Astronomers make first clear detection of a moon-forming disc around an exoplanet
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The Great Dimming of Betelgeuse explained in new research
June 16, 2021 — When Betelgeuse, a bright orange star in the constellation of Orion, became visibly darker in late 2019 and early 2020, the astronomy community was puzzled. A team of astronomers have now published new images of the star’s surface, taken using the European Southern Observatory’s Very Large Telescope (ESO’s VLT), that clearly show how its brightness changed. The new research reveals that the star was partially concealed by a cloud of dust, a discovery that solves the mystery of the “Great Dimming” of Betelgeuse.
Betelgeuse’s dip in brightness — a change noticeable even to the naked eye — led Miguel Montargès and his team to point ESO’s VLT towards the star in late 2019. An image from December 2019, when compared to an earlier image taken in January of the same year, showed that the stellar surface was significantly darker, especially in the southern region. But the astronomers weren’t sure why.
The team continued observing the star during its Great Dimming, capturing two other never-before-seen images in January 2020 and March 2020. By April 2020, the star had returned to its normal brightness.
“For once, we were seeing the appearance of a star changing in real time on a scale of weeks,” says Montargès, from the Observatoire de Paris, France, and KU Leuven, Belgium. The images now published are the only ones we have that show Betelgeuse’s surface changing in brightness over time.
In their new study, published today in Nature, the team revealed that the mysterious dimming was caused by a dusty veil shading the star, which in turn was the result of a drop in temperature on Betelgeuse’s stellar surface.
Betelgeuse’s surface regularly changes as giant bubbles of gas move, shrink and swell within the star. The team concludes that some time before the Great Dimming, the star ejected a large gas bubble that moved away from it. When a patch of the surface cooled down shortly after, that temperature decrease was enough for the gas to condense into solid dust.
“We have directly witnessed the formation of so-called stardust,” says Montargès, whose study provides evidence that dust formation can occur very quickly and close to a star’s surface. “The dust expelled from cool evolved stars, such as the ejection we’ve just witnessed, could go on to become the building blocks of terrestrial planets and life,” adds Emily Cannon, from KU Leuven, who was also involved in the study.
June 10 dawns with a partially eclipsed Sun
An annular eclipse of the sun will take place June 10 and it will be underway at sunrise. Unfortunately, even with clear skies we will not see the “ring of fire” that is the namesake look of this type of eclipse. In fact, no place in the United States will see the complete circle, or annulus, of Sun around Moon. So don’t feel left out.
In our area, sunrise will be at 5:55 AM (EDT) with the eclipse already at its maximum for us. The eclipse ends at 6:35 AM as Moon completes its passage across Sun.
A total eclipse of the sun takes place when Earth’s Moon, at normal orbital distances, covers the solar disk completely and blocks all but the glowing corona from view. An annular eclipse takes place when Moon is at higher points in its orbit when it passes between Earth and Sun, too distant and small to form a perfect cover, allowing a brilliant ring of our star to shine.
What we may see at dawn and diminishing thereafter, is a partial solar eclipse — looking a bit like the chomping character from the classic PAC-MAN video game. Much of the solar disk will be visible but the curved edge of Moon will take a bite out of one side.
How can you watch the eclipse? With great care!
How can you watch the eclipse? With great care! At no time during our partial solar eclipse will it be safe to watch the event without vision protection. If you have eclipse glasses from a recent solar eclipse, those should be just fine — just make sure there are no pinholes or other damage to the plastic film “lenses”! You can check for damage by holding the eclipse viewer at arm’s length and looking at a bright lightbulb. If you see any dots of light through the viewer film, throw those glasses out!
Do NOT look at the sun through sunglasses, even multiple sets of sunglasses, or photo negatives, Compact Discs, or anything other than certified eclipse viewing equipment! Pinhole and other projection techniques can be used safely since the viewer is looking at a projection and not the sun itself. Five Ways to View the Solar Eclipse
“The Sun can be viewed safely with the naked eye only during the few brief seconds or minutes of a total solar eclipse. Partial eclipses, annular eclipses, and the partial phases of total eclipses are never safe to watch without taking special precautions. Even when 99% of the Sun’s surface is obscured during the partial phases of a total eclipse, the remaining photospheric crescent is intensely bright and cannot be viewed safely without eye protection [Chou, 1981; Marsh, 1982]. Do not attempt to observe the partial or annular phases of any eclipse with the naked eye. Failure to use appropriate filtration may result in permanent eye damage or blindness!” — NASA: Eye Safety During Solar Eclipses
Total lunar eclipse? Uh, not this time.
