Tag Archives: astronomers

Analemma, the Slender Figure Eight in the Sky


Myself 

By T. V. Antony Raj

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Definition of Analemma by Merriam-Webster: “A plot or graph of the position of the sun in the sky at a certain time of day (such as noon) at one locale measured throughout the year that has the shape of a figure 8; also : a scale (as on a globe or sundial) based on such a plot that shows the sun’s position for each day of the year or that allows local mean time to be determined.

Our Earth orbits around the Sun on an elliptical path. It also revolves around the Sun on a slant with an axial tilt of about 23.4 degrees. This leads to some interesting observational effects. One of these is the analemma, the apparent path traced by the Sun in the sky when observed at the same time of day over the course of a year.

Due to the Earth’s orbital eccentricity and its axial tilt, our Sun does not appear in the same position in the sky at the same time every day throughout the year. These two factors combine to generate the slender figure-eight, called analemma ( Greek “support”) curve.

So, the astronomers use this analemma diagram that shows the deviation of the Sun from its mean motion in the sky, as viewed from a fixed location on the Earth.

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Analemma on a globe (Source: analemma.com)

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The analemma diagram with the Sun’s path resembling a lopsided figure eight can often be found printed on globes of the Earth, usually somewhere over the Pacific Ocean where there is lots of room to print it.

The north–south component of the analemma is the Sun’s declination, and the east–west component is the equation of time. Most often, the diagrams of analemmas carry marks that show the position of the Sun at various closely spaced dates throughout the year. Analemmas with date marks are used for various practical purposes. Without date marks, they are of little use, except as decoration.

Earlier, prior to the 18th century, the term “analemma” referred to any tool or method used in the construction of sundials. Now, the term “analemma” is used in conjunction with sundials to convert between apparent and mean solar time.

Analemmas are photographed by keeping a camera at a fixed location and orientation and taking multiple exposures throughout the year, always at the same clock-time.

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Analemma posted by Giuseppe Donatiello

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The above image is a photo of an analemma posted by Giuseppe Donatiello.

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Analemma photo taken by Jack Fishburn in 1998–99.

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The above is an afternoon analemma photo taken in 1998–99 by Jack Fishburn in Murray Hill, New Jersey, USA. The Bell Laboratories building is in the foreground.

Although the term “analemma” is used to refer to the Earth’s solar analemma, it can be applied to other celestial bodies as well.

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Comet Hale-Bopp: The Most Widely Observed Comet of the 20th Century


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Myself By T.V. Antony Raj
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Image of comet Hale-BoppC/1995 O1 (Hale-Bopp), taken on 1997 April 04. The field shown is about 6.5° x 6.5°. At full resolution, the stars in the image appear slightly elongated, as the camera tracked the comet during the exposure. (Photo: E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria)
Image of comet Hale-Bopp (C/1995 O1), taken on 1997 April 04. The field shown is about 6.5° x 6.5°. At full resolution, the stars in the image appear slightly elongated, as the camera tracked the comet during the exposure. (Photo: E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria)

On July 23, 1995, two independent observers Alan Hale and Thomas Bopp in the United States discovered the comet Hale-Bopp. This comet formally designated C/1995 O1 was perhaps the most widely observed comet of the 20th century, the third largest comet in the last 500 years, and one of the brightest seen for many decades. It was visible to the naked eye for a record 18 months. The previous record holder, the Great Comet of 1811, officially designated C/1811 F1, was visible to the naked eye for around 260 days.

Dr. Alan Hale
Dr. Alan Hale

Astronomer Alan Hale was born in 1958 in Tachikawa, Japan, when his father was serving in the United States Air Force. Four months later his father got transferred to Holloman Air Force Base outside Alamogordo, New Mexico. Hale served in the United States Navy from 1976 to 1983. In 1980, he graduated from the U.S. Naval Academy. Next, he joined the Jet Propulsion Laboratory (JPL) and worked as an engineering contractor for the Deep Space Network until 1986. As a contractor, he worked in several projects involving spacecraft, including Voyager 2. After Voyager’s encounter with Uranus, he left JPL. He attended New Mexico State University in Las Cruces. In 1992, he earned his Ph.D. in astronomy.

