Astronomy News for August 2023: A cold Brown Dwarf star is found to be broadcasting radio waves and how Astronomers took a picture of the Milky Way, using Neutrinos instead of light!

We humans like to place the objects we find into distinct categories, male or female, dog or cat, living or non-living. Nature doesn’t really work that way however, the edges between different classes of objects are often quite fuzzy. Take stars and planets for example, back in my post of 22 September 2021, I discussed an relatively new class of objects called brown dwarfs, objects that are too heavy to be planets, but too light to be stars.

Brown Dwarfs are too big to be planets but too small to ignite the fusion processes that power regular stars. (Credit: EarthSky)

Strictly speaking brown dwarfs do not have enough mass to cause the pressure and temperature at their core to ignite the process of hydrogen fusion. They are larger than planets however and do emit some infrared light because the gasses they are made of continue to collapse due to gravity and that shrinking generates heat.

Strictly speaking the planet Jupiter is actually emitting a little more energy than it receives from the Sun because even after 4 billion years it is still shrinking. (Credit: European Space Agency)

One of the smallest, and coolest brown dwarfs ever discovered is known as WISE J062309.94-045624.6, (I’ll just call it J06 from now on) which is located about 7 light years from our solar system. The size and mass of J06 are only approximately known, its diameter is between 0.95 and 0.65 that of Jupiter while it’s mass is at least four time Jupiter’s, but not more than 44 times. We do have a rather accurate measurement of it’s surface temperature however, around 425ºC making it about as hot as a wood burning fireplace.

The Wide-Field Infrared Survey Experiment or WISE space telescope searches the sky for objects that are only emitting light in the infrared. (Credit: Wikipedia)

Being so cool it was something of a surprise therefore when observations of J06 by the CSIRO ASKAP radio telescope in Western Australia showed that the dwarf was broadcasting periodically at frequencies between 0.9 and 2.0 Giga-Hertz (That’s between 900 million and 2 billion cycles per second). These observations were later confirmed with the Australia Telescope Compact Array and South Africa’s MeerKAT telescope.

Unlike the images we get from Hubble or ground based telescope this is the sort of data we get from radio telescopes. These are some of the actual measurements from J06. (Credit: IOPscience-Institute of Physics)

The time period for the radio emissions was found to be about 1.91 hours which is thought to be the time it takes the dwarf to rotate on its axis, its day that is. An analysis of the data from J06 by researchers at the University of Sydney, including lead author Ph.D. candidate Kovi Rose has led to the conclusion that the dwarf possesses a magnetic field of greater than 700 gauss that is generating the radio emissions.

University of Sidney Ph.D candidate Kovi Rose. (Credit: Cosmos Magazine)

Only a small number of Brown Dwarfs have been discovered so far by astronomers and there is much we don’t know about this class of celestial objects. Only by finding more dwarfs, maybe by using their radio emissions to detect them, can we learn more about these objects.

South Africa’s MeerKAT antenna array is becoming one of the centers for the study of Brown Dwarfs. (Credit:

Unlike normal stars, Brown Dwarfs are studied by observing them in the infrared or radio portions of the electro-magnetic (EM) spectrum. One hundred years ago such observations could not have been carried out simply because the instruments needed to detect infrared and radio energy did not exist. Today however astronomers also have instruments that allow them to observe in the Ultra-Violet and X-ray portions of the EM spectra so that we can “see” the Universe in those lights as well.

Since X-rays are quickly absorbed by out atmosphere astronomers have to study them using space telescopes like the Chandra X-Ray probe shown here. (Credit: NASA)

More than that, today astronomers can even make observations of the Universe using Cosmic Ray particles and Gravity Waves, see my posts of 14 June 2017 and 22 October 2017. In fact every time that astronomers have found a new way to observe the Universe, a new form of energy with which to make astronomical studies, they have discovered whole new kinds of celestial objects and learned even more about the objects they already knew.

The LIGO observatory was the first to detect and study the Universe using gravity waves instead of light. (Credit: LIGO Caltech)

One type of radiation that astronomers that tried for a long time to employ are neutrinos, those ghost like sub-atomic particles that can pass through the entire Earth with hardly any of them interacting. That’s why neutrinos are so hard to use for astronomical observations, you need huge detectors, and lots of time, in order to catch just a few of them.

