Category Archives: Comets

Close Encounter with a Comet

Here we have radar pictures of comet P/2016 BA14. The images were taken with an antenna of NASA’s Deep Space Network at Goldstone, California on 23 March 2016 when the comet was only 3.6 million km / 2.2 million miles from Earth.

Astronomers at the Planetary Science Institute also observed the comet with the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawaii. Very cool findings

Here is PSI’s press release:
March 24, 2016, Tucson, Ariz. — Astronomers at the Planetary Science Institute made observations of Comet Pan-STARRS (P/2016 BA14) using the NASA Infrared Telescope Facility (IRTF) on Mauna Kea, Hawai’i that show that it reflects less than 3 percent of the sunlight that falls on its surface. For comparison, fresh asphalt reflects about 4 percent of the light that falls on it.

Comet Pan-STARRS made a close flyby of the Earth at a distance of 3.6 million kilometers (2.2 million miles) on March 22. This is one of the closest flybys of a comet in recorded history and the last one to come closer was Lexell’s comet that flew by the Earth at a distance of 2.2 million kilometers (1.4 million miles) on July 1, 1770.

“We measured the spectral and thermal properties of the comet using the NASA IRTF and found that the comet reflects between 2-3 percent of the sunlight that falls on it,” said Vishnu Reddy, research scientist at the Planetary Science Institute in Tucson, Arizona. “This is typical for comets,” Reddy added. Based on its reflective properties, Reddy estimates the size of the comet to be between 600 meters and 1.2 kilometers (0.4 miles and 0.75 miles) in diameter.

Comet Pan-STARRS was originally discovered as an asteroid and later found to have cometary properties when astronomers realized its orbit is similar to another short period comet 252P/LINEAR, which also made a close flyby of the Earth at 5.3 million kilometers (3.3 miles) on March 21.

“It is an extremely rare opportunity to be able to study a pair of comets with historically close flybys. Measuring the physical properties of both comets will help us understand the evolution of comets in general,” said Jian-Yang Li, Senior Scientist at PSI. Li was observing 252P/LINEAR with the Hubble Space Telescope during its close encounter.

This research was funded by NASA Near-Earth Object Observations program. The Infrared Telescope Facility is operated by the University of Hawaii under contract NNH14CK55B with the National Aeronautics and Space Administration.

Image: NASA/JPL-Caltech/GSSR

Comet Catalina


UPDATE: I was clouded in this morning so after looking at satellite image I drove about 16 km north and I found Catalina to be a naked-eye comet.  It is pretty small but if you have even a small pair of binoculars it is easy to see.

A beautiful shot of Comet Catalina in the northern sky the other morning.  This image was taken about 60 km east of here before sunrise.

Comet Catalina is a binocular object about now and is pretty easy to find in the morning sky.  Yes, should be worth getting up early for.   To find Catalina, locate the “Plough  or Big Dipper”  follow along the handle and look about half way between the last star in the “handle” (the star is named Alkaid) and the star Arcturus.

To make it a little easier, I’ve located the stars with red asterisks here.  Make sure you have binoculars and your eyes are dark adapted.  Go outside and stay out of any bright light sources for a few minutes (15 is good) and have a look.

Thanks for the awesome image Andrew!

Neowise and Comet Christensen



This is a great press release, I believe I saw this comet back in 2009 I need to look back and see if I did, I’m pretty sure though.

Christensen has a period of 2,409,303 years!

Other Christensen facts at Heavens Above.

The Newowise caption:

An infrared view from NASA’s NEOWISE mission of the Oort cloud comet C/2006 W3 (Christensen). The spacecraft observed this comet on April 20th, 2010 as it traveled through the constellation Sagittarius. Comet Christensen was nearly 370 million miles (600 million kilometers) from Earth at the time.

The image is half of a degree of the sky on each side. Infrared light with wavelengths of 3.4, 12 and 22 micron channels are mapped to blue, green, and red, respectively. The signal at these wavelengths is dominated primarily by the comet’s dust thermal emission, giving it a golden hue.

