm that Uranus’s brightest and densest ring, called the epsilon ring, differs from the other known ring systems within our solar system, in particular the spectacularly beautiful rings of Saturn.

“Saturn’s mainly icy rings are broad, bright and have a range of particle sizes, from micron-sized dust in the innermost D ring, to tens of meters in size in the main rings,” said Imke de Pater, a UC Berkeley professor of astronomy. “The small end is missing in the main rings of Uranus; the brightest ring, epsilon, is composed of golf ball-sized and larger rocks.” [emphasis mine]

The mystery is why this ring has no dust, something not seen with any other ring system in the solar system, including the inner rings of Uranus itself..


ALMA detects a solar flare on Mira 420 light years away

Mira A and Mira B

The just completed ALMA (Atacama Large Millimeter/submillimeter Array), a collection of 66 antennas located in Chile, has snapped a picture of the variable star Mira with its companion star, detecting details on the primary’s surface, including evidence of a solar flare.

Mira is a star with a mass like our Sun’s, but near the end of its life having evolved into a red giant that is shedding its outer layers. Being able to track its behavior with this kind of detail will allow astronomers to better hone their theories about the life and death of stars, including our own.


ALMA captures the rotation of the large asteroid Juno

The large ground-based telescope ALMA has captured a series of images of the large asteroid Juno, allowing scientists to estimate its rotation and overall shape.

Linked together into a brief animation, these high-resolution images show the asteroid rotating through space as it shines in millimeter-wavelength light. “In contrast to optical telescopes, which capture the reflected light from the Sun, the new ALMA images show the actual millimeter-wavelength light emitted by the asteroid,” said Todd Hunter, an astronomer with the National Radio Astronomy Observatory (NRAO) in Charlottesville, Va.

…The complete ALMA observation, which includes 10 separate images, documents about 60 percent of one rotation of the asteroid. It was conducted over the course of four hours on 19 October 2014 when Juno was approximately 295 million kilometers from Earth. In these images, the asteroid’s axis of rotation is tilted away from the Earth, revealing its southern hemisphere most prominently.


The best image yet of the birth of a solar system

HL Tau

The new ground-based telescope ALMA has taken an amazing image of a baby star and the planet-forming accretion disk that surrounds it.

ALMA uncovered never-before-seen features in this system, including multiple concentric rings separated by clearly defined gaps. These structures suggest that planet formation is already well underway around this remarkably young star. “These features are almost certainly the result of young planet-like bodies that are being formed in the disk. This is surprising since HL Tau is no more than a million years old and such young stars are not expected to have large planetary bodies capable of producing the structures we see in this image,” said ALMA Deputy Director Stuartt Corder.

ALMA has just been completed and is only in its initial shake-out period. It is also not an optical telescope, but observes in longer wavelengths above infrared. Thus, it can peer through dust clouds to see details like this. And these details confirm that the most accepted theory of planetary formation appears to be right.


Astronomers today celebrate the official turning-on of ALMA, the world’s largest telescope.

Astronomers today celebrate the official turning-on of ALMA, the world’s largest telescope.

ALMA is an array of 66 dishes tuned to wavelengths in the millimeter to submillimeter range of the electromagnetic spectrum, between the infrared and radio frequencies.


The ring and planets of Formalhaut

Formalhaut ring

New observations from the new ground-based submillimeter ALMA telescope in Chile have given astronomers a clearer picture of the ring/disk of debris orbiting the nearby star Formalhaut. Moreover, the data suggests that two planets that are shepherding that ring are smaller than previously thought, no larger than a few times the size of the Earth.
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