Apophis Archives

December 27, 2009December 24, 2015 by Jerry Coffey

Celestial Body

[/caption]The term celestial body is as expansive as the entire universe, both known and unknown. By definition a celestial body is any natural body outside of the Earth’s atmosphere. Easy examples are the Moon, Sun, and the other planets of our solar system. But those are very limited examples. The Kuiper belt contains many celestial bodies. Any asteroid in space is a celestial body. So, what do you write about with such a broad topic? How about a sampling of five of my favorites and leave it at that for now? Which five, though. Well, let’s cover Ceres, the Kuiper belt, the asteroid Cruithne, Achernar, and Apophis.

Ceres is a celestial body that is by far the largest and most massive asteroid in the belt between Mars and Jupiter. It is approximately the size of Texas or 975km x 909 km with a mass of 9.5×10²⁰. It actually represents 1/3 of all of the mass of the asteroid belt. It has enough mass for self gravity which is a major requirement to be considered a dwarf planet. It revolves around the sun every 1679.819 days with a very small axial tilt. The surface is relatively warm. The high temperature is thought to be in the neighborhood of -38°C(235 K). Ceres has a visual brightness magnitude of +6.9 to +9. When it is at the brightest point possible, Ceres is nearly bright enough to be seen with the naked eye. It can be seen with binoculars whenever it is above the horizon on a completely dark night.

The Kuiper belt contains many a celestial body. It is actually a disk-shaped region in the outer solar system lying beyond the orbit of Neptune and extending to a distance of about 50 astronomical units, containing thousands of small icy bodies, some of which are on highly elliptical orbits, periodically visiting the inner solar system as comets. It is thought to be a collection of the remnants of the formation of the solar system. Who knows what may be found when we are able to send spacecraft to its edges?

As a celestial body, the asteroid Cruithne is sort of small and indistinct until you consider that it is locked in a 1:1 orbit with the Earth. The asteroid is sometimes referred to as the Earth’s second moon. It is not a true moon because the Earth’s gravity does not effect it nor does its effect the Earth. Cruithne’s nearest pass to Earth is .1 AU (40 moon lengths), although right now it never comes closer than .3 AU. The asteroid sort of runs like a corkscrew around the Earth while both are revolving around the Sun. The asteroid Cruithne is in a normal elliptic orbit around the Sun. Its revolution around the Sun, approximately 364 days at present, is almost equal to that of the Earth. Because of this, Cruithne and Earth appear to follow each other in their paths around the Sun.

The celestial body Achernar is a bright, blue, B3-type star of six to eight solar masses lying approximately 144 light years away. It is classified as a dwarf, but it is 3,000 times more luminous than our Sun. It is in the deep southern sky and never rises above 33°N. Achernar is best seen from the southern hemisphere in November; it is circumpolar below 33°S. Achernar spins so quickly that is spherical in shape. The distance along its equator is 50% greater than its polar diameter. It is the brightest star in the Eridanus constellation. It is also the 9th brightest star in the night sky. Of the 10 brightest stars, other than our Sun, it is the hottest and bluest.

The celestial body Apophis is one of the most intriguing, to me. It is the stuff that many sci-fi legends have been based on. Apophis is most famous for the stir it caused in 2004. The asteroid was discovered on its way towards the Earth and was predicted to have a 2.7% chance of impacting the Earth. That in and of itself is not significant. Objects impact the Earth on a yearly basis. The size of Apophis was the major concern. Even a small chance that an asteroid the size of a small town hitting the Earth rightly caused a large commotion. It achieved the highest score ever on the Torino scale and it stayed on an elevated level for longer than any other asteroid ever has. It was eventually studied enough to know that it would not hit the Earth in 2004. The asteroid will pass again in 2029. Scientists predict that it will not hit the Earth, but it may pass through a gravitational keyhole that could alter its orbit enough that it could impact in 2036. The chances are slight, but real. Even if it doesn’t hit a keyhole in 2029 it will return every seven years and may pose a serious threat in the future. Scientists have proposed that Apophis be nudged out of its present orbit into an orbit that takes it further from the keyhole. NASA scientist David Morrison says, “After 2029, the deflection would have to be vigorous enough to miss not just a tiny keyhole but the much larger target of the Earth itself. And such a deflection is far beyond present technology for an asteroid this large.”.

Many things can make a celestial body interesting. Everyone has their favorites. Mine happen to be the five I have listed. Each can be further researched here on Universe Today. Follow these links to find what you need: Ceres, the Kuiper belt, the asteroid Cruithne, Achernar, and Apophis. Astronomy Cast offers a good episode about the mind-boggling possibility of multiple universes. Here’s a list of the 10 brightest stars.

