Comet C/2023 H2 (Lemmon) approaches perihelion.

Comet C/2023 H2 (Lemmon) will reach its perihelion (the closest point on its orbit to the Sun) on Sunday 29 October 2023, when it will be approximately 0.89 AU from the Sun (i.e. 89% of the distance from the Sun to the planet Earth, or 133 142 000 km). At this time the comet will be 0.49 AU from the Earth, in the constellation of Canes Venatici, having a magnitude of 7.1, making it visible from the Northern Hemisphere with a good pair of binoculars or small telescope.

C/2023 H2 (Lemmon) (green object at centre of picture) observed from Lleida in Spain on 23 September 2023. Exposure time on image was 1 hour. Didac Mesa Romeu/Seichi Yoshida.

Comet C/2023 H2 (Lemmon) was discovered on 28 April 2023 by the University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount Lemmon in the Catalina Mountains north of Tucson. The designation C/2019 U6 (Lemmon) implies that it is a comet (C/), that it was the second comet-like body (2) discovered in the second half of April 2023 (period 2023 H - the year being split into 24 half-months represented by the letters A-Y, with I being excluded), and that it was discovered by the Mount Lemmon Survey (Lemmon).

The orbit and position of Comet C/2023 H2 (Lemmon) on 29 October 2023.  JPL Small Body Database.

Comet C/2023 H2 (Lemmon) has an orbital period of 3876 years and a highly eccentric orbit tilted at an angle of 114° to the plain of the Solar System, that brings it from 0.89 AU from the Sun at closest perihelion (89% of the distance between the Earth and the Sun to 493 AU from the Sun at aphelion (493 times as far from the Sun as the Earth or about 16.4 times as far from the Sun as the planet Neptune, and considerably outside the Kuiper Belt). As a comet with a period of more than 200 years, C/2023 H2 (Lemmon) is considered to be a non-Periodic Comet, since it is unlikely that it would be identified as the same body on another visit to the Inner Solar System.

Comet C/2023 H2 (Lemmon) is expected to pass by ot Earth on 10 November 2023, when the comet will reach 0.19 AU (28 424 000 km) from the planet at about 11.45 pm GMT. This is close for a cometary fly by of the Earth, although it will probably still not be naked eye visible.

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Comet C/2023 P1 (Nishimura) approaches perihelion.

Comet C/2023 P1 (Nishimura) will reach its perihelion (the closest point on its orbit to the Sun) slightly 3.25 pm GMT on Sunday 17 September 2023, when it will be approximately 0.23 AU from the Sun (i.e. 23% of the distance from the Sun to the planet Earth, or 33 689 000 km). At this time the comet will be 0.93 AU from the Earth, in the constellation of Virgo, having a magnitude of 2.1, which under other circumstances might make it naked-eye visible, although its proximity to the Sun will prevent observations and make it dagerous to look for without specialist equipment.

Comet C/2023 P1 (Nishimura) observed from Ceccano, Italy,, on 5 September 2023, using the Virtual Telescope Project ARTEC 10″-F/4.5 (250/1125 MM) telescope. Image is a composite made from eight 60 second exposures, with stars appearing slightly elongated as the telescope tracked the comet. Gianluca Masi/Virtual Telescope Project.

Comet C/2023 P1 (Nishimura) was discovered on 12 August 2023 Japanese amateur astronomer Hideo Nishimura. The name C/2023 P1 (Nishimura) implies that it is a Comet (C/), that it was the 1st comet discovered in the first half of August 2023 (period 2023 P), and that it was discovered by Nishimura.

Comet C/2023 P1 (Nishimura) has an orbital period of 434 years and a highly eccentric orbit tilted at an angle of 132° to the plain of the Solar System, that brings it from 0.23 AU from the Sun at closest perihelion (23% of the distance between the Earth and the Sun, and considerably inside the orbit of Mercury) to 114 AU from the Sun at aphelion (114 times as far from the Sun as the Earth or a little under four times as far from the Sun as the planet Neptune, and slightly outside the Kuiper Belt). As a comet with a period of more than 200 years, C/2023 P1 (Nishimura) is considered to be a non-Periodic Comet, since it is unlikely that it would be identified as the same body on another visit to the Inner Solar System.

