Earth to Voyager 2

In the nearly 44 years since NASA launched Voyager 2, the spacecraft has gone
beyond the frontiers of human exploration by visiting Uranus, Neptune and,
eventually, interstellar space.

In March, the agency was compelled to shut down its only means of reaching 12
billion miles across the heavens to this robotic trailblazer.

On 19 February 2021, Earth’s haunting silence will come to an end as NASA

switches that communications channel back on, restoring humanity’s ability to say
hello to its distant explorer.

Because of the direction in which it is flying out of the solar system, Voyager 2 can
only receive commands from Earth via one antenna in the entire world.

Both Voyager 1 and Voyager 2 hold the records for the farthest a spacecraft has
ever traveled and for the longest operating mission.
 What is an asteroid?

Asteroids are rocky objects that orbit the Sun, much smaller than planets. They are
also called minor planets. According to NASA, there are 994,383 known asteroids,
the remnants from the formation of the solar system over 4.6 billion years ago.

Asteroids are divided into three classes. First, those found in the main asteroid belt
between Mars and Jupiter, which is estimated to contain somewhere between 1.1-1.9
million asteroids.

The second group is that of trojans which are asteroids that share an orbit with a
larger planet. NASA reports the presence of Jupiter, Neptune and Mars trojans. In
2011, they reported an Earth trojan as well.

The third classification is Near-Earth Asteroids (NEA), which have orbits that pass
close by the Earth. Those that cross the Earth’s orbit are called Earth-crossers.
More than 10,000 such asteroids are known, out of which over 1,400 are classified as
potentially hazardous asteroids (PHAs).
 Why do scientists study asteroids?

Scientists study asteroids to look for information about the formation and history
of planets and the sun since asteroids were formed at the same time as other
objects in the solar system.

Another reason for tracking them is to look for asteroids that might be potentially
hazardous.

It is for these reasons that scientists are interested in gathering information about
asteroids.

For instance, scientists are interested in studying Bennu because it hasn’t

undergone drastic changes since its formation over billions of years ago and
therefore it contains chemicals and rocks dating back to the birth of the solar system.
It is also relatively close to the Earth.
 What is 2001 FO32?
On 21 March 2021, the largest asteroid predicted to pass by Earth in 2021 will be at
its closest.

It won’t come closer than 2 million km to Earth, but it will present a valuable
scientific opportunity for astronomers who can get a good look at a rocky relic that
formed at the dawn of our Solar System.

It is called 2001 FO32. There is no threat of a collision with our planet now or for
centuries to come.

Scientists know its orbital path around the Sun very accurately, since it was
discovered 20 years ago and has been tracked ever since.

For comparison, when it is at its closest, the distance of 2 million km is equal to 5¼

times the distance from Earth to the Moon. During this approach, 2001 FO32 will
pass by at about 124,000 kph – faster than the speed at which most asteroids
encounter Earth. Still, that distance is close in astronomical terms, which is why 2001
FO32 has been designated a “potentially hazardous asteroid”.
 Asteroid Apophis

The USA’s NASA space agency has ruled out the possibility of the dreaded asteroid
Apophis causing any damage to the Earth for the next 100 years.

Named after the ancient Egyptian god of chaos and darkness, it was discovered in
2004, after which NASA had said that it was one of the asteroids that posed the
greatest threat to Earth.

Apophis measures 340 metres across– comparable to the size of the huge ship that
has currently blocked the Suez Canal. (That ship, the Ever Given,, is 400m in length,
200m width)

Apophis was predicted to come threateningly close to us in the years 2029 and
2036, but NASA later ruled these events out. There were still fears about a possible
collision in 2068, however.

This year, the asteroid flew past Earth on 5 March 2021, coming within 17 million
km of our planet. They also used the 100-metre Green Bank Telescope in West
Virginia which showed imaging of Apophis.
 NEOWISE to be visible in India

Known as one of the brightest comets to pass near the Earth in over two
decades, comet C/2020 F3 or NEOWISE will be visible in the northern
hemisphere starting on 14 July 2020.

The comet had been discovered by NASA’s Near Earth Wide-field Infrared Survey
Explorer (NEOWISE) earlier this year.