Sources:
http://planetary.org/explore/topics/asteroids_and_comets/ceres.html
http://userpages.umbc.edu/~gwilson/kuiper.html
http://www.astro.uwo.ca/~wiegert/3753/3753.html
http://en.wikipedia.org/wiki/Achernar
http://neo.jpl.nasa.gov/apophis/

October 7, 2009December 24, 2015 by Nancy Atkinson

Apophis’ Odds of Earth Impact Downgraded

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NASA scientists have recalculated the path of the large asteroid Apophis, significantly downgrading the odds of it hitting Earth. Using new information, the refined path indicates a 1 in 250,000 chance of impact in 2036, reduced from the 1 in 45,000 odds calculated earlier. The asteroid is expected to make a record-setting — but harmless — close approach to Earth on Friday, April 13, 2029, when it comes no closer than 18,300 miles above Earth’s surface.

The new information provided a more accurate glimpse of 2036 Apophis’ orbit well into the latter part of this century. Among the findings is another close encounter by the asteroid with Earth in 2068 with chance of impact currently at approximately 1 in 333,000. As with earlier orbital estimates where Earth impacts in 2029 and 2036 could not initially be ruled out due to the need for additional data, it is expected that the 2068 encounter will diminish in probability as more information about 2029 Apophis is acquired.

Initially, Apophis was thought to have a 2.7 percent chance of impacting Earth in 2029. Additional observations of the asteriod ruled out any possibility of an impact in 2029.

The Apophis asteroid is approximately the size of two-and-a-half football fields.

“The refined orbital determination further reinforces that Apophis is an asteroid we can look to as an opportunity for exciting science and not something that should be feared,” said Don Yeomans, manager of the Near-Earth Object Program Office at JPL. “The public can follow along as we continue to study Apophis and other near-Earth objects by visiting us on our AsteroidWatch Web site and by following us on the @AsteroidWatch Twitter feed.”

The new data were documented by near-Earth object scientists Steve Chesley and Paul Chodas at NASA’s Jet Propulsion Laboratory. A majority of the data that enabled the updated orbit of Apophis came from observations made by Dave Tholen and collaborators at the University of Hawaii’s Institute for Astronomy in Manoa. Tholen pored over hundreds of previously unreleased images of the night sky made with the University of Hawaii’s 88-inch telescope, located near the summit of Mauna Kea.

Tholen made improved measurements of the asteroid’s position in the images, enabling him to provide Chesley and Chodas with new data sets more precise than previous measures for Apophis. Measurements from the Steward Observatory’s 90-inch Bok telescope on Kitt Peak in Arizona and the Arecibo Observatory on the island of Puerto Rico also were used in Chesley’s calculations.

“Apophis has been one of those celestial bodies that has captured the public’s interest since it was discovered in 2004,” said Chesley. “Updated computational techniques and newly available data indicate the probability of an Earth encounter on April 13, 2036, for Apophis has dropped from one-in-45,000 to about four-in-a million.”

The science of predicting asteroid orbits is based on a physical model of the solar system which includes the gravitational influence of the sun, moon, other planets and the three largest asteroids.

NASA detects and tracks asteroids and comets passing close to Earth using both ground and space-based telescopes. The Near Earth-Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterizes a subset of them and plots their orbits to determine if any could be potentially hazardous to our planet.

Source: NASA

April 19, 2008December 24, 2015 by Fraser Cain

How Big is Apophis?

Question: How Big is Apophis?

Answer: In case you haven’t heard, Asteroid 99942 Apophis is a near Earth asteroid that astronomers think will make a close flyby to the Earth in 2029. When its trajectory was first calculated back in 2004, it had one of the closest visits to Earth astronomers had seen, and had a 2.7% chance of hitting the Earth.

But follow-up observations brought that risk down to 1 in 45,000. Right now, astronomers think that Apophis is essentially no risk to the Earth. In April, 2008 media reported that a 13-year old German student had caught a math mistake made by NASA, and the risk of an Earth strike was actually 1-45. This later turned out to be a hoax.

Because of its close approach to Earth, space advocacy societies, including the Planetary Society think that the Apophis asteroid would make an ideal target for a human mission, and allow engineers to test out strategies for moving asteroids away from dangerous Earth-crossing orbits.

So back to the original question, how big is Apophis? The best estimate puts it at 270 meters (885 feet across), and it has a mass of 2.1 x 10¹⁰ kg. To give you a sense of scale, the Eiffel Tower in Paris is 324 meters tall.

But now you know its mass and size, you’re probably wondering: what would happen to the Earth if it struck? NASA estimated that a strike by Apophis would release the equivalent of 880 megatons of energy. Just as a comparison, the object that carved out Meteor Crater in Arizona probably released 3-10 megatons of energy.

If Apophis struck land, it would flatten thousands of square km of land, killing millions of people if it hit a densely populated area. But it wouldn’t cause the kinds of long term climate destruction that 1 km and larger asteroids can do. If it hit an ocean, it would create devastating tsunamis in all directions.

Here’s an article explaining techniques that might be used to move an asteroid. And here’s NASA’s official page on Apophis.