Dwarf galaxies are the most abundant galaxies in the universe. Yet understanding how these systems behave in galaxy group environments is still a mystery.
These objects are notoriously difficult to study because they are very small relative to classic spiral galaxies. They also have low mass and a low surface brightness, which means that, to date, we have only studied the dwarf galaxies in the nearby universe, out to about 35 million light years away.
My collaborators and I have been studying a dwarf galaxy named ESO 324-G024 and its connection to the northern radio lobe of a galaxy known as Centaurus A (Cen A).
The giant radio lobes are comprised of high energy charged particles, mostly made up of protons and electrons, that are moving at extremely high speeds. The lobes were created from the relativistic jet (shown in the image at the top) that is blasting out of the central core of Cen A.
These energetic particles glow at radio frequencies and can be seen as the fuzzy yellow lobes in the centre of the image (above), together with the neutral hydrogen intensity (HI) maps of its companion galaxies. The lobes now occupy a volume more than 1,000 times that of the host galaxy shown in the image at the top, assuming the lobes are as deep as they are wide.
These HI intensity maps are part of a large HI survey of nearby galaxies called the Local Volume HI Survey (LVHIS). These maps have been magnified in size by a factor of 10 so that they can be seen on such a large scale and are coloured by their relative distances to the centre of Cen A.
A green galaxy is at virtually the same distance from Earth as Cen A, while blue galaxies are in front of Cen A (closer to us) and red galaxies are behind it (farther away).
One of the striking things about this image is that out of the 17 galaxies overlaid onto the Cen A field, 14 are dwarf galaxies.
An interesting dwarf
The one object that really interested me after making this image was the dwarf irregular galaxy ESO 324-G024 (just above the black box). It has a long HI gaseous tail that extends roughly 6,500 light years to the northeast of its main body and it is at nearly the same distance as Cen A.
These two pieces of information right away made this a system worthy of investigation because we thought that perhaps there is a connection between this dwarf galaxy and the northern radio lobe of Cen A.
Nothing like this has ever been seen before, probably because galaxies that have giant radio lobes like Cen A are usually hundreds of millions to billions of light years away. Cen A is a special galaxy because it’s only about 12 million light years from Earth.
This was an interesting result and it told us that the northern radio lobe must be inclined toward our line of sight, because ESO 324-G024 was at nearly the same distance as Cen A. This had previously been suggested by studying the jet way down in the core of the host galaxy, but it had never been confirmed in this way before.
A wind in the tail
Next we investigated the mechanism responsible for creating the HI tail in ESO 324-G024. We looked at the likelihood of gravitational forces from the large, central host galaxy of Cen A as a potential culprit for ripping out ESO 324-G024’s gas. But we determined that it is simply too far away from the central gravitational potential for gravity to have created the tail.
So we explored ram pressure stripping, which is thought to be a dominant force for removing gas in galaxies within these kinds of groups. Ram pressure is a force created when a galaxy moves through a dense medium, and thus experiences a wind in its “face”.
It’s similar to holding a dandelion in your hand and then running as fast as you can go and watching the seeds blow away in the wind. At rest, the dandelion feels no wind and the seeds stay intact. But when you run, all of a sudden, the dandelion feels the wind created from your running and this wind blows away the seeds.
In this scenario, ESO 324-G024 is the dandelion and you represent gravity carrying the galaxy through space. We calculated the wind speed required to blow the gas out of ESO 324-G024 and compared this speed to the speed of ESO 324-G024 moving through space. It turns out that the two speeds did not match.
ESO 324-G024 seemed to be moving too slow for all of its gas to have been blown into its long tail. So we went back to our first conclusion about ESO 324-G024 being behind the radio lobe and surmised what may be happening.
We know that the charged particles inside the northern radio lobe of Cen A are moving extremely fast. If ESO 324-G024 is just now coming into contact with the posterior outer edge of the radio lobe of Cen A, which is likely due to its proximity to Cen A, then it is possible that ESO 324-G024 is not only feeling the wind generated from its own motion through space, but also the wind from the charged particles in the radio lobe itself.
This would be like you running with the dandelion and at the same time blowing on it. Therefore, we concluded that ESO 324-G024 is most likely experiencing ram pressure stripping of its gas as it passes close to the posterior edge of the northern radio lobe.
