Comet C/2021 T4 Lemon is sweeping the southern sky

The famous British astronomer Guy Otewell This article was originally published about Comet C/2021 T4 Lemon on May 25, 2023. Reprinted with permission. Edits by EarthSky.

Comet C/2021 T4 Lemon

Comet C/2021 T4 Lemmon was discovered on October 7, 2021, in images taken at Mount Lemon ObservatoryNortheast of Tucson, Arizona. T4 It means the fourth discovery or recovery in the first half of October.

Mount Limon is the highest point in the Santa Catalina Mountains, one of four mountain ranges around Tucson. Not to be confused with Catiline, the conspirator who attempted to seize power over the Roman Republic in 63 BC. I remember conjecturing that the Navajos may have viewed Canopus, the great star of the south, from one of the four sacred peaks surrounding their land. In fact, it is displayed as the cover photo of Astronomical calendar 2023.

Upon its discovery, Comet C/2021 T4, due to the geometry of its orbit, appeared just north, at an eccentricity of +12°.

Comet C/2021 T4 Lemon is a long-period comet

In fact, it’s a long-term offender; If it had previously fallen from its distant home – at 44,000 AU – into the inner solar system, it would have happened millions of years ago. So during its current passage, you will feel the gravity disorders One of the planets whose duration will be shortened to thousands of years only.

Its orbit is inclined about 20 degrees to the plane of the ecliptic. However, it is traveling in retrograde, or opposite to the direction in which the planets rotate. The result is that it will make a very long, fast sweep across the southern sky.

Researcher scheme

At the moment, the comet is located 60 degrees in the morning sky, south (at declination -13 degrees), 1.75 astronomical units from the Sun and 2 astronomical units from the Earth. However, it is still a lackluster size about 11. Then, on June 27, 2023, the distance between us and us will shrink to 1 AU.

On July 18, 2023, we will pass it in opposition. And around this time, it will be closest to us, 0.54 AU, and brightest, probably around 8 or 7, but still below the naked eye limit. Its close proximity will make it appear far to the south, at declination -56 degrees on July 20.

Then in the following months it will climb further north, becoming lower in the evening sky and more distant. At the same time it will dim by maybe 2 or 3. It will arrive rock bottom1.48 AU from the Sun, on July 31, 2023. Finally, it will ascend through the ecliptic on September 10, 2023, and will be conjunction behind and north of the Sun on November 9, 2023.

Of course, we must remember that predictions about the comet’s brightness and the size of its tails can be unreliable. That’s because it depends on the melting of ice and the emission of dust in these clumps of spinning bodies.

Comet Hale-Bopp is still observable? amazing!

By the way, Alan Hill He (Jay Otewell) alerted us to this comet through a Facebook post on May 22nd. Alan was the discoverer of the great comet Hale-Bopp (C/1995 O1). And despite being more than 47 astronomical units away, it is the first of its kind in space Minor Planet Centre List of comets currently observable, not due to their current size (about 20) but because it is the first still non-periodic comet ever seen.

Bottom line: Comet C/2021 T4 Lemmon was discovered by the Mount Lemmon Observatory in 2021. It is currently sweeping the southern skies.