Redshift z value

Redshift is the name given to the change in colour of objects which are moving away from us. At normal speeds this change is so small we do not notice, but when we use powerful telescopes to look at distant galaxies the colour change is measurable.

The cause of redshift is that light is a wave, and when the source of light moves away these waves are stretched out to a longer wavelength and so change colour towards the red end of the optical spectrum. Likewise, when objects move towards us their light waves are compressed and they look bluer than stationary objects.

We observe a similar phenomenon in our everyday lives when a vehicle passes us and we hear the sound of its engine drop as its sound waves change from being compressed (higher pitch) to stretched out (lower pitch). In this case the effect is called the “Doppler shift”

Astronomers use a value called z to measure the redshift of distant objects. It is calculated as the fractional change of wavelength of the moving object relative to a stationary object. Redshifts have positive values, blueshifts have negative ones and the z value of a stationary object is zero. The larger the z number, the faster it is moving.

Evolution of Milky Way-like Galaxies

The images below show how galaxies similar in mass to our home galaxy, the Milky Way, evolved over time. The images taken by the NASA/ESA Hubble Space Telescope reveal that Milky Way-like galaxies grow larger in size and in stellar mass over billions of years. These images are part of the most comprehensive multi-observatory galaxy surveys yet. Stretching back in time more than 10 billion years, the census contains nearly 2 000 snapshots of Milky Way-like galaxies.

The images were taken between 2010 and 2012 with Hubble’s Wide Field Camera 3 and Advanced Camera for Surveys as part of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS).

For an explanation of the z values quoted below, see this Redshift article.

11.3 Billion Years Ago

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 11.3 billion years ago. Links: NASA press release A firestorm of star birth (artist’s illustration) The growth of Milky Way-like galaxies over time Hubble galaxy at redshift z = 0.26 Hubble galaxy at redshift z = 0.65 Hubble galaxy at redshift z = 1.3 Hubble galaxy at redshift z = 2.0 Hubble galaxy at redshift z = 2.4

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 11.3 billion years ago. Z=2.8

The image above reveals a compact, youthful galaxy as it looked 11.3 billion years ago, when our Universe was only about 2.5 billion years old. The bluish-white glow reveals that the fledgling galaxy is undergoing a wave of star birth, as its rich reservoir of gas compresses under gravity, creating myriad stars.

10.9 Billion Years Ago

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 10.9 billion years ago.

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 10.9 billion years ago. z=2.4

10.3 Billion Years Ago

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 10.3 billion years ago.

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 10.3 billion years ago. z=2.0

At 10.3 billion years ago, the firestorm of star birth is reaching its peak. The stellar “baby boom” churned out stars 30 times faster than the Milky Way does today. The galaxy’s yellowish colour most likely highlights ongoing star formation that is being obscured by dust and gas.

8.9 Billion Years Ago

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 8.9 billion years ago.

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 8.9 billion years ago. z=1.3

Eventually, the galaxies exhaust their star-making gas. The galaxy at 8.9 billion years ago (image above) has developed a spiral shape, and the oldest stars reside in its central region.

6.1 Billion Years Ago

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 6.1 billion years ago.

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 6.1 billion years ago. z=0.65

By 6.3 billion years ago this similar galaxy had grown even larger. The galaxy was dominated by mostly older stars, which can be seen in its reddish appearance.

3.1 Billion Years Ago

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 3.1 billion years ago.

This image, taken by the NASA/ESA Hubble Space Telescope, shows a galaxy similar in mass to the Milky Way. The galaxy is seen as it was 3.1 billion years ago. z=0.26

At 3,1 billion years ago this galaxy had clearly visible spiral arms dotted with clouds of gas lit by newly formed open star clusters.

References

NASA Composite Image

Reconstruction of 10 billion year old Milky Way

Reconstruction of Early Milky Way

In one of the most comprehensive multi-observatory galaxy surveys yet, astronomers find that galaxies like our Milky Way underwent a stellar “baby boom,” churning out stars at a prodigious rate, about 30 times faster than today.

A Firestorm of Star Birth

This illustration depicts a view of the night sky from a hypothetical planet within the youthful Milky Way galaxy 10 billion years ago. The heavens are ablaze with a firestorm of star birth. Glowing pink clouds of hydrogen gas harbor countless newborn stars, and the bluish-white hue of young star clusters litter the landscape. The star-birth rate is 30 times higher than it is in the Milky Way today. Our Sun, however, is not among these fledgling stars. The Sun will not be born for another 5 billion years.

Our Sun, however, is a late “boomer.” The Milky Way’s star-birthing frenzy peaked 10 billion years ago, but our Sun was late for the party, not forming until roughly 5 billion years ago. By that time the star formation rate in our galaxy had plunged to a trickle…

Source: Hubblesite.org

Astronomers don’t have baby pictures of our Milky Way’s formative years to trace the history of stellar growth. Instead, they compiled the story from studying galaxies similar in mass to our Milky Way, found in deep surveys of the universe. The farther into the universe astronomers look, the further back in time they are seeing, because starlight from long ago is just arriving at Earth now. From those surveys, stretching back in time more than 10 billion years, researchers assembled an album of images containing nearly 2,000 snapshots of Milky Way-like galaxies.

References

NASA News Release Nov 2015

Reconstruction Images

Evolution of galaxies similar to Milky Way

Universe has lost 90% of its galaxies

In analyzing data from deep-sky census assembled from surveys taken by NASA’s Hubble Space Telescope and other observatories, a team led by Christopher Conselice of the University of Nottingham, U.K., found that 10 times as many galaxies were packed into a given volume of space in the early universe than found today.

