November 7, 2016

Young Stellar System Caught in the Act of Forming Close Multiples

Young Stellar System Caught in the Act of Forming Close Multiples

For the first time, astronomers have seen a dusty disc of material around a young star fragmenting into a multiple star system. This image comprises new observations from the Atacama Large Millimeter/submillimeter Array (ALMA), Chile, and reveals the process in action!

Stars form in cosmic clouds of gas and dust, when the thin material in the clouds collapses gravitationally into denser cores that in turn draw additional material inward. The infalling material forms a rotating disc around the young star, and is slowly consumed. Eventually, the young star gathers enough mass to create the necessary temperatures and pressures at its centre to trigger nuclear fusion.

Stars that have no companion — such as the Sun — are not as common as we once thought. In fact, almost half of the stars in our galaxy have at least one companion, and some are more sociable still! Previous studies have indicated that the stars in multiple systems tend to be either relatively close to each other, within about 500 times the Earth-Sun distance (known as an Astronomical Unit or AU), or significantly further apart, at over 1000 AU.

Given these wildly different distances, scientists concluded that there were two main mechanisms producing multiple star systems — either the original cloud collapsed unstably and fragmented, each subsequent fragment crumpling to form a new star, or the rotating disc around an existing star fragmented, with the same result. Systems with larger separations likely formed via the former process (as recent observational studies have suggested), and closer-knit stellar families via the latter (although there was limited evidence of this process).

New data from ALMA have now offered observational evidence of this conclusion. This image shows the second process in action, as seen in the young triple star system L1448 IRS3B. The trio are still deeply embedded within their parent cloud in the constellation of Perseus, some 750 light-years from Earth, and are hungrily feeding from material in the surrounding disc. ALMA has revealed this disc to have a spiral structure, a feature that indicates gravitational instability.

Image Credit: ALMA (ESO/NAOJ/NRAO)/J.J. Tobin (University of Oklahoma/Leiden University)
Explanation from: https://www.eso.org/public/images/potw1644a/

Earth's Atmosphere and Sunrise over Pacific Ocean seen from the International Space Station

Earth's Atmosphere and Sunrise over Pacific Ocean seen from the International Space Station

ISS, Orbit of the Earth
August 2016

Image Credit: NASA/ESA

Aurora over Høgtuva

Aurora over Høgtuva

Høgtuva, Nordland, Norway
October 24, 2011

Image Credit & Copyright: Tommy Eliassen

November 6, 2016

Globular Cluster NGC 362

Globular Cluster NGC 362

Globular clusters offer some of the most spectacular sights in the night sky. These ornate spheres contain hundreds of thousands of stars, and reside in the outskirts of galaxies. The Milky Way contains over 150 such clusters — and the one shown in this NASA/ESA Hubble Space Telescope image, named NGC 362, is one of the more unusual ones.

As stars make their way through life they fuse elements together in their cores, creating heavier and heavier elements — known in astronomy as metals — in the process. When these stars die, they flood their surroundings with the material they have formed during their lifetimes, enriching the interstellar medium with metals. Stars that form later therefore contain higher proportions of metals than their older relatives.

By studying the different elements present within individual stars in NGC 362, astronomers discovered that the cluster boasts a surprisingly high metal content, indicating that it is younger than expected. Although most globular clusters are much older than the majority of stars in their host galaxy, NGC 362 bucks the trend, with an age lying between 10 and 11 billion years old. For reference, the age of the Milky Way is estimated to be above 13 billion years.

This image, in which you can view NGC 362’s individual stars, was taken by Hubble’s Advanced Camera for Surveys (ACS).

Image Credit: ESA/Hubble & NASA
Explanation from: https://www.spacetelescope.org/images/potw1643a/

Lenticular Cloud over Mount Cheget

Lenticular Cloud over Mount Cheget

Mount Cheget, Caucasus, Kabardino-Balkaria, Russia

Image Credit & Copyright: Dmitry Demin

Aurora over Pacific Ocean seen from the International Space Station

Aurora over Pacific Ocean seen from the International Space Station

ISS, Orbit of the Earth
September 2016

Image Credit: NASA/ESA