Just Passing By—For Now

Asteroid 99942 Apophis made a relatively distant pass by Earth on 5 March. It will be back. This animation shows the trajectory of  the asteroid as it flies safely past Earth on 13 April, 2029. Earth’s gravity will slightly deflect the trajectory as the 340-meter-wide Near-Earth Object comes within 32,000 kilometers of the Earth’s surface. The motion has been sped up by a factor of 2,000. Recent observations and refined calculations show that 99942 Apophis should not hit the Earth for at least a century.

Video Credit: NASA / JPL

A Coming Attraction

On 13 April, 2029, a dot of light will streak across the sky getting brighter and going faster. At one point, it will travel more than the width of the full Moon within a minute, and it will get as bright as the stars in the Little Dipper. But it won’t be a satellite or an airplane. It will be a 340-meter-wide near-Earth asteroid called 99942 Apophis. It will cruise past Earth roughly 31,000 km above the surface. That’s inside the orbits of geostationary satellites. This animation shows the distance between the Apophis asteroid and Earth at the time of the asteroid’s closest approach. The blue dots are man-made satellites in orbit our planet, and the pink dot moving diagonally near the Earth represents the International Space Station.

Animation Credits: Marina Brozović / JPL

Just Passing By

Today’s close approach by the large, near-Earth asteroid 2003 SD220 has provided astronomers an opportunity capture detailed radar images of its surface and shape and to refine our knowledge of its orbit.

The asteroid will fly safely past Earth at a distance of about 2.9 million km. That will be the asteroid’s closest approach in more than 400 years. In 2070, the asteroid will get a bit closer, but still remain a safe distance off.

These two radar images were obtained on the 18th and 19th by coordinating observations with the Arecibo Observatory’s 305-m antenna in Puerto Rico and the National Science Foundation’s 100-m Green Bank Telescope in West Virginia. The radar images show that the asteroid is at least 1.6 km long.

Image Credits: NASA / Arecibo / USRA / UCF / GBO / NSF

A Near Earth Asteroid

NearEarthAsteroidThe greenish-yellow dot in the upper left is the potentially hazardous near-Earth object 1998 KN3 moving past a cloud of dense gas and dust near the Orion nebula in the far, far background. NEOWISE, the asteroid-hunting portion of the Wide-field Infrared Survey Explorer, or WISE, mission, took this infrared picture. Because near-Earth asteroids are warmed by the Sun to roughly room temperature, they glow brightly at the infrared.

Infrared light from asteroids is used to measure their sizes. Combined with visible-light observations, that data can also measure the reflectivity of their surfaces. The WISE data reveal that this asteroid is about 1.1 km in diameter and reflects only about 7 percent of the visible light that falls on its surface. It is relatively dark.

In this image blue denotes shorter infrared wavelengths and red, longer. Hotter objects emit shorter-wavelength light; they appear blue. Stars with temperatures of thousands of degrees are blue. The coldest gas and dust are red. The asteroid appears greenish-yellow in the image because it is about room temperature—cooler than the stars, but warmer than the dust.

Image Credit: NASA


This animation shows the first four year’s progress of NASA’s Near-Earth Object Wide-field Survey Explorer (NEOWISE) mission following the repurposing of the WISE satellite in December, 2013. Green dots represent near-Earth objects. Gray dots represent all other asteroids which are mainly in the main asteroid belt between Mars and Jupiter. Yellow squares represent comets.

Image Credit: NASA

3200 Phaethon

This animation was assembled from radar images of near-Earth asteroid 3200 Phaethon taken by astronomers at the National Science Foundation’s Arecibo Observatory last week. Observations of Phaethon were conducted at Arecibo from 15 to 19 December, 2017. At time of closest approach at about 11:00 UTC on the 16th, the asteroid was about 1.8 million km away (about 4.6 times the distance from Earth to the Moon). That should be the Earth’s  closest encounter with the asteroid until 2093.

The Arecibo radar images show that Phaethon has a diameter of about 6 km. That’s about a km larger than previous estimates. Given it’s size and near-Earth orbit, Phaethon is the second largest near-Earth asteroid classified as “Potentially Hazardous.”

Other Phaethon facts: It was the first asteroid discovered by a spacecraft—The Infrared Astronomical Satellite in 1983. It’s the parent body of the Geminids meteor shower. It has a highly elliptical orbit which brings it closer to the Sun than any other named asteroid. The orbit extends from beyond Mars’ to inside Mercury’s.

Image Credit: Arecibo Observatory / NSF / NASA

A Close Encounter

Asteroid 2012 TC4 flew by the Earth during the night of 11/12 October, 2017. This video was recorded at 20:54 UTC on the 11th by astronomers Peter Schlatter and Dominik Bodenmann working at the ZIMLAT telescope at the Swiss Optical Ground Station and Geodynamics Observatory operated by the Astronomical Institute of the University of Bern (AIUB) while the 10 to 20 m diameter asteroid was approaching the Earth. It made its closest approach at 05:41 UTC on the 12th, less than 44,000 km away—much closer than the Moon. Watch the asteroid move from left to right across the upper half of the reverse video image.

Video Credit: AIUB

A Close Encounter

This animation shows flyby of asteroid 2012 TC4 as it passes near Earth on Columbus Day, 2017. We can’t yet predict exactly how close it will approach, but the data from previous observations suggests it will come no closer than 6,800 km from Earth’s surface. The current estimates of the asteroid’s size puts it in the 10 to 30 m range.

Animation Credit: NASA

Jerry Pournelle and Larry Niven were unavailable for comment.

2014 AA

2014AAEarly Wednesday morning, the Catalina Sky Survey near Tucson, Arizona, collected a single track of observations with an immediate follow-up on what was probably a very small asteroid—2 or 3 meters across—on a potential impact trajectory with Earth. If it was a tiny asteroid on an Earth-impacting trajectory, it should have entered the Earth’s atmosphere between 1900 UTC Wednesday and 1400 UTC Thursday. It is unlikely asteroid 2014 AA would have made to the ground intact.

Image Credit: CSS/LPL/UA

An Near-Earth Asteriod

On 9 November, 2012, Asteroid 2005 YU55 passed by the Earth. In this video the asteroid moves through the field of view of Swift‘s Ultraviolet/Optical Telescope (UVOT) shortly after the space rock made its closest approach. The video plays on a background image from the Digital Sky Survey that shows the same region, which lies within the Great Square asterism of the constellation Pegasus (times are UTC).

[youtube http://www.youtube.com/watch?v=hAJxzMtIZHI]

Video Credit: NASA