Leeds Astronomical Society LAS Meetings Observing Membership



Comets (& Asteroids)

Scroll & select a comet from the previews below to display the respective image(s).

  • C2020/F3 (Neowise)
    C2020/F3 (Neowise)
  • C2019/Y4 (Atlas)
    C2019/Y4 (Atlas)
  • Comet 17P (Holmes)
    Comet 17P (Holmes)
  • C/2006 M4 (Swan)
    C/2006 M4 (Swan)
  • C/2006 A1 (Pojanski)
    C/2006 A1 (Pojanski)
  • Comet 9P/Tempel 1
    Comet 9P/Tempel 1
  • C/2004 Q2 (Machholz)
    C/2004 Q2 (Machholz)
  • C/2004 Q1 (Tucker)
    C/2004 Q1 (Tucker)
  • Comet 78P (Gehrels)
    Comet 78P (Gehrels)
  • C/2003 K4 (Linear)
    C/2003 K4 (Linear)
  • C/2003 T4 (Linear)
    C/2003 T4 (Linear)
  • C/2002 T7 (Linear)
    C/2002 T7 (Linear)
  • C/2001 Q4 (Neat)
    C/2001 Q4 (Neat)
  • Asteroids Psyche & Parthenope
  • Asteroid (7482) 1994 PC1
    (7482) 1994 PC1

C2019/Y4 (Atlas)

(Ivor Trueman)

C2019/Y4 (Atlas)

This comet was discovered in Dec. 2019 by the ATLAS (Asteroid Terrestial-impact Last Alert System), a robotic astronomical survey project in Hawaii.

It was hoped that this would be another of the great comets, but as it approached the Sun it split into four pieces and subsequently broke up further into 25-30 fragments.

The above image is a composite of 45 × 60 second exposures taken in Cookridge on the 22nd March 2020, with a DLSR and Skywatcher 130dps newtonian. Because comets appear to move in relation to the background stars, the processing of the data requires stacking the images with respect to the comet position, as well as the usual method of aligning & stacking the images using the star positions. In the 'Comet' image the stars appear to trail & have to be removed, and in the 'Stars' image the comet appears blurred & has to be removed. The 'Comet' and 'Star' image then have to be recombined. The results are always that great!

Below is a short video that compresses the 45 minutes plus, of the unprocessed data, into 8 seconds. The Comet can be seen moving in the bottom left of the picture.

For more info. on C2019/Y4 (Atlas) see the Wikipedia.



Astronomical Units

The Astronomical Unit, or AU was originally defined as the average distance from the Earth to the Sun when at the closest and farthest points apart (called the aphelion and perihelion respectively). i.e. 1 × AU is about 150 million km (93 million miles) or about 8 light-minutes.

In 2012 the AU was defined to be exactly 149,597,870.7 km.

Measuring distances in Astronomical Units, provides a reasonable 'yardstick' for measuring distances on the scale of the Solar system, which would otherwise become unwieldy if they had to be represented in km or miles.

Stellarparallax parsec1

For the even larger distances outside of the Solar System, the Astronical Unit forms the basis of another distance measurement the parsec.

A parsec is defined as the distance which one AU subtends an angle of one arcsecond (1/3600th of a degree), and is equivalent to approx. 206,264.8 AU's or 3.262 light-years.

i.e. if when the Earth moves through a distance of 1 AU, a star appears to move by 1/3600th of a degree when compared to background stars, then the disance to the star is 1 parsec.

For example our closest major galaxy, Andromeda is 778,000 parsecs away, or approx. 160 billion AU (or 2.537 million light-years).