The orbit and position of Comet C/2023 P1 (Nishimura) on 17 September 2023.  JPL Small Body Database.

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Comet C/2023 P1 (Nishimura) makes its closest pass to the Earth.

Comet C/2023 P1 (Nishimura) will pass by the Earth at a distance of 125 363 000 km (83.8% of the distance between the Earth and the Sun), on Tuesday 12 September 2023. At this time the comet will be in the constellation of Leo, but will not be visible due to its proximity to the Sun.

Comet C/2023 P1 (Nishimura), imaged from the Trevinca-Skies remote-astronomy facility at A Veiga in Ourense Province, Spain, 0n 25 August 2023. Image is a composite made up of four 30 second exposures. Stars in background are slightly elongated due to their movement relative to the comet over this time interval. Wikimedia Commons.

Comet C/2023 P1 (Nishimura) was discovered on 12 August 2023 Japanese amateur astronomer Hideo Nishimura. The name C/2023 P1 (Nishimura) implies that it is a Comet (C/), that it was the 1st comet discovered in the first half of August 2023 (period 2023 P), and that it was discovered by Nishimura.

Comet C/2023 P1 (Nishimura) has an orbital period of 434 years and a highly eccentric orbit tilted at an angle of 132° to the plain of the Solar System, that brings it from 0.23 AU from the Sun at closest perihelion (23% of the distance between the Earth and the Sun, and considerably inside the orbit of Mercury) to 114 AU from the Sun at aphelion (114 times as far from the Sun as the Earth or a little under four times as far from the Sun as the planet Neptune, and slightly outside the Kuiper Belt). As a comet with a period of more than 200 years, C/2023 P1 (Nishimura) is considered to be a non-Periodic Comet, since it is unlikely that it would be identified as the same body on another visit to the Inner Solar System.

The orbit and position of Comet C/2023 P1 (Nishimura) on 12 September 2023.  JPL Small Body Database.

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Comet C/2020 K1 (PANSTARRS) approaches perihelion.

Comet C/2020 K1 (PANSTARRS) will reach its perihelion (the closest point on its orbit to the Sun) slightly before 2.00 am GMT on Tuesday 9 May 2023, when it will be approximately 3.07 AU from the Sun (i.e. 3.07 times as far from the Sun as the planet Earth, or 459 829 000 km). At this time the comet is 2.63 AU from the Earth, in the constellation of Pavo, having a magnitude of 12.98, making it visible with a telescope with an aperture of 250 mm or greater. The constellation of Corona Borealis is high in the Southern Hemisphere sky, which means that viewing this comet will be impossible from much of the Northern Hemisphere.

The trajectory of Comet C/2020 K1 (PANSTARRS), and its position at 2.00 am GMT on 9 May 2023. JPL Small Body Database.

Comet C/2020 K1 (PANSTARRS) was discovered on 17 May 2020 by the  the University of Hawaii's PANSTARRS telescope. The name C/2020 K1 (PANSTARRS) implies that it is a comet (C/), that it was discovered in the second half of May 2020 (period 2020 K), that it was the first comet discovered within this period (1), and that it was discovered by the PANSTARRS telescope.

C/2020 K1 (PANSTARRS) observed from Tuscon, Arizona, on 6 May 2021. Mike Olason/Sky & Telescope.

Comet C/2020 K1 (PANSTARRS) has an estimated orbital period of 1.98 million years and a highly eccentric orbit tilted at an angle of 89.66° to the plain of the Solar System, that brings it from 3.07 AU from the Sun at closest perihelion (307% of the distance between the Earth and the Sun, or more than twice as far from the Sun as the planet Mars) to 31 499 AU from the Sun at aphelion (31 499 times as far from the Sun as the Earth, within the Outer Oort Cloud). As a comet with a period of more than 200 years, C/2020 K1 (PANSTARRS) is considered to be a Long Period Comet.