Hale had spent hundreds of hours searching for comets without success. On July 23, 1995, while tracking known comets from his driveway in New Mexico he chanced on the comet co-named after him just after midnight. The comet with an apparent magnitude of 10.5 was near the globular cluster M70 in the constellation of Sagittarius. He checked and confirmed that there was no other deep-sky object near M70. Next, he consulted a directory of known comets and established that none of them was in that area of the sky he had observed. He then found the object moving relative to the background stars.

As a trained astronomer who had seen about 200 comets, Hale to register his finding sent an email to the Central Bureau for Astronomical Telegrams (CBAT) in Cambridge, Massachusetts, the clearing house for astronomical discoveries operating under the auspices of Commission 6 of the International Astronomical Union (IAU). A few hours later his effort was rewarded. His new comet was officially designated C/1995 O1. His name would also be attached.

But Alan Hale was not the only observer that night.

That very night, about 400 miles (644 kilometers) away, Thomas Bopp was observing star clusters and galaxies through telescopes with friends in the desert outside Phoenix, Arizona.

Thomas Bopp in 1997 (Photo: Ron Baalke)
Thomas Bopp in 1997 (Photo: Ron Baalke)

Amateur astronomer Thomas J. Bopp was born in 1949 in Denver, Colorado. Later he relocated with his family to Youngstown, Ohio, where he graduated from Chaney High School in 1967. He attended Youngstown State University in Youngstown, Ohio, and has lived in Tucson, Arizona since 1980. He is a Life member of the Mahoning Valley Astronomical Society (MVAS).

Bopp was a manager at a construction materials factory. He did not own a telescope. He too noticed some fuzzy object near M70 in the constellation of Sagittarius and pointed it out to his friend Jim Steven who owned the 70 inches telescope of Dubsoniano design he was using.

Bopp had never come across a comet. Jim looked at Bopp and said, “Tom, I think you have a comet.”

He knew he had to contact the Central Bureau for Astronomical Telegrams in Cambridge, but he did not have the address with him. So, he drove back home to get it.

In the wee hours he managed to send a Western Union telegram to the Central Bureau for Astronomical Telegrams in Cambridge where its arrival was greeted with bemusement. Brian Marsden, the leading voice on a committee that has the last say laughed. “Nobody sends telegrams anymore,” he commented. “I mean, by the time that telegram got here, Alan Hale had already e-mailed us three times with updated coördinates.”

However, the following morning, the comet was confirmed as a new entity and designated as C/1995 O1. The discovery was announced in International Astronomical Union circular 6187.

Sometimes weird things happened with when major comets appeared. According to a  report, 39 members of a California cult claimed they were departing on a spaceship that was trailing comet Hale-Bopp and ate their last meal before ritually committing mass suicide. For Thomas Bopp, the comet portended a loss. As comet Hale-Bopp reached its most spectacular point in the sky, his brother and sister-in-law who had been out photographing the comet were killed in a late night car crash. “This has been the best week of my life. And, the worst,” he lamented.

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A Near-earth Object, Asteroid 1998 QE2, Is Now Hurtling Towards Earth


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Myself . By T.V. Antony Raj
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Asteroid 1998 QE2 - 1

A near-earth object labeled Asteroid 1998 QE2, is now hurtling towards earth.

The asteroid about 1.7 miles (2.7 kilometers) or nine Queen Elizabeth 2 ship-lengths in size in length has the physical mass to potentially knockout life on Earth. However, we are safe as it is just flying by.

The orbit of asteroid 1998 QE2

On May 31, 2013, at 20:59 UTC (1:59 p.m. Pacific / 4:59 p.m. Eastern) this asteroid will pass within 3.6 million miles (5.8 million km) of Earth – about 15 times the distance to the Moon. While this may seem a great distance for the layman, in astronomical terms it is a mere stone’s throw away. This is the closest approach the asteroid will make to Earth for at least the next two centuries.

The Massachusetts Institute of Technology Lincoln Near Earth Asteroid Research (LINEAR) program near Socorro, New Mexico, discovered this asteroid on August 19, 1998. It is officially known as Asteroid 1998 QE2. It is not named in honor of Queen Elizabeth II, or after that 12-decked, transatlantic-crossing flagship for the Cunard Line. The name was assigned by the NASA-supported Minor Planet Center in Cambridge, Massachusetts, USA. This institute assigns each newly discovered asteroid a provisional designation starting with the year of first detection, along with an alphanumeric code showing the half-month it was discovered, and the sequence within that half-month.

