The Young Astronomers
From the monthly archives: April 2012
A nebula is a cloud of dust and gas found within the interstellar medium filling the great voids between the stars within galaxies and star clusters.
The different types of nebula consist of different elements in different proportions. Most nebulae that have not been formed by the destruction of dying stars (i.e. SNR (several types -Ia and II – will be described at a later date), planetary nebulae and those generated by Wolf-Rayet stars), contain large amounts of hydrogen gas. These nebulae if given the right conditions to compress and heat up will form the next generation of stars.
One such star forming nebula - The Eagle Nebula Credit NASA, ESA; HST
All stars, whether they are hypergiants or red dwarfs began their lives as a nebula and rather fittingly as a star dies it returns its material to the cosmos as another nebula. This nebula is either a planetary nebula or a supernova remnant, and it is through this release of matter that the universe is provided with all the elements heavier than hydrogen and helium. This includes all the material that forms the Earth and everything on it, including humans. The oxygen we breathe was formed in the hearts of red giants and the iron in our bloodstream was produced in the final days of a massive star’s existence, right before it ripped itself to pieces as a supernova. It is from this that we get the saying that we are all made of star dust, we quite literally are!
The Helix Planetary Nebula Credit NASA, ESA; HST Perhaps one day a new star will for from the ashes of the star that produced this lovely sight.
As each generation of stars further enriches the universe by spreading their life’s work as a nebula, the following generation of stars contain more of the heavier elements as there is now more available thanks to the previous generation synthesising (producing) them from hydrogen and helium over the course of their lives. Meaning that each successive stellar generation contains a larger quantity of ‘metals’ – in astrophysics a metal is any element other than hydrogen and helium – this allows different populations of stars to be identified based on their metal content. This variation is due to each successive generation of star forming nebulae contain more and more dust and metals hence creating the different detectable differences in the spectra of the stars they produce.
There are three main populations of stars though I shall keep a description of each for a further post more focused on the topic.
There are several very different types of nebulae but these types will be discussed in depth in further posts.
Space telescopes usually thought of as huge machines. The famous Hubble Space Telescope, for example, is 13.2 meters (43.5 ft) long and 4.2 meters (14 ft) in diameter. Though not all are so large; 800 kilometers above the Earth there is a satellite that is just 65 centimeters (about 25 inches) long – not larger than a large suitcase – proving that, when it comes to science, “size doesn’t matter”.
This astonishing device is called MOST (which stands for Microvariability and Oscillations of Stars). Although being very small compared to its peers, this satellite is helping scientists answer intriguing questions about stars, planets and even the Universe itself.
The MOST Space Telescope Credit: Canadian Space Agency
Staring at the Stars
Launched on June 30th 2003, MOST is the first space telescope to be entirely designed and built in Canada. As its name suggests, it is designed to take precise measurements of variations in intensity (the brightness) of stars in order to determinate their composition and age. The larger space telescopes cannot afford the time required for this task as to measure these oscillations, is necessary to keep the lens pointed at a single target in the sky for weeks at a time, and they can’t do so because of the high demand for their time.
Usually, astronomers use expensive ground-based telescopes to measure these stellar pulsations. However, this isn’t the best way to do so, since the readings are distorted by the Earth’s atmosphere. Moreover, the day-night cycle makes impossible to scientists to observe a star for 24 hours a day. Though with its orbit above the Earth’s atmosphere MOST can avoid both problems; and is able to look at any part of the sky continuously for up to seven weeks with a minimum of distortion.
The Secret life of Stars
The technology of this incredible telescope is helping astronomers figure out some very interesting things about stars, things well beyond our expectations. One of these discoveries was made as soon as the satellite became operational.
In 2004, the MOST team reported that Procyon (the brightest star in the constellation Canis Minor) shows no pulsations at all, contradicting more than 20 years of observations. Later, in 2006, the scientists realized that they were dealing with an unknown class of stars, the “slowly pulsating B supergiants”.
Furthermore, MOST has also been used to study exoplanets in alien star systems. Indeed, this is the only telescope – in space and on Earth – able to detect the light reflected by a planet orbiting around another star. Although not designed for this purpose, MOST is giving us a hint of what the atmosphere of those planets look like. It does this by detecting subtle variations in the light from either the planet or the star itself. MOST can see changes down to levels of one part to a million – or one ten thousandth of a percent!