The WISE spacecraft was put into hibernation in 2011 upon completing its goal of surveying the entire sky in infrared light. WISE cataloged three quarters of a billion objects, including asteroids, stars and galaxies. In August 2013, NASA decided to reinstate the spacecraft on a mission to find and characterize more asteroids.

JPL manages NEOWISE for NASA’s Science Mission Directorate at the agency’s headquarters in Washington. The Space Dynamics Laboratory in Logan, Utah, built the science instrument. Ball Aerospace & Technologies Corp. of Boulder, Colorado, built the spacecraft. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA.

Comet Hunter – Shoemaker(s) and Levi

SOHO maybe the most successful space based comet hunters but it is very difficult to talk about the best comet hunters without including Eugene and Carolyn Shoemaker and David Levy. They have many comet discoveries to their credit including the famous Shoemaker-Levi 9 comet.


Rosetta’s Shadow

Rosetta's shadow on Comet 67/C-G taken on 14 February 2015. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Rosetta’s shadow on Comet 67/C-G taken on 14 February 2015. Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Here’s something you don’t see very often or ever for that matter. We can see the shadow of ESA’s Rosetta spacecraft on Comet 67P/Churyumov-Gerasimenko.

During the close flybys of a couple week ago, only 6 km separated spacecraft and comet. During the flyby the sun was directly between sun and comet so a shadow of about 20 x 50 meters (66 x 164 feet) was projected onto the comet. ESA was able to capture the image with the OSIRIS camera.

The pair were about 2.35 AU from the Sun so if I did the math correctly the light levels would be approximately 5.5 times less bright than what we see around us.

Approximate brightness relative to us is about the distance in AU (astronomical units) to the power of 2,

2.35 AU 2 = 5.5 (in this case 5.5 X dimmer)

Is this a first? I can’t think of any example of shadows on other comet encounters.

ESA has a nice write up and more pictures at the Rosetta blog, check it out.

Comet Dust

Dust particles from Comet 67P/Churyumov-Gerasimenko collected by ESA's Rosetta spacecraft. Copyright ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/ BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S
Dust particles from Comet 67P/Churyumov-Gerasimenko collected by ESA’s Rosetta spacecraft. Copyright ESA/Rosetta/MPS for COSIMA Team MPS/CSNSM/UNIBW/TUORLA/IWF/IAS/ESA/ BUW/MPE/LPC2E/LCM/FMI/UTU/LISA/UOFC/vH&S

One of the instruments on board ESA’s Rosetta called COSIMA, short for the COmetary Secondary Ion Mass Analyser one of three dust analysis experiments.

Essentially this instrument has a plate for catching dust grains from the comet at fairly low speeds. The dust grains shown above is two of the grains collected and they have yielded some interesting results.

I’ll let ESA explain:

Two examples of dust grains collected by Rosetta’s COmetary Secondary Ion Mass Analyser (COSIMA) instrument in the period 25–31 October 2014. Both grains were collected at a distance of 10–20 km from the comet nucleus. Image (a) shows a dust particle (named by the COSIMA team as Eloi) that crumbled into a rubble pile when collected; (b) shows a dust particle that shattered (named Arvid).

For both grains, the image is shown twice under two different grazing illumination conditions: the top image is illuminated from the right, the bottom image from the left. The brightness is adjusted to emphasise the shadows, in order to determine the height of the dust grain. Eloi therefore reaches about 0.1 mm above the target plate; Arvid about 0.06 mm. The two small grains at the far right of image (b) are not part of the shattered cluster.

The fact that the grains broke apart so easily means their individual parts are not well glued together. If they contained ice they would not shatter; instead, the icy component would evaporate off the grain shortly after touching the collecting plate, leaving voids in what remained. By comparison, if a pure water-ice grain had struck the detector, then only a dark patch would have been seen.

These ‘fluffy’ grains are thought to originate from the dusty layer built up on the comet’s surface since its last close approach to the Sun, and will soon be lost into the coma.

Be sure to check the Rosetta Blog. The have this and results from six other Rosetta’s science instruments since arriving at Comet 67P/Churyumov-Gerasimenko – great stuff!!