Tag Archives: Astronomy

Probing the Universe with the Square Kilometre Array

Scientists from South Africa are playing a leading role in developing the science which will be done with the world’s largest telescope, the Square Kilometre Array.

The SKA telescope, to be built in Australia and South Africa, will allow scientists to look far back into the history of the universe and will give much more detail than before on how the universe has evolved over 14 thousand million years. More information will be obtained on how stars, galaxies and clusters of galaxies formed and how they have changed since the Universe was young. This will allow for the plotting of a 3D map of the Universe.

The international SKA Organisation, which includes eleven countries, is bringing up to date the science case for the telescope. South African scientists are playing a leading role in many of the working groups. The SKA Cosmology Working Group is chaired by Roy Maartens, SKA Research Professor at the University of the Western Cape (UWC). Professor Maartens and Professor Mario Santos, also a Research Professor at UWC, with astronomers from South Africa and the other SKA member countries, have played a leading role in setting out the SKA science.

Roy Maartens says: “Researchers here have devised a means of using the world’s largest telescope in new ways that will help shape the future of cosmology.”

Mario Santos says: “Usually a map of the Universe is made using galaxies as tiny beacons of the large scale structure of the Universe. This is quite demanding as it requires the mapping of large numbers of galaxies across the sky.”

“The survey we are proposing will measure the emitted radiation from all the hydrogen atoms spread across the Universe without actually detecting galaxies. This will make it easier to survey all of the sky across cosmic times, allowing the phase 1 of the SKA to become an extremely competitive cosmology machine,” he adds.

“By making these huge, 3D maps of the Universe we will be able to test the limits of General Relativity and maybe find some signature of new physics on these large scales which can shed light on the true nature of dark energy. Moreover, we can also look for imprints of what happened at the very beginning of the Universe,” added Santos.

An experiment like this, says Santos, using intensity mapping, has never been done before. The largest 3D maps of the large scale structure of the Universe have been done using optical telescopes. The current project will be about 50 times larger. Other future experiments, such as the Euclid satellite, will be able to also probe a large fraction of the Universe, but none will match the SKA in terms of size and depth.

Maartens adds: “It will be like making a movie of the Universe from a young age, when it was only about 2 billion years old, until today when it is about 14 billion years old. The movie will be low resolution but enough to test the fundamentals of cosmology.”

When the actual survey with the SKA comes online, a large team will be required to deal with it. Once the phase 1 of the SKA is built, around 2023, it will take about 2 years to complete the survey.

SKA SA has been crucial in promoting the build up of the required researchers to lead such an effort. However, says Santos, they don’t have to wait for the SKA to start, before doing observations. “Tests are already being conducted using the KAT7 system with the full support of the KAT7 staff and we plan to start tests with MeerKAT in just a year, during the early science phase,” Santos stated.

He added that the SKA telescope is like a “physics lab”, allowing many different experiments to be pursued. There will be other surveys that in combination with this one, will allow scientists to push the limits of our current knowledge of the Universe.

Reference information

Astronomers preparing to map the Universe with largest radio telescope ever built

SKA Website

100,000 Stars – 3D Interactive Visualization

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Optical View

100,000 Stars is an interactive visualization of the stellar neighborhood created for the Google Chrome web browser. It shows the location of 119,617 nearby stars derived from multiple sources, including the 1989 Hipparcos mission. Zooming in reveals 87 individually identified stars and our solar system. The galaxy view is an artist’s rendition based on NGC 1232, a spiral galaxy like the Milky Way.

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Thermal View

It is an incredible 3-D Visualization that will keep you rooted in from of your screen all day if you are not careful!

We suggest taking the automated tour on your first visit. Kudos and thank you to all involved in this amazing project, we hope you keep it going!

VISIT THE 100,000 Stars Experiment at stars.chromeexperiments.com/

(from their site)
Warning: Scientific accuracy is not guaranteed. Please do not use this visualization for interstellar navigation.

Sources:
Programmed by some space enthusiasts at Google.Music by Sam Hulick, whose work you may have heard in the video game, Mass Effect. The track is titled “In a Strange Land” and is used with his permission.
Galaxy images provided by Wikipedia and ESO/IDA/Danish 1.5m/R.Gendler and A. Hornstrup.
Star renderings derived from Wikipedia
Sun images courtesy of NASA/SDO and the AIA, EVE, and HMI science teams.
Star data provided by:HYG Database, by Astronomy Nexus
Gliese/Jahreiß Catalog, by Dr. Wilhelm Gliese and Dr. Hartmut Jahreiss
Bright Star Catalog (5th edition), by Dr. E. Dorrit Hoffleit and Dr. Wayne H. Warren Jr, and the Department of Astronomy at Yale University
HIPPARCOS Catalog (3rd Edition) by the European Space Agency

DID YOU KNOW?: A lunar day is a month on Earth!

A lunar day is the period of time it takes for the Earth’s Moon to complete one full rotation on its axis with respect to the Sun. Equivalently, it is the time it takes the Moon to make one complete orbit around the Earth and come back to the same phase. It is marked from a new moon to the next new moon.

