The images and our best computer models don't agree.
A trio of intriguing galaxy clusters<img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQzNDA0OS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYxNTkzNzUyOH0.0IRzkzvKsmPEHV-v1dqM1JIPhgE2W-UHx0COuB0qQnA/img.jpg?width=980" id="d69be" class="rm-shortcode" data-rm-shortcode-id="2d2664d9174369e0a06540cb3a3a9079" data-rm-shortcode-name="rebelmouse-image" />
The three galaxy clusters imaged for the study
Mapping dark matter<span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="d904b585c806752f261e1215014691a6"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/fO0jO_a9uLA?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span><p>The assumption has been that the greater the lensing effect, the higher the concentration of dark matter.</p><p>As scientists analyzed the clusters' large-scale lensing — the massive arc and elongation visual effects produced by dark matter — they noticed areas of smaller-scale lensing within that larger distortion. The scientists interpret these as concentrations of dark matter within individual galaxies inside the clusters.</p><p>The researchers used spectrographic data from the VLT to determine the mass of these smaller lenses. <a href="https://www.oas.inaf.it/en/user/pietro.bergamini/" target="_blank" rel="noopener noreferrer">Pietro Bergamini</a> of the INAF-Observatory of Astrophysics and Space Science in Bologna, Italy explains, "The speed of the stars gave us an estimate of each individual galaxy's mass, including the amount of dark matter." The leader of the spectrographic aspect of the study was <a href="http://docente.unife.it/docenti-en/piero.rosati1/curriculum?set_language=en" target="_blank">Piero Rosati</a> of the Università degli Studi di Ferrara, Italy who recalls, "the data from Hubble and the VLT provided excellent synergy. We were able to associate the galaxies with each cluster and estimate their distances." </p><p>This work allowed the team to develop a thoroughly calibrated, high-resolution map of dark matter concentrations throughout the three clusters.</p>
But the models say...<p>However, when the researchers compared their map to the concentrations of dark matter computer models predicted for galaxies bearing the same general characteristics, something was <em>way</em> off. Some small-scale areas of the map had 10 times the amount of lensing — and presumably 10 times the amount of dark matter — than the model predicted.</p><p>"The results of these analyses further demonstrate how observations and numerical simulations go hand in hand," notes one team member, <a href="https://nena12276.wixsite.com/elenarasia" target="_blank">Elena Rasia</a> of the INAF-Astronomical Observatory of Trieste, Italy. Another, <a href="http://adlibitum.oats.inaf.it/borgani/" target="_blank" rel="noopener noreferrer">Stefano Borgani</a> of the Università degli Studi di Trieste, Italy, adds that "with advanced cosmological simulations, we can match the quality of observations analyzed in our paper, permitting detailed comparisons like never before."</p><p>"We have done a lot of testing of the data in this study," Meneghetti says, "and we are sure that this mismatch indicates that some physical ingredient is missing either from the simulations or from our understanding of the nature of dark matter." <a href="https://physics.yale.edu/people/priyamvada-natarajan" target="_blank">Priyamvada Natarajan</a> of Yale University in Connecticut agrees: "There's a feature of the real Universe that we are simply not capturing in our current theoretical models."</p><p>Given that any theory in science lasts only until a better one comes along, Natarajan views the discrepancy as an opportunity, saying, "this could signal a gap in our current understanding of the nature of dark matter and its properties, as these exquisite data have permitted us to probe the detailed distribution of dark matter on the smallest scales."</p><p>At this point, it's unclear exactly what the conflict signifies. Do these smaller areas have unexpectedly high concentrations of dark matter? Or can dark matter, under certain currently unknown conditions, produce a tenfold increase in lensing beyond what we've been expecting, breaking the assumption that more lensing means more dark matter?</p><p>Obviously, the scientific community has barely begun to understand this mystery.</p>
Astronomers spot an object heading into Earth orbit.