Comet C/2020 F3 is expected to come closest to planet Earth on July 22 and July
23 and can be visible in the north-western sky.

A comet is a cosmic snowball made up of frozen gases, rocks and some dust,
which orbits around in an elliptical manner.

When a comet reaches closer to the sun, its gases start to evaporate in a way that
leaves a tail and a glowing head.

Since they do not have their light on their own, they mostly reflect the sun’s light. In
a dark sky, these comets can be easily viewed.
 What is 16 Psyche

A recent study has found that asteroid 16 Psyche, which orbits between Mars and
Jupiter, could be made entirely of metal and is worth an estimated $10,000
quadrillion — more than the entire economy of Earth.

New images from NASA’s Hubble Space Telescope offer a closer view of the
mysterious asteroid 16 Psyche, whose surface may mostly comprise iron and nickel
(several other rare materials like gold, platinum, cobalt, iridium and rhenium),
similar to the Earth’s core, according to the study published in The Planetary Science
Journal on 2 November 2020.

Metal asteroids are not commonly found in the solar system, and scientists believe
that studying 16 Psyche may offer a rare glimpse of what the inside of a planet
really looks like.

The exact composition and origins of the asteroid will be uncovered in 2022, when
NASA sends (SpaceX Falcon Heavy rocket from Cape Canaveral Air Force Station in
Florida) an unmanned spacecraft to study it up close.
 What is asteroid 16 Psyche?

Located around 370 million kilometres away from Earth, asteroid 16 Psyche is
one of the most massive objects in the asteroid belt in our solar system. The
somewhat potato-shaped asteroid has a diameter of around 140 miles, according to
NASA.

It was first discovered on March 17, 1853, by the Italian astronomer Annibale de
Gasparis and was named after the ancient Greek goddess of the soul, Psyche.

Unlike most asteroids that are made up of rocks or ice, scientists believe that
Psyche is a dense and largely metallic object thought to be the core of an earlier
planet that failed in formation.
 Hayabusa2 mission

Six years after Japan’s Hayabusa2 mission was launched, it returns back to Earth on
6 December 2020 carrying with it samples from the one-kilometre wide Ryugu
asteroid that orbits the Sun.

The mission is similar to NASA’s OSIRIS-REX mission that brought back samples
from asteroid Bennu late in October.

As per NASA, the asteroid is thought to be made up mostly of nickel and iron.
Asteroids like Ryugu are interesting for several reasons, perhaps foremost because they
are near the Earth and might, one day in the far future, pose an impact threat.

Hayabasu2’s predecessor, the Hayabusa mission brought back samples from the
asteroid Itokawa in 2010.

Ryugu is also classified as a PHA and was discovered in 1999 and was given the
name by the Minor Planet Center in 2015. It is 300 million kilometres from Earth
and it took Hayabusa2 over 42 months to reach it.
 NASA’s OSIRIS-REx mission

On 20 October 2020, NASA’s OSIRIS-REx — Origins, Spectral Interpretation,

Resource Identification, Security, Regolith Explorer — spacecraft briefly touched
asteroid Bennu (located over 200 million miles away from Earth), from where it is
meant to collect samples of dust and pebbles and deliver them back to Earth in
2023.

The asteroid was named after an Egyptian deity by a nine-year-old boy from North
Carolina in 2013 who won NASA’s “Name that Asteroid” competition. The asteroid
was discovered by a team from the NASA-funded Lincoln Near-Earth Asteroid
Research team in 1999.

On 20 October 2020, The spacecraft’s robotic arm, also called the Touch-And-Go
Sample Acquisition Mechanism or Tagsam, had made contact with the surface of the
ancient Bennu asteroid. While mission planners expected the total time of contact
to be less than 16 seconds.

In 2016, NASA launched the OSIRIS-REx mission. It reached its target in 2018.
 Geminids meteor shower unique

The Geminids meteor shower, believed to be the strongest of the year, is active
from December 4-December 20, with December 13 and 14 considered to be the best
nights for viewing these meteor showers.

