When it comes to telescopes, bigger really is better. A larger telescope brings with it the ability to see fainter objects and also to be able to see more detail. Typically we have relied upon larger and larger single aperture telescopes in our attempts to distinguish exoplanets around other stars. Space telescopes have also been employed but all that may be about to change. A new paper suggests that multiple telescopes working together as interferometers are what’s needed.
When telescopes were invented they were single aperture instruments. A new technique emerged in the late 1800’s to combine optics from multiple instruments. This achieved higher resolution than would ordinarily be achieved by the instruments operating on their own. The concept involves analysis of the interference pattern when the incoming light from all the individual optical elements is combined. This is used very successfully in radio astronomy for example at the aptly named Very Large Array. It is not just radio waves that are used, infra-red and even visible light interferometers have been developed saving significant costs and producing results that would otherwise not be achievable from a single instrument.
Image of radio telescopes at the Karl G. Jansky Very Large Array, located in Socorro, New Mexico. (Credit: National Radio Astronomy Observatory)One area of astronomical research is the study of exoplanets. Observing alien worlds orbiting distant stars presents a number of challenges but the two key difficulties are that they lie at great distances and orbit bright stars. The planets are usually small and faint making them almost (but not quite) impossible to study directly due to the brightness and proximity to their star. Some understanding of their nature can be gleaned from using the transit method of study. This involves studying starlight as it passes through any atmosphere present to reveal its composition.
Direct imaging and study is a little more challenging and requires high resolution and sometimes a way of blocking light from the nearby star. To achieve direct observations requires angular resolution of a few milliarcseconds or even less (the full Moon covers 1,860,000 milliarcseconds!) This depends largely on the planets size and distance from Earth and from its host star. To give some idea of context, to resolve a planet like Earth orbiting the Sun from a distance of just 10 light years requires an angular resolution of 0.1 milliarcseconds. The James Webb Space Telescope has a resolution of 70 milliarcseconds so even that will struggle.
This artist’s impression depicts the exomoon candidate Kepler-1625b-i, the planet it is orbiting and the star in the centre of the star system. Kepler-1625b-i is the first exomoon candidate and, if confirmed, the first moon to be found outside the Solar System. Like many exoplanets, Kepler-1625b-i was discovered using the transit method. Exomoons are difficult to find because they are smaller than their companion planets, so their transit signal is weak, and their position in the system changes with each transit because of their orbit. This requires extensive modelling and data analysis.A paper recently authored by Amit Kumar Jha from the University of Arizona and a team of astronomers explores this very possibility. They look at using interferometry techniques to achieve the required resolutions, at using advanced imaging techniques like the Quantum Binary Spatial Mode Demultiplexing to analyse the point spread function (familiar to amateur astronomical imagers) and at using quantum based detectors.
The study draws upon radio interferometric techniques with promising results. They showed that a multi-aperture interferometry approach utilising quantum based detectors are more effective than single aperture instruments. They will provide a super-resolution imaging solution that has to date not been used in exoplanetary research. Not only will it hugely increase resolution, it’s also a very cost effective way to observe exoplanets and indeed other objects across the cosmos.
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Pluto may have been downgraded from full-planet status, but that doesn’t mean it doesn’t hold a special place in scientist’s hearts. There are practical and sentimental reasons for that – Pluto has tantalizing mysteries to unlock that New Horizons, the most recent spacecraft to visit the system, only added to. To research those mysteries, a multidisciplinary team from dozens of universities and research institutes has proposed Persephone – a mission to the Pluto system that could last 50 years.
New Horizons rocketed past the Pluto system in 2015, which is now technically considered part of the Kuiper Belt. The mission collected data on the dwarf planet and its unique moon, Charon. Scientists have now had time to analyze the data from that mission, and it left them wanting more—in particular, data about some of the surface features that they observed.
Persephone has four main scientific questions it is designed to answer, according to a paper published back in 2021:
1) “How has the population of the Kuiper Belt evolved?”