This means that these types of radio lobes must have wreaked havoc on their dwarf galaxy companions in the distant past. This is an interesting case study that showcases how dwarf galaxies may have been knocked about, blasted, by their larger companion galaxies.
Just how common are situations like this and how have they influenced dwarf galaxies over cosmic time? The answer is that we simply don’t know, but I look forward to exploring these questions.
By Eamonn Bermingham
It’s wider than a blue whale is long, weighs as much as 25 Asian elephants and will soon be helping to unlock the secrets of the Universe. Say hello to our new dish: Deep Space Station 36.
Fresh from showing the world the first close encounter images with Pluto last month, our Deep Space Communication Complex in Canberra welcomed the newest member of its dish family to the facility earlier today.
The Canberra Complex is one of three Deep Space Network stations capable of providing two-way radio contact with robotic deep space missions. The complex’s sister stations are located in California and Spain.
The new dish is part of a $120 million NASA investment at the site, adding to our four other antennae – though it will take another 12 months to completely fit out.
“It’s a massive investment by NASA and shows the confidence they have in Australia and our ability to manage these operations,” Facility Director Dr Ed Kruzins said today.
Earlier this year our Deep Space Complex celebrated its 50th birthday. Ed says NASA’s latest investment shows that Australia is here to stay when it comes to space communications.
So what’s so special about Australia when it comes to staring into space?
“Geographically, we’re uniquely placed to look at the southern part of the solar system, which is where many of the space missions are now headed. We’re now tracking 40 different space missions, mostly with NASA and some others with Japan and the European Space Agency, so we need this extra capacity to be able to monitor the skies 24/7, 365 days a year,” says Ed.
What can we expect to find?
As the first images from Pluto demonstrated, the Universe has a habit of surprising us.
“We didn’t expect to see some of the things that came back from Pluto and we’ll no doubt see more that we didn’t expect when signals start returning over the coming months. The Universe is full of things we don’t understand. Pluto is covered in ice and in very deep freeze so should be inert, but it isn’t. Why is that? We just don’t know yet.”
But the fascination doesn’t end with Pluto. From water on Mars to the possibility of life on the icy moons of Jupiter, you get a sense that we’re only beginning to understand our solar system – not to mention further afield.
“Our largest antenna, which is 70 metres in diameter, is the only one in the world that’s covering the Voyager 2 mission, which launched back in 1977. It’s recently gone interstellar, easily further than any manmade object has been before, *17.5 light hours away.”
Wow. Speaking of Interstellar, how about that movie?
“The first half of it was absolutely accurate, in that time does pass more slowly on a planet in higher gravity fields!”
If you’d like to find out more about our space research, gaze over here.
(*That’s very, very far away)
It’s already an exciting time for Australia in the field of astronomy and space science. But we’ve just received an astronomical boost with the announcement of CSIRO’s role with the Breakthrough Prize Foundation’s (BPF) US$100 million dollar search for extraterrestrial intelligence, called Breakthrough Listen.
CSIRO has signed a multi-million dollar agreement to use its 64 metre Parkes radio telescope in the quest to search for intelligent life elsewhere in the universe. Breakthrough Listen will be allocated a quarter of the science time available on the Parkes telescope from October 2016 for a period five years, on a full cost recovery basis.
The Parkes observations will be part of a larger set of initiatives to search for life in the universe. The ET hunters will also use time on the Green Bank telescope in West Virginia, operated by the US National Radio Astronomy Observatory, and a telescope at the University of California’s Lick Observatory.
CSIRO has the only capability for radio astronomy in the southern hemisphere that can deliver the scientific goals for the new initiative. The Parkes Radio Telescope is essential for the scientific integrity of the Search for Extraterrestrial Intelligence (SETI). It is ideally situated for a search such as this. The most interesting and richest parts of our own galaxy, the Milky Way, pass directly overhead. If we are going to detect intelligent life elsewhere, it is most likely going to be found in that part of the galaxy towards the centre of the Milky Way.