Meteors are bits of rock and ice that are ejected from comets as they manoeuvre
around their orbits around the sun.

When a meteor reaches the Earth, it is called a meteorite and a series of

meteorites, when encountered at once, is termed a meteor shower. According to
NASA, over 30 meteor showers occur annually and are observable from the Earth.

The Geminids meteor showers are unique because their origin does not lie in a
comet, but what is believed to be an asteroid or an extinct comet. The Geminids
emerge from 3200 Phaethon, which meteor scientists consider to be an asteroid.

Discovered on October 11, 1983, the asteroid is over 5 km in diameter and was
named after the Greek myth of Phaethon, the son of Sun god Helios.
Space Internet
 Starlink satellites

Tech billionaire Elon Musk's private aerospace company SpaceX on 14 March 2021
launched 60 Starlink satellites from Launch Complex 39A (LC-39A) at Kennedy
Space Center in Florida.

This was the ninth launch and landing of Falcon 9 first stage booster, which
previously supported launch of Crew Dragon Demo-1, RADARSAT Constellation,
SXM-7, and five Starlink missions.
 OneWeb’s satellites launched

Bharti Global and UK government on 18 December 2020 said their joint

venture OneWeb — a Low Earth Orbit (LEO) satellite communications
operator — launched 36 satellites from the Vostochny cosmodrome in
Russia.

This takes the total in-orbit constellation to 110 satellites, part of

OneWeb’s 648 LEO satellite fleet that will deliver high-speed, low-latency
global connectivity.
 SpaceX selected for SPHEREx mission

NASA has selected tech billionaire Elon Musk's private aerospace company
SpaceX to provide launch services for an astrophysics mission to survey the sky in
the near-infrared light.

The planned two-year mission is called SPHEREx, short for Spectro-Photometer for
the History of the Universe, Epoch of Reionization, and Ices Explorer.

The near-infrared light, which, though not visible to the human eye, serves as a
powerful tool for answering cosmic questions involving the birth of the universe,
and the subsequent development of galaxies.

SPHEREx will also search for water and organic molecules -- essentials for life as
we know it -- in regions where stars are born from gas and dust, known as stellar
nurseries, as well as disks around stars where new planets could be forming.
Space Tourism
 What is space tourism?

Space tourism is a segment of space travel that seeks to give lay people the
opportunity to go to space for recreational, leisure or business purposes. The idea
is to make space more accessible to those individuals who are not astronauts and
want to go to space for non-scientific purposes.

A report published by the Congressional Research Service (CRS) notes that the
concept of space tourism is “fairly new”. The report mentions that in 1997, the
private company Space Adventures was founded to offer “bookable space-related
adventures”.

In fact, Space Adventures is the only private company to send paying customers
to orbital space so far, the report says.

In 2004, test pilot Mike Melville became the first private astronaut to fly beyond
the Karman Line (recognised as the edge of space).
In 2008, the billionaire video game developer, Richard Garriott became the sixth
private citizen to fly to space. As per media reports, Garriott paid over $30 million
to spend about 12 days at the ISS, which he traveled to aboard a Russian Soyuz
spacecraft.

Before Garriott, Space Adventures’ customer Dennis Tito became the first space
tourist in 2001.

As of now, companies including Virgin Atlantic, SpaceX, XCOR Aerospace, Jeff

Bezos’s Blue Origin and Armadillo Aerospace are working on providing space
tourism services to people.

As of now, potential customers can pay a $1000 fully refundable registration fee
to Virgin Galactic, after which they will be notified as and when tickets go on sale.
 Shephard test successful

Jeff Bezos' Blue Origin space company launched a New Shepard rocket for a
seventh time from a remote corner of Texas on 13 October 2020, testing
new lunar-landing technology for NASA that could help put astronauts back on
the moon by 2024.

In 2018, Blue Origin was one of the ten companies selected by NASA to conduct
studies and advance technologies to collect, process and use space-based
resources for missions to the Moon and Mars.

New Shephard has been named after astronaut Alan Shephard, the first
American to go to space, and offers flights to space over 100 km above the Earth
and accommodation for payloads.