2) “What are the particle and magnetic field environments of the Kuiper Belt?”
3) “How have the surfaces of both Pluto and Charon changed?”
4) “What are the internal structures of Pluto and Charon?”
That last one might be the most intriguing, as the answer for Pluto’s internal structure might be that it has a subsurface ocean despite being so far away from the Sun. There is already some evidence for this, as Pluto appears to have an active surface, and an ice sheet called Sputnik Planitia could potentially be caused by a subsurface ocean. We don’t have enough data yet to prove it.
That is what Persephone is designed to provide. Unfortunately, with the unforgiving logic of orbital mechanics and current constraints on propulsion technology, any such mission would take multiple decades, even with a gravity assist from Jupiter. The mission design for Persephone has been operational for almost 31 years, including a 28-year cruise phase and a three-year orbit period around Pluto and Charon. It could then have an extended operational mission to visit other Kuiper belt objects to help constrain the variance in the different kinds of objects in that massive section of space.
That travel time could be helped by the development of a more effective nuclear electric propulsion system, which could shave up to 2 years off it even with a heavier payload than currently planned for Persephone. Such a system has been described but might not be available for the planned 2031 launch date for Persephone on board an SLS rocket.
Fraser discusses the longevity of spacecraft, which will definitely be a consideration for any future missions to Pluto.Persephone will take a suite of sensors, no matter its propulsion system, which can be “brought to bear on any and every object encountered during the mission,”. According to the flight plan, that would include Jupiter and its moons. These sensors include cameras, spectrometers, radar, magnetometers, and altimeters to meet the mission’s necessary science objectives.
A critical differentiator for the mission is that it is designed to be an orbiter rather than a flyby. According to the authors, much of the data needed to be collected would be infeasible with the short period a flyby would provide with the system. An orbiter would be able to stick around and collect data over the three-year period about both Pluto and Charon, including their active surface dynamics.
This proposal is just one of many mission proposals to the outer planets seeking further funding, and a preliminary estimate of $3bn puts it in the higher range of those missions. But if it is funded in some capacity, it could provide answers to the questions that New Horizons posed, even if it would take several decades to reach them.
Learn More:
Howett et al – Persephone: A Pluto-system Orbiter and Kuiper Belt Explorer
UT – The (Dwarf) Planet Pluto
UT – NASA’s New Horizons Mission Still Threatened
UT – New Horizons is Funded Through the Decade. Enough to Explore Another Kuiper Belt Object
Lead Image:
Graphic of Pluto being visited by Persephone and all the different questions the mission could answer.
Credit – Howett et al.
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If you were lucky enough to observe a total eclipse, you are certain to remember the halo of brilliant light around the Moon during totality. It’s known as the corona, and it is the diffuse outer atmosphere of the Sun. Although it is so thin we’d consider it a vacuum on Earth, it has a temperature of millions of degrees, which is why it’s visible during a total eclipse. According to our understanding of black hole dynamics black holes should also have a corona. And like the Sun’s corona, it is usually difficult to observe. Now a study in The Astrophysical Journal has made observations of this elusive region.
For an active black hole, it’s generally thought that there is a donut-shaped torus of gas and dust surrounding the black hole, in which there is an accretion disk of heated material aligned along the rotational plane of the black hole. Streaming from the polar regions of the black hole are jets of ionized gas speeding away at nearly the speed of light. This model would explain the various types of active galactic nuclei (AGNs) we observe, since the orientation of the black hole relative to us changes the appearance of the AGN.
According to the model, the innermost region of the accretion disk should be a superheated region at near vacuum density, which streams into the black hole. It is a corona like the Sun’s, but instead of millions of degrees, it has a temperature of billions of degrees. But because it’s so diffuse, its light is overwhelmed by the light of the accretion disk.
