Monday, 28 June 2021

Asteroid (441987) 2010 NY65 passes the Earth.

Asteroid (441987) 2010 NY65 passed by the Earth at a distance of 5 972 000 km (15.6 times the average distance between the Earth and the Moon, or 3.99% of the average distance between the Earth and the Sun), slightly before 5.10 am GMT on Friday 25 June 2021. There was no danger of the asteroid hitting us, though had it done so it would have presented a considerable threat. (441987) 2010 NY65 has an estimated equivalent diameter of 94-300 m (i.e. a spherical body with the same mass would be 99-310 m in diameter), and an towards the upper end of this range would pass through the atmosphere and directly impact the ground with a force of about 1110 megatons (about 65 300 times the explosive energy of the Hiroshima bomb), causing devastation over a wide area and creating a crater about 4.6 km across, and resulting in global climatic problems that could last for decades or even centuries.

Asteroid (441987) 2010 NY65 observed from London, England in June 2017. Northolt Branch Observatories/Facebook.

(441987) 2010 NY65 was discovered on 14 July 2010 by the NEOWISE system on the Wide-field Infrared Survey Explorer satellite. The designation 2010 NY65 implies that it was the 1649th asteroid (asteroid Y65; in numbering asteroids the letters A-Z, excluding I, are assigned numbers from 1 to 25, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 26, A2 = 51, etc., which means that Y65 = (25 x 65) + 24 = 1649) discovered in the first half of July 2010 (period 2010 N; the year being split into 24 half-months represented by the letters A-Y, with I being excluded), while the designation 441987 implies that it was 441 987th asteroid ever discovered (asteroids are not given this longer designation immediately to avoid naming double or false sightings).
The relative positions of (441987) 2010 NY65 and the Earth on 25 June 2021. JPL Small Body Database.
(441987) 2010 NY65 has a 367 day (1 year) orbital period, with an elliptical orbit tilted at an angle of 11.6° to the plain of the Solar System which takes in to 0.63 AU from the Sun (63% of the distance at which the Earth orbits the Sun and inside the orbit of the planet Venus) and out to 1.37 AU (37% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in June 2020 and the next predicted in June 2022. (441987) 2010 NY65 also has frequent close encounters with the planet Venus, with the last thought to have occurred in May 2020 and the next predicted for May 2052. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, (441987) 2010 NY65 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. As an asteroid possibly larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (441987) 2010 NY65 is also classified as a Potentially Hazardous Asteroid.
The orbit and current position of (441987) 2010 NY65. Minor Planet Centre.

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Homatula guanheensis: A new species of Stone Loach from Henan Province, China

The Stone Loach genus Homatula includes a number of small, benthic Fish, which live in the drainage basins of the Yellow, Yangtze, Pearl, Lancang, Nujiang and Red rivers. They are sometimes considered to be a part of the genus Paracobitis, which is morphologically similar, but the two are generally considered separate, due to their different distributions, with Homatula known only from China, and Paracobitis found only in western Asia. Studies based on the morphology of Homatula have suggested that there is more diversity that the current number of species (19-20), but to what extent this reflects variation within species rather than the presence of undescribed species remained unclear, until scientists began to apply genetic identifications to the genus.

In a paper published in the Biodiversity Data Journal on 16 June 2021, Chuanjiang Zhou, Wenwen Ma, Xi Wang, Yongtao Tang, Xiaoling Meng, and Guoxing Nie of the Engineering Technology Research Center of Henan Province for Aquatic Animal Cultivation at Henan Normal University, describe a new species of Homatula from the Guanhe River, in the HanJiang River drainage (a tributary of the Yangtze River),  in Xixia County, Henan Province.

The new species is named Homatula guanheensis, where 'guanheensis' means 'coming from Guanhe', in reference to the Guanhe River where it was found living in cave environments. Like other Stone Loaches, the new species is an elongate, slender Fish. The known specimens range from 76.9 to 109.26 mm in length, and are cylindrical, and flattened towards the rear. The head is short and flattened, and lacks scales. The snout is short, with nostrils closer to the eye than the tip. The eyes are oval, and located towards the top of the head. The lips are thick, and cover the jaw; there are three pairs of barbels. 