Essentially, it is a rocket system that has been designed to take astronauts and
research payloads past the Karman line – the internationally recognised boundary of
space.
 Starship prototype explodes

SpaceX’s Starship prototype exploded while attempting to land on 9 December 2020

after an otherwise successful test launch from the company’s rocket facility in Boca
Chica, Texas.

Designed by SpaceX, Starship is a spacecraft and super-heavy booster rocket

meant to act as a reusable transportation system for crew and cargo to the Earth’s
orbit, Moon and Mars.

SpaceX has described Starship as “the world’s most powerful launch vehicle” with
an ability to carry over 100 metric tonnes to the Earth’s orbit.

Starship has been under development since 2012 and is a part of Space X’s central
mission to make interplanetary travel accessible and affordable and to become the
first private company to do so.
 What is Starship?

Designed by SpaceX, Starship is a spacecraft and super-heavy booster rocket

meant to act as a reusable transportation system for crew and cargo to the Earth’s
orbit, Moon and Mars.

SpaceX has described Starship as “the world’s most powerful launch vehicle” with
an ability to carry over 100 metric tonnes to the Earth’s orbit.

What is the idea behind developing this spacecraft?

Starship has been under development since 2012 and is a part of Space X’s
central mission to make interplanetary travel accessible and affordable and to
become the first private company to do so.

Therefore, the company is working on building a fleet of reusable launch vehicles,

capable of carrying humans to Mars and other destinations in the solar system.
 SpaceShipTwo’s first crewed test flight

On 12 December 2020, Virgin Galactic launched a test flight of SpaceShipTwo, its

reusable winged spacecraft which will take off from New Mexico’s Spaceport
America for the first time and is expected to reach an altitude of 80 km.

Virgin Galactic is a publicly traded company founded by British entrepreneur

Richard Branson and is one of the companies that is working on offering flights to
space to paying customers.
Crew Mission
 SpaceX-NASA Crew-1 mission

As part of NASA’s first commercial human spacecraft system in history, a crew of

four astronauts is now en route to the International Space Station (ISS) on a 27-hour
flight, onboard SpaceX’s Crew Dragon spacecraft called Resilience.

The mission was to launch on 14 November 2021 initially, but was impeded by
unfavourable weather conditions.

Crew-1 is the first operational flight of the SpaceX Crew Dragon spacecraft on a
Falcon 9 rocket to the ISS and is also the first of the three such flights scheduled over
the course of 2020-21.

It is the first of six crewed missions that NASA and SpaceX will operate as part of
the Commercial Crew Program, whose objective is to make access to space easier in
terms of its cost, so that cargo and crew can be easily transported to and from the
ISS, enabling greater scientific research.

Boeing and SpaceX were selected by NASA in September 2014 to develop

transportation systems meant to transfer crew from the US to the ISS.
While the Crew Dragon spacecraft is capable of staying in orbit for a period of 210
days, it will return in spring 2021, making it the longest human space mission
launched from the US.

At the ISS, the Crew-1 team will join members of Expedition 64 and conduct
microgravity studies.

Some of the research that the crew is carrying with themselves includes materials to
investigate food physiology, which will study the effects of dietary improvements
on immune function and the gut microbiome and how those improvements can help
crews adapt to spaceflight.

Another experiment aboard the Crew Dragon is a student-designed experiment

titled, “Genes in Space-7” that aims to understand how spaceflight affects brain
function.

Other experiments include research that will enable scientists to understand the
physical interactions on liquid, rocks and microorganisms, another experiment on
the role of microgravity on human health and how microgravity affects heart
tissue.
NASA used to have a fleet of five spaceships under its Space Shuttle programme,
that were used to make a total of 135 of journeys into space, and the International
Space Station (ISS), in the 30 years between 1981 and 2011.

Two of these were destroyed in accidents, the Challenger in 1986 and Columbia in
2003, each resulting in the death of seven astronauts.

After the 2003 accident, in which India-born astronaut Kalpana Chawla was among
those killed, the US government had decided to close the Space Shuttle programme.

