First Interstellar Comet to Enter Our Solar System Dec. 7-8
Posted 02 December 2019 - 06:17 AM
“It’s humbling to realize how small Earth is next to this visitor from another solar system.
— P. van Dokkum, Ph.D., Professor of Astronomy, Yale University
This visitor came from interstellar space along a hyperbolic trajectory. It is only the second known intruder to zoom through our Solar System (the interstellar object ‘Oumuamua was detected in 2017).
As the graphic shows, the comet’s straight path across interstellar space is slightly deflected by the gravitational pull of our Sun. The comet is travelling so fast, at over 155 000 kilometres per hour, it will eventually leave the Solar System.
The panel on the right shows the comet’s position relative to Earth when the NASA/ESA Hubble Space Telescope observed it on 12 October 2019, when it was 420 million kilometres from Earth.
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Yale astronomers in Hawaii at the W. M. Keck Observatory have captured a new image below of 21/Borisov, the second interstellar object and first interstellar comet to enter our solar system. The first interstellar object was Oumuamua, which astronomers at the University of Hawaii Institute for Astronomy spotted in 2017 using the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS1) telescope at Haleakala on Maui. There is controversy about what exactly Oumuamua was.
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Astronomers report that this first interstellar comet formed in a solar system beyond ours and was ejected into interstellar space when there was a near-collision with a planet in its original solar system. The comet is following a hyperbolic path around the Sun, and currently is speeding at an extraordinary speed of 110,000 miles per hour. David Jewitt, Ph.D., at the University of California, Los Angeles (UCLA), is leader of the Hubble Space Telescope team who is also observing and photographing the interstellar comet. Prof. Jewitt says, “It’s traveling so fast it almost doesn’t care that the Sun is there.”
Artist's Comparison of Size with Earth
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Posted 02 December 2019 - 06:44 AM
What sets C/2019 Q4 apart from nearly every other comet is the eccentricity of its orbit. Eccentricity measures how much an orbit deviates from a perfect circle, which has an eccentricity of 0. Elliptical orbits, typical of planets, asteroids and comets, have eccentricities between 0 and 1. Parabolas are equal to 1, and an eccentricity greater than 1 indicates a hyperbolic orbit.
If this result holds up, astronomers have an unprecedented opportunity to study a potentially interstellar object in great detail over a long span of time. Based on the comet's current magnitude (~18) and distance from the Sun (2.7 a.u.), it appears to be a fairly large object — perhaps 10 km or more across, depending on the reflectivity of its surface.
Whether it becomes visible in amateur telescopes is unknown at this point, but it may become bright enough for astrophotographers to capture. We'll have updates as additional observations and photos arrive. For predicted positions and current orbital element, check out the Minor Planet Center's latest circular MPEC 2019-R106.
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