Archive for the ‘Astronomy’ Category

SKA Split decision – the best solution!

The selection of the best site for the Square Kilometre Array (SKA), which was between South Africa and a joint Australian/New Zealand bid, surprised most people. But it makes real sense to utilize the preliminary facilities that both nations have started to contribute.

In an earlier article on RelativeCosmos.com I suggested Australia would be best but in light of the split decision, it is a welcome selection!

Australia will launch phase 1 of the plan and get started sooner and South Africa will come in a little later with phase 2. It really is a workable solution and it is coup for both countries’ astronomy communities – many details are yet to be finalised but it’s one of those great times where a turning point makes for great history.

To quote Nature, “But splitting the site does have potential benefits. For one thing, the redundancy created by international collaboration can come in handy. The ISS, for example, continues to be serviced by a slew of vehicles from its different partners, even though the US space shuttle no longer flies there. There is also a perverse financial advantage — multiple partners are less likely to cancel an over-budget project than is a single government. But the greatest benefit is human: a more complex project draws in more people from more places and gives them an opportunity to participate.”

Read more on:  Nature  485, 548 (31 May 2012) doi:10.1038/485548a

Square Kilometre Array (SKA) may go to South Africa but is it really the best site?

By Estelle Asmodelle

SKA Image courtesy: Paul Bourke and Jonathan Knispel and supported by WASP (UWA), iVEC, ICRAR, and CSIRO

Recent reports on the selection of the site for the Square Kilometre Array (SKA) have suggested that South Africa offers the best site and a panel of advisors recommended the SA site over Australia. The argument was put that the SA site was cheaper for construction, yet Australia had lower insurance fees, and primarily that the SA site was at a higher altitude.

The issue of altitude is really irrelevant here for at higher frequencies water vapour, or Scintillation (the distortion of waves moving through varying densities) can become a problem, but not so much for long radio waves, the bigger problem there is  radio frequency interference. Australia would be the best place for SKA, especially in WA which is ‘radio quite,’ not so in South Africa. Most long wave radio dishes are low lying. Altitude is more important for millimetre or sub-millimetre arrays.

I think this is really a political issue, South Africa really needs help financially and the SKA would boost their economy. I just hope that Australia is chosen, for South Africa’s site is not as remote and within 10 years, of completion, the site could suffer considerable radio interference problems, which would seriously degrade its operational status.

And also South Africa has many other issues, such as social unrest which could affect the operation of the telescope, or the employees. The argument that SA would be best as they have already started building the array, but it’s also true of Australia, who under the project name ASKAP, or the Australian Square Kilometre Array Pathfinder have already deployed some of the planned 36 dishes which will be complete in 2013, and can be integrated into the SKA if Australia is chosen, some dishes have already seen first light. See the site:

ASKAP, or the Australian Square Kilometre Array Pathfinder

http://www.atnf.csiro.au/projects/askap/index.html

See the status of the ASKAP site here in real time – updated often:

http://www.atnf.csiro.au/projects/askap/askap-live/

Don’t take my word for it – see Brian Boyle’s burb on the advantages Australia offers for the SKA:

http://www.ska.gov.au/Pages/BrianBoyle’s2012SKAUpdate.aspx

Some say that people who are astronomers, or students like me who will be looking for placement soon, are just feathering their nest – not true, for most of the people who will work on these sites will be from all over the world, the very cream of the crop, and probably not be Australian to a large extent.

So in fact we are further along than SA. So why the support for SA – word is, as I’ve eluded too, it’s really about politics not science – see this article:

http://www.gizmodo.com.au/2012/02/ska-bid-should-come-down-to-science-not-politics/

The last thing to bear in mind – Australia will soon have the NBN rolled out all over the country – this will assist the data handling to a very large extent – certainly by the time the SKA is complete we will have one of the best broadband networks in the world!