“MOST has been very good at seeing things in the Universe that most people never expected or thought possible,” says Jaymie Matthews.
This post is part of the Young Astronomers’ Databank Project
Hubble has for the first time spotted Aurorae on the distant ice giant Uranus. In the image below you can see the turquoise disk of the planet has a bright ‘blotch’.
Uranus' Aurorae Credit:NASA, ESA, and L. Lamy
An aurora is produced when a stream of charged particles from the solar wind (the material ejected from the Sun) collides with a planet’s magnetic field (more properly called its magnetosphere) and excites the particles within the atmosphere casing them to glow. This glow is what we observe as the aurora.
On Earth aurorae with a blue or red colour are due to excited nitrogen, whilst green or a redish brown hue is due to excited oxygen. The aurorae can dance across the sky in waves of coloured light and whilst some last for a few brief minutes others can remain active for hours depending on the conditions creating them – solar storms for example can create very powerful aurorae.
Aurorae have been observed on other planets as well, particularly Jupiter and Saturn; both of which have prominent auroral systems. Those present in Uranus’ atmosphere are considerably fainter and appear to last only for a few short minutes at a time.
These images represent the first observation of Uranus aurorae, with previous data collected directly during the Voyager 2 flyby in 1986.
These new observations should help to reveal more about Uranus’ magnetic field, which we currently know little about.
You can read more here
Last week saw the launch of a new science project on twitter:
The project is hoping to collect as many science based definitions, explanations and facts all in the form of tweets which contain no more than 140 characters.
No small feat!
The project is looking for as many people to contribute as possible on all topics of science right through from Astrophysics to Zoology. Best of all anyone can take part regardless of age or experience.
What is the goal of this project you ask?
We aim to collect these definitions, explanations and biographies over the next three months in the hopes of collating them in to a book – the proceeds of which will go to charity. Details of the charity / charities will be released in the coming weeks.
Fun education from all, for all and helping out a good cause to boot, what could be better!
You can learn more about the project on the official website and on twitter by following @science140
Submitting a tweet for the project is easy, just include the hash tag – #science140
So what are you waiting for! Dust off your facts and get tweeting!
In celebration of the Hubble Space Telescope’s 22nd anniversary the ESA has released this truly stunning image of the star forming region 30 Doradus.
30 Doradus Credit: NASA, ESA, ESO, D. Lennon and E. Sabbi (ESA/STScI), J. Anderson, S. E. de Mink, R. van der Marel, T. Sohn, and N. Walborn (STScI), N. Bastian (Excellence Cluster, Munich), L. Bedin (INAF, Padua), E. Bressert (ESO), P. Crowther (Sheffield), A. de Koter (Amsterdam), C. Evans (UKATC/STFC, Edinburgh), A. Herrero (IAC, Tenerife), N. Langer (AifA, Bonn), I. Platais (JHU) and H. Sana (Amsterdam)
30 Doradus is better known as the Tarantula nebula and is located 170,000 light years away within the Milky Way’s largest satellite galaxy the Large Magellanic Cloud (LMC).
The image shows a region of space approximately 650 light years across with several million stars present within. Combined, the sum total of the stars’ masses shown in this image would be well over a million times the mass of our own Sun.
The stars are grouped into smaller clusters ranging in age from about 2 million – 25 million years old, whilst this may sound ancient in human terms as far as the universe is concerned even the oldest star in the region is a newcommer.
The brightest cluster is NGC 2070 being one of the youngest (between 2 and 3 million years old) and most actively starforming regions with the larger structure Astronomers find it an attractive region to study. Recently in fact, it was revealed that at the heart of the cluster (which contains upwards of half a million stars) there is a dense clump of stars designated RMC 136 where the largest stars yet discovered reside. Indeed several of these monsters are more than 100 times the mass of our own sun, truly cosmic giants.
The fierce output of the regions hot stars sculpts the regions gas and just into the fantastic arcs and bubbles we can see in the image. The fierce radiation bombardment of radiation is also exciting the gas and dust molecules of the nebula making them glow in their own right and classing the region as an emission nebula.
The image is composed of data from both Hubble and the ESO’s MPG/ESO 2.2-metre telescope and represents the one of the largest such mosaics in existence today. The data was captured by both telescopes during an observing run in October 2011.
You can read more here.
AAPOD
Portal to the Universe
