Category Exploring the Universe

HOW MANY COMETS HAVE BEEN IDENTIFIED SO FAR?

The current number of known comets is: 3,743. Comets are frozen leftovers from the formation of the solar system composed of dust, rock, and ices. They range from a few miles to tens of miles wide, but as they orbit closer to the Sun, they heat up and spew gases and dust into a glowing head that can be larger than a planet. This material forms a tail that stretches millions of miles.

Comets are cosmic snowballs of frozen gases, rock, and dust that orbit the Sun. When frozen, they are the size of a small town. When a comet’s orbit brings it close to the Sun, it heats up and spews dust and gases into a giant glowing head larger than most planets. The dust and gases form a tail that stretches away from the Sun for millions of miles. There are likely billions of comets orbiting our Sun in the Kuiper Belt and even more distant Oort Cloud.

Credit : NASA science 

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DOES THE TEMPERATURE OF NEPTUNE CHANGE?

Neptune, the farthest planet in the solar system, takes more than 165 years to complete an orbit around the sun. As Neptune has an axial tilt, it experiences seasons, just like our Earth.

Sensing emitted heat : Neptune’s great distance from the sun and the longer period of revolution, however, implies that its seasons change slowly, lasting over 40 Earth years each. A new research published in April in Planetary Science Journal revealed that the temperatures in Neptune’s atmosphere have fluctuated unexpectedly over the last two decades, even though this period only represents half of a Neptune season.

An international team of researchers that included scientists from Leicester and NASA’s Jet Propulsion Laboratory used observations that effectively sensed heat emitted from Neptune’s atmosphere. They combined two decades worth of thermal infrared images of Neptune from the European Southern Observatory’s Very Large Telescope; Gemini South telescope in Chile; Subaru Telescope, Keck Telescope, and the Gemini North Telescope in Hawaii; and spectra from NASA’s Spitzer Space Telescope.

Cooler than we thought :  Analysing this data allowed the researchers to reveal a complete picture of trends in Neptune’s temperatures like never before, and some of these revelations were unexpected, to say the least. Since the beginning of reliable thermal  imaging of Neptune in 2003, the datasets indicate a decline in Neptune’s thermal brightness, which came as a surprise to the researchers. This means that the globally averaged temperature in Neptune’s atmosphere has come down by almost 8 degrees Celsius from 2003 to 2018, making the planet cooler than what we thought  before.

The data from Neptune’s south pole, however, reveals a different dramatic change. Observations of this region show that Neptune’s polar stratosphere has warmed up by nearly 11 degrees Celsius from 2018 to 2020, reversing the previous cooling trend.

As of now, the causes for these stratospheric temperature changes are unknown and follow-up observations of the temperature will be needed to further assess these findings. Some of those causes might be revealed by the James Webb Space Telescope that is set to observe both Uranus and Neptune later this year.

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What is the longest drive record Perseverance Mas rover has set?

NASA’s Perseverance Mars rover set a new record for the longest drive in a single Martian day, travelling 245.76 metres (806 feet) on the surface of Mars on February 4. The previous record was held by NASA’s Opportunity rover in 2005 (214 metres/702 feet). Perseverance broke a second record, surpassing its own longest AutoNav drive. NASA integrated this function into a rover for the first time. When in AutoNav, the rover drives autonomously by navigating through 3D maps and software that help it avoid obstacles. This feature makes Perseverance faster as compared to when it’s being remotely controlled by NASA personnel; it would only traverse about 200 metres a day which would lengthen the timeline of exploration. Perseverance landed on the red planet a year ago and is on a mission to seek out signs of ancient microbial life. It has collected six samples of Martian rock and atmosphere, over 50GB of science data and has sent back over 100,000 images. It has also snapped two selfies on the Martian surface!

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Where are most meteorites found?

Researchers from Delft University of Technology in The Netherlands have used artificial intelligence to create a treasure map of zones in which to find meteorites hidden in Antarctic ice.

Sixty-two per cent of all meteorites recovered on Earth were found in Antarctica, making this cold continent a hotbed for space research. These meteorites provide a unique view into the origin and evolution of the solar system.