Homatula guanheensis (holotype, HNU 010048, 99.6 mm SL). (A) Lateral view; (B) Dorsal view; (C) Ventral view; (D) Mouth characters; (E) Intestine form; (F) X–ray (lateral view). Zhou et al. (2021).

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Saturday, 26 June 2021

The June Bootid Meteor Shower.

The June Bootid Meteor Shower is visible each year between 26 June and 2 July, typically peaking on 27 June. This meteor shower if highly unpredictable in nature, with most years producing very few meteors, but the shower occasionally having peak years, in which hundreds of meteors are visible each hour; the most recent of such peak years happened in 1998, with the three peaks prior to that happening in 1927, 1921, and 1916. The shower has a radiant point (point from which the meteors appear to radiate) in the constellation of Boötes, close to the North Pole, making the shower possible to spot from anywhere in the Northern Hemisphere, but hard to see in the Southern Hemisphere. Unfortunately, this year peak activity comes only a few days after the Full Moon on 24 June, which means that good observation of the meteors may be hampered by the brightness of the Moon.

The radiant point of the June Bootid Meteor Shower. Space Weather.

Meteor showers are thought to be largely composed of material from the tails of comets. Comets are composed largely of ice (mostly water and carbon dioxide), and when they fall into the inner Solar System the outer layers of this boil away, forming a visible tail (which always points away from the Sun, not in the direction the comet is coming from, as our Earth-bound experience would lead us to expect). Particles of rock and dust from within the comet are freed by this melting (strictly sublimation, transforming directly from a solid to a gas due to the low pressure on it's surface) of the comet into the tail and continue to orbit in the same path as the comet, falling behind over time.

The Earth passing through a stream of comet dust, resulting in a meteor shower. Not to scale. Astro Bob.

The June Bootids Meteor Shower is caused by the Earth passing through the trail of comet 7P/Pons-Winnecke, where it encounters thousands of tiny dust particles shed from the comet as its icy surface is melted (strictly sublimated) by the heat of the Sun. 7P/Pons-Winnecke visits the Inner Solar System every 6.37 years, most recently in 2015, and last came close to the Earth on 1927.

How the passage of the Earth through a meteor shower creates a radiant point from which they can be observed. In The Sky.

7P/Pons-Winnecke was discovered on 12 June 1819 by French astronomer Jean-Louis Pons, then based at Marseilles Observatory, and rediscovered by Friedrich August Theodor Winnecke at Pulkovo Observatory near Saint Petersburg. The designation 7P/Pons-Winnecke implies that it was the seventh comet discovered (7/ - strictly speaking people had been observing comets for thousands of years, but it was not until the mid-eighteenth century that it was realised that they were predictable objects that returned cyclically), that it is a periodic comet (P - again, most comets are periodic, but the term 'periodic comet' is reserved for those with periods of less than 200 years, since these can be reliably predicted), and that it was discovered by Pons and Winnecke.

7P/Pons-Winnecke immaged on 23 September 2015 from Kiev, Ukraine. The image is a single 300 second exposure, with the slightly elongate objects being stars that have moved over the course of the exposure. Alexander Baransky/Kiev Comet Station/Fachgruppe Kometen.

Comet 7P/Pons-Winnecke currently completes one orbit every 2326 days (6.37 years) on an eccentric orbit tilted at 22.3° to the plane of the Solar System, that takes it from 1.26 AU from the Sun (126% of the average distance at which the Earth orbits the Sun) to 5.61 AU from the Sun (5.61 times as far from the Sun as the Earth, and slightly outside the orbit of Jupiter). As a comet with a period of less than 20 years with an orbit angled at less than 30° to the plane of the Solar System, 7P/Pons-Winnecke is considered to be a Jupiter Family Comet.
The orbit and current position of 7P/Pons-Winnecke. JPL Small Body Database.
This orbit means that 7P/Pons-Winnecke occasionally comes close to the Earth, with the last close approach having happened on 12 June 2021 (i.e. 14 days ago), when it reached a distance of 0.44 AU from the Earth (44% of the distance between the Earth and the Sun, or 66 107 000 km). The comet will next come close to us in July 2045, when it will reach a distance of 0.21 AU from the Earth.
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