The three remaining spaceships, Discovery, Atlantis, and Endeavour, were formally
retired in July 2011, even though they were fit for many more flights.
 The significance of the Crew-2 mission
Four astronauts were launched to the International Space Station (ISS) from Florida
as part of collaboration between NASA and SpaceX under the Commercial Crew
Program (23 April 2021). Now, Crew-2 astronauts will join the members of
Expedition 65

The mission is called Crew-2 and is the second crew rotation of the SpaceX Crew
Dragon and the first with international partners.

Out of the four astronauts, two are from NASA and two are from the Japan
Aerospace Exploration Agency (JAXA) and the European Space Agency (ESA).

The main objective of this program is to make access to space easier in terms of
its cost, so that cargo and crew can be easily transported to and from the ISS,
enabling greater scientific research.

Some of the research that the crew carried with them included materials to
investigate food physiology meant to study the effects of dietary improvements on
immune function and the gut microbiome and how those improvements can help
crews adapt to spaceflight.
 Sentinel-6 satellite

The Copernicus Sentinel-6 Michael Freilich satellite, designed to monitor oceans,

was launched from the Vandenberg Air Force base in California aboard a SpaceX
Falcon 9 rocket on 21 November 2020.

This is a part of the next mission dedicated to measuring changes in the global sea
level.

Other satellites that have been launched since 1992 to track changes in the oceans
on a global scale include the TOPEX/Poseidon, Jason-1 and OSTN/Jason-2, among
others.

The Sentinel-6 Michael Freilich satellite has been named after Dr. Michael Freilich,
who was the Director of NASA’s Earth Science Division from 2006-2019 and passed
away in August this year.
The mission, called the Jason Continuity of Service (Jason-CS) mission, is designed
to measure the height of the ocean, which is a key component in understanding
how the Earth’s climate is changing.

The spacecraft consists of two satellites, one of them launched on 21 November

2020, and the other, called Sentinel-6B, to be launched in 2025.

It has been developed jointly by the European Space Agency (ESA), NASA,
European Organisation for the Exploitation of Meteorological Satellites
(Eumetsat), the USA’s National Oceanic and Atmospheric Administration (NOAA)
and the EU, with contributions from France’s National Centre for Space Studies
(CNES).

Since 1992, high-precision satellite altimeters have helped scientists understand

how the ocean stores and distributes heat, water and carbon in the climate
system.
 US spacecraft named after Kalpana Chawla

An American commercial cargo spacecraft bound for the International Space

Station has been named after fallen NASA astronaut Kalpana Chawla (S S Kalpana
Chawla capsule), the first India-born woman to enter space, for her key contributions
to human spaceflight.

Northrop Grumman, an American global aerospace and defence technology company,

announced that its next Cygnus capsule will be named the “S.S. Kalpana Chawla”, in
memory of the mission specialist who died with her six crewmates aboard the
space shuttle Columbia in 2003.

Chawla was selected in honour of her prominent place in history as the first
woman of Indian descent to go to space.

The S S Kalpana Chawla capsule is scheduled to launch on the NG-14 mission atop a
Northrop Grumman Antares rocket from the Mid-Atlantic Regional Spaceport
(MARS) at NASA’s Wallops Flight Facility in Virginia on 29 September 2020.
 Aditya - L1 First Indian mission to study the Sun

The Aditya-1 mission was conceived as a 400kg class satellite carrying

one payload, the Visible Emission Line Coronagraph (VELC) and was
planned to launch in a 800 km low earth orbit.

A Satellite placed in the halo orbit around the Lagrangian point 1 (L1) of
the Sun-Earth system has the major advantage of continuously viewing
the Sun without any occultation/ eclipses.

Therefore, the Aditya-1 mission has now been revised to “Aditya-L1

mission” and will be inserted in a halo orbit around the L1, which is 1.5
million km from the Earth.

The satellite carries additional six payloads with enhanced science scope
and objectives.
 Algorithm for Aditya L1 developed

A group of researchers, led by the Aryabhatta Research Institute of Observational

Sciences (ARIES), has developed a novel algorithm to track the very fast accelerating
Coronal Mass Ejections (CMEs) emerging from the interiors of the Sun.

