Sep 222017

As many of you know the OSIRIS-REx spacecraft made an Earth gravitational assist fly-by today. The spacecraft needed the slingshot maneuver to make it to its rendezvous with the asteroid Bennu in August 2018. The spacecraft will orbit the asteroid for up close study, then drop low enough to grab a sample of the surface for return to the Earth in September 2023.

NASA put out a call to amateur astronomers to take images of the spacecraft as it approached the Earth. So, for the past week I have been attempting to do just that. Last night the spacecraft was finally bright enough for me to catch it in a series of exposures. Even so, the speed, brightness and size of the spacecraft makes it very difficult to see.

The above image is the third of eight 300 second exposures that I was able to get before the clouds closed in. The circle shows the location of the automobile sized craft which should give you an idea where it will be in the following animation. The craft’s motion is from upper right to middle left.

I had to stretch the images as well as invert them to make the faint streak a little more visible. This close to the Earth the apparent velocity of OSIRIS-REx is obvious.

[Update: 03 Jan 2018] OSIRIS-Rex is now projected to arrive at Bennu in December of 2018. Approach operations will begin in August.

 Posted by at 14:37
Feb 042017

On the second of February a small asteroid buzzed the Earth. Discovered only three days earlier by the PanSTARRS 1 telescope in Hawaii, the rock missed us by less than half the distance to the Moon. The most recent estimates of its size are in the range of 11-25m making it roughly the size of the asteroid that entered the atmosphere over the Russian city of Chelyabinsk on the 15th of Feb 2013.

(2017 BS32) [C:3x300s]

This image is a stack of three 300 second images taken on the evening prior to the object’s closest approach. The asteroid is seen as three distinct faint streaks starting in the top right and traveling down to the bottom center. Clicking on the image will provide a larger view where the streaks will be a little easier to see.

The wispy vertical artifact at lower center is either the remains of an aircraft contrail or a meteor train. I capture these every so often. Animating several of these exposures shows a slow drift indicating it is atmospheric in nature.

 Posted by at 14:43
Jul 012016


Yesterday, June 30th, was Asteroid Day. The following is quoted directly from the Asteroid Day website.

Asteroid Day is a global awareness campaign where people from around the world come together to learn about asteroids, the impact hazard they may pose, and what we can do to protect our planet, families, communities, and future generations from future asteroid impacts. Asteroid Day is held each year on the anniversary of the largest impact in recent history, the 1908 Tunguska event in Siberia.

The primary activity at the PTO is asteroid and comet orbit verification. The PTO’s primary telescope is too small to have any real chance of discovering a new asteroid or comet. But discovery is only part of the effort. The orbits of these objects can and have been changed by any number of physical processes. So, the PTO monitors known asteroids and comets to make sure they are where we think they are.

The way the PTO does this is to take a series of nine 300 second images of the target asteroid and then through computer analysis, determine sub arc second positions for the object. The information of at least three of the observations is then transmitted to the Minor Planet Center for comparison with predicted positions. The image below is a stack of 3 images with the asteroids circled showing their movement. The image is a negative of the stacked exposures. It is quite often easier to see darker objects against a white background than the other way around. Also visible is the track of a satellite recorded during one of the images.



The motion of all the asteroids is from the top of the image (East) toward the bottom (West). Since 2009 the PTO has submitted ≈2700 observations to the MPC.

 Posted by at 16:39
Dec 172012

(4179) Toutatis takes 4 years to orbit the Sun. At it’s furthest point it is just inside Jupiter’s orbit; at it’s closest, just inside Earth’s.  These conditions lead to frequent close approaches between Earth and Toutatis.  The most recent was on the 12th of December 2012.  The distance between them was about 18 Lunar Distances (LD).  The asteroid is roughly peanut shaped with the longest axis being about 2.8 miles in length.  



Although the Minor Planet Center classifies the body as a potentially hazardous asteroid (PHA), current modeling shows no threat of an Earth impact for at least 600 years.  That is about the limit of current orbit simulations for Toutatis.  It’s orbit is resonant with both Jupiter and Earth leading to a chaotic orbit and increasingly inaccurate predictions.  The next reasonable close approach will be in 2069 and somewhat closer at 8 LD.

This video consists of 90 ten second images taken about 10 seconds apart, showing about 30 minutes of motion.  The flash obvious just to the left of the asteroid’s path is probably a satellite.  At the time, Toutatis was crossing the constellation Pisces.

I measured the asteroid’s brightness at an average magnitude of 10.6 making this easily visible in a backyard telescope.

 Posted by at 15:07
Nov 132011

Observations on the evening of the 8th of November marked the first official observations at the Pear Tree Observatory since it passed final inspection by the city building inspector. The object being observed that  night was also special.  As you might have heard, that evening, asteroid 2005 YU55 passed the earth within the orbit of the moon.  The asteroid is relatively large with a diameter of 400 meters. Being this close meant it was covering a lot of sky very fast; that large meant it would be quite bright.

Since I have had problems in the past finding close fast objects with TheSky6, I used the Minor Planet Ephemeris Service to generate a list of coordinates appropriate for the observatory’s location.  Guest astronomer Frank Atchison and I used those coordinates to position the telescope.  2005 YU55 was moving so quickly that we missed it several times using coordinates based on the current time.  We couldn’t get coordinates for ‘now’ entered in, slew the telescope and take an image before the asteroid left the field of view.  Ultimately, we positioned the telescope 15 minutes ahead of the asteroid and we took exposures until it passed into and out of the FOV.  All the while, we watched as clouds appeared over the tree line and headed for the part of the sky that we were pointed at.

”]This image is a stack of 3 individual exposures. One being 30 seconds, one being 10 seconds and the last 1 second.  The asteroid in the 1 second image is very near the bottom, left of center and just left and below a double star.  We used this set to determine that the asteroid was traveling so fast that a half-second exposure was needed to get a un-smeared image.  Of course, by then we had a pretty solid cloud deck getting in the way and the next set of half-second images were useless for measuring.

 Posted by at 21:49