Minimoons<p>Scientists have confirmed just two prior minimoons. One was <a href="https://en.wikipedia.org/wiki/2006_RH120" target="_blank">2006 RH120</a>, which orbited us from September 2006 to June 2007. The other was <a href="https://en.wikipedia.org/wiki/2020_CD3" target="_blank">2020 CD3</a>, which got stuck in the 2015–2016 timeframe, and is believed to gotten away in May 2020.</p><p>2020 SO, the new kid on the block, is expected to arrive in October 2020 and pop out of orbit in May 2021.</p><div id="37962" class="rm-shortcode" data-rm-shortcode-id="f4c0fc8a2cba6536ea4cd960ebed3e6e"><blockquote class="twitter-tweet twitter-custom-tweet" data-twitter-tweet-id="1307729521869611008" data-partner="rebelmouse"><div style="margin:1em 0">Asteroid 2020 SO may get captured by Earth from Oct 2020 - May 2021. Current nominal trajectory shows shows capture… https://t.co/F5utxRvN6Z</div> — Tony Dunn (@Tony Dunn)<a href="https://twitter.com/tony873004/statuses/1307729521869611008">1600621989.0</a></blockquote></div>
Identifying 2020 SO<p>The first clue 2020 SO isn't your ordinary asteroid is its exceptionally low velocity. It's traveling much more slowly that a typical asteroid — their <a href="https://www.lpi.usra.edu/exploration/training/illustrations/craterMechanics/" target="_blank">average rate of travel</a> <a href="https://www.lpi.usra.edu/exploration/training/illustrations/craterMechanics/" target="_blank" rel="noopener noreferrer"></a>is 18 kilometers (58,000 feet) per second. Even <a href="https://en.wikipedia.org/wiki/Moon_rock" target="_blank">moon rocks</a> sent careening into Earth orbit by impacts on the lunar surface outpace pokey 2020 SO.</p><p>For another thing, 2020 SO has an orbital path very similar to Earth's, lasting about one Earth year. It's also just slightly less circular than our own orbit, from which it's barely tilted off-axis.</p><p>So, what is it? <a href="https://cneos.jpl.nasa.gov/ca/" target="_blank">NASA estimates</a> that the object has dimensions very reminiscent of a discarded Centaur rocket stage from the <a href="https://en.wikipedia.org/wiki/Surveyor_2" target="_blank" rel="noopener noreferrer">Surveyor 2 mission</a> that landed an unmanned craft on the moon. Back in the day, rocket stages were jettisoned as craft were aimed toward their desired position. This stuff, if released high enough, remains in space. It appears that this Centaur rocket, launched in September 1966, is now making its way back homeward, at least for a little bit.</p><p>When 2020 SO arrives at its closest point in December, the rocket is expected to be about 50,000 kilometers from Earth. Its next closest approach is much further: 220,000 kilometers, in February 2010.</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDQzMDk3NC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYyODg1MTQ1MX0.HGknDwqp0GmeuczKY_AS7vrPG7KMFUc_XO95tNoI2xo/img.jpg?width=980" id="e5cda" class="rm-shortcode" data-rm-shortcode-id="85eb1f790d8c3ee5b261f7ba13eaa5e1" data-rm-shortcode-name="rebelmouse-image" alt="Centaur rocket stage" />
Centaur rocket stage
What we may be able to learn<p>Earthly space programs being as young as they are, scientists would love to know what's happened to our rocket during a half century in space.</p><p>While 2020 SO won't get close enough to drop into our atmosphere, its slow progress has scientists hopeful that they'll still get some kind of a decent look at it.</p><p>Spectroscopy may be able to reveal what the rocket's surface is like now — has any of its paint survived, for example? Of course, being out in space, it's likely to have been hit by lots of dust and micrometeorites, so the current state of its surfaces is also of interest. Experts are curious to know how reflective the rocket is at this point, valuable information that can help planners of future long-term missions anticipate how well a craft out in space for extended periods will remain able to reflect sunlight.</p>
Construction is nearly complete for a camera that will take 3,200-megapixel panoramas of the southern night sky.
Building a bigger focal plane<p>The tech involved in the focal plane is incredibly sophisticated and its assembly is downright harrowing.</p><p>The sensors that capture 16-megapixel images in high-end digital cameras are called <a href="https://en.wikipedia.org/wiki/Charge-coupled_device" target="_blank">charge-coupled devices</a>, or CCDs. (Our phones and tablets instead use <a href="https://lifeinlofi.com/2015/05/06/how-does-your-iphone-cmos-shutter-work/" target="_blank" rel="noopener noreferrer">CMOS</a> sensors.) The LSST camera contains 189 CCD sensors. The sensors are arranged into 21 squares of nine CCDs each — each square is called a "science raft." The 2-foot-tall, 20-pound rafts are mounted in a grid inside the camera. This all adds up to 3.2 billion pixels, each of which is tiny at 10 microns in size, about a tenth of the width of a human hair.</p><p>As you might expect, assembling such sophisticated hardware is not for the faint of heart. The rafts must be precisely positioned in the grid so that they're separated by a width equivalent to just five human hairs. If they touch they crack, and down the drain goes $3 million per raft. The SLAC team practiced the assembly operation for a year before the six-month assembly process commenced.</p><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDMwNzk5Mi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTYwNjc0ODQyNH0.JGSUxAHw3ZaqyyeO_ZeYxt0CBKTxyKqOTAB9QTE7pfo/img.jpg?width=980" id="9d15d" class="rm-shortcode" data-rm-shortcode-id="3d35e06eb183e93b8c2f549194477e23" data-rm-shortcode-name="rebelmouse-image" />
One CCD raft in place, plus a smaller non-imaging raft to its left.
