Comet Lovejoy (C/2014 Q2) was discovered in August 2014 and reached a peak magnitude of around 5 in early 2015. It has an extremely long orbital period of approximately 11,500 years, though planetary perturbations have shortened its period to around 8,000 years. Images taken over 50 minutes on January 2, 2015 show the comet moving relative to background stars at a rate of about 36 km/s as it traveled around 200 million km from the Sun and 70 million km from Earth. The comet displayed a green coma due to fluorescing carbon molecules and a faint blue ion tail. A time-lapse video captures the comet's motion over a 14 second period.

1. Comet Lovejoy (C/2014 Q2)

2. • C/2014 Q2 (Lovejoy) is a new discovery -
August 18, 2014 by Terry Lovejoy
(Brisbane), his 5th.
• At the time in Puppis was “shining” at
15th magnitude.
• As of January 2nd it was being reported
at about magnitude 4.7 to 5.2, but the
light of the waxing gibbous Moon filling
the sky has made it a lot harder to see.

3. Comet Lovejoy features.
• This is a very LONG-PERIOD** comet (orbital
period of +/- 11 500 years).
• Due to perturbations by the planets – shortened
to about 8000 yrs.
• ** Orbital periods depend on origin of the
comet:
– Long period comets (> 200 yrs) originate from the
Oordt Cloud (can be thousands to millions of years),
– Short period comets ( < 200 yrs) are from the Kuiper
Belt (Two families: Jupiter family < 20 yrs, Halley
family: 20 – 200 yrs).

4. • The green colour : Usual for comets’ heads – Molecules of
diatomic carbon (C2) fluorescing in the Sun’s UV light,
• Also some violet (to which our eyes are insensitive) – from
cyanogen (CN),
• The gas tail (ion tail):
– Points away from the sun,
– Tinted blue: Carbon Monoxide ions fluorescing,
– NOT visible in these images - taken from a LIGHT POLLUTED site.
• Dust: appears Sun-coloured: reflected sunlight,
• (Lovejoy had LITTLE dust…),
• “Great” comets usually thus very dusty/ visible, like Lovejoy
of 2011; Hale-Bopp of 1997 etc.
Comet Lovejoy features.

5. “Angular Displacement/ Distance
travelled” in +/- 50 minutes.
• The next slides demonstrate the movement of the
comet against background stars over a period of
50 minutes.
• Jan 2nd, 2015: Two images taken at 21h10 and
21h59: Comet Lovejoy was travelling at +/- 36
km/ sec** relative to the Sun,
• **On Jan 6th : 36.38 km/s (speeding up); +/- 200
mill. km from the Sun, +/- 70 mill. km from Earth.
• The field of view** is +/-0.66 deg. (Horizontal) –
see next slide.

6. “Angular Displacement/Distance”
travelled in +/- 50 minutes**.
21h10
21h59
**
**

7. “Angular Distance/ Displacement” in +/- 50 minutes**.) - Relative to the Great Orion Nebula (M42)
(Similar set-up/ ** FOV as comet images)
**
**

8. “Angular Distance/ Displacement” in +/- 50 minutes**.
(Similar set-up/ **FOV as comet images)
“Reality speed check”:
+/- 36km/s
= 360km/ 10 s
= 3600km/ 100 s
Thus: “covers” the
Moon’s diameter
(3476km) in < 100 s…
The Moon is +/- 0.50
“across”, the ** FOV thus
+/- 0.660 across…
**

9. • Jan 2nd 2015: 21h10 – 21h59
– Meade LX 850 14” telescope,
• Auto-guided with Starlock system,
• Moon waxing gibbous, with **thin, variable cloud cover/
light pollution (BUT FAIR/GOOD SEEING) …
• **Clouds moving across apparent in time-laps movie…
– DSLR: Canon EOS 5D3
– 84 exposures:
• Prime focus,
• 10 sec, ISO 3200,
• Individual exposures: Contrast + saturation adjustments
and noise reduction in Paint.Net.
– Time-laps movie in Picasa:
• 6 frames/sec = duration of +/- 14 sec.
• 2nd clip: shorter - better sky conditions.

10. Click through to the
next slide to view the
video footage

11. Click through to the
next slide to view the
video footage

12. Goodbye…
…until 10 014…
For more comet info:
http://cometchasing.skyhound.com/