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Comet C/2021 P4 (ATLAS) reaches perihelion.

Comet C/2021 P4 (ATLAS) reached its perihelion (the closest point on its orbit to the Sun) slightly after 9.00 am GMT on Saturday 30 July 2022, when it will be approximately 1.08 AU from the Sun (i.e. 1.08 times as far from the Sun as the planet Earth, or 161 360 000 km). At this time the comet is 1.95 AU from the Earth, in the constellation of Leo, having a magnitude of 12.55, making it visible with a telescope with an aperture of 250 mm or greater, making it fairly close to the Sun, and best observed slightly after dusk (extreme caution should be taken when observing objects close to the Sun, and an optical instrument should never be looked through when it is pointing close to the Sun).

The trajectory of Comet C/2021 P4 (ATLAS), and its current position. JPL Small Body Database.

C/2021 P4 (ATLAS) was discovered on 10 August 2021 by the Asteroid Terrestrial-impact Last Alert System (ATLAS) search program. The name C/2021 P4 (ATLAS) implies that it is a comet (C/), that it was the fourth comet (4) discovered in the first half of August 2021 (period 2021 P) and that it was discovered by the ATLAS program.

Comet C/2021 P4 (ATLAS) is estimated to complete one orbit every 5574 years on an eccentric orbit tilted at 56.3° to the plane of the Solar System, that takes it from 1.08 AU from the Sun (108% of the average distance at which the Earth orbits the Sun) to 628 AU from the Sun (628 times as far from the Sun as the Earth, and roughly 21 times the distance at which the planet Neptune orbits the Sun). As a comet with an orbital period of more than 200 years it is considered to be a Long Period Comet; such comets are sometimes referred to as Non-periodic Comets, since there is no expectation of their being another observation being made by anyone who will remember the current comet naming-system, although this name does not distinguish them from Parabolic Comets, which are knocked from a position in the Oort Cloud by an encounter with some other object, and pass through the Inner Solar System once before disappearing into space, or Interstellar Comets, which originate outside the Solar System and only pass through it once.

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The Lyrid Meteors.

The Lyrid Meteors is expected to be visible between Saturday16 and Monday 25 April this year (2022), and will be at peak visibility on Friday 22 April. With the Third Quarter Moon falling on Saturday 23 April, this year will not be the best opportunity to see these meteors, but nevertheless there should be a good chance to see them in cloudless areas. At its peak the Lyrid Meteor shower typically produces about 20 meteors per hour, though higher rates have been recorded. The Lyrid Meteors take their name from the constellation of Lyra, from which they appear to radiate, at a point close to the star Vega, which will be above the horizon for most of the night from most places on Earth this week, setting at about 5.00 am.

 

The Radiant Point (i.e. point from which the meteors appear to radiate) of the Lyrid Meteors. Bruce McClure/Joni Hall/EarthSky/Wikimedia Commons.

The Lyrid Meteors are comprised of debris from the comet C/1861 G1 Thatcher (named after the astronomer A. E. Thatcher, not the politician). This is a long-period comet that spends most of its time in the Oort Cloud, only visiting the inner Solar System once every 415 years, the last occasion being in 1861. When the comet visits the inner Solar System it is heated by the Sun, melting the ices that make up its surface and releasing a trail of dust, which continues to follow the path of the comet. The Earth passes through this trail in April each year, creating a light show as the dust particles burn in the upper atmosphere.

 

The orbit and current position of Comet C/1861 G1 Thatcher. JPL Small Body Database.

Comet C/1861 G1 Thatcher completes one orbit every 415 years on an eccentric orbit tilted at 79.8° to the plane of the Solar System, that takes it from 0.92 AU from the Sun (92% of the average distance at which the Earth orbits the Sun) to 106 AU from the Sun (110 times as far from the Sun as the Earth, and more than three times the distance at which the planet Neptune orbits the Sun). The comet last visited the Inner Solar System in 1891, and is expected to return again in 2306. As a comet with an orbital period of more than 200 years it is considered to be a Long Period Comet.

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