The Parkes Radio Telescope is also one of the world’s premier big dishes and has outstanding ability to detect weak signals that a search like this requires. It has always been at the forefront of discovery, from receiving video footage of the first Moon walk on 20 July 1969 (which was dramatised in the movie The Dish), to tracking NASA’s Curiosity rover during its descent onto Mars in 2012, to now once again searching for intelligent life.
It has also played a leading role in the detection and study of pulsars, small dense stars that can spin hundreds of times a second, the recent discovery of enigmatic (but boringly named) fast radio bursts, or FRBs, and in the search for gravitational waves.
Parkes also played a leading role in previous SETI searches. In 1995 the California-based SETI Institute used the telescope for six months for its Project Phoenix search. The Parkes telescope provided the critical capability to search the southern sky that could not be accessed using telescopes in the northern hemisphere.
The latest initiative is being led by a number of the world’s most eminent astrophysicists and astronomers. Professor Matthew Bailes, ARC Laureate Fellow at the Centre for Astrophysics and Supercomputing at Swinburne University of Technology in Melbourne, will be the Australian lead of the SETI observing team using the Parkes telescope.
The program will nicely complement the existing scientific uses of the Parkes telescope. Although it will take up a quarter of Parkes time, it will benefit the research undertaken during the other three-quarters of the time the telescope is in operation. It will enable even greater scientific capability to be provided to a wide range of astronomy research through both the financial support and through the provision of new data processing and analysis systems and techniques. Incredible advances in computing technology make it possible for this new search to scan much greater swaths of the radio spectrum than has ever before been explored.
Rather than trying to guess where on the radio dial astronomers might receive a signal, they can now search an entire region of the radio spectrum in a single observation. The dramatic increase in data processing capability has also meant that astronomers can analyse telescope data in new ways, searching for many different types of artificial signals. CSIRO is thrilled to be part of this global initiative which takes advantage of the significant advances that have been made in computation and signal processing since the search for extraterrestrial life began. The probability of detecting intelligent life is small but it is much greater today than ever before.
To be the first to discover intelligent life would be a phenomenal achievement not only for the scientific community but for all humankind.
For more of our astronomical feats, visit #CSIROSpace
By Indra Tomic
From the moment mankind looked up at the sky we’ve been fascinated by the possibility that we might not be alone in the Universe.
It’s been easy to let our imagination go into hyperdrive. We’ve fallen in love with ET, wanted to have Mr Spock over to a dinner party and dreamt of red cape shenanigans with Superman. Popular culture, and science fiction, have filled our minds with a breadth of extra-terrestrial characters because we want to believe there is more to this Universe than the humble limits of our Earth. After all, there are hundreds of billions of galaxies, some very small with only a few million stars, and others possibly having as many as 400 billion stars.
Can we really be the only form of intelligent life out there?
The quest to solve this cosmic mystery has just gotten more interesting… and exciting. Russian entrepreneur and venture capitalist, Yuri Milner and theoretical physicist and cosmologist, Stephen Hawking announced in London yesterday that the Breakthrough Prize Foundation will provide $100 million to dramatically accelerate the search for intelligent life in the Universe.
This initiative will be the most powerful, comprehensive and intensive scientific search ever undertaken for signs of intelligent life beyond Earth. It will involve an unprecedented survey of the 1,000,000 closest stars to Earth and it will scan the center of our galaxy and the entire galactic plane.
The program is being led by the world’s most eminent leaders’ in astrophysics and astronomy using three of the largest and most capable radio telescope’s in the world, CSIRO’s Parkes Radio Telescope, the Green Bank Telescope and Lick Observatory in the US.
We have the only capability for radio astronomy in the southern hemisphere that can deliver the scientific goals for the new initiative. Our Parkes Radio Telescope has always been at the forefront of space discovery for decades. We received video footage of the first Moon walk back on this day back in 1969, and we helped track NASA’s Curiosity rover during its descent onto Mars in 2012.
Actually, this isn’t the first time Parkes telescope has played a leading role in Searches for Extraterrestrial Intelligence (SETI). From February 1995 to March 2004, we were involved in the most ambitious SETI search conducted to date, called Project Phoenix. Even though it was successful in achieving many of its observing goals, there were no signs of ET detected.
The Parkes telescope provides critical and unparalleled capability to search the southern sky, with its ideal location it is perfectly positioned to provide the best and most powerful view of our galactic plane.