Interestingly the last big astronomy project SA was involved in had endless imaging problems (Although an optical site), and still does to an extent, and even more recently, poor broadband and operating problems:

http://www.salt.ac.za/

And read more here:

http://www.southafrica.info/about/science/salt-telescope.htm

All in all the remote WA site is best suited for such an astronomical site for several reasons but most importantly the size of our site  – see the map for details:

Potential SKA array station placement in Australia and New Zealand overlaid on a population density map. Major broadband network links (existing and planned) are also shown. Credit: CSIRO

 

 

 

 

 

 

 

THE TRANSIT OF VENUS and also the TOTAL SOLAR ECLIPSE.

By Estelle Asmodelle

The transit of Venus is happening 5th-6th June 2012.

There are plenty of Astronomical Societies who are holding ‘transit parties,’ including two that I do presentations to: The first one, here is a page from the Newcastle Astronomical Society with their ‘transit party’ and they had ABC radio there as well:

http://www.nas.org.au/HTML%20Pages/venus_transit_event_2004.htm

I understand they will be doing the same thing this year… and I will be going as well.

The second is the Sutherland Astronomical Society (largest such group in Sydney) – they have their own observatory, and it’s a good one too. They too are going to have a ‘transit party’

http://www.sasi.net.au/index.php

Incidentally, I am giving  a presentation to this group (in response to an invite from them after reading some of my articles in Cosmos) entitled: “Cosmology and the role of the General Theory of Relativity.” Which will be 2 nights after the transit – this will be the first time that I’ve given a presentation to this group, and I feel a bit intimidated by it as it’s a 90 minute presentation and they usually get university lecturers to do such presentations – fingers crossed that I have my ducks all in a row…

I didn’t see the 2004 transit as I was overseas at the time but I won’t miss this one! Here is an Australian site dedicated to the transit that you may find interesting as well:

http://www.transitofvenus.com.au/HOME.html

Incidentally, Jeremiah Horrocks was the first person to successfully predict and observe the transit of Venus in 1639.

But the BIG news is really the total solar eclipse in Cairns, which is at the top of Queensland, that is the big news. Cairns is 3 hour flight and 2 hour drive from my home but we have our flight booked and our hotel booked ready – I am taking my two nephews as well, one is at Uni and the other is very interested in astronomy as well. Here in Australia its big news for many people and most of Cairns is booked out – I will taking my telescope and HD video camera, together with a suitable filter, to film the event – so it’s really exciting – it’s my first total eclipse. I have seen a couple of partials but never a total! Here is an Australian website with some more details:

http://www.eclipsecairns.com/

By November it should be dry, also Cairns gets tropical rain and as the eclipse is just after sunrise it will 95% be dry, I just hope it’s clear skies!

Water on the Moon

By Estelle Asmodelle

Last December I joined the Newcastle Astronomical Society [NAS: http://www.nas.org.au/ ], that’s in Newcastle here in NSW, Australia – not the UK. When they had learned that I write the Space | Astronomy | Cosmology news for Cosmo magazine (sometimes) they invited me to give a series of talks – which I was surprised about as they usually have academics delivering such presentations, but agreed nervously. Still nervous about it :-)

Anyway, then came the problem about what to talk about – as there is so much but being an Astronomical society they aren’t interested in mathematical or highly technical presentations, and so I borrowed some work from this course for the 1st presentation:

I wrote my Essay about Moon discoveries, the title being: “Moon Discoveries & The Presence of Water” It’s a very interesting subject, and there has been many more tests and detections of water, in some form, on the Moon than most realise – so I decided to turn this essay, into a 1 hour presentation, it had to be expanded somewhat, with more photos etc., but it should go well.

The title of the talk is “Water on the Moon,” and is to at University of Newcastle, 3rd February – would invite any who are interested but it’s a bit far to travel – check out the link:

http://www.nas.org.au/HTML%20Pages/NAS%20Meetings.htm

Is the universe expanding asymmetrically?

