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Current gravitational wave observatories have two significant limitations. The first is that they can only observe powerful gravitational bursts such as the mergers of black holes and neutron stars. The second is that they can only observe these mergers for wavelengths on the order of hundreds to thousands of kilometers. This means we can only observe stellar mass mergers. Of course, there’s a lot of interesting gravitational astronomy going on at other wavelengths and noise levels, which has motivated astronomers to get clever. One of these clever ideas is to use pulsars as a telescope.

The concept is known as a pulsar timing array (PTA). Pulsars are rotating neutron stars with a strong magnetic field aligned in such a way that it sweeps a burst of radio energy toward Earth with each rotation. We see them as a very regular radio flash. Some pulsars, known as millisecond pulsars, rotate so quickly that they emit hundreds of radio pulses a second. Since the rotation of a neutron star is almost as regular as clockwork, pulsars can be used as a kind of cosmic timepiece.

Because of this, if a pulsar moves in any way, such as orbiting a star, the relative motion of the pulsar causes the pulses to shift slightly. We can measure these shifts with extreme accuracy. Our observations are so precise pulsars were used to measure the orbital decay of binary systems as indirect evidence of gravitational waves long before we could observe them directly.

Even when pulsars aren’t part of a binary system, small gravitational tugs cause them to shift slightly. So when a gravitational wave passes through them, their pulses will shift by a tiny amount. These shifts are essentially at the random fluctuation level of the pulses themselves, so we can’t see the gravitational wave effect from a single pulsar. We need observations of lots of pulsars to see the statistical fluctuations. Hence, we need an array of pulsar timings.

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Multiple pulsars can pinpoint the source of gravitational waves. Credit: Kato & Takahashi

Earlier this year astronomers from the NANOGrav used an array of 67 pulsars with 15 years of data and were able to measure the background gravitational rumble of the Universe. The likely sources of this background are supermassive binary black holes (SMBHs), but the results weren’t entirely conclusive. One problem with the data is that while the team could measure the gravitational waves, they couldn’t pinpoint the point of origin for them.

There are several ongoing PTA projects, meaning that we will soon have a wealth of observational data. In a new study, a team proposes how this data could be used to pinpoint the sources of background gravitational waves. Their idea focuses on making precise distance measurements of the pulsars in an array. At the moment, while we know the distance to some pulsars very accurately, the distance of many pulsars is fuzzy. Detailed observations of PTA pulsars through observatories such as the Very Long Baseline Array could give us the precision we need. Knowing both the distance and the timing variation of a pulsar would give us a range for the source. With an array of pulsars, ranges would overlap to triangulate the source.

As the paper shows, a good level of accuracy could be obtained with a PTA of only a dozen pulsars. This initial study only focused on a 2-dimensional array, but a more 3D array should also be reasonably accurate. Certainly accurate enough to prove whether these background waves come from supermassive binary black holes, or something we don’t yet fully understand.

Reference: Kato, Ryo, and Keitaro Takahashi. “Precision of localization of single gravitational-wave source with pulsar timing array.” arXiv preprint arXiv:2308.10419 (2023).

The post Pulsars Detected the Background Gravitational Hum of the Universe. Now Can They Detect Single Mergers? appeared first on Universe Today.

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Iran Sent a Capsule Capable of Holding Animals into Orbit.

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Despite popular opinion, the first animals in space were not dogs or chimps, they were fruit flies launched by the United States in February 1947. The Soviet Union launched Laika, the first dog into space in November 1957 and now, it seems Iran is getting in on the act. A 500kg capsule known as the “indigenous bio-capsule” with life support capability was recently launched atop the Iranian “Salman” rocket. It has been reported by some agencies that there were animals on board but no official statement has been released.

The Iranian Space Agency (ISA) are gearing up to getting humans into space before 2029 but is testing its launch capability with animal passengers. The capsule was launched on December 6 2023 and attained an orbital altitude of 130 kilometres. According to their Telecommunications Minister Isa Zarepour, it is aimed at sending Iranian astronauts to space by 2029.

The “Salaman” solid-fuelled rocket was designed by the aerospace division of the Ministry of Science, Research and Technology and built and launched by the Ministry of Defence and Armed Forces Logistics. It has already been used to launch a data collecting satellite and in 2013 successfully sent and returned monkeys into space.

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Ham, a chimpanzee, became the first great ape in space during his January 31, 1961, suborbital flight aboard Mercury-Redstone 2 (Credit : NASA)

To date, only three counties have human spaceflight capability; USA, Russia and China. India are attempting to become the fourth as they work on their Gaganyaan program. Will Iran become the fifth!? Iran plans further tests with further launches bearing animal occupants before attempting to send humans up.

According to the Iranian Space Agency, its satellite program is purely for scientific research and other civilian applications. There is however, international suspicion because there are suspicions that the Salamn rockets could very easily be converted to long range missiles.

Source : Iran says it sent a capsule capable of carrying animals into orbit as it prepares for human missions

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What Could a Next Generation Event Horizon Telescope Do?

