The newly discovered galaxies are 62 times bigger than the Milky Way.
- Two recently discovered radio galaxies are among the largest objects in the cosmos.
- The discovery implies that radio galaxies are more common than previously thought.
- The discovery was made while creating a radio map of the sky with a small part of a new radio array.
An extremely active galaxy<p> <br> </p><p>Radio galaxies are galaxies with extremely active central regions, known as nuclei, which shine incredibly brightly in some part of the electromagnetic spectrum. They are known for emitting large jets of ionized matter into intergalactic space at speeds approaching that of light. They are related to quasars and blazars. It is thought that supermassive black holes are the energy source that make these galaxies shine so brightly. </p><p>What makes these two galaxies (known as MGTC J095959.63+024608.6 and MGTC J100016.84+015133.0) so interesting is their size. Only 831 similar, "giant radio galaxies" are known to exist. As study co-author Dr. Matthew Prescott explains, these are particularly large even for <a href="https://www.forbes.com/sites/jamiecartereurope/2021/01/18/we-just-found-two-mysterious-galaxies-62-times-bigger-than-our-milky-way-say-scientists/?sh=76edf29c2892" target="_blank" rel="noopener noreferrer">giants</a>:</p><p>"These two galaxies are special because they are amongst the largest giants known, and in the top 10 percent of all giant radio galaxies. They are more than two mega-parsecs across, which is around 6.5 million light-years or about 62 times the size of the Milky Way. Yet they are fainter than others of the same size."</p><p>The smaller of the two is just over two megaparsecs across, roughly six and a half million light-years. The larger is almost another half megaparsec larger than <a href="http://www.sci-news.com/astronomy/giant-radio-galaxies-09266.html" target="_blank">that</a>. <br></p><p>Exactly how these things get to be so massive remains a mystery. Some have proposed that they are ejecting matter into unusually empty space, allowing for the jet to expand further, though some evidence contradicts this. The most commonly suggested idea is that they are simply much, much older than the previously observed radio galaxies, allowing more time for expansion to occur.</p>
How does this change our understanding of the universe?<p> While exciting and impressive on their own, the findings also suggest that there are very many more of these giant galaxies than previously supposed. If you were going off the previous estimates for how typical these galaxies are, then the odds of finding these two would be 1 in 2.7×10<sup>6. </sup>This suggests that there must be more, given that the alternative is that the scientists were impossibly lucky. </p><p> In the study, the researchers also apply this reasoning to smaller versions of these galaxies, saying:</p><p> "While our analysis has considered only enormous (>2 Mpc) objects, if radio galaxies must grow to reach this size, then we may expect to similarly uncover in our data previously undetected GRGs with smaller sizes."</p><p> Exactly how common radio galaxies and turn out to be remains to be seen. Still, it will undoubtedly be an exciting time for radio astronomy as new telescopes are turned skywards to search for them.</p>
How did they find them?<iframe width="730" height="430" src="https://www.youtube.com/embed/c1ZW3nVfe5A" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe><p> The new galaxies were discovered by the amusingly named <a href="https://www.sarao.ac.za/gallery/meerkat/" target="_blank" rel="noopener noreferrer">MeerKAT</a> radio telescope in South Africa during the creation of a new radio map of the sky. The MeerKAT is the first of what will soon be the <a href="https://en.wikipedia.org/wiki/Square_Kilometre_Array" target="_blank" rel="noopener noreferrer">Square Kilometre Array</a> of telescopes, which will span several countries in the southern hemisphere and make even more impressive discoveries in radio astronomy possible. </p>
Planets can emit radio waves. For the first time, we've picked them up from outside the solar system.
- An international team of scientists have picked up the first radio waves emitted by an exoplanet.
- The planet is a "Hot Jupiter" orbiting a star system 40 light years from Earth.
- The findings must be confirmed, but if they are, it will be a first in radio astronomy.