Diagram of the polarization behavior of obscured black holes. Credit: Saade, et alIn this new study, the team used a trick similar to observing the Sun’s corona during a total eclipse. The orientation of a black hole relative to us means that for some black holes the torus of gas and dust obscures our view of the accretion disk region, while for other black holes we can see the disk directly. These are known as obscured and unobscured black holes. The obscured black holes are similar to an eclipsed Sun, since the light of the accretion disk is blocked from view. Unfortunately, so is the black hole’s corona. But the corona is so hot that it emits extremely high-energy X-rays. These X-rays can scatter off material in the torus and reflect into our line of site.
Using data from NASA’s Imaging X-ray Polarimetry Explorer (IPXE), the team gathered data on a dozen obscured black holes, including Cygnus X-1 and X-3 in the Milky Way, and LMG X-1 and X-3 in the Large Magellanic Cloud. They were not only able to observe scattered X-rays from the coronas of these black holes, they were also able to detect a pattern among them. Based on the data, the corona surrounds the black hole in a disk similar to the accretion disk, rather than surrounding the black hole in a sphere similar to the Sun’s corona.
Research such as this will help astronomers refine our models of black holes. It will also help us better understand how black holes consume matter and power the AGNs we observe in distant galaxies.
Reference: Saade, M. Lynne, et al. “A Comparison of the X-Ray Polarimetric Properties of Stellar and Supermassive Black Holes.” The Astrophysical Journal 974.1 (2024): 101.
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Despite the fact that our universe is old, cold, and well past its prime, it’s not done making new galaxies yet.
Galaxy formation first got started when our universe was only a few hundred million years old. In those dark ages the first stars gathered enough material to trigger nuclear fusion and ignite. Slowly over time those clumps of stars found each other and began to build the first young protogalaxies.
Over time those protogalaxies accumulated more material and merged together to quickly grow to become the massive galaxies that sprinkle throughout the universe today.
But galaxies are more than clumps of stars and gas. They are also deep wells of dark matter, which is the invisible substance that makes up the most of the mass of every object in the universe. To make a galaxy you really start with an accumulation of dark matter. That forms the gravitational bedrock for normal matter to gather onto and start forming stars.
The accumulation of dark matter really only happened in the very early universe, and long ago shut off. But those concentrations of dark matter remain today. Evidence from simulations and observations tells us that normal matter is still finding those pockets and triggering fresh rounds of star formation. That means while the seeds of galaxies were only laid down once, new accumulations of matter are still lighting up in the present day cosmos.
It is true that we are well past the peak of star formation and the heyday of galaxy assembly. That epoch came and went over 10 billion years ago. And far into the future our universe will expand so much that this process will slow down and eventually stop. But the universe isn’t done yet. For now, we can still enjoy a universe full of galaxies and knowing that new ones are still coming on the scene.
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The New Zealand Astrophotography Competition showcases and recognizes some of the most stunning images of the southern hemisphere’s night sky. This year, photographers from across New Zealand have captured some incredibly breathtaking skyscapes such as amazing auroras, stunning images of our Solar System, and deep-sky marvels.
Universe Today was proud to be part of this year’s competition, as our own Fraser Cain was one of the judges.
The overall winner in the competition is a gorgeous view of the Aurora Australis, above, by photographer Tom Rae. Rae said he captured this image during the “once in a lifetime” geomagnetic storm in May of 2024, showing the Milky Way arching over the dramatic landscape of Aoraki Mount Cook National Park. This image also won the “Aurora” category.
The other categories in the competition include Deep Sky, Solar System, Dark-Sky Places, Timelapse, and new this year are Smartphone Images and a People’s Choice Award, chosen by the public.
There’s also a Nightscape category, and the winner –again — for this category is Tom Rae, showing the bowed Milky Way over a sharp ridge in Aoraki Mount Cook National Park.
