My Science School

You might have heard the idiom "Once in a blue moon" at some point in time. But is there actually a blue moon?

Rare and blue

Blue moon is used to refer to the third full moon in a season which has four full moons. Also called a seasonal blue moon, this occurs once in two-and-a-half years, making it a somewhat rare phenomenon. Today, however, a blue moon is also used to refer to the second full moon that appears in a month, which is also a rare occurrence.

A misunderstanding leads to a new definition

The seasonal definition for the term blue moon dates back to 1937. The August 1937 issue of the Maine Farmers' Almanac explained that moon appears full 12 times in a year, three times each season. However, occasionally there will come a year that has 13 full moons. This means that one of the four seasons will have four full moons, instead of the usual three. The almanac followed certain rules for naming each full moon, such as the last full moon of winter had to fall during Lent and was called the Lenten Moon, while the first full moon of spring was called the Easter Moon and had to fall within the week before Easter.

Thus, when a particular season had four full moons, the third full moon was dubbed a blue moon so that the other full moons could occur at proper times relative to the solstices and equinoxes.

In March 1946, in an article titled "Once in a Blue Moon" which appeared in the Sky and Telescope magazine, the author misinterpreted the Maine Farmers’ Almanac and stated that in a year with 13 full moons, each of the months will have one full moon, while one will have two. However, this definition would mean the blue moon would appear in a different time than the seasonal blue moon since the seasonal blue moon was fixed based on solstices and equinoxes. But this monthly definition became popular after a radio programme in 1980 used this article as a source.

Has the moon ever appeared blue?

While a blue moon appears just like any other full moon, there have been cases where the moon has appeared bluish to the observer. The first major instance when this was observed was after the volcano Krakatoa erupted in 1883. The huge amounts of dust in the air acted as a filter causing sunsets and the moon to turn green and blue all over the world.

Sometimes events such as forest fires and dust storms can also cause the moon to appear bluish.

 

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There are several spacecraft in space. But how do NASA and other space agencies communicate with these spacecraft?

Deep Space Network

Space agencies communicate with spacecraft using the Deep Space Network or DSN. The DSN is a collection of big radio antennas situated in different parts of the world. NASA'S DSN locations are near Canberra, Australia: Madrid, Spain, and Goldstone, California, the US. These sites are almost evenly spaced out meaning even as Earth turns, they never lose contact with the spacecraft.

ISRO, the Indian space agency’s DSN is located at Byalalu, near Bengaluru, Karnataka.

Space agencies use these DSN antennas to send instructions to the spacecraft while the spacecraft send images and other information to these antennas. The antennas also tell us about the location of spacecraft and how they are doing.

Connecting with the DSN antenna

Since spacecraft cannot carry a lot of weight as they need to leave Earth's orbit and stay in space, all spacecraft are fitted with small antennas that can beam weak radio signals back to Earth. The farther away a spacecraft the larger the DSN antenna required to detect its signal and communicate with it. The largest antennas at each of NASA'S DSN sites is 70 mt in diameter.

Post connecting with an antenna

Once a spacecraft communicates with the DSN antenna, centres at each DSN site receive information. In the case of NASA, these sites send the information to the Space Flight Operations Facility at the Jet Propulsion Laboratory in Pasadena, California. Here, photos and other data are processed and shared with scientists and the rest of the world.

 

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The six-year-old Ryugu mission came to an end for Japan's Hayabusa-2 spacecraft when it brought back a capsule of samples from the asteroid on December 6. The capsule landed near Woomera in South Australia. After preliminary inspection, it was flown to the Japan Aerospace Exploration Agency (JAXA) research centre. The extremely high precision required to carry out the mission thrilled many in Japan. The project's manager, Yuichi Tsuda of JAXA, called the capsule a "treasure box." What's the mission Hayabusa-2 all about and what's special about Ryugu?

The unmanned Hayabusa-2 spacecraft was launched on December 3, 2014 to Ryugu, an asteroid more than 300 million km away from Earth. It is a successor to the Hayabusa mission, which returned asteroid samples from Itokawa in June 2010.

Hayabusa-2 arrived at the Ryugu asteroid in June 2018 after which it deployed two rovers and a small lander onto the surface. The asteroid's extremely rocky surface forced the mission's team to revise landing plans, and the spacecraft managed to collect data and soil samples in the more than one-year time it spent by Ryugu. In its first touchdown in February 2019, the spacecraft collected surface dust samples. In June 2019, Hayabusa-2 blasted a crater into the asteroid's surface and then collected underground samples from the asteroid, a first for space history. In late 2019, Hayabusa-2 left Ryugu on its year-long journey to return the samples to Earth which ended on December 6, 2020.

How did the samples reach Earth?

