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The Universe is filled with supermassive black holes. Almost every galaxy in the cosmos has one, and they are the most well-studied black holes by astronomers. But one thing we still don’t understand is just how they grew so massive so quickly. To answer that, astronomers have to identify lots of black holes in the early Universe, and since they are typically found in merging galaxies, that means astronomers have to identify early galaxies accurately. By hand. But thanks to the power of machine learning, that’s changing.

With the power of current and future sky surveys, the challenge of astronomy is less about capturing the right data and more about filtering out the right data from the vast trove we gather. It takes a tremendous amount of skill to distinguish a true merging galaxy from an irregular galaxy or two independent galaxies that just happen to be seen in the same patch of sky. People can be trained to do it well, but the need for skilled identifiers far surpasses the number of skilled people. One way to overcome this is to allow volunteers to fill the gap. In general, their identifications won’t be as accurate as the professionals, but a bit of statistics will allow astronomers to glean useful information.

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True positives vs false positives in machine learning identification. Credit: Avirett-Mackenzie, et al

This new study takes a different approach. Rather than having experts train volunteers, they used experts to train machine learning algorithms. That’s easier said than done. Even the most skilled expert will occasionally make mistakes, or have certain biases, and any software trained on that expert will have the same biases. So the team partnered with the Big Data Applications for Black Hole Evolution Studies (BiD4BEST), which is an EU project that provides a training network for black hole evolution data. Together they used skilled experts to identify black hole mergers in both simulated data and data from the Sloan Digital Sky Survey (SDSS). By comparing the two, the team could remove biases from the machine learning data. The result was pretty successful. When algorithm sortings were compared to simulated mergers they found it had an accuracy of well over 80%, comparable to that of the most skilled experts.

The team then used the software to identify more than 8,000 active black holes and found an interesting connection between the growth of black holes and their galaxies. It isn’t galactic mergers that trigger the growth of supermassive black holes, but large quantities of nearby cold gas. The team found that mergers only drive rapid growth when they involve the merger of star-forming galaxies rich in gas and dust. Thus, the same conditions that lead to star formation also lead to supermassive black holes. This is part of the reason why galaxies and their black holes seem to grow in parallel.

As we continue to capture astronomical data at an almost exponential rate, software will be a necessary complement to skilled observers. As this study shows, the two can be used together effectively.

Reference: Avirett-Mackenzie, M. S., et al. “A post-merger enhancement only in star-forming Type 2 Seyfert galaxies: the deep learning view.” Monthly Notices of the Royal Astronomical Society 528.4 (2024): 6915-6933.

The post Black Holes Need Refreshing Cold Gas to Keep Growing appeared first on Universe Today.

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5 Reasons You Must Backpack Idaho’s Sawtooth Mountains

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By Michael Lanza

Chances are that, by now, you’ve heard of Idaho’s Sawtooths—having typed that name into a search box may be the reason you’ve landed on this story. Maybe you’ve been intrigued at what you’ve heard or images you’ve seen from Idaho’s best-known mountain range. Perhaps you’ve even been there and the experience has only amplified your curiosity to see more of this range.

As someone who’s had the good fortune of having backpacked all over the country and in many other countries over the past three-plus decades, including the 10 years I spent as a field editor for Backpacker magazine and even longer running this blog, I rank the Sawtooths among the 10 best backpacking trips in America.

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Hi, I’m Michael Lanza, creator of The Big Outside. Click here to sign up for my FREE email newsletter. Join The Big Outside to get full access to all of my blog’s stories. Click here for my e-books to classic backpacking trips. Click here to learn how I can help you plan your next trip.

Backpackers on Trail 154 to Cramer Divide in Idaho’s Sawtooths.
” data-image-caption=”Backpackers on Trail 154 to Cramer Divide in Idaho’s Sawtooths.
” data-medium-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg?fit=200%2C300&ssl=1″ data-large-file=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg?fit=683%2C1024&ssl=1″ src=”https://i0.wp.com/tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho-683×1024.jpg?resize=683%2C1024&ssl=1″ alt=”Backpackers on Trail 154 to Cramer Divide in Idaho’s Sawtooths.” class=”wp-image-45355″ style=”width:572px;height:auto” srcset=”https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg 683w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg 200w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg 768w, https://tbo-media.sfo2.digitaloceanspaces.com/wp-content/uploads/2021/04/06230304/Saw19-024-Backpackers-on-Trail-154-to-Cramer-Divide-Sawtooth-Mountains-Idaho.jpg 800w” sizes=”(max-width: 683px) 100vw, 683px” data-recalc-dims=”1″ />Backpackers on Trail 154 to Cramer Divide in Idaho’s Sawtooths.

I’ve wandered around the Sawtooths at least a couple dozen times over more than two decades, including numerous backpacking trips, dayhikes, peak scrambles, rock climbing, and backcountry skiing. While there remain peaks on my list to climb, a few trails to hike, and many lakes to leap into (or just sit beside), the Sawtooths have become my backyard mountains. I feel at home there.

This story presents the five reasons I think every backpacker should take a multi-day hike through the Sawtooths—spotlighting the characteristics of a trip there that make this place unique. I believe this argument may persuade you to go (if, somehow, the photos don’t do it).

See my e-book “The Best Backpacking Trip in Idaho’s Sawtooth Mountains” to learn all you need to know to plan and pull off a five-day, 36-mile Sawtooths hike through the core of the Sawtooths, and my Custom Trip Planning page to learn how I can help you plan every detail of a multi-day hike there.

Please share your thoughts or experiences there in the comments section at the bottom of this story. I
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The Venerable Hubble Space Telescope Keeps Delivering

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The world was much different in 1990 when NASA astronauts removed the Hubble Space Telescope from Space Shuttle Discovery’s cargo bay and placed it into orbit. The Cold War was ending, there were only 5.3 billion humans, and the World Wide Web had just come online.