They say timing is everything and, with eclipses, that is certainly true. Unfortunately, timing will not be in our favor for viewing the Wednesday, May 26 total lunar eclipse. Earth’s Moon will be dipping very close to the horizon as morning twilight brightens hiding the most colorful portion of the event — totality — when Moon turns shades of copper and red. The subtle penumbral eclipse as Moon enters Earth’s outer shadow and will likely be even harder to see than usual. The partial phase of the eclipse begins as Moon enters the dark inner portion of the shadow cone and is easily spotted under other circumstances. Even the partial eclipse begins so late with Moon so close to the horizon that only a lucky few Ohioans will see any part of it.
| Penumbral Eclipse begins | May 26 at 4:47 a.m. |
| Partial Eclipse begins | May 26 at 5:45 a.m. |
| Total Eclipse begins | May 26 at 7:11 a.m. |
| Maximum Eclipse | May 26 at 7:18 a.m. |
The good news? Lunar eclipses can occur only at the time of a Full Moon and this event features a perigee Moon — our natural satellite at a particularly low portion of its orbit around Earth — appearing just a bit bigger and brighter than average. “Low”, in this case means 221,880 miles out. So, if skies allow, get out and enjoy the big, brilliant Full Moon tonight — it’s a natural wonder in its own right.
Still want to watch the eclipse, even though we can’t see it from here? Just do an online search for live eclipse viewing opportunities or tune in to your favorite morning TV news show; they’ll be broadcasting from the West Coast or Hawaii where the eclipse can be properly seen!
Don’t despair, dear moonwatcher! Come this November 19, in the wee hours of the morning, we will be in an excellent position to see a nearly total lunar eclipse from our own backyards! More on that at a later time!
Happy “birthday” Hubble Space Telescope! We get the gift.
The giant star featured in this latest Hubble Space Telescope anniversary image is waging a tug-of-war between gravity and radiation to avoid self-destruction. The star, called AG Carinae, is surrounded by an expanding shell of gas and dust — a nebula — that is shaped by the powerful winds of the star. The nebula is about five light-years wide, which equals the distance from here to our nearest star (beyond our own Sun), Alpha Centauri.
The huge structure was created from one or more giant eruptions several thousand years ago. The star’s outer layers were blown into space, the expelled material amounting to roughly 10 times the mass of our Sun. These outbursts are typical in the life of a rare breed of star called a Luminous Blue Variable (LBV), a brief unstable phase in the short life of an ultra-bright, glamorous star that lives fast and dies young. These stars are among the most massive and brightest stars known. They live for only a few million years, compared to the roughly 10-billion-year lifetime of our own Sun. AG Carinae is a few million years old and resides 20 000 light-years away inside our Milky Way galaxy. The star’s expected lifetime is between 5 million and 6 million years.
LBVs have a dual personality. They appear to spend years in semi-quiescent bliss and then they erupt in a petulant outburst, during which their luminosity increases — sometimes by several orders of magnitude. These behemoths are stars in the extreme, far different from normal stars like our Sun. In fact AG Carinae is estimated to be up to 70 times more massive than our Sun and shines with the blinding brilliance of 1 million suns.
First flight on another planet takes a little Ingenuity
For more on the Ingenuity Mars Helicopter technology demonstration, click here!
Ingenuity Mars helicopter to take flight soon
Credits: NASA/JPL-Caltech/ASU
UPDATE: Based on data from the Ingenuity Mars helicopter that arrived late Friday night, NASA has chosen to reschedule the Ingenuity Mars Helicopter’s first experimental flight to no earlier than April 14. CLICK HERE for the full story.
A livestream confirming Ingenuity’s first flight is targeted to begin around 3:30 a.m. EDT Monday, April 12, on NASA Television, the NASA app, and the agency’s website, and will livestream on multiple agency social media platforms, including the JPL YouTube and Facebook channels. When it happens it will be the first flight of an aircraft operated on another planet.
New: A view of the M87 supermassive black hole in polarized light
March 24 — The Event Horizon Telescope (EHT) collaboration, who produced the first ever image of a black hole, has today revealed a new view of the massive object at the center of the Messier 87 (M87) galaxy: how it looks in polarized light. This is the first time astronomers have been able to measure polarization, a signature of magnetic fields, this close to the edge of a black hole. The observations are key to explaining how the M87 galaxy, located 55 million light-years away, is able to launch energetic jets from its core.
“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy,” says Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University in the Netherlands.
On 10 April 2019, scientists released the first ever image of a black hole, revealing a bright ring-like structure with a dark central region — the black hole’s shadow. Since then, the EHT collaboration has delved deeper into the data on the supermassive object at the heart of the M87 galaxy collected in 2017. They have discovered that a significant fraction of the light around the M87 black hole is polarized.
“This work is a major milestone: the polarization of light carries information that allows us to better understand the physics behind the image we saw in April 2019, which was not possible before,” explains Iván Martí-Vidal, also Coordinator of the EHT Polarimetry Working Group and GenT Distinguished Researcher at the University of Valencia, Spain. He adds that “unveiling this new polarized-light image required years of work due to the complex techniques involved in obtaining and analyzing the data.”
Light becomes polarized when it goes through certain filters, like the lenses of polarized sunglasses, or when it is emitted in hot regions of space where magnetic fields are present. In the same way that polarized sunglasses help us see better by reducing reflections and glare from bright surfaces, astronomers can sharpen their view of the region around the black hole by looking at how the light originating from it is polarized. Specifically, polarization allows astronomers to map the magnetic field lines present at the inner edge of the black hole.