As it approached Earth, approximately at 220,000 km from space, Hayabusa-2 released a capsule and fired its engines to push off in another direction. The 16 kg capsule entered the Earth's atmosphere and landed inside the Woomera Range Complex in the South Australian outback using a parachute. A recovery team collected the pan shaped capsule, about 40 cm in diameter. The capsule contains soil samples taken from two different sites on asteroid Ryugu. Some gases might also be embedded in the samples. The preliminary inspection was done at a lab in Australia. The Hayabusa-2 team wanted the sample in Japan within 100 hours of its entry into Earth in order to keep the space rock pristine. So the capsule was taken on a nine-hour flight to the JAXA.

What is special about Ryugu?

Ryugu is a Near-Earth Asteroid (NEA) with orbits that pass dose by the Earth. It is classified as a potentially hazardous asteroid. Ryugu is an ancient fragment of a larger asteroid that formed in the cloud of gas and dust that spawned our solar system. It is an intriguing type of asteroid that's rich in carbon, an element essential to life. The water composition of some asteroids is believed to be similar to Earth. By studying Ryugu, scientists hope to test this theory.

What can the asteroid samples tell us?

Asteroids orbit the Sun but are much smaller than planets. Scientists believe asteroids are made of the same stuff that went into forming the planets such as Earth They are among the oldest objects in the solar system and therefore may contain dues to how Earth evolved.

Scientists say the samples, especially those taken from under the asteroids surface contain data from 4.6 billion years ago unaffected by space radiation and other environmental factors. They are particularly interested in studying organic materials in the samples to learn about how they are distributed in the solar system and if or how they are related to life on Earth. The samples may help explain the origins of the solar system and how water helped to bring life to Earth. Fragments brought back from Ryugu can also tell its collision and thermal history.

Why is the mission such a big deal for Japan?

The first Hayabusa spaceship's return was considered a miracle, given the troubles it encountered. JAXA'S subsequent Venus and Mars missions also were flawed. According to the Hayabusa-2 team, it used all the hard lessons learnt from the earlier missions to accomplish a 100 times better than "perfect outcome.

What is next for Hayabusa-2?

About an hour after the sample capsule separated from Hayabusa-2, the spacecraft was sent on another mission to the smaller asteroid. 1998KY26. That is an 11-year journey one way. The mission is to study possible ways to prevent big meteorites from colliding with Earth. Between 2021 and 2026, the spacecraft will also conduct observations of exoplanets.

As for the samples, some will be shared with NASA and other international scientists. About 40% of them will be stored for future research.

 

Picture Credit : Google

Scientists send spacecraft to probe objects in space. These spacecraft carry instruments that help them take pictures and collect data in space and send them back to Earth. But to do this, the spacecraft needs electricity So what powers it?

Based on the mission it is assigned, and factors such as where the spacecraft is travelling, what it plans to do there and how long it needs to work engineers choose the best way to power a spacecraft.

The Sun

One source of power engineers consider is energy from the Sun, or solar power. Spacecraft that orbit close to Earth are dose enough to the Sun to use solar power. These spacecraft are fitted with solar panels, which convert the Sun's energy into electricity. The electricity from the panels charges a battery in the spacecraft and can be used even when the spacecraft doesn't have direct sunlight

Batteries

Sometimes, when the mission is only for a short duration, such as the Huygens probe that landed on Titan, Saturn's largest moon, and meant to work only for a few hours, engineers may power the spacecraft with batteries. These batteries are designed to be tough since they need to withstand the harsh environment of space.

Atoms

An atom is a tiny building block of matter. Atoms need to store a lot of energy to hold themselves together. However, atoms such as radioisotopes are unstable and begin to fall apart. As they fall apart, they release energy as heat. A radioisotope power system uses the temperature difference between the heat from the unstable atoms and the cold of space to produce electricity. This system produces power for a very long time even in harsh environments. That's why this system has been used to power many of NASA's missions, including the two Voyager spacecraft that continue to send back information after over four decades in space.

 

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When one object crosses in front of another in space, it is known as transit. For example, when the Moon passes between the Earth and the Sun, the Moon is ‘transiting‘ the Sun.

Why is it important?

Just like objects in our solar system that transit the Sun, there are objects outside our solar system too that transit stars there. These objects include planets known as explants, and their transit help scientists identify these planets.

If the orbit of a planet is lined up right, the planet is lined up right, the planet will transit the star it orbits. When this happens, the light from the star dims by a small amount of time between each transit. This is how scientists discovered seven exoplanets around a star called TRAPPIST-1. There of these planets were discovered in 2015, while four more were identified in 2017.

Bottomline, transits not only help scientists identify new planets but also understand the world beyond our solar system.

The transits we can see

From Earth, there are two main transits that can be seen by people. One is the transit of the Moon, as it passes the Sun. this is when we witness a solar eclipse. The other is the transit of the planet Venus when it passes between the Earth and the Sun during its orbit.

While solar eclipse can be observed often, the transit of Venus cannot be seen frequently because of how he orbits of Venus and Earth are lined up. The last transit of Venus was on June 6, 2012. The next one, however is not until 2117!

 

Picture Credit : Google