Though this asteroid is not of much interest to those astronomers and scientists on the lookout for hazardous asteroids, it is of interest to those who dabble in radar astronomy and have a 230-foot (70-meter) or larger radar telescopes at their disposal.

Radar astronomer Lance Benner, the principal investigator for the Goldstone radar observations from NASA’s Jet Propulsion Laboratory in Pasadena, California said: “Asteroid 1998 QE2 will be an outstanding radar imaging target at Goldstone and Arecibo and we expect to obtain a series of high-resolution images that could reveal a wealth of surface features … Whenever an asteroid approaches this closely, it provides an important scientific opportunity to study it in detail to understand its size, shape, rotation, surface features, and what they can tell us about its origin. We will also use new radar measurements of the asteroid’s distance and velocity to improve our calculation of its orbit and compute its motion farther into the future than we could otherwise.”

Asteroid 1998 QE2

Asteroids come in various sizes and shapes: dog bones, bowling pins, spheroids, diamonds, muffins, potatoes, etc. Between May 30 and June 9, radar astronomers using NASA’s 230-foot-wide (70 meter) Deep Space Network antenna at Goldstone, California, and the Arecibo Observatory in Puerto Rico, are planning an extensive campaign of observations. The two telescopes with complementary imaging capabilities will enable astronomers to study 1998 QE2 and what it looks like during its brief flyby.

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Asteroid 2012 DA14 Will Flyby on February 15, 2013


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Myself By T.V. Antony Raj

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Diagram of 2012 DA14 passing the Earth on 15 February 2013
Path of 2012 DA14 passing the Earth on 15 February 2013

The small near-Earth asteroid named 2012 DA14 discovered on February 23, 2012, by the OAM Observatory, La Sagra in Spain with an estimated diameter of about 45 meters (about half the size of a football field) weighing about 130,000 metric tons mass probably made of stone in contrast to metal or ice is now hurtling towards the earth. It will pass within about 3.5 Earth radii of the Earth’s surface inside the geosynchronous satellite ring, located about 35,800 kilometers above the equator.

UPCOMING CLOSE APPROACHES TO EARTH - 2

Tomorrow, February 15, 2013, when it passes within 17,200 miles (28,000 kilometers) of Earth, it will not be visible to the naked eye, but will be within range of small telescopes and solidly mounted binoculars, used by experienced observers who have access to appropriate star charts. Here is a note from NASA about the asteroid’s visibility:

On [February 15, 2013], the asteroid will travel rapidly from the southern evening sky into the northern morning sky with its closest Earth approach occurring about 19:26 UTC when it will achieve a magnitude of less than seven, which is somewhat fainter than naked eye visibility. About 4 minutes after its Earth close approach, there is a good chance it will pass into the Earth’s shadow for about 18 minutes or so before reappearing from the eclipse. When traveling rapidly into the northern morning sky, 2012 DA14 will quickly fade in brightness.

Astronomical observatories with their large telescopes would record images of the asteroid, and some observatories will be broadcasting them live online.

Slooh Space Camera will cover the asteroid’s near-approach on Friday, February 15, Slooh to cover live from the Canary Islands with the broadcast team, with several live shows free to the public starting at 6 p.m. PST / 9 p.m. EST / 02:00 UTC (2/16), accompanied by real-time discussions with Slooh Space Camera’s Paul Cox, astronomer and author Bob Berman, and Prescott Observatory manager Matt Francis. Viewers can watch live on their PC or iOS/Android mobile device.

Clay Center Observatory will be offering real-time high-definition video, from 22:00 UTC (6 p.m. EST) February 15 until 8:00 UTC (4 a.m. EST) on February 16. The video feed can be freely accessed worldwide via Clay Center Observatory’s Ustream channel. The observatory has also set up a countdown clock to show how much time remains until the tracking begins.

Bareket Observatory in Israel will be providing a free live webcast of the close approach of asteroid 2012 DA14 using a remote telescope coupled with a cooled CCD camera on February 15 from 21:00 – 22:30 local time (19:00 – 20:30 UTC, or 2 p.m. – 3:30 p.m. CST).