Now, the old Soviet Union is gone, replaced by a smaller but no less militaristic Russia. The human population has ballooned to 8.1 billion. The internet is a fixture in daily life. We also have a new, more powerful space telescope, the JWST.

But the Hubble keeps delivering, as this latest image shows.

The lenticular galaxy NGC 4753 is about 60 million light-years away. Lenticular galaxies are midway between elliptical and spiral galaxies. They have large-scale disks but only poorly defined spiral arms. NGC 4753 sees very little star formation because like other lenticulars, it’s used up most of its gas. The fact that they contain mostly older stars makes them similar to elliptical galaxies.

Among lenticulars, NGC 4753 is known for the dust lanes surrounding its nucleus. Astronomers think that spirals evolve into lenticulars in dense environments because they interact with other galaxies and with the intergalactic medium. However, NGC 4753 is in a low-density environment. Its environment and complex structure make it a target for astronomers to test their theories of galaxy formation and evolution.

This Hubble image is the sharpest ever taken of NGC 4753, revealing its intriguing complexity and highlighting the space telescope’s impressive resolving power.

Astronomers think that NGC 4753 is the result of a merger with a dwarf galaxy over one billion years ago. The dwarf galaxy was gas-rich, and NGC 4753's distinct dust rings probably accreted from the merger. NGC 4753's powerful gravity then shaped the gas into the complex shapes we see in this image. Image Credit: ESA/Hubble & NASA, L. Kelsey
Astronomers think that NGC 4753 is the result of a merger with a dwarf galaxy over one billion years ago. The dwarf galaxy was gas-rich, and NGC 4753’s distinct dust rings probably accreted from the merger. NGC 4753’s powerful gravity then shaped the gas into the complex shapes we see in this image. Image Credit: ESA/Hubble & NASA, L. Kelsey

NGC 4763’s unique structure results from a merger with a dwarf galaxy about 1.3 billion years ago. The video below from NOIRlab explains what happened.

NGC 4753 also hosts two known Type 1a supernovae, which are important because they help astronomers study the expansion of the Universe. They serve as standard candles, an important rung in the cosmic distance ladder.

Galaxies like NGC 4753 may not be rare, but the viewing angle plays a key role in identifying them. Our edge-on view of the galaxy makes its lenticular form clear. We could be seeing others like it from different angles that obscure its nature.

This is a model of NGC 4753, as seen from various viewing orientations. From left to right and top to bottom, the angle of the line of sight to the galaxy's equatorial plane ranges from 10° to 90° in steps of 10°. Although galaxies similar to NGC 4753 may not be rare, only certain viewing orientations allow for easy identification of a highly twisted disk. This infographic is a recreation of Figure 7 from a 1992 research paper.
This is a model of NGC
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Juno Reveals Secrets About Europa’s Icy Surface

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Europa has always held a fascination to me. I think it’s the concept of a world with a sub-surface ocean and the possibility of life that has inspired me and many others. In September 2022, NASAs Juno spacecraft made a flyby, coming within 355 kilometres of the surface. Since the encounter, scientists have been exploring the images and have identified regions where brine may have bubbled to the surface. Other images revealed possible, previously unidentified steep-walled depressions up to 50km wide, this could be caused by a free-floating ocean! 

Juno was launched to Jupiter on 5 August 2011. It took off from the Cape Canaveral site on board an Atlas V rocket and travelled around 3 billion kilometres. It arrived at Jupiter on 4 July 2016 and in September 2022 made its closest flyby of Europa. The frozen world is the second of the four Galilean satellites that were discovered by Galileo over 400 years ago. Visible in small telescopes, the true nature of the moon is only detectable by visiting craft like Juno. 

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Artist’s impression of NASA’s Galileo space probe in orbit of Jupiter. Credit: NASA

During its close fly-by, one of the onboard cameras known as Juno-Cam took the highest resolution images of the moon since Galileo took a flyby in 2000. The images supported the long held theory that the icy crusts at the north and south poles are not where they used to be. Another instrument on board, known as the Stellar Reference Unit (SRU), revealed possible activity resembling plumes where brine may have bubbled to the surface.

The ground track over Europa that was followed by Juno enabled imaging around the equatorial regions. The images revealed the usual, expected blocks of ice, walls, ridges and scarps but also found something else. Steep walled depressions that measured 20 to 50 kilometres across were also seen and they resembled large ovoid pits. 

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One of Juno’s enormous solar panels, unfurled on Earth. NASA/JPL. SWrI

The observations of the meanderings of the north/south polar ice and the varied surface features all point towards an outer icy shell that is free-floating upon the sub surface ocean. This can only happen if the outer shell is not connected to the rocky interior. When this happens, there are high levels of stress on the ice which then causes the fracture pattern witnessed. The images represent the first time such patterns have been seen in the southern hemisphere, the first evidence of true polar wandering.

The images from the SRU surprisingly provided the best quality images. It was originally designed to detect faint light from stars for navigation. Instead, the team used it to capture images when Europa was illuminated by the gentle glow of sunlight reflected from Jupiter. It was quite a novel approach and allowed complex features to become far more pronounced than before. Intricate networks of ridges criss-crossing the surface were identified along with dark stains from water plumes. One feature in particular stood out, nicknamed ‘the Platypus’, it was a 37 kilometre by 67 kilometre region shaped somewhat like a platypus.

Source : NASA’s Juno Provides High-Definition Views of Europa’s Icy Shell

The post Juno Reveals Secrets About Europa’s Icy Surface appeared first on Universe Today.

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