pulsating star

I remember the night
You went away, darkness
Descended, it became my
Friend. I dreamt of glittering
Cities where you might walk,
I pictured night trains racing
Through the cold, distance
Threatening love, stifling
Hearts. I peered up at the
Flickering stars, galaxies
Pulsating, drifting like spirits
Through time, with age, I’ve
Discovered grace, as I awake
To the chill, it keeps my bones
Warm, keeps my heart beating
To the rhythm, of restlessness

Star pulsating gas cloud (this is an artist depiction of a real phenomenon: while stars with periodic variable activity like this exist, to see this pattern you would need to live a very, very long time and experience time in a very different way)

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RS Puppis

Over a period of five weeks the NASA/ESA Hubble Space Telescope has observed the variable star RS Puppis growing brighter and dimmer as it pulsates.

This is known as a light echo, where light appears to reverberate through the murky environment around the star.

A star is pretty stable for most of its life, shining brightly by slowly consuming the fuel at its core.

However, some stars evolve into very different beasts once most of the hydrogen that stars use as fuel has been consumed.

They become pulsating stars - unstable, expanding and shrinking over a number of days or weeks and growing brighter and dimmer as they do so.

RS Puppis is a type of variable star known as a Cepheid variable, which naturally have comparatively long periods. This one varies in brightness by almost a factor of five every 40 or so days.

RS Puppis is unusual as it is shrouded by a nebula.

Hubble captured this photo in 2010, but back in 2008, astronomers used the light echo around RS Puppis to measure its distance from us, obtaining the most accurate measurement of a Cepheid’s distance.

The universe is expanding even faster than expected

Astronomers using NASA’s Hubble Space Telescope have discovered that the universe is expanding 5 percent to 9 percent faster than expected.

“This surprising finding may be an important clue to understanding those mysterious parts of the universe that make up 95 percent of everything and don’t emit light, such as dark energy, dark matter, and dark radiation,” said study leader and Nobel Laureate Adam Riess of the Space Telescope Science Institute and The Johns Hopkins University, both in Baltimore, Maryland.

The results will appear in an upcoming issue of The Astrophysical Journal.

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A GIANT STELLAR VOID IN THE MILKY WAY

A major revision is required in our understanding of our Milky Way Galaxy according to an international team led by Prof. Noriyuki Matsunaga of the University of Tokyo. The Japanese, South African and Italian astronomers find that there is a huge region around the centre of our own galaxy which is devoid of young stars. The team publish their work in a paper in Monthly Notices of the Royal Astronomical Society.

The Milky Way is a spiral galaxy containing many billions of stars, with our Sun about 26,000 light-years from its centre. Measuring the distribution of these stars is crucial to our understanding of how our galaxy formed and evolved. Pulsating stars called Cepheids are ideal for this. They are much younger (between 10 and 300 million years old) than our Sun (4.6 billion years old) and they pulsate in brightness in a regular cycle. The length of this cycle is related to the luminosity of the Cepheid, so if astronomers monitor them they can establish how bright the star really is, compare it with what we see from Earth, and work out its distance.

Despite this, finding Cepheids in the inner Milky Way is difficult, as the galaxy is full of interstellar dust which blocks out light and hides many stars from view. Matsunaga’s team compensated for this, with an analysis of near-infrared observations made with a Japanese-South African telescope located at Sutherland, South Africa. To their surprise they found hardly any Cepheids in a huge region stretching for thousands of light-years from the core of the galaxy.

Noriyuki Matsunaga explains: “We already found some time ago that there are Cepheids in the central heart of our Milky Way (in a region about 150 light-years in radius). Now we find that outside this there is a huge Cepheid desert extending out to 8,000 light-years from the centre.”

This suggests that a large part of our galaxy, called the extreme inner disk, has no young stars. Co-author Michael Feast notes: “Our conclusions are contrary to other recent work, but in line with the work of radio astronomers who see no new stars being born in this desert.”

Another author, Giuseppe Bono, points out: “The current results indicate that there has been no significant star formation in this large region over hundreds of millions years. The movement and the chemical composition of the new Cepheids are helping us to better understand the formation and evolution of the Milky Way.”

Cepheids have more typically been used to measure the distances of objects in the distant universe, and the new work is an example instead of the same technique revealing the structure of our own Milky Way.

IMAGE….An artist’s impression of the implied distribution of young stars, represented here by Cepheids shown as blue stars plotted on the background of a drawing of the Milky Way. With the exception of a small clump in the Galactic centre, the central 8000 light years appear to have very few Cepheids, and hence very few young stars. Credit: The University of Tokyo. Click for a full size image