In order to capture just a few neutrinos you need huge detectors buried deep underground. (Credit: Nature)

That hasn’t stopped astronomers and astrophysicists from trying to use neutrinos however. The first time was a neutrino detector buried in the Homestake mine in South Dakota that was designed to detect neutrinos produced by the process of hydrogen fusion deep within the Sun. This experiment ran from 1970 to 1994 and taught us a great deal about both the Sun and neutrinos. Then, in 1987 the first supernova in our galaxy for over 300 years was detected and just as astrophysicists had predicted the Sudbury neutrino experiment detected about a dozen neutrinos from the distant event.

Buried in a massive glacier in Antarctica the Ice Cube neutrino detector is by volume the largest scientific experiment ever built. (Credit: Ice Cube Neutrino Observatory)

Now astronomers have constructed the largest, in terms of volume, experiment ever in the ice covered continent of Antarctica. The Ice Cube Telescope as it is known uses the fact that when a neutrino does interact with more normal matter it causes the emission of a few photons of light, photons that can travel a considerable distance through the Antarctic ice.

The scientists who operate Ice Cube live right above their instrument in this building near the south pole. (Credit: Wikipedia)

The Ice Cube Telescope was constructed with a full cubic kilometer of glacial ice near the Amundsen-Scott South Pole Station. Drilling holes down into the ice scientists buried over 5,000 light detectors so that they could detect the light generated by any neutrinos that were absorbed in that cubic kilometer of ice. Despite its huge size the Ice Cube detector still only captures a small number of neutrinos every day so, like taking a picture in very low light, in order to form any kind of image a long exposure time was required.

Taking a picture at night or in any low light conditions requires a time exposure like in the image here. (Credit: Visual Wilderness)

In fact it took over 10 years to collect 60,000 neutrino generated collisions and a special computer algorithm in order to form the first ever neutrino image of our Milky Way galaxy. Researchers from Drexel University’s Department of Physics Naoko Kurahashi Neilson, Associate Professor along with graduate student Steve Sclafani performed the processing that produced the image shown below.

The way our Milky way galaxy looks in radio (top), optical and gamma rays and now in neutrinos (bottom). (Credit: American Physical Society)
Naoko Kurahashi Neilson in her office at Drexel University and at the Ice Cube observatory in Antarctica. (Credit: UMKC WordPress)

This picture represents the birth of an entirely new kind of astronomy, neutrino astronomy. Right now we can only guess what neutrino images will tell us about the objects we already know about, but more importantly what new kinds of astronomical objects will be discovered using neutrinos.

The Low Frequency Array (LOFAR) consortium centered in Belgium is working to construct a Radio Telescope that is effectively as large as all of Western Europe.

Ever since the telescope was first used by Galileo to study the heavens astronomers have built bigger and bigger telescopes to aid them in their work. To an astronomer the bigger the telescope the better for two basic reasons, the first reason is simply that the bigger the telescope the more light it can collect. This extra light allows objects that are too dim to be seen with the unaided eye to become visible. Point even a small telescope at a portion of the sky where you see only one or two stars and suddenly you’ll see dozens of stars because the telescope has a larger area to gather more light from those dimmer stars.

All of the galaxies seen in this image taken by the Hubble Space Telescope are far to dim to be seen with our eyes. But because the light gathering area of Hubble is so much larger it can gather much more light making these dim objects visible. (Credit: Science News)

The second reason is that a telescope, because of its ability to magnify what it sees, can separate two objects that appear to the naked eye to be a single object. Soon after a child receives their first telescope, and after a few nights looking at the Moon and a few planets they will turn to look at a star like Rigel or Spica in order to see how a single star becomes two or even more stars in their new ‘scope.

Equation for calculating the resolution, the ability of a telescope to separate two very close objects. For a visible telescope the wavelengths of light are so small even a small ‘scope does a good job but at radio frequencies the wavelengths are so large that a huge telescope is needed. (Credit: Telescope Nerd)

This ability to resolve the details of distant objects is a function of the size of the telescope divided by the size of the wavelength of the Electromagnetic waves it is designed to collect. For an optical telescope the wavelength of visible light is very small so they tend to have a lot of resolution. For radio telescopes however the waves they collect can have wavelengths that are centimeters or even meters long. In fact at a low frequency like 3 Mega-Hertz (MHz) the wavelength is actually a full 100m.

