Universe Today

When a star like our Sun reaches the end of its life – a fate we’ll face in 5 billion years – it swells up immensely, becoming a red giant star. Its size expands until it engulfs everything within the Earth’s orbit, and begins to pulsate, expending and contracting in regular intervals. Then it settles down, to live out the rest of its years as a slowly cooling white dwarf.

We’ve got 5 billion years to wait, but astronomers have found a relatively nearby star going through this very process: S Orionis, located in the constellation of Orion, and belongs to a class of Mira-type variable stars.

S Orionis pulsates with a period of 420 days. During this cycle, it changes in brightness by a factor of 500%, and changes its diameter by 20%. This ranges from 1.9 to 2.3 times the distance between the Earth and the Sun. Another way to measure this is between 400 and 500 solar radii.

During these pulsations, the star releases a tremendous amount of dust, which form into concentric rings around the star and expand outward at a speed of 10 km/s (6 miles/s). During the star’s minimum size, there’s more dust production and coronal mass ejections, and then the shell expands, releasing the material into space.

Astronomers studied S Orionis with the European Southern Observatory’s Very Large Telescope Interferometer at Paranal Observatory, Chile, using its four 8.2-metre telescopes and four 1.8-metre scopes.

Original Source: ESO News Release

After surveying more than 200 stars in various stages of formation, ESA’s XMM-Newton X-Ray Observatory has revealed a dramatically different picture than what astronomers were predicting. Specifically, the observatory helped show how streams of matter fall down onto the stars’ magnetic atmosphere, cooling the atmosphere, and absorbing X-rays.

XMM-Newton targeted new star formation in the Taurus Molecular Cloud; a vast star formation region located only 400 light-years from Earth. Many of these stars are still accumulating new material through a process called accretion. As new matter strikes the star, it heats up, blasting out ultraviolet radiation.

Astronomers expected that the infalling material would heat the stellar envelop so much that it should produce an excess of X-rays as well. But that wasn’t happening. Instead, it appears that the streams of material are so dense, they actually cool the outer atmosphere, and absorb most of the X-rays being emitted.

There should also be large quantities of dust falling into the star that should obscure it from our view, but the stars are seen burning brightly. It must be that the star’s radiation is actually vapourizing the dust before it can reach the star, giving us a clear view.

Original Source: ESA News Release

One of the brightest, closest stars to the Earth is Altair, located about 15 light-years away. For the first time, astronomers have imaged its surface, getting a better look at this bizarre neighbour.

Unlike the red giant stars that have been imaged to date, Altair is relatively tiny. It only has 1.7 times the mass of our own Sun. It rotates at an amazing speed, with its equator turning at about 300 km/s (186 miles/s), and completing a full revolution in under 10 hours. This high rate of rotation flattens the star out so that it’s 22% wider than it is tall.

These new observations were made using four of the six telescopes at a facility on Mt. Wilson, Calif., operated by the Center for High Angular Resolution Astronomy (CHARA). They have a special instrument that allows them to clean up the distortions created by the Earth’s atmosphere. By using the four telescopes together, they acted as a single instrument with 25 times the resolution of the Hubble Space Telescope.

Original Source: NSF News Release