Due to limited technology — both in terms of satellite and ground-based observatories

along with computational capabilities, acquiring observations of CMEs originating from
within the Sun’s interiors have been a hurdle for the scientific community.

Space environment around Earth is governed by the Sun. Weather and climate on
Earth are influenced by even a minor variation in this environment.

CMEs, along with solar flares, solar energetic particles, high-speed solar winds,
together pose serious threat to most of Earth’s space-based services including Global
Positioning System (GPS), radio and satellite-based telecommunication and can lead
to power grid failure.
This algorithm, named CME Identification in Inner Solar Corona
(CIISCO), could even set a foundation in planning research of the lesser-
known lower corona region of the Sun using Aditya L1, India’s maiden
mission to the Sun.

This Indian Space Research Organisation (ISRO)-led mission is scheduled

for a launch in 2022.
 What is Square Kilometre Array

On 4 February 2021, the Square Kilometre Array Observatory (SKAO) Council held
its maiden meeting and approved the establishment of the world’s largest radio
telescope.

SKAO is a new intergovernmental organisation dedicated to radio astronomy and

is headquartered in the UK. At the moment, organisations from ten countries are a
part of the SKAO.

These include Australia, Canada, China, India, Italy, New Zealand, South Africa,
Sweden, the Netherlands and the UK.

Unlike optical telescopes, radio telescopes can detect invisible gas and, therefore,
they can reveal areas of space that may be obscured by cosmic dust.

Significantly, since the first radio signals were detected by physicist Karl Jansky
in the 1930s, astronomers have used radio telescopes to detect radio waves
emitted by different objects in the universe and explore it.
 So what is significant about the SKA telescope?

The telescope, proposed to be the largest radio telescope in the world, will
be located in Africa and Australia whose operation, maintenance and
construction will be overseen by SKAO.

The completion is expected to take nearly a decade at a cost of over £1.8

billion.
 HST captures Einstein Ring

The National Aeronautics and Space Administration (NASA) and European Space
Agency (ESA) operated Hubble Space Telescope (HST) has captured the GAL-CLUS-
022058s in a stunning image. The narrow galaxy is curved around a spherical
companion, depicting a highly rare phenomenon.

The GAL-CLUS-022058s is located in Fornax or the Furnace’s southern

hemisphere constellation.

The space agency has called this one of the most complete as well as the largest
Einstein Ring that has ever been discovered by us in the vast universe.

Astronomers who have been observing this particular Einstein Ring have started
calling it the “Molten Ring”, alluding to both its appearance as well as the host
constellation.

The phenomenon was first theorised by great scientist Albert Einstein in his
general theory of relativity.
The object has an unusual shape due to the gravitational lensing, a process that
causes light coming from a faraway place to bend due to an object’s gravity
between the source of the light and the observer.

In this particular case, the agency said, the light was originating from the galaxy in
the background and it was distorted and made into a curve due to the
gravitational pull of the galaxy cluster in front of it.
In Einstein’s theory of relativity, Einstein postulated that space and time,
together known as space time, were in fact warped by massive objects.

The more massive the object, the larger the impact in has on space time. The
curves created by objects form a sense of gravity and replace the gravitational
force that classical physics preached.

In contrast to a force pulling all objects with mass together, objects are instead
caught following the straight path in warped area, known as the geodetic effect, of a
massive object.

By bending space-time, massive objects can also “bend” electromagnetic waves

that travel on these curved surfaces. By creating his theory of general relativity,
Einstein set the stage for black holes to make a reemergence in the world of
physics.

While Einstein’s general relativity allowed black holes to exist, Einstein was not
responsible for the modern idea of black holes; Karl Schwarzschild was.
 A missing supermassive black hole

A supermassive black hole, which is estimated to weigh up to 100 billion

times the mass of the Sun, is seemingly missing, leaving astronomers
perplexed.

Scientists have been looking for the black hole using NASA’s Chandra X-
ray Observatory and Hubble Space Telescope, and have so far found no
evidence that it is anywhere to be found.