The planets have never been more aligned then they are today, making this endeavour possible – the availability of significant observing time on the world’s largest and most sensitive radio telescopes; significant developments in the field of astrobiology; and incredible advances in computing technology, making it possible to scan greater swaths of the radio spectrum than even before.
Not only will the program deliver excellent science and contribute to world-leading astronomy, but it’s projects like this that will inspire scientists of the future in the pursuit of an answer to the fundamental question, ‘Are we alone?’.
To read more about our work with the Breakthrough Prize Foundation, have a look at the FAQs page on our website.
We’re playing a vital role in NASA’s New Horizons mission, the first ever attempt to visit Pluto. Learn more about this historic exploration, and our other astronomical feats, at #CSIROSpace.
Talk about a long distance call.
Some time tonight, around 9:57pm AEST, we’re expecting a world-first ‘phone call’ from the outer edges of the solar system.
The team at our Canberra Deep Space Communications Centre (CDSCC) will be the first to hear from the New Horizons spacecraft as it completes its nine-and-half-year journey to the solar system’s most famous dwarf planet, Pluto. NASA and Johns Hopkins University Applied Physics Laboratory are the lead agencies on this multi-million dollar project, but our CDSCC facility will be integral in communicating with the far-flung vessel.
Scientists have never before had an opportunity to study Pluto and its surrounding moons (Charon, Hydra, Nix, Styx and Kerebros) with such detail and precision. Even images from Hubble have shown us little more than blobs. Using an immense array of sensors and cameras, New Horizons will send us the most comprehensive images and data from the icy dwarf planet the world has ever seen. This information will not only shed new light on Pluto’s mysteries, but it will also help us better understand the origin and evolution of Earth and our planetary neighbours.
Before New Horizons reaches its mission objective, let’s find out a little more about this spacecraft and the amazing science powering it to Pluto.
- A long time ago: New Horizons (NH) blasted off from Cape Canaveral in Florida on the 19th January 2006: the same year the X-Box 360 was released in Australia, the Beaconsfield mine disaster hit the headlines and Peter Brock and Steve Irwin passed away.
- A powerful name: The probe is powered by a single radioisotope thermoelectric generator (RTG), which transforms the heat from the natural radioactive decay of plutonium dioxide into electricity. Can you guess which dwarf planet plutonium-238 is named after?
- An interplanetary pit stop: NH made a quick detour to Jupiter in 2007. During this interplanetary layover, the probe used the opportunity to test some of its scientific instruments, before using the gas giant’s gravity to give it a 14,000km/h slingshot towards Pluto.
- Short but sweet: It’s only going to be in range of Pluto for 5 hours, capturing immense amounts of data, before it starts a new mission. After Pluto, NH will venture on to the mysterious Kuiper belt.
- A close-ish encounter: NH will duck between Pluto and its neighbouring moon, Charon, before it skims approximately 12,500 kilometres above Pluto’s surface, unleashing its suite of scientific observations.
- Me first: Our CDSCC will be one of the first places on Earth to receive the data from New Horizons, in binary form (a massive cache of 1s and 0s)… which is great if you can read the Matrix.
- Whispers from space: By the time it reaches Earth, the radio signals from New Horizons are 20 billion times weaker than the power of a watch battery. These are the signals captured and processed by CDSCC’s giant antenna dishes before being sent to waiting mission scientists.
- Six of the best: Alice, LORRI, Ralph, PEPSSI, SWAP and Rex. No, it’s not the next team of contestants on The Voice – these are the names of the six scientific instruments mounted to New Horizons. The instruments are equipped to collect a vast array of information, and include imaging spectrometers, particle detection instruments and a passive radiometer.
- Students riding shot-gun: There is also a plus-one tagging along: a dust particle counter created by a group of students from the University of Colorado, which puts pretty much every other student group student project in the history of the world to shame.
Remember to check out #CSIROSpace for the latest updates!
NASA has spent the last nine years navigating New Horizons towards Pluto. Within days, the first high resolution images will be beamed back to earth giving the world its first real insight into what makes the tiny ‘planet’ tick. But for now, not even NASA can claim to know very much about it. So we thought we’d speak to some of Australia’s youngest and brightest minds to see what they think.
