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Comets » 

Comet C/2021 T4 (Lemmon)

Below the horizon.  Rise: 17:51 | Tran: 2:13 | Set: 10:31
Alt: -10.19°   Az: 24.90°   Direction: North-North-East

Comet C/2021 T4 (Lemmon) is in the constellation of Leo, at a distance of 823,140,124.0 kilometers from Earth. The current Right Ascension is 11h 58m 44s and the Declination is +24° 40’ 46” (apparent coordinates). The predicted magnitude of Comet C/2021 T4 (Lemmon) is 19.14 (data provided by JPL Horizons).

Finder Charts

Map showing Comet C/2021 T4 (Lemmon) in Leo on February, 16 2025. Field of view: 50x30 degrees
View interactive star map
Sky map showing Comet C/2021 T4 (Lemmon) in Leo on February, 16 2025. Field of view: 15x9 degrees. View in interactive sky chart

High precision deep sky finder chart, 60 arcmin wide, showing where Comet C/2021 T4 (Lemmon) is right now. Click on the image to see a more detailed fullscreen tracker view.

C/2021 T4 (Lemmon)
RA: 11h 57m 27s
Dec: +24° 49’ 10”
Deep sky finder chart for Comet C/2021 T4 (Lemmon). Field of view: 60x40 arcmins. View in deep sky object tracker

Also check out Where is Comet C/2021 T4 (Lemmon)?, a page that provides all the information needed to find Comet C/2021 T4 (Lemmon) in the sky and additional links to sky charts.

Celestial Coordinates

Apparent

11h 58m 44s
+24° 40’ 46”
13h 48m 31s
01h 47m 16s

J2000

11h 57m 27s
+24° 49’ 10”

Additional Information

Leo
n/a
n/a
n/a
n/a
19.14

The observed values of Magnitude, Coma Diameter and Tail Length are derived from the most recent observation recorded at the Comet Observers Database. The value of Predicted Magnitude comes from the JPL Horizons ephemerides service and, in the case of comets, might be inaccurate given the highly dynamic and unpredictable behavior of these objects. When available, please refer to the Observed Magnitude value and consider the Predicted Magnitude as a directional indication. We acknowledge with thanks the comet observations from the COBS Comet Observation Database contributed by observers worldwide and used in this table to report recent comet observations.

Rise and Set Times

Today's rise, transit and set times of Comet C/2021 T4 (Lemmon) from Greenwich, UK (all times relative to the local timezone Europe/London):

Azimuth: 65.3°
Max altitude: 63.1°
Azimuth: 294.7°
  • C/2021 T4 (Lemmon) is below the horizon from Greenwich, UK.
  • Given its current magnitude, C/2021 T4 (Lemmon) is visible only through long exposure photography.
  • Go to interactive sky chart

If you need to access this information frequently for your observations, you can create a simple customized Quick Access page, so that you can easily bookmark it in your browser favorites or add a shortcut to your mobile phones' home screen.

Distance from Earth

The distance of Comet C/2021 T4 (Lemmon) from Earth is currently 823,140,124.0 kilometers, equivalent to 5.5023518727 Astronomical Units. Light takes 45m 45.700s to travel from Comet C/2021 T4 (Lemmon) and arrive to us.

823,140,124.0
5.5023518727
45m 45.700s

The following chart shows the distance of Comet C/2021 T4 (Lemmon) from Earth as a function of time. In the chart the distance data is measured in Astronomical Units and sampled with an interval of 1 day.

Chart of the distance of Comet C/2021 T4 (Lemmon) from Earth in Astronomical Units (au)

The value of the reported distance might be somewhat inaccurate around the times of closest approach for objects passing extremely close to Earth. The value of the distance of C/2021 T4 (Lemmon) from Earth is also available as a real time updated value in the Live Position and Data Tracker.

Closest Approach

Between 1 January 2000 and 31 December 2099, the closest approach of Comet C/2021 T4 (Lemmon) to Earth happens on Fri Jul 21 2023 at a distance of 0.541534 Astronomical Units, or 81,012,307 kilometers:

Fri Jul 21 2023
81,012,307
0.541534

NOTE: values for the closest approach are computed with a sampling interval of 1 day.

Light Curve

The following chart is the predicted light curve (visual magnitude as a function of time) of Comet C/2021 T4 (Lemmon), according to the most recent ephemerides data. Magnitude data is sampled with a 2 days interval and there might be inaccuracies for objects changing brightness very rapidly during the course of a few days. For comets there could be large discrepancies between the observed and predicted brightness because of their highly dynamic behaviour.

Chart of the magnitude of Comet C/2021 T4 (Lemmon) as a function of time

Orbital Elements

The following table lists the orbital elements of Comet C/2021 T4 (Lemmon) at epoch 19 August 2022 00:00 UTC (JD: 2459811.5). Source: JPL Small-Body Database

Element Symbol Value
Orbit eccentricity e 0.99996874
Orbit inclination i 160.75778068°
Perihelion distance q 1.48199298 AU
221,702,995 km
Aphelion distance Q 94,810.21049579 AU
14,183,405,639,233 km
Semi-major axis a 47,405.84624439 AU
7,091,813,671,114 km
Orbital period period 10,321,814.6864 years
3,770,042,814.1990 days
Date of perihelion transit Tp 2023-Jul-31 12:33:47
2,460,157.0235 JD
Next perihelion transit 2023-Jul-31 12:33
3,772,502,971.2225 JD
Argument of perihelion peri 329.7808734849°
Longitude of the ascending node node 257.8014092137°
Mean anomaly M 359.99996700609°
Mean motion n 0.00000010°/day

Orbit Visualization

Orbit Diagram of Comet C/2021 T4 (Lemmon)
View Comet C/2021 T4 (Lemmon) in the 3D Solar System Simulator

15 Days Ephemeris

The following table lists the ephemerides of Comet C/2021 T4 (Lemmon) computed for the past and next 7 days, with a 24 hours interval. Apparent celestial coordinates are provided.

Date Right AscensionR.A. DeclinationDec. MagnitudeMag Constellation
2025 Feb 09 12h 04m 56s +23° 46’ 46” 19.10 Coma
2025 Feb 10 12h 04m 09s +23° 53’ 56” 19.10 Coma
2025 Feb 11 12h 03m 22s +24° 01’ 04” 19.11 Coma
2025 Feb 12 12h 02m 34s +24° 08’ 10” 19.11 Coma
2025 Feb 13 12h 01m 46s +24° 15’ 14” 19.12 Coma
2025 Feb 14 12h 00m 57s +24° 22’ 16” 19.12 Coma
2025 Feb 15 12h 00m 08s +24° 29’ 14” 19.13 Coma
2025 Feb 16 11h 59m 18s +24° 36’ 10” 19.13 Leo
2025 Feb 17 11h 58m 27s +24° 43’ 03” 19.14 Leo
2025 Feb 18 11h 57m 36s +24° 49’ 52” 19.14 Leo
2025 Feb 19 11h 56m 45s +24° 56’ 38” 19.15 Leo
2025 Feb 20 11h 55m 54s +25° 03’ 20” 19.15 Leo
2025 Feb 21 11h 55m 02s +25° 09’ 59” 19.16 Leo
2025 Feb 22 11h 54m 09s +25° 16’ 34” 19.16 Leo

Additional Resources