Most of these galaxies were relatively small and faint, with masses similar to those of the satellite galaxies surrounding the Milky Way. As they merged to form larger galaxies the population density of galaxies in space dwindled. This means that galaxies are not evenly distributed throughout the universe’s history, the research team reports in a paper to be published in The Astrophysical Journal.

Reference

http://www.nasa.gov/feature/goddard/2016/hubble-reveals-observable-universe-contains-10-times-more-galaxies-than-previously-thought

Solar System is in Orion Arm of Galaxy

The Orion Arm is a minor spiral arm of the Milky Way some 3,500 light-years (1,100 parsecs) across and approximately 10,000 light-years (3,100 parsecs) in length. The Solar System, including the Earth, lies within the Orion Arm. It is also referred to by its full name, the Orion–Cygnus Arm, as well as Local Arm, Orion Bridge, and formerly, the Local Spur and Orion Spur.

References

https://en.wikipedia.org/wiki/Orion_Arm?wprov=sfla1

 

Earth’s magnetic field maintained by Moon

The Earth’s magnetic field permanently protects us from the charged particles and radiation that originate in the Sun. This shield is produced by the geodynamo, the rapid motion of huge quantities of liquid iron alloy in the Earth’s outer core. To maintain this magnetic field until the present day, the classical model required the Earth’s core to have cooled by around 3 000 °C over the past 4.3 billion years. Now, a team of researchers from CNRS and Université Blaise Pascal, Clermont-Ferrand, France, suggests that, on the contrary, its temperature has fallen by only 300 °C. The action of the Moon, overlooked until now, is thought to have compensated for this difference and kept the geodynamo active. Their work is published on 30 march 2016 in the journal Earth and Planetary Science Letters.

More information from

http://www2.cnrs.fr/en/2735.htm

Historic First Observation of Gravitational Waves

On September 14, 2015 at 09:50:45 UTC, for the first time in history, the two detectors of the Laser Interferometer Gravitational-Wave Observatory both observed a transient gravitational-wave signal. Based on previous simulations of possible observations, the Ligo Collaboration Team was able to conclude that what their revolutionary experiment had detected was the result of two black holes merging 1 billion years ago.

Not since Galileo first turned a telescope on the night sky in 1609 have men taken such a profound step forward in observing the universe. But, whereas all telescopes since Galileo have been limited to using electromagnetic waves at one of it’s many frequencies, Ligo’s observations are based on an entirely different principal: it uses the distortions of space-time itself to make deductions about what caused these distortions. In this case, the movement and final fusion of two massive black holes.

The signal that they observed was a mere 20 millisecond blip.For the layman it might seem strange to think that the astronomers are not actually seeing anything concrete, but merely comparing a tiny observation with computer-based predictions and thereby coming to dramatic conclusions.

But this is the way that cutting-edge science works. It is exactly the same at CERN, for example, and many other physics experiments.

This is just the beginning of a revolution in astronomy. Know we know that laser interferometry really can detect gravitational waves, scientists will be pressing governments for the money to build more, bigger and more sophisticated observatories. And just as Galileo could never have predicted the discoveries to which his first observations have led us in the past 400 years, so we have no idea what incredible new things we are going to learn about the universe. But results are certainly not going to take another 400 years to arrive.

For more information see the following:

A summary of the scientific paper carrying the announcement:
http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 

A podcast of a 30 minute BBC radio program on the day the discovery was announced http://www.bbc.co.uk/programmes/b06zj4dl

A BBC news story with useful images
http://www.bbc.co.uk/news/science-environment-35524440

A Scientific American Feature on the story
http://www.scientificamerican.com/article/gravitational-waves-discovered-from-colliding-black-holes1/

A Guardian newpaper story
https://www.theguardian.com/science/2016/feb/11/gravitational-waves-discovery-hailed-as-breakthrough-of-the-century?CMP=share_btn_link

 

Astronomers say a Neptune-sized planet lurks beyond Pluto

The solar system appears to have a new ninth planet. Today, two scientists announced evidence that a body nearly the size of Neptune—but as yet unseen—orbits the sun every 15,000 years. During the solar system’s infancy 4.5 billion years ago, they say, the giant planet was knocked out of the planet-forming region near the sun. Slowed down by gas, the planet settled into a distant elliptical orbit, where it still lurks today.

Source: Astronomers say a Neptune-sized planet lurks beyond Pluto | Science | AAAS

Could There Be a Crisis in Physics?

Great Podcast on Science Friday

If you don’t know Science Friday podcasts, this is a good place to start.

Physicist Lawrence Krauss and Nobel Laureates Frank Wilczek and Brian Schmidt discuss cosmic challenges.

Episode Download Link (24 MB): http://www.podtrac.com/pts/redirect.mp3/traffic.libsyn.com/sciencefriday/scifri201401312.mp3

Show Notes: http://www.podtrac.com/pts/redirect.mp3/traffic.libsyn.com/sciencefriday/scifri201401312.mp3

Podcast Feed: Science Friday Audio Podcast (http://www.npr.org/rss/podcast.php?id=510221)

Colossal star explosion detected – BBC News

Astronomers have seen what could be the most powerful supernova ever detected. The exploding star a super-luminous supernova, was first seen 3.8 billion light-years from Earth by the All Sky Automated Survey for SuperNovae (ASAS-SN) in June 2015 and is still radiating vast amounts of energy.

At its peak, the event was 200 times more powerful than a typical supernova, making it shine with 570 billion times the brightness of our Sun. Researchers think the explosion and ongoing activity have been boosted by a very dense, highly magnetised, remnant object called a magnetar.

This object, created as the supernova got going, is probably no bigger than a major city, such as London, and is likely spinning at a fantastic rate – perhaps a thousand times a second.

Source: Colossal star explosion detected – BBC News