It's not little green men, but it's a start.<iframe width="730" height="430" src="https://www.youtube.com/embed/dXOLJOnLKDg" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe><p> Science has known for a while that planets emit radio emissions. Jupiter does it all the time due to the interaction of various kinds of radiation with its magnetic <a href="https://en.wikipedia.org/wiki/Jupiter#Radiotelescope_research" target="_blank" rel="noopener noreferrer">field</a>. Previous studies achieved a fair understanding of what these emissions look like. </p><p>In this study, the authors used an estimate of what Jupiter's emissions would look like if they were much further away to determine if the radio emissions coming from the <a href="https://en.wikipedia.org/wiki/Tau_Bo%C3%B6tis" target="_blank" rel="noopener noreferrer">Tau Boötis</a> system matched what would be expected if the system had a gas giant of its own closely orbiting its sun, commonly known as a "Hot Jupiter." The existence of a planet in that system has been known for some <a href="https://en.wikipedia.org/wiki/Tau_Bo%C3%B6tis_b" target="_blank" rel="noopener noreferrer">time</a>.</p><p> The study utilized a top of the line, decentralized radio telescope network to collect these findings. The Low-Frequency Array (LOFAR) is centered in the Netherlands and operated by the Netherlands Institute for Radio Astronomy. While the network includes telescopes all over Europe, this study only used the core group of telescopes. </p><p>After reviewing the massive collection of radio images, the subtle signs of a gas giant orbiting another star began to appear. Lead author Dr. <a href="https://sites.google.com/site/astrojaketurner/" target="_blank" rel="noopener noreferrer">Jake D. Turner</a>, a postdoctoral researcher at Cornell University, explained <a href="https://news.cornell.edu/stories/2020/12/cornell-postdoc-detects-possible-exoplanet-radio-emission" target="_blank">the findings</a>:</p><p> "We present one of the first hints of detecting an exoplanet in the radio realm. The signal is from the Tau Boötes system, which contains a binary star and an exoplanet. We make the case for an emission by the planet itself. From the strength and polarization of the radio signal and the planet's magnetic field, it is compatible with theoretical predictions."</p><p>While the idea of looking for exoplanets with radio telescopes isn't new, this is the first time that researchers have picked up signals from an exoplanet. This is no small feat, and several other astronomers have expressed their excitement. </p><p>Study co-author <a href="https://astro.cornell.edu/ray-jayawardhana" target="_blank" rel="noopener noreferrer">Ray Jayawardhana</a> explained that the findings could open up an entirely new area of space <a href="https://news.cornell.edu/stories/2020/12/cornell-postdoc-detects-possible-exoplanet-radio-emission" target="_blank" rel="noopener noreferrer">exploration</a>:</p><p> "If confirmed through follow-up observations this radio detection opens up a new window on exoplanets, giving us a novel way to examine alien worlds that are tens of light-years away."</p><p>The study involved more than 100 hours of searching for radio signals in star systems up to 100 light-years away. The expected signals were only seen in Tau Boötes. The detected signal is relatively weak, and it remains possible that it wasn't from the exoplanet. Further research will focus on confirming the findings.</p><p>Dr. Turner also expressed his desire to continue searching for other exoplanets using a larger proportion of the telescopes in the LOFAR. </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.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNDMwNzk5Mi9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2OTgyMDQyNH0.jl7J1c0ekAWOQAaeyCNWHtUmYqD1kAoz7clAgpBCBaE/img.jpg?width=980" id="a7993" class="rm-shortcode" data-rm-shortcode-id="3d35e06eb183e93b8c2f549194477e23" data-rm-shortcode-name="rebelmouse-image" data-width="1440" data-height="960" />
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" data-width="2466" data-height="2472" /></a>
(Click image to explore the image at full resolution.)
A gigantic star makes off during an eight-year gap in observations.
- The massive star in the Kinsman Dwarf Galaxy seems to have disappeared between 2011 and 2019.
- It's likely that it erupted, but could it have collapsed into a black hole without a supernova?
- Maybe it's still there, but much less luminous and/or covered by dust.
A "very massive star" in the Kinman Dwarf galaxy caught the attention of astronomers in the early years of the 2000s: It seemed to be reaching a late-ish chapter in its life story and offered a rare chance to observe the death of a large star in a region low in metallicity. However, by the time scientists had the chance to turn the European Southern Observatory's (ESO) Very Large Telescope (VLT) in Paranal, Chile back around to it in 2019 — it's not a slow-turner, just an in-demand device — it was utterly gone without a trace. But how?
The two leading theories about what happened are that either it's still there, still erupting its way through its death throes, with less luminosity and perhaps obscured by dust, or it just up and collapsed into a black hole without going through a supernova stage. "If true, this would be the first direct detection of such a monster star ending its life in this manner," says Andrew Allan of Trinity College Dublin, Ireland, leader of the observation team whose study is published in Monthly Notices of the Royal Astronomical Society.