Meteorites have been accumulating in Antarctica for millennia, falling from space and becoming embedded in ice sheets within the continent’s interior. As the glaciers slowly flow, the meteorites are carried with them. If a glacier comes up against a large obstacle, in areas like the Transantarctic Mountains, the ice rises and meteorites are brought to the surface. Dry Antarctic winds gradually erode the ice, exposing the meteorites. As more ice rises to the surface, the process repeats. Given enough time, a significant accumulation of meteorites builds up.

Researchers say that satellite observations of temperature, ice flow rate, surface cover and geometry are good predictors of the location of meteorite rich areas, and expect the “treasure map’ to be 80 per cent accurate. Based on the study, scientists calculate that as many as 300,000 meteorites are out there on the Antarctic landscape.

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Why do the footprints of astronauts remain unchanged on the surface of the moon?

We are pretty proud of the human flight to the Moon and our footprints on the lunar surface. But did you know these footprints can last a million years on the surface of the Moon? It has been decades since humans last set foot on the Moon, but its surface is still marked with the historic footprints of the 12 astronauts who walked across it Unlike on Earth, there is no erosion by wind or water on the Moon because it has no atmosphere. The Moon is geologically inactive there are no earthquakes or volcanoes. So, nothing gets washed away and nothing gets eroded.

However, the Moon is exposed to bombardment by meteorites, which change the surface. One little spacerock could easily wipe out a footprint on the moon. And since the Moon has no atmosphere, it is exposed to the solar wind, a stream of charged particles coming from the sun, and over time this acts almost like weather on Earth to scour surfaces on the moon, but the process is very, very slow.

On July 20, 1969, Neil Armstrong put his left foot on the rocky Moon. It was the first human footprint on the Moon. They had taken TV cameras with them. The two astronauts walked on the Moon. They picked up rocks and dirt to bring back to Earth. The astronauts had much work to do. Then, the Eagle went back to meet astronaut Collins. He was in the Command Module working.

When Neil Armstrong and Buzz Aldrin visited the moon 50 years ago, they left roughly 100 objects behind, including a portion of their lunar lander, the American flag and, yes, various kinds of trash. Those objects are still there, surrounded by rugged bootprints marking humanity’s first steps on another world. But that site, called Tranquillity Base, may not be as enduring as the legacy those prints represent.

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What is future of the sun?

Nothing in the Universe is permanent. One of the most profound rules in all the Universe is that nothing lasts forever. With gravitational, electromagnetic and nuclear forces all acting on matter, practically everything we observe to exist today will face changes in the future. Even the stars, the most enormous collections that transform nuclear fuel in the cosmos, will someday all burn out, including our Sun. In about five billion years, the Sun will exhaust the hydrogen fuel in its core and start burning helium, forcing its transition into a red giant star. A red giant is a dying star in the final stages of stellar evolution. When the Sun turns into a red giant, it will expand and engulf the inner planets- possibly even Earth. After spending about one billion years as a red giant, the star will become a white dwarf, packing most of its initial mass into a sphere roughly the size of Earth. It will eventually become a black dwarf.

In about 5 billion years time the Sun will have exhausted all the hydrogen at its core. The core, which by then will consist of helium nuclei, will then shrink and nuclear reactions will take place in a large shell outside the core, rather than the core itself. The outer regions of the Sun will greatly expand and it will become a red giant.

It is unclear exactly how large the Sun will get when it becomes a red giant. Current estimates are that it will expand to 100-250 times its current diameter (ref 2). If we take the lower value, the innermost planet Mercury (but not Venus and the Earth) will be swallowed up by the Sun.  At the higher value, the Earth would also be inside the Sun.

When all of the helium in the core has been converted into carbon, nuclear reactions in the core will once again stop. The Sun will start to convert helium into carbon in a shell outside its core but will become more and more unstable. It will vary widely in brightness as it flares up and ejects some of its outer layers into space and then contracts again. Eventually the whole of the outer regions of the Sun will be blown away forming a glowing shell of plasma called a planetary nebula.

With the lower value, where the Sun expands to 100 times its current radius  value, on Earth the Sun would appear 10,000 times larger than it is today. The surface temperature of the Earth would be around 1500 degrees Celsius, hot enough for it glow a dull red colour. The Earth would have lost its atmosphere long before this and will be a bone dry scorched airless desert on which it will be impossible for life to exist.

Credit : Explaining Science

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