Monday, 26 September 2011
by Estelle Asmodelle
Is the universe expanding asymmetrically? This image shows the two hemispheres of a spherical mapping of the cosmic microwave background. New research examining the velocities of Type Ia supernovae suggests faster expansion in the northern hemisphere of the universe, challenging the cosmological principle that the universe is expanding uniformly in all directions.

Credit: WMAP/NASA

GOSFORD: Recent examination of supernovae velocities suggests the universe may be expanding non-uniformly in its acceleration, which implies the laws of physics may vary throughout the cosmos.

Physicists working with the Supernova Cosmology Project’s Union2 data set have suggested that the expansion of the universe seems to display a preferred axis, meaning that the universe is expanding faster in one direction than any other.

See here for the full article.

Sun puts relativity to the test

Sep 13, 2011

Alternatives to Einstein’s general theory of relativity can be investigated by studying the Sun. That is the claim of a group of physicists in Portugal who have found that a variation of a theory put forward nearly a century ago by Arthur Eddington is constrained but not ruled out by observations of solar neutrinos and solar acoustic waves.

General relativity, which describes gravity as the curvature of space–time by massive objects, has so far passed every experimental and observational test dreamed up by physicists. But the theory does present a number of problems. In addition to the difficulty of unifying it with quantum mechanics and the challenge to explain the nature of dark matter and dark energy, there remains the conceptual problem of singularities, where the laws of physics break down.

Since Einstein introduced general relativity in 1916, many alternatives have been proposed. Last year Máximo Bañados of the Pontifical Catholic University in Chile and Pedro Ferreira of Oxford University reported a variant of a theory originally put forward by the British astrophysicist Arthur Eddington that adds a repulsive gravitational term to general relativity. This has the virtue of not requiring singularities, and as a result does not predict that the universe originated from a Big Bang, nor does it imply the formation of black holes.

Looking inside a star

When considering a gravitational field within a vacuum, this Eddington-inspired theory is equivalent to general relativity but predicts different effects for gravity acting within matter. The ideal place to look for such differences would be inside neutron stars – but the interiors of neutron stars are not understood sufficiently to compare the theories.

The answer, say Jordi Casanellas and colleagues at the Technical University of Lisbon, is to use the Sun. While a much less extreme source of gravity than a neutron star, the inner workings of the Sun are described accurately by solar models. Casanellas’s group has calculated that even in its non-relativistic Newtonian form, the Eddington-inspired theory should predict measurable differences in solar output compared with standard gravitational theory.

The Lisbon researchers have shown that the presence of the repulsive gravity term in the theory of Bañados and Ferreira is similar to setting a different value for the gravitational constant inside matter. And with the strength of gravity higher or lower than it would otherwise be inside the Sun, the inner solar temperature is also modified because the Sun is assumed to be in hydrostatic equilibrium. This means that the inward pressure of its mass is balanced by the outward thermal pressure generated by the fusion reactions within it. A higher temperature implies a greater rate of fusion burning, which in turn implies higher emission rates of solar neutrinos.

Altering acoustic waves

Similarly, a different strength of gravity inside the Sun implies a variation in its density distribution, which should modify the propagation of acoustic waves measured using the techniques of helioseismology.

Casanellas and co-workers have shown that observations made by neutrino telescopes of the solar neutrino flux coming from the proton–proton chain reaction that produces boron-8 significantly constrain the correction to general relativity, calculating an upper limit to the effective gravitational constant. Combined with a lower limit obtained from helioseismic data, the researchers are able to put a significant constraint on the Eddington-inspired theory. However, they point out that their calculations do not rule out such a theory.

The researchers say that improving on these upper and lower limits will be difficult because of uncertainties in a few of the parameters within solar models, such as the abundance of helium on the solar surface. As such, more sensitive measurements of neutrino fluxes are unlikely to have much of an impact. But they believe their approach could be used to constrain other alternative theories of gravity.