In summary, here are five ways NASA can prepare for an encounter with Pluto.
- Before you get to Pluto give them a call, and let them know you’re coming: According to our ‘young astronomers’ there is a man on Pluto with a phone, and he may be able to tell you how cool or fun it is before you get there.
- Definitely pack a hairbrush: You never know when you’ll need to look your best. And you might just really like brushing your hair. Oh, and bring toys.
- Be prepared to eat a lot of cheese: Right now we don’t know exactly what Pluto is made of. One theory is that ‘like the moon’ it could be made of cheese. Hopefully a nice Brie or Camembert.
- Be aware of Pluto’s emotional state: Our young scientists have warned that Pluto may be dealing with some hurt feelings. Since it was forcibly removed from the planets’ friendship ring, Pluto is believed to be “upset, angry, stressed, left-out and unlucky”.
- It’s never too late to say sorry: NASA might consider apologising on behalf of planet Earth. #plutoisaplanet
We played a key role in the Pluto fly-by. Read more in our other Plu-tastic blog post.
By Adam Knight
We’re playing a vital role in NASA’s New Horizons mission, the first ever attempt to visit Pluto. Learn more about this historic exploration, and our other astronomical feats, at #CSIROSpace.
It’s more than five billion kilometres away, is smaller than our moon and it’s not even a planet. So why have we spent nine and a half years hurling a probe to the far reaches of the Solar System, just to catch a brief glimpse of a tiny ice dwarf known as Pluto?
Well for one, we know hardly anything about the composition of the dwarf planet and its moons. Learning more about how they formed will help us better understand the origins of our solar system.
But who knows what other secrets might be unlocked by the New Horizons spacecraft and its suite of scientific instruments: what ‘unknown unknowns’ we might discover when the data starts streaming on July 14?
Before the teams at NASA and John Hopkins University sink their teeth into this bounty of information, we thought we should take stock of some of the things we DO know about this odd chunk of ice and rock that sits on outer edge of the solar system.
1. Believed, and then seen: Pluto’s location was originally predicted by Percival Lowell in 1915, before being officially discovered on February 18, 1930 by Clyde Tombaugh at the Lowell Observatory in Arizona, USA.
2. When in Rome: Pluto was named by an 11 year old girl, Venetia Burney, after the Roman God of the underworld. Thankfully Pluto was chosen over the other options like Zymal, Constance and Cronus.
3. Out of its world: A list about Pluto would be incomplete without talking about the loss of its planet-hood status. In 2006 the International Astronomy Union finalised the definition of a planet, sadly Pluto was unable meet the criteria. Because Pluto is ‘unable to clear the neighbourhood around its orbit’ it was downgraded to the first ever dwarf planet.
4. You thought dial-up was bad: Even at the speed of light it will take 4.6 hours for our team at the Canberra Deep Space Communication Complex (CDSCC) to receive data from New Horizons.
5. Pluto’s pups: There are five moons in orbit around Pluto. Charon, the largest was discovered back in 1978. Hydra, Nix, Kerberos and Styx were all discovered between 2005 and 2012.
6. In’n’Out: At its closest point to the Sun or its ‘perihelion’ Pluto is 4.4 billion kilometres away. When it reaches its ‘aphelion’ or the point where Pluto is furthest from the Sun, the ice dwarf is 7.3 billion kilometres away from the warmth of our star. Because of this orbit, Pluto is periodically closer to the Sun than Neptune.
7. Long days, longer years: The length of a Pluto day is equal to 6 days, 9 hours and 17 minutes, compared to Earth’s 24 hours. It takes Pluto a whopping 247.9 Earth-years to complete one orbit of the Sun.
8. Bring a jacket: Temperatures on the planet range from a balmy -210C to -235C.
9. A rock and a cold place: Pluto is made up of one third frozen water with the remaining two thirds consisting of rock.
The New Horizons spacecraft is due to pass by Pluto on the 14th July, and our team at the CDSCC are ready to receive the first ever images and video as they’re sent through. NASA will be making much of it available soon after, so stay tuned as we will be sharing these images on our blog, Facebook, Twitter and Instagram.