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
Jun 272011

As you might have heard, an asteroid (2011 MD) buzzed us this afternoon.  The asteroid was discovered on the 22nd by the Lincoln Near Earth Asteroid Research program (LINEAR).  By the 23rd a call went out for astrometric observations to further refine the orbit of the asteroid.  Time was being requested at the Goldstone Radio Observatory in order to ‘image’ the interloper as it passed and precise positioning would be required.

I started observations Friday night (24th).  Since the asteroid was comparatively very close,  its orbit was being significantly changed by the earths gravitational field.  Normally, the numbers that define an orbit (orbital elements) change very little, absent any external interference.  But, the closeness and speed of 2011 MD meant that the numbers were changing very rapidly.  My planetarium software can directly download the latest elements from the Minor Planet Center and I did so just before my time on the  scope Friday night.  The software then takes the numbers and calculates the apparent position of the object as viewed from here.  After numerous exposures I saw nothing.  It was easy to verify that I was looking where the asteroid was supposed to be, and I was spot on.  The problem could have been two things: the position was bad or the asteroid was too dim.

Strike one.

Saturday night was the astronomy club meeting, but right after I got home, back out to the observatory.  I once again downloaded the latest orbital elements.  The position had moved (as expected) and was reasonable for a days worth of motion.  Since the rock was coming directly towards us, most of the motion was radial to us with not a whole lot of movement across the sky.  At least not yet.  I took exposures until 0200 local.  Still nothing.  Again the exposures were right where the asteroid was supposed to be.  However, by now there were plenty of exposures taken by other observers and they showed the object to be bright enough that I should have been able to see it.

Strike two.

Chatter on the discussion boards I frequent indicated that others were also having problems with the asteroid’s position; at least I wasn’t the only one.  By now it was Sunday afternoon and it was then I remembered I had problems finding a close pass last year.  Ultimately, I had to ‘manually’ find the position and point the scope.  Just like the last two nights, I downloaded fresh orbital elements and let the software calculate the position.  I also had the Minor Planet Center calculate the position using its own elements.  I downloaded a tabular listing of those positions versus time.  I then rolled the time forward on the software to that evening and checked the position of the asteroid against the listing that the MPC calculated.  They weren’t even close.  Although the software I use is normally right on, it looks as if the calculated positions are in error if the object is close and fast.  So I highlighted my position listings and waited for it to get dark and for the clouds to clear.

Strike three.

Hopefully,  I’ll remember this lesson and not have to learn it a third time for the next close pass.

Although most of the news coverage implied that the asteroid passed us, in reality it was ahead of the earth and the earth overtook it.  It was close enough to pass between the earth and our GPS satellites.  The task now is to get observations of 2011 MD as it departs to measure the changes in its orbit caused by the close pass to the Earth.

 Posted by at 20:18