Not unexpectedly, many social media users have expressed confusion about
the black hole’s whereabouts, which is supposed to be at the centre of a
far-off galaxy.
 The ‘missing’ black hole

The black hole is supposed to be located in Abell 2261, an enormous

galaxy cluster that is about 2.7 billion light-years away from our planet.

One light-year is the distance that a beam of light travels in one Earth
year, which is 9 trillion km.

On the scale of the Universe, astronomers measure the distance from stars
and galaxies in the time it takes for light to reach us.

So, when we look at a celestial object, we are looking at how it appeared

that long ago in the past.

At 2.7 billion light-years away, the Abell galaxy is at an overwhelmingly

large distance away from us.
 So, what could have happened?

Every large galaxy in the universe has a supermassive black hole at its centre,
whose mass is millions or billions of times that of the Sun, according to NASA.

The black hole at the centre of our galaxy– the Milky Way– is called Sagittarius A*,
and is 26,000 light-years away from Earth.

‘Recoiling’ black holes

When two black holes merge, they release what are known as gravitational waves–
invisible ripples travelling at the speed of light, which squeeze and stretch
anything in their path.

As per the theory of gravitational waves, during such a merger, when the amount of
waves generated in one direction is stronger than another, the new big black
hole can be sent away from the centre of the galaxy into the opposite direction.
This is known as a “recoiling” black hole.
Einstein predicted that something special happens when two bodies—such as
planets or stars—orbit each other.

He believed that this kind of movement could cause ripples in space. These ripples
would spread out like the ripples in a pond when a stone is tossed in. Scientists
call these ripples of space gravitational waves.

Gravitational waves are invisible. However, they are incredibly fast. They travel at
the speed of light (186,000 miles per second). Gravitational waves squeeze and
stretch anything in their path as they pass by.

What causes gravitational waves?

The most powerful gravitational waves are created when objects move at very
high speeds. Some examples of events that could cause a gravitational wave are:

1. when a star explodes asymmetrically (called a supernova)

2. when two big stars orbit each other
3. when two black holes orbit each other and merge
 India’s LIGO gravitational-wave observatory gets green light

The observatory is scheduled for completion in 2024, will be built in the Hingoli
District of Maharashtra state in western India.

An Indian team of scientists has been collaborating formally on the Laser Interferometer
Gravitational-Wave Observatory (LIGO) project with US scientists since 2016.

In 2015, LIGO’s US detectors made the first discovery of gravitational waves —

energy produced and radiated by the collision of two black holes — thereby confirming
Albert Einstein’s prediction and launching a new way of studying the Universe.

The Indian gravitational-wave detector would be only the sixth such observatory in
the world and will be similar to the two US detectors in Hanford, Washington, and
Livingston, Louisiana.

India’s Department of Atomic Energy and its Department of Science and

Technology signed a memorandum of understanding with the US National Science
Foundation for the LIGO project in March 2016.
 LISA Pathfinder Mission

LISA Pathfinder has been introduced to mitigate the risks of the LISA
mission. The main goal of the LISA Pathfinder mission is to
demonstrate the concept of the gravitational wave detection using a
single spacecraft: it will put two test masses in a near-perfect
gravitational free-fall and control and measure their motion with
unprecedented accuracy.

This is achieved through state-of-the-art technology comprising

the inertial sensor system, the laser metrology system, the drag-free
control system and an ultra-precise micro-propulsion system.
 Evolved Laser Interferometer Space Antenna (eLISA)

eLISA is a spectacular plan of setting into space three spacecraft, a mother and
two daughter spacecraft, which will fly in a triangular formation, trailing the earth
in its orbit around the sun at a distance of over 50 million km.

Each arm of the imaginary triangle, from the mother to each daughter spacecraft, will
measure about a million km.

Inside these spacecraft will float “freely falling” test masses – cubes with sides
measuring abut 46 mm.

Laser interferometers will accurately measure changes in the distance between

these cubes. If they should be affected by a gravitational wave, the minute changes in
this distance are measure by the interferometer.

eLISA aims to measure gravitational waves in the frequency range from 0.1mHz to
about 100 mHz. To do this, it is necessary for the interferometers to have an arm
length of a million kilometres and that is impossible to achieve with an earth
based setup.