Between astronomers' last look in 2011 and 2019 is a large enough interval of time for something to happen. Not that 2001 (when it was first observed) or 2019 have much meaning, since we're always watching the past out there and the Kinman Dwarf Galaxy is 75 million light years away. We often think of cosmic events as slow-moving phenomena because so often their follow-on effects are massive and unfold to us over time. But things happen just as fast big as small. The number of things that happened in the first 10 millionth of a trillionth of a trillionth of a trillionth of a second after the Big Bang, for example, is insane.
In any event, the Kinsman Dwarf Galaxy, or PHL 293B, is far way, too far for astronomers to directly observe its stars. Their presence can be inferred from spectroscopic signatures — specifically, PHL 293B between 2001 and 2011 consistently featured strong signatures of hydrogen that indicated the presence of a massive "luminous blue variable" (LBV) star about 2.5 times more brilliant than our Sun. Astronomers suspect that some very large stars may spend their final years as LBVs.
Though LBVs are known to experience radical shifts in spectra and brightness, they reliably leave specific traces that help confirm their ongoing presence. In 2019 the hydrogen signatures, and such traces, were gone. Allan says, "It would be highly unusual for such a massive star to disappear without producing a bright supernova explosion."
The Kinsman Dwarf Galaxy, or PHL 293B, is one of the most metal-poor galaxies known. Explosive, massive, Wolf-Rayet stars are seldom seen in such environments — NASA refers to such stars as those that "live fast, die hard." Red supergiants are also rare to low Z environments. The now-missing star was looked to as a rare opportunity to observe a massive star's late stages in such an environment.
In August 2019, the team pointed the four eight-meter telescopes of ESO's ESPRESSO array simultaneously toward the LBV's former location: nothing. They also gave the VLT's X-shooter instrument a shot a few months later: also nothing.
Still pursuing the missing star, the scientists acquired access to older data for comparison to what they already felt they knew. "The ESO Science Archive Facility enabled us to find and use data of the same object obtained in 2002 and 2009," says Andrea Mehner, an ESO staff member who worked on the study. "The comparison of the 2002 high-resolution UVES spectra with our observations obtained in 2019 with ESO's newest high-resolution spectrograph ESPRESSO was especially revealing, from both an astronomical and an instrumentation point of view."
Examination of this data suggested that the LBV may have indeed been winding up to a grand final sometime after 2011.
Team member Jose Groh, also of Trinity College, says "We may have detected one of the most massive stars of the local Universe going gently into the night. Our discovery would not have been made without using the powerful ESO 8-meter telescopes, their unique instrumentation, and the prompt access to those capabilities following the recent agreement of Ireland to join ESO."
Combining the 2019 data with contemporaneous Hubble Space Telescope (HST) imagery leaves the authors of the reports with the sense that "the LBV was in an eruptive state at least between 2001 and 2011, which then ended, and may have been followed by a collapse into a massive BH without the production of an SN. This scenario is consistent with the available HST and ground-based photometry."
A star collapsing into a black hole without a supernova would be a rare event, and that argues against the idea. The paper also notes that we may simply have missed the star's supernova during the eight-year observation gap.
LBVs are known to be highly unstable, so the star dropping to a state of less luminosity or producing a dust cover would be much more in the realm of expected behavior.
Says the paper: "A combination of a slightly reduced luminosity and a thick dusty shell could result in the star being obscured. While the lack of variability between the 2009 and 2019 near-infrared continuum from our X-shooter spectra eliminates the possibility of formation of hot dust (⪆1500 K), mid-infrared observations are necessary to rule out a slowly expanding cooler dust shell."
The authors of the report are pretty confident the star experienced a dramatic eruption after 2011. Beyond that, though:
"Based on our observations and models, we suggest that PHL 293B hosted an LBV with an eruption that ended sometime after 2011. This could have been followed by
(1) a surviving star or
(2) a collapse of the LBV to a BH [black hole] without the production of a bright SN, but possibly with a weak transient."
Astrophysicist Michelle Thaller talks ISS and why NICER is so important.
- Being outside of Earth's atmosphere while also being able to look down on the planet is both a challenge and a unique benefit for astronauts conducting important and innovative experiments aboard the International Space Station.
- NASA astrophysicist Michelle Thaller explains why one such project, known as NICER (Neutron star Interior Composition Explorer), is "one of the most amazing discoveries of the last year."
- Researchers used x-ray light data from NICER to map the surface of neutrons (the spinning remnants of dead stars 10-50 times the mass of our sun). Thaller explains how this data can be used to create a clock more accurate than any on Earth, as well as a GPS device that can be used anywhere in the galaxy.