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Telescopes have come a long way in a little over four hundred years! It was 1608 that Dutch spectacle maker Hans Lippershey who was said to be working with a case of myopia and, in working with lenses discovered the magnifying powers if arranged in certain configurations. Now, centuries on and we have many different telescope designs and even telescopes in orbit but none are more incredible than the Event Horizon Telescope (EHT). Images las year revealed the supermassive black hole at the centre of our Galaxy and around M87 but now a team of astronomers have explored the potential of an even more powerful system the Next Generation EHT (ngEHT).

There is no doubt that our understanding of the processes within our Universe have come on leaps and bounds since the invention of the telescope. The resolution of these space piercing instruments is dictated by the telescope’s aperture. The technique known as interferometry hooks individual telescopes together and combines their signal so they act as one BIG telescope, boosting the resolution. 

Telescopes like the EHT have been using interferometry to great advantage to study black holes. These enigmatic and mysterious stellar corpses defy our probing; we do not fully understand their origins and processes and indeed our laws of physics break down if you get too close to the point source in the centre, the singularity. Due to their interaction with space and time, understanding the full nature of black holes will – hopefully – unlock our understanding of the Universe. 

Previously, observations have only revealed the movement of stars around galactic centre suggesting an object was lurking there weighing in at around 4 million times the mass of the Sun. Data from the EHT collected during 2022, finally revealed an image of the object at the centre – SgrA* – a super massive black hole and the matter in the immediate vicinity of the event horizon. Whilst this image did not reveal the black hole itself – another article required to explain that – it certainly revealed the telltale signs. 

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Sag A* compared to M87* and the orbit of Mercury. Credit: EHT collaboration

A recently published paper explores the possibilities of the ngEHT and how they might be able to unpick some of the physics around black holes. The ngEHT will increase the geographical footprint of EHT by 10 further instruments that span across the Earth.  Making use of the significant improvement in resolution, the ngEHT will also improve image dynamics range, provide a multi-wavelength capability and facilitate long term monitoring. 

The team conclude that future enhancements in measurement sensitivity and data analysis techniques in ngEHT will substantially advance our understanding of black holes and the immediate environments surrounding them with particular focus on the photon ring, mass and spin analysis, binary supermassive black holes and more besides.

Source : Fundamental Physics Opportunities with the Next-Generation Event Horizon Telescope

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Déjà vu All Over Again: Backpacking in Glacier National Park

By Michael Lanza

In the second week of September, the cool air in the shade of the forest nips at our cheeks as we leave our first night’s camp beside Glenns Lake in the backcountry of Glacier National Park, starting at a reasonably early hour for a day where we will walk nearly 16 miles and 6,000 feet of combined uphill and downhill. I’m hiking in a fleece hoodie, pants, and gloves and my friends Pam Solon and Jeff Wilhelm are similarly layered up. Once the sun reaches us within an hour, we’ll strip down to shorts and T-shirts.

Where the trail crosses a meadow, the expansive view west across a calm and insistently blue Cosley Lake reveals what looks like a long wall of overlapping stone shields jammed into the earth, each 2,000 or more feet tall and tilting at different angles. At the lake’s outlet—now in warm sunshine—we ford the Belly River, ankle- to calf-deep here with just a few tiny riffles and not very cold. More hiking through quiet forest brings us to the refrigerated, cliff-shaded alcove below Dawn Mist Falls, which spills thunderously over a sheer drop and crashes onto fallen boulders at its base, its force releasing a perpetual mist. Moss wallpapers the alcove’s short cliffs.

A backpacker hiking the Ptarmigan Tunnel Trail in Glacier National Park.
” data-image-caption=”Pam Solon backpacking the Ptarmigan Tunnel Trail in Glacier National Park.
” data-medium-file=”″ data-large-file=”″ src=”″ alt=”A backpacker hiking the Ptarmigan Tunnel Trail in Glacier National Park.” class=”wp-image-61144″ srcset=” 1024w, 300w, 768w, 150w, 1200w” sizes=”(max-width: 900px) 100vw, 900px” data-recalc-dims=”1″ />Pam Solon backpacking the Ptarmigan Tunnel Trail in Glacier National Park.

After a thoroughly relaxing lunch break on the pebbly beach at Elizabeth Lake—where the perfect combination of solar warmth and soft breeze probably converts in direct value to about a thousand hours of counseling—we start the long climb to the Ptarmigan Tunnel. Reaching the open alpine terrain, I repeatedly stop to spin 180 degrees and take big bites of our view of the valley of Helen and Elizabeth lakes and the peaks on the other side, which shelter what remains of a couple of glaciers in the shade of north-facing cliffs just below the mountaintops.

I’ve backpacked this trail before; this isn’t new to me. But time slowly renders a bit fuzzier the memory of how constantly breathtaking it is—which is, in a funny way, a gift to us: We get to experience that awe anew each time.

Everyone laughed when the legendary Yogi Berra said, “It’s like déjà vu all over again,” but I think I knew what he meant.

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