Global warming - also in Pluto?

The changes occur as Pluto moves away from the Sun, but the trends are much more complex than expected

Pluto may be experiencing a trend of surface warming and atmosphere cooling, planetary scientists say. The astronomers estimated this based on data obtained during a stellar eclipse - which occurred when Pluto blocked the light of the star P126A.

The last time Pluto produced a stellar eclipse was in 1998. However, the star's light reappeared so quickly that nothing about Pluto could be learned from it. In July of this year, the star's light dimmed slowly as Pluto passed in front of it.

By studying the starlight, scientists can estimate the density, pressure and temperature of Pluto's thin atmosphere.

"Over the last 14 years there have been some changes," says Mark Bowie of the Lovell Observatory in Arizona. "Pluto's atmosphere is undergoing global cooling, while other data show that the surface has warmed slightly."

The changes are occurring as Pluto moves away from the Sun, but the trends are much more complex than expected," says Bowie, who along with James Elliott of MIT reported the findings last week. Pluto has an extremely elliptical orbit and moves away from the Sun towards the furthest point in its orbit.

The astronomers' theory predicts that during this time, the star's atmosphere will freeze for a period of over a hundred years. This Thursday, Pluto is again going to pass in front of another star. Such eclipses now occur more often because Pluto now moves in line with the central plane of the Milky Way where the density of stars is higher.

We must set out quickly, before Pluto freezes and disappears from sight

Kenneth Chang New York Times

Image: Johns Hopkins University

Diagram of the "New Horizons" spacecraft on its way to Pluto. The American spacecraft is scheduled to be launched in 2006 and reach Pluto in 2016

In 1991, the US Postal Service issued a series of stamps, commemorating the American research missions in space. The stamp for Pluto consisted of an image of a gray disc, with a kind of apology underneath: "not yet explored".

Pluto, the smallest and most distant of the solar system's planets, is still the only planet that has yet to be visited by a spacecraft. In the 72 years since Clyde Tombaugh, an astronomer at the Lowell Observatory in Flagstaff, Arizona, spotted Pluto as a point of light in one of his photographs, Pluto has remained just that: a point of light. Ground telescopes are not powerful enough to pick up any details of its surface.

But with a little ingenuity, astronomers learned a lot just by looking hard at the bright spot. The specific colors in the light indicate the composition of the surface and its thin atmosphere. By measuring how it brightened and darkened during eclipses with its moon, Charon, scientists created a rough map of its surface.

Pluto has recently been the subject of controversy between those who argue that it should be counted among the celestial objects of the Kuiper Belt - a ring of icy rocks beyond Neptune's orbit that have failed to merge into a larger planet - and those who attack any attempt to devalue its status as the ninth planet. This dispute ultimately converges on the question of what a planet is - a seemingly clear concept, but without a precise definition.

Beyond semantics, planetary scientists care about Pluto because, like comets, it may be made of many of the same materials that made up the primordial solar system.

Despite its distance from the Sun - about 4.7 billion km - Pluto is not just a frozen and unchanging ball of ice. The polar ice caps are expanding and thinning over the decades. There are suspicions that with its atmosphere becoming thinner, the winds there will reach speeds of hundreds of kilometers per hour.

Predictions in the shadow of Pluto

Astronomers who observed Pluto's eclipses in July and August are having trouble determining whether the planet's atmosphere has warmed or cooled since the previous observation, made 14 years ago

5.9.2002

By: Kenneth Chang New York Times

Photo: NASA

Pluto (center) and its moon, Charon, as photographed by the Hubble Space Telescope. Astronomers agree that the planet's atmosphere appears surprisingly active

The weather forecast for Pluto is still unclear. Astronomers from the Lowell Observatory in Arizona and the Massachusetts Institute of Technology (MIT) say that the atmosphere on the planet has cooled by 10 to 20 degrees Celsius in the last 14 years, that the surface has probably warmed slightly, and that a low layer of smog that floated in the air has dissipated. French astronomers dispute them. According to them, the air has cooled but slightly and the smog layer still exists in the planet's atmosphere.

These estimates seem to inspire no more confidence than the American tradition of "Marmite Day", starting on February 2nd. (According to tradition, on this day, the Marmite peeks out of its burrow to check if its image casts a shadow. If it does not cast a shadow, it is a sign that the day is cloudy - that is, spring has arrived. If its image casts a shadow, it is a sign that winter will last six more weeks, and the Marmite returns to its burrow). Even in the case of Pluto, all the findings are based on observations of shadows.

Pluto, which is at a distance of 4.5 billion km from the Earth and is getting further and further away from it, is nothing more than a point of light on the screens of telescopes placed on the Earth. Astronomers can infer something about the planet's atmosphere only when, thanks to a celestial coincidence, Pluto passes in front of a distant star and casts a faint shadow on Earth.

This happened once in 1988 and at the end of the 14 year wait - twice last summer. The dimming of the light from the hidden star indicates the degree of compression and temperature of Pluto's atmosphere. If Pluto is devoid of air, the star will suddenly disappear. But the atmosphere acts as a lens: it bends the starlight around the planet and causes the dimming to occur gradually. In the eclipse of the star in 1988, its light dimmed at a steady rate, until it reached 40% of its normal brightness, and then quickly disappeared.

The dimming rate indicated that most of Pluto's atmosphere, which reaches up to a height of 160 km above the planet's surface, is fairly uniform in temperature: from minus 173 degrees Celsius to minus 162 degrees.

The sudden disappearance shows that there is a layer 24 to 56 km thick on the surface, consisting of either a foggy mist that swallows the light, or colder and much more compressed air, which distorts the light until it is not visible from the earth. From other measurements, researchers know that the temperature of the surface on Pluto is minus 234 degrees Celsius.

