Look up toward the stars this month, and you just might spot the brightest comet to grace Northern Hemisphere skies in decades. In July 2020, comet NEOWISE (short for C/2020 F3 NEOWISE) has thrilled skywatchers in North America, in Europe, and in space. If you don’t spot the comet this time around, you won’t get another chance. It has a long, elliptical orbit, so it will be approximately 6,800 years before NEOWISE returns to the inner parts of the solar system.
The photo above and the time-lapse video below show NEOWISE as viewed from the International Space Station (ISS) on July 5, 2020. An astronaut shot more than 340 photos as the comet rose above the sunlit limb of Earth while the ISS passed over Uzbekistan and Central Asia.
Comet Neowise has a nucleus measuring roughly 5 kilometers (3 miles) in diameter, and its dust and ion tails stretch hundreds of thousands to millions of kilometers while pointing away from the Sun. The icy visitor was discovered on March 27, 2020, by NASA’s Near-Earth Object Wide-field Infrared Survey Explorer (NEOWISE) spacecraft as the comet was headed toward the Sun. The comet made its closest approach to the Sun on July 3, and then turned back toward the outer solar system.
Comets are made of frozen leftovers from the formation of the solar system roughly 4.6 billion years ago. The masses of dust, rock, and ice heat up when approaching the Sun; as they get closer, they spew gases and dust into a glowing head and tail. Satellite data indicate the NEOWISE has a dust tail and possibly two ionized gas tails. The comet is made visible by sunlight reflecting off of its gas emissions and dust tail.
“It’s quite rare for a comet to be bright enough that we can see it with the naked eye or even just with binoculars,” said Emily Kramer, a co-investigator of the NEOWISE satellite, in a NASA Science Live webcast. “The last time we had a comet this bright was Hale-Bopp back in 1995-1996.”
July 14, 2020
The photo above shows the comet (bottom-right) on July 14, 2020, against the backdrop of a green aurora in western Manitoba, Canada. The bright streak at the top is a meteor. The purple, ribbon-like structure is an aurora-like structure called STEVE (short for Strong Thermal Emission Velocity Enhancement), a phenomenon that was recently discovered with help from citizen scientists. Donna Lach, the photographer and an avid participant in the Aurorasaurus project, observed the scene for three hours and said the comet even out-shined the brilliant aurora at times.
NEOWISE is expected to make its closest approach to Earth on July 22, passing at a harmless distance of 103 million kilometers (64 million miles). From mid-July onward, viewers can spot the comet after sunset, below the Big Dipper in the northwest sky. For best viewing, make sure to find a spot away from city lights and with a clear view of the sky. While you may be able to see it with your naked eye, you might want to bring binoculars or a small telescope.
Astronaut photograph ISS063-E-39888 (top) was acquired on July 5th 2020, with a Nikon D5 digital camera using a 28-millimeter lens and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. The image was taken by a member of the Expedition 63 crew. Time-lapse animation by Sara Schmidt of the Earth Science and Remote Sensing group at NASA JSC. Aurora and comet photograph by Donna Lach, used with permission.
According to a new map of the Milky Way galaxy, the Solar System’s position isn’t where we thought it was. Not only is it closer to the galactic centre – and the supermassive hole therein, Sagittarius A* – it’s orbiting at a faster clip.
It’s nothing to be concerned about; we’re not actually moving closer to Sgr A*, and we’re in no danger of being slurped up. Rather, our map of the Milky Way has been adjusted, more accurately identifying where we have been all along.
And the survey beautifully demonstrates how tricky it is to map a galaxy in three dimensions from inside it.
It’s a problem that has long devilled our understanding of space phenomena. It’s relatively easy to map the two-dimensional coordinates of stars and other cosmic objects, but the distances to those objects is a lot harder to figure out.
And distances are important – they help us determine the intrinsic brightness of objects. A good recent example of this is the red giant star Betelgeuse, which turned out to be closer to Earth than previous measurements suggested. This means that it’s neither as large nor as bright as we thought.
Another is the object CK Vulpeculae, a star that exploded 350 years ago. It’s actually much farther away, which means that the explosion was brighter and more energetic, and requires a new explanation, since previous analyses were performed under the assumption it was relatively low energy.
But we’re getting better at calculating those distances, with surveys using the best available technology and techniques working hard to refine our three-dimensional maps of the Milky Way, a field known as astrometry. And one of these is the VERA radio astronomy survey, conducted by the Japanese VERA collaboration.