Radio waves have wavelengths ranging from centimetres to kilometres in length. (Credit: YateBTS)

This has always made the ‘images’ produced by radio telescopes much ‘fuzzier’ than those from optical telescopes. Over the last couple of decades however radio astronomers have developed a workaround thanks to the enormous progress in computer and communications technology. What they have done is link as many as a dozen radio telescopes in different parts of the world together electronically so that the signals they collect are added together by a supercomputer, effectively making the separate telescopes into a single one with a size of nearly the entire planet.

Combining the energy received by twelve radio telescopes spread across the world astronomers succeeded in obtaining the first image of a black hole. (Credit: BBC)

As mentioned in a previous post 17 April 2019, this technique is being used to provide the most detailed images ever obtained of the supermassive black holes at the center of galaxies along with other objects of interest. The telescopes used in these projects however were not originally designed to be used in conjunction with other scopes.

First image taken of a Black Hole obtained by an array of radio telescopes spread across the entire Earth and added together in a computer. (Credit: NASA)

Now a large array of radio receivers that are designed to act as a single radio telescope has been constructed at sites spread out over a sizeable portion of the Earth’s surface. Known as the LOw Frequency ARray or LOFAR project and originally funded as a national program by the government of the Netherlands LOFAR has now grown to include most of the countries of Western Europe.

Originally started as a project by the government of the Netherlands LOFAR has grown to cover western Europe. (Credit: Earth Observation Portal)

Currently LOFAR consists of 38 stations in the Netherlands, 24 core stations in the province of Exloo and 14 remote station spread around the rest of the country. There are also 14 international stations, 6 in Germany, 3 in Poland and one each in Ireland, the UK, France, Sweden and Latvia with a fifteenth station under construction in Italy. Each station is composed of 96 Low Band Antennas (LBAs) that receive signals between 10 and 90 MHz, along with 48 High Band Antennas (HBAs) that receive in the 120 to 240 MHz band. All together this makes for a total of more than 70,000 antennas in the LOFAR array. Each station also has the computer facilities to completely digitize all of the signals received by its antennas so that the data can be combined with those from all the other stations making LOFAR the highest resolution radio telescope ever built.

One of the LOFAR remote antenna stations in Holland. The high band antennas are to the left and the low band antennas are to the right.
Design for the layout of a LOFAR remote antenna station. (Credit: LOFAR)
Ground level view of some LOFAR antennas. Because they are simple, and cheap to build a very large number can be built increasing the amount of signal the entire array can receive. (Credit: BDFRMA)

The initial results published by the LOFAR consortium have dealt with detailed studied of the radio emissions from the supermassive black holes at the center of galaxies. When combined with optical images of the galaxy containing the black holes, see image below, astronomers can get a much more complete picture of the influence of supermassive black holes on their host galaxies.

This image of the galaxy Hercules A was made by combining a Hubble image in visible light with a LOFAR image at radio frequencies. The LOFAR data consists of the two jets streaming out from the galaxy itself, which is a tiny object in the center. The jets are generated by a supermassive black hole in the center of the galaxy which is feeding and generating huge amounts of energy. (Credit: R. Timmerman, LOFAR and Hubble)

Other studies planned for LOFAR include a full scale investigation into the early period of the Universe known as the ‘Period of Re-Ionization’ when the first stars and galaxies heated the gas and dust created by the big bang. LOFAR will also be employed to study transient sources like pulsars and fast radio bursts (FRBs). Closer to home LOFAR will study our Sun and in particular the solar wind of high energy particles emitted by the Sun.

The LOFAR array will also be used to study the solar wind and solar flares giving scientists a beeter idea of conditions on the Sun. (Credit: Astronimy and Astrophysics Group)

Best of all the LOFAR partnership has already submitted its plan to the EU for LOFAR2.0, a major upgrade to the system that is planned to commence in 2022. One can only guess at what wonders that system will reveal.

Astronomers think that they have finally solved the mystery of ‘Fast Radio Bursts’ (FRBs), and what are FRBs anyway?

Go out some clear night and look up at the night sky, it’s much better if you can get away from big city lights by the way. If you think about it there really aren’t that many different types of objects up there. Aside from the Moon, if it’s out, all there really is up there are a lot of points of light, stars. O’k some stars are certainly brighter than others, and if you look closely it is easy to see that there are some stars with distinct colour to them. Nevertheless, from here on Earth the Universe just looks like a lot of points of light, a lot of stars.