“The Ridge” by Tom Rae, winner of the Artistic/Nightscape category of the 2024 New Zealand Astrophotography Competition. Credit and copyright: Tom Rae.“This image is one of my biggest astrophotography accomplishments to date,” Rae explained on NZ Astrophotography Competition website, “and the largest panorama I’ve ever captured, with the full resolution image containing over a billion pixels from 62 images stitched together.”
Deep Sky “First Amateur Detection of Light Echoes from 19th-Century Great Eruption of Eta Carinae” by Rolf Wahl Olsen in the Deep Sky category of the 2024 New Zealand Astrophotography Competition. Credit and copyright: Rolf Wahl Olsen.NZ astrophotographer Rolf Wahl Olsen is no stranger to Universe Today readers, as we’ve featured several of his photos for years. Olsen outdid himself with this deep sky photo of Eta Carinae.
“This is the first amateur image of light echoes from the 19th-century Great Eruption of Eta Carinae,” Olsen explained. “These light echoes have been detected by the Hubble Space Telescope and from large observatories such as the CTIO 4m telescope, but this is the first time that amateur images reveal these transient features.
Olson said his other first amateur detection of light echoes from supernova SN1987a inspired an attempt to try looking for the fainter echoes near Eta Carinae. You can read more about this effort on the NZ Astrophotography website and also at Olsen’s website.
Solar System “Solar Fury” by Navaneeth Unnikrishnan won the Solar System Category of the 2024 New Zealand Astrophotgraphy Competition. Credit and copyright: Navaneeth Unnikrishnan.Navaneeth Unnikrishnan captured this stunning view of the full disk of the Sun. Using an H-alpha filter reveals the Sun’s dynamic surface and massive prominences. “A reminder of the incredible power and beauty just beyond our skies,” said Unnikrishnan.
Dark Sky “Endurance” by Abby Keith won the Dark Sky Places category of the 2024 New Zealand Astrophotgraphy Competition. Credit and copyright: Abby Keith.Abby Keith captured this stunning dark sky photo while on a five-day hike in New Zealand’s in Fiordland National Park. The view shows Lake Mackenzie, a sub-alpine lake on the Routeburn Track, which is one of New Zealand’s Great Walks.
This panoramic image consists of 16 images for the foreground and 38 images for the sky.
“This image is the hardest one I’ve had to work for,” Keith explained. Carrying a 20-plus kg pack was worth it, however, as there were perfect conditions to capture this view.
Smartphone “Lake Aviemore aurora” by Ian Griffin won the Smartphone category in the 2024 New Zealand Astrophotgraphy Competition. Credit and copyright: Iam Griffin.This image was was also taken during the famous geomagnetic storm of May 12, 2024. Griffin called it “one of the most epic auroral storms I have ever seen. As my main digital cameras snapped away, I decided to see what my Iphone could do; I was blown away by the results!”
So are we! For more great astrophotos, check out Griffin’s website.
People’s Choice “Father and Son Magic” by Grant Birley won the People’s Choice Award in the 2024 New Zealand Astrophotgraphy Competition. Credit and copyright: Grant Birley.New this year for this competition is the People’s Choice Award, where after short-list winners were announced, online voting was opened for the public to choose their favorite images. This beautiful and heartfelt image is definitely worthy of being a favorite. You can see more of Birley’s images on Instagram.
TimelapseThis breathtaking timelapse shows mountains rotating against the backdrop of the stars, instead of the usual view of the stars moving. This work was submitted by Last Quarter Photography on YouTube.
You can see all the winners, runners-up and highly commended images and videos at the NZ Astrophotography Competition website.
New Zealand Astrophotography Competition This is New Zealand’s leading annual astrophotography competition and it is run jointly by the Royal Astronomy Society of New Zealand (RASNZ) and the Auckland Astronomical Society. Along with Fraser Cain, the other judges this year were Judy Schmidt — another name well-known to Universe Today readers for her imaging editing and cosmic creativity, and Dylan O’Donnell who operates the YouTube channel “Star Stuff.”
Below is a video of all the short-list entries from this year’s competition.
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