Virtual Telescope Project, which calls itself “the most active facility in the world in astronomical science and education,” will also be following 2012 DA14 on February 15, 2013.

Will anything happen when asteroid 2012 DA14 comes close to Earth? Nothing. According to Paul Chodas, Jon Giorgini and Don Yeomans of NASA/JPL Near-Earth Object Program Office the asteroid will not impact the Earth on February 15, 2013.

The asteroid will have no effect on the tides. It will not cause volcanoes to erupt. It will not trigger earthquakes and tsunamis. Though the asteroid will just hurtle closely past Earth only 17,000 miles away – within the orbits of geosynchronous satellites, most of us will not see it, and we will not be aware of it at all.

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A Near-Earth Object, Asteroid 2012 DA14 Now Hurtling Towards Earth


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Myself By T.V. Antony Raj
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Comets and asteroids that enter the Earth’s neighborhood nudged by the gravitational attraction of nearby planets are known as near-Earth Objects (NEOs).

One such near-Earth asteroid named 4179 Toutatis formerly known as 1989 AC was discovered by Christian Pollas on January 4, 1989, at Caussols, France. On
December 12, 2012, this asteroid with a shape of a “malformed potato” tumbled through space like a fumbled football, within 4.3 million miles from Earth.

UPCOMING CLOSE APPROACHES TO EARTH - 2

Another near-Earth asteroid discovered on February 23, 2012, by the OAM Observatory, La Sagra in Spain with an estimated diameter of about 45 meters (about half the size of a football field) weighing about 130,000 metric tons mass probably made of stone in contrast to metal or ice is now hurtling towards the earth.

Diagram of 2012 DA14 passing the Earth on 15 February 2013
Diagram of 2012 DA14 passing the Earth on 15 February 2013

On February 15, 2013, this asteroid labeled 2012 DA14 will pass within about 3.5 Earth radii of the Earth’s surface inside the geosynchronous weather and communication satellites ring, approximately 35,800 kilometers above the equator.

Even though asteroids like 2012 DA14 fly past Earth almost every 40 years they impact with our planet only every 1200 years or so. Don Yeomans, Paul Chodas, and Jon Giorgini of NASA/JPL Near-Earth Object Program Office after predicting the asteroid’s path have declared that according to their observations, there is no chance that the asteroid might be on a collision course with the Earth, and it will safely fly past Earth’s outer ring of satellites on February 15.

“Since regular sky surveys began in the 1990s, we’ve never seen an object this big gets so close to Earth,” Don Yeomans said.

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Asteroid 2012 DA14 Will Pass the Earth on February 15, 2013


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Myself By T.V. Antony Raj

.UPCOMING CLOSE APPROACHES TO EARTH

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On February 23, 2012, the OAM Observatory, La Sagra in Spain discovered a near-earth asteroid with an estimated diameter of about 45 meters and about 130,000 metric tons mass hurtling towards the earth. On February 15th, 2013, this asteroid named 2012 DA14 will pass within about 3.5 Earth radii of the Earth’s surface inside the geosynchronous satellite ring, located about 35,800 kilometers above the equator. According to Paul Chodas, Jon Giorgini and Don Yeomans of NASA/JPL Near-Earth Object Program Office the asteroid will not impact the Earth on February 15, 2013.

Diagram of 2012 DA14 passing the Earth on 15 February 2013
Diagram of 2012 DA14 passing the Earth on 15 February 2013. – Author: NASA/JPL Near-Earth Object Program Office.

As per calculations, on February 15, 2013, the distance between the asteroid and the Earth will be 0.09 Lunar Distance (35,000 kilometers; 21,000 miles) and travel rapidly from the southern evening sky into the northern morning sky. Its closest Earth approach to Earth would occur at 19:26 UTC achieving magnitude of less than seven; somewhat fainter than naked-eye visibility. Four minutes later 2012 DA14 after passing into the Earth’s shadow for 18 minutes it will reappear from the eclipse, travel swiftly into the northern morning sky and would disappear.

Note: LD = Lunar Distance = ~384,000 kilometers (238,900 miles) .

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