The night sky may look beautiful, but there really don’t appear to be a lot of different types of objects. Appearances can be deceptive however. (Credit: Forbes)

Of course we all know that’s not true. With the invention of the telescope we quickly learned that stars and planets are very different. We also learned that some stars are giants while some are dwarfs.

The visual differences between the stars is summed up in the Hertzsprung Russell Diagram. (Credit: Chandra X-ray Observatory)

Then, as new types of telescopes were invented, other stranger kinds of objects were discovered. Radio telescopes discovered both quasars and pulsars while X-ray telescopes discovered black holes. One very unusual discovery was made when CIA spy satellites were the first to observe Gamma Ray bursts.

Quasars are the brightest steady objects in the Universe. They are now known to actually be a supermassive Black Hole in the center of a galaxy that is feasting on nearby stars, releasing some of that energy. (Credit: Hubble Space Telescope)

Based upon the observations from those telescopes astrophysicists then had to figure out what those objects actually were. Quasars for example turned out to be supermassive black holes in the centers of distant galaxies that are devouring nearby stars and releasing some of that energy feast. Pulsars are the remains of stars that went supernova, been crushed down into neutron stars and are emitting radio waves like a lighthouse. Gamma Ray Bursts on the other hand are caused by giant stars collapsing into black holes.

A Gamma Ray Burst (GRB) is even brighter than a Quasar but it only lasts for a few seconds. When a supermassive star explodes as a supernova some of its energy is released as gamma rays creating the GRB.

Fast Radio Bursts (FRBs) are the newest member of the cosmic zoo. Now FRBs are exactly what they sound like.  Without any warning a powerful burst of radio waves occurs that only lasts for a tiny fraction of a second. Transient events like FRBs are a curse to scientists because you’re never looking right at it when it happens, and by the time you say ‘what was that’ and turn around to look at it it’s gone.

The Parkes radio telescope in Australia. Large reflector dishes such as Parkes can only observe a small region of the sky at any one time. That’s what makes finding transient objects such as an FRB so difficult. (Credit: Square Kilometre Array)

In fact the very first FRB was actually ‘discovered’ in an analysis of old data from the Parkes Observatory in Australia. The data had been collected in 2001 but the FRB wasn’t recognized until 2007. Then it wasn’t until the 15th of January in 2015 that an FRB was detected live, also at Parkes Observatory. Canada’s new Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope, which unlike other radio telescopes is designed to have a wide field of view, has detected dozens of FRBs since it first went online in 2018.

The CHIME telescope in Canada is a different type of radio telescope that has a wider field of view. That now makes it the go-to instrument for studying FRBs. (Credit: Phys.org)

One of the few things that we do known about FRBs is that the most common frequencies of the burst are from around 800-1400 Mega-Hertz (MHz), that’s not to far from the frequencies used by your cellphone. Also, when astronomers say fast they mean really fast, each event being a single spike of radio waves lasting no more than a few milli-seconds. And because FRBs are scattered evenly across our sky, rather than being concentrated along the Milky Way, they must come from intergalactic space, perhaps as far away as billions of light years. At those enormous distances the energy released during those few milliseconds must be more than our Sun emits over the course of more than a dozen years.

A typical observation of an FRB. The burst releases different amounts of power at different frequencies but the entire event only last a few milli-seconds. (Credit: Daily Mail)

The mystery of FRBs has generated a lot of attention in the astronomy field and with all of that interest it’s not surprising that new discoveries are being made every year. A few FRBs have been discovered that are irregular repeaters, that is they have erupted more than once but without a predictable pattern. On the other hand FRB 180916 has been found to repeat on a schedule of once every 16.35 days. (By the way FRBs are numbered by the year, month and day they were first observed hence FRB 180916 was observed on the 16th of September in 2018.)

Just this past April an FRB was definitively detected as coming from inside our own galaxy and astronomers believe that they can even identify the source as the known object magnetar SGR 1935+2154 which is located in the constellation Vulpecula at a distance of about 30,000 light years. This is significant because some astrophysicists have been promoting magnetars as a possible source for FRBs for the past several years.

A magnetar is the dead corpse of a star that blew up as a supernova. The remaining core has been chrushed so small that its magnetic fiend is super intensified! (Credit: Quanta Magazine)

Now magnetars are the dead corpses of massive stars that exploded as supernovas. What remains after that explosion is an object about as massive as our Sun crushed down to the size of a city, an object so dense that it has become composed mainly of neutrons, a neutron star. As the star was squeezed its magnetic field also got compressed. But while compressing a magnetic field may decrease its size it also increases its intensity and a neutron star with a particularly strong magnetic field is given the special name of magnetar.