Amazingly detailed images<p>The camera will be worth the effort.</p><p>The flatness of its giant focal plane — over 2 feet wide, as opposed to 1.4 inches in a consumer camera — will allow it to capture images of the heavens about 40 moons across. Zoomed in, the team says an image it produces will be so clear it will be like seeing a golf ball from 15 miles away. The camera will also be highly sensitive to dim objects, so it will be able to take pictures of things that are more than 100 million times dimmer than what we can see with our eyes — it's comparable to being able to see a candle from 1,000 miles away. Project scientists Steven Ritz sums it up: "These specifications are just astounding."</p><p>Once assembled, the focal plane was put inside a custom-built cryostat for cooling — the required operating temperature is -150° F.</p><span style="display:block;position:relative;padding-top:56.25%;" class="rm-shortcode" data-rm-shortcode-id="32a84ac359d1e08caf87ad1d1f0f8fce"><iframe type="lazy-iframe" data-runner-src="https://www.youtube.com/embed/IP3TUneJ0ho?rel=0" width="100%" height="auto" frameborder="0" scrolling="no" style="position:absolute;top:0;left:0;width:100%;height:100%;"></iframe></span>
Broccoli, say "cheese."<p>Broccoli's surface is packed with tiny details, making it a sensible candidate for testing out the focal plane. The camera housing hasn't yet been completed, so the scientists <a href="https://youtu.be/qc_iscV1uA0?t=62" target="_blank">created a pinhole device</a> that projected the broccoli's image onto the focal plane.</p><p>The man in charge of assembling and testing the LSST focal plane is Aaron Roodman, who says that "taking these images is a major accomplishment. With the tight specifications we really pushed the limits of what's possible to take advantage of every square millimeter of the focal plane and maximize the science we can do with it." </p><a href="https://www.slac.stanford.edu/~tonyj/osd/public/romanesco.html" ><img type="lazy-image" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDMwODA5MS9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY1MDEwNTEyNX0.nszfZqSEKmPZabqaYBziJOQetJ6VAowQ7678QB4G6a0/img.jpg?width=980" id="0c7cc" class="rm-shortcode" data-rm-shortcode-id="dc13ce1e827f4380684bb21aa006d47c" data-rm-shortcode-name="rebelmouse-image" alt="broccoli image captured by LSST camera" /></a>
(Click image to explore the image at full resolution.)
It's the largest black hole merger ever observed by scientists.
- In 2019, scientists detected gravitational waves that were later determined to come from the merging of two so-called "intermediate-mass" black holes.
- These black holes were thought to exist, but had never been directly observed.
- The discovery sheds new light on how black holes form.
Intermediate-mass black holes<p>Scientists know relatively little about these mid-sized black holes. They've catalogued small black holes only a few times more massive than the Sun, as well as supermassive black holes more than six billion times the mass of our star. But direct evidence of intermediate-mass black holes has remained elusive.</p><p style="margin-left: 20px;">"Long have we searched for an intermediate-mass black hole to bridge the gap between stellar-mass and supermassive black holes," Christopher Berry, a professor at Northwestern University's Center for Interdisciplinary Exploration and Research in Astrophysics), <a href="https://news.northwestern.edu/stories/2020/09/scientists-detect-first-of-its-kind-intermediate-mass-black-hole-gravitational-waves/" target="_blank">told</a> Northwestern Now. "Now, we have proof that intermediate-mass black holes do exist."</p><p>Still, how these middleweight black holes form is a mystery. Scientists know that smaller black holes form when stars explode in violent events called supernovas. But mid-sized black holes couldn't form this way, according to current physics, because stars of a certain mass range undergo a death process called pair instability, where they explode and leave nothing behind, not even a black hole.</p>
This chart compares the mass of black-hole merger events observed by LIGO-Virgo.
Visualization of a black hole.
Credit: NASA<p>The recent discovery sheds light on how black holes form, but questions still remain. Scientists with the LIGO-Virgo collaboration hope to continue studying the newly discovered intermediate black hole — dubbed GW190521 — in 2021 when the facilities will be up and running again with improved instruments.</p><p style="margin-left: 20px;">"Our ability to find a black hole a few hundred kilometers-wide from half-way across the Universe is one of the most striking realizations of this discovery," Karan Jani, an astrophysicist with LIGO <a href="https://themalaysianreserve.com/2020/09/04/mysterious-intermediate-mass-black-hole-found/" target="_blank">told</a> The Malaysian Reserve.</p><p>The discovery was described in two papers published in the<a href="https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.125.101102" target="_blank" rel="noopener noreferrer"> Physical Review Letters</a> and <a href="https://iopscience.iop.org/article/10.3847/2041-8213/aba493" target="_blank" rel="noopener noreferrer">The Astrophysical Journal Letters</a>.</p>
Astronomer Michelle Thaller schools us on what atoms really look, the Big Bang theory, and the speed of light.
- Most people have seen atoms illustrated in textbooks and know about the Big Bang and the speed of light, but there is a good chance what you think you know is not scientifically accurate.
- Michelle Thaller, an astronomer and Assistant Director for Science Communication at NASA, is here to clear up the misconceptions and explain why atoms don't actually look that way, why the Big Bang is a misnomer, and why the speed of light is more than just really fast.
- Is there an edge of space? Does light experience time? Watch this video for answers to those and other interesting questions.