VERA stands for VLBI (Very Long Baseline Interferometry) Exploration of Radio Astrometry, and it uses a number of radio telescopes across the Japanese archipelago, combining their data to effectively produce the same resolution as a telescope with a 2,300 kilometre- (1,430 mile-) diameter dish. It’s the same principle behind the Event Horizon Telescope that produced our very first direct image of a black hole’s shadow.
VERA, which started observing in 2000, is designed to help us calculate the distances to radio-emitting stars by calculating their parallax. With its incredible resolution, it observes these stars for over a year, and watches how their position changes relative to stars that are much farther away as Earth orbits the Sun.
(National Astronomical Observatory of Japan)
This change in position can then be used to calculate how far a star is from Earth, but not all parallax observations are created equal. VLBI can produce much higher resolution images; VERA has a breathtaking angular resolution of 10 millionths of an arcsecond, which is expected to produce extraordinarily high precision astrometry measurements.
And this is what astronomers have used to refine our Solar System’s position in the Milky Way. Based on the first VERA Astrometry Catalog of 99 objects released earlier this year, as well as other observations, astronomers created a position and velocity map of those objects.
From this map, they calculated the position of the galactic centre.
In 1985, the International Astronomical Union defined the distance to the galactic centre as 27,700 light-years. Last year, the GRAVITY collaboration recalculated it and found it closer, just 26,673 light-years away.
(National Astronomical Observatory of Japan)
The VERA-based measurements bring it closer still, to a distance of just 25,800 light-years. And the Solar System’s orbital speed is faster, too – 227 kilometres (141 miles) per second, rather than the official velocity of 220 kilometres (137 miles) per second.
That change may not seem like much, but it could have an impact on how we measure and interpret activity in the galactic centre – ultimately, hopefully, leading to a more accurate picture of the complex interactions around Sgr A*.
Meanwhile, the VERA collaboration is forging ahead. Not only is it continuing to make observations of objects in the Milky Way, it’s joining up with an even larger project, the East Asian VLBI Network. Together, astronomers hope, the telescopes involved in this project could provide measurements of unprecedented accuracy.
Great news! It turns out scientists have discovered that we’re 2,000 light-years closer to Sagittarius A* than we thought.
This doesn’t mean we’re currently on a collision course with a black hole. No, it’s simply the result of a more accurate model of the Milky Way based on new data.
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Over the last 15 years, a Japanese radio astronomy project, VERA, has been gathering data. Using a technique called interferometry, VERA gathered data from telescopes across Japan and combined them with data from other existing projects to create what is essentially the most accurate map of the Milky Way yet.
By pinpointing the location and velocity of around 99 specific points in our galaxy, VERA has concluded that the supermassive black hole Sagittarius A, at the center of our galaxy, is actually 25,800 light-years from Earth — almost 2,000 light-years closer than what we previously believed.
In addition, the new model calculates Earth is moving faster than we believed. Older models clocked Earth’s speed at 220 kilometers (136 miles) per second, orbiting around the galaxy’s centre. VERA’s new model has us moving at 227 kilometers (141 miles) per second.
VERA is now hoping to increase the accuracy of its model by increasing the amount of points it’s gathering data from by expanding into EAVN (East Asian VLBI Network) and gathering data from a larger suite of radio telescopes located throughout Japan, Korea and China.
Researchers have effectively confirmed one of the most important theories in star physics. NBC Newsreports that a team at the Italian National Institute for Nuclear Physics has detected neutrinos traced back to star fusion for the first time. The scientists determined that the elusive particles passing through its Borexino detector stemmed from a carbon-nitrogen-oxygen (CNO) fusion process at the heart of the Sun.
This kind of behavior had been predicted in 1938, but hadn’t been verified until now despite scientists detecting neutrinos in 1956. Borexino’s design was crucial to overcoming that hurdle — its “onion-like” construction and ongoing refinements make it both ultra-sensitive and resistant to unwanted cosmic radiation.
It’s a somewhat surprising discovery, too. CNO fusion is much more common in larger, hotter stars. A smaller celestial body like the Sun only produces 1 percent of its energy through that process. This not only confirms that CNO is a driving force behind bigger stars, but the universe at large.
That, in turn, might help explain some dark matter, where neutrinos could play a significant role. Scientist Orebi Gann, who wasn’t involved in these findings, also told NBC that an asymmetry between neutrinos and their relevant antiparticles might explain why there isn’t much known antimatter in the universe. To put it another way, the findings could help answer some of the most basic questions about the cosmos.
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