But wait, didn’t I say near the top of this post that neutron stars are also known as pulsars. Yes indeed, in fact all of these creatures are so closely related that astrophysicists argue all of the time where one class ends and another begins, in fact many neutron stars may be both pulsars and magnetars at the same time.

Pulsars also are the dead core of supernovas, and they also have very strong magnetic fields. So is there any real difference between a pulsar and a magnetar? Perhaps not very much. (Credit: Pinterest)

And just because one FRB has been identified as coming from a magnetar doesn’t mean that they all do. There may be even more exotic animals in the cosmic zoo that are as yet completely unknown such as dark matter particles or even cosmic strings. So far we’ve figured out a bit about FRBs but there’s still a lot more to learn. But then isn’t that the whole fun of astronomy!

The Big Dish: Scientists and Engineers are completing their designs for the World’s largest Radio Telescope, the Square Kilometer Array

When most people think about telescopes they immediately think of a long tube with either lenses or mirrors to gather visible light and magnify the resulting image. For a good three hundred years from the time of Galileo until less than a hundred years ago these were the only type of telescope that existed.

Starting in the 1950s however a new kind of telescope came into use by astronomers, radio telescopes. Telescopes that were designed to gather radio waves from outer space and whose images allowed astronomers to look at the universe in a whole new way.

Radio telescopes however have one big disadvantage when compared to their optical cousins. Since a radio wave is a million or more times longer than a wave of visible light a radio telescope has to be a million times bigger than an optical telescope in order to see with the same precision, the same definition. In fact you’d need a radio telescope 120 kilometers across in order to have the same resolution as the little 12cm telescope I had when I was growing up. Because of this the need to built ever bigger radio telescopes, and to find ways to still keep the costs down, has been one of the key engineering problems of modern science. A big step forward will be the construction of the Square Kilometer Array (SKA) radio telescope in western Australia.

Now Murchison Shire in Western Australia is probably the best place in the world to build a radio telescope because in an area the size of New Jersey there are less than a thousand residents. The image below gives some idea of the emptiness of Murchison Shire.

Murchison Shire (Credit: Google)

Because Murchison Shire is so uninhabited that means the place is radio quiet, no TV stations, no radio stations or cell phone towers to generate signals that could interfere with the signals coming from pulsars or stellar nurseries or distant galaxies.

Also, because there are different types of radio waves, long waves, short waves, microwaves the SKA will actually be composed of three different antennas occupying the same area of land. One of the arrays, the SKA Low (SKAL) antennas will receive signals in the 50 to 350 MHz (that’s 50 to 350 million cycles per second) frequency range. The entire SKAL will consist of tens of thousands of antennas that resemble wire Christmas Trees, see image below. One of the advantages of Radio Telescopes is that it is relatively easy to add the signals from two or more antennas in order to get an effectively bigger telescope.

Square Kilometer Array Low Antennas (Credit: SKA)

The Murchison Widefield Array (MWA) will operate in the same manner, a huge number of small antennas combining their signals in order to do the job of one huge antenna. The image below shows some of the first antennas of the MWA.

Murchison Widefield Array Antennas (Credit: SKA)

The SKA will also have some of the large dish antennas commonly associated with radio astronomy. 188 dishes between 13 and 15 meters in diameter will make up the SKA Pathfinder telescope. The Pathfinder telescope will also digitally combine its signals with another set of 197 radio dishes in South Africa effectively making them a telescope whose resolution is equivalent to one the size of the Indian Ocean. The image below shows some of the dishes of the Pathfinder telescope.

Pathfinder Dish Antennas (Credit: SKA)

It is estimated that with the current level of funding from ten member nations the Square Kilometer Array will be completed by 2025 but another advantage about combining thousands of small radio telescopes into a big one is that even a partially completed array can still do useful work. Astronomers hope that the SKA will soon be giving them a better view of objects in space that cannot be studied in visible light. I expect the discoveries to start very soon.

If you’d like to learn more about the Square Kilometer Array click on the link below to be taken to their website. (You can also  find out if your country is a part of the SKA organization!)

Square Kilometre Array – Home