On average, this synodic period lasts 29 days, 12 hours, 44 minutes and 3 seconds. Which just so happens to be what we call a synodic month here on Earth.

This is an average figure, since the speed of the Earth-Moon system around the Sun varies slightly over a year, due to the eccentricity of the orbit. The Moon’s own orbit also undergoes a number of periodic variations about its mean value, due to the gravitational perturbations of the Sun.

Types of Months used in Astronomy:

The following types of months are mainly of significance in astronomy, most of them (but not the distinction between sidereal and tropical months) first recognized in Babylonian lunar astronomy.

  1. The sidereal month is defined as the Moon’s orbital period in a non-rotating frame of reference (which on average is equal to its rotation period in the same frame). It is about 27.32166 days (27 days, 7 hours, 43 minutes, 11.6 seconds). The exact duration of the orbital period cannot be easily determined, because the ‘non-rotating frame of reference’ cannot be observed directly. However, it is approximately equal to the time it takes the Moon to pass twice a “fixed” star (different stars give different results because all have proper motions and are not really fixed in position).
  2. A synodic month is the most familiar lunar cycle, defined as the time interval between two consecutive occurrences of a particular phase (such as new moon or full moon) as seen by an observer on Earth. The mean length of the synodic month is 29.53059 days (29 days, 12 hours, 44 minutes, 2.8 seconds). Due to the eccentric orbit of the lunar orbit around Earth (and to a lesser degree, the Earth’s elliptical orbit around the Sun), the length of a synodic month can vary by up to seven hours.
  3. The tropical month is the average time for the Moon to pass twice through the same equinox point of the sky. It is 27.32158 days, very slightly shorter than the sidereal month (27.32166) days, because of precession of the equinoxes. Unlike the sidereal month, it can be measured precisely.
  4. An anomalistic month is the average time the Moon takes to go from perigee to perigee – the point in the Moon’s orbit when it is closest to Earth. An anomalistic month is about 27.55455 days on average.
  5. The draconic month or nodal month is the period in which the Moon returns to the same node of its orbit; the nodes are the two points where the Moon’s orbit crosses the plane of the Earth’s orbit. Its duration is about 27.21222 days on average.

A synodic month is longer than a sidereal month because the Earth-Moon system is orbiting the Sun in the same direction as the Moon is orbiting the Earth. Therefore, the Sun appears to move with respect to the stars, and it takes about 2.2 days longer for the Moon to return to the same apparent position with respect to the Sun.

An anomalistic month is longer than a sidereal month because the perigee moves in the same direction as the Moon is orbiting the Earth, one revolution in nine years. Therefore, the Moon takes a little longer to return to perigee than to return to the same star.

A draconic month is shorter than a sidereal month because the nodes move in the opposite direction as the Moon is orbiting the Earth, one revolution in 18 years. Therefore, the Moon returns to the same node slightly earlier than it returns to the same star.

Sources: Wikipedia, NASA Lunar Reconnaissance Orbiter.

Max Planck Society Invests €11 million in SKA precursor MeerKAT

MeerKAT Array
MeerKAT Array

The Minister for Science and Technology of South Africa and the President of the Max-Planck-Society (MPG) today announced that the MPG and the Max-Planck-Institute for Radio Astronomy (MPIfR) in Bonn will make available a total of €11 million (approximately R150 million) to build and install radio receivers on the South African MeerKAT radio telescope.

The receivers will be built by the MPIfR and will operate in the S band of radio frequencies. They will be used primarily for research on pulsars, the rapid spinning neutron star which emit very regular radio pulses and so can be used as highly accurate clocks to test extreme physics. Two other sets of receivers, for the L band and ULF band of frequencies, are already under construction in South Africa.

The President of the MPG, Martin Stratmann, said: “We consider MeerKAT to be an important undertaking as it is not only a preeminent astronomy project, but also a light-house project for science in Africa in general. The MPG is very pleased to enable close collaboration between its scientists and the South African community and looks forward to see MeerKAT’s first glimpse of the Universe with the receivers of the MPIfR”.

Welcoming the strong and growing collaboration between South Africa and Germany, Minister of Science and Technology, Naledi Pandor said that the investment is an endorsement of the excellence of the MeerKAT and the South African team which designed and is building it. Minister Pandor added that “this significant investment by a leading global research organisation of prestigious repute, home to several Nobel Prize winners, was an important vote of confidence, in South African science in general and the MeerKAT specifically.” South Africa and Germany have a vibrant science and technology partnership, with radio astronomy fast becoming a blossoming flagship area of cooperation, evidence by huge interest in academic and industrial cooperation from both sides. Minister Pandor concluded, “MeerKAT is already acclaimed internationally as a world-class instrument“ thanks to our partnership with Max Planck, MeerKAT’s ability to perform transformational science for the benefit of global knowledge production will be considerably boosted. Awaiting the start of construction of the SKA, South Africa and our international partners such as Max Planck, continue to set the pace for global radio astronomy.”

MeerKAT will be the most sensitive cm wave radio telescope in the world until the SKA is built. It is expected to do transformational science on pulsars and other areas of astronomy.