On July 20, Pluto stood in front of the star,P126A But cloudy weather thwarted the efforts of all researchers, except for two teams of observers in northern Chile. Astronomers were luckier on August 20, when Pluto obscured another star, .P131.1 The eclipse was captured by a large number of large observatories in Hawaii and the western United States.

Dr. Mark Bowie, an astronomer at the Lowell Observatory who made one of the two successful observations in July in Chile, said that the star's light had dimmed in a way that indicates a sharp drop in Pluto's temperature compared to 1988. According to him, there were also no signs of the haze layer or the cold air, meaning The thing that the layer has shrunk by at least 24 km, and maybe disappeared altogether. "We have surprises at the most basic level," Bowie said.

But the team that made the other successful observation in Chile announced that according to their analysis the temperature of Pluto's atmosphere is still minus 173 degrees. "We haven't seen many changes since '88," said team leader Dr. Bruno Sicardi, an astronomer at the Paris Observatory. "I don't understand how they could conclude anything about changes." In addition, Cicardi said, measurements from the August eclipse at the Canada-France-Hawaii telescope on Mauna Kea in Hawaii showed that the haze layer was still present.

Bowie and his research partner, Dr. James Elliott, an astronomer fromMIT The data from August have not been analyzed yet. Several telescopes in Hawaii, the Lick Observatory in California, and the Lowell Observatory then observed the eclipse in different wavelengths of visible and infrared light. A clearer picture of Pluto should be obtained within a few months. The infrared measurements will clarify whether it is a layer of cold air or of haze in the lower atmosphere. Cold air distorts all wavelengths equally. Haze absorbs visible light, but allows infrared light, which has longer wavelengths, to pass through. "This is also the reason why sunsets are red," said Dr. Sicardi.

According to Dr. Elliott, for now none of the explanations are satisfactory. For smog to cause the dimming observed in 1988, its particles must be quite large - too large to remain in Pluto's thin atmosphere. Computer models also fail to create an atmosphere where there has been such a sharp drop in temperature within 14 years. "There was no physical model that could explain what we saw in '88," Eliot concluded.

Astronomers agree that the planet's atmosphere appears surprisingly active, given the minimal amount of sunlight reaching it. In the August eclipse, Sicardi said, the star's light suddenly brightened for a few seconds, about 10 times its previous brightness, and then faded again — a phenomenon indicative of pockets of colder air. "In order to create such variations, dynamic activity is necessary," he said. "Energy is needed to maintain these buildings."

It is not clear how the new findings fit in with predictions that Pluto's cooling atmosphere will freeze and collapse within 20 years. This mainly depends on the temperature of the surface, which determines how much of the frozen methane and nitrogen will turn into gas. Bowie said that his computer models indicate that the surface may actually have warmed by a tenth of a degree since 1988. The surface has darkened - perhaps due to the retreat of glaciers - and this allows for a higher rate of heat absorption. But Pluto is moving away and cooling, and the trend is expected to reverse at some point. Astronomers do not know when the stars will provide another opportunity to observe Pluto's atmosphere and what will change by then.

The surprising discovery: Pluto is heating up

24.9.2002
By: Dr. Noah Brosh
Direct link to this page: https://www.hayadan.org.il/pluto240902.html

This is what the face of Pluto looks like in the observations of the Hubble Space Telescope's collection of curiosities that provides the most distant planet
From us, we also joined the discovery that the farther he is now from the sun - the warmer his face gets
Pluto is moving away and is now moving away from the sun, in its regular orbit, where its one lap around the sun lasts about 250 years. But recently it was discovered that its face gradually warms up, precisely as its distance from the sun increases.
This surprising fact joins the collection of oddities exhibited by this planet, the last and most distant from us of the nine that orbit the Sun. Pluto has not yet been explored by spacecraft.
There has recently been an "almost war" between the Senate and the White House over the ambition to conduct an in-depth study of Pluto. While the academic-scientific establishment indicated an operation to launch a spacecraft towards Pluto, as a project that must receive high priority, in the line of science and research operations regarding the solar system - a determination accepted by the Senate - the president and his advisers are determined to cancel the plan, in favor of other operations.
Pluto was only discovered in 1930 and since then it has traveled only a fraction of one cup around the sun. Pluto's orbital motion is carried out in an elongated elliptical orbit. Today, its distance from the sun is about 4.6 billion km. In 116 years it will be at its peak distance from the sun - more than 7 billion km.

Due to the sharp change in the distance to the sun, the amount of heat on its surface decreases over time. That is: a decrease in the temperature of the planet is expected. As a result, its thin atmosphere, which is probably made mostly of nitrogen, is expected to freeze. Only in the year 2200 or so, will Pluto be close enough to the Sun for its atmosphere to thaw.

The existence of the atmosphere was deduced from an observation made in 1985 at the Wise Observatory of Tel Aviv University in Mitzpe Ramon. The findings have since been confirmed several times when Pluto covered a star in the background. The gradual decrease in the intensity of the light coming from it clearly indicated the existence of an atmosphere around the distant planet. But this year two similar events took place, in which Pluto passed over two background stars - as seen from Earth. The scientists expected the decrease in light intensity to be sharper than before (following a similar event observed in 1998). But to their surprise, the first of the two events showed that the decrease in light was more gradual, indicating a more extensive atmosphere and not as narrow as they had previously estimated.

The results of the second event, which occurred and was observed on August 21, have not yet been deciphered. The hypothesis is that Pluto's surface is heating up, for an unknown reason, precisely when it was thought to be cooling down. Observations of similar events, which are expected in the future, will show if indeed the warming process continues, or if the planet's behavior returns to be predictable as previously estimated.