“The newly published polarized images are key to understanding how the magnetic field allows the black hole to ‘eat’ matter and launch powerful jets,” says EHT collaboration member Andrew Chael, a NASA Hubble Fellow at the Princeton Center for Theoretical Science and the Princeton Gravity Initiative in the US.
The bright jets of energy and matter that emerge from M87’s core and extend at least 5000 light-years from its center are one of the galaxy’s most mysterious and energetic features. Most matter lying close to the edge of a black hole falls in. However, some of the surrounding particles escape moments before capture and are blown far out into space in the form of jets.
Astronomers have relied on different models of how matter behaves near the black hole to better understand this process. But they still don’t know exactly how jets larger than the galaxy are launched from its central region, which is comparable in size to the Solar System, nor how exactly matter falls into the black hole. With the new EHT image of the black hole and its shadow in polarized light, astronomers managed for the first time to look into the region just outside the black hole where this interplay between matter flowing in and being ejected out is happening.
The observations provide new information about the structure of the magnetic fields just outside the black hole. The team found that only theoretical models featuring strongly magnetized gas can explain what they are seeing at the event horizon.
“The observations suggest that the magnetic fields at the black hole’s edge are strong enough to push back on the hot gas and help it resist gravity’s pull. Only the gas that slips through the field can spiral inwards to the event horizon,” explains Jason Dexter, Assistant Professor at the University of Colorado Boulder, US, and Coordinator of the EHT Theory Working Group.
To observe the heart of the M87 galaxy, the collaboration linked eight telescopes around the world — including the northern Chile-based Atacama Large Millimeter/submillimeter Array (ALMA) and the Atacama Pathfinder EXperiment (APEX), in which the European Southern Observatory (ESO) is a partner — to create a virtual Earth-sized telescope, the EHT. The impressive resolution obtained with the EHT is equivalent to that needed to measure the length of a credit card on the surface of the Moon.
“With ALMA and APEX, which through their southern location enhance the image quality by adding geographical spread to the EHT network, European scientists were able to play a central role in the research,” says Ciska Kemper, European ALMA Program Scientist at ESO. “With its 66 antennas, ALMA dominates the overall signal collection in polarized light, while APEX has been essential for the calibration of the image.”
“ALMA data were also crucial to calibrate, image and interpret the EHT observations, providing tight constraints on the theoretical models that explain how matter behaves near the black hole event horizon,” adds Ciriaco Goddi, a scientist at Radboud University and Leiden Observatory, the Netherlands, who led an accompanying study that relied only on ALMA observations.
The EHT setup allowed the team to directly observe the black hole shadow and the ring of light around it, with the new polarized-light image clearly showing that the ring is magnetized. The results are published today in two separate papers in The Astrophysical Journal Letters by the EHT collaboration. The research involved over 300 researchers from multiple organizations and universities worldwide.
“The EHT is making rapid advancements, with technological upgrades being done to the network and new observatories being added. We expect future EHT observations to reveal more accurately the magnetic field structure around the black hole and to tell us more about the physics of the hot gas in this region,” concludes EHT collaboration member Jongho Park, an East Asian Core Observatories Association Fellow at the Academia Sinica Institute of Astronomy and Astrophysics in Taipei.
It moves!
NASA HQ building named for Mary W. Jackson, of “Hidden Figures” fame
NASA Administrator Jim Bridenstine announced Wednesday the agency’s headquarters building in Washington, D.C., will be named after Mary W. Jackson, the first African American female engineer at NASA.
Jackson started her NASA career in the segregated West Area Computing Unit of the agency’s Langley Research Center in Hampton, Virginia. Jackson, a mathematician and aerospace engineer, went on to lead programs influencing the hiring and promotion of women in NASA’s science, technology, engineering, and mathematics careers. In 2019, she was posthumously awarded the Congressional Gold Medal.
“Mary W. Jackson was part of a group of very important women who helped NASA succeed in getting American astronauts into space. Mary never accepted the status quo, she helped break barriers and open opportunities for African Americans and women in the field of engineering and technology,” said Bridenstine. “Today, we proudly announce the Mary W. Jackson NASA Headquarters building. It appropriately sits on ‘Hidden Figures Way,’ a reminder that Mary is one of many incredible and talented professionals in NASA’s history who contributed to this agency’s success. Hidden no more, we will continue to recognize the contributions of women, African Americans, and people of all backgrounds who have made NASA’s successful history of exploration possible.”
The work of the West Area Computing Unit caught widespread national attention in the 2016 Margot Lee Shetterly book “Hidden Figures: The American Dream and the Untold Story of the Black Women Mathematicians Who Helped Win the Space Race.” The book was made into a popular movie that same year and Jackson’s character was played by award-winning actress Janelle Monáe.
“We are honored that NASA continues to celebrate the legacy of our mother and grandmother Mary W. Jackson,” said, Carolyn Lewis, Mary’s daughter. “She was a scientist, humanitarian, wife, mother, and trailblazer who paved the way for thousands of others to succeed, not only at NASA, but throughout this nation.”
Stephens Memorial Observatory 