Further testing on Earth

Ultimately, adds team member Paolo Pani, such theories could be tested experimentally by measuring, for example, the gravitational attraction between a metal ball inserted into a hole in the ground and the mass of the Earth surrounding it. The idea would be to make the hole just big enough for the ball to fit and no more, so that what is measured is the strength of gravity through matter and not the surrounding void (in this case air). However, Pani points out that doing so would be a considerable experimental challenge.

Clifford Will of Washington University in St Louis, US, described the latest work as a “nice example of using the Sun as a laboratory for probing fundamental physics” but added that “it’s not yet clear whether the bounds proposed by this paper present serious threats to alternative gravity theories”.

The research is reported at arXiv:1109.0249.

About the author

Edwin Cartlidge is a science writer based in Rome

Dark matter signals detected?

Thursday, 15 September 2011
by Estelle Asmodelle

CRESST Detector

This image shows the CRESST experiment. The detectors are supercooled to a temperature only slightly above absolute zero.

Credit: Credit: CRESST & The Max-Planck-Institut für Physik.

GOSFORD: Physicists have detected signals that could be interpreted as dark matter, the elusive substance believed to comprise 80% of matter in the Universe, and say it could have a lower mass than suspected.

Researchers working on the Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) experiment in Italy, have announced they have detected weakly interacting particles that may be evidence for the elusive substance, only known because of the gravitational pull it exerts on ‘normal’ (baryonic) matter.

Read the full article here:

The Milky Way is a galactic cannibal

Monday, 18 July 2011
by Estelle Asmodelle
galaxy (NGC1300) An image of a barred-spiral galaxy (NGC1300) where you can clearly see the bar structure in the thin disk of the galaxy (the line through the middle of the galaxy which the spiral arms start from). The Milky Way is thought to have a bar like this in its thin disk, as well as a similar shape in the thick disk as predicted by Dr Bekki’s simulation.Credit: NASA, ESA, and The Hubble Heritage Team STScI/AURA

http://www.cosmosmagazine.com/news/4528/the-milky-way-a-galactic-cannibal

PERTH: A merger between the infant Milky Way and a smaller galaxy has been detected with the help of a new theoretical model, providing evidence that our galaxy is a barred-spiral galaxy.

The new model simulates a merger between a smaller galaxy and the Milky Way some nine billion years ago and shed light on how the Milky Way was formed, reveals its history of devouring smaller galaxies and may strongly support a new model of the galaxy formation.

Threat of James Webb Space Telescope Cancellation

As NASA prepares to wrap up its shuttle program, leaving open questions about what comes next for U.S. human spaceflight, the next big thing in NASA’s astronomy program has been dealt a blow. The James Webb Space Telescope, a tennis court–size spacecraft that would take up a position in deep space to peer farther than ever into the cosmos, has been in development as a replacement for and successor to the Hubble Space Telescope, which has already logged 21 years in orbit. But the House Appropriations Committee, in a bill announced July 6, proposed axing the project entirely this week, citing mismanagement and bad budgeting.

http://www.scientificamerican.com/blog/post.cfm?id=threat-of-james-webb-space-telescop-2011-07-07&WT.mc_id=SA_WR_20110714

Neptune’s day measured to the second

by Estelle Asmodelle

NeptuneThe colours in this image were modified to emphasize the planet’s atmospheric features. Neptune’s Great Dark Spot stands out as the most prominent feature on the left. The two key features Karkoschka used can also be seen: the fainter Dark Spot 2 and the South Polar Feature, which are locked to the planet’s rotation.Credit: Erich Karkoschka

This finding adds to our knowledge of the fundamental properties of Neptune and also provides a mechanism for understanding how Neptune’s mass is distributed. The study could lead to a better understanding of the giant gas planets in general.

http://www.cosmosmagazine.com/news/4474/neptunes-day-measured