Surprise asteroid to give Earth a Halloween flyby

Posted: October 19, 2015 by oldbrew in Astronomy, News

Just passing by [image credit :]

Just passing by [image credit :]

No need to duck, but an asteroid designated 2015 TB145 will pass by the Earth at around 1.3 lunar distances (approximately 310,000 miles or about 499,000 km) on October 31 this year, reports Gizmag.

Estimated to be anywhere between 280 to 620 m (918 to 2,034 ft) in diameter and traveling in excess of 126,000 km/h (78,293 mph), the asteroid was discovered less than two weeks ago using the Pan-STARRS array in Hawaii and is the largest object to so closely approach our planet in recent times.

Before you start panicking, NASA says that the object is expected to safely pass by the Earth and is following an eccentric and high-inclination orbit, which may help explain why it was not discovered until October 10 of this year.

Much closer than a “near miss” of 3.1 lunar distances by another recent asteroid, 2004 BL86, 2015 TB145 is of a similar size or greater than that object, but without an accompanying moon. Nevertheless, this now qualifies as the latest known close encounter, after 2004 XP14 in July 2006 at 1.1 lunar distances, and until the asteroid 1999 AN10 swings by Earth at less than one lunar distance sometime in August 2027.

Full report: Surprise asteroid to give Earth a Halloween flyby – Gizmag

  1. […] Source: Surprise asteroid to give Earth a Halloween flyby […]

  2. Scute says:

    This is a very unusual asteroid. I check the NEO page at JPL every day and select interesting ones about once a month (1 in every 100 or so) to characterise their orbit in relation to the Earth. I send them off to Frank Davis to do a model run on his orbit programme. I always check the minimum orbital intersection distance (MOID) rather than the close approach distance. This is because Frank and I believe it’s highly possible that asteroids, especially larger ones can have small companions orbiting in their wake. So even if the asteroid goes through the MOID ahead of us, we may hit companions as we go through the MOID several hours later. The MOID is where the stream of trailing rocks or ‘rock train’ will be passing through. The close approach distance of the asteroid is always somewhat more than the MOID distance so the MOID is the key. Frank sets up rock clouds, offset from the main orbit so that they hit the Earth and then from there he can establish the radiant and trajectory of any related meteor anywhere in the world.

    2015TB145 has a MOID of about 280,000km, just inside our usual cutoff for a 300,000km radius from the Earth’s orbit. It’s especially interesting being so big and, we believe, more likely to have companions.

    2015TB145 has high eccentricity and a high aphelion meaning it doesn’t catch us up slowly like other asteroids in fatter, lower orbits. It hurtles in at us. Most geocentric radiant velocities are around 6-20 km/sec. This one is 35 km/sec, the third highest I’ve ever seen (highest: 38km/sec).

    Frank has already established that the close approach of 2015TB145 is at 17:02 UTC on the 31st October and the closest approach of the rock train is at 19:48 that day. He has offset a rock around 300,000 km from the rock train and it hits the Earth at 19:20 on the 31st.

    300,000km might seem a lot but it is only about 1/1000th of the semimajor axis of the orbit of the asteroid. We shall be looking out for meteor reports at this date and time and a few hours either side. Not just any meteor but ones arriving at 37km/sec and from a very specific radiant causing a predictable altitude and azimuth anywhere on the planet (that related fragments can physically reach).

    Being at 37km/sec they should produce very different meteors from normal. If steep, they should produce extremely bright but short flashes. If grazing, they will be fast, bright and very sustained.

    Steep hits will generally come through the morning skies and grazers will be towards the just-past-midnight line and late afternoon line.

    It should be said that the evening times given above are the UTC times of arrival, but because they can hit anywhere in the world, the UTC arrival time can be morning, evening or nighttime for other places. Also, the atmospheric trajectory speed is 2km/sec faster than the cosmic radiant speed due to gravity well speed-up.

  3. michael hart says:

    phew, that was a close one.
    Time for less global-warming watching and more asteroid watching?
    Just kidding. They both seem the same.

  4. oldbrew says:

    Scute: interesting stuff. Maybe my ‘no need to duck’ comment was a bit complacent 😉

  5. Scute says:


    Apologies- a small correction. The steep ones will be around the 3AM hour line and the grazers, late evening and late morning. Of course, that’s if they come at all! I should have made that clear.

  6. Frank Davis says:

    If there’s a rock train behind it, we’ll be nearest it at about 19:30 UT on 31 Oct 2015.

    And if any rocks (exiting top right) hit the Earth, they’ll be centred on the Indian ocean, and radiating from there.

    Blue lines are ground tracks, red lines are air paths.

  7. oldbrew says:

    Frank D: where’s the link?

  8. Frank Davis says:

    Sorry, the image didn’t appear.

  9. Frank Davis says:

    The period of (2015 TB145) is about 3.1 years. So the last time it came round was in 2012. So I wondered if there’d been any fireballs around 31 Oct 2012. A Google search immediately turned up this

    Meteor explodes above Alabama, 30 October 2012, NOT a Taurid or so-called ‘Hallowe’en Fireball’

    This was very near the time of (2015 TB145) theoretical rock train closest approach. I wondered if the 2012 Alabama fireball could have been from that rock train. So I checked it out. And it could have been.

    The recorded track from west to east is shown on the map. And one of my (2015 TB145) companions is landing not far away, also coming from west to east, on a slightly more northerly trajectory.

    Not proof of anything, of course. Just proof that it could have been.

  10. […] Source: Surprise asteroid to give Earth a Halloween flyby […]

  11. carol smith says: are now calling it a comet – it is apparently travelling very fast. One cannot help but think of Clube and Napier’s hypothetical comet that also had an orbit of between 3 and 4 years, in their two books and numerous astronomical articles. Napier has recently dated its arrival back into the Late Pleistocene period which is of course conjectural. They of course had it breaking up into small pieces in the fourth and third millenniums BC – and as such remnant pieces might still be out there orbiting around.